The application of switching power supply is becoming more and more extensive. How to understand the intrinsic quality of switching power supply during the purchase process? Which of the 9 extreme tests must be passed? The following are introduced one by one:

1. Repeated short circuit test

test introduction

Short-circuit the output of the module under various input and output states, the module should be able to achieve protection or retraction, and short-circuit repeatedly for many times. After the fault is eliminated, the module should automatically resume normal operation.

testing method

a. No-load to short-circuit: within the full range of the input voltage, when the module is switched from no-load to short-circuit, the module should be able to achieve output current limiting or retraction normally. After the short-circuit is removed, the module should be able to resume normal operation. Let the module work repeatedly from no-load to short-circuit, the short-circuit time is 1s, the release time is 1s, and the duration is 2 hours. After this, the short circuit is released to judge whether the module can work normally.

b. Full load to short circuit: In the full range of the input voltage, the module should be able to achieve output current limiting or retraction from full load to short circuit. After the short circuit is removed, the module should be able to resume normal operation. Let the module go from full load to short circuit and remain short circuit for 2 hours. Then release the short circuit to determine whether the module can work normally.

c. Short-circuit power-on: short-circuit the output of the module first, then power on, and then power on within the input voltage range of the module. The module should be able to achieve normal current limiting or retraction. After the short-circuit fault is eliminated, the module should be able to resume normal work. After repeating the above test 10 times, let the short circuit open to judge whether the module can work normally.

judgement standard

After the above test, the power supply module can work normally when it is turned on; the case is checked, and there is no abnormality in the circuit board and other parts (such as whether the input relay is electrocuted during the short-circuit process, etc.), and it is qualified; otherwise, it is not qualified.

2. Repeated switch test

test introduction

When the output of the power module is under the maximum load, the input voltage is 220v, (input overvoltage point -5v) and (input undervoltage point +5v), the input is repeatedly switched on and off, and the performance of the power module is tested repeatedly.

testing method

a. The input voltage is 220v, the power module can quickly bring the maximum load, use the contactor to control the voltage input, close for 15s, disconnect for 5s (or you can use ac source for simulation), run continuously for 2 hours, the power module should be able to work normally;

b. The input voltage is -5v at the overvoltage point, the power module has the maximum load, use the contactor to control the voltage input, close for 15s, disconnect for 5s (or you can use ac source for simulation), run continuously for 2 hours, the power module should be normal Work;

c. The input voltage is the undervoltage point -5v, the power module has the maximum load, use the contactor to control the voltage input, close for 15s, disconnect for 5s (or you can use ac source for simulation), run continuously for 2 hours, the power module should be normal Work.

judgement standard

In the above test, the power module works normally, and the power module can work normally after the test, and the performance has no obvious change, which is qualified; otherwise it is unqualified.

3. Input low pressure point cycle test

test introduction

The setting hysteresis of the input undervoltage point protection of the primary power supply module often occurs in the following situations: the input voltage is low, close to the undervoltage point of the primary power supply module, and the power supply module is turned off. The voltage will rise after the power failure, which may cause the primary power module to be in a state of repeated development at low voltage.

testing method

The power module runs with full load, the input voltage changes slowly from (input undervoltage point -3v) to (input undervoltage point +3v), the time is set to 5 to 8 minutes, and the power supply module should be able to work normally and stably, continuously running For at least 0.5 hours, the performance of the power module has no significant change.

judgement standard

The primary power module runs normally and continuously, and the performance does not change significantly after at least 0.5 hours, and it is qualified; otherwise, it is unqualified.

