USH1319H - Current limit circuit for power supply regulators - Google Patents

Current limit circuit for power supply regulators Download PDF

Info

Publication number
USH1319H
USH1319H US07/671,594 US67159491A USH1319H US H1319 H USH1319 H US H1319H US 67159491 A US67159491 A US 67159491A US H1319 H USH1319 H US H1319H
Authority
US
United States
Prior art keywords
current
voltage
limit
output
switching regulator
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US07/671,594
Inventor
Thomas C. Stroup
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
US Department of Navy
Original Assignee
US Department of Navy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by US Department of Navy filed Critical US Department of Navy
Priority to US07/671,594 priority Critical patent/USH1319H/en
Assigned to NAVY, THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE SECRETARY OF THE reassignment NAVY, THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE SECRETARY OF THE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: LOCKHEED MISSILES & SPACE COMPANY, INC.
Assigned to LOCKHEED MISSILES & SPACE COMPANY, INC. reassignment LOCKHEED MISSILES & SPACE COMPANY, INC. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: STROUP, THOMAS C.
Application granted granted Critical
Publication of USH1319H publication Critical patent/USH1319H/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
    • G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
    • G05F1/565—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor
    • G05F1/569—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection
    • G05F1/573—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection with overcurrent detector

Definitions

  • This invention pertains to a method and apparatus for limiting current in a power supply.
  • Still another objective is to avoid oscillation of the output voltage.
  • a further objective is provide a highly reliable circuit.
  • An important advantage of the present invention is that the circuit uses provides a square voltage-current curve.
  • Another advantage is that the circuit uses few components.
  • a further advantage is that most components of the circuit are fairly insensitive to component tolerances or parameters.
  • Still another advantage is that oscillation is prevented.
  • FIG. 1 shows the circuit according to the invention.
  • SR--switching regulator IC e.g. Harris FG1532
  • FIG. I the circuit according to the invention.
  • the invention uses feedback to the switching regulator to maintain the output voltage V out within desired limits.
  • the output current flows through the current limit resistor R c thus providing a voltage proportional to the current at the base-emitter junction of Q 1 via CR 1 and R 2 .
  • the forward biased CR 1 voltage maintains a reverse bias on the B-E junction of Q 1 .
  • Q 1 turns on, hence turning on Q 2 , thus providing its contribution to the current limit feedback circuitry for use by the switching regulator SR.
  • R 1 is a resistor that maintains the continuous forward bias current through CR 1 .
  • R 2 provides some current limiting for the base-emitter junction of Q 1 during hard current limiting conditions and output current spikes.
  • R 3 prevents Q 2 from being driven too hard by Q 1 .
  • R 4 provides a path for leakage current from the base-collector junction of Q 2 thus helping to hold it off during normal operation.
  • Capacitor C 1 is simply a filter capacitor for the regulator output.
  • R 5 and R 6 scale the feedback signal to the power control circuit.
  • C 2 and CR2 are filters to reduce the noise to the power control circuit.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Continuous-Control Power Sources That Use Transistors (AREA)

Abstract

Most power supply regulators either cause the output voltage to drop-off gradually, or caused output oscillation upon reaching or exceeding the limit current. Current limit feedback to an error amplifier within a switching regulator is used to control the output voltage, prevent oscillation, insure that current limiting does not occur until a well-defined threshold is achieved and then steeply limit the current. The circuit uses feedback to the switching regulator to maintain the output voltage within desired limits. The output current flows through the current limit resistor Rc thus providing a voltage proportional to the current at the base-emitter junction of Q1 via CR1 and R2. During normal operation, the forward biased CR1 voltage maintains a reverse bias on the B-E junction of Q1. When the voltage across Rc exceeds the forward bias on CR1, Q1 turns on, hence turning on Q2, thus providing its contribution to the current limit feedback circuitry for use by the switching regulator.

