EP0664059A1 - Protection circuit for electronic systems in general and for an electronic ballast operating discharge lamps in particular - Google Patents

Protection circuit for electronic systems in general and for an electronic ballast operating discharge lamps in particular

Info

Publication number
EP0664059A1
EP0664059A1 EP94927857A EP94927857A EP0664059A1 EP 0664059 A1 EP0664059 A1 EP 0664059A1 EP 94927857 A EP94927857 A EP 94927857A EP 94927857 A EP94927857 A EP 94927857A EP 0664059 A1 EP0664059 A1 EP 0664059A1
Authority
EP
European Patent Office
Prior art keywords
mosfet
voltage
mains voltage
protection circuit
mains
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.)
Withdrawn
Application number
EP94927857A
Other languages
German (de)
French (fr)
Inventor
Paul Adriaan Coster
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.)
Cm Personnel Participation Nv
Original Assignee
Cm Personnel Participation Nv
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 Cm Personnel Participation Nv filed Critical Cm Personnel Participation Nv
Publication of EP0664059A1 publication Critical patent/EP0664059A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/282—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices
    • H05B41/285—Arrangements for protecting lamps or circuits against abnormal operating conditions
    • H05B41/2851—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions
    • H05B41/2856—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions against internal abnormal circuit conditions
    • 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
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage

Definitions

  • Protection circuit for electronic systems in general and for an electronic ballast operating discharge lamps in particular.
  • the invention relates to a protection circuit, which takes care of an overvoltage detection and overvoltage protection, and in particular the limitation of the inrush current of an electronic ballast for discharge lamps.
  • a ballast for operating discharge tubes is common knowled ⁇ ge, in which the current is limited through the discharge lamp, f.i. a fluorescent lamp, by using a choke in serial connection with the lamp. Ingnition of the light usually happens with the aid of a starter, and this starter is in serial connection with the electrodes of the fluorescent lamp.
  • An electronic ballast is a common known circuit with as object to replace the circuit mentioned in de previous alinea. This is achieved by placing two in serial connected switches across the input DC voltage, which one at a time is closed controlled by a predefined control frequency.
  • a high inrush current as a result of charging a large capacity coursing a peak load in the mains supply It applies particularly for an electronic ballast that the number of ballasts connected to a mains distribution group is limited.
  • the object of this invention is to provide a protection circuit for electronic ballast in particular,which eli ates the disadvantages as mentioned above, and where the functions, overvoltage detection, overvoltage protection, and limitation of the inrush current are implemented by one simple circuit.
  • a circuit with the characteristics in the head of conclusie 1 are known of e.g. EP-A1-0272514.
  • the previous mentioned goals of the invention are achieved by a protection circuit with the following characteristics
  • the advantages of the invention are: 1) Through the detection of the mains voltage, the limitation of the inrush current will be activated if the mains voltage is correct. The electronic ballast will not be activated as long as the mains voltage is too high. This is a non-destructive method to protect the electronic ballast against a too high supply voltage.
  • Another advantage is the definable hysteresis of the overvoltage detection at variable voltage. As a result, small changes in the supply voltage at the switching point will not effect the state of the overvoltage detection.
  • the overvoltage detection is formed by resistors R25, R26, R27, capacitor C20, and transistor T3; preceding by a diode- bridge with capacitor C4 and an input filter between mains and the diode-bridge.
  • C20 is charged through R25 as soon as the mains voltage is switched on.
  • the voltage at C20 is limited by the voltage divider R25 in serial with R26 and R27.
  • These last two resistors serve as a voltage divider, which control the base of T3 at a high voltage.
  • the mains voltage's switch off value is set through this voltage divider. T3 will conduct if the voltage of C20 crosses a predefined value.
  • controllable resistor MOSFET Q6 remains in a high impedancy state, or reaches this state by arising mains voltage.
  • the inrush current limitation circuit is formed by resistors R28, R29, R30; capacitors C21, C22, C23; zener diodes Dll and D13; and MOSFET Q6.
  • the inrush current limitation is based on the principle that the MOSFET Q6 is opened slowly, therefore peak currents cannot occur.
  • the inrush current limitation circuit is out of function for as long as T3 conducts. This means that the variable resistor, formed by Q6, is in a high impedancy state.
  • the inrush current limitation circuit will be active for as long as T3 is blocked, but only if the present voltage is correct.
  • R20 will charge 021 till Dll's zener voltage is reached.
  • 022 is charged as soon as 020's voltage oversteps D13's zener voltage.
  • the voltage of 022 forms the gate-source voltage of FET Q6 for as long as Q6 does not conduct.
  • the voltage drop of R30 combined with 022 reduces the gate-source voltage of the MOSFET. This means that the channel resistance of the MOSFET decreases slowly and that the current through the MOSFET is limited. R30 takes care of the feed back of the current through the MOSFET in combination with 022.
  • 023 is used for the suppression of the induction voltage proceeded from the connected switched power supply if the MOSFET Q6 is in a high impedancy state.
  • the overvoltage detection has a certain hysteresis around the switch off voltage. This means that the overvoltage detection will switch off above a definable voltage of supply line V2 and will switch on below a definable voltage of supply line VI, where VI is less than V2.
  • the advantage is that the circuit switches on and off after a clear and a significant change in the mains voltage.
  • the operation of the hysteresis is based on the fact that the average voltage is higher over 04 when the MOSFET bloks compared to when the MOSFET conducts.

