A device for testing high-voltage transistors. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Measuring technology
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In the manufacture of switching network power supplies, high-voltage switching bipolar and field-effect transistors are widely used. The uninterrupted operation of the entire product largely depends on their reliability. Therefore, before installation, it is advisable to check them for an increased collector reverse current for the bipolar transistor or residual field drain current and determine if they can withstand the required operating voltage. This can be done using the device proposed by the authors. Based on the test results, specimens with the best parameters are selected.
Fig. 1
The scheme of the device is shown in fig. 1. A rectifier with voltage tripling is assembled on diodes VD1-VD4 and capacitors C1-C3. Resistor R1 limits the charging current of capacitors when the device is turned on, and resistors R2-R5 ensure their rapid discharge when turned off. A digital multimeter DT1 or similar with an input resistance of 830 MΩ is connected to the XS1 socket, set to a DC voltage measurement limit of 1000 V. The bipolar or field effect transistor under test, taking into account its structure, is connected to the XS2 or XS3 socket, after which the input of the device is connected to the gradually increase its output voltage.
The rectified voltage is supplied to a multimeter and a transistor connected in series. With an input resistance of the multimeter of 1 MΩ in the voltage measurement mode at the limit of 1000 V, each volt corresponds to a current of 1 μA. If the collector reverse current and the residual drain current are small (not exceeding a few microamps), the voltmeter reading will also not exceed a few volts. When an electrical breakdown occurs or an increase in the reverse current of the collector (residual drain current), the voltmeter readings increase significantly. According to the author's experience, critical readings are 10 ... 20 V, while the voltage applied to the tested transistor can be determined by pressing the SB1 button. In this case, the entire output voltage of the rectifier will go to the multimeter. Since the current through the tested transistor does not exceed 1 mA, when an electrical breakdown occurs, it is not damaged.
The device uses MLT resistors, capacitors K75-12, K75-24; the SB1 button must withstand a voltage of 1000 V between the terminals and between the terminals and the case, KP-1, KP-2, KP-3 are suitable. Sockets XS2, XS3 for connecting transistors are made from a panel for installing microcircuits.
Fig. 2
All parts are placed in a housing made of insulating material a few millimeters thick by surface mounting. The appearance of the device is shown in fig. 2, the SB1 button and sockets XS1-XS3 are attached to the top panel, a wire with a power plug is brought out to connect to the LATR.
The device also allows you to determine the stabilization voltage of high-voltage zener diodes, the breakdown voltage of rectifier or protective diodes, gas-discharge devices, such as neon lamps and other devices.
When operating the device, remember the safety rules and do not touch the tested elements during their testing.
Author: Yu. Gumerov, A. Zuev, Ulyanovsk; Publication: radioradar.net
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