Test method for dynamic indicators of AC stabilized power supply

    Abstract: According to the SJ/T10542 standard approved and implemented by the former Ministry of Electronics Industry, this article introduces several main dynamic indicators of AC stabilized power supplies and their test methods.

    Keywords: standards, dynamic indicators, test methods

1 Maximum overshoot amplitude of the output voltage when the source voltage steps

    (1) Test conditions

    Quantities other than source voltage should comply with the reference conditions. The change quantity is the source voltage, and the measured value is the maximum overshoot instantaneous value of the output voltage.

    (2) Test method

    Connect the test circuit as shown in Figure 1.

    S1 is the source voltage step control switch. When the S1 position is at a, the power supply under test is powered by a higher source voltage. When the S1 position is at b, the power supply under test is powered by a lower source voltage. S1 is at a and b. When switching quickly between , the required source voltage step can be obtained.

    The function of R1 and R2 is to ensure uninterrupted power supply from the power supply under test. The resistance value should be selected so that the supply voltage is close to the lower value of the source voltage step at the moment when S1 is not connected to either side.

    N is a digital storage oscilloscope, which is used to measure and record the instantaneous value of the output voltage. The digital storage oscilloscope should have a sufficient sampling rate to accurately reflect the transient process of output voltage changes.

    T is a synchronous trigger, so that the generation of the source voltage step and the measurement start at the same time.

    Set the source voltage (position of the voltage regulator) according to the values ​​specified in Table 1, operate switch S1 to generate a source voltage step, and record the transient change waveform of the output voltage of the power supply under test at the same time.

Table 1 Data processing of source voltage step response test

    (3) Test results

    The maximum overshoot amplitude should be the instantaneous value of the output voltage overshoot (see Figure 2), and the test result will be the one with the largest voltage value.

2 Total recovery time of output voltage transient during source voltage step

    (1) Test conditions

    Quantities other than source voltage should comply with the reference conditions. The change is the source voltage, and the measurand is the total recovery time from the output voltage transient.

    (2) Test method

    The total recovery time of the output voltage transient during a source voltage step is measured simultaneously with the maximum overshoot amplitude of the output voltage.

    (3) Test results

    The total recovery time of the output voltage transient during a source voltage step includes the transient delay time and the transient recovery time (see Figure 2). The maximum measured value is the total recovery time.

3 Maximum overshoot amplitude of output voltage during load step

    (1) Test conditions

　　The remaining influencing quantities except load should comply with the baseline conditions. The amount of change is the output current, and the measured value is the instantaneous value of the maximum overshoot (overshoot or undershoot) of the output voltage.

    (2) Test method

    Connect the circuit as shown in Figure 1. In the figure:

    R3 and R4 are variable resistors, used to adjust the size of the load step. Adjust R3 so that the current flowing through it is equal to 30% IIN and 80% IIN respectively. Adjust R4 so that the current flowing through it is equal to 20% IIN.

    S2 is the load control switch.

    S3 is the load step 20% IIN control switch.

    Set the load as specified in Table 2, operate switches S2 and S3 to generate a load step, and record the transient change waveform of the output voltage of the power supply under test.

Table 2 Load step response test

    (3) Test results

    The maximum overshoot amplitude should be taken as the instantaneous value of the output voltage, and the one with the largest value in the measurement is the test result.

4 Total recovery time of output voltage transient during load step

    (1) Test conditions

    The remaining influencing quantities except load should comply with the baseline conditions. The amount of change is the output current, and the measured value is the instantaneous value of the maximum overshoot (overshoot or undershoot) of the output voltage.

    (2) Test method

    Connect the circuit as shown in Figure 1. The total recovery time of the load step transient is measured simultaneously with the measurement of the maximum overshoot amplitude of the load step.

    (3) Test results

    The total transient recovery time during load step includes transient delay time and transient recovery time. The maximum measured value is the total recovery time.

5 Start inrush current

    (1) Test conditions

    The load is the rated value, the amount that changes is the source voltage (from off to on), which is measured as the instantaneous value of the input current.

    (2) Test method

    Connect the circuit as shown in Figure 3.

    Connecting a non-inductive resistor R in series to the source input circuit has nothing to do with phase angle switching. Use a digital storage oscilloscope to measure and record the voltage drop of the starting inrush current on the resistor R and calculate the maximum instantaneous value of the starting inrush current.

    The value of resistor R should be selected so that the drop in source voltage when the starting inrush current occurs is less than 10% of the nominal value of the source voltage.

    During measurement, the phase angle switch is measured once every 15° (electrical angle). If there is no phase angle switching switch, it can be determined by statistical method, and the switch is randomly switched 20 times.

    If the power supply under test does not allow loading and starting, the test can be carried out under no-load conditions, and the test results should be marked "under no-load conditions".

6 Overshoot when turning on (off) the machine

    (1) Test conditions

    The load is the nominal value, the amount that changes is the source voltage (from off to on or from on to off), which is measured as the instantaneous value of the output voltage.

    (2) Test method

    Connect the circuit as shown in Figure 3, and connect the storage oscilloscope to the output of the power supply under test. Refer to the test method in Article 5(2), use the phase angle switch or the statistical method (randomly switch the switch 20 times) to conduct the startup and shutdown tests respectively, and measure the overshoot (instantaneous value) of the output voltage.

    (3) Test results

    The one with the largest instantaneous value of the switching (off) machine overshoot during measurement is the switching (off) machine overshoot value.