Abstract: Power stealing circuitry to provide power to a controller for an environmental control system. The power stealing circuitry may include a first circuit, to steal power when a load for a stage is switched off, e.g. de-energized. The power stealing circuitry may include a second circuit, e.g., a power trickle circuit, to steal power when the load is switched on, e.g., energized. The load may include a furnace, electrical heating element, heat pump, humidifier, electrostatic filter, air conditioning unit and so on. In some examples, the environmental control system may have one or many stages, each with a separate load. The controller may include power stealing circuitry for each stage of the environmental control system. In other words, the controller may include a first circuit and a second circuit for each stage of a multi-stage environmental control system.

Abstract: Power stealing circuitry to provide power to a controller for an environmental control system. The power stealing circuitry may include a first circuit, to steal power when a load for a stage is switched off, e.g. de-energized. The power stealing circuitry may include a second circuit, e.g., a power trickle circuit, to steal power when the load is switched on, e.g., energized. The load may include a furnace, electrical heating element, heat pump, humidifier, electrostatic filter, air conditioning unit and so on. In some examples, the environmental control system may have one or many stages, each with a separate load. The controller may include power stealing circuitry for each stage of the environmental control system. In other words, the controller may include a first circuit and a second circuit for each stage of a multi-stage environmental control system.

Abstract: A circuit to isolate a first circuit node from second circuit node at certain times yet connect the first circuit node and second circuit node at other times. For example, the isolation circuit may isolate a reference node from a system ground during certain phases of operation, but temporarily connect the reference node to the system ground during other phases. An isolation circuit of this disclosure may include a pair of MOSFETs in a back-to-back connection. The MOSFETs may be placed between the two nodes to be isolated. The MOSFETS may be driven by a bipolar junction transistor (BJT). A control signal applied to the BJT emitter controls the operation of the pair of MOSFETs. The isolation or connection from the power supply reference node to system ground may be controlled by applying a HIGH or LOW logic signal to the PNP transistor emitter.