Double-base-connected bipolar transistors with passive components preventing accidental turn-on
The present application discloses new approaches to providing “passive-off” protection for a B-TRAN-like device. Even if the control circuitry is inactive, AC coupling uses transient voltage on the external terminals to prevent forward biasing an emitter junction. Preferably the same switches which implement diode-mode and pre-turnoff operation are used as part of the passive-off circuit operation.
1. A switching circuit, comprising:
a power semiconductor device which includes first and second first-conductivity-type emitter/collector regions on respective surfaces of a second-conductivity-type semiconductor die, separately defining first and second emitter junctions, and a first base contact region on the same surface as the first emitter/collector region, and a second base contact region on the same surface as the second emitter/collector region, both base contact regions separately making ohmic contact to the semiconductor die;
first drive transistors which, when ON, operatively connect the first base contact region to the first emitter/collector; and second drive transistors which, when ON, operatively connect the second base contact region to the second emitter/collector region; and
a transient coupling circuit, including at least one series resistor, which is operatively connected to electrically connect voltage slew across the emitter/collector regions to activate the drive transistors of whichever of the emitter/collector regions is becoming the emitter, to limit the voltage between that emitter/collector region and its corresponding base contact region;
a control circuit which drives the first and second base contact regions independently, to control turn on and turn off of conduction, including switching phases where the first drive transistors and second drive transistors connect at least one of the emitter/collector regions with its corresponding base contact region;
whereby forward voltage on the first emitter junction is limited to less than the forward diode voltage drop characteristic of the first emitter junction, and forward voltage on the second emitter junction to less than the forward diode voltage drop characteristic of the second emitter junction; and thereby leakage currents are not amplified when the control circuit is inactive, and breakdown voltage is not degraded by amplification of leakage currents.
2. The switching circuit of claim 1 , wherein the semiconductor die is silicon.
3. The switching circuit of claim 1 , wherein the emitter/collector region on the first said surface is not electrically connected to the emitter/collector region on the second said surface, except through the semiconductor die itself.
4. The switching circuit of claim 1 , wherein the base contact region on the first said surface is not electrically connected to the base contact region on the second said surface, except through the semiconductor die itself.
5. The switching circuit of claim 1 , wherein the first and second first-conductivity-type emitter/collector regions are both n-type.
6. The switching circuit of claim 1 , wherein the second-conductivity-type semiconductor die is p-type.
7. The switching circuit of claim 1 , wherein the first and second base contact regions are both p-type.
8. The switching circuit of claim 1 , wherein the first and second first-conductivity-type emitter/collector regions are both n-type, and wherein the second-conductivity-type semiconductor die and the first and second base contact regions are all p-type.
9. The switching circuit of claim 1 , wherein the transient coupling circuit does not include any series active devices.