Control circuitry using two branch circuits for high voltage solid-state switches

• US 4,656,366 A
• Filed: 02/24/1982
• Issued: 04/07/1987
• Est. Priority Date: 12/28/1979
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Inventors: Shackle, Peter W., MacPherson, William F., Davis, James A., Mussman, Harry E.
• Primary Examiner(s): CLAWSON JR, JOSEPH
• Application Number:
  US06/351,911
• Time in Patent Office: 1,868 Days
• Field of Search: 357/22, 357/38, 357/58, 307/252 A, 307/252 C, 307/252 J, 307/252 K, 307/305, 307/311
• US Class Current: 327/474
• CPC Class Codes: H03K 17/567 Circuits characterised by the use of more than one type of semiconductor device, e.g. BIMOS, composite devices such as IGBT
• CPC Class Codes: H03K 17/74 by the use, as active elements, of diodes by the use of more than one type of semiconductor device H03K17/567; by the use of tunnel diodes H03K17/58; by the use of negative resistance diodes H03K17/70
• CPC Class Codes: H03K 17/785 controlling field-effect transistor switches

Abstract

To switch a first gated diode switch (GDSL1) to the "OFF" state requires a voltage applied to the gate which is more positive than that of the anode or cathode and a sourcing of current into the gate of substantially the same order of magnitude as flows between the anode and cathode of the first switch. Control circuitry, which uses a second gated diode switch (GDSC) coupled by the cathode to the gate of the first switch (GDSL1), is used to control the state of the first switch (GDSL1). The control circuitry also comprises a first branch circuit coupled to the anode of the GDSC and to a first potential source V1 and a second branch circuit coupled to the anode of GDSC and to a second potential source V2 which is of a lower potential than V1. The second branch circuit has a high voltage and high current capability switch in series between V2 and the anode of GDSC. The first branch circuit has a high voltage but modest current handling switch in series between V1 and the anode of GDSC. The second branch circuit is used to provide a surge of current if and when needed during the current break operation to turn GDSL1 to an OFF state and the first branch circuit is used to maintain the state of the load switch. The second branch circuit can be shared by many control circuits.

Claims

1. In combination:

a first switching device and a second switching device, each said device comprising a semiconductor body having a bulk portion which is of relatively high resistivity and of a first conductivity type, a first region of the first conductivity type and of relatively low resistivity, and second and third regions of a second conductivity type opposite that of the first conductivity type and of relatively low resistivity, the first and third regions being connected to separate output terminals of the switching device, the second region being coupled to a control terminal of the switching device, and the first, second, and third regions being mutually separated by portions of the bulk of the semiconductor body;

said second switching device having essentially same electrical characteristics as the first switching device, said second switching device being coupled to the first switching device and being used to provide control of the first switching device;

means coupled to the second switching device for aiding in selectively switching off the first switching device, said means comprising first and second branch circuits;

the first branch circuit being adapted to selectively allow up to a preselected current level to flow therethrough and to flow into or out of the control terminal of the first switching device;

the second branch circuit being adapted to substantially inhibit current flow therethrough if the level of current flow through the first branch circuit is less than the preselected current level; and

the second branch circuit being further adapted to allow a greater current level than the preselected level to flow therethrough and to flow into or out of the control terminal of the first switching device if, and only if, the current flowing through the first branch circuit reaches the preselected level.

2. In combination:

a first switching device and a second switching device, each said device comprising a semiconductor body having a bulk portion which is of relatively high resistivity and of a first conductivity type, a first region of the first conductivity type and of relatively low resistivity, and second and third regions of a second conductivity type opposite that of the first conductivity type and of relatively low resistivity, the first and third regions being connected to separate output terminals of the switching device, the second region being coupled to a control terminal of the switching device, the first, second, and third regions being mutually separated by portions of the bulk of the semiconductor body;

said second switching device having essentially same electrical characteristics as the first switching device, said second switching device being coupled by a second output terminal thereof to the control terminal of the first switching device for controlling the first device;

means, under the effective control of applied signals, coupled to a first output terminal of the second switching device for aiding in selectively switching off the first switching device, said means comprising first and second branch circuits which are each coupled to the first output terminal of the second switching device;

the first branch circuit being adapted to selectively allow up to a preselected current level to flow therethrough which flows through the second switching device and flows into or out of the first switching device;

the second branch circuit being adapted to substantially inhibit current flow therethrough if the level of current flow through the first branch circuit is less than the preselected level;

the second branch circuit being further adapted to allow a greater current level than the preselected level to flow therethrough which flows through the second switching device and flows into or out of the first switching device if, and only if, the current level flowing through the first branch circuit reaches the preselected level; and

the first and second branch circuits being adapted such that the current flowing through each does not flow through the other.

