US3723774A - Power supply with temperature compensated current foldback - Google Patents

Power supply with temperature compensated current foldback Download PDF

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Publication number
US3723774A
US3723774A US00169686A US3723774DA US3723774A US 3723774 A US3723774 A US 3723774A US 00169686 A US00169686 A US 00169686A US 3723774D A US3723774D A US 3723774DA US 3723774 A US3723774 A US 3723774A
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Prior art keywords
power supply
transistor
current
potential
foldback
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Expired - Lifetime
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US00169686A
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English (en)
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D Rogers
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Jerrold Electronics Corp
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Jerrold Electronics Corp
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    • 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
    • G05F1/575—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 characterised by the feedback circuit

Definitions

  • ABSTRACT A power supply with overload current foldback cmploys series regulating feedback circuitry for normally controlling the base potential of a series pass transistor.
  • a current limiting transistor selectively connects the pass transistor base and power supply output terminals for reducing pass transistor drive responsive to overload conditions.
  • a temperature responsive load current sensing network is employed to maintain the peak available power supply output current constant, and a constant potential source is utilized for the foldback circuitry to 3,072,841 1/1963 Saunders .307/297 X 3,211,989 10/1965 Mintz et al ....307/297 X render the foldback characteristic independent of line 3,391,330 7/1968 Grossomehme... ..323/9 voltage variations. 3,101,442 8/1963 Darbie et a1.
  • overload protection i.e., to limit the maximum current which may be drawn from the supply by a load. Absent such structure, the load current would increase without bound as the load increases (to a short circuit in the limiting case) as the regulator elements attempt to maintain the prescribed source output voltage. If the load current becomes excessive, damage may result in power supply components,'or in the load.
  • a load current sensing impedance has heretofore been placed in series between the voltage series regulator transistor and the load, and the voltage developed across the sensing impedance (a measure of load current) selectively employed when it attainsa threshold value for preventing any further significant increase in power supply output current.
  • the mechanism typically employed for this purpose is the controlled reduction of base drive potential from the series pass transistor in the voltage regulator.
  • current foldback has heretofore been employed to quantitatively reduce output current from itsmaximum permissible level as the overload condition becomes increasingly severe.
  • Current foldback has illustratively been implemented by employing a threshold switching device which is responsive to output potential. The fault-enabled switching transistor or the like removes drive from the series current passing regulator transistor when the out put potential markedly decreases, as by the application of a short circuited load to the regulated supply.
  • an additional current limiting protective transistor has its collectoremitter principal conduction path connected between the base of the series regulator transistor and the power supply output terminal.
  • the base of the protective transistor has supplied thereto a load current dependent signal developing by the current sensing impedance, and a fixed, independently regulated potential via a suitable impedance.
  • the additional transistor responds to current overload conditions by selectively removing base drive potential from the series pass transistor to prevent the current from increasing significantly beyond its prescribed maximum value.
  • the transistor is also responsive to a decrease in supply output potential for effecting a progressive reduction in output current (current foldback).
  • the load current sensing impedance includes a temperature dependent element whose impedance varies with temperature in a manner which offsets the temperature-dependent characteristic of the base-emitter junction of the protective transistor. Accordingly, the conduction threshold for this transistor is effectively maintained constant with temperature, thus providing a maximum output current for the composite power supply which does not vary with temperature.
  • FIG. 1 schematically depicts a power supply with overload current foldback protection illustrating the principles of the present invention
  • FIG. 2 depicts the output characteristic for the FIG. 1 power supply.
  • the source of unregulated d.c. potential may illustratively comprise, for example, a transformer, diode bridge and filter capacitor, the dc potential thus exhibiting some ripple and also varying in amplitude direct with line voltage changes.
  • VOLTAGE REGULATION Voltage regulation for the FIG. 1 power supply is of conventional series regulator feedback construction, and comprises a series pass, voltage dropping regulator element 20, schematically shown as a single transistor 22.
  • the series pass member 20 may comprise plural transistors connected in a Darlington configuration;
  • the series elements 20 is operated to instantly have disposed thereacross that voltage then necessary to maintain the power supply output potential at an output terminal 58 constant.
  • the series pass transistor 22 therefore accommodates at its collector-emitter terminals the instantaneous voltage differences between that supplied by the unregulated source 10 and the desired output at the terminal 58.
  • This mode of operation is effected by obtaining a measure of supply output potential, as in a voltage divider 505254 and supplying this signal to the inverting input 41 of a difference amplifier 40.
  • a non-inverting input 42 of the difference amplifier 40 is connected to a source of fixed reference potential 47.
  • the difference amplifier may simply comprise a single transistor connected in a common emitter configuration, and the reference source 47 simply comprising a zener diode.
  • the amplifier 40 output terminal 45 (e.g., the collector of the transistor 44) is connected to the base of the series pass transistor 22.
  • one element in the voltage divider e.g., the resistance 52, is made variable such that a range of output power supply potentials can selectively provide substantially like voltages at the amplifier inputs 41 and 42.
  • I sensing impedance 27 is disposed between the series pass element and the load 56.
  • the series pass impedance includes a main load current passing, low value resistance 27 having a voltagedivider 30 through 33 connected thereacross.
