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Diode High Current Stored Charge Measurement

IP.com Disclosure Number: IPCOM000082126D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Penney, FJ: AUTHOR

Abstract

This circuit measures diode stored charge (reverse recovery) by squarewave techniques, at current levels in excess of 100 amps forward current (Ifm). A unique feature is that the reverse recovery portion of the waveform may be separated from the total waveform. By using conventional analog-to-digital (A/D) converter techniques, this waveform may be read out directly in coulombs of stored charge.

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Diode High Current Stored Charge Measurement

This circuit measures diode stored charge (reverse recovery) by squarewave techniques, at current levels in excess of 100 amps forward current (Ifm). A unique feature is that the reverse recovery portion of the waveform may be separated from the total waveform. By using conventional analog-to-digital (A/D) converter techniques, this waveform may be read out directly in coulombs of stored charge.

Input A turns on Q1, Q2, D3 and the diode under test (DUT). The collector voltage (Vcc) is set at a value to keep Q1 and Q2 out of saturation. Input B turns on Q3 and Q4. This turns off Q1, Q2 and D3. Voltage Vee now becomes the reverse voltage for the DUT and the collector voltage for Q3 and Q4. Transistors Q3 and Q4 are driven heavily into saturation. Current probe B senses only the reverse recovery portion of the waveform. This may readily be converted to coulombs of stored charge. Current probe A senses the complete waveform which may be displayed on an oscilloscope.

Diodes D1 thru D4 are low-current, fast-recovery devices. Diodes D1 and D2 speed up the turn off of Q1 and Q2. Transistors Q1 thru Q4 consist of several high-speed, high-current devices in parallel.

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