1.Reason :

Recently, due to the popularity of electronic and computer product, as well as the increase awareness of environmental protection issue, therefore it has been listed as an improvement item.

Normally power source （exclude battery） for electronic and computer product comes through from public utility power system. Its power source's circuitry structure is using diode rectifier, filter then pass through current transformation circuitry, as shown in figure 1, even though this method will make the voltage waveform becomes positive waveform rectifying diode and filtering capacitor, the rectifying diode short at the instant where the AC voltage is higher than the voltage on the filtering capacitor, causing intermittent current flow which result in an impulse waveform effect, this is the reason why harmonic current and power factor are below （usually 0.6 to 0.7）.

Figure 1. Full Bridge Diode Rectifier Circuitry and its Voltage and Current Waveform.

Above result and ideal non-harmonic current （power factor of 1.0） has an apparent difference, it cause the efficiency of power consumption to be lower. For example in table 1, usual power supply has a power factor of 0.65 when obtaining power from public utility power system with 1440 VA capacity, it can load up to maximum power of 702W. However, for the power supply with PFC function, it can reach up to power factor of 0.99 with load up to maximum power of 1015W.

European CE mark has already require product with power consumption more than 300W （will be reduce in the future） to meet their harmonic current limit requirement, that means the power factor has to increase （about > 0.95） in order to meet CE requirement before a product can be market to Europe. Right now, countries other than one in Europe, are planning to put these requirements into the law. Because of that, reducing power source harmonic current, increase power factor is a global environmental protection trend.

 Table 1. Typical Power Supply Input Circuitry and Waveform

Table 1 compare between power supply using traditional rectifier circuitry and PFC correction circuitry. In a traditional 15 A/120 V public power circuit, UL require that under 15 A circuit breaker capacity, its continues rms current value must be lower than 12 A, so to meet UL safety requirement. That means there is only 1440 VA usable capacity, but consider typical energy transformation efficiency and poor power factor, there is only 702 W of power can be given to load, （1440*0.75*0.65=702 W）. However, for the power supply with PFC front-end circuitry, it can improve to 1015 W of power transferable to load.

2. Application :

Traditional electrical product like motor with inductance, its power factor increase depends on connecting parallel capacitor to shows resistance on the load, it also increases performance. However nowadays, electronic and computer product belongs to rectifying type load, its current waveform does not like inductive type load remains like sine wave, it has an impulse waveform, therefore it cannot just rely on parallel capacitor to improve the power factor.

Actually, to increase power factor for rectifying type loading electronic and computer product, there are passive and active type power factor correction.

Passive type use inductor （figure 2）, capacitor （figure 3） circuitry to reduce harmonic current, because power source frequency is 50 Hz or 60 Hz low frequency, it needs large inductor and capacitor, also the power factor improvement is not as good, limited improvement result, that is why it is rarely use.

Figure 2 input terminal inductance working frequency is power source frequency (50 Hz/60 Hz), due to the fact that inductor can soften the current sudden change, therefore the input current waveform will be smoother. Figure 3 is using partly smoothen circuitry structure, to improve power factor. Its theory is extending the period where the voltage of the power source is higher than output voltage range, according to diode turn on condition, input current waveform will become smoother.

Figure 2 : Passive type filtering inductor power factor correction circuit

Figure 3 : adding partly smoothen capacitor's power factor correction circuit

Active type power factor correction using active component (control circuit and power sine conductor ON/OFF switch) as shown in figure 4.

figure 4（a） BUCK structure

figure 4（b） BOOST structure

figure 4（c）FLYBACK structure

Its fundamental working theory is to adjust input current waveform to looks like input voltage waveform, this can reach the point where power factor of 1 goal. Right now there are several chip manufacturer offer PFC control IC, just need to add few parts like power Mosfet, inductor and few other little component to make a active power factor regulator, such as figure 4（b） BOOST structure power factor correction as voltage step up type, that is input voltage range can be 90 Vac to 264 Vac without additional switch for choosing the voltage range. To have a universal voltage model, this power factor regulator is a very important additional value, and this power factor regulator output of 380 Vdc has a 10 Vp-p and 50 Hz/60 Hz harmonic & high frequency noise.

