In the section below, you can find the most frequently asked questions (and answers) we received.

These are categorized in Operation, Reliability, Compliance, and Others.

You can select the FAQs by category or use the search function at the top of the website to directly search for information.
If you cannot find the information you are looking for, use the “DON’T FIND ANSWERS? CONTACT US” button on the top right side of our website.

Depending on the installation environment, you may need IP certified power supplies (IP65/IP67). 

Also, waterproof connectors and junction boxes are useful accessories to ensure a reliable operation in damp environments (please refer to the LED power supply installation manual).

Waterproof connector solution

Junction box option

Note that the MEAN WELL product IP level, including IP67, is tested according to IEC 60529. The protection does not guarantee for permanently immersing in the water. Please check the device installation manual for proper suggestions on installation. 

Categories: LED Lighting, Operation
Tags: IEC60529, IP65, IP67

Capacitive loads can be found under many different forms: capacitor banks, batteries, and even power supplies themselves are considered as capacitive loads. The principal issue that can appear on such type of load is at PSU start-up: a discharged capacitor basically acts like a short-circuit at start-up, hence it may overload the output.

One solution is either to add current limiting resistors in series with the capacitive load to limit the output current, or to select a power supply with “constant current limiting” overload protection type. This way, the power supply will automatically limit the current to a certain level stated in the specifications:

SPV-150 series specifications

For inductive loads, motors need high current at start-up, therefore a power supply with peak power capability is recommended (or a PSU with constant current limiting overload protection type).

The main issue of dynamic loads is output voltage drop. If the load step is too high in amplitude and too long, it may be able to completely discharge the output capacitors and then create a voltage drop or high ripple at the output. If the frequency of the load changes is high enough, this kind of issue is less likely to happen (please refer to the test reports for more information). One solution could be to put additional capacitors between Power Supply and load.

Some applications may need to draw short peak currents from the power supply. If the PSU overload protection type is hiccup or constant current limiting mode, then it will not be able to provide the current peak needed by the load. Some of our power supplies come with a peak power capability that makes them suitable for these kinds of applications. (e.g. HRP-150N series)

For open-frame power supplies with peak capability, the user should refer to the derating curves, and check the thermal requirements (a fan may be required).

Categories: Industrial, Medical, Operation

A TTL signal, Transistor-Transistor-Logic, is a binary signal generated with the help of a transistor turning on or off. 0-0.4V is considered as low state, and 2.7-5V is a high state.

The difference between the TTL and Relay Contact topologies is that since in Mean Well products the TTL signal is created through a transistor or semiconductor, the current capability of the signal is relatively low. In contrary, using Relay Contact method (which uses a metal contact as conductor) allows much higher current to flow.

Categories: Industrial, Operation

Generally, at no load or light load, the power factor is relatively low. In such conditions, although the active power is low, the reactive power and input current is quite high, which results in high measured current using a multimeter. In order to accurately measure the active power, the RMS input current, RMS input voltage, as well as the distrotion and phase shift between V and I curves should be measured (with a powermeter, or an oscilloscope).

If only measuring V and I RMS values, the result is the apparent power, which comprises real and reactive power.
Some models may require to use the Remote Off function to achieve low no load power consumption.

Categories: Industrial, Medical, Operation

MEAN WELL developed many power supplies series specifically for LED application. Single stage PFC was used in such developments due to low cost. This topology has the following restrictions:

AC fluctuation

  • This topology does not use input bulk capacitor. For this reason, in areas with low AC quality, output voltage and current may become unstable causing variation in LED brightness. If the input AC voltage is stable, then this problem will not occur.
  • Output ripple

This is also caused by lack of input bulk capacitor. As compared to power supplies using two-stage PFC, the ripple will be significantly larger (see Figure 4). There could be instances where the low end of the ripple may be too low for the driver IC to operate properly, and the LEDs will start to flicker. To solve this type of problem, the output voltage can be adjusted higher, so the low end is higher than the driver’s minimum working voltage. Or simply select a PSU with higher rated voltage.

  • Current harmonics

Single stage PFC power supplies are optimized for constant current drive. Using these supplies as constant voltage sources (such as application including cascading a constant current driver IC), the harmonics might be worsening in this case. When operating in areas with unstable utility voltage or with driver IC, we highly recommend using general application types as found in table 1. Avoid using single stage PFC if possible and use a two-stage PFC power supply instead, or contact MEANWELL for more information.

Categories: LED Lighting, Operation

MEAN WELL LED power supply does not have a parallel “current sharing” function, so it is not suitable for parallel connection. For high power requirements, please select higher wattage power supply or divide LED load into smaller subsections to be powered by individual power supplies. Example of such LED configuration can be found in figure 5. As shown in fig. 5, the connection between -V of the LPC-35 units should be severed and not connected in common. On the contrary, small wattage LED loads can be connected in parallel and be powered by a single high wattage power supply. But the ability to divide current evenly must be taken into consideration.

Categories: LED Lighting, Operation

When power supplies are connected in parallel, mostly, is intended to increase the output current. Due to the design of active current sharing, they are mostly without reverse current protection, therefore, they are not the best solution when talking about redundancy. For redundant purposes, please choose the PSU with redundant function or implement external redundant modules. Be sure that the difference in output voltage and wiring impedance, should be as small as possible.

1. Use PSP models as an example, connect P(LP/CS) terminals together (Please refer to the parallel function in the specification). Input and output should be connected in parallel before connecting to the AC source and loads. Shown as in the picture below (some specific power supplies require a minimum load after paralleling).

2. Output voltage difference between power supply units should be as small as possible, normally < 0.2V.

3. The power supplies should be paralleled with short and large diameter wiring together first, and then connected to the load.

4. After paralleling, the maximum usage of total power should be around 90% of the rated total power.

5. When the power supplies are paralleled, if the load is lower than 10% of the rated load of the individual power supply, the LED indicator or signals (Power Good, Pok, Alarm Signal) may malfunction.

6. To ensure that the load current is effectively shared in parallel operation, in general, it is recommended not to use more than 4-6 power supplies at one time. Please follow the maximum number of units as stated in the datasheet.

