Apparatus for measuring the reverse recovery charge of fast semiconductor diodes

摘要

1,083,526. Measuring diode recovery charge. V#YZKUMN#Y …STAV MATEMATICK#YCH STROJ…. Jan. 13, 1966 [Jan. 28, 1965], No. 1639/66. Heading G1U. In an apparatus for measuring the reverse recovery charge of a fast semi-conductor diode, the diode D is pulsed from a generator G and the voltage produced across a load resistor R is applied to an input 5 of a sampling oscilloscope 1 having a CRT display 2. The sampling oscilloscope effects a time transposition of the reverse recovery waveform to enable it to be displayed. The charge flowing in the reverse recovery process is measured by developing a voltage which is applied to a calibration input of the sampling oscilloscope in such a manner as to shift the level of the display showing the reverse recovery so that it is equally balanced about the zero axis. The system operates in a self balancing manner to keep this calibration voltage at a value appropriate to maintain the balance, and this value is proportional to the charge to be measured. To derive this voltage, the reverse recovery waveform, applied via the sampling oscilloscope to the vertical plate 4 of the CRT, is also applied via a condenser 10 to a detector 11, 12. As the waveform swings negative into the reverse recovery region, the detector passes a pulse which triggers a gating pulse generator 13. This generator provides a pulse, whose width is adjustable, which is supplied to open the gates 14, 15. The reverse recovery waveform itself is passed via the gate 14 to the integrating network 16, 17, and the integrated signal is passed via a high gain amplifier 18 to a meter 19 and to the other input of the gate 15. The voltage is therefore passed for the period allowed by the generator 13 to the calibrating input 6 of the sampling oscilloscope. The generator 13 is set to provide a pulse slightly longer than the time required for the recovery process to be completed. Near the end of each time base sweep provided from the sampling oscilloscope a trigger signal is derived at the output 7 which operates a switch 9 via a switching pulse generator 8 to discharge the capacitor 10. The system establishes a balance such that the indicator 19 shows a voltage proportional to the recovery charge to be measured.