Abstract: An exemplary DC-DC converting circuit (2) includes an input terminal (20), a regulating circuit (21), a bleeder circuit (23), an output terminal (25), a voltage-controlling terminal (26), and a load (24). The input terminal, the regulating circuit, the bleeder circuit, and the output terminal are connected in series. The output terminal is grounded via the load. The voltage-controlling terminal is configured to supply a controlling voltage that controls the regulating circuit, and the bleeder circuit is configured to supply a stable divided voltage to the output terminal for output.

Abstract: An exemplary power supply circuit (20) includes a first commutating and filter circuit (21), a transformer (24), a second commutating and filter circuit (25), a transistor (27), a pulse width modulation circuit (26) outputting a control signal to control operation state of the transistor, and a feedback circuit (29). An external alternating current voltage is converted into a direct current with a cooperation operating of the transistor, the first commutating and filter circuit, the transformer, and the second commutating and filter circuit. The feedback circuit feeds an operating state of the transformer back to the pulse width modulation circuit, and the pulse width modulation circuit outputs corresponding control signals to turn on or turn off the transistor.

Abstract: An exemplary power supply circuit (20) includes a first commutating and filter circuit (21), a transformer (24), a second commutating and filter circuit (25), a transistor (27), a pulse width modulation circuit (26) outputting a control signal to control operation state of the transistor, and a feedback circuit (29). An external alternating current voltage is converted into a direct current with a cooperation operating of the transistor, the first commutating and filter circuit, the transformer, and the second commutating and filter circuit. The feedback circuit feeds an operating state of the transformer back to the pulse width modulation circuit, and the pulse width modulation circuit outputs corresponding control signals to turn on or turn off the transistor.

Abstract: An exemplary DC-DC converting circuit (2) includes an input terminal (20), a regulating circuit (21), a bleeder circuit (23), an output terminal (25), a voltage-controlling terminal (26), and a load (24). The input terminal, the regulating circuit, the bleeder circuit, and the output terminal are connected in series. The output terminal is grounded via the load. The voltage-controlling terminal is configured to supply a controlling voltage that controls the regulating circuit, and the bleeder circuit is configured to supply a stable divided voltage to the output terminal for output.