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Reducing Diode Reverse Recovery Current

IP.com Disclosure Number: IPCOM000084277D
Original Publication Date: 1975-Oct-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Bauman, KA: AUTHOR

Abstract

A frequently encountered problem is the reduction of peak reverse recovery current in a diode which is being commutated from a forward to a reverse-biased state. It is desirable to accomplish this reduction with minimal effect on commutation time. Described is the use of a saturating inductance for this purpose.

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Reducing Diode Reverse Recovery Current

A frequently encountered problem is the reduction of peak reverse recovery current in a diode which is being commutated from a forward to a reverse-biased state. It is desirable to accomplish this reduction with minimal effect on commutation time. Described is the use of a saturating inductance for this purpose.

The basic problem is illustrated schematically in Fig. 1, wherein Vs, Zs is a low-impedance source. Fig. 2 shows a typical diode current commutation waveform for the circuit of Fig. 1.

Irm = [2Qr (dI/dt)]/1/2/, where dI/dt is the rate of change of current after the current passes through zero. dI/dt for the circuit in Fig. 1 is limited only by stray inductances and the turnon characteristics of the switch SW. Thus, dI/dt can be very high resulting in a high peak reverse recovery current Irm. In the past the value of dI/dt has been reduced by utilization of a linear inductor in series with the diode D1. However, this may operate to increase commutation time undesirably.

Fig. 3 shows a saturating inductor L1 in series with diode D1, and a resistor R1 and diode D2 shunting L1. Inductor L1 is designed to saturate at a current level less than Ifm. The diode current commutation waveform associated with Fig. 3 is shown in Fig. 4. The waveform of Fig. 4 depicts the same high dI/dt as Fig. 2 until L1 come out of saturation. Then a reduced dI/dt results which yields a lower Irm, without a proportionate lengthening of the over...