4. Input transient high voltage test

test introduction

The pfc circuit uses the average value circuit for over-voltage protection, so when the input transient high voltage, the pfc circuit may achieve protection quickly, resulting in damage, test the stable operation ability of the power module under transient conditions to evaluate the reliability .

testing method

a. For rated voltage input, use a dual trace oscilloscope to test the input voltage waveform and the overvoltage protection signal, the input voltage jumps from the power limit point plus 5v to 300v, read the number of cycles n before overvoltage protection from the oscilloscope, and use it as the following basis for the test.

b. Rated input voltage, the power module runs with full load, superimpose 300v voltage jump on the input, the number of superimposed cycles is (n-1), the superposition frequency is 1 time/30s, and the operation is 3 hours in total.

judgement standard

If the primary power module can run stably under the above conditions without damage or other abnormal phenomena, it is qualified; otherwise, it is unqualified.

5. Input voltage drop and output dynamic load

test introduction

During the actual use of the primary module, when the input voltage drops, the limit condition of the sudden load on the power module may occur. At this time, the power devices and magnetic components work in the maximum transient current state, and the test can check the control sequence and current limit. The rationality of circuit and software design for protection.

testing method

a. Adjust the input voltage to jump between the undervoltage point +5v (duration is 5s) and the overvoltage point -5v (duration is 5s), and the output is adjusted to the maximum load (maximum rated capacity, duration is 500ms) , jump between no-load (duration is 500ms), run for 1 hour;

b. Adjust the input voltage to jump between the undervoltage point +5v (duration is 5s), the overvoltage point -5v (duration is 5s), and the output is adjusted to the maximum load (maximum rated capacity, duration is 1s), Jump between no-load (duration is 500ms), run for 1 hour.

judgement standard

Under the above conditions, it should be able to operate stably without damage or other abnormal phenomena, and it is qualified; otherwise, it is not qualified. In the event of damage, record the failure problem to provide a basis for analyzing the cause of the damage.

6. High-pressure no-load, low-pressure current-limiting operation test

test introduction

High-voltage no-load operation is the loss of the test module, especially the module with soft switching technology. Under no-load condition, the soft switch becomes hard switch, and the loss of the module increases accordingly. The low-voltage full-load operation is to test the loss of the module when the module is at the maximum input current. Under normal conditions, the module has the lowest efficiency when the module is in low-voltage input and full-load output, and the module generates the most serious heat at this time.

testing method

a. Adjust the input voltage of the module to the input overvoltage protection point -3v, and the output of the module is the lowest output voltage, no-load operation, at this time, the duty cycle of the module is the smallest, and the module should not be damaged after continuous operation for 2 hours;

b. Adjust the input voltage of the module to the undervoltage point +3v, and the output of the module is the inflection point state of the highest output voltage. At this time, the duty cycle of the module is the largest, and the module should not be damaged after continuous operation for 2 hours;

c. Adjust the input voltage of the module to the input voltage when the efficiency is the lowest point, the module output is the inflection point state of the highest output voltage, and run continuously for 2 hours, the module should not be damaged;

d. Adjust the input voltage of the module to the overvoltage point of -3v, and the output of the module is the inflection point state of the highest output voltage. At this time, the duty cycle of the module is the largest, and the module should not be damaged after continuous operation for 2 hours;

e. Adjust the input voltage of the module to the input voltage when the efficiency is the lowest point, and the module output is the inflection point state of the highest output voltage, and the module should not be damaged after continuous operation for 2 hours.

Note: The above tests must be carried out at the maximum operating temperature specified in the specification.

judgement standard

Working under the above conditions, the module is not damaged, it is qualified; otherwise it is unqualified.

7. Power supply special waveform test

test introduction

Verify the power module's ability to operate stably in the presence of spikes, glitches and harmonics that may be formed by grid waveform distortion. The following waveforms must be input for testing:

(1) Glitch input test waveform

The glitch of the power grid is the most common waveform in the power grid. There is no limit to the size and amplitude of the glitch. Generally, through the oscillation wave input test and the ringing input waveform, the glitch input in the power grid can basically be simulated. Do the following glitch input test

Features: The peak of the power grid has overshoot and will drop to 0v. The pulse width of overshoot and drop is very narrow, generally not greater than 100ms, and the overshoot amplitude is generally not more than 100v. The phase drop is not limited to the peak point, it can happen at any phase. This kind of waveform is very common in the real power grid, and opening any switch will cause this phenomenon.

