Universal Lighting Technologies, Inc.

Philip Walker

Stephen D Mays, Ii

Donald Folker

John Jay Dernovsek

Steve Mays

An isolated buck converter protects inverter switches during non-zero voltage switching and reduces output ripple current by maintaining operation of an output inductor of the isolated buck converter in a continuous current mode. Continuous current mode operation is maintained by various combinations of: shifting the frequency of operation of the inverter switches of the isolated buck converter as a function of output current of the isolated buck converter; employing pulse density modulation to decrease the off time of the isolated buck converter which will decrease the magnitude of the current ripple; and use a step gap core (i.e., a swinging choke) for the output inductor that saturates to a lower value of inductance for high load current and a higher value of inductance at low load current.

Reducing output ripple current and protecting inverter switches during non-zero voltage switching for isolated buck converters

A lighting device such as an electronic ballast or LED driver includes circuitry to detect power converter activity and act accordingly. A power factor correction (PFC) circuit includes an inductor, a power converter switch, and a PFC controller effective to provide driving signals the power converter switch to turn on and off. A power converter activity detection circuit includes a first capacitor coupled between the PFC controller and the power converter switch, a zener diode, and a second capacitor coupled between the first capacitor and ground. An output voltage for the power converter activity detection circuit as referenced from a node between the first capacitor and the second capacitor is representative of activity by the power converter switch, and is provided to a lighting device controller which may accordingly maintain operation of the lighting device where a mains power interruption is only temporary but would otherwise disable the device.

Lighting device with circuit and method for detecting power converter activity

A lighting device such as an electronic ballast or LED driver includes a power factor correction (PFC) controller responsive to input power supply signals to generate control signals, a PFC boost converter responsive to said control signals to generate a boosted output voltage, and a fast start circuit with a power supply source and an energy storage device, a magnitude of the input power supply signal corresponding to energy stored in the energy storage device. During a first mode, the fast start circuit responds to a rectified mains input to enable the power supply source and charge the energy storage device. During a second mode, the fast start circuit responds to a magnitude of the power supply signal to disable the power supply source and discharge the energy storage device. The boost converter during the second operating mode maintains controller operation while the power supply source is disabled.

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Manchester, TN, United States of America

Philip Walker