OVER-CURRENT DETECTOR

• US 3,679,964 A
• Filed: 10/04/1971
• Issued: 07/25/1972
• Est. Priority Date: 10/04/1971
• Status: Expired due to Term

• Current Assignee: John R. Nowell
• Original Assignee: John R. Nowell
• Inventors: Nowell, John R.
• Primary Examiner(s): Pellinen, A. D.
• Application Number:
  US05/186,122
• Time in Patent Office: 295 Days
• Field of Search: 321/2,11,14 323/9,22SC
• US Class Current: 361/18
• CPC Class Codes: H02H 7/12 for static converters or rectifiers for discharge lamp power supplies using static converters H05B41/2851, H05B41/2921, H05B41/2981
• CPC Class Codes: H02H 7/1213 for DC-DC converters

Abstract

An over-current detector monitors the current delivered by a switching regulator and provides a signal for disabling the switching regulator when the current exceeds a threshold value. The threshold value is determined by the value of the output voltage from the switching regulator.

Claims

1. An over-current detector for use with a switching regulator which includes a transformer having a primary winding and a secondary winding, said detector comprising:

a first transistor having a base, a collector and an emitter;

first, second, third and fourth reference potentials;

first, second and third resistors, said first resistor being connected between said first potential and said collector of said first transistor, said second resistor being connected between said second potential and said base of said first transistor;

first and second diodes each havinG an anode and a cathode, said cathode of said first diode being connected to said base of said first transistor, said third resistor being connected between said third potential and said anode of said first diode, said anode of said second diode being connected to said anode of said first diode, said secondary of said transformer being connected between said second potential and said cathode of said second diode;

a capacitor, said capacitor being connected between said second potential and said base of said first transistor;

said fourth potential being coupled to said emitter of said first transistor; and

an output lead, said output lead being coupled to said collector of said first transistor;

2. An over-current detector as defined in claim 1, including:

a second transistor having a base, a collector and an emitter; and

a fourth resistor, said fourth resistor being connected between said second potential and said emitters of said first and said second transistors, said base of said second transistor being coupled to said fourth potential, said collector of said second transistor being connected to said first potential.

3. An over-current detector as defined in claim 2, including:

a third transistor having a base, a collector and an emitter, said base of said third transistor being connected to said output lead, said emitter of said third transistor being connected to said first potential;

a controlled rectifier having an anode, a cathode and a gate, said gate of said rectifier being coupled to said collector of said third transistor, said cathode of said rectifier being connected to said second potential;

a fifth resistor, said fifth resistor being connected between said first potential and said anode of said rectifier; and

a signal-output terminal, said signal-output terminal being coupled to said anode of said rectifier.

4. An over-current detector for use with a switching regulator which includes first and second voltage-output terminals and a transformer having a secondary winding, said detector comprising:

first and second transistors each having a base, a collector and an emitter;

first, second and third reference potentials;

first, second, third and fourth resistors, said first resistor being connected between said first potential and said collector of said first transistor, said second resistor being connected between said second potential and said base of said first transistor;

a voltage divider network having first and second input terminals and an output terminal, said first input terminal of said network being connected to said first output terminal of said regulator, said second input terminal of said network being connected to said second output terminal of said regulator, said output terminal of said network being connected to said base of said second transistor, said second output terminal of said regulator being connected to said second potential;

first and second diodes each having an anode and a cathode, said cathode of said first diode being connected to said base of said first transistor, said third resistor being connected between said third potential and said anode of said first diode, said anode of said second diode being connected to said anode of said first diode, said secondary of said transformer being connected between said second potential and said cathode of said second diode;

a capacitor, said capacitor being connected between said second potential and said base of said first transistor, said fourth resistor being connected between said second potential and said emitters of said first and said second transistors, said collector of said second transistor being connected to said first potential; and

an output lead, said output lead being coupled to said collector of said first transistor.

