faq

FAQ

If you have questions on WEHO’s products, please read the FAQ first. If the listed answers still cannot solve your problems, ease contact us or mail us , We would reply to you as soon as received your request.

As a dedicated manufacturer of standard power supplies, WEHO provides a wide variety of power supplies to meet different demands from the markets. However, selecting the right products relies heavily on the correct electrical characteristics and specification, we listed the frequently asked questions for your reference.

WEHO is manufacturer of power supply for 15 years , from 10w to 3000w .

3V 5V 9V 12V 13.8V 15V 18V 24V 27V 36V 48V 60V 70V 72V 90V 110V And so on .

From 0.5A to 125A (Max power to 3000w )

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.
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.
he derating curve of “ambient temperature” versus “output power” can be found on our spec sheets.
Choosing functions based on your application:
Protection function: Over Voltage Protection (OVP), Over Temperature Protection (OVP), Over Load 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.
Make sure that the model qualifies for the safety standards and EMC regulations you need.

There are some minimum-load requirements on WEHO’s multi-output power supplies. Please read the specification first before connecting to the load. In order 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.

In general there are two circumstances that will cause the power supply to shut down. The first one is the activation of the over-load-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 of these conditions will let the S.P.S. enter protection mode and shut down. After these conditions are removed, the S.P.S. will be back to normal.

Cooling fans have a relatively shorter lifetime (typical MTTF, Mean Time To Failure, of around 5000-100000 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:

Temperature 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.
Load 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 (20~100A based on the design of S.P.S.) 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. Besides, 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 S.P.S. to turn them on/off.

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

Due to different circuit designs, WEHO power supply’s input consists of three types as below:
(VAC≒VDC)
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.

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 purpose.
Power Good: after the output of a power supply reaches 90% rated voltage, an 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.

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:
(1)FOLDBACK CURRENT LIMITING
Output current decreases about 20% of rated current, shown as curve (a) in the figure below.
(2)CONSTANT CURRENT LIMITING
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.
(3)OVER POWER LIMITING
Output power remains constant. As output load increases, output voltage decreases in proportion, shown as curve (c) in the figure below.
(4)HICCUP CURRENT LIMITING
Output voltage and current keep pulsing ON and OFF repeatedly when protection is activated. The unit automatically recovers when faulty condition is removed.
(5)SHUT OFF
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.

There are 2 types of Power Factor Correction circuits; one is Single Stage and 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 PSU against AC mains is much better than that of Single Stage PSU; in addition, Two Stage manifests 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 circumstance for LED drivers or as industrial switching power supplies.

industrial automation control, military equipment,
scientific research equipment, LED lighting, industrial control equipment,
communication equipment, power equipment, instrumentation, medical equipment,
semiconductor refrigeration and heating, air purifier, electronic refrigerator,
liquid crystal display, LED lamps, communication equipment,
audio-visual products, security monitoring, LED lamp belt,
computer case, digital products and so on. Instruments and other fields.

a.Two years warranty for each switching power supply

b.A strict quality control inspection before shipment

c. shockproof & high quality blister packing to protect the item from damaging during shipment

Wave solder machine,Automatic Insertion machine ,High and low temperature heat Chamber, EMI tester Receiver, Leakage current tester ,Comprehensive Performance Tester ,
Voltage tester ,Aging Tester ,Resistance Tester, Automatic Double Liquid Glue Machine,Shrink Packaging Machine ,Pachage Tape Machine .

ODM design & OEM packing welcome

a.MOQ:We support sample order. (1~5 pieces) within 3days

b.More than 500 pieces ,the lead time is 10-15days

c. More than 5000 pieces ,The lead time is 22-30days

We usually ship by DHL, UPS, FedEx or TNT. It usually takes 3-5 days to arrive. Airline and sea shipping also optional.

For our customers’ convenience, we accept various payment methods as below:

PayPal
Credit Card (through PayPal or alibaba)
Wire Transfer (regular Bank transfer)
L/C D/A D/P O/A

Yes ,if you annuals sales much more than our other customers in your market that you can be our distributor

Tel:86-577-61777088 Fax:86-577-61777072 Skype:Chnwh005
Email:[email protected] Whatsapp:86-15869492061