  • a current limiting transistor 38 has its collector and emitter terminals respectively connected to a junction point 24 at the base of the series pass transistor 22, and to the power supply output. The base of the transistor 38 is connected to an intermediate point in the voltage divider 30-33.
  • the current flowing through the current sensing resistance 28 develops a voltage thereacross which is insufficient in amplitude to turn the transistor 38 on, that is, the voltage produced at the junction of the voltage divider resistors 30 and 31 is less than the conduction threshold for the transistor 38 (typically'some value less than a volt).
  • the transistor 38 is nonconductive and performs no circuit function.
  • the voltage developed by the resistance 28 and the voltage divider 30-33 connected thereacross reaches the conduction threshold of the transistor 38.
  • the power supply output current is thereafter prevented from substantially increasing above this value a since any such increase in current develops a larger base-emitter drive for the transistor 38, thereby increasing its collector current which flows through a resistance 18 connected from the collector to the base of the regulator transistor 22.
  • Such a current flow through resistor 18 reduces the base potential of the series pass transistor 20, thus also reducing the voltage at the emitter of transistor 22 and power supply output terminal 58.
  • the power supply output thus enters a second (quasi-constant current) operating range B wherein output voltage decreases with increasing overload while current only slightly increases.
  • the current sensing network 27 includes a temperature responsive resistance 33, e.g., a thermistor, such that the voltage division factor effected by the network 30-33 varies in a manner which compensates for the temperature variation of the transistor.
  • the input junction of the transistor 38 becomes more sensitive and, correspondingly, the voltage division factor for elements 30-33 is reduced such that less of the voltage developing across resistance 38 is coupled to the transistor base terminal. Similar compensation occurs for a temperature decrease.
  • the transistor 38 becomes conductive in response to a load current of magnitude a at any ambient temperature, the power supply thereby exhibiting a fixed break point 70.
  • the base of the transistor 38 is connected by a resistance 36 to a source of fixed potential developed, for example, by a zener diode 14 energized via a resistance 12.
  • a diode 16 may be included in series with the resistor 36; the diode I6 is not essential as described hereinbelow.
  • the power supply regulator attempts to supply an unbounded increasing amount of current in an attempt to increase the supply output voltage, following the operating region A of FIG. 2 to the right until the point 70 is reached. At this point, the current flowing through the current sensing resistor 28 is sufficient to turn the transistor 38 on as above discussed, and the supply voltage output drops (operating region B).
  • the emitter of the transistor 38 is at a potential sufficiently less than that of the zener diode 14 such that the diode 16 is conductive. Accordingly, the transistor 38 thereafter operates with a parting from the spirit and scope of the present invention.
  • series pass transistor means including first and second terminals having a main conduction path therebetween and a control terminal, a power supply output terminal, current sensing impedance means disposing intermediate a first one of said series pass main conduction terminals and said power supply output terminal, feedback amplifier means including means for comparing a measure of the output potential at said power supply output terminal with a fixed reference voltage and for supplying at said control terminal of said series pass transistor means an output potential dependent upon said comparison, an additional transistor having collector and emitter terminals thereof respectively connected to said control relatively firm base energization source (substantially the zener voltage through source impedance 36) and becomes very heavily, increasingly conductive for each further incremental output voltage decrease.
  • the transistor 38 thus draws a relatively large collector current through the resistor 18 to very significantly reduce the voltage at-the base of the series pass transistor 22.
  • the net effect of the above described regenerative-type action is the operating region C for the FIG. 1 power supply.
  • the terminal load current may simply comprise that passed by the transistor 38 the unit 38 operating at saturation to completely cut off the series pass element 20.
  • the composite FIG. 1 circuit may latch in this foldback state to require manual restarting and thereby signal a fault condition to an operator), or may be automatically restarted when the overload is removed.
  • the diode 16 renders operation of the protection transistor 38 in the overcurrent sensing mode i.e.,
  • range B) essentially independent of the current foldback supply a series impedance 12-14-16.
  • the diode is not essential, however. When the diode is notemployed, the zener l4 voltage and the resistor 36 are selected to quiescently provide a base-emitter biasing potential for transistor 38 less than its conduction threshold. Current limiting and foldback then proceed as above-described.
  • said current sensing impedance means comprising temperature responsive resistance means connected in parallel with the base-emitter junction of said additional transistor for offsetting the temperature dependent conduction threshold of said additional transistor wherein said current sensing impedance means and said temperature responsive resistance means comprise a first load current passing impedance, resistive voltage divider means connected in parallel with said current passing resistance, said voltage divider including in one branch thereof said temperature responsive resistance means.
  • series pass transistor means including first and second terminals having a main conduction path therebetween and a control terminal, a power supply output terminal, current sensing impedance means disposing intermediate a first one of said series pass main conduction terminals and said power supply output terminal, feedback amplifier means including means for comparing a measure of the output potential at said power supply output terminal with a fixed reference voltage and for supplying at said control terminal of said series pass transistor means an output potential dependent upon said comparison, an additional transistor having collector and emitter terminals thereof respectively connected to said control terminal of said series pass transistor means and said power supply output terminal, a potential source, foldback impedance means connecting the base of said additional transistor with said potential source, said cur rent sensing impedance means comprising temperature responsive resistance means connected in parallel with the base-emitter junction of said additional transistor for off-setting the temperature dependent conduction threshold of said additional transistor wherein said potential source comprises means for providing a constant output potential independent of line voltage variations further comprising a diode connected

