Systems, circuits, devices, and methods with bidirectional bipolar transistors
Methods, systems, circuits, and devices for power-packet-switching power converters using bidirectional bipolar transistors (BTRANs) for switching. Four-terminal three-layer BTRANs provide substantially identical operation in either direction with forward voltages of less than a diode drop. BTRANs are fully symmetric merged double-base bidirectional bipolar opposite-faced devices which operate under conditions of high non-equilibrium carrier concentration, and which can have surprising synergies when used as bidirectional switches for power-packet-switching power converters. BTRANs are driven into a state of high carrier concentration, making the on-state voltage drop very low.
1. A power-packet-switching power converter, comprising:
a plurality of phase legs which each include two bidirectional switches which can connect a respective external line to either side of a link inductor which is paralleled by a capacitor, each said bidirectional switch comprising:
first and second first-conductivity-type emitter regions on opposing faces of a second-conductivity-type semiconductor mass,
first and second second-conductivity-type base contact regions, in proximity to said first and second emitter regions respectively, and
oxide-filled trenches between each said first-conductivity-type emitter region and respectively adjacent second-conductivity-type base contact regions;
control circuitry which, repeatedly, turns on a selected one or two of said bidirectional switches to drive energy from one or more input lines into said inductor, and then turns off all of said switches to disconnect said inductor, and then turns on a different selected one or two of said bidirectional switches to drive energy from said inductor onto one or two output lines; and
a drive circuit which, when the control circuitry selects one of said bidirectional switches for turn-on, drives a base contact region of that switch, to forward bias the associated emitter-base junction and permit majority carriers to flow to the other emitter region on the opposing surface;
wherein the drive circuit drives sufficient current through the selected base contact region to generate a total nonequilibrium carrier concentration, in the interior of said semiconductor mass, which is more than thirty times as great as the off-state equilibrium majority carrier concentration, to thereby lower the voltage drop across the switch to less than half a diode drop;
wherein, when one said bidirectional switch is conducting in a first direction from one said face, the emitter regions on the opposing face act as collector regions.
2. The power-packet-switching power converter of claim 1 , wherein said bidirectional switches are driven in a regime of high carrier densities.
3. The power-packet-switching power converter of claim 1 , wherein the second-conductivity-type base contact regions in said bidirectional switches are more highly doped than the respective second-conductivity-type semiconductor mass.
4. The power-packet-switching power converter of claim 1 , said bidirectional switches further comprising a thin layer of tunnel oxide between each said first-conductivity-type emitter region and the respective second-conductivity-type semiconductor mass.
5. The power-packet-switching power converter of claim 1 , said bidirectional switches further comprising a thin layer of tunnel oxide between each said first-conductivity-type emitter region and a respective emitter metallization.
6. The power-packet-switching power converter of claim 1 , wherein emitter-base junctions of said bidirectional switches are heterojunctions.
7. The power-packet-switching power converter of claim 1 , wherein the first-conductivity-type emitter regions of said bidirectional switches are amorphous silicon, and the respective second-conductivity-type semiconductor mass is substantially monocrystalline silicon.
8. The power-packet-switching power converter of claim 1 , wherein the first-conductivity-type emitter regions of said bidirectional switches are polycrystalline silicon, and the respective second-conductivity-type semiconductor mass is substantially monocrystalline silicon.
9. The power-packet-switching power converter of claim 1 , each said bidirectional switch further comprising a respective edge termination structure which comprises a first-conductivity-type region in a second-conductivity-type region.
