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1:Notes on choosing a switching power supply(LED power supply)?

                                                                                                             
To increase the reliability of the switching power supply/adapter, 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 switching power supply/adapter with 120W of output power or more.
By doing this, you can effectively boost the reliability of the switching power supply/adapter in your system.
We also need to consider about ambient temperature of the switching power supply/adapter and whether there is additional device for dissipating the heat. If the switching power supply/adapter 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 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.


 
2: Can KRECO's power supply be used in the range of 45Hz ~ 440Hz? If YES, what will happen?
                                                                                                                
KRECO's power supply can be used within this frequency range. But if the frequency is too low, the efficiency will also be lower.


 
3. When testing a dual output power supply, the +5V channel is correct, but the +12V channel is over the specification. What is going on?
                                                                                                                
There are some minimum-load requirements on KRECO's multi-output power supplies, please refer to the specification first before connecting the load. When the load condition is 5V/4A, 12V/0A, the output voltage of the 12V channel will be around 12.8V that is over the ?% of voltage deviation (12.72V) specified in the spec. sheet. If we add in the minimum load 0.2A to the 12V channel, the 12V channel will reduce to around 12.3V which is within the specification.


 
5. Why did the AC/DC switching power supply shuts down during operation and after turning it off, I can restart the power supply again?
                                                                                                                
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 switching power supply/adapter enter protection mode and shut down. After these conditions are removed, theswitching power supply/adapter will be back to normal.


 
6. Why the fan is not running after turning on certain models( for our 250Watt to 360Watt model)?
                                                                                                                
Some models control the fan based on internal temperature to extend its life time.


 
7. What is "Inrush Current"? What will we notice?
                                                                                                                
At input side, there will be (1/2 ~1 cycle, ex. 1/120 ~ 1/60 seconds for 60 Hz AC source) large pulse current (20~60A based on the design of switching power supply/adapter) 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 there. It is suggested that these power supplies start up one by one or use the remote control function of switching power supply/adapter to turn them on/off.


 
8. What is PFC?
                                                                                                                
PFC stands for Power Factor Correction.
The purpose of PFC is to improve the ratio of apparent power and real power. The power factor is only 0.4~0.6 in non-PFC models. In PFC models, the power factor can reach above 0.95. The calculation formulas are as below:
Apparent Power=Input Voltage x Input Current (VA)
Real Power= Input Voltage x Input Current x Power Factor (W)
From the environment friendly point, the electric power plant needs to generate a power which is higher than apparent power in order to steadily provide electricity to the market. The real usage of electricity should be defined by real power. Assuming the power factor is 0.5, the power plant needs to produce more than 2VA to satisfy 1W real power. On the contrary, if the power factor is 0.95, the power plant only needs to generate more than 1.06VA to provide 1W real power need. It will be more effective.


 
9. What is the difference between -V and COM which are marked on the output side?
                                                                                                                
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)


 
10. What is the real input voltage range In KRECO's product specification ?
                                                                                                                
Due to different circuit designs, KRECO AC/ DC power adapter/supply 's input consists of three types as below:
a.90~264VAC;100~240VAC
b.176~264VAC;
c.85~132VAC/176~264VAC by Switch;
d.80~300VAC


 
11. What is MTBF? Is it distinct from Life Cycle?
                                                                                                                
MTBF and Life Cycle are both indicators of reliability. KRECO uses MIL-HDBK-217F as the core of MTBF. An expected reliability is forecasted through accounting component's number (exclude fans).
The exact meaning of MTBF is after continuously using of power supply in a certain time, the probability of operating properly is 36.8%(e-1=0.368). If power supply is continuously used at double the MTBF time, the probability of operating properly becomes 13.5%(e-2=0.135).
Life Cycle is found through using the temperature rise of electrolytic capacitor to estimate the approximate life of power supply. For example, SP-750-12 MTBF=769.3K hours; electrolytic capacitor C108 Life Cycle=202.2K hours (Ta=45?C).


 
12. What is power good and power fail signals and how can use it?
                                                                                                                
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.