7. In some models, the +S, -S terminals should be used to reduce unstable pulsation of output voltage.

Categories: Industrial, Operation

COM (COMMON) means common ground. Please see below:

Single output: Positive pole (+V), Negative pole (-V)Multiple outputs (Common ground): Positive pole (+V1, +V2,.), Negative pole (COM)

Categories: Industrial, Operation
Tag: COM

Yes, for power supplies certified >2000m please read the “note” in the spec.

In general, for unpotted models, a derating of 5°C/1000m has to be applied and for potted models, a derating of  3.5°C/1000m has to be applied.

For example LRS-75-24:

The datasheet shows:

The Note. 7 shows:

At 5000m the derating curve will need to move 15°C following the arrow (1)

At full load the maximum operating temperature at 5000m will be 35°C shown at (2)

There are some minimum-load requirements on MEAN WELL’s multi-output power supplies. Please read the specification first before connecting to the load. To allow the power supply to work properly, a minimum load for each output is required, or else, the output voltage level will be unstable or outer tolerance range. Please refer to “Current range” in the specification as shown in the table below: Channel 1 requires a 2A minimum-load; channel 2 requires 0.5A; Channel 3 requires 0.1A ; Channel 4 does not need any minimum-load.

Categories: Industrial, Medical, Operation

In general, there are two circumstances that will cause the power supply to shut down. The first one is the activation of the overload protection (OLP). To deal with this situation, we suggest increasing the rating of the output power or modifying the OLP point. The second one is the activation of over temperature protection (OTP) when the internal temperature reaches the pre-set value. All these conditions will let the Power Supply enter protection mode and shut down. After these conditions are removed, the Power Supply will be back to normal.

Categories: Industrial, Medical, Operation

Cooling fans have a relatively shorter lifetime (typical MTTF, Mean Time To Failure, of around 5,000-100,000 hours) compared with other components of power supply. As a result, changing operating method of the fans can extend the operation hours. The most common control schemes are shown as below:nnTemperature control: if the internal temperature of a power supply, detected by a temperature sensor, is over the threshold, the fan will start working at full speed, whereas, if the internal temperature is less than the set threshold, the fan will stop working or run at half speed. In addition, cooling fans in some power supplies are controlled by a non-linear control method whereby fan speed can be changed with different internal temperatures synchronously.nLoad control: if the loading of a power supply is over the threshold, the fan will start working at full speed, whereas, if the loading is less than the set threshold, the fan will stop working or run at half speed.

At input side, there will be (1/2 ~1 cycle, ex. 1/120 ~ 1/60 seconds for 60 Hz AC source) large pulse current (Ipk 20~100A based on the design of power supply) at the moment of power-on and then back to normal rating. This “Inrush Current” will appear every time you turn on the power. Although it will not damage the power supply, we suggest not turning the power supply ON/OFF very quickly within a short time. 

A more critical situation can occur if there are several power supplies turning on at the same time, the dispatching system of AC source may shut off and go into protection mode because of the huge inrush current. It is suggested that these power supplies start up one by one or use the remote control function of power supply to turn them on/off.

Categories: Industrial, Medical, Operation

COM (COMMON) means common ground. Please see below:nSingle output: Positive pole (+V), Negative pole (-V)nMultiple output (Common ground): Positive pole (+V1, +V2,.), Negative pole (COM)

Categories: Industrial, Operation

Due to different circuit designs, the MEAN WELL power supply’s input consists of three types as below:


a.  85~264VAC;120~370VDC

b.  176~264VAC;250~370VDC

c.  85~132VAC/176~264VAC by Switch; 250~370VDC

  • In a and b inputs models, power supply can work properly no matter under AC or DC input. Some models need correct connection of input poles, positive pole connects to AC/L; negative pole connects to AC/N. Others may require opposite connection, positive pole to AC/N; negative pole to AC/L. If customers make a wrong connection, the power supply will not be broken. You can just reverse the input poles and power supply will still work.
  • In c input models, please make sure that you switch the 115/230V input correctly. If the switch is on the 115V side and the real input is 230V, the power supply will be damaged. 
Categories: Industrial, Medical, Operation

Some power supplies provide a “Power Good” signal when they are turned on and send out a ” Power Fail” signal when they are turned off. This is usually used for monitoring and controlling purposes.

  • Power Good: after the output of a power supply reaches 90% rated voltage, a TTL signal (about 5V) will be sent out within the next 10-500ms.
  • Power Fail: before the output of a power supply is less than 90% rated voltage, the power-good signal will be turned off at least 1ms in advance.
Categories: Industrial, Medical, Operation

When current drawn exceeds the rating of the PSU, the protection circuit will be triggered to protect the unit against overload/overcurrent. 

Protections of overload/overcurrent can be divided into several forms:


Output current decreases about 20% of rated current, shown as curve (a) in the figure below. 


Output current remains at a constant level and within the specified range while the output voltage drops to a lower level, shown as curve (b) in the figure below. 


Output power remains constant. As output load increases, output voltage decreases in proportion, shown as curve (c) in the figure below.  


Output voltage and current keep pulsing ON and OFF repeatedly when protection is activated. The unit automatically recovers when faulty condition is removed.


 Output voltage and current are cut off when output load reaches protection range. 

NOTE: Protection mode of some of the products combines with different types of the forms mentioned, such as constant current limiting + shut down.

Recover method:

(1)Auto Recovery: PSU recovers automatically after faulty condition is removed.

(2)Re-power on: PSU restarts by manual AC re-power on after faulty condition is removed.

Note: Please do not operate PSU in overcurrent or short-circuit condition for a long period of time to prevent a shorten lifespan or damaging the PSU.

Categories: Industrial, Medical, Operation

LED power supply comparison table to see which MW LED power supply allows for V/I adjustments. A suitable unit can be picked based on the type of adjustment required. For the allowed adjustment range, please refer to the spec sheet. Tuning of the voltage and current levels can be done through the built-in VRs/potentiometers. PLN/ELN requires removal of the top cover in order to access the internal SVR1 and SVR2, see figure 9 for VR locations. For other series, the VRs can be accessed through IoADJ and VoADJ holes after rubber stopper removal. After adjustments have been made, please make sure rate power is not exceeded and the rubber stoppers are properly reassembled.