Abstract

A protection circuit for an electronic system in general, and an electronic ballast in particular, wherein behind a diode bridge a controllable resistor, formed by a MOSFET, is placed, which will be gradually turned on when the mains voltage is switched on to prevent a high inrush current. The MOSFET will be controlled by a transistor, which determines by the height of the mains voltage, if the MOSFET will conduct. This will protect the electronic system against a high mains voltage.

Description

Protection circuit for electronic systems in general and for an electronic ballast operating discharge lamps in particular.
The invention relates to a protection circuit, which takes care of an overvoltage detection and overvoltage protection, and in particular the limitation of the inrush current of an electronic ballast for discharge lamps. A ballast for operating discharge tubes is common knowled¬ ge, in which the current is limited through the discharge lamp, f.i. a fluorescent lamp, by using a choke in serial connection with the lamp. Ingnition of the light usually happens with the aid of a starter, and this starter is in serial connection with the electrodes of the fluorescent lamp.
An electronic ballast is a common known circuit with as object to replace the circuit mentioned in de previous alinea. This is achieved by placing two in serial connected switches across the input DC voltage, which one at a time is closed controlled by a predefined control frequency.
The disadvantages of known electronic ballast are:
1) A high inrush current as a result of charging a large capacity coursing a peak load in the mains supply. It applies particularly for an electronic ballast that the number of ballasts connected to a mains distribution group is limited.
2) No adequate, non-destructive detection of, and protection against continuous exposure to a high supply voltages. The object of this invention is to provide a protection circuit for electronic ballast in particular,which eli ates the disadvantages as mentioned above, and where the functions, overvoltage detection, overvoltage protection, and limitation of the inrush current are implemented by one simple circuit. A circuit with the characteristics in the head of conclusie 1 are known of e.g. EP-A1-0272514. The previous mentioned goals of the invention are achieved by a protection circuit with the following characteristics
The advantages of the invention are: 1) Through the detection of the mains voltage, the limitation of the inrush current will be activated if the mains voltage is correct. The electronic ballast will not be activated as long as the mains voltage is too high. This is a non-destructive method to protect the electronic ballast against a too high supply voltage.
2) The limitation of the inrush current will only be activated in case of a proper supply voltage and the mains will not suffer from any peak loads. Because of this, it will be possible to connect more electronic ballasts to one distribution group under simular circumstances.
3) Another advantage is the definable hysteresis of the overvoltage detection at variable voltage. As a result, small changes in the supply voltage at the switching point will not effect the state of the overvoltage detection.
The invention will be further explained by means of attached illustration, figure 1.
The overvoltage detection is formed by resistors R25, R26, R27, capacitor C20, and transistor T3; preceding by a diode- bridge with capacitor C4 and an input filter between mains and the diode-bridge. C20 is charged through R25 as soon as the mains voltage is switched on. The voltage at C20 is limited by the voltage divider R25 in serial with R26 and R27. These last two resistors serve as a voltage divider, which control the base of T3 at a high voltage. The mains voltage's switch off value is set through this voltage divider. T3 will conduct if the voltage of C20 crosses a predefined value. As a result controllable resistor MOSFET Q6 remains in a high impedancy state, or reaches this state by arising mains voltage. The inrush current limitation circuit is formed by resistors R28, R29, R30; capacitors C21, C22, C23; zener diodes Dll and D13; and MOSFET Q6. The inrush current limitation is based on the principle that the MOSFET Q6 is opened slowly, therefore peak currents cannot occur.
The inrush current limitation circuit is out of function for as long as T3 conducts. This means that the variable resistor, formed by Q6, is in a high impedancy state.
The inrush current limitation circuit will be active for as long as T3 is blocked, but only if the present voltage is correct. R20 will charge 021 till Dll's zener voltage is reached. 022 is charged as soon as 020's voltage oversteps D13's zener voltage.
The voltage of 022 forms the gate-source voltage of FET Q6 for as long as Q6 does not conduct. At the moment Q6 starts to conduct, the voltage drop of R30 combined with 022, reduces the gate-source voltage of the MOSFET. This means that the channel resistance of the MOSFET decreases slowly and that the current through the MOSFET is limited. R30 takes care of the feed back of the current through the MOSFET in combination with 022.
However, 022 will still be charged through zener diode D13, so that the gate-source voltage still increases, and this has as result that the MOSFET reaches a low impedancy state.
If the overvoltage gets enabled, 021 will be discharged through T3 and the current through R28 can no longer charge 021. 022 is discharged through R29, putting MOSFET Q6 in a high impedancy state. This means that the connected circuit is no longer supplied through the mains.
Further, 023 is used for the suppression of the induction voltage proceeded from the connected switched power supply if the MOSFET Q6 is in a high impedancy state. The overvoltage detection has a certain hysteresis around the switch off voltage. This means that the overvoltage detection will switch off above a definable voltage of supply line V2 and will switch on below a definable voltage of supply line VI, where VI is less than V2. The advantage is that the circuit switches on and off after a clear and a significant change in the mains voltage.
The operation of the hysteresis is based on the fact that the average voltage is higher over 04 when the MOSFET bloks compared to when the MOSFET conducts.

