Start-up circuit and method for AC-DC converters using a depletion mode transistor
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorsMohammad Al-Shyoukh, Percy Neyra
Life of this patent
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Abstract
An AC-DC power converter includes a rectifying unit for generating a rectified voltage, an output stage for converting the rectified voltage into a DC voltage for a load, a controller for controlling the output stage, and a start-up circuit. The start-up circuit includes a first power section coupled to the rectifying unit and configured to generate a first voltage from the rectified voltage and to output the first voltage to the controller to enable the controller before the output stage starts outputting power. The first power section includes a depletion mode transistor having a first terminal configured to receive the rectified voltage and a second terminal configured to output the first voltage.
Claims20
An AC-DC power converter, comprising:
- a rectifying unit configured to rectify an AC voltage to a rectified voltage;
- an output stage coupled to the rectifying unit and configured to convert the rectified voltage into a DC voltage for a load;
- a controller coupled to the output stage and configured to control the output stage;
- and
- a start-up circuit comprising a first power section which is coupled to the rectifying unit and configured to generate a first voltage from the rectified voltage and to output the first voltage to the controller to enable the controller before the output stage starts outputting power;
- a second power section coupled to the output stage and configured to generate a second voltage from power supplied by the output stage after the output stage starts operating;
- and
- a selector coupled to the first and second power sections and configured to select and output the higher of the first and second voltages to the controller;
- wherein the first power section comprises a depletion mode transistor having a first terminal configured to receive the rectified voltage and a second terminal configured to output the first voltage.
A power converter, comprising:
- a rectifying circuit;
- an output stage coupled to an output of the rectifying circuit;
- a controller coupled to a control node of the output stage;
- and
- a start-up circuit comprising:
- an input node coupled to the output of the rectifying circuit;
- an output node coupled to an input of the controller;
- a reference node;
- a depletion mode field-effect transistor (FET) having a first terminal coupled to the input node, a second terminal coupled to the output node, and a gate terminal configured to receive a gate voltage;
- a first diode having a cathode coupled to the gate terminal of the FET and an anode coupled to the reference node, wherein the first diode is a zener diode;
- a first capacitor coupled in parallel with the first diode;
- a first resistor coupled between the gate terminal of the FET and the input node;
- and
- a second resistor coupled between the second terminal of the FET and the reference node,
- wherein the first diode and the first resistor are configured to establish the gate voltage between the first diode and the first resistor by a current flowing through the first resistor.
A method of starting-up a power converter, the method comprising:
- generating an AC rectified voltage upon power-up of the power converter;
- generating, by a depletion mode field-effect transistor (FET), a first voltage from the rectified voltage;
- enabling, by the first voltage, a controller of the power converter before an output stage of the power converter starts outputting power;
- controlling, by the enabled controller, the output stage to output power;
- generating a second voltage from the power supplied by the output stage;
- and
- selecting and outputting the higher of the first and second voltages to the controller.
Dependencies are inferred from the claim text.