WO1999056373A1 - Inrush current limiting protection circuit - Google Patents

Inrush current limiting protection circuit Download PDF

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Publication number
WO1999056373A1
WO1999056373A1 PCT/FI1999/000346 FI9900346W WO9956373A1 WO 1999056373 A1 WO1999056373 A1 WO 1999056373A1 FI 9900346 W FI9900346 W FI 9900346W WO 9956373 A1 WO9956373 A1 WO 9956373A1
Authority
WO
WIPO (PCT)
Prior art keywords
current
circuit
transistor
protection circuit
control means
Prior art date
Application number
PCT/FI1999/000346
Other languages
French (fr)
Inventor
Matti Lyly
Original Assignee
Nokia Networks Oy
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 Nokia Networks Oy filed Critical Nokia Networks Oy
Priority to AU37122/99A priority Critical patent/AU3712299A/en
Publication of WO1999056373A1 publication Critical patent/WO1999056373A1/en

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/001—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection limiting speed of change of electric quantities, e.g. soft switching on or off
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/02—Details
    • H02H3/06—Details with automatic reconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H02H3/093—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current with timing means

Definitions

  • the invention relates to a protection circuit defined in the preamble of claim 1.
  • the protection circuit includes a current supply part 1, defined by a dotted line in the drawing, comprising a resistor R2 and a voltage limiting reverse biased voltage-regulator diode Dl.
  • the protection circuit further includes a current sensing part 2 comprising a current sensing resistor Rl and a bipolar transistor Ql.
  • the voltage across the current sensing resistor Rl which preferably has a resistance as low as possible, say 0.1 ⁇ , is used to limit the inrush current by utilizing the threshold voltage of the bipolar transistor Ql in such a manner that as the voltage of resistor Rl starts to rise, the threshold voltage of transistor Ql is exceeded and transistor Ql starts to conduct.
  • the conductive state of transistor Ql is further used to control a current regulating MOSFET (Metal Oxide Sulfite Field Effect Transistor) Ml.
  • MOSFET Metal Oxide Sulfite Field Effect Transistor
  • the control circuit of transistor Ml also comprises a current shut-off part 3 in which the current is shut off after a short circuit has occurred. It relies on shut-off control by transistor Q2 based on the voltage across the current regulating transistor Ml at the coupling point of resistors R3 and R4.
  • the resistance of resistor R3 is about five times that of resistor R4.
  • the purpose of capacitor Cl is to produce a delay of about 1.5 ms for the current shut-off.
  • More versatile protection circuits are also known which have more diverse characteristics than those described above.
  • a problem with known advantageous protection circuits is that in a short circuit condition the circuit is locked open and a restart can only be realized by removing the operating voltage of the circuit.
  • a problem with known more versatile protection circuits is that they cost more in addition to consuming more power.
  • An object of the invention is to eliminate the disadvantages mentioned above by providing an advantageous protection circuit which also realizes automatic attempted restart.
  • the protection circuit according to the invention is characterized by what is expressed in claim 1. Preferred embodiments of the invention are disclosed in the dependent claims.
  • the invention pertains to an inrush current limiting protection circuit comprising means for current sensing, control means for delayed initial switch-on of current when switching on the protection circuit as well as for delayed shut-off of current and setting into a trial mode when the current exceeds a predetermined short circuit limit, control means for attempting current feed in the trial mode, and switching means for switching the current.
  • the control means for the delayed initial switch-on and shut-off of current and setting into a trial mode comprises a first delay circuit
  • the control means for attempting current feed in the trial mode comprises a second delay circuit.
  • the delay circuit is implemented as an RC circuit.
  • control means for the delayed initial switch-on of current and shut-off of current and setting into a trial mode also comprises a transistor that conducts current to the sensing circuit and a transistor that conducts a decision to the subsequent control means
  • said first delay circuit comprises a series resistor and a pull-up resistor and a capacitor which is connected in parallel on the control line and is charged in the normal operating mode by said pull-up resistor and the purpose of which is to produce a delay in accordance with the rate of change of the charge status of said capacitor.
