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US 2020/0007041 A1Published application
Boot strap capacitor charging for switching power converters
AssigneeDialog Semiconductor GmbH
InventorsWenduo Liu, Cong Zheng
Life of this patent
Estimating the term…
Abstract
A charging path is provided for the charging of an bootstrap capacitor that stores a driver power supply voltage for driving an active clamp switch transistor in a flyback converter. The charging path couples charge from an active clamp capacitor to charge the bootstrap capacitor.
Claims23
A flyback converter, comprising:
- an active clamp capacitor;
- a bootstrap capacitor for storing a driver power supply voltage for driving an active clamp switch transistor connected to a positive plate of the active clamp capacitor, wherein the active clamp capacitor has a negative plate connected to a primary winding of a transformer;
- a power supply capacitor for storing a power supply voltage for a controller for controlling the switching of a power switch transistor;
- a first diode coupled between bootstrap capacitor and the power supply capacitor for coupling charge from the power supply capacitor to charge the bootstrap capacitor;
- and
- a second diode in series with a resistor connected between the positive plate of the active clamp capacitor and the bootstrap capacitor for coupling charge from the active clamp capacitor to charge the bootstrap capacitor.
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A method of operation for a flyback converter, comprising:
- charging a power supply capacitor to provide a power supply voltage to a controller for the flyback converter;
- conducting charge from the power supply capacitor through a diode path to charge a bootstrap capacitor to provide a driver power supply voltage for driving an active clamp switch transistor;
- switching on a charging transistor responsive to the power supply voltage being less than a threshold voltage to conduct charge from a positive plate of an active clamp capacitor through the charging transistor to charge the bootstrap capacitor;
- and
- switching off the charging transistor responsive to the power supply voltage being greater than the threshold voltage.
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A flyback converter, comprising:
- an active clamp capacitor;
- a bootstrap capacitor for storing a driver power supply voltage for driving an active clamp switch transistor connected to a positive plate of the active clamp capacitor, wherein the active clamp capacitor has a negative plate connected to a primary winding of a transformer;
- a power supply capacitor for storing a power supply voltage for a controller for controlling the switching of a power switch transistor;
- a diode coupled between bootstrap capacitor and the power supply capacitor for coupling charge from the power supply capacitor to charge the bootstrap capacitor;
- a charging transistor coupled between the positive plate of the active clamp capacitor and a positive plate of the bootstrap capacitor;
- and
- a control circuit configured to switch on the charging transistor to charge the bootstrap capacitor responsive to the power supply voltage for the controller being less than a reference voltage.
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Dependencies are inferred from the claim text.