3. In combination:

a first gated diode switch and a second gated diode switch, each said switch comprising a semiconductor body having a bulk portion which is of relatively high resistivity and of a first conductivity type, a first region of the first conductivity type and of relatively low resistivity, and second and third regions of a second conductivity type opposite that of the first conductivity type and of relatively low resistivity, the first and third regions being connected to separate output terminals of the switching device, the second region being coupled to a control terminal of the switching device, and the first, second, and third regions being mutually separated by portions of the bulk of the semiconductor body;

the second gated diode switch having essentially same electrical characteristics as the first gated diode switch, said second gated diode switch being coupled by a second output terminal thereof to the control terminal of the first gated diode switch so as to control the first switch;

first means, under the effective control of applied signals, coupled to the second gated diode switch for controlling the second gated diode switch;

second means, under the effective control of applied signals, coupled to a first output terminal of the second gated diode switch for aiding in selectively switching off the first gated diode switch, said second means comprising first and second branch circuits which are each coupled to the first output terminal of the second gated diode switch;

the first branch circuit being adapted to selectively allow up to a preselected current level to flow therethrough which flows through the second gated diode switch and flows into or out of the control terminal of the first gated diode switch;

the second branch circuit being adapted to substantially inhibit current flow therethrough if the level of current flow through the first branch circuit is less than the preselected level;

the second branch circuit being further adapted to allow a greater current level than the preselected level to flow therethrough which flows through the second gated diode switch and then flows into or out of the control terminal of the first gated diode switch if, and only if, the current level flowing through the first branch circuit reaches the preselected level; and

the first and second branch circuits being adapted such that the current flowing through each does not flow through the other.

4. The combination of claim 3 wherein:

the first means and the first branch circuit comprise third (T3), fourth (T4), fifth (T5) and sixth (T6) switching devices, and a current limiter;

the third, fourth, and fifth switching devices each being a separate p-n-p type junction transistor and the sixth switching device being an n-p-n type junction transistor, each of the transistors having a base, a collector, and an emitter;

the base terminal of T3 being coupled to an input combination terminal;

the collector of T3 being coupled to the collector of T6 and to the control terminal of the second gated diode switch;

the emitter of T3 being coupled to the base of T4;

the emitters of T4 and T5 being coupled together and being adapted to be coupled to a first potential source;

the collector of T4 being coupled to the base of T5 and to a first terminal of the current limiter;

a second terminal of the current limiter being coupled to the second output terminal of the second gated diode switch;

the collector of T5 being coupled to the base of T6; and

the emitter of T6 being coupled to the first output terminal of the second gated diode switch.

5. The combination of claim 4 wherein:

the second branch circuit comprises first and second resistors, a capacitor, and an n-p-n junction photo-transistor;

a first terminal of the first resistor being adapted to be coupled to a second potential source;

a second terminal of the first resistor being coupled to a first terminal of the capacitor and to a first terminal of the second resistor;

a second terminal of the second resistor being coupled to a collector of the photo-transistor; and

an emitter of the photo-transistor being coupled to the first output terminal of the second gated diode switch.

6. The combination of claim 5 further comprising:

seventh (T2) and eighth (T1) switching devices;

T2 being a p-n-p junction transistor and T1 being an n-p-n junction transistor, each of T1 and T2 having a base, emitter and collector;

the base of T2 being coupled to the input combination terminal;

the emitter of T2 being coupled to the emitter of T3;

the collector of T2 being coupled to the base of T1; and

the collector and emitter of T1 being coupled to the control terminal and one of the output terminals, respectively, of the first gated diode switch.

7. The combination of claim 6 wherein the first and second output terminals and the control terminal are the anode, cathode, and gate terminals, respectively, of each gated diode switch.