Claims

Conclusions:
1) Protection circuit for an electronic device in general, and an electronic ballast in particular, which is placed directly after the diode bridge, and consist of an controllable resistance vormed by a MOSFET, which will be turned on gradually when the mains voltage is switched on, characterised by the MOSFET's control voltage which is vormed by the difference between the output voltage of a, at the input connected switching device, delay netwerk and the feedback voltage over a resistor placed in series with the MOSFET in de main current.
2) Protection circuit in accordance with conclusion 1, charaterised by the MOSFET which is controlled by a transistor which determines, based on the value from the mains voltage, whether the previous mentioned switching of the MOSFET will taken place or not.
3) Protection circuit in accordance with conclusion 2, charaterised by the transistor's control takes place, based on the value of the mains voltage and in case the mains voltage is too high the MOSFET will not be turned on, so the connected circuit is protected against the high main voltage.
4) Protection circuit in accordance with one of the conclusi- ons 2 through 3, charaterised by the MOSFET which will be blocked in case the mains voltage is above a predefined value. The MOSFET will conduct if the mains voltage is below a certain value, lower than the mains voltage, at which the MOSFET will be blocked. If the mains voltage shows small fluctuations around the switching point, the switching condition stays preserved.
EP94927857A 1993-08-12 1994-08-09 Protection circuit for electronic systems in general and for an electronic ballast operating discharge lamps in particular Withdrawn EP0664059A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NL9301397A NL9301397A (en) 1993-08-12 1993-08-12 Safety switching device for electronic switching devices in general and for an electronic ballast for gas discharge tubes in particular.
NL9301397 1993-08-12
PCT/NL1994/000186 WO1995005696A2 (en) 1993-08-12 1994-08-09 Protection circuit for electronic systems in general and for an electronic ballast operating discharge lamps in particular

Publications (1)

Publication Number Publication Date
EP0664059A1 true EP0664059A1 (en) 1995-07-26

Family

ID=19862752

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94927857A Withdrawn EP0664059A1 (en) 1993-08-12 1994-08-09 Protection circuit for electronic systems in general and for an electronic ballast operating discharge lamps in particular

Country Status (4)

Country Link
EP (1) EP0664059A1 (en)
AU (1) AU7709894A (en)
NL (1) NL9301397A (en)
WO (1) WO1995005696A2 (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE59508863D1 (en) * 1995-08-04 2000-12-21 Siemens Ag Electronic ballast with inrush current limitation and / or surge protection
EP0769855B1 (en) * 1995-10-18 2000-08-16 Koninklijke Philips Electronics N.V. Electrical keying circuit for fluorescent lamps
DE29602914U1 (en) * 1996-02-19 1997-06-19 Tridonic Bauelemente Circuit arrangement for inrush current limitation and overvoltage protection for an active harmonic filter of an electronic ballast
US20100109554A1 (en) * 2007-04-25 2010-05-06 Osram Gesellschaft Mit Beschraenkter Haftung Illumination device having inrush current limiting circuit
EP2375857A1 (en) * 2010-04-08 2011-10-12 Helvar Oy Ab Transformer arrangement for preventing optoelectronics components from damaging
DE112011101249T5 (en) * 2010-04-08 2013-05-02 Helvar Oy Ab Transformer arrangement for protecting opto-electrical components
EP2375856A1 (en) * 2010-04-08 2011-10-12 Helvar Oy Ab Transformer arrangement for protecting optoelectronics components

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3402222A1 (en) * 1984-01-24 1985-07-25 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Circuit arrangement for limiting overvoltages
US4891728A (en) * 1986-12-23 1990-01-02 Siemens Aktiengesellschaft Circuit arrangement for limiting the switch-on current and for providing an over voltage protection in switch mode power supply devices
DE3829705A1 (en) * 1988-09-01 1990-03-15 Ceag Licht & Strom OVERVOLTAGE PROTECTION DEVICE FOR AN ELECTRONIC CIRCUIT
DE3934577A1 (en) * 1989-10-17 1991-04-18 Philips Patentverwaltung POWER SUPPLY DEVICE WITH INRED CURRENT LIMITATION

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9505696A2 *

Also Published As

Publication number Publication date
NL9301397A (en) 1995-03-01
WO1995005696A3 (en) 1995-03-23
AU7709894A (en) 1995-03-14
WO1995005696A2 (en) 1995-02-23

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