Diode with Reverse Recovery

Purpose

Dynamic diode model with reverse recovery

Library

Electrical / Power Semiconductors

Description

This component is a behavioral model of a diode which reproduces the effect of reverse recovery. This effect can be observed when a forward biased diode is rapidly turned off. It takes some time until the excess charge stored in the diode during conduction is removed. During this time the diode represents a short circuit instead of an open circuit, and a negative current can flow through the diode. The diode finally turns off when the charge is swept out by the reverse current and lost by internal recombination.

Note

• Due to the small time-constant introduced by the turn-off transient a stiff solver is recommended for this device model.

• If multiple diodes are connected in series, the off-resistance may not be infinite.

Fig. 208 illustrates the relationship between the diode parameters and the turn-off current waveform. \(I_{\mathrm{f0}}\) and \(dI_{\mathrm{r}}/dt\) denote the continuous forward current and the rated turn-off current slope under test conditions. The turn-off time \(t_{\mathrm{rr}}\) is defined as the period between the zero-crossing of the current and the instant when it becomes equal to \(10\,\%\) of the maximum reverse current \(I_{\mathrm{rrm}}\). The reverse recovery charge is denoted \(Q_{\mathrm{rr}}\). Only two out of the three parameters \(t_{\mathrm{rr}}\), \(I_{\mathrm{rrm}}\), and \(Q_{\mathrm{rr}}\) need to be specified since they are linked geometrically. The remaining parameter should be set to \(0\). If all three parameters are given, \(Q_{\mathrm{rr}}\) is ignored.

Fig. 208 Reverse recovery current waveform

The equivalent circuit of the diode model is shown in Fig. 209. It is composed of a resistance, and inductance, and a controlled current source which is linearly dependent on the inductor voltage. The values of these internal elements are automatically calculated from the diode parameters.

Fig. 209 Reverse recovery diode equivalent circuit

Parameters

Forward voltage

Additional dc voltage \(V_{\mathrm{f}}\) in volts \((\mathrm{V})\) between anode and cathode when the diode is conducting. The default is 0.

On-resistance

The resistance \(R_{\mathrm{on}}\) of the conducting device, in ohms \((\Omega)\). The default is 0.

Off-resistance

The resistance \(R_{\mathrm{off}}\) of the blocking device, in ohms \((\Omega)\). The default is 1e6. This parameter may be set to inf unless multiple diodes are connected in series.

Continuous forward current

The continuous forward current \(I_{\mathrm{f0}}\) in amperes \((\mathrm{A})\) under test conditions.

Current slope at turn-off

The turn-off current slope \(dI_{\mathrm{r}}/dt\) in \(\left( \frac{\mathrm{A}}{\mathrm{s}} \right)\) under test conditions.

Reverse recovery time

The turn-off time \(t_{\mathrm{rr}}\) in seconds \((\mathrm{s})\) under test conditions.

Peak recovery current

The absolute peak value of the reverse current \(I_{\mathrm{rrm}}\) in amperes \((\mathrm{A})\) under test conditions.

Reverse recovery charge

The reverse recovery charge \(Q_{\mathrm{rr}}\) in coulombs \((\mathrm{C})\) under test conditions. If both \(t_{\mathrm{rr}}\) and \(I_{\mathrm{rrm}}\) are specified, this parameter is ignored.

Lrr

This inductance acts as a probe measuring the \(di/dt\). It should be set to a very small value, in henries \((\mathrm{H})\). The default is 10e-10.

Probe Signals

Diode voltage

The voltage measured between anode and cathode.

Diode current

The current through the diode flowing from anode to cathode.

Diode conductivity

Conduction state of the internal switch. The signal outputs \(0\) when the diode is blocking, and \(1\) when it is conducting.

References

• A. Courtay, “MAST power diode and thyristor models including automatic parameter extraction”, SABER User Group Meeting Brighton, UK, Sept. 1995.