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  • 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)
US00169686A 1971-08-06 1971-08-06 Power supply with temperature compensated current foldback Expired - Lifetime US3723774A (en)

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Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3959713A (en) * 1975-03-27 1976-05-25 Motorola, Inc. Solid state current limit circuit
US4104544A (en) * 1977-03-16 1978-08-01 The United States Of America As Represented By The Secretary Of The Interior Current limiting circuit for direct current power supplies
US4180768A (en) * 1978-07-20 1979-12-25 Tele/Resources, Incorporated Energy limiting foldback circuit for power supply
US4326245A (en) * 1981-02-23 1982-04-20 Siemens Corporation Current foldback circuit for a DC power supply
US4500830A (en) * 1981-08-18 1985-02-19 Matsushita Electric Industrial Co., Ltd. Current control circuit for a plurality of loads
US4535276A (en) * 1983-01-12 1985-08-13 Matsushita Electric Industrial Co., Ltd. Output circuit and brushless motor using the same
US4800331A (en) * 1987-02-12 1989-01-24 United Technologies Corporation Linear current limiter with temperature shutdown
DE3733889A1 (de) * 1987-10-07 1989-04-27 Philips Patentverwaltung Laengsregler
US4837653A (en) * 1987-06-26 1989-06-06 Data I/O Corporation Quasi-power measurement circuit
US4972136A (en) * 1989-11-07 1990-11-20 The United States Of America As Represented By The Secretary Of The Navy Linear power regulator with current limiting and thermal shutdown and recycle
US5041777A (en) * 1989-09-30 1991-08-20 U.S. Philips Corporation Voltage controlled and current limited power supply
US5089768A (en) * 1989-03-22 1992-02-18 Canon Kabushiki Kaisha Power source device with control of voltage change speed
DE4128679C1 (online.php) * 1991-08-29 1992-08-27 Ant Nachrichtentechnik Gmbh, 7150 Backnang, De
US5301082A (en) * 1987-05-29 1994-04-05 Stolar, Inc. Current limiter circuit
US5587649A (en) * 1994-09-30 1996-12-24 Motorola, Inc. Thermal performance matched current limiting circuit, and battery using same
US5640059A (en) * 1995-12-21 1997-06-17 Reltec Corporation Power supply system including thermal current limiting protection
US5994884A (en) * 1998-08-27 1999-11-30 The United States Of America As Represented By The Secretary Of The Navy Booster circuit for foldback current limited power supplies
EP1006422A1 (fr) * 1998-12-04 2000-06-07 Schneider Electric Industries SA Dispositif de communication comportant un circuit d'alimentation et procédé d'alimentation pour un tel dispositif
US20030174011A1 (en) * 2000-12-07 2003-09-18 Alechine Evgueni Sergeyevich Method of stabilization of operating conditions in electronic devices
US20050052797A1 (en) * 2003-09-10 2005-03-10 Yu-Hu Yan Protection device for power source and electronic device
US7336464B1 (en) * 2003-08-28 2008-02-26 National Semiconductor Corporation Power limiting circuit
US20080061752A1 (en) * 2006-09-13 2008-03-13 Linear Technology Corporation Programmable constant power foldback
US7408755B1 (en) 2007-06-12 2008-08-05 Honeywell International Inc. Advanced inrush/transient current limit and overload/short circuit protection method and apparatus for DC voltage power supply
US20090039858A1 (en) * 2005-04-18 2009-02-12 Rohm Co., Ltd. Direct current power supply device
US20090273323A1 (en) * 2007-09-13 2009-11-05 Freescale Semiconductor, Inc Series regulator with over current protection circuit
US20100020842A1 (en) * 2008-07-28 2010-01-28 Finesse Solutions, Llc. System and method for temperature measurement
US20120314782A1 (en) * 2011-06-10 2012-12-13 Didier Boivin Powerline Control Interface in CENELEC (EU) A-D Bands Frequency and Amplitude Modulation Transmitter