  • control means for attempting current feed in the trial mode also comprises a circuit that produces a bistable state, comprising three transistors coupled down to the negative supply voltage, a coupling point pull-up resistor between said transistors and a transistor to the base of which a control signal comes from the second delay circuit, and said second delay circuit comprises two pull-up resistors and a capacitor coupled between them.
  • the invention has the advantage that the protection circuit is simple and inexpensive to realize and that the current is automatically switched on following a short circuit.
  • Fig. 1 is a circuit diagram of an advantageous inrush current limiting protection circuit according to the prior art
  • Fig. 2 is a circuit diagram of an inrush current limiting protection circuit according to the invention
  • Fig. 3 is a timing diagram of the operation of the protection circuit in a short circuit condition.
  • Fig. 1 was discussed above in connection with the description of the prior art.
  • Fig. 2 shows an inrush current limiting protection circuit according to the invention.
  • the protection circuit includes current supply parts 4 and 5 for the gate voltage and control circuit voltage, respectively, defined by dotted lines in the drawing. Both parts 4, 5 include a resistor R6, R7 and a voltage limiting reverse biased voltage- regulator diode D2, D3.
  • the protection circuit further includes a current sensing part 6 comprising a current sensing resistor R5 and a bipolar transistor Q3.
  • the conductive state of transistor Q3 is further used to control a current regulating MOSFET (Metal Oxide Sulfite Field Effect Transistor) M2.
  • the current shut-off part of the protection circuit according to the invention comprises two portions 7, 8.
  • the current shut-off part 7,8 comprises a delay circuit 7 to produce delays for initial switch-on and current shut-off subsequent to a short circuit.
  • the change of status of transistor Q4 is delayed by resistors R8, R9 and capacitor C2 the charge status of which is changed.
  • the status is coupled on by transistor Q5.
  • the current shut-off part 7,8 comprises a second delay circuit 8 to delay the restart attempt when the short circuit has been removed.
  • Capacitor C3 between resistors RIO and Rl 1 delays the transition fed back from the previous part and previous status to the subsequent status which is conducted by transistors Q7 and Q8 to serve as a control voltage for the current regulating MOSFET M2.
  • resistor R13 and transistor Q6 realizes a so-called "hiccup mode", i.e. the function that performs the restart attempts.
  • Resistors RIO and R12 serve as pull-up resistors for transistors Q6 and Q7, respectively.
  • Transistors Q6 and Q8 are not in conduction in the initial state because the base current provided by resistor Rl 1 makes transistor Q7 conductive so that it pulls down the bases of transistors Q6 and Q8 which, as a result, are non-conductive. Thus, capacitor C3 has no charge.
  • transistor Q5 begins to conduct, capacitor C3 pulls down the base of transistor Q7, making it non-conductive so that transistors Q6 and Q8 begin to conduct.
  • the conduction of transistor Q8 stops the conduction of the MOSFET M2.
  • Transistor Q5 conducts only for a short time as the voltage across resistor R5 drops and transistor Q4 is no more conductive, which makes transistor Q5 non-conductive, too.
  • transistor Q6 As capacitor C3 is charged because of the voltage difference between transistor Q6 and resistor Rll the voltage reaches a value where transistor Q7 again begins to conduct and transistors Q6 and Q8 become non-conductive.
  • the non-conduction of transistor Q8 makes the MOSFET M2 conductive again, i.e. the current is switched on following a short circuit.
  • the switch-on of current is attempted at intervals of 90 s, for example.
  • Fig. 3 uses a time line to illustrate the operation of the protection circuit in a short circuit condition.
  • the delay following initial start-up is about 13 ms, current feed is started and a short circuit is detected. However, current feed is continued for about 3 ms whereafter the supply is cut off. The circuit waits for about 85 ms, whereafter current is again supplied, a short circuit is detected and current supply is cut off 3 ms later.

Abstract

The invention pertains to an advantageous inrush current limiting protection circuit to sense a current, switch on the current (I) in a delayed manner when the protection circuit is switched on and to shut off the current in a delayed manner and set the circuit into a trial mode when the current (I) exceeds a predetermined short circuit limit (ISC) and to control current feed attempts in the trial mode. In accordance with the invention, an advantageous RC delay circuit (R8, R9, C2) is utilized for the delayed initial switch-on and shut-off of current (I) and setting into a trial mode, and a second advantageous RC delay circuit (R11, R12, C3) is utilized for the attempted current feed in the trial mode, in addition to transistors (Q5, Q6, Q7, Q8) controlled by these. Advantages of the protection circuit according to the invention include its inexpensive structure and low power consumption.