Categories: LED Lighting, Operation

With 1~10V dimming, the lighting unit can be dimmed down to 10%; with 0~10V dimming, it can be dim down to 0%, or say, dim-to-off.

Categories: LED Lighting, Operation

To install a power supply into the system, you would need wires for the connection both to the loads and to the energy source. There are a couple of points that should be taken into consideration when choosing wires, one is the current rating, it may cause high heat on the wires or burnt out in the worst case if the rating is not enough. The other is voltage drop, there would be voltage reduction at load side as current moves through the wires owing to the internal resistance. If too many voltage drop in a line, there could be no sufficient voltage to drive the loads. You can find the right wires for use by referring to the table below on the basis of your system design.

Categories: Industrial, Medical, Operation

First, use twisted wires, connect +S to the positive end of the output, then -S to the negative end of the output, as shown in the illustration. Also, keep the wires off the AC and output cables to prevent noise interference.

Add capacitors at the output end where the Remote Sensing wires are connected to if the dynamic load (frequency above 1K Hz) is used. The purpose is to reduce noise as Remote Sensing is a sensitive function. A suitable capacitor requires two factors:

a. Rated Ripple Current is 0.2 times greater than the output current

b. Rated Voltage is higher than the output voltage

Categories: Industrial, Operation

If you connect the power supply to motors, light bulbs, or high capacitive loads, you will have a high output surge current when you turn on the power supply and this high surge current will cause failure of startup. We suggest using power supply with constant current limiting protection to deal with these loads.

Categories: Industrial, Medical, Operation

Yes. Since our products are designed based on isolation concept, it will be no problem that the output ground (GND) and frame ground (FG) is the same point in your system. But EMI may be affected by this connection.

Categories: Industrial, Medical, Operation

Yes this is normal. Leakage current is the current flowing from the protective earth (PE) conductor, such as metal enclosure, of equipments to frame ground (FG). Due to EMI requirement for the power supply, there are Y capacitors connected in between AC L/N and PE conductor. A low current will flow through the Y-caps to FG. In reality, leakage current should be regulated to comply with safety standards. In regulations of safety for IT products, leakage current should be less than 3.5mA for portable Class I equipment, 0.75mA for hand-held Class I equipment, and 0.25mA for Class IInequipment.

Because of the low current flowing, this is not harmful for the human body. For medical power supplies there are however more strict regulations regarding leakage current.

For more information, please see our Medical Application page

Categories: Industrial, Medical, Operation

Depending on the circuit design, there could be different operational problems. See below:

  • Boost mode driver IC:

The startup voltage of such driver IC is significantly lower than the total LED forward voltage. For this reason, the IC will start up at very low voltage level usually about 1/2 of the power supply’s rated voltage and to meet rated power requirement, the startup current will reach 2 times the power supply’s rated current. When the power supply is unable to provide this current, the LED CC driver will not activate.

  • Buck mode driver IC:

If the selected power supply voltage is significantly higher than the LED forward voltage. For example, power supply provides 48V and the LED lamp only needs 24V and the power ratings are equivalent. When power supply voltage reached the LED conduction voltage, the power supply will immediately go into constant current mode. At this moment, the required power to start up the LED + driver is larger than what the power supply can provide causing malfunction of the driver circuit and the power supply to be clamped at LED forward voltage. For boost mode design, we recommend raising the startup voltage of the driver IC to be as close to the power supply voltage as possible or incorporate soft start function (see fig. 3). Wait until the power supply voltage is established before starting the driver. When selecting power supply for buck mode, the output voltage of the power supply should be as close to the LED total voltage as possible with excess power available (LED power/0.85).

DIM PIN is the startup pin for most PWM based driver. It can also be designated as EN (Enable). DIM (or Enable) is at 0V the internal connection to SW pin will be open. When the DIM voltage reaches 1.5V (Typ), the IC will Turn ON. To set the Vstart for the DRIVER IC: Vstart = (VDIM/RB) x (RA+RB). The general rule is to set the Vstart at 5~10% higher than the total LED forward voltage.

Categories: LED Lighting, Operation

LDD/LDH series comprises switching components; series or parallel connection will damage these switching components.

Categories: LED Lighting, Operation
Tags: Parallel, Series

First of all. Determine the driving method of LED lamp. If the lamp is driven by constant current, forward current shall be within specification. On the contract, if it’s driven by constant voltage, then user must check if they are using the right product to dim the LED lamp, such as PWM/IDLV/ODLV series.

Categories: LED Lighting, Operation

Yes in this situation the AUX power is available to be able to use the remote on/off function.

Categories: Industrial, Medical, Operation

During safety verification process, the agency will use a stricter standard ±10% (IEC 62368 uses +10%, -10% for the product with AC input rated) of the input voltage range labeled on the power supply to conduct the test. So, operating at the wider input voltage range as specified on the spec. sheet should be fine. The narrower range of input voltage labeled on the power supply is to fulfill the test standard of safety regulation and make sure that users insert input voltage correctly.

Tag: IEC62368

If the two phases are 180o out of phase (split phase system), then yes. The resulting voltage will be around 240VAC, so it can be used with power supplies that has input range of 200VAC-240VAC.

If the two phases are 120o out of phase, the resulting RMS voltage will be 208VAC, so it should work, but derating might be needed on some models.

For a single-phase operation, you should check the input range of the power supply in its datasheet (derating might be necessary at low input voltage).

Categories: Industrial, Operation
Tag: 2 Phase

The hold-up time is the duration between the instant when the input is shut off, and when the output voltage falls below 90% of the rated output voltage. The hold-up time is highly dependent on the internal capacitances of the PSU and the load: the higher the capacitance, the longer the hold-up time and the higher the load, the shorter the hold-up time. nA common way to increase this parameter is to use buffer modules, such as our DBUF series, or if the hold-up time only needs to be slightly increased, you could use a Power Supply with a higher power rating. (The hold-up time on the specification is based on full load condition)

Categories: Industrial, Medical, Operation

PMBus full name is Power Management Bus is an open standard for digital power management. The physical layer is based on I2C, and PM Bus had a set of commands that specifically design for power supply industry. More information can be found in

MEAN WELL Rack Power and intelligent power supply and chargers have optional PMBus solution for example: PHP-3500 and HEP-1000 further the RCP/RSP-1600, UHP-2500 and DPU-3200 have this optional available.