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2509133A1 (fr) * 1981-07-09 1983-01-14 Devilder Julien Dispositif d'hamecon pour la peche au vif

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3072841A (en) * 1958-11-24 1963-01-08 Gen Precision Inc Transistor network voltage regulator
US3101442A (en) * 1959-12-15 1963-08-20 Hewlett Packard Co Transistorized direct-voltage regulated power supply
US3211989A (en) * 1961-12-07 1965-10-12 Trw Inc Voltage regulator employing a nonlinear impedance and negative temperature coefficient impedance to prevent leakage current
US3345554A (en) * 1964-08-28 1967-10-03 Technipower Inc Regulating system with periodically inhibted forld-back characteristic
US3391330A (en) * 1965-10-19 1968-07-02 Gen Electric Direct current power supplies with overload protection
US3426265A (en) * 1965-10-29 1969-02-04 Amp Inc Over-current short circuit protection circuit
US3527997A (en) * 1968-06-21 1970-09-08 Forbro Design Corp Regulated power supply with fold-back overload current characteristic and overvoltage protection

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3072841A (en) * 1958-11-24 1963-01-08 Gen Precision Inc Transistor network voltage regulator
US3101442A (en) * 1959-12-15 1963-08-20 Hewlett Packard Co Transistorized direct-voltage regulated power supply
US3211989A (en) * 1961-12-07 1965-10-12 Trw Inc Voltage regulator employing a nonlinear impedance and negative temperature coefficient impedance to prevent leakage current
US3345554A (en) * 1964-08-28 1967-10-03 Technipower Inc Regulating system with periodically inhibted forld-back characteristic
US3391330A (en) * 1965-10-19 1968-07-02 Gen Electric Direct current power supplies with overload protection
US3426265A (en) * 1965-10-29 1969-02-04 Amp Inc Over-current short circuit protection circuit
US3527997A (en) * 1968-06-21 1970-09-08 Forbro Design Corp Regulated power supply with fold-back overload current characteristic and overvoltage protection

