Power supply for in-line power controllers and two-terminal electronic thermostat employing same

摘要

A two-terminal electronic thermostat connectable in series with an electrical heater and a source of AC power and selectively providing AC power to the electrical heater, and a power supply incorporated in the thermostat for providing DC power to the control circuitry of the thermostat, includes a relay connectable in series with the electrical heater, a control circuit for selectively actuating the relay, an ambient temperature sensor and a potentiometer for setting a set point temperature. The power supply includes a current transformer having its primary winding connected in series with the relay and the electrical heater. The power supply also includes a first bridge rectifier circuit, a second bridge rectifier circuit connected to the secondary winding of the current transformer and a capacitor divider network formed from first and second capacitors and providing a desired DC voltage to the control circuit. The first capacitor is coupled to the first bridge rectifier circuit. The first and second bridge rectifier circuits have DC outputs which are connected across the second capacitor of the network, which also acts to filter the DC voltage provided to the control circuit of the thermostat.