# US 10,873,329 B2 · High reliability AC load switching circuit

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- Number: US 10,873,329 B2
- Document ID: US10873329B2
- Status: Granted
- Kind: B2
- Application number: 16/385,020
- Filed: 2019-04-16
- Published: 2019-08-08
- Granted: 2020-12-22
- Earliest claimed: 2016-06-24
- Assignees: IDEAL Industries Lighting LLC
- Applicants: Ideal Industries Lighting LLC
- Inventors: Yuequan Hu; Amruteshwar Hiremath; Kory A. Liszt
- Web page: https://patentgrep.com/patent/US10873329B2

## CPC

- H03K 17/68: specially adapted for switching AC currents or voltages
- H03K 17/72: having more than two PN junctions; having more than three electrodes; having more than one electrode connected to the same conductivity region
- H02H 9/002: {limiting inrush current on switching on of inductive loads subjected to remanence, e.g. transformers}
- H03K 2217/0009: AC switches, i.e. delivering AC power to a load
- H03K 2217/0054: Gating switches, e.g. pass gates
- 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)
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)

## Abstract

A high reliability AC load switching circuit is disclosed. In some embodiments, the AC load switching circuit includes a high-speed switch connected between the load and the voltage source, a cutoff switch connected between the load and the voltage source in parallel with the high-speed switch, and a level detector connected to the voltage source and to a control input of the high-speed switch. The high-speed switch may be a solid-state switch, for example, a TRIAC or a bidirectional switch, and the cutoff switch may be an electromechanical switch, for example, a relay. In some embodiments a snubber is connected in parallel with a solid-state switch. In some embodiments a microcontroller is connected to an electromechanical switch and the level detector. In some embodiments, both a first cutoff switch and a second cutoff switch are used.

## Claims

### Claim 1

A switching circuit to selectively connect a load to a voltage source, the switching circuit comprising:
a high-speed switch connected between the load and the voltage source;
a snubber connected in parallel with the high-speed switch;
a cutoff switch connected between the load and the voltage source in parallel with the high-speed switch;
a level detector and control circuit connected to the voltage source and to a control input of the high-speed switch, wherein the control input is further connected to a portion of the switching circuit that is between the load and an output of the high-speed switch and between the load and an output of the cutoff switch; and
a controller comprising a first enabling input connected to the level detector and control circuit and a second enabling input connected to the cutoff switch, the controller further comprising a processor and memory storing at least one of firmware and software that is executable such that: the first enabling input is activated in response to a powering on signal received from the controller and the level detector and control circuit turns on the high-speed switch at a zero crossing of the voltage source, and the second enabling input is activated independent of the operation of the high-speed switch after the high-speed switch is turned on to turn on the cutoff switch, the high-speed switch remaining turned on after the cutoff switch is turned on.

### Claim 2 (depends on 1)

The switching circuit of claim 1 wherein the high-speed switch comprises a solid-state switch.

### Claim 3 (depends on 2)

The switching circuit of claim 2 wherein the solid-state switch comprises a triode for alternating current (TRIAC).

### Claim 4 (depends on 2)

The switching circuit of claim 2 wherein the solid-state switch comprises bidirectional switch.

### Claim 5 (depends on 1)

The switching circuit of claim 1 wherein the cutoff switch comprises an electromechanical switch and further comprising:
a transistor connected to the controller; and
a resistor connected between the transistor and the electromechanical switch.

### Claim 6 (depends on 1)

The switching circuit of claim 1 further comprising a second cutoff switch connected in series with the high-speed switch.

### Claim 7 (depends on 6)

The switching circuit of claim 6 wherein the cutoff switch, the second cutoff switch, or both the cutoff switch and the second cutoff switch each comprise an electromechanical switch.

### Claim 8 (depends on 7)

The switching circuit of claim 7 wherein the electromechanical switch comprises a relay.

### Claim 9 (depends on 6)

The switching circuit of claim 6 wherein the second cutoff switch is connected between the high-speed switch and the voltage source.

### Claim 10 (depends on 6)

The switching circuit of claim 6 wherein the second cutoff switch is connected between the high-speed switch and the load.

### Claim 11

A method of selectively connecting a load to an AC voltage through a switching circuit comprising a controller comprising a first enabling input connected to a level detector and control circuit and a second enabling input connected to a cutoff switch, the controller further comprising a processor and memory storing at least one of firmware and software, the method comprising:
activating the first enabling input from the controller in response to a powering on signal received from the controller to thereby enable the level detector and control circuit to turn on a solid-state switch between the AC voltage and the load at zero-crossing of the AC voltage;
suppressing voltage spikes and/or dampening ringing to prevent misfiring of the solid-state switch using a snubber connected in parallel with the solid-state switch; and
activating a second enabling input from the controller to close a first electromechanical switch connected in parallel with the solid-state switch independent of the operation of the solid-state switch after the turning on of the solid-state switch to turn on the cutoff switch, maintaining the solid-state switch turned on after the cutoff switch is turned on using a control input of the solid-state switch that is connected between the load and an output of the solid-state switch and between the load and an output of the cutoff switch.

### Claim 12 (depends on 11)

The method of claim 11 further comprising:
in response to a powering off signal received by the controller, deactivating the first electromechanical switch; and
turning off the solid-state switch after deactivating the first electromechanical switch.

### Claim 13 (depends on 11)

The method of claim 11 further comprising activating a second electromechanical switch connected in series with the solid-state switch prior to turning on the solid-state switch and in response to activation of the switching circuit.

### Claim 14 (depends on 13)

The method of claim 13 further comprising:
deactivating the first electromechanical switch;
turning off the solid-state switch; and
deactivating the second electromechanical switch.

### Claim 15 (depends on 11)

The method of claim 11 wherein the solid-state switch comprises bidirectional switch.

### Claim 16 (depends on 1)

The switching circuit of claim 1 wherein the high-speed switch is configured to remain turned on for an entire duration that the cutoff switch is turned on.