Cited By (32)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3959713A (en) * 1975-03-27 1976-05-25 Motorola, Inc. Solid state current limit circuit
US4104544A (en) * 1977-03-16 1978-08-01 The United States Of America As Represented By The Secretary Of The Interior Current limiting circuit for direct current power supplies
US4180768A (en) * 1978-07-20 1979-12-25 Tele/Resources, Incorporated Energy limiting foldback circuit for power supply
US4326245A (en) * 1981-02-23 1982-04-20 Siemens Corporation Current foldback circuit for a DC power supply
US4500830A (en) * 1981-08-18 1985-02-19 Matsushita Electric Industrial Co., Ltd. Current control circuit for a plurality of loads
US4535276A (en) * 1983-01-12 1985-08-13 Matsushita Electric Industrial Co., Ltd. Output circuit and brushless motor using the same
US4800331A (en) * 1987-02-12 1989-01-24 United Technologies Corporation Linear current limiter with temperature shutdown
US5301082A (en) * 1987-05-29 1994-04-05 Stolar, Inc. Current limiter circuit
US4837653A (en) * 1987-06-26 1989-06-06 Data I/O Corporation Quasi-power measurement circuit
DE3733889A1 (de) * 1987-10-07 1989-04-27 Philips Patentverwaltung Laengsregler
US5089768A (en) * 1989-03-22 1992-02-18 Canon Kabushiki Kaisha Power source device with control of voltage change speed
US5041777A (en) * 1989-09-30 1991-08-20 U.S. Philips Corporation Voltage controlled and current limited power supply
US4972136A (en) * 1989-11-07 1990-11-20 The United States Of America As Represented By The Secretary Of The Navy Linear power regulator with current limiting and thermal shutdown and recycle
DE4128679C1 (online.php) * 1991-08-29 1992-08-27 Ant Nachrichtentechnik Gmbh, 7150 Backnang, De
US5587649A (en) * 1994-09-30 1996-12-24 Motorola, Inc. Thermal performance matched current limiting circuit, and battery using same
US5640059A (en) * 1995-12-21 1997-06-17 Reltec Corporation Power supply system including thermal current limiting protection
US5994884A (en) * 1998-08-27 1999-11-30 The United States Of America As Represented By The Secretary Of The Navy Booster circuit for foldback current limited power supplies
EP1006422A1 (fr) * 1998-12-04 2000-06-07 Schneider Electric Industries SA Dispositif de communication comportant un circuit d'alimentation et procédé d'alimentation pour un tel dispositif
US20030174011A1 (en) * 2000-12-07 2003-09-18 Alechine Evgueni Sergeyevich Method of stabilization of operating conditions in electronic devices
US7336464B1 (en) * 2003-08-28 2008-02-26 National Semiconductor Corporation Power limiting circuit
US20050052797A1 (en) * 2003-09-10 2005-03-10 Yu-Hu Yan Protection device for power source and electronic device
US7215524B2 (en) * 2003-09-10 2007-05-08 Benq Corporation Protection device for power source and electronic device
US20090039858A1 (en) * 2005-04-18 2009-02-12 Rohm Co., Ltd. Direct current power supply device
US7538528B2 (en) * 2006-09-13 2009-05-26 Linear Technology Corporation Constant power foldback mechanism programmable to approximate safe operating area of pass device for providing connection to load
US20080061752A1 (en) * 2006-09-13 2008-03-13 Linear Technology Corporation Programmable constant power foldback
US7408755B1 (en) 2007-06-12 2008-08-05 Honeywell International Inc. Advanced inrush/transient current limit and overload/short circuit protection method and apparatus for DC voltage power supply
US20090273323A1 (en) * 2007-09-13 2009-11-05 Freescale Semiconductor, Inc Series regulator with over current protection circuit
US8174251B2 (en) * 2007-09-13 2012-05-08 Freescale Semiconductor, Inc. Series regulator with over current protection circuit
US20100020842A1 (en) * 2008-07-28 2010-01-28 Finesse Solutions, Llc. System and method for temperature measurement
US8092084B2 (en) * 2008-07-28 2012-01-10 Finesse Solutions, Llc System and method for temperature measurement
US20120314782A1 (en) * 2011-06-10 2012-12-13 Didier Boivin Powerline Control Interface in CENELEC (EU) A-D Bands Frequency and Amplitude Modulation Transmitter
US8699586B2 (en) * 2011-06-10 2014-04-15 Didier Boivin Powerline control interface in CENELEC (EU) A-D bands frequency and amplitude modulation transmitter

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FR2148495B3 (online.php) 1975-10-03
FR2148495A1 (online.php) 1973-03-23
AU4504372A (en) 1974-01-31

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