(2) Voltage clipping waveform input

This waveform is also very common in power grids and is characterized by the fact that the power grid suddenly drops from an indeterminate phase to 0v, and then does not recover until the next half-wave begins. In iec1004-4-11, the drop of the waveform starts from more than half a cycle, but there are still many similar waveforms with a drop time less than half a cycle in the actual power grid. It is required during the test that the input voltage waveform starts to drop from 90 degrees, drops for 1/4 cycle, and works for 2 hours for a long time.

(3) The half wave head of the power grid rises sharply to double the voltage. This waveform is mainly used to simulate the resonance overvoltage that will suddenly appear in the actual power grid, and in this case, the input overvoltage protection circuit of the module does not work. , this shock is dangerous for circuits with pfc. Test content: a. When the input voltage is 180v and the output is fully loaded, use the ac source to simulate the waveform, requiring 180v to work for 3 minutes, then the voltage suddenly increases to 380v for 100ms, and then returns to 180v, so that the module is in this state. In case of working for 1 hour for a long time, it should not be damaged; b. Set the ac source so that the input voltage is 0v for 5 minutes, then the voltage suddenly increases to 380v for 100ms, and then returns to 0v, so that the module can be long in this case Time to work for 1 hour and should not be damaged.

testing method

Use the ac source to supply power to the module, and the module will output at full load; use the ac source to simulate the input of spikes, glitches and harmonic voltages, each special voltage input works for 2 hours, and measure the input current and output voltage. The module should be able to run stably. During the test, pay attention to the x capacitor, auxiliary power supply, soft-start resistor and other possible problems.

judgement standard

In practice, it can run stably in the case of sharp spikes, burrs, and harmonic voltages, without damage, and it is qualified; otherwise, it is unqualified.

8. Active pfc performance test

test introduction

Power modules with active pfc are sensitive to grid spikes, glitches and harmonics, and should be thoroughly and carefully tested.

testing method

Use ac source as the input voltage source, output with half load and full load respectively, test the input current waveform and voltage waveform, and monitor the voltage after pfc; Phase and amplitude relationship; measure the current and voltage of the pfc switch tube to verify the safety of the switch tube and other power devices and the ability of current to track voltage changes in the full voltage range and in the case of glitches, spikes, harmonics, etc.

judgement standard

The pfc test can be used as a reference for reliability. When serious problems occur, they should be solved in time.

9. Operating voltage test

test introduction

There are various operating overvoltages in the power grid, among which the most common is no-load line closing overvoltage, which is also a great threat to the module. This test is to verify the module's ability to resist operating overvoltage.

testing method

The simulation of the overvoltage line is very simple, the principle is as follows:

The parameter of the inductance is 10mh (for reference: in the module test method of ees, there is no grounding capacitor, the input resistance is connected in series with the inductance, the resistance value is 0 ohm, the inductance is 8mh, and the resistance is 79 ohms and the inductance is 10mh. ), the capacitance is 16.7uf, and the test waveform is as follows (not shown).

Connect the device under test to both ends of the capacitor, and at the moment of closing k, an overvoltage will be generated at both ends of the capacitor, which is used to simulate the degree of damage to the device caused by the overvoltage during the power-on process. As a limit test item, the input is connected to the l and n lines, the device to be tested is connected to both ends of the capacitor, the machine is switched on and off frequently, the repetition frequency is 1 time/5 minutes, and the continuous test is 5 hours. For three-phase input equipment, the input is connected to the l and l lines, and the device under test is connected to both ends of the capacitor. The repetition frequency is 1 time/5 minutes, and the continuous test is 2 hours.

judgement standard

In the test process, if there is short-term function decline or performance degradation, but it can be automatically recovered, it is qualified; but if the performance is permanently deteriorated or requires manual intervention to recover, it is not qualified.