Power supply with PFC included as shown in Figure 5 and Figure 6.

Figure 5 PFC Block

Figure 6 PFC Circuit

3. Testing Technique :

1. When examine power supply with PFC included (Figure 5), need to do a few test on the input and output. These include input line regulation of PFC: When input voltage change, the rate of change to input power factor. Output load regulation of PFC: When load current change, the rate of change to input power factor. Combine regulation of PFC: When input voltage and output load change at the same time, the rate of change to input power factor.
   
   
2. Above input voltage change can use auto-transformer or AC power source to change input voltage to simulate possible actual change, for example 90 V to 115 C to 132 V or 180 V to 230 V to 264 V or 90 V to 115 V to 264 V or 90 V to 230 V to 264 V different voltage combination.
   
   
3. Input power measurement require accurate power meter, such as GW Instek GPM-8310/8320/8330 accurate power meter, this meter need to have consistent accuracy within 90 V to 264 V voltage range in order to have a trustful result under different input current.
   
   
4. On output load, one can use DC electronic load to simulate different load conditions.
   
   
5. Above is using adjustable power source for testing, to examine PFC function. That is indirect examine method, because when load change, it is going through Figure 5(b) switching regulator, if the switching regulator experiences any abnormal conditions, this will affect the examine result on Figure 5(a) PFC Block. This testing method is more suitable in testing the final product in production line.
   
   
6. Therefore we are going to introduce another testing method. Take out the PFC section as shown in figure 6 and do the test individually on it. Now we use 500 V/600 V high voltage electronic load to simulate Figure 5(b) switching regulator and DC output current, so we can more accurately examine the power factor regulator with input voltage, output load and combination input power factor correction rate. Now we only need use a high voltage electronic load (like model 3314F/G, 3319G/3319G-M, 3360F/PEL-5000G/PEL/5000C product), then we can examine the function of the power factor regulator and do test directly. This testing method is suitable for R&D to verify on PFC function and testing; it is also suitable for production to test on PFC section.

4. Testing Technique:

Prodigit Electronic always devoted to developing of power electric testing equipment, we have the best and complete solution in all necessary equipment for PFC testing: Accurate digital power meter and high voltage 500 V/600 V electronic load.

GW Instek accurate digital power meter model GPM8310/8320/8330 series simultaneously digitally sampling the voltage and current waveform, according to RMS, watt and PF theory, using microprocessor to compute 0.1% accuracy's RMS voltage, current watt and < 0.1 % accuracy's power factor, it is highly accurate and consistent under the widest voltage and current range, this is the most accurate and reasonable price's power meter in the market.

High voltage 500 V/600 V electronic load model 3314F/G, 3319G/3319G-M, 3360F/PEL-5000G/PEL-5000V series is specially designing 500 V/600 V electronic load for PFC output testing, 3314F/G is design for 300 W or below, 3319G/331pG-M is specially design for 800 W or below, and PEL-5000G/PEL-5000C is for up to 24 kW testing load.

Above high voltage electronic load has constant current and constant resistant mode, has voltage, current, power and VA meter, allow you easily read PFC's output voltage, current, power, and then compare with the input measure by the digitizing power meter, this way the PFC efficiency can be calculate.

Above PFC testing equipment are used by several power supply manufacturer with good result, please contact company sales if you have any need of this equipment.

※ PRODIGIT is a sub-brand of GW Instek.

Because low voltage power supply will be more popular in the future, for example 3.3 V or 2.2 V, it can reduce the power dissipate or heat problem in the Advance IC, such as CPU. For example, change the operating voltage from 5 V to 3.3 V with same current, it can reduce about 34 % heat dissipate in IC; where the heat is the major problem in a compact size computer, such as notebook PC.