5. An over-current detector as defined in claim 4 including:

a third transistor having a base, a collector and an emitter, said base of said third transistor beinG connected to said output lead, said emitter of said third transistor being connected to said first potential;

a controlled rectifier having an anode, a cathode and a gate, said gate of said rectifier being coupled to said collector of said third transistor, said cathode of said rectifier being connected to said second potential;

a fifth resistor, said fifth resistor being connected between said first potential and said anode of said rectifier; and

a signal output-terminal, said signal-output terminal being coupled to said anode of said rectifier.

6. An over-current detector as defined in claim 4, including:

a switch having first and second terminals;

fifth and sixth resistors, said first terminal of said switch being connected to said third potential, said sixth resistor being connected between said second terminal of said switch and said anode of said first diode;

a third transistor having a base, a collector and an emitter, said base of said third transistor being connected to said output lead, said emitter of said third transistor being connected to said first potential;

a controlled rectifier having an anode, a cathode and a gate, said gate of said rectifier being coupled to said collector of said third transistor, said cathode of said rectifier being connected to said second potential, said fifth resistor being connected between said first potential and said anode of said rectifier; and

a signal-output terminal, said signal-output terminal being coupled to said anode of said rectifier.

7. An over-current detector for use with a switching regulator which includes first and second voltage-input terminals, first and second voltage-output terminals and a transformer having a secondary winding, said detector comprising:

first and second transistors each having a base, a collector and an emitter;

first and second reference potentials, said collector of said second transistor being connected to said first potential;

a voltage divider network having first and second input terminals and an output terminal, said first input terminal of said network being connected to said first output terminal of said regulator, said second input terminal of said network being connected to said second output terminal of said regulator and to said second input terminal of said regulator, said output terminal of said network being connected to said base of said second transistor, said second output terminal of said regulator being connected to said second potential;

first, second, third and fourth resistors, said first resistor being connected between said first potential and the said collector of said first transistor, said second resistor being connected between said second potential and said base of said first transistor;

first and second diodes each having an anode and a cathode, said cathode of said first diode being connected to said base of said first transistor, said third resistor being connected between said anode of said first diode and said first input terminal of said switching regulator, said anode of said second diode being connected to said anode of said first diode, said secondary winding of said transformer being connected between said second potential and said cathode of said second diode;

a capacitor, said capacitor being connected between said second potential and said base of said first transistor, said fourth resistor being connected between said second potential and said emitters of said first and said second transistors; and

an output lead, said output lead being coupled to said collector of said first transistor.

8. An over-current detector as defined in claim 7 including:

a third transistor having a base, a collector and an emitter, said base of said third transistor being connected to said output lead, said emitter of said third transistor being connected to said first potential;

a controlled rectifier having an anode, a cathode and a gate, said gate of said rectifier being coUpled to said collector of said third transistor, said cathode of said rectifier being connected to said second potential;

a fifth resistor, said fifth resistor being connected between said first potential and said anode of said rectifier; and

a signal-output terminal, said signal-output terminal being coupled to said anode of said rectifier.

9. An over-current detector as defined in claim 7 including:

a switch having first and second terminals; and

a sixth resistor, said first terminal of said switch being connected to said first input terminal of said regulator, said sixth resistor being connected between said second terminal of said switch and said anode of said first diode.

10. An over-current detector as defined in claim 7 including:

a switch having first and second terminals;

fifth and sixth resistors, said first terminal of said switch being connected to said first input terminal of said regulator, said sixth resistor being connected between said second terminal of said switch and said anode of said first diode;

a third transistor having a base, a collector and an emitter, said base of said third transistor being connected to said output lead, said emitter of said third transistor being connected to said first potential;

a controlled rectifier having an anode, a cathode and a gate, said gate of said rectifier being coupled to said collector of said third transistor, said cathode of said rectifier being connected to said second potential, said fifth resistor being connected between said first potential and said anode of said rectifier; and

a signal-output terminal, said signal-output terminal being coupled to said anode of said rectifier.