Abstract: A power converting apparatus includes: a reactor that includes a first terminal and a second terminal, the first terminal being connected to an alternating-current power supply; a bridge circuit that is connected to the second terminal of the reactor, includes at least one or more switching elements, and converts an alternating-current voltage output from the alternating-current power supply into a direct-current voltage; a power-supply current detecting unit that detects a current from the alternating-current power supply; and a control unit that controls ON and OFF of the switching elements depending on a current value detected by the power-supply current detecting unit, in which two or more current thresholds for controlling ON and OFF of the switching elements are included.

Abstract: A drive circuit with a zero-crossing detection function, and a zero-crossing detection method. The drive circuit comprises: a power switch transistor, a pull-up drive transistor, a first pull-down drive transistor and a second pull-down drive transistor. When an inductor starts to discharge, the first pull-down current and the second pull-down current jointly pull down a gate terminal of the power switch transistor, such that the power switch transistor is in a cut-off state; after a set time, the first pull-down current is turned off; and when the inductor ends discharging, a parasitic capacitance of the power switch transistor couples with the drop signal, and when the drop signal is detected, the pull-up current pulls up the gate terminal of the power switch transistor, such that the power switch transistor is in a turn-on state.

Abstract: The embodiments of the present invention disclose a synchronous rectification circuit and associated zero-crossing detection method. The synchronous rectification circuit includes a synchronous rectifier having a source, a drain, and at least two gates. The synchronous rectifier having N MOS cells connected in parallel, wherein N is an integer greater than or equal to 2. Through comparing a voltage signal across the drain and the source of the synchronous rectifier with a first and a second threshold voltage, part of the N MOS cells is turned off once the voltage signal is equal to the first threshold voltage, and the left part of the N MOS cells is turned off once the voltage signal is equal to the second threshold voltage. Thus, the accuracy of zero-crossing detection is improved.