Power supply apparatus with discharge circuit

摘要

A power supply apparatus is provided. The power supply apparatus includes a power conversion circuit, an AC safety capacitor and a control unit. An AC input voltage is received by an input side of the power converting circuit, and is converted to a DC output voltage. The AC safety capacitor is connected across the input side. The control unit controls the operation of the power converting circuit, where the control unit samples and holds a voltage between two terminals of the AC safety capacitor to obtain a holding voltage, and compares the holding voltage and the AC input voltage during each period of a clock signal, so as to decide to discharge electric energy stored by the AC safety capacitor according to a comparison result.

主权项

1. A power supply apparatus, comprising:
a power conversion circuit, receiving an alternating current (AC) input voltage through an input side, and converting the AC input voltage into a direct current (DC) output voltage; an AC safety capacitor, connected across the input side; and a control unit, configured to control an operation of the power conversion circuit, wherein the control unit samples and holds a voltage between two terminals of the AC safety capacitor to obtain a holding voltage, and compares the holding voltage and the AC input voltage during each period of a clock signal, so as to decide whether to execute a discharge operation to discharge electric energy stored in the AC safety capacitor according to a comparison result, wherein the control unit comprises:
a rectifier circuit, coupled to the power conversion circuit and the AC safety capacitor, and rectifying the AC input voltage to generate a rectified voltage;a sampling circuit, coupled to the rectifier circuit, and sampling a peak level of the rectified voltage to obtain a peak voltage during a first period of the clock signal;a holding circuit, coupled to the sampling circuit, and holding the peak voltage sampled by the sampling circuit during the first period at a second period following the first period, and accordingly generating the holding voltage; anda comparison circuit, coupled to an input terminal of the sampling circuit and an output terminal of the holding circuit to compare the holding voltage and the rectified voltage related to the AC input voltage, so as to output a detection signal.