Categories: Charging, Industrial, Operation

A Controller Area Network (CAN Bus) is a bus standard initially developed for vehicle designed to allow multi-master with priority control without a host computer. The latest version is CAN 2.0 which consists of part A and part B. CAN 2.0A is for standard format with 11-bit identifier, and CAN 2.0B is for extended format with 20-bit identifier. CAN Bus is widely used in Automotive and industrial automation. There are not only 1 but many higher layer protocol such as CANopen, DeviceNet and more.

MEAN WELL CAN Bus product support CAN 2.0B (ISO-11898) with baud rate 250Kbps

MEAN WELL offers optionally CAN bus for PHP-3500, HEP-1000, RCP/RSP-1600, UHP-2500 and DRP/DPU-3200 and DBR/DBU-3200.

Categories: Charging, Industrial, Operation

For a 3 phase PSU, the input port L1 L2 L3 and FG should be connected to AC phase R, S, T and PE respectively. In some cases, neutral might be needed and can be configured as below:

The same configuration can also be used if one want to use multiple single phase power supply for three phase connection.

For specific power supplies i.e., 3 phase power supplies with a lower power, a dual phase operation is possible by directly connecting the 2 phases to two of the three input ports of the power supply.

DC input can also be used by applying the positive wire to any of the input ports, and the negative one to another. In both cases, derating may be needed. (e.g., TDR series)

Categories: Industrial, Operation

Most MEAN WELL power supplies are certified to be operated till 2000m. For some models the certification is valid for a higher altitude, this will be shown on the first page of the power supply under features (1)(2).
Please note that derating is needed at an altitude above 2000m. See FAQ “Do I need to derate my power supply when I used it over 2000m?

MEAN WELL’s specification shows the absolute values which were verified during design quality verification tests. Those condition are guaranteed by manufacture from quality and warranty perspectives.

When certifying a power supply according to a certain norm, there is normally a requirement described in this standard a certain tolerance which must be considered. (See also FAQ: Why Is The Input Voltage On The Label Different From The Input Voltage In The Spec? For Example, The Specification Shows Is 88~264 VAC While The Label On The Power Supply Says That It Is 100~240VAC?

The specification shows what is possible, the report and label of the power supply shows what is approved by the certifying body according to the standards.

Besides the difference due to tolerance there might also be another reason why the specification and label/test report show a different temperature. For example, if the power supply needs to be derated at a low voltage input such as 100VAC, the label and test report might show the max temperature at full load based on this low input.  

Different standards might have different tolerance requirements and different ranges this could mean that the most conservative value, or multiple values will show up on the label of the power supply.

In general MEAN WELL’s power supplies with a fan will continue to spin in no load condition. For certain power supplies where the fan will turn off in no load condition this will be marked (1) in the feature section of the specification:

MEAN WELL has incorporated dust proofing and waterproofing into the majority of its LED power supply design. Mainly based on the international standard IEC60529, detailed descriptions can be found in the following table:
(Note: PSUs with IP64 rating or above are suitable for indoor or outdoor applications in sheltered locations)

*IP64-IP66 level products are suitable for damp indoor or sheltered outdoor environment. For actual installation limitations, please refer to the corresponding IP level tests.
*All products cannot be continuously submerged in water.
*The definition of IP68 by MEAN WELL: Immerse a unit under test in 1 meter below the surface of the water, tested with a dynamic condition where 12-hour AC on; 12-hour AC off.
Test duration: 1 month.

Nowadays, customer implement magnetic component in their system to achieve fast installation and maintenance. The magnetic component should keep as far as possible from PSU to avoid interference in the control circuitry of PSU. If limitation of distance is unavoidable, install a well magnetic-conducted metal plate (ex: steel plate, copper plate) between PSU and magnetic component to minimize the interference.

MEAN WELL’s component self-heating can be found on

1. Use the search function on the website to find the right product
2. Fill in the series number in the search field (do not include the last extensions such as -12 in XLG-150-12)
3. Click the search button
4. Click on the PDF icon to open the specification

5. Click on report

6. Click on the model and scroll down:

7. The temperature of the critical component can be found in the chapter Reliability Test under item 1 Temperature Rise Test

For more details about the component type for each position, please use the Contact Us function on this website.

MEAN WELL’s DMTBF can be found on

1. Use the search function on the website to find the right product
2. Fill in the series number in the search field (do not include the last extensions such as -12 in XLG-150-12)
3. Click the search button
4. Click on the PDF icon to open the specification

5. Click on report
6. Click on the model and scroll down:

7. The DMTBF is shown on the last page of the report in the chapter

Reliability test


MEAN WELL’s MTBF can be found on

1. Use the search function on the website to find the right product
2. Fill in the series number in the search field (do not include the last 3. extensions such as -12 in XLG-150-12)
3. Click the search button
4. Click on the PDF icon to open the specification

Scroll down in the specification to the bottom of the second page

5. Find the MTBF value in under others:


MEAN WELL’s capacitor lifecycle calculation can be found on

1. Use the search function on the website to find the right product
2. Fill in the series number in the search field (do not include the last extensions such as -12 in XLG-150-12)
3. Click the search button 
4. Click on the PDF icon to open the specification

5. Click on report

6. Click on the model and scroll down:

7. The Capacitor life cycle calculation is shown on the last page of the report in the chapter Reliability test

The Capacitor life cycle calculation is considered as the key indicator for the lifetime of the power supply. Please refer to the test report of the power supply on  for the capacitor life cycle calculation.

As a rule of thumb, every 10dC increase the lifetime will be cut in half and vice versa for every 10dC decrease in temperature.

In the above example, if the power supply is used at 75dC at Ta 40dC, the estimated lifetime would be 2*104095 Hrs ~200K hrs.

This depends on the condition the power supply is used in. Please contact us for specific situations.
In general, the possibility to use the power supply in a higher temperature than specified is very low and all certifications of the power supply will become invalid.

MEAN WELL offers a selection of Surge Protection Devices to protect the power supply against surges and voltage peaks. 

