POWER AMPLIFIER

PROBLEM TO BE SOLVED: To further increase a switching frequency of a switching element in an output switching circuit.SOLUTION: A power amplifier 1 includes a power supply circuit 3, a current detector 4 and output switching circuits 5. A DC power supply in the power supply circuit 3 supplies a driving current to respective excitation coils of three phases in an AC-synchronized servo motor. Each of the output switching circuits 5 consists of a first switching element connected between the positive polarity side of the DC power supply and the excitation coil and a second switching element connected between the negative polarity side of the DC power supply and the excitation coil. Each of the switching circuits 5 of two phases, i.e. U and V phases, includes a switching element driving circuit 10 for repeatedly supplying a control signal to the switching element by a predetermined switching frequency in accordance with a difference between a target current amount based on a moving command and a detected current amount detected by the current detector 4 so that either one of the switching elements is conducted correspondingly to the polarity of the driving current supplied to the excitation coils. 【課題】出力スイッチング回路のスイッチング素子のスイッチング周波数をより高くする。【解決手段】パワーアンプ１は、電源回路３と電流検出器４と出力スイッチング回路５を有する。電源回路３の直流電源は、交流同期サーボモータの三相各相の励磁コイルに駆動電流を供給する。出力スイッチング回路５は、直流電源の正極側と励磁コイルとの間に設けられる第１のスイッチング素子と直流電源の負極側と励磁コイルとの間に設けられる第２のスイッチング素子とでなる。Ｕ相とＶ相の２相の各スイッチング回路５は、移動指令に従う目標電流量と電流検出器４で検出される検出電流量との差に応じて制御信号を励磁コイルに供給される駆動電流の極性に対応してスイッチング素子の何れか一方が導通するようにスイッチング素子に所定のスイッチング周波数で繰返し供給するスイッチング素子駆動回路１０とを含んでなる。【選択図】図１