Fail-safe driver circuit

Claim 2

In a power control system, the combination of a power circuit for supplying low frequency AC power to a load coupled to the power circuit; a bilateral unitary switch inserted in the power circuit and convertible from a high impedance to a low impedance to permit the flow of said low frequency AC power through said load, said bilateral switch returning to its high impedance when said AC power goes through each node of its successive half cycles; and a relaxation oscillator forming a generator for converting low voltage, small amplitude current into a train of high frequency large amplitude pulses for delivery to said bilateral switch to continuously apply to said bilateral switch pulses during each succeeding positive and negative half cycle of the AC power to cause said bilateral switch to exhibit substantially continuously a low impedance to the flow of current from said source of AC power to the load during said succeeding half cycles of said source, said relaxation oscillator including a breakdown device and a capacitor connected to said bilateral switch for charging said capacitor and discharging said capacitor through said breakdown device, said relaxation oscillator also including opposite conductivity transistors having their respective bases and collectors coupled to each other, wherein said breakdown device is coupled in the collector circuit of one of said transistors.

Claim 3

In a power control system, the combination defined by claim 1, including, in addition, a low energy DC source to initiate the operation of the generator.

Claim 4

In a power control system, the combination in accordance with claim 2, in which the high-frequency pulses of the generator are of relatively much higher energy than the energy of said DC initiating source.

Claim 5

In a power control system, the combination defined by claim 2, in which said generator includes a plurality of components and in which said power circuit will not be activated upon the failure of any component of said generator when the low energy source does not call for the initiation of the generator.

Claim 6

In a power control system, in accordance with claim 4, the combination including, in addition, means to prevent actuation of the power circuit upon failure of said generator when the low energy source does not call for the initiation of the generator.

Claim 7

In a fail-safe power control system, the combination of a DC signal source of voltage continuously supplying a relatively small amount of energy; a relaxation oscillator for converting the DC signal voltage into a train of pulses of current of relatively high amplitude and high frequency during the continuous supply of DC voltage from said signal source; a unitary bilateral switch to which the high-frequency pulses are applied; each high-frequency pulse causing the bilateral switch to be Converted from a high impedance to a low impedance; a relatively low frequency power circuit which is independent of, but is controlled by, the DC signal source, said low-frequency power circuit including therein said bilateral switch to render the power circuit effective when a high-frequency pulse of current is applied to the bilateral switch and ineffective when said high-frequency pulse is suppressed; said bilateral switch being arranged to be deactivated upon the failure of said converting means when the signal source does not call for the actuation of the power circuit, said relaxation oscillator including a breakdown device and a capacitor connected to the bilateral switch for charging said capacitor according to the high amplitude current and discharging said capacitor through said breakdown device, said relaxation oscillator also including opposite conductivity transistors having their respective bases and collectors coupled to each other, wherein said breakdown device is coupled in the collector circuit of one of said transistors.

Claim 8

In a fail-safe power control system, the combination of a DC signal source of voltage continuously supplying a relatively small amount of energy; a relaxation oscillator for converting the DC signal voltage into a train of pulses of current of relatively high amplitude and high frequency during the continuous supply of DC voltage from said signal source; a unitary bilateral switch to which the high-frequency pulses are applied; each high-frequency pulse causing the bilateral switch to be Converted from a high impedance to a low impedance; a relatively low frequency power circuit which is independent of, but is controlled by, the DC signal source, said low-frequency power circuit including therein said bilateral switch to render the power circuit effective when a high-frequency pulse of current is applied to the bilateral switch and ineffective when said high-frequency pulse is suppressed; said bilateral switch being arranged to be deactivated upon the failure of said converting means when the signal source does not call for the actuation of the power circuit, said relaxation oscillator including a breakdown device and a capacitor connected to the bilateral switch for charging said capacitor according to the high amplitude current and discharging said capacitor through said breakdown device, said relaxation oscillator also including opposite conductivity transistors having their respective bases and collectors coupled to each other, wherein said breakdown device is coupled in the collector circuit of one of said transistors.

Claim 9

In a fail-safe power control system, the combination in accordance with claim 6, in which the converting means comprises a plurality of components, and in which the activation of the power circuit and the bilateral switch will not occur when any component of said converting means has failed and the signal source does not call for the actuation of the power circuit.

Claim 10

A fail-safe power control system comprising a power circuit for continuously supplying low frequency AC power to a load; a bilateral switch connected in series with said power circuit and serving as a control for said power circuit; said bilateral switch normally exhibiting a high impedance to block the flow of power to said load but exhibiting a low impedance when one or more high-frequency pulses of current are applied to said switch during each half cycle of said AC power; and a relaxation oscillator producing high-frequency pulses of current for transmission to said switch to operate it substantially continuously during successive and repetitive cycles of said AC power; said relaxation oscillator having a plurality of components which may fail; the bilateral switch continuing to exhibit a high impedance in response to the failure of any of the components of said generator; said relaxation oscillator including a breakdown device and a capacitor to be charged by the high-frequency pulses of current and to be discharged through said breakdown device, said relaxation oscillator also including opposite conductivity transistors having their respective bases and collectors coupled to each other, wherein said breakdown device is coupled in the collector circuit of one of said transistors.

Claim 11

A fail-safe power control system comprising a power circuit for continuously supplying low frequency AC power to a load; a bilateral switch connected in series with said power circuit and serving as a control for said power circuit; said bilateral switch normally exhibiting a high impedance to block the flow of power to said load but exhibiting a low impedance when one or more high-frequency pulses of current are applied to said switch during each half cycle of said AC power; and a relaxation oscillator producing high-frequency pulses of current for transmission to said switch to operate it substantially continuously during successive and repetitive cycles of said AC power; said relaxation oscillator having a plurality of components which may fail; the bilateral switch continuing to exhibit a high impedance in response to the failure of any of the components of said generator; said relaxation oscillator including a breakdown device and a capacitor to be charged by the high-frequency pulses of current and to be discharged through said breakdown device, said relaxation oscillator also including opposite conductivity transistors having their respective bases and collectors coupled to each other, wherein said breakdown device is coupled in the collector circuit of one of said transistors.

Claim 12

A fail-safe power control system according to claim 8, including, in addition, a low voltage DC signal source connected to the relaxation oscillator for initiating the operation of said transistor network.

Claim 13

A fail-safe power control system according to claim 9, in which the relaxation oscillator provides pulses to the bilateral switch of an energy level high enough to produce the specified impedance changes therein, so that only a substantially small amount of energy is derived from the low voltage DC signal source.