Soft shutdown modular circuitry for power semiconductor switches
View Patent ↗Circuitry for soft shutdown of a power switch and a power converters that includes circuitry for soft shutdown are described. In one aspect, circuitry for soft shutdown of a power switch includes a sense input to be coupled to a power switch receive a signal representative of current passing through the power switch, a comparator to compare the signal with an overcurrent threshold indicative of an overcurrent condition of the power switch and to output a triggering signal in response to the comparison indicating the overcurrent condition, and a gating transistor to be coupled to a control terminal of the power switch, the gating transistor configured to divert a portion of a drive signal away from the control terminal of the power switch in response to the triggering signal.
1. Circuitry for a soft shutdown of a power switch, the circuitry comprising:
a sense input coupled to the power switch receive a signal representative of current passing through the power switch;
a comparator coupled to compare the signal representative of current passing through the power switch with an overcurrent threshold indicative of an overcurrent condition of the power switch, wherein the comparator is coupled to output a triggering signal in response to the comparison indicating the overcurrent condition;
latch circuitry coupled to the comparator to latch the triggering signal;
a resistance coupled between an output terminal and a reset terminal of the latch circuitry;
a timing capacitor coupled to the resistance and the reset terminal of the latch circuitry, wherein the reset terminal is coupled to receive an input signal representative of a duration of the soft shutdown of the power switch from the timing capacitor, wherein the latch circuitry is coupled to be reset in response to the input signal received from the timing capacitor; and
a gating transistor coupled to an output of the latch circuitry and to a control terminal of the power switch, the gating transistor configured to divert a portion of a drive signal away from the control terminal of the power switch in response to the output of the latch circuitry.
2. The circuitry of claim 1 , wherein:
the sense input is a current sense input; and
the signal representative of current passing through the power switch is a current sense signal.
3. The circuitry of claim 1 , wherein:
the sense input is a voltage sense input; and
the signal representative of current passing through the power switch is a voltage sense signal representative of the potential difference between main terminals of the power switch.
4. The circuitry of claim 1 , wherein the duration of the soft shutdown of the power switch is determined by the input signal in response to a time constant set by magnitudes of the timing capacitor and the resistance such that the gating transistor is latched to divert the portion of the drive signal away from the control terminal for the duration of the soft shutdown of the power switch.
5. The circuitry of claim 1 , wherein the latch circuitry is a D-type flip flop.
6. The circuitry of claim 1 , further comprising an overcurrent threshold adjust input coupled to receive a signal to adjust the overcurrent threshold.
7. The circuitry of claim 1 , wherein the circuitry for soft shutdown of a power switch is modular.
8. The circuitry of claim 7 , wherein the circuitry for soft shutdown is packaged in an integrated circuit package that is discrete from the power switch and driver circuitry that outputs the drive signal.
9. The circuitry of claim 7 , wherein the circuitry for soft shutdown is assembled on a circuit board that is discrete from the power switch and driver circuitry that outputs the drive signal.
10. A power converter comprising:
a power switch having a control terminal and first and second main terminals;
driver circuitry coupled to output a drive signal to drive the control terminal of the power switch so that the power switch switches between a first, more conductive ON state and a second, less conductive OFF state;
a switching controller coupled to control the driving of the control terminal by the driver circuitry; and
modular soft shutdown circuitry coupled to at least one of the main terminals and to the control terminal of the power switch, wherein the modular soft shutdown circuitry is configured to sense an overcurrent condition in the power switch in response to the sensing of the overcurrent condition to slow the transition of the power switch from the ON state into the OFF state, wherein the modular soft shutdown circuitry comprises:
a sense input coupled to the power switch receive a signal representative of current passing through the power switch;
a comparator coupled to compare the signal representative of current passing through the power switch with an overcurrent threshold indicative of the overcurrent condition of the power switch, wherein the comparator is coupled to output a triggering signal in response to the comparison indicating the overcurrent condition;
latch circuitry coupled to the comparator to latch the triggering signal;
a resistance coupled between an output terminal and a reset terminal of the latch circuitry;
a timing capacitor coupled to the resistance and the reset terminal of the latch circuitry, wherein the reset terminal is coupled to receive an input signal representative of a duration of the soft shutdown of the power switch from the timing capacitor, wherein the latch circuitry is coupled to be reset in response to the input signal received from the timing capacitor; and
a gating transistor coupled to an output of the latch circuitry and to a control terminal of the power switch, the gating transistor configured to divert a portion of a drive signal away from the control terminal of the power switch in response to the output of the latch circuitry.
11. The power converter of claim 10 , wherein the modular soft shutdown circuitry is packaged in an integrated circuit package that is discrete from the power switch, the driver circuitry, and the switching controller.
12. The power converter of claim 10 , wherein the modular soft shutdown circuitry is assembled on a circuit board that is discrete from the power switch, the driver circuitry, and the switching controller.
13. The power converter of claim 10 , wherein:
the modular soft shutdown circuitry is housed in a housing; and
the power switch, the driver circuitry, and the switching controller are external to the housing.
14. The power converter of claim 10 , wherein the drive signal passes through the modular soft shutdown circuitry.
15. The power converter of claim 10 , wherein the duration of the soft shutdown of the power switch is determined by the input signal in response to a time constant set by magnitudes of the timing capacitor and the resistance such that the gating transistor is latched to divert the portion of the drive signal output from the driver circuitry away from the control terminal for the duration of the soft shutdown of the power switch.
16. The power converter of claim 10 , wherein the power converter comprises a plurality of power switches that are coupled in parallel.
17. The power converter of claim 10 , wherein the power switch comprises a tap and the modular soft shutdown circuitry is coupled to the at least one of the main terminals via the tap.
18. The power converter of claim 10 , wherein the power switch is a SiC power switch.