Overcurrent protection circuit {8 for an object circuit{9

Claim 2

An overcurrent protection circuit connected in series between a power source terminal and a load terminal, comprising: a high-breakdown voltage transistor having a collector-emitter conductive path connected in series between the power source and the load, a high voltage breakdown diode connected in series between the load and the collector of said transistor to prevent application of a high reverse voltage to said high-breakdown voltage transistor, detection means comprising a detection resistor connected in series to the collector-emitter conductive path of said highbreakdown voltage transistor to detect a current flowing through said high-breakdown voltage transistor and control means comprising a control resistor having one terminal connected to the base of said transistor and having another terminal connected to a junction of the source and the load operatively coupled to said detection means for reducing the collector current of the transistor in response to the increase of said current detected by said detection means.

Claim 3

An overcurrent protection circuit according to claim 1, in which said detection means further includes a control transistor biased by a voltage developed across said detecting resistor for controlling the base current of said high-breakdown voltage transistor.

Claim 4

An overcurrent protection circuit according to claim 1, further including a diode connected in parallel with the series circuit comprising the collector-base path of said high-breakdown voltage transistor and said control resistor to assume a conductive condition when a positive overcurrent is applied to the load.

Claim 5

An overcurrent protection circuit comprising: a. a bipolar transistor having a pair of principal conduction electrodes having relative polarities and a control electrode, said control electrode receptive in operation of external electrical signals for controlling the conductivity characteristics of said transistor between said pair of principal conduction electrodes; b. a first diode electrically connected to one of said principal conduction electrodes and having a polarity effective to prevent high reverse voltages from being developed across said pair of principal conduction electrodes by current flowing through said first diode; c. a detection resistor connected in series in the circuit path defined between said pair of principal conduction electrodes and through said first diode for developing a voltage thereacross in response to current flowing through said circuit path; d. control means responsive to the voltage developed across said detection resistor for controlling external electrical signals applied to said control electrode to reduce current flowing through said transistor in response to an increase of the cUrrent flowing through said circuit path; e. a first resistor connected to said control electrode; f. a second resistor and a second diode connected in series; and g. means electrically connecting said first resistor, said second resistor and said second diode in series between said control electrode and said one of said principal conduction electrodes, said second diode having a polarity effective to prevent current from flowing from said one of said principal conduction electrodes to said control electrode when said first diode is conductive.

Claim 6

An overcurrent protection circuit comprising: a. a bipolar transistor having a pair of principal conduction electrodes having relative polarities and a control electrode, said control electrode receptive in operation of external electrical signals for controlling the conductivity characteristics of said transistor between said pair of principal conduction electrodes; b. a first diode electrically connected to one of said principal conduction electrodes and having a polarity effective to prevent high reverse voltages from being developed across said pair of principal conduction electrodes by current flowing through said first diode; c. a detection resistor connected in series in the circuit path defined between said pair of principal conduction electrodes and through said first diode for developing a voltage thereacross in response to current flowing through said circuit path; d. control means responsive to the voltage developed across said detection resistor for controlling external electrical signals applied to said control electrode to reduce current flowing through said transistor in response to an increase of the cUrrent flowing through said circuit path; e. a first resistor connected to said control electrode; f. a second resistor and a second diode connected in series; and g. means electrically connecting said first resistor, said second resistor and said second diode in series between said control electrode and said one of said principal conduction electrodes, said second diode having a polarity effective to prevent current from flowing from said one of said principal conduction electrodes to said control electrode when said first diode is conductive.

Claim 7

An overcurrent protection circuit according to claim 4, further comprising: a. detecting means for detecting a voltage developed in use between a first of said pair of principal conduction electrodes and said control electrode; and b. means cooperative with said detecting means for short-circuiting said control electrode and the second of said pair of principal conduction electrodes when the voltage detected by said detecting means exceeds a pre-determined value.

Claim 8

An overcurrent protection circuit connected between a power source and a load, comprising: a high-breakdown voltage transistor having a collector-emitter conductive path connected in series between the power source and the load, a high voltage breakdown diode connected in series between the load and the collector of said transistor to prevent application of a high reverse voltage to said high-breakdown voltage transistor. detection means comprising a detection resistor connected in series to the collector-emitter conductive path of said high-breakdown voltage transistor to detect a current flowing through said high-breakdown voltage transistor, control means comprising a control resistor connected to the base of said transistor and operatively coupled to said detection means for reducing the collector current of the transistor in response to the increase of said current detected by said detection means. second detection means connected to said transistor to detect a voltage across the collector-base path thereof, and a switching circuit comprising a switching element and a driving circuit of the switching element, said switching element connected to said transistor to form a short circuit across the base-emitter path thereof when an overcurrent detected by said second detection means is applied to said transistor.

Claim 9

An overcurrent protection circuit connected between a power source and a load, comprising: a high-breakdown voltage transistor having a collector-emitter conductive path connected in series between the power source and the load, a high voltage breakdown diode connected in series between the load and the collector of said transistor to prevent application of a high reverse voltage to said high-breakdown voltage transistor. detection means comprising a detection resistor connected in series to the collector-emitter conductive path of said high-breakdown voltage transistor to detect a current flowing through said high-breakdown voltage transistor, control means comprising a control resistor connected to the base of said transistor and operatively coupled to said detection means for reducing the collector current of the transistor in response to the increase of said current detected by said detection means. second detection means connected to said transistor to detect a voltage across the collector-base path thereof, and a switching circuit comprising a switching element and a driving circuit of the switching element, said switching element connected to said transistor to form a short circuit across the base-emitter path thereof when an overcurrent detected by said second detection means is applied to said transistor.