Description

FIELD OF THE INVENTION
This invention pertains to a method and apparatus for limiting current in a power supply.
BACKGROUND OF THE INVENTION
Most prior art circuits either caused the output voltage to drop-off gradually, or caused output oscillation upon reaching or exceeding the limit current.
OBJECTIVES OF THE INVENTION
It is therefore a primary objective of the present invention to provide a circuit for regulating voltage of a power supply to provide good regulation of voltage up to a desired current limit value.
It is another objective to drop the voltage sharply above the desired current limit.
Still another objective is to avoid oscillation of the output voltage.
A further objective is provide a highly reliable circuit.
SUMMARY OF THE INVENTION
Current limit feedback to an error amplifier within a switching regulator is used to control the output current, prevent oscillation, insure that current limiting does not occur until a well-defined threshold is achieved and then steeply limit the current.
These objects of the invention and other objects, features and advantages to become apparent as the specification progresses are accomplished by the invention according to which, briefly stated, current limit feedback to an error amplifier within a switching regulator is used to control the output voltage and prevent oscillation.
LIST OF ADVANTAGES OF THE INVENTION
An important advantage of the present invention is that the circuit uses provides a square voltage-current curve.
Another advantage is that the circuit uses few components.
A further advantage is that most components of the circuit are fairly insensitive to component tolerances or parameters.
Still another advantage is that oscillation is prevented.
These and further objectives, constructional and operational characteristics, and advantages of the invention will no double be more evident to those skilled in the art from the detailed description given hereinafter with reference to the figures of the accompanying drawings which illustrate a preferred embodiment by way of non-limiting example.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the circuit according to the invention.
GLOSSARY
The following is a glossary of circuit elements as referenced and employed in the present invention.
Q1 --2N2222A transistor
Q2 --2N2907A transistor
Q3 --2N3584 transistor
Q4 --2N3584 transistor
CR1,CR2--1N414B diodes
Rc --0.249Ω resistor
R1 --1000Ω resistor
R2 --16.2Ω resistor
R3 --4.99Ω resistor
R4 --499Ω resistor
R5 --3.01kΩ resistor
R6 --499Ω resistor
R7 --90.9Ω resistor
R8 --10kΩ resistor
C1, C2 --0.01 mfd capacitors
SR--switching regulator IC, e.g. Harris FG1532
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings wherein like reference numerals are used to designate like or corresponding parts throughout the various figures thereof, there is shown in FIG. I the circuit according to the invention.
The invention uses feedback to the switching regulator to maintain the output voltage Vout within desired limits. The output current flows through the current limit resistor Rc thus providing a voltage proportional to the current at the base-emitter junction of Q1 via CR1 and R2. During normal operation, the forward biased CR1 voltage maintains a reverse bias on the B-E junction of Q1. When the voltage across Rc exceeds the forward bias on CR1, Q1 turns on, hence turning on Q2, thus providing its contribution to the current limit feedback circuitry for use by the switching regulator SR.
R1 is a resistor that maintains the continuous forward bias current through CR1. R2 provides some current limiting for the base-emitter junction of Q1 during hard current limiting conditions and output current spikes. R3 prevents Q2 from being driven too hard by Q1. R4 provides a path for leakage current from the base-collector junction of Q2 thus helping to hold it off during normal operation. Capacitor C1 is simply a filter capacitor for the regulator output.
Within the feedback circuit, R5 and R6 scale the feedback signal to the power control circuit. C2 and CR2 are filters to reduce the noise to the power control circuit.
This invention is not limited to the preferred embodiment and alternatives heretofore described, to which variations and improvements may be made, without departing from the scope of protection of the present patent and true spirit of the invention, the characteristics of which are summarized in the following claims.

Claims (1)

What is claimed is:
1. A circuit for regulating voltage in a power supply, comprising:
a power control circuit means for controlling a voltage of a power source,
a current limiting means for generating a feedback signal to said power control circuit means while limiting current to an output, and
a feedback circuit means for scaling a signal from a signal generation means to be sent to said power control circuit means.
US07/671,594 1991-03-19 1991-03-19 Current limit circuit for power supply regulators Abandoned USH1319H (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US07/671,594 USH1319H (en) 1991-03-19 1991-03-19 Current limit circuit for power supply regulators

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US07/671,594 USH1319H (en) 1991-03-19 1991-03-19 Current limit circuit for power supply regulators

Publications (1)

Publication Number Publication Date
USH1319H true USH1319H (en) 1994-06-07

Family

ID=24695155

Family Applications (1)

Application Number Title Priority Date Filing Date
US07/671,594 Abandoned USH1319H (en) 1991-03-19 1991-03-19 Current limit circuit for power supply regulators

Country Status (1)

Country Link
US (1) USH1319H (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050146315A1 (en) * 2003-12-31 2005-07-07 Burton Edward A. Regulating voltage applied to an integrated circuit and proxy frequency

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050146315A1 (en) * 2003-12-31 2005-07-07 Burton Edward A. Regulating voltage applied to an integrated circuit and proxy frequency
US7098635B2 (en) 2003-12-31 2006-08-29 Intel Corporation Regulating voltage applied to an integrated circuit and proxy frequency

Similar Documents

Publication Publication Date Title
US5570060A (en) Circuit for limiting the current in a power transistor
US6885530B2 (en) Power limiting time delay circuit
US5177431A (en) Linear programming circuit for adjustable output voltage power converters
US5666044A (en) Start up circuit and current-foldback protection for voltage regulators
EP0492117B1 (en) Current source with adjustable temperature variation
US4940930A (en) Digitally controlled current source
US4887181A (en) Circuit for temperature protection with hysteresis
EP0574646A1 (en) A circuit for controlling the maximum current in a power-MOS transistor used for driving a load connected to ground
US6822428B2 (en) Stabilized power supply unit having a current limiting function
US6713991B1 (en) Bipolar shunt regulator
US3983473A (en) Series direct-current voltage regulator
USH1319H (en) Current limit circuit for power supply regulators
US5262713A (en) Current mirror for sensing current
US4135234A (en) Saturable reactor switch control for switching regulator power supplies
US6118263A (en) Current generator circuitry with zero-current shutdown state
US4837653A (en) Quasi-power measurement circuit
US5199039A (en) Laser diode supply circuit
US3566254A (en) Series-type voltage regulator
US4572927A (en) Current limiter for telephone office signalling
US20040240133A1 (en) Laser diode protection circuit
US4419632A (en) Bias circuit for microwave FETs
GB2182788A (en) Voltage regulator circuit
JPS57155809A (en) Transistor amplifier
JPH02113314A (en) Constant voltage device
US5796241A (en) Self-excited oscillation type power supply device

Legal Events

Date Code Title Description
AS Assignment

Owner name: NAVY, THE UNITED STATES OF AMERICA, AS REPRESENTED

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:LOCKHEED MISSILES & SPACE COMPANY, INC.;REEL/FRAME:005657/0108

Effective date: 19910327

STCF Information on status: patent grant

Free format text: PATENTED CASE