The application of switching power supply is becoming more and more extensive. How to understand the intrinsic quality of switching power supply during the purchase process? Which of the 9 extreme tests must be passed? The following are introduced one by one:

1. Repeated short circuit test

test introduction

Short-circuit the output of the module under various input and output states, the module should be able to achieve protection or retraction, and short-circuit repeatedly for many times. After the fault is eliminated, the module should automatically resume normal operation.

testing method

a. No-load to short-circuit: within the full range of the input voltage, when the module is switched from no-load to short-circuit, the module should be able to achieve output current limiting or retraction normally. After the short-circuit is removed, the module should be able to resume normal operation. Let the module work repeatedly from no-load to short-circuit, the short-circuit time is 1s, the release time is 1s, and the duration is 2 hours. After this, the short circuit is released to judge whether the module can work normally.

b. Full load to short circuit: In the full range of the input voltage, the module should be able to achieve output current limiting or retraction from full load to short circuit. After the short circuit is removed, the module should be able to resume normal operation. Let the module go from full load to short circuit and remain short circuit for 2 hours. Then release the short circuit to determine whether the module can work normally.

c. Short-circuit power-on: short-circuit the output of the module first, then power on, and then power on within the input voltage range of the module. The module should be able to achieve normal current limiting or retraction. After the short-circuit fault is eliminated, the module should be able to resume normal work. After repeating the above test 10 times, let the short circuit open to judge whether the module can work normally.

judgement standard

After the above test, the power supply module can work normally when it is turned on; the case is checked, and there is no abnormality in the circuit board and other parts (such as whether the input relay is electrocuted during the short-circuit process, etc.), and it is qualified; otherwise, it is not qualified.

2. Repeated switch test

test introduction

When the output of the power module is under the maximum load, the input voltage is 220v, (input overvoltage point -5v) and (input undervoltage point +5v), the input is repeatedly switched on and off, and the performance of the power module is tested repeatedly.

testing method

a. The input voltage is 220v, the power module can quickly bring the maximum load, use the contactor to control the voltage input, close for 15s, disconnect for 5s (or you can use ac source for simulation), run continuously for 2 hours, the power module should be able to work normally;

b. The input voltage is -5v at the overvoltage point, the power module has the maximum load, use the contactor to control the voltage input, close for 15s, disconnect for 5s (or you can use ac source for simulation), run continuously for 2 hours, the power module should be normal Work;

c. The input voltage is the undervoltage point -5v, the power module has the maximum load, use the contactor to control the voltage input, close for 15s, disconnect for 5s (or you can use ac source for simulation), run continuously for 2 hours, the power module should be normal Work.

judgement standard

In the above test, the power module works normally, and the power module can work normally after the test, and the performance has no obvious change, which is qualified; otherwise it is unqualified.

3. Input low pressure point cycle test

test introduction

The setting hysteresis of the input undervoltage point protection of the primary power supply module often occurs in the following situations: the input voltage is low, close to the undervoltage point of the primary power supply module, and the power supply module is turned off. The voltage will rise after the power failure, which may cause the primary power module to be in a state of repeated development at low voltage.

testing method

The power module runs with full load, the input voltage changes slowly from (input undervoltage point -3v) to (input undervoltage point +3v), the time is set to 5 to 8 minutes, and the power supply module should be able to work normally and stably, continuously running For at least 0.5 hours, the performance of the power module has no significant change.

judgement standard

The primary power module runs normally and continuously, and the performance does not change significantly after at least 0.5 hours, and it is qualified; otherwise, it is unqualified.

