Overvoltage protection circuit for a generator regulator system

Claim 2

A motor vehicle electrical generating system for supplying direct current power at a voltage having a desired regulated value relative to a reference potential, said system comprising: an alternating current generator including an output winding and a field winding which produces voltage in said output winding when said field winding is supplied with current; a rectifier means having alternating current input terminals connected to said output winding and first and second direct current power output terminals, said first power output terminal supplying the desired value of regulated voltage to the electrical loads of said motor vehicle with said second power output terminal being connected to said reference potential; an output transistor operative between conductive and nonconductive states including emitter, collector and base electrodes; means connecting the collector-emitter circuit of said output transistor in a series circuit connection with said field winding and across said output winding for supplying current to said field winding when said output transistor is conductive; a voltage sensing circuit connected to said first and second power output terminals; means connecting said voltage sensing circuit to the base of said output transistor for developing a voltage having a first predetermined value which is operative to bias said output transistor conductive when the voltage across said first and second power output terminals is below said desired regulated value and having a second predetermined value which is operative to bias said output transistor nonconductive when the voltage across the first and second power output terminals is above said desired regulated value; a plurality of controlled rectifiers including anode, cathode and gate electrodes, means connecting the anode and cathode of each of said plurality of controlled rectifiers between said output winding and said reference potential so that said voltage produced in said output winding is shunted to said reference potential when said plurality of controlled rectifiers are gates conductive; a control transistor including collector, emitter and base electrodes, means connecting the collector-emitter circuit of said control transistor to the base of said output transistor to bias said output transistor nonconductive when said control transistor is conductive thereby deenergizing the current supply to said field winding; a time delay network inclUding a capacitor and a resistor having a predetermined time constant connected to the base-emitter circuit of said control transistor; a single controlled rectifier including anode, cathode and gate electrodes; means connecting the anode and cathode of said single controlled rectifier in a series circuit with said time delay network and across said first and second power output terminals for charging said capacitor from the voltage occuring thereacross when said single controlled rectifier is gated conductive, the voltage developed across said capacitor being discharged through said resistor and the base-emitter circuit of said control transistor to bias said control transistor conductive for a predetermined time interval; and an overvoltage sensing device connected between said first power output terminal and each of said gate electrodes of said plurality of said controlled rectifiers and said single control rectifier, said overvoltage sensing device being rendered conductive in response to a predetermined level of a high transient voltage developed in said output winding and across said first and second power output terminals so that said plurality of controlled rectifiers and said single controlled rectifier are gated conductive, whereby said high transient voltage is shunted to said reference potential and concurrently said field winding is deenergized for said predetermined time interval.

Claim 3

A motor vehicle electrical generating system for supplying direct current power at a voltage having a desired regulated value relative to a reference potential, said system comprising: an alternating current generator including a three-phase output winding and a field winding which produces three-phase alternating-current voltage in said output winding when said field winding is supplied with current; a power rectifier circuit means having alternating current input terminals connected to each phase of said output winding and positive and negative output terminals, said positive output terminal supplying said direct current power at said desired regulated value of voltage said negative output terminal being connected to said reference potential; a direct current electrical load of said motor vehicle; a conductor means connecting said electrical load across said positive and negative output terminals for supplying said direct current power to said load; an output transistor including emitter, collector, and base electrodes operative between conductive and nonconductive states; means connecting the collector-emitter circuit of said output transistor in a series connection with said field winding and across said positive and negative output terminals for supplying current to said field winding when said output transistor is conductive; a voltage sensing circuit connected to said positive and said negative output terminals; means connecting said voltage sensing circuit to the base of said output transistor for developing a voltage having a first predetermined value which is operative to bias said output transistor conductive when the voltage across said positive and negative output terminals is below said desired regulated value and having a second predetermined value which is operative to bias said output transistor nonconductive when the voltage across said positive and negative output terminals is above said desired regulated value; a group of three controlled rectifiers including anode, cathode and gate electrode; means connecting the anode and cathode of each of said three controlled rectifiers between one phase of said output winding and said reference potential so that when said group of controlled rectifiers is conductive positively poled current paths are provided from said output winding to said reference potential; a zener diode having a predetermined breakdown voltage connected between said positive output terminal and each of said gates of said group of controlled rectifiers, said zener diode gating said group of controlled rectifiers conductive when said predetermined breakdoWn voltage is developed thereacross by a high transient voltage generated in said output winding by sudden disconnection of said electrical load; a control transistor including collector, emitter and base electrodes, means connecting the collector-emitter circuit of said control transistor to the base of said output transistor to bias said output transistor nonconductive when said control transistor is conductive thereby deenergizing the current supply to said field winding; a time delay network including a capacitor and a resistor connected together and across the base-emitter circuit of said control rectifier and having a predetermined time constant; a single controlled rectifier including anode, cathode and gate electrodes; a coupling capacitor means connected between said zener diode and said gate of said single controlled rectifier whereby said single controlled rectifier is gated conductive by a triggering pulse developed across said coupling capacitor means when said predetermined breakdown voltage is developed across said zener diode and being maintained conductive thereafter by forward poled voltage applied across the anode and cathode thereof; means connecting said anode and cathode of said single controlled rectifier in series with said capacitor of said time delay network and across said positive and negative power output terminals for charging said capacitor from the voltage developed across said output terminals when said single controlled rectifier is gated conductive, the voltage developed across said capacitor rendering said single controlled rectifier nonconductive by opposing the forward poled voltage and being discharged from said capacitor through a circuit path including said resistor and the base-emitter circuit of said control transistor thereby biasing said control transistor conductive for a predetermined time interval corresponding to the time constant to said time delay network, whereby said high transient voltage is shunted from said output winding to said reference potential and concurrently said field winding is deenergized for said predetermined time interval.