To solve the low output voltage power supply testing requirement, all Prodigit Electronic Load can be used for 3.3 V,2.2 V or even 1.7 V output voltage. The following table shows the Prodigit 3310F/G series Electronic Load typical working voltage on half and full load current.

Note :

The ≦ 80 V models typical factory set Load ON Voltage is 1 V, 250 V modes set to 2 V and 500 V models set to 4 V when shipment however, the Load ON Voltage can be adjusted from 0 V to 3 V for Input Voltage ≦ 80 V models, or from 0 V to 5 V for input Voltage > 80 V models.

※ PRODIGIT is a sub-brand of GW Instek.

1.Quick Start guide for e-Load

  WARNING Risk of electric shock.

• The DC LOAD conforms to IEC Safety Class I (equipment that has a Protective Con-doctor terminal). Be sure to earth ground the product to Prevent electric Shock.
• The DC LOAD is grounded through the power cord ground wire.
• Connect the protective conductor terminal to earth ground.

1.1.  Installation and Preparation

1. Turn the POWER switch off.
2. Check that the AC power line meets the nominal input rating of the DC LOAD.
3. Connect the power cord to the AC INPUT.
4. Check that the power cord is connected correctly.
5. Connect the power cord plug to a properly grounded outlet.

1.2. Checking Whether the Power Is On or Off

1. Check that the power cord is connected correctly.
2. Check that nothing is connected to the DC INPUT (load input) terminals on the rear panels.
3. Turn the POWER switch on.
4. If you notice strange sounds, unusual odors, fire, or smoke around or from inside the DC Load, turn the POWER switch off, or remove the power cord plug from the outlet.
5. Press the side of the POWER switch to turn the power off.

1.3. Connecting to the DUT

 CAUTION  Risk of damage 

• Do not connect the DUT to the load input terminals while the product’s load is turned on.
• Do not invert the polarity when connecting. An overcurrent might flow when the load is turned on.
• To avoid overheating, observe the following precaution.
• Use the supplied screws to connect the cables with crimping terminals.

1.4. Connecting to the load input terminals on the rear panel

  WARNING  Risk of electric shock

Be sure to attach the cover for the load input terminals on the rear panel.

1. Turn the load off.
2. Turn off the output of the DUT.
3. Connect the DUT to the load input terminals on the rear panel.
4. Connect the load cables to the load input terminals on the rear panel using the included load input terminal screw set.
5. Do not invert the polarity when connecting.
6. Connect the positive (+) input terminal on the load generator to the high Potential output of the DUT & Load unit, and connect the negative (-) polarity input terminal on the load generator to the low Potential output of the DUT & Load unit.
7. This completes the connections.

Note :

During voltage calibration, due to the input impedance and Snubber circuit, do not directly input the DC Standard to the DC Load Input terminal.

1.5. Wire/Cable Guide

The following table provides a guide to the current carrying capability (ampacity) of Both Metric and AWG sizes. Metric sizes are expressed as a cross sectional areas (CSA). If in any doubt of a cables ampacity it is recommended that you ask your Cable supplier.

1.6. Power ON / Off the Load and DUT

Power ON Sequence 

1. Turn the POWER switch on the Load.
2. Turn the POWER switch on the DUT.
   
   

Power OFF Sequence

1. Turn the POWER switch off the DUT.
2. Turn the POWER switch off the Load.

2. Electronic Load testing connection

When the Current/Watt rating exceeds the Plug-in unit rating. Two or more Plug-in units may be parallelled to increase the power rating. Different electronic load modules （such as a 3310F and a 3310G） may be parallelled together. Delete short key of Electronic Load is recommended for parallel operation

Prodigit strongly advises against series wiring of Electronic Loads.

3. Vsense and Imonitor connection

Due to the large changes of load current will cause a voltage drop on the conductor, the Vsense input BNC is designed to compensate this condition. Prodigit 3310F/G series Electronic Loads are equipped with Auto-Vsense capability. The DVM will measure Load input binding post when Vsense BNC to clip cable is not used. The DVM will measure the power supply output terminal voltage when Vsense cable is used, the connection diagram is shown below :

Imonitor BNC output is used to monitor the load current flow through the Electronic Load, Imonitor output is 10V F.S for Prodigit 3310F/G series, it is normally connected to an oscilloscope for dynamic current wave form monitor.