 
15: How do we choose a switching power supply to charge a battery?
                                                                                                                
KRECO has some series are designed as a charger, we advice to pick up one which over load protection (OLP) mode is constant current limiting. The models in this mode provide constant current even when the protection circuit is triggered.
The second choice is fold-back current limiting or constant wattage model. In this model, when a battery is running low, the output current of the power supply will gently increase. The level of increase depends on battery's capacity and degree of exhaustion.


 
16: If we need a 24V output power supply, but KRECO does not have this model, can we use two 12V power supplies connecting in series instead of one 24V power supply?
                                                                                                                
YES, basically you can do this to get the right output voltage, but be careful that the rated output current of the series system should be the rating of the minimum one in
these series connected power supplies. Furthermore, we like you to parallel a diode at the output of power supply to prevent possible damage of internal capacitors


 
17: Why I can not turn on the power supply smoothly when the loads are motors, light bulbs or capacitive loads?
                                                                                                                
If you connect the switching power supply/adapter to motors, light bulbs, or high capacitive loads, you will have a high output surge current when you turn on the switching power supply/adapter and this high surge current will cause failure of start up. We suggest using switching power supply/adapter with constant current limiting protection to deal with these loads.


 
18: During the operation of KRECO power supply, there is some leakage current on the case. Is this normal? Will this leakage current hurt human body?
                                                                                                                
Due to the requirement of EMI, there will be some Y capacitors between line and neutral to the FG (case) to improve EMC. These Y capacitors will cause some leakage current flow from line or neutral to the case (normally case will be connected to earth ground). For example, IEC-60950-1 requires that this current should be less than 3.5mA for IT equipment, so basically the leakage current you find on the case will not hurt human body. Proper connection to Earth ground will solve the leakage current problem.


 
19: For certain need, is it possible to reduce the noise of fan?
                                                                                                                
Noise is directly related to the fan which is build 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. Generally, when we choose a suitable power supply, fan is not necessary if wattage is under 150W. Between 150~250W, both fan and fanless products are available. Above 250W, a fan is needed.


 
20: What should be noticed when installing a power supply in vertical and horizontal directions?
                                                                                                                
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.


 
21: Can KRECO charger use on Lithium battery or other type of battery?
                                                                                                                
Some of chargers are designed for lead-acid batteries, some of chargers are designed for Lithium battery.
Other type of battery will have its own charging/discharging characteristic.
Modification will be required for our charger in order to match the profile of each battery or users' requirements. Please contact our salesperson if you would like to have a modification for your own battery.


 
22: Why the input voltage marked on the spec sheet is 90~264 VAC while the label on the power supply says that it is 100~240VAC?
                                                                                                                
During safety verification process, the agency will use a stricter standard (IEC60950 uses +6%, -10%) 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.


 
23: Will KRECO's products with CE marking meet the EMC requirements after assembling into my system?
                                                                                                                
We cannot guarantee 100% 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.


 
25: What is different between information (EN60950-1) and medical (EN60601-1) safety standard?
                                                                                                                
According to safety standard, the leakage current in EN60950-1 Class I cannot exceed 3.5mA; in EN60601-1 cannot exceed 0.3mA.
Others criteria like safe distance and numbers of fuse are also different.


 
26: What is class 2, class II and LPS? What is the difference between class I and class II?
                                                                                                                
Class I: Equipment where protection against electric shock is achieved by using basic insulation and also providing a means of connecting to the protective earth conductor in the building where by routing those conductive parts that are otherwise capable of assuming hazardous voltages to earth ground if the basic insulation fails. This means a class I switching power supply/adapter will provide a terminal/pin for earth ground connection.
Class II: Equipment in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions, such as double insulation or reinforced insulation are provided, there being no reliance on either protective earth or installation conditions. This means a class II switching power supply/adapter does NOT have a terminal/pin for earth ground connection.
LPS: When an electronic circuit is powered by a limit power source, its output current and power are under the limitation shown in Table 3.4, and the risk of fire can be reduced significantly. So, the safety distances and flammability rating of components can be much lower. In this way, the design cost for switching power supply/adapter compliant with LPS can be reduced as compared with non LPS switching power supply/adapter.


