LOW POWER AND LOW EMI POWER STEALING CIRCUIT FOR A CONTROL DEVICE

• US 20140368036A1
• Filed: 06/14/2013
• Published: 12/18/2014
• Est. Priority Date: 06/14/2013
• Status: Active Grant

• Current Assignee: Sinope Technologies, Inc.
• Original Assignee: Sinope Technologies, Inc.
• Inventors: HOUDE, Francois, MAYER, Sylvain, MARCOUX-HOUDE, Samuel
• Granted Patent: US 9,608,507 B2
• Time in Patent Office: Days
• US Class Current: 307/31
• CPC Class Codes: H02M 1/0006 Arrangements for supplying an adequate voltage to the control circuit of converters
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters

Abstract

There is provided a device and a method for controlling a supply of power from an AC power source to a load. A switch is arranged in series electrical connection between the power source and the load, the switch having a first state in which the switch connects the load to the power source for supplying an electrical current from the power source to the load and a second state in which the switch disconnects the load from the power source. A power stealing circuit is arranged in parallel electrical connection to the switch and adapted to divert the electrical current away from the power source with the switch in the second state, the power stealing circuit comprising a linear semiconductor device adapted to control a rate of change of a first voltage across terminals of the switch upon the switch being brought to the first state.

Claims

1. A control device for controlling a supply of power from an AC power source to a load, the control device comprising:

a switch arranged in series electrical connection between the power source and the load, the switch having a first state in which the switch connects the load to the power source for supplying an electrical current from the power source to the load and a second state in which the switch disconnects the load from the power source; and

a power stealing circuit arranged in parallel electrical connection to the switch and adapted to divert the electrical current away from the power source with the switch in the second state, the power stealing circuit comprising a linear semiconductor device adapted to control a rate of change of a first voltage across terminals of the switch upon the switch being brought to the first state.

2. The control device of claim 1, wherein the power stealing circuit comprises a charge storage device adapted to store therein an electrical charge when the electrical current is diverted away from the power source.

3. The control device of claim 2, further comprising a control unit adapted to determine a charging time of the charge storage device and to estimate therefrom a power consumed by the load.

4. The control device of claim 3, wherein the power stealing circuit comprises a voltage detector for monitoring a second voltage across terminals of the charge storage device and, if the voltage detector determines that the second voltage has reached a threshold value, for causing the control unit to output a control signal for activating the linear semiconductor device.

5. The control device of claim 4, wherein the linear semiconductor device comprises a linear MOSFET adapted, when activated, to lower with a controlled rate a line voltage supplied by the power source towards zero volts for decreasing the rate of change of the first voltage and a level of interference generated upon the switch being brought to the first state.

6. The control device of claim 5, wherein the control unit waits a predetermined time delay for the line voltage to approach zero volts prior to applying a first pulse on a gate terminal of the switch to bring the switch into conduction.

7. The control device of claim 5, wherein the power stealing circuit further comprises a zero crossing detector for monitoring the line voltage, and, if the line voltage approaches zero volts, for causing the control unit to apply a first pulse on a gate terminal of the switch to bring the switch into conduction.

8. The control device of claim 7, wherein the line voltage comprises a plurality of repeating cycles and further wherein, a half-cycle after the line voltage approaches zero volts, the control unit applies a second pulse on the gate terminal to maintain the conduction of the switch.

9. The control device of claim 8, wherein the control unit causes at least a portion of the electrical charge stored in the charge storage device to be applied on the gate terminal.

10. The control device of claim 1, wherein the control device comprises a two-wire line voltage thermostat adapted to receive one or more radio-frequency signals indicative of instructions to operate at least one of the load and the thermostat and adapted to transmit one or more radio-frequency signals indicative of an operating condition of at least one of the load and the thermostat in response to the instructions.

