Smart thermostat with active power stealing an processor isolation from switching elements
First Claim
1. A method comprising:
- closing a switching circuit for powering an external AC load, wherein closing the switching circuit causes the external AC load to receive power from an external AC source;
monitoring a voltage;
receiving control signals from a microcontroller to control the switching circuit, wherein the control signals pass through an isolation barrier between the microcontroller and the switching circuit;
opening the switching circuit for a time interval, wherein the time interval begins after the voltage is below a lower threshold;
harvesting power from the external AC source to raise the voltage during the time interval; and
ending the time interval after the voltage exceeds an upper threshold, wherein the time interval is short enough that the operation of the AC load is not affected during the time interval.
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Abstract
A circuit includes a monitoring circuit that monitors a voltage and a switching circuit. Closing the switching circuit causes an external AC load to receive power from an external AC source. The circuit further includes a control circuit that opens the switching circuit for a time interval, where the time interval begins after the voltage is below a lower threshold. The control circuit also ends the time interval after the voltage exceeds an upper threshold, where the time interval is short enough that the operation of the AC load is not affected during the time interval. The circuit also includes a power harvesting circuit that harvests power from the external AC source to raise the voltage during the time interval.
507 Citations
18 Claims
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1. A method comprising:
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closing a switching circuit for powering an external AC load, wherein closing the switching circuit causes the external AC load to receive power from an external AC source; monitoring a voltage; receiving control signals from a microcontroller to control the switching circuit, wherein the control signals pass through an isolation barrier between the microcontroller and the switching circuit; opening the switching circuit for a time interval, wherein the time interval begins after the voltage is below a lower threshold; harvesting power from the external AC source to raise the voltage during the time interval; and ending the time interval after the voltage exceeds an upper threshold, wherein the time interval is short enough that the operation of the AC load is not affected during the time interval. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A circuit comprising:
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a monitoring circuit that monitors a voltage; a switching circuit, wherein; closing the switching circuit causes an external AC load to receive power from an external AC source; a control circuit that; receives control signals from a microcontroller through an isolation barrier between the microcontroller and the switching circuit; opens the switching circuit for a time interval, wherein the time interval begins after the voltage is below a lower threshold; and ends the time interval after the voltage exceeds an upper threshold, wherein the time interval is short enough that the operation of the AC load is not affected during the time interval; and a power harvesting circuit that harvests power from the external AC source to raise the voltage during the time interval. - View Dependent Claims (11, 12, 13)
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14. A control device comprising:
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a capacitive element; a monitoring circuit that monitors a voltage associated with the capacitive element; a switching circuit, wherein; closing the switching circuit causes an external AC load to receive power from an external AC source; a control circuit that; receives control signals from a microcontroller through an isolation barrier between the microcontroller and the switching circuit; opens the switching circuit for a time interval, wherein the time interval begins after the voltage is below a lower threshold; and ends the time interval after the voltage exceeds an upper threshold, wherein the time interval is short enough that the operation of the AC load is not affected during the time interval; and a power harvesting circuit that harvests power from the external AC source to charge the capacitive element during the time interval. - View Dependent Claims (15, 16, 17, 18)
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Specification