Description

Inrush current limiting protection circuit
The invention relates to a protection circuit defined in the preamble of claim 1.
From the prior art it is known an advantageous inrush current limiting protection circuit, which is shown in Fig. 1. The protection circuit includes a current supply part 1, defined by a dotted line in the drawing, comprising a resistor R2 and a voltage limiting reverse biased voltage-regulator diode Dl. The protection circuit further includes a current sensing part 2 comprising a current sensing resistor Rl and a bipolar transistor Ql. The voltage across the current sensing resistor Rl, which preferably has a resistance as low as possible, say 0.1 Ω, is used to limit the inrush current by utilizing the threshold voltage of the bipolar transistor Ql in such a manner that as the voltage of resistor Rl starts to rise, the threshold voltage of transistor Ql is exceeded and transistor Ql starts to conduct. The conductive state of transistor Ql is further used to control a current regulating MOSFET (Metal Oxide Sulfite Field Effect Transistor) Ml. The control circuit of transistor Ml also comprises a current shut-off part 3 in which the current is shut off after a short circuit has occurred. It relies on shut-off control by transistor Q2 based on the voltage across the current regulating transistor Ml at the coupling point of resistors R3 and R4. The resistance of resistor R3 is about five times that of resistor R4. The purpose of capacitor Cl is to produce a delay of about 1.5 ms for the current shut-off.
More versatile protection circuits are also known which have more diverse characteristics than those described above.
A problem with known advantageous protection circuits is that in a short circuit condition the circuit is locked open and a restart can only be realized by removing the operating voltage of the circuit.
A problem with known more versatile protection circuits is that they cost more in addition to consuming more power.
An object of the invention is to eliminate the disadvantages mentioned above by providing an advantageous protection circuit which also realizes automatic attempted restart.
The protection circuit according to the invention is characterized by what is expressed in claim 1. Preferred embodiments of the invention are disclosed in the dependent claims. The invention pertains to an inrush current limiting protection circuit comprising means for current sensing, control means for delayed initial switch-on of current when switching on the protection circuit as well as for delayed shut-off of current and setting into a trial mode when the current exceeds a predetermined short circuit limit, control means for attempting current feed in the trial mode, and switching means for switching the current. In accordance with the invention, the control means for the delayed initial switch-on and shut-off of current and setting into a trial mode comprises a first delay circuit, and the control means for attempting current feed in the trial mode comprises a second delay circuit.
In accordance with an embodiment of the invention the delay circuit is implemented as an RC circuit.
According to an embodiment of the invention the control means for the delayed initial switch-on of current and shut-off of current and setting into a trial mode also comprises a transistor that conducts current to the sensing circuit and a transistor that conducts a decision to the subsequent control means, and said first delay circuit comprises a series resistor and a pull-up resistor and a capacitor which is connected in parallel on the control line and is charged in the normal operating mode by said pull-up resistor and the purpose of which is to produce a delay in accordance with the rate of change of the charge status of said capacitor.
According to an embodiment of the invention the control means for attempting current feed in the trial mode also comprises a circuit that produces a bistable state, comprising three transistors coupled down to the negative supply voltage, a coupling point pull-up resistor between said transistors and a transistor to the base of which a control signal comes from the second delay circuit, and said second delay circuit comprises two pull-up resistors and a capacitor coupled between them.
The invention has the advantage that the protection circuit is simple and inexpensive to realize and that the current is automatically switched on following a short circuit.
The invention is below described in detail with reference to the attached drawing in which
Fig. 1 is a circuit diagram of an advantageous inrush current limiting protection circuit according to the prior art,
