A zero-crossing detection circuit can include: a state judging circuit that generates a judging signal based on whether a body diode of a synchronous power switch is conducting when the synchronous power switch is off; a regulation voltage generator that reduces a regulation voltage when the judging signal indicates that the body diode is conducting, and increases the regulation voltage when the judging signal indicates that the body diode is not conducting, where a detection voltage includes a sum of the regulation voltage and a voltage at a first terminal of the synchronous power switch; and a comparison circuit that compares the detection voltage against a voltage at a second terminal of the synchronous power switch, and generates a zero-crossing detection signal that is activated to turn off the synchronous power switch when the detection voltage equals the voltage at the second terminal of the synchronous power switch.

A power supply system includes at least one power supply module and at least one redundant power supply module. A power supply module may include a charging resistor in parallel with an OR-ing device to keep all filter capacitors charged as long as at least one power supply module remains operational. This may avoid current spikes at turn on and may enable the redundant module to turn on without using soft start.

Disclosed is a voltage reference buffer circuit including a first, second, third, and fourth bias generators and a first, second, third, and fourth driving components. The first, second, third, and fourth bias generators generate bias voltages to control the first, second, third, and fourth driving components respectively. The first, second, third, and fourth driving components are coupled in sequence, wherein the first and second driving components are different types of transistors and jointly output a first reference voltage, the third and fourth driving components are different types of transistors and jointly output a second reference voltage, and the group of the first and second driving components is separated from the group of the third and fourth driving components by a resistance load.

Disclosed is a voltage reference buffer circuit including a first, second, third, and fourth bias generators and a first, second, third, and fourth driving components. The first, second, third, and fourth bias generators generate bias voltages to control the first, second, third, and fourth driving components respectively. The first, second, third, and fourth driving components are coupled in sequence, wherein the first and second driving components are different types of transistors and jointly output a first reference voltage, the third and fourth driving components are different types of transistors and jointly output a second reference voltage, and the group of the first and second driving components is separated from the group of the third and fourth driving components by a resistance load.

A constant voltage circuit amplifies an error between a reference voltage and an output voltage by an operational amplifier, and controls a load current based on the amplified voltage so that the output voltage becomes a constant voltage. The constant voltage circuit includes voltage detector means that detects only AC components of the output voltage limited to a predetermined band and outputs a detected voltage; voltage amplifier means that amplifies AC components of the detected voltage and outputs an amplified voltage; judgment means that outputs a judgment signal indicating whether or not the amplified voltage equal to or larger than a predetermined threshold; and controller means configured to increase a current value of the constant current source included in the operational amplifier, based on the judgment signal, thereby temporarily increasing a current consumption of the operational amplifier.

A constant voltage circuit amplifies an error between a reference voltage and an output voltage by an operational amplifier, and controls a load current based on the amplified voltage so that the output voltage becomes a constant voltage. The constant voltage circuit includes voltage detector means that detects only AC components of the output voltage limited to a predetermined band and outputs a detected voltage; voltage amplifier means that amplifies AC components of the detected voltage and outputs an amplified voltage; judgment means that outputs a judgment signal indicating whether or not the amplified voltage equal to or larger than a predetermined threshold; and controller means configured to increase a current value of the constant current source included in the operational amplifier, based on the judgment signal, thereby temporarily increasing a current consumption of the operational amplifier.

Provided is a circuit structure for suppressing surge current, which includes a surge current suppression judgment circuit, a switching control circuit and a self-boosting regulating circuit. An output end of the surge current suppression judgment circuit is connected with the switching control circuit. An output end of the switching control circuit is connected with the self-boosting regulating circuit. The switching control circuit and the self-boosting regulating circuit are both connected with a current input end Vin. An output end of the self-boosting regulating circuit is connected with an input end of the surge current suppression judgment circuit. The output end of the self-boosting regulating circuit is an output end Vout of the whole circuit structure for suppressing surge current.

An alternating-current (AC) voltage regulator including an input, an isolated power supply, a control circuit, an amplifier, and an output. The input is configured to receive an input voltage. The isolated power supply is configured to receive the input voltage and output a direct-current (DC) signal isolated from the input voltage. The control circuit is configured to receive a portion of the input voltage, adjust the portion of the input voltage, and output the adjusted voltage. The amplifier is configured to receive the isolated DC signal, the adjusted voltage, and a feedback loop, and output a differential signal. The output is configured to add the differential signal to the input voltage resulting in a regulated voltage, and output the regulated voltage.

A driver circuit for controlling a P-channel MOSFET includes a first voltage divider connected to a source terminal of the P-channel MOSFET, a first sub-transistor including a first collector terminal, a first emitter terminal and a first base terminal, the first collector terminal is connected to the first voltage divider, a second sub-transistor including a second collector terminal, a second emitter terminal and a second base terminal, the second emitter terminal is connected to a gate terminal of the P-channel MOSFET, and the second base terminal is connected to a first connection node, a third sub-transistor including a third collector terminal, a third emitter terminal and a third base terminal, the third emitter terminal is connected to the second emitter terminal, and the third collector terminal is connected to a ground, and a first resistor connected between the second collector terminal and the second emitter terminal.

An alternating-current (AC) voltage regulator including an isolated power supply, a control circuit, an amplifier, and an output. The isolated power supply is configured to receive an input voltage and output a direct-current (DC) signal isolated from the input voltage. The control circuit is configured to adjust a portion of the input voltage, and output an adjusted voltage. The amplifier is configured to output a differential signal. The differential signal is based on at least one selected from a group consisting of the isolated DC signal, the adjusted voltage, and a feedback loop. The output is configured to add the differential signal to the input voltage resulting in a regulated voltage, and output the regulated voltage.