Claim 4

A motor vehicle electrical generating system for supplying direct current power at a voltage having a desired regulated value relative to a reference potential, said system comprising: an alternating current generator including a three-phase output winding and a field winding which produces three-phase alternating-current voltage in said output winding when said field winding is supplied with current; a power rectifier circuit means having alternating current input terminals connected to each phase of said output winding and positive and negative output terminals, said positive output terminal supplying said direct current power at said desired regulated value of voltage said negative output terminal being connected to said reference potential; a direct current electrical load of said motor vehicle; a conductor means connecting said electrical load across said positive and negative output terminals for supplying said direct current power to said load; an output transistor including emitter, collector, and base electrodes operative between conductive and nonconductive states; means connecting the collector-emitter circuit of said output transistor in a series connection with said field winding and across said positive and negative output terminals for supplying current to said field winding when said output transistor is conductive; a voltage sensing circuit connected to said positive and said negative output terminals; means connecting said voltage sensing circuit to the base of said output transistor for developing a voltage having a first predetermined value which is operative to bias said output transistor conductive when the voltage across said positive and negative output terminals is below said desired regulated value and having a second predetermined value which is operative to bias said output transistor nonconductive when the voltage across said positive and negative output terminals is above said desired regulated value; a group of three controlled rectifiers including anode, cathode and gate electrode; means connecting the anode and cathode of each of said three controlled rectifiers between one phase of said output winding and said reference potential so that when said group of controlled rectifiers is conductive positively poled current paths are provided from said output winding to said reference potential; a zener diode having a predetermined breakdown voltage connected between said positive output terminal and each of said gates of said group of controlled rectifiers, said zener diode gating said group of controlled rectifiers conductive when said predetermined breakdoWn voltage is developed thereacross by a high transient voltage generated in said output winding by sudden disconnection of said electrical load; a control transistor including collector, emitter and base electrodes, means connecting the collector-emitter circuit of said control transistor to the base of said output transistor to bias said output transistor nonconductive when said control transistor is conductive thereby deenergizing the current supply to said field winding; a time delay network including a capacitor and a resistor connected together and across the base-emitter circuit of said control rectifier and having a predetermined time constant; a single controlled rectifier including anode, cathode and gate electrodes; a coupling capacitor means connected between said zener diode and said gate of said single controlled rectifier whereby said single controlled rectifier is gated conductive by a triggering pulse developed across said coupling capacitor means when said predetermined breakdown voltage is developed across said zener diode and being maintained conductive thereafter by forward poled voltage applied across the anode and cathode thereof; means connecting said anode and cathode of said single controlled rectifier in series with said capacitor of said time delay network and across said positive and negative power output terminals for charging said capacitor from the voltage developed across said output terminals when said single controlled rectifier is gated conductive, the voltage developed across said capacitor rendering said single controlled rectifier nonconductive by opposing the forward poled voltage and being discharged from said capacitor through a circuit path including said resistor and the base-emitter circuit of said control transistor thereby biasing said control transistor conductive for a predetermined time interval corresponding to the time constant to said time delay network, whereby said high transient voltage is shunted from said output winding to said reference potential and concurrently said field winding is deenergized for said predetermined time interval.