Bcd Semiconductor Manufacturing Limited

Other

Bcd Semiconductor Manufacturing Co., Ltd.

Qiang Zong

Yajiang Zhu

ShaoHua Fang

Jia Xie

Reixia Fei

BaoZhen Chen

Jianhua Duan

Pingan Zhao

Huizhen Zhu

Jinhua Duan

A power supply controller is provided for providing a drive current to a control terminal of a power transistor in three time intervals. The controller includes control circuits configured to control the drive current in multiple stages. During a first time interval, first drive current includes a current spike for turning on the power transistor in response to a start of the control signal pulse. During a second time interval, a second drive current includes a ramping current substantially proportional to a magnitude of a current through the power transistor. During a third time interval, current flow to the power transistor is at least partially turned off before an end of the control signal pulse.

Power transistor driving circuits and methods for switching mode power supplies

A synchronous rectification circuit for a power supply includes a power switch for coupling to a secondary winding of a transformer of the power supply and an output capacitor of the power supply. The power switch includes a four-terminal MOSFET having a source, a drain, a gate, and a body. A body diode is formed by a junction between the body and the drain or by a junction between the body and the source. The body diode is coupled in parallel to the source and drain of the power transistor. A control circuit is configured to provide a control signal for controlling an on/off state of the power switch in response to a voltage condition of two terminals of the power switch. When the body diode makes a transition from reverse bias to forward bias, the control circuit causes the MOSFET to turn on, and when the forward bias voltage drops below a reference voltage, the control circuit causes the MOSFET to turn off. When the body diode makes a transition from forward bias to reverse bias, the control circuit causes the MOSFET to turn off.

System and method for synchronous rectifier

A switched mode power supply (SMPS) includes a transformer with a primary winding, a secondary winding, an auxiliary winding, and a power switch coupled to the primary winding. During one switching cycle, the auxiliary winding provides a feedback signal which includes a first voltage pulse that is induced after the power switch is turned on and a second voltage pulse that is induced after the power switch is turned off. A control circuit includes a circuit for generating a sampling signal for sampling the second voltage pulse in a switching cycle at a time that is determined based on the first voltage pulse in the same switching cycle. A sample-and-hold circuit is configured for sampling and storing the second voltage pulse in response to the sampling signal. A switching signal generating circuit is configured to generate a switching signal for controlling the power switch based on an output of the sample-and-hold circuit.

Control circuit for primary side control of switching power supply

A startup circuit for a switching-mode power supply (SMPS) includes a first voltage detector configured to trigger the switching-mode power supply from a first operation mode to a second operation mode when an input supply voltage exceeds a first threshold voltage, a current consumption in the first voltage detector in the first operation mode being determined by a reverse leakage current of a diode. A feedback circuit is coupled to the first voltage detector and being capable of maintaining a positive feedback loop. A second voltage detector is coupled to the first voltage detector and the feedback circuit, and is configured to trigger the switching-mode power supply to switch from the second operation mode to the first operation mode when the input supply voltage is below a second threshold voltage.

Method and apparatus of low current startup circuit for switching mode power supplies

A synchronous rectification circuit for a power converter includes a power switch coupled to a transformer and an output capacitor and a switching control circuit configured to provide a control signal to the power switch in response to a first state and a second state of the voltage across the power switch. In the switching control circuit, the second state is determined prior to the first state is determined. In an embodiment, the switching control circuit includes a voltage comparing unit configured to act in response to the first and second inputs. The voltage comparing unit is also configured to output a logic signal according to the voltage difference between the sensed voltage drop across the power switch and a reference threshold voltage. A logic processing circuit is coupled to the voltage comparing unit and configured to provide the first state and the second state of the voltage across the power switch.

A startup circuit for a switching-mode power supply (SMPS) includes a first voltage detector configured to trigger the switching-mode power supply from a startup mode to a normal operation mode when an input supply voltage exceeds a first threshold voltage, a current consumption in the first voltage detector in the startup mode being determined by a reverse leakage current of a diode. A feedback circuit is coupled to the first voltage detector and being capable of maintaining a positive feedback loop with a current consumption of no more than a microampere. A second voltage detector is coupled to the first voltage detector and the feedback circuit, and is configured to trigger the switching-mode power supply to switch from the normal operation mode to the startup mode when the input supply voltage is below a second threshold voltage.

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Shanghai, China

Qiang Zong