Share the inrush current test circuit for power adapter diode, provided by Shenzhen adapter manufacturer. Tell you about the basic requirements and standard test methods of diode forward surge current test. In view of the shortcomings of standard test methods, we have designed and implemented a circuit solution that uses signal control, capacitor energy storage, and high-power FET transistor current drive. , Simple and efficient realization of the diode forward surge current test.
One: Generation of sine half-wave pulse current:
Diodes have a variety of specifications, and the common rated on-state current ranges from hundreds of milliamps to hundreds of amps or even higher. The peak pulse current required for IFSM testing requires tens of times the rated on-state current value. The standard test method is to use a large-capacity industrial frequency transformer to intercept the AC power waveform to generate a sine half-wave pulse with a time constant of 10 ms and a conduction angle of 0 ° to 180 °. This method generates hundreds of thousands of amperes. The sinusoidal pulse current, the volume and weight of the transformer used are very considerable, and it is very inconvenient to install and use. Some foreign companies' products have special requirements for the surge inrush current waveform. For example, they require a sine half-wave pulse with a time constant of 10ms or 8.3ms and a conduction angle of 0 ° to 180 °. Current, or it is required to apply two consecutive sinusoidal half-wave pulse currents with a time constant of 10ms or 8.3ms and a conduction angle of 0 ° to 180 °. Obviously, it is difficult to meet the test requirements of different devices by using the mains interception method.
2: Design ideas:
High-power FET transistors are a standard class of voltage-controlled current devices. In the linear working area of a VDMOS tube, the drain current is controlled by the gate voltage: IDS = GFS * VGS . Apply the required voltage waveform to the gate, and the corresponding current waveform will be output at the drain. Therefore, the selection of high-power VDMOS tubes is suitable for achieving the required surge current waveform. The op amp composes a basic reverse operation circuit to drive the gate of the VDMOS tube. The drain-source current is added to the op amp's inverting input through the source sampling resistor of the VDMOS tube and added to the input waveform to form feedback. The gate voltage VGS of the VDMOS tube further controls the drain output current IDS . This IDS is the forward surge current applied to the diode under test (DUT).
The power and current amplification capability of a single VDMOS tube is limited, and it cannot reach the output current capability of thousands of amps. Using multiple parallel connections can solve this problem to achieve the required peak current. This test scheme uses mature circuit control technology to concisely and effectively achieve the requirements of various surge impact tests. All the components are conventional and easily available. The assembled device is small in size and light in weight, and can be easily installed in an ordinary instrument box to become a standard test instrument. It has the characteristics of flexible use, easy operation, high test accuracy, safety and reliability.
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