Controller of an auxiliary switch used in a flyback circuit and control method thereof
AssigneeHangzhou MPS Semiconductor Technology Ltd.
InventorXuefeng Chen
Life of this patent
Estimating the term…
Abstract
A controller for controlling auxiliary switch connected in series with a clamp capacitor to form an energy recycle branch in a flyback circuit. The controller has a power supply terminal to receive an external supply voltage, a sensing terminal connected to a first terminal of a current sense resistor which is connected in series with a primary switch, a ground terminal connected to a second terminal of the current sense resistor, a drive terminal connected to a control terminal of the auxiliary switch, and a turn on control circuit. Based on a logic state of a voltage at the power supply terminal and a voltage across the current sense resistor, the turn on control circuit provides a turn on control signal to control of the auxiliary switch.
Claims17
A controller for controlling an auxiliary switch, the controller comprising:
- a power supply terminal configured to receive an external supply voltage;
- a sensing terminal configured to be coupled to a first terminal of a current sense resistor which is connected in series with a primary switch;
- a ground terminal configured to be coupled to a second terminal of the current sense resistor;
- a drive terminal configured to be coupled to a control terminal of the auxiliary switch;
- and
- a turn on control circuit comprising:
- a logic state judgement circuit coupled to the power supply terminal to receive a voltage at the power supply terminal, wherein when a duration the voltage at the power supply terminal being a logic high level is longer than a first pre-determined period, the logic state judgement circuit is configured to provide a trigger signal having a first level;
- a turn on enable circuit coupled to the sensing terminal of the controller to receive a sensing signal representative of a voltage across the current sense resistor, wherein when the trigger signal is being the first level and the sensing signal is decreased to a first threshold voltage, the turn on enable circuit is configured to provide an enable signal having a first level;
- and
- an enable logic circuit configured to allow the auxiliary switch to be turned on when the enable signal is being the first level and a falling-edge of the voltage at the power supply terminal comes.
A flyback circuit, comprising:
- a primary switch coupled to the primary winding of a transformer via a current sense resistor;
- an auxiliary switch coupled in series with a clamp capacitor to form an energy recycle branch;
- and
- a controller, configured to control the auxiliary switch, comprising:
- a power supply terminal configured to receive an external supply voltage;
- a sensing terminal configured to be coupled to a first terminal of the current sense resistor;
- a ground terminal configured to be coupled to a second terminal of the current sense resistor;
- a drive terminal configured to be coupled to a control terminal of the auxiliary switch;
- and
- a turn on control circuit comprising:
- a logic state judgement circuit coupled to the power supply terminal to receive a voltage at the power supply terminal, wherein when a duration the voltage at the power supply terminal being a logic high level is longer than a first pre-determined period, the logic state judgement circuit provides a trigger signal having a first level;
- a turn on enable circuit coupled to the sensing terminal to receive a sensing signal representative of a voltage across the current sense resistor, when the trigger signal is being the first level and the sensing signal is decreased to a first threshold voltage, the turn on enable circuit is configured to provide an enable signal having a first level;
- and
- an enable logic circuit configured to allow the auxiliary switch to be turned on when the enable signal is being the first level and a falling-edge of the voltage at the power supply terminal comes.
A control method for controlling an auxiliary switch, and the control method comprising:
- receiving an external supply voltage at a power supply terminal of a controller;
- coupling a sensing terminal of the controller to a first terminal of a current sense resistor;
- coupling a ground terminal of the controller to a second terminal of the current sense resistor;
- coupling a drive terminal of the controller to a control terminal of the auxiliary switch;
- detecting the logic state of a voltage at the power supply terminal;
- providing a trigger signal having a first level when a duration a voltage at the power supply terminal being a logic high level is longer than a first pre-determined period;
- providing a sensing signal representative of a voltage across the current sense resistor;
- providing an enable signal with a first level when the trigger signal is being the first level and the sensing signal decreases to a first threshold voltage;
- and
- allowing the auxiliary switch to be turned on when the enable signal is being the first level and a falling-edge of the voltage at the power supply terminal comes.
Dependencies are inferred from the claim text.