4. Input transient high voltage test

test introduction

The pfc circuit uses the average value circuit for over-voltage protection, so when the input transient high voltage, the pfc circuit may achieve protection quickly, resulting in damage, test the stable operation ability of the power module under transient conditions to evaluate the reliability .

testing method

a. For rated voltage input, use a dual trace oscilloscope to test the input voltage waveform and the overvoltage protection signal, the input voltage jumps from the power limit point plus 5v to 300v, read the number of cycles n before overvoltage protection from the oscilloscope, and use it as the following basis for the test.

b. Rated input voltage, the power module runs with full load, superimpose 300v voltage jump on the input, the number of superimposed cycles is (n-1), the superposition frequency is 1 time/30s, and the operation is 3 hours in total.

judgement standard

If the primary power module can run stably under the above conditions without damage or other abnormal phenomena, it is qualified; otherwise, it is unqualified.

5. Input voltage drop and output dynamic load

test introduction

During the actual use of the primary module, when the input voltage drops, the limit condition of the sudden load on the power module may occur. At this time, the power devices and magnetic components work in the maximum transient current state, and the test can check the control sequence and current limit. The rationality of circuit and software design for protection.

testing method

a. Adjust the input voltage to jump between the undervoltage point +5v (duration is 5s) and the overvoltage point -5v (duration is 5s), and the output is adjusted to the maximum load (maximum rated capacity, duration is 500ms) , jump between no-load (duration is 500ms), run for 1 hour;

b. Adjust the input voltage to jump between the undervoltage point +5v (duration is 5s), the overvoltage point -5v (duration is 5s), and the output is adjusted to the maximum load (maximum rated capacity, duration is 1s), Jump between no-load (duration is 500ms), run for 1 hour.

judgement standard

Under the above conditions, it should be able to operate stably without damage or other abnormal phenomena, and it is qualified; otherwise, it is not qualified. In the event of damage, record the failure problem to provide a basis for analyzing the cause of the damage.

6. High-pressure no-load, low-pressure current-limiting operation test

test introduction

High-voltage no-load operation is the loss of the test module, especially the module with soft switching technology. Under no-load condition, the soft switch becomes hard switch, and the loss of the module increases accordingly. The low-voltage full-load operation is to test the loss of the module when the module is at the maximum input current. Under normal conditions, the module has the lowest efficiency when the module is in low-voltage input and full-load output, and the module generates the most serious heat at this time.

testing method

a. Adjust the input voltage of the module to the input overvoltage protection point -3v, and the output of the module is the lowest output voltage, no-load operation, at this time, the duty cycle of the module is the smallest, and the module should not be damaged after continuous operation for 2 hours;

b. Adjust the input voltage of the module to the undervoltage point +3v, and the output of the module is the inflection point state of the highest output voltage. At this time, the duty cycle of the module is the largest, and the module should not be damaged after continuous operation for 2 hours;

c. Adjust the input voltage of the module to the input voltage when the efficiency is the lowest point, the module output is the inflection point state of the highest output voltage, and run continuously for 2 hours, the module should not be damaged;

d. Adjust the input voltage of the module to the overvoltage point of -3v, and the output of the module is the inflection point state of the highest output voltage. At this time, the duty cycle of the module is the largest, and the module should not be damaged after continuous operation for 2 hours;

e. Adjust the input voltage of the module to the input voltage when the efficiency is the lowest point, and the module output is the inflection point state of the highest output voltage, and the module should not be damaged after continuous operation for 2 hours.

Note: The above tests must be carried out at the maximum operating temperature specified in the specification.

judgement standard

Working under the above conditions, the module is not damaged, it is qualified; otherwise it is unqualified.

7. Power supply special waveform test

test introduction

Verify the power module's ability to operate stably in the presence of spikes, glitches and harmonics that may be formed by grid waveform distortion. The following waveforms must be input for testing:

(1) Glitch input test waveform

The glitch of the power grid is the most common waveform in the power grid. There is no limit to the size and amplitude of the glitch. Generally, through the oscillation wave input test and the ringing input waveform, the glitch input in the power grid can basically be simulated. Do the following glitch input test

Features: The peak of the power grid has overshoot and will drop to 0v. The pulse width of overshoot and drop is very narrow, generally not greater than 100ms, and the overshoot amplitude is generally not more than 100v. The phase drop is not limited to the peak point, it can happen at any phase. This kind of waveform is very common in the real power grid, and opening any switch will cause this phenomenon.