Note :

The Imonitor of the 3310F/G series is not isolated. When testing two sets of power supplies (positive and negative) and simultaneously observing the load current waveforms of the two sets, connect two Imonitors to Ch1 and Ch2 of the oscilloscope at the same time. Since the input section of a typical oscilloscope does not have an isolation device, if the Imonitor output is not isolated after connection, it will cause a short circuit in the power supply device under test and make it impossible to measure simultaneously.

4. Multiple output (both +/-) power supply testing connection

There is a rule for connection between a multiple output power supply and a multi-channel Electronic Load: Rule: The potential of Electronic Load's positive input (Red binding post) must be higher than the Negative input（black binding post）

The above example shows a four output power supply connects to four channel Electronic Load.

※ PRODIGIT is a sub-brand of GW Instek.

Prodigit provides a very flexible range of Plug-in Electronic Load module and Mainframe to meet your testing requirements.
Plug-in Electronic Load units have power rating from 75 W to 300 W.

Modules are installed from the front of the mainframe.
The 3310F/G series has CC, CR, CV, CP, dynamic and short modes, it is most commonly used for R&D, Quality control, and ATE systems. Voltage/Current and Wattage ratings for the 3310F/G series modules are shown in the specification chart below.

Determine power requirements in watts and use the above table to determine which module(s) is (are) required. For example: a 12V 20A power supply would require a 300 W module. A dual output power supply would require two modules.

The lower current rating in the 3310F and 3310G series Electronic Loads provides higher programming resolution and minimizes load noise effects to a power supply. Load noise order figures are listed below :

Selecting the proper mainframe :

For single load applications select Prodigit's 3302F/G Mainframe. This mainframe accepts all 3310F and 3310G series under 400 W plug-in modules. For 3317G-M/3319G-M 800 W modules need to selecting two or four slot mainframe. For two or more loads requiring dynamic load testing, the 3305F/G(two slot) and 3300F/G(4 slot) mainframe should be selected.

Note :

3317G and 3319G are standalone models, there are included load mainframe. The 330XF/G Mainframe has optional GPIB+RS232C, GPIB, RS-232, USB and LAN interface with Listen/Talk capability. The 330XF/G Mainframe accepts all 3310F/G series Electronic Load Plug-in units with communication interface. The remote function is Listen/Talk for 3310F/G series Plug-in units.

 (a) 3300F/G Mainframe GPIB programming

330XF/G Mainframe GPIB programming

All 3310F/G series Electronic Load module can be loaded into a 330XF/G mainframe in any combination. GPIB : LISTEN/TALK Capability.

 (b) 3300F/G Mainframe RS232C programming

330XF/G Mainframe RS232C programming

All 3310F/G series Electronic Load module can be loaded into a 330XF/G mainframe in any combination. RS232C : SETTING/READ BACK Capability. 330XF/G Mainframe RS232C programming All 3310F/G series Electronic Load module.

 (c) 3302F/G Mainframe GPIB programming

330XF/G Mainframe GPIB programming

All 3310F and 3310G series Electronic Load modules can be put into the 330XF/G mainframe.

Note :

The GPIB card suppliers below meet Prodigit's GPIB protocol requirements. : 

1. National Instrument (U.S.A).
2. Keysight (U.S.A.)
3. ADlink (TAIWAN).
4. CONTEC (JAPAN).
5. ines Test and Measurement GmbH & Co. KG (GERMANY)

※ PRODIGIT is a sub-brand of GW Instek.

The constant current and constant resistance modes are used in conjunction for testing switching power supplies.

