طراحی از Hipot تستر ماژول

The parameters that need to be monitored in the withstand voltage test are: the value of the transformer output high voltage and the leakage current value of the test circuit (as shown in Figure 2). The secondary winding of the step-up transformer used in the test system has two voltage outputs: 0~5000V and 0~5V. When the high voltage output of the transformer secondary winding changes from 0V to 5000V, the low voltage output of the transformer secondary winding changes from 0V to 5V, and there is a good linear relationship between the two outputs. At the beginning of the test, within the set boost time interval, the voltage output from the low voltage side of the transformer secondary winding enters the single-chip microcomputer ADCm842 after the isolation transformer and the signal conditioning circuit. The 12-bit ADC in the single-chip microcomputer ADCm842 performs high-speed A/D conversion at a conversion speed of 420,000 times per second. The digital quantity after A/D conversion is transmitted to the computer and compared with the computer set value until the output voltage meets the set voltage value. We believe that the actual output test voltage meets the requirements of our set value.
The test range of leakage current of the withstand voltage test system is 0mA ~ 20mA. At the beginning of the test, the leakage current of the device under test passes through the current transformer, and then the I/V conversion circuit converts the sampled current into voltage for corresponding A/D conversion and calculation in the single-chip microcomputer. Finally, the leakage current value of the device under test under the set voltage condition is obtained. By comparing it with the leakage current value specified in the safety standard, it can be checked whether the device withstand voltage test is qualified. In actual testing, an overcurrent protection circuit is designed on the secondary side of the current transformer. When an overcurrent occurs, such as the device under test is broken down or the insulation of the device under test is defective, the power supply is quickly cut off and the test is terminated to protect the test system from damage.
The conventional signal conditioning part uses true effective value analog calculation. The effective value and peak value calculation of the leakage current signal are input into the single-chip microcomputer or computer after the hardware circuit is completed. This signal conditioning method can only obtain the peak value or effective value of the leakage current signal. This method is not only not accurate but also loses frequency information, and cannot truly reproduce the actual waveform of the leakage current. This system uses high-speed A/D conversion to directly collect the AC voltage value into the computer, calculate the peak value and effective value according to the user's requirements, and draw the real-time leakage current waveform so that the user can intuitively monitor the leakage current. The computer can also perform software correction to remove errors caused by drift and offset. According to actual conditions, digital filtering can also be used to remove high-frequency interference. This signal conditioning method simplifies the hardware circuit, has low cost, high test accuracy, and good test stability. Since the test voltage of the withstand voltage test is high, in order to ensure the safety of the test, the chassis shell of the test system must be well grounded during the test.