11. A power stealing circuit for a control device controlling a supply of power from an AC power source to a load, the control device comprising a first switch having a first state in which the first switch connects the load to the power source for supplying an electrical current from the power source to the load and a second state in which the first switch disconnects the load from the power source, the power stealing circuit comprising:

a second switch arranged in parallel electrical connection with the first switch for diverting the electrical current away from the power source with the first switch in the second state;

a charge storage device coupled to the second switch and adapted to store therein an electrical charge when the electrical current is diverted away from the power source; and

a linear semiconductor device arranged in parallel electrical connection with the first switch and adapted to control a rate of change of a first voltage across terminals of the first switch upon the first switch being brought to the first state.

12. The power stealing circuit of claim 11, further comprising a voltage detector for monitoring a second voltage across terminals of the charge storage device, and, if the voltage detector determines that the second voltage has reached a threshold value, for causing the linear semiconductor device to be activated.

13. The power stealing circuit of claim 12, wherein the linear semiconductor device comprises a linear MOSFET adapted, when activated, to lower with a controlled rate a line voltage supplied by the power source towards zero volts for decreasing the rate of change of the first voltage and a level of interference generated upon the first switch being brought to the first state.

14. The power stealing circuit of claim 13, further comprising a control unit adapted to wait a predetermined time delay for the line voltage to approach zero volts prior to applying a first pulse on a gate terminal of the first switch to bring the first switch into conduction.

15. The power stealing circuit of claim 13, further comprising a zero crossing detector for monitoring the line voltage and a control unit in communication with the zero crossing detector, wherein, if the line voltage approaches zero volts, the zero crossing detector causes the control unit to apply a first pulse on a gate terminal of the first switch to bring the first switch into conduction.

16. The power stealing circuit of claim 15, wherein the line voltage comprises a plurality of repeating cycles and further wherein a half-cycle after the line voltage approaches zero volts, the control unit applies a second pulse on the gate terminal of the first switch to maintain the conduction of the first switch.

17. The power stealing circuit of claim 16, wherein the control unit causes at least a portion of the electrical charge stored in the charge storage device to be applied on the gate terminal.

18. The power stealing circuit of claim 17, wherein the control unit is adapted to determine a charging time of the charge storage device and to estimate therefrom a power consumed by the load.

19. A method for controlling a supply of power from an AC power source to a load, the method comprising:

diverting an electrical current away from the power source;

storing an electrical charge in a charge storage device upon the electrical current being diverted away from the power source;

comparing a voltage across terminals of the charge storage device to a threshold value;

if the voltage reaches the threshold value, outputting a control signal for activating a linear semiconductor device, the linear semiconductor device, when activated, controllably lowering a line voltage supplied by the power source towards zero volts; and

applying, when the line voltage approaches zero volts, a first pulse on a gate terminal of a switch arranged in series electrical connection between the power source and the load to trigger the switch.

20. The method of claim 19, further comprising, prior to applying the first pulse, one of monitoring the line voltage for detecting when the line voltage approaches zero volts and waiting a predetermined time delay for the line voltage to approach zero volts.

21. The method of claim 20, further comprising, a half-cycle after the line voltage reaches zero volts, applying a second pulse on the gate terminal of the switch to maintain a conduction state of the switch.

22. The method of claim 21, further comprising, determining a charging time of the charge storage device and estimating therefrom a power consumed by the load.

23. A two-wire line voltage thermostat for controlling a supply of power from an AC power source to a load, the thermostat comprising:

a switch arranged in series electrical connection between the power source and the load, the switch having a first state in which the switch connects the load to the power source for supplying an electrical current from the power source to the load and a second state in which the switch disconnects the load from the power source;

a power stealing circuit arranged in parallel electrical connection to the switch and adapted to divert the electrical current away from the power source with the switch in the second state, the power stealing circuit comprising a linear semiconductor device adapted to control a rate of change of a first voltage across terminals of the switch upon the switch being brought to the first state; and

a communications module adapted to receive one or more input radio-frequency signals indicative of instructions to operate at least one of the load and the thermostat.

24. The thermostat of claim 23, wherein the communications module is adapted to receive the one or more input radio-frequency signals from one or more remote devices and to transmit to the one or more remote devices one or more output radio-frequency signals indicative of an operating condition of the at least one of the load and the thermostat in response to the instructions.