SWITCHING POWER SUPPLY DEVICE

To provide a current resonant half-bridge type switching power supply device in which a resonance voltage signal generating section or a resonance current signal generating section can be configured in a compact and inexpensive manner.SOLUTION: In a switching power supply device 10, a resonating operation monitor circuit 34 comprises: a voltage drop capacitor 36 of which one end is connected to one end of a resonance capacitor 26; and a resonance voltage signal generating section 38(1) and resonance current signal generating sections 40(1) and 40(2) connected between the other end of the voltage drop capacitor and a ground line 18. The resonance voltage signal generating section consists of a series circuit of signal generating capacitors 42a and 42b and outputs a resonance voltage signal Sv(1). The resonance current signal generating sections consist of a series circuit of a current separation capacitor 44a and a current/voltage conversion resistor 44b and output resonance current signals Si(1) and Si(2). A capacity of the voltage drop capacitor is smaller than a capacity of the resonance capacitor, and a voltage generated in the other end of the voltage drop capacitor is set to be equal to or lower than 50 V.SELECTED DRAWING: Figure 1 【課題】共振電圧信号発生部又は共振電流信号発生部はコンパクトで安価に構成できる電流共振型ハーフブリッジ方式のスイッチング電源装置を提供する。【解決手段】スイッチング電源装置１０において、共振動作監視回路３４は、一端が共振用コンデンサ２６の一端に接続された降圧用コンデンサ３６と降圧用コンデンサの他端とグランドライン１８との間に接続された共振電圧信号発生部３８（１）及び共振電流信号発生部４０（１）、４０（２）を備える。共振電圧信号発生部は、信号生成用コンデンサ４２ａ、４２ｂの直列回路で成り、共振電圧信号Sv（１）を出力する。共振電流信号発生部は、分流用コンデンサ４４ａと電流電圧変換用抵抗４４ｂとの直列回路で成り共振電流信号Ｓｉ（１）、Ｓｉ（２）を出力する。降圧用コンデンサの容量は、共振用コンデンサの容量よりも小さく、降圧用コンデンサの他端に発生する電圧が５０Ｖ以下になるように設定される。【選択図】図１