Caution must be exercised when using the CC mode in test set up, for example: A 5V/50A output power supply can not deliver 50A over its start up range 0-5 volts. In many cases the power supply short circuit or over current protection circuit will shut the power supply down. What is occurring is that the power supply is trying to deliver 50A at 2V because the load tester is in the CC mode. The power supply is designed not to do this.

As a result, when testing a power supply, the CR mode should be used to allow the power supply voltage and current to ramp up together. After this has occurred the CC mode should be used to complete testing. Prodigit has eliminated the need for manually switching from the CR to the CC mode with their 3310 and 3320 series Electronic Loads. They can be programmed with proper current and slew rate in the CC mode which allows a power supply to reach its specified output condition in the CC load mode.

• Figure（a） is the AC line voltage to the switching power supply.
• Figure（b） is the power supply's output voltage. Output voltage starts to come up at t0, and reaches its final stable voltage at t1.
• Figure（c） shows the load current of the unit under test when an Electronic Load is in the CR mode.
• Figure（d） shows the same load current when a Load is in the CC mode. Note that the unit under test has to deliver more power from t0 to t1 in the CC mode.
• Figure（e） is load current using Prodigit's 3310 and 3320 series Electronic Loads.

Due to the End-of-Life (EOL) notice from our component supplier, the power switch for PSW-Series has been updated. This change specifically pertains to the mechanical operation and appearance of the power switch, as detailed below:

• Switch Functionality: The original power switch used in PSW-Series featured a relay-trip (hardware trip-off) function. Following the supplier's discontinuation notice, our engineering team initiated a second-source design transition. Since there is no direct drop-in replacement with the same trip function currently available, the new switch provides standard ON/OFF operation only.
  Note: While the User Manual was updated in September 2024 to reflect this change, some units manufactured in late 2025 may still be equipped with the original relay-trip switch due to a postponement in the supplier's final production cutoff.

• Specifications and Programming: There are no changes to the electrical specifications or the SCPI command set. All performance parameters remain fully consistent with the previous version.

• Protection Features: All core protection mechanisms, including OCP (Over-Current Protection), OVP (Over-Voltage Protection), and OPP (Over-Power Protection), remain fully functional.

• Physical Appearance and Operation:
  1. The power switch color is now Black.
  2. The hardware-controlled trip function has been removed (refer to the illustration below for visual comparison).

We appreciate your continued trust and support of GW Instek products.

GRA-451-E (EIA) for ASR-6000 series (standard)

GRA-451-J (JIS) for ASR-6000 series (optional)

ASR-003 GPIB interface card

ASR-004 Device Net interface card

ASR-005 CAN BUS interface card

ASR-006 External parallel cable

ASR-006 Parallel cable	ASR-003 GPIB interface
ASR-004 DeviceNet interface	ASR-005 CAN Bus interface

Testing fuses and circuit breakers requires transient current to test whether the operation is normal.

• It is a design issue when a circuit breaker fails to disconnect.

• It is a quality issue when a circuit breaker disconnects abnormally.

GW Instek electronic loads with turbo mode can help users verify these two issues at the most appropriate cost.

Turbo mode can provide double the rated current or power for a short period of time (1 second).

Electronic loads with turbo mode include:

• GW Instek brand: The AEL-5000 series
• Prodigit brand: The 3310G series, the 3350G series, the 3270 series, and the 3282 series

Other applications of turbo mode: AC power short circuit, OCP and OPP tests

More Porduct information: DC Electronic Load

The DC mode of the AC power supply does not have the constant current (CC) output of the DC power supply.

The DC mode of the AC power supply can only provide constant voltage (CV) output. When the DC power supply is overloaded, it will become a constant current (CC) output. When the DC mode of the AC power supply is overloaded, the output will stop.

The power supply overvoltage protection (OVP) is designed to protect the device under test (DUT) or the circuit under test (DUC) from excessive voltage.

Three possible overvoltage (OVP) scenarios are provided below.

Scenario 1: Users forgot that the over-voltage protection was set in the last project, and the voltage of this test project is higher than the over-voltage protection setting value.

