Control circuit for controlling a current in an electromagnetic coil with a duty ratio which is adjusted in response to variation of a power source voltage

摘要

In a control circuit for controlling a coil current flowing in an electromagnetic coil (21a) connected to a power source (73), a current processing circuit (72, 75, 76, 77) is connected to the power source to process the coil current into a pulse current with a duty ratio. For adjusting the duty ratio in response to variation of a voltage of the power source, a ratio adjusting circuit (79, 80, 81) is connected to the power source and the current processing circuit. The electromagnetic coil is included in a displacement control valve for varying a displacement of a variable displacement compressor.