Switch with common-mode choke
In one embodiment, a level-shifter for driving a high-side power switch with sub-nanosecond timing integrity, without requiring a high-side gate-drive power supply, is provided. A drive source is connected to the gate of a power switch through a common-mode choke, and the latter level-shifts the common-mode voltage of the drive signal to the common-mode level of the power switch. The same level-shifter may also be used to drive a low-side power switch to avoid ground bounce.
1. A substantially bistable power switch comprising:
at least one gate-charge retaining power transistor; and
control circuitry responsive to at least one control signal, said control circuitry capable of injecting charge into and removing charge from the gate of the power transistor responsive to the control signal; and
at least one common-mode choke connected to the gate of the power transistor through which charge injection or charge removal occurs; wherein the power switch is bistable.
2. The switch of claim 1 wherein the circuit through which current for both gate-charge injection and gate-charge removal passes includes a common-mode choke.
3. The switch of claim 1 wherein the circuit through which current for gate-charge injection only passes includes a common-mode choke.
4. The switch of claim 1 wherein the circuit through which current for gate-charge removal only passes includes a common-mode choke.
5. The switch of claim 1 wherein the circuit through which current for gate-charge injection passes includes a first common-mode choke and the circuit through which current for gate-charge removal passes includes a second common-mode choke.
6. The switch of claim 1 wherein the common-mode choke comprises a recovery winding.
7. The switch of claim 1 wherein a snubber is used to effect magnetic field reset.
8. A method of level-shifting a gate-drive voltage for a power switch, the method comprising:
connecting a gate-drive voltage supply in a circuit with a gate of a power switch via switches and a common-mode choke;
applying a voltage to turn the power switch on or off by closing and opening said switches.
9. The method of claim 8 wherein the power switch is substantially bistable.
10. The method of claim 8 wherein the gate-drive voltage supply is connected in a series circuit with the gate and source of the power switch via the switches and the common-mode choke.