10. A power-packet-switching power converter, comprising:
a plurality of phase legs which each include two bidirectional switches which can connect a respective external line to either side of a link inductor which is paralleled by a capacitor; each said bidirectional switch comprising:
first-conductivity-type emitter regions on opposing faces of a second-conductivity-type semiconductor mass, and second-conductivity-type base contact regions in proximity to respective emitter regions;
control circuitry which turns on two of said bidirectional switches to drive energy from one or more input lines into said inductor, and then turns off all of said switches to disconnect said inductor, and then turns on a different two of said bidirectional switches to drive energy from said inductor onto one or two output lines; and
a drive circuit which, when the control circuitry selects one of said bidirectional switches for turn-on:
begins turn-on by shorting a first one of the base contact regions of that switch to the respective emitter region, while leaving the base contact regions on the opposing face of that switch floating;
drives said first one of the base contact regions, to forward bias the associated emitter-base junction and permit majority carriers flow to the other emitter region on the opposing surface, thereby entering saturation mode;
shorts said first one of the base contact regions to the respective emitter region, thereby exiting saturation mode;
begins turn-off by shorting the base contact region on the opposing surface to the respective emitter region; and
completes turn-off by causing said first one of the base contact region to float;
wherein, when said drive circuit drives said first one of the base contact regions, the drive circuit drives sufficient current through the selected base contact region to generate a total nonequilibrium carrier concentration, in said semiconductor mass, to thereby lower the voltage drop across the switch.
11. The power-packet-switching power converter of claim 10 , wherein, when one said bidirectional switch is conducting in a first direction from one said face, the emitter regions on the opposing face act as collector regions.
12. The power-packet-switching power converter of claim 10 , wherein said bidirectional switches are driven in a regime of high carrier densities.
13. The power-packet-switching power converter of claim 10 , wherein the second-conductivity-type base contact regions in said bidirectional switches are more highly doped than the respective second-conductivity-type semiconductor mass.
14. The power-packet-switching power converter of claim 10 , said bidirectional switches further comprising a thin layer of tunnel oxide between each said first-conductivity-type emitter region and the respective second-conductivity-type semiconductor mass.
15. The power-packet-switching power converter of claim 10 , said bidirectional switches further comprising a thin layer of tunnel oxide between each said first-conductivity-type emitter region and a respective emitter metallization.
16. A power-packet-switching power converter, comprising:
a plurality of phase legs which each include two bidirectional switches which can connect a respective external line to either side of a link inductor which is paralleled by a capacitor; each said bidirectional switch comprising:
first-conductivity-type emitter regions on opposing faces of a second-conductivity-type semiconductor mass, and second-conductivity-type base contact regions in proximity to respective emitter regions;
control circuitry which turns on two of said bidirectional switches to drive energy from one or more input lines into said inductor, and then turns off all of said switches to disconnect said inductor, and then turns on a different two of said bidirectional switches to drive energy from said inductor onto one or two output lines; and
a drive circuit which, when the control circuitry selects one of said bidirectional switches for turn-on:
begins turn-on by shorting a first one of the base contact regions of that switch to the respective emitter region, while leaving the base contact regions on the opposing face of that switch floating;
drives said first one of the base contact regions, to forward bias the associated emitter-base junction and permit majority carriers flow to the other emitter region on the opposing surface, thereby entering saturation mode;
shorts said first one of the base contact regions to the respective emitter region, thereby exiting saturation mode;
begins turn-off by shorting the base contact region on the opposing surface to the respective emitter region; and
completes turn-off by causing said first one of the base contact region to float;
wherein, when said drive circuit drives said first one of the base contact regions, the drive circuit drives sufficient current through the selected base contact region to generate a total nonequilibrium carrier concentration, in said semiconductor mass, to thereby lower the voltage drop across the switch;
wherein emitter-base junctions of said bidirectional switches are heterojunctions.
17. The power-packet-switching power converter of claim 10 , wherein the first-conductivity-type emitter regions of said bidirectional switches are amorphous silicon, and the respective second-conductivity-type semiconductor mass is substantially monocrystalline silicon.
18. The power-packet-switching power converter of claim 10 , wherein the first-conductivity-type emitter regions of said bidirectional switches are polycrystalline silicon, and the respective second-conductivity-type semiconductor mass is substantially monocrystalline silicon.
19. The power-packet-switching power converter of claim 10 , said bidirectional switches further comprising oxide-filled trenches between each said first-conductivity-type emitter region and respectively adjacent second-conductivity-type base contact regions.