Semiconductor device for power supply control and power supply device, and discharging method for X capacitor

Abstract

The invention provides a semiconductor device for power supply control and a power supply device, and a discharging method for an X capacitor. The invention aims to reduce the circuit scale of the circuit which performs discharging of the X capacitor and to reduce the power consumption and the chip size in the semiconductor device for control forming an insulated direct-current power supply device. The semiconductor device for power supply control includes: a high-voltage input start terminal (HV) to which alternating-current voltage of AC input or voltage rectified in a diode bridge is input;a plurality of voltage comparison circuits (CMP1, CMP2) which connect input terminals to the high-voltage input start terminal; a timer circuit (TMR) which starts to measure a predetermined time at atiming of rising and / or falling of output of the plurality of voltage comparison circuits; and a discharging unit (Rd, Sd) between the high-voltage switching element (S0) and a ground point, whereinthe discharging unit is made conductive when the predetermined time is measured by the timer circuit.

Description

technical field [0001] The present invention relates to a semiconductor device for power supply control, and particularly relates to a technology effectively used for a semiconductor device for primary side control constituting an isolated DC power supply device including a transformer for voltage conversion. Background technique [0002] In the DC power supply device, there is an isolated AC power supply device composed of a diode bridge circuit that rectifies the AC power supply, and a DC-DC converter that steps down the DC voltage rectified by the current and converts it into a DC voltage of a desired potential. -DC converter. [0003] In an isolated AC-DC converter, an X capacitor is generally connected between the AC terminals in order to attenuate normal-mode noise, and in order to quickly discharge the charge remaining in the X capacitor when the plug is pulled out from the outlet, and X A resistor for discharging is connected in parallel to the capacitor. [0004] ...

AI Technical Summary

Problems solved by technology

However, in the invention described in Patent Document 3, in the standby mode, the internal power supply circuit, the circuit for starting the IC, the circuit for controlling the start-up, the discharge circuit of the X capacitor, the reference voltage circuit, and the bias circuit are operated. , so there is a problem of insufficient low power consumption during standby

However, in order to reduce power consumption, if the operation of the discharge circuit of the X capacitor is stopped in the standby mode, there is a problem that the discharge of the X capacitor cannot be detected when the plug is pulled out in the standby mode.

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