# US 4,878,011 A · Proportional firing circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,878,011 A - Document ID: US4878011A - Status: Granted - Kind: A - Application number: 07/226,224 - Filed: 1988-07-29 - Granted: 1989-10-31 - Earliest claimed: 1988-07-29 - Assignees: Wolf Engineering Corporation - Inventors: Roger A. Holtslander - Web page: https://patentgrep.com/patent/US4878011A ## CPC - H03K 17/725: for AC voltages or currents (H03K17/722, H03K17/735 take precedence) - G05D 23/1913: {delivering a series of pulses} - G05F 1/452: {with pulse-burst modulation control} - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES ## Abstract A relay control circuit which is capable of reliably controlling the transmission of electrical power in very small time increments. Specifically, the present invention features a proportional firing circuit which will create an SCR firing signal whose pulse timing is proportional to the magnitude of a variable input signal. The control circuit varies the conduction time for the SCRs by varying the time between firing signal pulses of fixed duration. ## Claims ### Claim 1 In an electrical switching apparatus having semiconductor controlled rectifier means for controlling the transmission of electrical power from an alternating power supply, a proportional firing circuit comprising: input means for providing a variable signal whose magnitude is used to control the conduction of said semiconductor controlled rectifier means; timer means for generating a firing signal for said semiconductor controlled rectifier means whose pulse timing is proportional to the variable characteristic of said variable signal, so as to enable the conduction time of said semiconductor controlled rectifier means to be proportionally varied between a minimum conduction time which is associated with the cycling of said alternating power supply and a maximum conduction time; and zero crossing means receiving said firing signal of said timer means for permitting the conduction of said semiconductor controlled rectifier means only at zero crossing junctions in the alternating cycle of said power supply; wherein said firing signal has a fixed pulse duration, and only the time between the pulses of said firing signal is varied in response to said variable input signal. ### Claim 2 (depends on 1) The electrical switching apparatus according to claim 1, wherein said input means includes a variable resistor component. ### Claim 3 (depends on 2) The electrical switching apparatus according to claim 2, wherein said variable resistor component is a potentiometer. ### Claim 4 (depends on 2) The electrical switching apparatus according to claim 2, wherein said variable resistor component is an optical coupler, and said input means includes balanced resistor means connected to said optical coupler to enable the variable characteristic of the input signal to be either a variable voltage or a variable current. ### Claim 5 (depends on 1) The electrical switching apparatus according to claim 1, wherein said timer means includes a multivibrator component and RC timing components connected to both said multivibrator component and said input means. ### Claim 6 (depends on 5) The electrical switching apparatus according to claim 5, wherein said multivibrator component generally comprises a 555 timer integrated circuit. ### Claim 7 (depends on 1) The electrical switching apparatus according to claim 1, wherein said semiconductor controlled rectifier means comprises a pair of inverse parallel connected silicon controlled rectifiers for each phase of said alternating power supply. ### Claim 8 A multi-phase electrical switching apparatus circuit, comprising: a pair of inverse parallel connected semiconductor controlled rectifiers for at least two phases of a multi-phase electrical power supply; zero crossing means connected to the gate terminals of each of semiconductor controlled rectifier pairs for permitting the conduction of said semiconductor controlled rectifiers only at zero crossing junctions in the alternating cycle of said power supply; and proportional firing means for generating a firing signal for said semiconductor controlled rectifiers whose pulse timing is proportional to the magnitude of a variable input signal, so as to enable the conduction time of said semiconductor controlled rectifiers to be proportionally varied between a minimum conduction time which is associated with the cycling of said electrical power supply and a maximum conduction time; wherein said firing signal has a fixed pulse duration, and only the time between the pulses of said firing signal is varied in response to said variable input signal. ### Claim 9 (depends on 8) The multi-phase electrical switching apparatus circuit according to claim 8, wherein a pair of inverse parallel connected semiconductor controlled rectifiers is provided for each phase of said electrical power supply. ### Claim 10 (depends on 8) The multi-phase electrical switching apparatus circuit according to claim 8, wherein said semiconductor controlled rectifiers are silicon controlled rectifiers. ### Claim 11 (depends on 8) The multi-phase electrical switching apparatus circuit according to claim 8, wherein said variable input signal is provided through a variable resistor. ### Claim 12 (depends on 11) The multi-phase electrical switching apparatus circuit according to claim 11, wherein said proportional firing means includes a multivibrator component and a timing capacitor which is connected to both said multivibrator component and said variable resistor. ### Claim 13 (depends on 12) The multi-phase electrical switching apparatus circuit according to claim 12, wherein said variable resistor includes an optical coupler whose resistance is variable, and balanced resistor means is connected to said optical coupler to enable the variable characteristic of the input signal to be either a variable voltage or a variable current.