For example: the OVP of the last project was set to 12.5V, and the required voltage for this project is 15V. The set output voltage is higher than the over-voltage protection of 12.5V, so the power supply starts the protection mechanism to stop output.

Scenario 2: After remote compensation is connected, the output of the power supply exceeds the overvoltage protection setting value due to compensation.

For example: the working voltage of the circuit is 12V, and the overvoltage protection is set to 12.5V. Due to excessive wire loss, a voltage drop of 0.6V is caused on the wire, resulting in the voltage of the DUT being only 11.4V. The power supply starts to compensate. After compensation to 12.5V, the DUT is 11.9V. After further compensation, it exceeds the overvoltage setting value of 12.5V, so the power supply activates the protection mechanism to stop output.

Scenario 3: Due to the inductance of the test wire, at the moment when the power supply is switched on or off or when the programmable voltage changes, the stray components on the wire cause LC resonance, leading the transient voltage of voltage change to exceed the OVP protection voltage setting value.

During production line testing, the programmable DC power supply provides voltage, current, and test time. These three programmable variables allow the complex production line testing process to be automated. However, if you want to further improve the test productivity after automation, you must understand the design and special features of the programmable power supply.

First we need to understand the output characteristics and load effect of the DC power supply.

In order to provide a stable DC output, the DC power supply has a capacitor on the output to perform filtering operation. The capacitor does not allow the voltage to change instantaneously, so when you want the voltage output to change, the DC output filter capacitor will cause this change time application in dilemma. The smaller the output ripple is, the slower the reaction speed to voltage changes is.

The output voltage should become larger: faster when there is no load and slower when there is a load. A life case: A car full of passengers and a car without any passengers climb a hill. Under the same accelerator conditions, the latter climbs faster and the former climbs slower.

The output voltage should become smaller: slower when there is no load and faster when there is a load. A life case: A car full of passengers and a car without any passengers go downhill. When the accelerator is not stepped on, the latter goes downhill slowly, but the former goes downhill quickly. When the power supply provides the bleeder resistor function, the bleeder resistor can be used to increase the time for the voltage to decrease.

If the power supply needs to perform rapid voltage changes (100u second level), it can be achieved by using the DC mode of the AC power supply, such as GW Instek's ASR-2000 series and ASR-3000 series AC/DC dual-purpose power supplies.

If rapid changes in current are required, an electronic load can be used to draw the source to force the power supply to provide rapid current.

In addition to the above issues, the hardware setting time and the computer control interface adopted (GPIB, RS-232, USB, LAN) will all affect the programmable voltage change time.

More Porduct information: AC/DC Power Supply

Step 1:

Check whether the AC input of the power supply is normal? Is it because the power plug strip controlled by a switch was not turned on or was turned off by a colleague without noticing. Check whether the display on the power supply shows anything. If not, check whether the fuse of the power supply is burned out.

Step 2:

After confirming that the power input is normal, set the output voltage and current of the power supply. The two cannot be 0 (especially note that the current cannot be 0). If you find that the set value cannot be displayed, some models of GW Instek provide a key lock function to ensure that the set value is not accidentally changed during the test.

Please confirm whether the model you are using has this function. If so, please confirm the Key Lock light is off. If the Key Lock light is on, please unlock it first. If it still cannot be set, please confirm whether the power supply is connected to the computer. If the computer is connected, the remote control mode will cancel the local operation.

Step 3:

If the power supply has an output control switch, please press on. If the power supply has an output control switch, there will usually be a light indicating that the output is on.

Step 4:

If the output control switch is turned on but the light does not light up (the light may be faulty, but the power supply still has output), please use a multimeter with a voltage range to measure the output of the power supply. Several power supplies from GW Instek have an on/off delay timer function. Please also pay attention to whether there is a time delay in the output due to this function being turned on.

If after following the above steps, the power supply still has no output, please contact your nearest GW Instek Service Center to arrange for the instrument to be sent for repair.

Service Support

• Email: services@goodwill.com.tw

More Porduct information: DC Power Supply