Bcd Semiconductor Manufacturing Co., Ltd.

Diodes Inc.

Shanghai Sim-bcd Semiconductor Manufacturing Co., Ltd.

Zeqiang Chen

Yajiang Zhu

Xuegang Ren

Na Liu

Siyuan Xu

Jianhua Duan

Shihai Zhu

Zhimin Hu

Chao Deng

A switch mode power supply (SMPS) system includes a rectifying circuit for coupling to an AC input voltage and a transformer having a primary winding for coupling to the rectifying circuit and a secondary winding coupled to the primary winding. The system also has a power switch coupled to the primary winding and a control circuit coupled to the power switch. The control circuit is configured to control current flow in the primary winding such that an envelope waveform formed by peak points of current pulses is in phase with the magnitude of the AC input voltage. Moreover, the SMPS system is configured to provide a constant average output current.

High power-factor control circuit and method for switched mode power supply

An SMPS received a rectified periodic input line voltage and is configure to provide a regulated output. A power switch has a constant turn-on time in a given cycle of the rectified periodic input line voltage. A maximum value of the envelope of peak currents through the power switch is determined and is compared with a reference value, and the power switch turn-on time in the next cycle is adjusted accordingly. The output of the power supply is regulated to a target output value, and the current is in phase with the periodic input line voltage, resulting in a high power factor. No sampling of the line voltage is needed to maintain the high power factor. A controller chip can have as few as five pins. Alternatively, a seven-pin controller chip can have two external resistors for selecting operations in either Boundary Conduction Mode (BCM) or Discontinuous Conduction Mode (DCM).

High power-factor control circuit and power supply

A switch mode power supply (SMPS) system includes a rectifying circuit for coupling to an AC input voltage and a transformer having a primary winding for coupling to the rectifying circuit and a secondary winding coupled to the primary winding. The system also has a power switch coupled to the primary winding and a control circuit coupled to the power switch. The control circuit is configured to control current flow in the primary winding such that an envelop waveform formed by peak points of current pulses are in phase with the magnitude of the AC input voltage. Moreover, the SMPS system is configured to provide a constant average output current.

A switch-mode power supply (SMPS) includes a transformer having a primary winding coupled to a power switch, a secondary winding for providing an output of the power supply, and a controller. The controller includes a first input terminal for receiving a current sensing signal related to a current in the primary winding, a second input terminal for receiving a feedback signal related to a current in the secondary winding, and an output terminal for providing a control signal to turn on and off the power switch. When the feedback signal is higher than a first reference voltage, the controller is configured to cause the SMPS to maintain a constant output current at a first current magnitude. When the feedback signal is lower than the first reference voltage, the controller is configured to cause the SMPS to provide a second output current at a second current magnitude higher than the first current magnitude.

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Zeqiang Chen