Go to

  1. Select products
  2. Type in “SPD” in the search field
  3. You will find several available SPD’s

Category: Reliability

Most small wattage and fanless power supplies are mainly installed in the horizontal position. If you have to install it vertically because of mechanical limitation, you should consider the output derating due to the heat concern. The temperature derating curve can be found on the spec sheet. Regarding the power supplies with built-in fan or the application has forced cooling system, vertical and horizontal installations have less difference. Ex. In SP-150 derating curve, the ambient temperature difference in application is 5 Celsius from vertical to horizontal. The output wattage in forced cooling can be 20% higher than air cooling convection.

Category: Reliability

Depending on the cooling mechanism of the power supply there are different considerations and restriction towards the mounting orientation of the power supply and distance towards other components and self-heating components.

In general, please check our power supply user manuals on (Installation Manual-MEAN WELL Switching Power Supply Manufacturer). The actual distance and orientation depend normally on system design. Customers must review and test the power supplies in the real application and environment.

General guidelines for power supplies with different cooling mechanisms:

  • Power supplies with an internal fan or which are cooled with an external fan have less constraints regarding the orientation in which they are mounted. Nevertheless, the fans and ventilation holes must be kept free from any obstructions. Also, a 10-15 cm clearance must be kept from any adjacent heat source
  • A convection cooled power supply with standard a vertical mounting orientation which will be mounted in another orientation have to be derated by 5dC. See FAQ What should be noticed when installing a power supply in vertical and horizontal directions? Additionally ventilation holes must be kept free from any obstructions. Also, a 10-15 cm clearance must be kept from any adjacent heat source
  • Din rail power supplies can only be mounted in the specified orientation. This is with the ventilation holes at the bottom and on top of the power supply. No other mounting directions are recommended. Allow good ventilation clearances, 5mm left and right, 40mm above and 20mm below, around the unit in use to prevent it from overheating. Also, a 10-15 cm clearance must be kept when the adjacent device is a heat source.
  • For conduction cooling power supplies, the temperature on the Tc point is the key indicator if a mounting position can be allowed. The Tc position (1) and max Tc temperature (2) can be found in the product specification. Conduction cooled power supplies are for example IP65~IP68 LED drivers and base plate cooled power supplies such as UHP)  

In MEAN WELL’s specification you can find 2 derating curves, in below example the 300W open frame power supply: EPP-300

  1. The Derating Curve with the Ambient Temperature vs. Load
  2. The Derating Curve with the Input Voltage vs. Load
  1. In this Curve one can find that the maximum load of this power supply is 300W at 50dC when an external air flow of 20.5CFM is applied. For temperatures exceeding 50dC, 60dC for example additional derating need to be applied, in above case at 60dC the maximum load would be 225W. (50dC 300W, 70dC 150W => from 50dC to 60dC:  75W derating)
  1. In case this power supply would be used at 90VAC input, a derating of 80% must be applied. So, in previous example with the 20.5CFM forced air the max load would be 240W. In case of an ambient temperature of 60dC and a 90VAC input the maximum rated power would be 225W * 0.8 = 180W with 20.5CFM forced air.
  1. If the power supply is used in an application without additional forced Air, the power supply will be derated to 200W till a maximum temperature of 50dC
  2. In case it will be powered by a 90VAC input the power supply has to be additionally derated to 80% of the 200W = 160W max

LED Drivers are recommended operate at full load as long as it observes the working temperature specified in the datasheet, which means Tc measurement results should be equal to or less than the stated Tc in the datasheet. 5 years warranty complies as long as drivers operate within working Temperature and Tc. Limit as well.

MTBF (Mean Time Between Failure) and Life Cycle are both indicators of reliability. MTBF can be calculated by two different methodologies, which are “part count” and “stress analysis”. The regulations, MIL-HDBK-217F Notice 2 and TELCORDIA SR/TR-332(Bellcore) are commonly used to calculate MTBF. MIL-HDBK-217F is a United States military standard, and TELCORDIA SR/TR-332(Bellcore) is a commercial regulation. MEAN WELL utilize MIL-HDBK-217F(Stress Analysis) as the core of MTBF. The exact meaning of MTBF is, after continuously using the power supply for a certain amount of time, the average time that the probability of proper operation is down to 36.8%(e-1=0.368). Currently MEAN WELL is adopting MIL-HDBK-217F, to predict the expected reliability through Stress Analysis (excluding fans); this MTBF means the probability of the product can continue the normal work after working continuously up to the calculated MTBF time is 36.8% (e-1=0.368). If the power supply is continuously used at double the MTBF time, the probability of proper operation becomes 13.5%(e-2=0.135.

DMTBF (Demonstrated Mean Time Between Failures) is a way of evaluating MTBF in a relatively short period of time based on accelerated deterioration (high stress, high temperature) tests under specific parameters and conditions. Please refer to the following equation for MTBF calculation.
This method compares to the previous methods, this calculation uses real test data to demonstrate the reliability of the power supply.


MTBF: Mean Time Between Failure

  • X2:Can be found in chi-square distribution
  • N:Number of sampling
  • AF:Acceleration factor, which can be derived from acceleration factor equation.
  • Ae=0.6
  • K(Boltzmann Constant)=(eV/k)
  • T1:Rated temperature of specification. Note: Kelvin will be the unit use for calculation
  • T2:The temperature that is used in the meaning of acceleration, and the chosen temperature could not result in physical change in materials. 

Note: Kelvin will be the unit use for calculation.  

Life Cycle (Capacitor Life Cycle) is found by using the temperature rise of electrolytic capacitors under maximum operating temperature to estimate the approximate life of the power supply. For example, RSP-750-12 MTBF=109.1K hours(25°C); electrolytic capacitor C110 Life Cycle=213K hours (Ta=50℃).

MEAN WELL considers the capacitor lifecycle calculation as the most important indicator for the estimated lifetime. The (D)MTBF is the main indicator for the reliability of the power supply. For more information please see:  Investigation of The Lifetime & Reliability of Power Supply -MEAN WELL EUROPE Switching Power Supply

No, they are different. SELV means the LED driver will use a safety isolating transformer with double or reinforced insulation and the output voltage shall not exceed 120Vdc.
This is good for the end product safety certified if the LED driver with SELV output.


