Patent ID: 6288881
Filing Date: 2001-09-11
Classification: H02H,H02J,Y02T

Abstract:
A flyback diode protection circuit for a battery voltage regulator, the regulator having (i) a controlled power switch in series in a circuit branch between a battery terminal and a field coil terminal for, at times, applying battery voltage to the field coil, (ii) a voltage regulating circuit having a battery voltage detection circuit connected between a battery terminal and a ground terminal and a power switch control circuit connected to the voltage detecting circuit for turning the power switch off when the battery voltage exceeds a set value and turning the power switch on when the battery voltage is less than a set value, and (iii) a flyback diode connected in series in a circuit branch between the field coil terminal and the ground terminal for conducting field coil current when the controlled power switch is open, wherein the improvement comprises:a) a power transistor interposed in series in the diode circuit branch for protecting the diode and having a control input; andb) a power transistor drive circuit having an output connected to the control input of the power transistor and an input connected to a regulator ignition terminal, the regulator ignition terminal being for electrical connection to an ignition terminal of a vehicle ignition switch for turning on the power transistor when a voltage is present at the ignition terminal of the vehicle ignition switch and for turning the power transistor off when a voltage is not present.