(2) Voltage clipping waveform input

This waveform is also very common in power grids and is characterized by the fact that the power grid suddenly drops from an indeterminate phase to 0v, and then does not recover until the next half-wave begins. In iec1004-4-11, the drop of the waveform starts from more than half a cycle, but there are still many similar waveforms with a drop time less than half a cycle in the actual power grid. It is required during the test that the input voltage waveform starts to drop from 90 degrees, drops for 1/4 cycle, and works for 2 hours for a long time.

(3) The half wave head of the power grid rises sharply to double the voltage. This waveform is mainly used to simulate the resonance overvoltage that will suddenly appear in the actual power grid, and in this case, the input overvoltage protection circuit of the module does not work. , this shock is dangerous for circuits with pfc. Test content: a. When the input voltage is 180v and the output is fully loaded, use the ac source to simulate the waveform, requiring 180v to work for 3 minutes, then the voltage suddenly increases to 380v for 100ms, and then returns to 180v, so that the module is in this state. In case of working for 1 hour for a long time, it should not be damaged; b. Set the ac source so that the input voltage is 0v for 5 minutes, then the voltage suddenly increases to 380v for 100ms, and then returns to 0v, so that the module can be long in this case Time to work for 1 hour and should not be damaged.

testing method

Use the ac source to supply power to the module, and the module will output at full load; use the ac source to simulate the input of spikes, glitches and harmonic voltages, each special voltage input works for 2 hours, and measure the input current and output voltage. The module should be able to run stably. During the test, pay attention to the x capacitor, auxiliary power supply, soft-start resistor and other possible problems.

judgement standard

In practice, it can run stably in the case of sharp spikes, burrs, and harmonic voltages, without damage, and it is qualified; otherwise, it is unqualified.

8. Active pfc performance test

test introduction

Power modules with active pfc are sensitive to grid spikes, glitches and harmonics, and should be thoroughly and carefully tested.

testing method

Use ac source as the input voltage source, output with half load and full load respectively, test the input current waveform and voltage waveform, and monitor the voltage after pfc; Phase and amplitude relationship; measure the current and voltage of the pfc switch tube to verify the safety of the switch tube and other power devices and the ability of current to track voltage changes in the full voltage range and in the case of glitches, spikes, harmonics, etc.

judgement standard

The pfc test can be used as a reference for reliability. When serious problems occur, they should be solved in time.

9. Operating voltage test

test introduction

There are various operating overvoltages in the power grid, among which the most common is no-load line closing overvoltage, which is also a great threat to the module. This test is to verify the module's ability to resist operating overvoltage.

testing method

The simulation of the overvoltage line is very simple, the principle is as follows:

The parameter of the inductance is 10mh (for reference: in the module test method of ees, there is no grounding capacitor, the input resistance is connected in series with the inductance, the resistance value is 0 ohm, the inductance is 8mh, and the resistance is 79 ohms and the inductance is 10mh. ), the capacitance is 16.7uf, and the test waveform is as follows (not shown).

Connect the device under test to both ends of the capacitor, and at the moment of closing k, an overvoltage will be generated at both ends of the capacitor, which is used to simulate the degree of damage to the device caused by the overvoltage during the power-on process. As a limit test item, the input is connected to the l and n lines, the device to be tested is connected to both ends of the capacitor, the machine is switched on and off frequently, the repetition frequency is 1 time/5 minutes, and the continuous test is 5 hours. For three-phase input equipment, the input is connected to the l and l lines, and the device under test is connected to both ends of the capacitor. The repetition frequency is 1 time/5 minutes, and the continuous test is 2 hours.

judgement standard

In the test process, if there is short-term function decline or performance degradation, but it can be automatically recovered, it is qualified; but if the performance is permanently deteriorated or requires manual intervention to recover, it is not qualified.