MOOP stands for Means of Operator Protection. This category is related to electronic devices which are handled by trained operators, and do not come into direct contact with the patient. The medical device with 2 x MOOP has an isolation of 3000Vac isolation

MOPP, on the other hand, is the Means of Patient Protection; all electronic devices with direct physical contact with patients must meet stricter standards and require a double isolation between input and output.
For more information, you can find in our medical application section: Medical

Categories: Compliance, Medical

The requirement of LPS is from IEC60950. It means the product output shall not exceed 60V/8A/100W under the normal and abnormal condition.
If the power supplies can meet LPS, the end product does not need the fire enclosure.

Categories: Compliance, Industrial
Tag: LPS

MEAN WELL aims to design the power supply in such way that there is sufficient margin for your system to pass the EMC requirements on system level. However we cannot guarantee that the final system can still meet the EMC requirements. The location, wiring and grounding of the switching power supply in the system may influence its EMC characteristics. In different environment or applications, the same switching power supply may have different outcomes. Our test results are based on setup shown in the EMC report.

Categories: Compliance, Industrial, Medical

The definition of SELV was defined in the IEC 60950 standard but it is not defined in the  IEC 62368 standard. This has been replaced with the ES1 Energy sources definition.

The definition of SELV is still applicable to the 61347-2-13 standard. In this standard it is that a LED driver will use a safety isolating transformer with double or reinforced insulation and the output voltage shall not exceed 120Vdc.

In the specification MEAN WELL’s 61347-2-13 certified LED drivers are marked with the SELV symbol in the case that the SELV requirements are fulfilled:


MEAN WELL has a global safety team. Case by case it might be possible to apply for additional certifications for certain of our products. Please discuss the possibilities via your local Mean Well sales channel. If you are unable to get the support, please contact us via this website.

Category: Compliance

MEAN WELL’s EMC reports are not available online. In case you need these reports to validate your design with your certifying body, please contact your local MEAN WELL sales channel for support. If you are unable to get the support, please contact us via this website.

Category: Compliance
Tag: EMC report

MEAN WELL’s safety reports, IEC reports and CB reports are not available online. In case you need these reports to validate your design with your certifying body, please contact your local MEAN WELL sales channel for support. If you are unable to get the support, please contact us via this website.

Tag: CB reports

MEAN WELL’s User Manual can be found on
1. Go to products
2. Click on Installation Manual

3. Scroll down to find the user manuals for the different product families.

MEAN WELL’s Safety certifications can be found on

  1. Use the search function on the website
  2. Fill in the series number in the search field (do not include the last extentions suchs as -12 in XLG-150-12
  3. Click the search button

4. Click on the PDF Link

5. Click on the top on the certificate
6. All available certificates are shown and will show up once clicked upon

MEAN WELL’s CE declarations can be found on

  1. Use the search function on the website
  2. Fill in the series number in the search field ( do not include the last extentions suchs as -12
  3. Click the search button

4. Click on the PDF Link

5. Click on the top on certificate
6. Click on CE declaration

Select (1) Products followed by (2) downloads

MEAN WELL’s EMI test guide can be found on

Select (1) Products followed by (2) Downloads

Or you can use this link to directly download the EMI testing guide:

Tags: EMC, EMI

MEAN WELL’s RoHS and Reach statements can be found on

Select (1) Products followed by (2) Downloads:



After this scroll down to find the RoHS declaration and Declaration of SVHC/ REACH conformity:


Or you can use these below links to download the declarations:

REACH SVHC Delaration.pdf


MEAN WELL’s Declaration of Conflict Free Minerals can be found on

Select (1) Products followed by (2) Downloads

After this scroll down to find the Declaration of Minerals Conflict Free

Or you can use this Link to directly download the EMI testing guide:

Download the EMI testing guide

A Surge Protection Device is optimized for a single voltage. Therefore, SPD should be chosen according to the actual operating voltage of the part that need to be protected.Secondly, the voltage protection level shows what is the maximum voltage appeared at output side when a specified surge is coming to the SPD. In general, the lower the voltage protection level, and the higher the discharge or surge current from SPD, means the better protection that the SPD provides.

Enclosed power supplies:

  • 35-125W applications: The RD, RT and RQ series provide dual, triple, and quadruple output.
  • 150-320W applications: The QP series comes with 4 different outputs.
  • 190-240W applications: The semi-potted HDP series provides dual output.

PCB-type power supplies:

  • 25-250W applications: The PD and PT series provide dual and triple output.
  • 45-200W medical applications: The MPD, MPT and MPQ series offer dual, triple, and quadruple output.

Configurable power supplies:

  • 400W fanless, the UMP-400 series is a convection cooled 1U height modular power supply and can provide up to 4 different outputs.
  • 450-1000W for ITE applications, MP series provides up to 7 different isolated outputs.
  • 650-1200W for ITE and medical applications, NMP series can provide up to 6 different isolated outputs with the NMS single output modules from 3~55VDC. With the NMD dual output module more outputs are possible in the 3~30VDC range. Additionally, the NMP offers a 5V AUX output.

Please also see our “NMP Page

Desktop-type power supplies:

  • 25-50W applications, our GP series is a triple-output type industrial adaptor. 

DC-DC modules:

  • 1-2W applications, the SMD-type DETN series comes with +/-5, 12 or 15V symmetrical outputs.
  • 3-30W applications, the DIP-type DCW, DCWN, RDDW, DKM, DKMW, DKA30 series come with +/- 5, 12 or 15V symmetrical outputs.
  • 20W ultra-wide input range requirements, the DIP-type RDDW20UW series can provide a +/-12, 15 and 24V symmetrical output.
  • 15W applications, the DIP-type DKE15 series offers a +/-5, 12, 15 or 24V symmetrical output.
  • 30W applications, the DIP-type TKA30 series offers a 5V output in addition to a +/-12 or 15V symmetrical output.
  • 10-15W applications, the on-board-type NSD series can provide a +/- 5, 12 or 15V symmetrical output.
Categories: Industrial, Medical, Others

The number of outputs, the available output voltage range and minimum load requirements are some key aspects to be considered when it comes to choosing a multiple output type PSU.