Fig. 2 is a circuit diagram of an inrush current limiting protection circuit according to the invention, and Fig. 3 is a timing diagram of the operation of the protection circuit in a short circuit condition.
Fig. 1 was discussed above in connection with the description of the prior art.
Fig. 2 shows an inrush current limiting protection circuit according to the invention. The protection circuit includes current supply parts 4 and 5 for the gate voltage and control circuit voltage, respectively, defined by dotted lines in the drawing. Both parts 4, 5 include a resistor R6, R7 and a voltage limiting reverse biased voltage- regulator diode D2, D3. The protection circuit further includes a current sensing part 6 comprising a current sensing resistor R5 and a bipolar transistor Q3. The voltage across the current sensing resistor R5, which preferably has a resistance as low as possible, say 0.1 Ω, is used to limit the inrush current by utilizing the threshold voltage of the bipolar transistor Q3 in such a manner that as the voltage of resistor R5 starts to rise, the threshold voltage of transistor Q3 is exceeded and tran- sistor Q3 starts to conduct. The conductive state of transistor Q3 is further used to control a current regulating MOSFET (Metal Oxide Sulfite Field Effect Transistor) M2.
The current shut-off part of the protection circuit according to the invention comprises two portions 7, 8. First, the current shut-off part 7,8 comprises a delay circuit 7 to produce delays for initial switch-on and current shut-off subsequent to a short circuit. The change of status of transistor Q4 is delayed by resistors R8, R9 and capacitor C2 the charge status of which is changed. The status is coupled on by transistor Q5. Second, the current shut-off part 7,8 comprises a second delay circuit 8 to delay the restart attempt when the short circuit has been removed. Capacitor C3 between resistors RIO and Rl 1 delays the transition fed back from the previous part and previous status to the subsequent status which is conducted by transistors Q7 and Q8 to serve as a control voltage for the current regulating MOSFET M2. The status fed back by resistor R13 and transistor Q6 realizes a so-called "hiccup mode", i.e. the function that performs the restart attempts. Resistors RIO and R12 serve as pull-up resistors for transistors Q6 and Q7, respectively.
Let us consider, by way of example, a situation in which the current is already switched on and the load current begins to rise as the load increases. The voltage across the current sensing resistor R5 rises and the current sensing transistor Q3 and transistor Q4 begin to conduct. Transistor Q4 discharges, through resistor R8, ca- pacitor C2 which has up till now been fully charged by resistor R9. After a time corresponding to the time constant of the circuit comprised of resistors R8 and R9 and capacitor C2, capacitor C2 will have discharged to an extent where transistor Q5 starts to conduct.
Transistors Q6 and Q8 are not in conduction in the initial state because the base current provided by resistor Rl 1 makes transistor Q7 conductive so that it pulls down the bases of transistors Q6 and Q8 which, as a result, are non-conductive. Thus, capacitor C3 has no charge.
As transistor Q5 begins to conduct, capacitor C3 pulls down the base of transistor Q7, making it non-conductive so that transistors Q6 and Q8 begin to conduct. The conduction of transistor Q8 stops the conduction of the MOSFET M2. Transistor Q5 conducts only for a short time as the voltage across resistor R5 drops and transistor Q4 is no more conductive, which makes transistor Q5 non-conductive, too.
As capacitor C3 is charged because of the voltage difference between transistor Q6 and resistor Rll the voltage reaches a value where transistor Q7 again begins to conduct and transistors Q6 and Q8 become non-conductive. The non-conduction of transistor Q8 makes the MOSFET M2 conductive again, i.e. the current is switched on following a short circuit. The switch-on of current is attempted at intervals of 90 s, for example.
Fig. 3 uses a time line to illustrate the operation of the protection circuit in a short circuit condition. The delay following initial start-up is about 13 ms, current feed is started and a short circuit is detected. However, current feed is continued for about 3 ms whereafter the supply is cut off. The circuit waits for about 85 ms, whereafter current is again supplied, a short circuit is detected and current supply is cut off 3 ms later.
The invention is not limited to the embodiments described above but many modifi- cations are possible within the scope of the inventional idea defined by the claims attached hereto.

