Drive circuit for a bidirectional flow control valve

A drive circuit for a directional flow control valve, comprising:

• an H-type bridge circuit to control current conducted to a coil for driving a bidirectional flow control valve which assumes an intermediate position responsive to current not being conducted to said coil, where said bidirectional flow control valve is opened from said intermediate position by an increase in current of one direction to said coil, and where said bidirectional flow control valve is closed from said intermediate position by an increase in current of an opposite direction to said coil, said H-type bridge circuit including a first switch to connect a high-level power-source terminal to an end of said coil, a second switch to connect a low-level power-source terminal to an end of said coil, a third switch to connect said high-level power-source terminal to another end of said coil and a fourth switch to connect said low-level power-source terminal to another end of said coil;
• and
• a control circuit which alternatingly repeats, in a predetermined cycle, a normal-direction conduction mode to switch on said first and fourth switches and switch off said second and third switches and a reverse-direction conduction mode to switch on said second and third switches and switch off said first and fourth switches in order to control a position of said bidirectional flow control valve, wherein said control circuit executes each of said normal-direction conduction mode and said reverse-direction conduction mode during equal periods of time in said predetermined cycle to maintain said bidirectional flow control valve in said intermediate position, executes said normal-direction conduction mode longer than said reverse-direction conduction mode in said predetermined cycle so as to increase current flowing in said one direction to said coil to open said bidirectional flow control valve from said intermediate position, and executes said normal-direction conduction mode shorter than said reverse-direction conduction mode in said predetermined cycle so as to increase current flowing in said opposite direction to said coil to close said bidirectional flow control valve from said intermediate position.