High speed-high voltage switching with low power consumption

• US 4,070,589 A
• Filed: 10/29/1976
• Issued: 01/24/1978
• Est. Priority Date: 10/29/1976
• Status: Expired due to Term

• Current Assignee: Hughes Aircraft Company (Rtx Corporation)
• Original Assignee: Singer PLC (Hayleys Plc)
• Inventors: Martinkovic, David John
• Primary Examiner(s): Zazworsky, John
• Application Number:
  US05/737,095
• Time in Patent Office: 452 Days
• Field of Search: 307/246, 307/254, 307/268, 307/270, 328/67, 320/1
• US Class Current: 327/111
• CPC Class Codes: H03K 17/04126 in bipolar transistor switches
• CPC Class Codes: H03K 17/10 Modifications for increasing the maximum permissible switched voltage
• CPC Class Codes: H03K 2217/0036 Means reducing energy consumption

Abstract

A capacitive load is charged through a series transistor. Peak charge currents for the load are drawn from a capacitive source whose charge is constantly maintained. Rapid discharge of the capacitive load is through a semiconductor diode and a cascade of transistors which act as switching elements. Diodes across the base-emitter junction of these switching diodes provide protection against transient damage as well as reducing the time required to cut-off conduction of the transistors. A simple transistor TTL drive (+5v) operates the switch.

Claims

1. A high speed-high voltage switch which consumes little power when operative to charge and discharge a capacitive load comprising:

a storage capacitor of several orders of magnitude greater capacity than the capacitive load;

means to continually maintain a desired charge level on said storage capacitor;

a conduction path of variable impedance connecting said storage capacitor and said capacitive load;

a switched discharge path operative to discharge said capacitive load while simultaneously increasing the impedance of said variable impedance conduction path; and

drive means to establish the operating state (charge or discharge) of said high speed-high voltage switch.

2. The high speed-high voltage switch of claim 1 in which the variable impedance conduction path comprises a transistor, said impedance being a function of the β

of said transistor.

3. The high speed-high voltage switch of claim 1 in which said switched discharge path comprises:

a series of transistors connected between said capacitive load and the discharge potential to which the load is to be drawn, the number of said transistors required being a function of the break-down voltage rating of each transistor and the voltage to be switched; and

means to provide equal sharing among said transistors of said voltage to be switched.

4. The high speed-high voltage switch of claim 3 in which said switched discharge transistors further comprise means to protect said transistors from the adverse effect of reverse bias transients.

5. The invention of claim 4 in which said protective means comprise diodes used to clamp the reverse bias, base-emitter voltages to safe levels.

6. The high speed-high voltage switch of claim 5 further comprising means to protect said drive means from high voltages which may appear on said transistors.

7. The invention of claim 6 in which said protective means comprise diodes within the base circuit of said transistors to block high voltages which may appear on said transistor base.

8. The high-speed, high voltage switch of claim 1 in which said drive means is a simple TTL drive comprising:

a transistor having its collector connected to a low voltage source and to said switched discharge path, its emitter to ground, and its base to a drive signal source.

9. A method for switching a capacitive load so as to charge and discharge it at high voltage levels and high speed while consuming minimal power comprising the steps of:

storing high voltage energy within a capacitor relatively large with respect to the load;

maintaining a continual charge on said capacitor;

drawing charge from said capacitor to charge said load;

drawing said charge through a variable impedance path;

providing a switched discharge path to discharge said load while simultaneously increasing the impedance of said variable impedance charge path; and

providing a drive signal to control the operating of said switched discharge path and of said variable impedance charge path.