Basic power supplies in this category have a so-called minimum load requirement. These types of PSU rely on one same internal transformer to provide different outputs. For all outputs to work properly, a minimum current should always be drawn from the main output channel.

See below example how this is shown in the specification for the RPT-60A

More advanced power supplies such as the RT-65A do not have this restriction:

There are two options to select a multiple output PSU: a standard PSU with fixed output voltages, or modular power supplies. Modular PSUs can be personalized according to one’s systems requirements and offer much more flexibility than fixed output voltages PSUs. For instance, our NMP modular medical power supply series come with up to 6 slots for different output voltages from 3 to 55V which can be connected in series and parallel to adapt to each application.

Categories: Industrial, Medical, Others

This information can be found back in our installation manual, please visit “Installation Manual-MEAN WELL Switching Power Supply Manufacturer” and select the right product (group) and language.

Categories: Industrial, Others

Yes, CSP-3000 and PHP-3500-HV series both come with an inclusive choice of output voltages (120, 250, 400VDC). Also, our IP67 rated HEP-1000 series can provide DC output up to 100VDC.

Categories: Industrial, Others
Tag: DC Systems

All MEAN WELL power supplies come with at least one fuse on the line path1. The internal fuse is designed to handle the nominal current on the whole range of input voltages; for the same power, at low input voltages, the current drawn by the PSU will be higher:

LPV-100 input ratings (internal T 4AL-250VAC fuse)

If you want a more adapted protection for a specific input voltage, you could add an external fuse to protect the power supply. Considering that it will only protect the PSU (no other appliances connected after it), you should refer to the datasheet of the power supply and look for the typical input current under your input voltage. The fuse should be rated slightly higher than this current value. The selected external fuse should be a Slow-Blow type, this to avoid it is triggered by the inrush current of the power supply. For reference, most of MEAN WELL power supplies use type-T slow acting fuses. 

Further please take into consideration that fuses characteristics are given for an operating temperature of 25oC. Exceeding this value will lower the current rating and shorten its lifetime. Similarly, when operated in cold areas, the current rating will be increased.

Note 1: Except for DDRH-60 series

Categories: Industrial, Medical, Others

To download a digital version of our catalog, go to

1. Click on Products
2. Click on Downloads

Find our (3) LED driver, our (4) Industrial power and (5) short forms

Category: Others

Find the latest news in the MEAN WELL APP

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MEAN WELL’s distributor information can be found on Distributor Network-MEAN WELL Switching Power Supply Manufacturer 

  1. Click on the region that you are located
  2. Select the country you are in
  3. Click on the search button
  4. Scroll down to see our local distribution channels
  5. Look for the distributor with a tick for the product group that you are looking for

MEAN WELL has the largest distribution network for serving your small and medium demand Power Supplies. You can find all MEAN WELL’s distribution channels on Distributor Network-MEAN WELL Switching Power Supply Manufacturer

OEM’s which have no sales channel for MEAN WELL products yet can contact us via the “Contact Us” form on this website.

MEAN WELL’s discontinued product schedule and End of Life products are normally updated 2 times per year, in January and in July and are published on See FAQ “Where can I find MEAN WELL’s discontinued product schedule and End of Life information?

The normal procedure for E.O.L. is:

  1. The product or series is announced in the Discontinued product list in January or July and announced as NRND (Not Recommend for New Design) 
  2. 6 months later the lead time of the product or series will increase +30 days, the price will increase as well.
  3. Another 6 months later, the lead time will increase another +30 days (so + 60day compared to the original lead time), the price will increase again.
  4. Another 6 months later, the lead time will increase another +30day (so +90 days compared to the original lead time) and the price will increase again and additionally there will be a MOQ of 200pcs (and steps of 100 for higher quantities)
  5. After another 6 months the last buy is announced on the website. This will be the last opportunity to place an order for this product or series.

In total MEAN WELL’s End of Life, procedure will take 2 years. However, there are situations for instance that certification is expired, or some components can no longer be obtained by the market which will force to accelerate the EOL schedule. Therefore, it is always highly recommended from the moment that a product is on the discontinued list to design in one of our new generation products. If need any advice to this, please use the “Contact Us” function on this website.

MEAN WELL’s discontinued product schedule and End of Life products are normally updated 2 times per year, in January and in July. To see the full list, go to

1. Click on products

2. Click on Discontinued products for the schedule for the EOL schedule 

Click on EOL for the MEAN WELL products which are End Of Life

You can use the “Contact Us” function on this website

MEAN WELL’s website provides you all the basic information about our Power Supplies. This includes company news, product announcements, ISO certificates, Specifications, test report, Certificates, ROHS declarations, Reach declarations and many more.

MEAN WELL’s products can be found on

1. Click on products and select the product category

Or in case you already have a part number, you can use the search function on the website:

2. Use the search function on the website to find the right product

3. Fill in the series number in the search field (do not include the last extensions such as -12 in XLG-150-12)

4. Click the search button 

5. Click on the PDF icon to open the specification

Owing to line (voltage)-drop, we suggest the extension made from AC cable. In case DC cable extension is necessary, please consider Line-Drop leading to insufficient Vf so that the LED model or lamp may fail to switch ON. Moreover, EMC performance and characteristic may also be affected by DC cable extension.

Categories: LED Lighting, Others

First, you have to know your Led lamp specification in order to screen out a suitable Led driver range (Wattage, Voltage, Max Current CC or CV). From those ranges, further check a compatible dimming function. Hereunder is a table to show you the pros and cons of Dimming Function you can find in MW’s catalogue.

Categories: LED Lighting, Others

MEAN WELL has several charger products, and we suggest choosing them first. Chargers would be more suitable since they are designed for charging applications. Safety and approvals should be taken into account based on the final application. If you are unable to find a proper model in our charger series, our LED CC models can be used as charger. Please choose suitable products after confirming the current and voltage specification on the datasheet of the battery.

Categories: Charging, LED Lighting, Others

3 in 1 dimming circuit would drain 0.1mA per model. Dividing the rated current of the dimmer by the 0.1mA, and we could know how many units can be controlled by one dimming device. For resistance dimming applications, resistance for 100% dimming output would be 100K ohm divided number of models.

