Bel Fuse (macao Commercial Offshore) Limited

Bel Fuse, Inc.

Scott Moore

Mark Jutras

Mark Masera

A power switch includes a bridge-connected switching circuit with (1) a pair of MOSFETs back-to-back in series between line and load connections, an interconnection point of the MOSFETs being a first common connection, and (2) a pair of diodes back-to-back between the line and load connections, an interconnection point of the diodes being a second common connection. A line/load controller has supply inputs connected to the first and second common connections for receiving operating power, and (1) places both MOSFETs in the ON state to deliver normal operating current to the load for normal operation, and (2) places both MOSFETs in the OFF state to deliver (by body diode conduction) a substantially reduced leakage current to the load when the load is not powered for normal operation, the leakage current providing the operating power to the line/load controller.

Power switch with power harvesting for local controller

A power supply includes signaling circuitry coupled to output terminals for engaging in bidirectional communications with a load. A controller is capable of conducting the bidirectional communications and selecting among different operating modes for the power supply based on the communications. The modes may include a constant-current mode suitable for applications such as battery charging and power LED lamps, and a constant-voltage mode suitable for a variety of conventional uses such as powering electronic circuitry. The signaling circuitry may include a power switching transistor in series with the load, which is pulsed in a binary fashion to transmit communications to the load. A signal-forming resistor in parallel with the power switching transistor develops a signaling voltage monitored by the controller to receive communications from the load.

Power supply having selectable operation based on communications with load

A power supply for an LED lamp has a set of coupled coils, primary-side power circuitry including a converter power switch for conducting input power, and secondary-side power circuitry including a dimming power switch. Power control circuitry includes converter control circuitry which generates a converter control signal for the converter power switch to maintain a desired undimmed level of lamp current at a normal operating value of a lamp voltage. Dimming control circuitry generates a dimming control signal for the dimming power switch to pulse-width modulate the lamp current at a duty cycle corresponding to a desired dimming. Operation of the converter control circuitry is modified during dimming to prevent an automatic increase of the lamp voltage in response to a decrease in lamp current, avoiding undesirable overshooting of the lamp current and providing more accurate and effective control over dimming operation.

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Westford, MA, United States of America

Scott Moore