 
27: What is SELV? Are all KRECO switching power supply/adapters compliant with SELV?
                                                                                                                
This regulation applies to the secondary circuitry. The circuit should be designed to guarantee that under normal operating conditions, the voltage between any two touchable points should be less than 42.4Vpeak or 60Vdc. For class I equipment, it refers to "between any touchable point and the ground." Under single fault conditions, the voltages between any two conductors of the SELV circuit and between any one such conductor and earth shall not exceed 42.4V peak or 60Vdc for a period longer than 0.2 seconds. Moreover, a limit of 71V peak or 120Vdc shall not be exceeded.
According to requirements below, KRECO switching power supply/adapters can comply with SELV.
IEC 60950-1 (ITE switching power supply/adapter): voltage of o/p circuit is less than 60Vdc under normal condition.
IEC 61347-2-13 (LED switching power supply/adapter): voltage of o/p circuit is less than 120Vdc under normal condition.


 
28: What is the Max output power for EI28 size AC/DC adapter? and Max output Current?
                                                                                                                
There is 2 conditions to Output Power for EI28 size AC/DC adapter.
Condition A.)When input voltage is at 100VAC(Japan electricity) or 110 to 120VAC(Taiwan and America elctricity)or 127VAC(Brasil electricity)condition,the Max output power is 2.5 watt and the Max output current is 600mA.
Condition B.)When input voltage is at 220VAC(China,Middle east,Asia electricity) or 230 to 240VAC(whole Europe,Australia,Russia elctricity)or peak 300VAC(some country like india electricity)condition,the Max output power is 2.3 watt and the Max output current is 550mA.


 
29: What is the Max output power for EI28 size AC/AC adapter? and Max output Current?
                                                                                                                
There is 2 conditions to Output Power for EI28 size AC/AC adapter.
Condition A.)When input voltage is at 100VAC(Japan electricity) or 110 to 120VAC(Taiwan and America elctricity)or 127VAC(Brasil electricity)condition,the Max output power is 3 watt and the Max output current is 600mA.
Condition B.)When input voltage is at 220VAC(China,Middle east,Asia electricity) or 230 to 240VAC(whole Europe,Australia,Russia elctricity)or peak 300VAC(some country like india electricity)condition,the Max output power is 2.8 watt and the Max output current is 550mA.


 
30: What is the Max output power for EI35 size AC/DC adapter? and Max output Current?
                                                                                                                
There is 2 conditions to Output Power for EI35 size AC/DC adapter.
Condition A.)When input voltage is at 100VAC(Japan electricity) or 110 to 120VAC(Taiwan and America elctricity)or 127VAC(Brasil electricity)condition,the Max output power is 4.8 watt and the Max output current is 1000mA.
Condition B.)When input voltage is at 220VAC(China,Middle east,Asia electricity) or 230 to 240VAC(whole Europe,Australia,Russia elctricity)or peak 300VAC(some country like india electricity)condition,the Max output power is 4.6 watt and the Max output current is 900mA.


 
31: What is the Max output power for EI35 size AC/AC adapter? and Max output Current?
                                                                                                                
There is 2 conditions to Output Power for EI35 size AC/AC adapter.
Condition A.)When input voltage is at 100VAC(Japan electricity) or 110 to 120VAC(Taiwan and America elctricity)or 127VAC(Brasil electricity)condition,the Max output power is 4.8 watt and the Max output current is 1000mA.
Condition B.)When input voltage is at 220VAC(China,Middle east,Asia electricity) or 230 to 240VAC(whole Europe,Australia,Russia elctricity)or peak 300VAC(some country like india electricity)condition,the Max output power is 4.6 watt and the Max output current is 950mA.


