Alternating current (AC) to direct current (DC) converter device

1. An alternating current (AC) to direct current (DC) converter device, comprising:

an AC-to-DC converter circuit adapted to receive and perform an AC-to-DC conversion on an AC power so as to output a DC bus voltage;

a step-down DC converter circuit coupled electrically to said AC-to-DC converter circuit to receive the DC bus voltage therefrom, and performing a step-down conversion on the DC bus voltage so as to output a main power voltage;

a controller;

a first standby power converter circuit coupled electrically to said step-down DC converter circuit to receive the main power voltage therefrom, and including a first switch that is coupled electrically to said controller, said first standby converter circuit performing a step-down conversion on the main power voltage so as to output a first standby DC voltage when said controller performs a pulse-width modulation (PWM) control on said first switch; and

a second standby power converter circuit coupled electrically to said AC-to-DC converter circuit to receive the DC bus voltage therefrom, and including a second switch that is coupled electrically to said controller, said second standby power converter circuit performing a step-down conversion on the DC bus voltage to output a second standby DC voltage when said controller performs a PWM control on said second switch;

wherein said controller controls said second switch to operate in a non-conducting state and performs PWM control on said first switch when said step-down DC converter circuit operates, and controls said first switch to operate in a non-conducting state and performs PWM control on said second switch when said step-down DC converter circuit stops operating.

2. The AC-to-DC converter device as claimed in claim 1 , wherein said step-down DC converter circuit and said first standby power converter circuit operate when said AC-to-DC converter device operates in a normal mode, and said second standby power converter circuit operates when said AC-to-DC converter device operates in a standby mode.

3. The AC-to-DC converter device as claimed in claim 1 , wherein said first standby power converter circuit is a buck DC-to-DC converter circuit that includes said first switch, an inductor, a diode, a capacitor, and a load resistor connected in parallel to said capacitor, a first terminal of said inductor being electrically coupled to a first terminal of said first switch, a second terminal of said inductor being electrically coupled to a first junction of said capacitor and said load resistor, a second terminal of said first switch being electrically coupled to said step-down DC power converter circuit for receiving the main power voltage therefrom, a cathode of said diode being electrically coupled to said first terminal of said first switch, an anode of said diode being electrically coupled to a second junction of said capacitor and said load resistor; and

wherein said second standby power converter circuit is a flyback DC-to-DC converter circuit that includes said second switch, a transformer, said diode, said capacitor and said load resistor, a first terminal of a primary winding of said transformer being coupled electrically to said AC-to-DC converter circuit for receiving the DC bus voltage therefrom, a second terminal of said primary winding being electrically coupled to a first terminal of said second switch, a second terminal of said second switch is grounded, a secondary winding of said transformer serving as said inductor.

4. The AC-to-DC converter device as claimed in claim 1 , wherein said first switch is a low-voltage MOSFET switch, and said second switch is a high-voltage MOSFET switch.

5. The AC-to-DC converter device as claimed in claim 4 , wherein said step-down DC converter circuit is a half-bridge logical link control (LLC) resonant converter circuit including a third switch and a fourth switch that are series connected, and the AC-to-DC converter device further comprises a PWM signal generator coupled electrically to said third and fourth switches, and generating two PWM signals opposite in phase for respectively controlling operation of said third and fourth switches.