Claims

Claims
1. An inrush current limiting protection circuit comprising
- means (R5, Q3, Q4) for sensing a current (I),
- control means for delayed initial switch-on of current (I) when the protection cir- cuit is switched on and for delayed shut-off of current and setting into a trial mode when the current (I) exceeds a predetermined short circuit limit (ISc),
- control means for attempting current (I) feed in the trial mode,
- switching means (Ml, M2) for switching the current, characterized in that - the control means (7) for the delayed initial switch-on (I) and shut-off of current and setting into a trial mode comprises a first delay circuit, and
- the control means (8) for attempting current feed in the trial mode comprises a second delay circuit.
2. A protection circuit according to claim 1, characterized in that the first and second delay circuits are implemented as RC circuits.
3. A protection circuit according to claim 1 or 2, characterized in that the control means (7) for the delayed initial switch-on and shut-off of current (I) and setting into a trial mode
- further comprises a transistor (Q4) that conducts current to the current sensing means and a transistor (Q5) that conducts a decision to the subsequent control means (8), and
- said first delay circuit (9) comprises a series resistor (R8) and a pull-up resistor (R9) and a capacitor (C2) which is connected in parallel on the control line and is charged in the normal operating mode by said pull-up resistor (R9) and the purpose of which is to produce a delay in accordance with the rate of change of the charge status of said capacitor (C2).
4. A protection circuit according to claim 1, 2 or 3, characterized in that the control means (8) for attempting current feed in the trial mode
- further comprises a circuit that produces a bistable state, comprising three transis- tors (Q6, Q7, Q8) coupled down to the negative supply voltage (VΓN-), a coupling point pull-up resistor (R12) between said transistors and a transistor (Q7) to the base of which a control signal comes from the second delay circuit (10), and
- said second delay circuit (10) comprises two pull-up resistors (R10, Rll) and a capacitor (C3) coupled between them.
PCT/FI1999/000346 1998-04-29 1999-04-28 Inrush current limiting protection circuit WO1999056373A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU37122/99A AU3712299A (en) 1998-04-29 1999-04-28 Inrush current limiting protection circuit

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI980946A FI980946A (en) 1998-04-29 1998-04-29 Downstream protection circuit
FI980946 1998-04-29

Publications (1)

Publication Number Publication Date
WO1999056373A1 true WO1999056373A1 (en) 1999-11-04

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FI (1) FI980946A (en)
WO (1) WO1999056373A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7082020B2 (en) * 2001-01-16 2006-07-25 Siemens Aktiengesellschaft Electronic switching device and an operating method thereof
CN103887762A (en) * 2013-03-01 2014-06-25 上海富欣智能交通控制有限公司 Tunable output channel delay self-recovery over-current protection circuit
TWI453576B (en) * 2011-09-28 2014-09-21 Inventec Corp Rack-mount server system
EP3418850A1 (en) * 2017-06-21 2018-12-26 Hamilton Sundstrand Corporation Automatically restarting a voltage foldback circuit

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3535864A1 (en) * 1985-10-08 1987-04-16 Ant Nachrichtentech Current limiting circuit
DE3743453A1 (en) * 1986-12-24 1988-07-28 Dold & Soehne Kg E Circuit arrangement for short-circuit protection of a semiconductor amplifier element
US5087871A (en) * 1989-10-17 1992-02-11 U.S. Philips Corporation Power supply with inrush current limiter

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3535864A1 (en) * 1985-10-08 1987-04-16 Ant Nachrichtentech Current limiting circuit
DE3743453A1 (en) * 1986-12-24 1988-07-28 Dold & Soehne Kg E Circuit arrangement for short-circuit protection of a semiconductor amplifier element
US5087871A (en) * 1989-10-17 1992-02-11 U.S. Philips Corporation Power supply with inrush current limiter

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7082020B2 (en) * 2001-01-16 2006-07-25 Siemens Aktiengesellschaft Electronic switching device and an operating method thereof
TWI453576B (en) * 2011-09-28 2014-09-21 Inventec Corp Rack-mount server system
CN103887762A (en) * 2013-03-01 2014-06-25 上海富欣智能交通控制有限公司 Tunable output channel delay self-recovery over-current protection circuit
EP3418850A1 (en) * 2017-06-21 2018-12-26 Hamilton Sundstrand Corporation Automatically restarting a voltage foldback circuit
US10429866B2 (en) 2017-06-21 2019-10-01 Hamilton Sundstrand Corporation Automatically restarting a voltage foldback circuit

Also Published As

Publication number Publication date
AU3712299A (en) 1999-11-16
FI980946A (en) 1999-10-30
FI980946A0 (en) 1998-04-29

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