 
32: What is the Max output power for EI35 size AC/DC adapter? and Max output Current?
                                                                                                              
There is 2 conditions to Output Power for EI41 size AC/DC adapter.
Condition A.)When input voltage is at 100VAC(Japan electricity) or 110 to 120VAC(Taiwan and America elctricity)or 127VAC(Brasil electricity)condition,the Max output power is 9 watt and the Max output current is 1000mA.
Condition B.)When input voltage is at 220VAC(China,Middle east,Asia electricity) or 230 to 240VAC(whole Europe,Australia,Russia elctricity)or peak 300VAC(some country like india electricity)condition,the Max output power is 8.5 watt and the Max output current is 950mA.


 
33: What is the Max output power for EI41 size AC/AC adapter? and Max output Current?
                                                                                                              
There is 2 conditions to Output Power for EI41 size AC/AC adapter.
Condition A.)When input voltage is at 100VAC(Japan electricity) or 110 to 120VAC(Taiwan and America elctricity)or 127VAC(Brasil electricity)condition,the Max output power is 10 watt and the Max output current is 1500mA.
Condition B.)When input voltage is at 220VAC(China,Middle east,Asia electricity) or 230 to 240VAC(whole Europe,Australia,Russia elctricity)or peak 300VAC(some country like india electricity)condition,the Max output power is 9.5 watt and the Max output current is 1200mA.


 
35: What about the Max output power and current for others like EI48 and EI57 and EI66 sizeAC/DC adapter ,AC/AC adapter or transformer?
                                                                                                               
Let's say it is more simple:
if AC to DC(AC/DC)adapter or transformer at condition A(100-120V,see above):
EI48 size: 23 Watt,1600mA current
EI57 size: 41 Watt,2500mA current
EI66 size: 60 watt,4500mA current
if AC to DC(AC/DC)adapter or transformer at condition B(220-240V,see above):
EI48 size: 22 Watt,1500mA current
EI57 size: 40 Watt,2300mA current
EI66 size: 58 watt,4200mA current
if AC to AC(AC/AC)adapter or transformer at condition A(100-120V,see above):
EI48 size: 24 Watt,1800mA current
EI57 size: 42 Watt,2700mA current
EI66 size: 65 watt,5000mA current
if AC to AC(AC/AC)adapter or transformer at condition B(220-240V,see above):
EI48 size: 24 Watt,1700mA current
EI57 size: 42 Watt,2600mA current
EI66 size: 65 watt,4800mA current


 
36: Why you don't accept small quantity order which below your MOQ?
                                                                                                                
Because our raw materials venders refuse to provide raw materials to us if order quantity below MOQ, even we pay extra
price for them. There is much much more expenses and works to do compare to normall quantity production. like: ship production fee, high
labor cost, Labor power.etc.
So we should say no to the quantity which below our MOQ. please appreciate our situation.


 
37: Why KRECO samples get failure in EMC testing?
                                                                                                                
According to our sample policy, we make samples as per the buyer's requirement. As we know, we have different customer levels, some of them need Non-EMC version for cost down situation, and some of them need EMC version for high compatibility situation. If the buyer did not state clearly about the EMC requirement when requesting a sample, we will randomly to make NON-EMC version for testing.
So, what is the most important? We kindly suggest that the buyer would better to clearly required EMC or NON-EMC in the sample procedure and must talk to our salesperson.

In case of failure, a new sample of EMC version will be provided again, if the buyer did not state in sample process, then the buyer pay the 2nd express freight, if KRECO made the wrong samples by NON-EMC version instead of EMC version, we will definitely pay the 2nd part of express freight.


 
38: Is that necessary to make all samples by EMC version?
                                                                                                                
We suggest that it is not definitely necessary, because of different marketing needs.
It depends on your product compatibility and cost effects.

TIPS:
Note: Max output voltage for all AC/DC adapter,AC/AC adapter transformer is below and euqal to 24V,
Max output voltage for all switching power supply or LED power supply is less than and equal to 48V.

Due to we have changed our technical issues very quickly, for the up to date technology information, we suggest you that to contact our salesperson,
or email directly to: sales@kreco.com.cn for inquiry.

 
  

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