Categories: LED Lighting, Others

A LED strip is normally a Constant Voltage application (CV). For this type of CV application MEAN WELL has design the PWM, IDLV and ODLV series which will allow CV applications to dim.

Categories: LED Lighting, Others

3 in 1 dimming is the most common application used in LED dimming with the feature that it does not have to work with any specific dimmer. The only thing that has to be verified is that whether the dimmer (1~10V/10V PWM/resistance) is compatible with the definition advised in our specs.

Categories: LED Lighting, Others

All MEAN WELL chargers are preset for lead-acid batteries. For other products that can customize the charging curve (such as ENC / NPB series), customers can customize their charging curve depending on the charging and discharging characteristics of batteries. If you have other requirements, please use the contact us function on this website.

Categories: Charging, Others

Noise is directly related to the fan which is built into the power supply. Lowering the airflow of the fan means reducing the heat dissipation ability. It will also influence the reliability of the products. Furthermore, minimum airflow of fans is defined by Safety Organization and a safety appendage will be needed if using a new fan. If fan noise is a critical concern, we suggest to select FANLESS products or contact MEAN WELL for other possibilities according to the conditions of use.

Categories: Industrial, Medical, Others
Tags: Fanless, Noise

There are two different applications when power supplies are connected in series. One is to generate plus minus voltage, another is to increase total output voltage. Connection methods are as follows:

(1) Connection for plus and minus voltage are shown as follow

(2) To increase the total output voltage (Output current remain the same). Diodes connect in parallel at output side of the driver is necessary to prevent damage during start up. The voltage rating of diode shall greater than V1 + V2(shown as figure below), in addition, peak forward surge current rating shall greater than rated current.

* Because part of the signal ground is shorted with output ground, strongly suggest to use isolated signals to achieve control scheme, in order to prevent damage to the product.

Categories: Industrial, Medical, Others

MEAN WELL has launched ENC, HEP-600C, GC, PA, PB, RPB and RCB series for battery charge applications (30~1000W). However, if these models cannot fulfill your requirements, there is an alternative solution. Power supplies with constant current limiting as overload protection are suggested. Charge current varies in battery percentage (full or flat), there is high possibility to trigger overload protection when battery is low, those with overload protection as hiccup or shutdown will stop charging the battery in low battery condition. Yet, using a power supply as charging purpose is considered as overload usage, modification is required. Please Contact Us for the request.

Categories: Charging, Industrial, Others

An adaptor may need connection of a power cord to receive energy needed from the utility. You can refer to the specification of the adaptor for the connector (AC inlet) at the adaptor end of the power cord; Different countries/regions vary in type of AC socket and voltage, please look at the table below for the information of the AC plug you need.

Categories: Industrial, Medical, Others

MEAN WELL’s LED product specification normally exhibits V-I characteristics. Per the characteristics, there are generally two types of drivers, the “CC” type and the “CC+CV” type. “CC” type of driver is suitable only for LED applications whereas “CC+CV” is for either LED applications or general switching power supply applications. The section that is not suitable for LED applications are represented by dotted line, and based on the protection procedures it can be categorized into hiccup mode and constant current mode; in this section, the tolerance of current is not defined but only the characteristic of current is displayed. If customers attempt not to see a very high current under short circuit conditions, those models with hiccup mode for this section can be selected; if there are applications with motors or capacitive load, those with constant current can be chosen.

Categories: LED Lighting, Others
Tag: CC+CV

There are 2 types of Power Factor Correction circuits; one is Single Stage; the other is Two Stage.

Single Stage power supply combines functions of power factor correction and converter in one circuit but Two Stage use two separate circuits. Compared to Single Stage, Two Stage design is more complex and costly, but the immunity performance of Two Stage power supply against AC mains is much better than that of Single Stage power supply. In addition, Two Stage power supplies manifest better ripple noises performance on output. Owing to that Single Stage is only suitable for fields with quality AC mains but Two Stage can be used in serious circumstances for LED drivers or as industrial switching power supplies.

Categories: LED Lighting, Others

It is the small unwanted residual periodic variation of the direct current (DC) output of a power supply which has been derived from an alternating current (AC) source. The wave form is shown as figure below.

There are two AC contents, also known as Ripple and Noise (R&N), on the DC output. The first one, coming from sine wave rectification, is at a low frequency which is 2 times of the input frequency; the second one is at high frequency which is from the switching frequency. For measuring high frequency noise, a configuration of an oscilloscope with a bandwidth of 20MHz, a scope probe with shortest ground wire possible, and add 0.1uF and 47uF capacitors in parallel with test point for filtering out noise interference are required.

Categories: Industrial, Medical, Others

1. To increase the reliability of the power supply, we suggest users choose a unit that has a rating of 30% more power than actual need. For example, if the system needs a 100W source, we suggest that users choose a power supply with 130W of output power or more. By doing this, you can effectively boost the reliability of the power supply in your system.

2. We also need to consider about ambient temperature of the power supply and whether there is additional device for dissipating the heat. If the power supply is working in a high temperature environment, we need to make some derating to the output power. The derating curve of “ambient temperature” versus “output power” can be found on our specifications.

3. Choosing functions based on your application:

  • Protection function: Over Voltage Protection (OVP), Over Temperature Protection (OVP), Overload Protection (OLP), and etc.
  • Application function: Signaling Function (Power Good, Power Fail), Remote Control, Remote Sensing, and etc.
  • Special function: Power Factor Correction (PFC), Uninterruptible Power Supply (UPS) function.

4. Make sure that the model qualifies for the safety standards and EMC regulations you need.

Categories: Industrial, Medical, Others

All MEAN WELL power supplies have an internal fuse except for the DDRH series.

Categories: Industrial, Medical, Others
Tag: Fuse

MEAN WELL’s Step files/ 3D files can be found on

  1. Use the search function on the website to find the right product
  2. Fill in the series number in the search field (do not include the last extensions such as -12 in XLG-150-12)
  3. Click the search button 
  4. Click on the PDF icon to open the specification
  1. Click on 3D OUTLINE
  2. Click on the model XLG-150-3D to download the step file.