Lii Semiconductor Co., Ltd.

Fulong Wang

Jie Zhang

Min Zhu

A CCM-based fly-back switching power supply circuit includes: a constant current control circuit, a sampling circuit and a peak current control circuit, wherein a sampling circuit is configured to sample the ON-time of the secondary coil to obtain its duty cycle signal D_SEC, and send the signal to a constant current control circuit; a constant current control circuit is configured to receive the duty cycle signal D_SEC, generate a voltage signal CAC from the duty cycle signal D_SEC and the preset reference voltage signal VREF, convert the voltage signal CAC and the peak current control signal VCST from the peak current control circuit into time signals, and conform a comparison on the time signals to output an adjustment signal CCOUT which is used to initiatively adjust the value of the peak current control signal VCST to cause the fly-back switching power supply circuit output a constant current.

CCM-based fly-back switching power supply circuit and control method thereof

A constant-current output control circuit includes a control module, a first resistor, a capacitor, and an error amplifier; the control module is connected to an adjustable control voltage and a detection signal, and the non-inverting input end of the error amplifier is connected to the reference voltage, the inverting input end of the error amplifier is connected to the first end of the first resistor, the output end of the error amplifier is connected to the circuit to be connected, and the first end of the capacitor is connected to the first end of the first resistor, the second end of the capacitor is connected to the output end of the error amplifier, and the second end of the first resistor is connected to the control module. The design method of the circuit is also disclosed.

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Suzhou, China

Fulong Wang