Converter for converting an AC power main voltage to a voltage suitable for driving a lamp
AssigneeGroupe Delta Xfo, Inc.
InventorAndrew D. Piaskowski
Life of this patent
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Abstract
An electronic converter converts high-voltage AC power main voltage, such as 120V, 240V or 277V, to a low-voltage suitable for driving a halogen lamp. The converter includes a rectifier circuit, starter circuit, a driver circuit, a current sensing circuit and a transformer circuit. The current sensing circuit senses an output current of the converter. The sensed current is used to govern pulse-width modulation of the lamp drive voltage, to provide over-voltage protection. Temperature protection can also be provided to reduce drive current when the converter overheats. This enables reliable operation of the converter over an extended temperature range, and reduces the occurrence of converter component failures due to ground faults or overheating.
Claims33
A converter for converting an AC (alternating current) power main voltage to a voltage suitable for driving a lamp, the converter comprising:
- a rectifier circuit connectable to the AC power main, adapted to rectify the AC power main voltage and adapted to provide a DC (direct current) voltage;
- a driver circuit adapted to receive the DC voltage from the rectifier circuit, and provide a driver output voltage and a driver output current and further adapted to receive an output current limiting signal;
- a starter circuit for providing a starter signal that initiates oscillation at an operating frequency in the driver circuit;
- a sensing circuit for sensing an output current of the driver circuit and providing the output current limiting signal in response to the sensed output current of the driver circuit;
- and
- a transformer circuit for transforming the driver output voltage to a voltage suitable for driving the lamp.
The converter as claimed in claim 7 wherein the high-side switch has a control terminal, a first terminal and a second terminal;
- the low-side switch has a control terminal, a first terminal and a second terminal;
- the first, second, third and fourth windings of the feedback transformer respectively have a first terminal and a second terminal;
- and, the first terminal of the first winding is connected a second terminal of the driver circuit, the second terminal of the first winding is connected to a second input of the driver circuit, the first terminal of the second winding is connected to a ground reference node, the second terminal of the second winding is connected to a first input of the driver circuit, the first terminal of the third winding is connected to the control terminal of the high-side switch, the second terminal of the third winding is connected to a first output of the driver circuit, the first terminal of the fourth winding is connected to the first output of the driver circuit, the second terminal of the fourth winding is connected to a second output of the driver circuit, the first terminal of the high-side switch is connected to first terminal of the driver circuit, the second terminal of the high-side switch is connected to the first output of the driver circuit, the first terminal of the low-side switch is connected to the first output of the driver circuit and the second terminal of the low-side switch is connected to the second terminal of the driver circuit.
The converter as claimed in claim 7 wherein the high-side and low-side switches are N-channel field-effect transistors.
A method for controlling an output voltage of a driver circuit in response to an output current of a converter for converting an AC (alternating current) power main voltage to a voltage suitable for driving a lamp, the method comprising the steps of:
- sensing the converter output current to determine whether the sensed converter output current exceeds a threshold;
- if the threshold is exceeded, sensing an extent to which the converter output current exceeds the threshold;
- triggering a latch when the sensed converter output current exceeds the threshold to stop an oscillation of the driver circuit;
- re-setting the latch after a period of time related to an extent to which the converter output current exceeded the threshold to permit the oscillation of the driver circuit to be re-started.
Dependencies are inferred from the claim text.