US 6,288,881 B1 · Battery voltage regulator protection circuits

Abstract

A voltage regulator protecting both the regulator and the electrical system. A flyback diode is protected by an autoprotected MOSFET in series with the flyback diode and controlling it by a drive circuit connected to the vehicle ignition switch. Protection against overcurrent is provided by a resettable fuse, having a thermal protection circuit, in series with the power switch. A relay is in series with the resettable fuse. The controlled switch is controlled by the output of a voltage detector. A latching circuit holds it open as long as the circuit remains connected to the battery. Overvoltage protection is provided by a voltage detector which opens the relay if the battery voltage exceeds a pre-selected voltage. To accommodate lead-acid and maintenance-free batteries, the regulator has two input ignition terminals one of which controls the set point voltage. The resettable fuse is physically mounted in thermal connection to the power switch which switches the field.

Claims24

Dependent claims

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;
and
b) 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.

An overcurrent protection circuit for a battery voltage 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 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 diode connected in series in a circuit branch between the field coil terminal and the ground terminal for conducting field coil current when the power switch is opened, wherein the protection circuit comprises:

a) a resettable fuse including thermal protection for opening the fuse in response to heating above a selected temperature and closing the fuse when the fuse temperature falls below a selected temperature, the resettable fuse being interposed in series in the controlled power switch circuit branch between the battery terminal and the field coil terminal;
b) a controlled switch having a control input and having switched terminals connected in series with the resettable fuse and interposed in series in the controlled power switch circuit branch between the battery terminal and the field terminal;
and
c) a voltage detector having an input terminal connected between the field coil terminal and the series combination of (i) the resettable fuse and (ii) the controlled power switch, the voltage detector having an output connected to the control input of the controlled switch for opening the controlled switch when the resettable fuse is opened.

1 more element

A resettable overvoltage protection circuit for a battery voltage regulator having a (i) 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 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 diode connected in series in a circuit branch between the field coil terminal and the ground terminal for conducting field coil current when the power switch is opened, the protection circuit comprising:

a) a controlled switch having a control input and having switched terminals connected in series in the controlled power switch circuit branch between the battery terminal and the field terminal;
and
b) a voltage detector including a voltage reference circuit having a reference voltage, the voltage detector having an input terminal connected between the battery terminal and the ground terminal for applying a voltage to the voltage reference circuit and having an output terminal connected to the control input of the controlled switch for opening the controlled switch when the applied voltage exceeds the reference voltage;
and
c) a latching circuit connected to the controlled switch and to the battery terminal for holding the controlled switch open after the controlled switch is opened by the voltage detector.

2 more elements

Dependencies are inferred from the claim text.

Battery voltage regulator protection circuits

Life of this patent

Battery voltage regulator protection circuits

Life of this patent

Abstract

Claims24