Method and apparatus for controlling the current through a magnetic coil

摘要: Apparatus and method for controlling current flow through a magnetic coil actuator of solenoid valve. The the is measured by sensing voltage drop across precision resistor in series with coil. apparatus includes power switch alternately switching on off. A flyback diode coupled parallel operation during shut-off. first sensor continuously measures combined switch. second sensor, resistor, samples flowing samplings occur synchronously turn-on, are delayed predetermined time delay which long enough to allow reach steady state before sampled. Circuitry provided employing sensed signal produce whose value function resistive component impedance. Control circuitry turns at fixed frequency. control circuitry, however, adjusts duration i.e., duty cycle, as instantaneous also resistance order maintain near reference value.