EP2285192A1 - Vorwärmzyklussteuerkreis für eine Leuchtstofflampe - Google Patents

Vorwärmzyklussteuerkreis für eine Leuchtstofflampe Download PDF

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Publication number
EP2285192A1
EP2285192A1 EP09165323A EP09165323A EP2285192A1 EP 2285192 A1 EP2285192 A1 EP 2285192A1 EP 09165323 A EP09165323 A EP 09165323A EP 09165323 A EP09165323 A EP 09165323A EP 2285192 A1 EP2285192 A1 EP 2285192A1
Authority
EP
European Patent Office
Prior art keywords
circuit
switching element
controller
preheat
side switching
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Withdrawn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
EP09165323A
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English (en)
French (fr)
Inventor
Winston Langeslag
Arjan Van Den Berg
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.)
NXP BV
Original Assignee
NXP BV
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 NXP BV filed Critical NXP BV
Priority to EP09165323A priority Critical patent/EP2285192A1/de
Publication of EP2285192A1 publication Critical patent/EP2285192A1/de
Withdrawn legal-status Critical Current

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    • 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
    • H05B41/295—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 and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps

Definitions

  • the present invention relates to fluorescent lamps, and more particularly to a preheat cycle control circuit for a fluorescent lamp drive circuit.
  • a fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor.
  • the excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light.
  • Drive circuits are employed to start and operate fluorescent lamps.
  • the choice of drive circuit is based on factors such as mains voltage, tube length, initial cost, long term cost, instant versus non-instant starting, temperature ranges and parts availability, etc.
  • a drive circuit may be used to control the voltage and current provided to the fluorescent lamp during startup and operation.
  • the drive circuit includes a preheat cycle and an operating cycle (comprising an ignition period followed by a burn period).
  • a preheat cycle voltage and current are supplied to the lamp to warm the electrodes. Once the electrodes are warmed, a voltage and current may be supplied to the lamp to excite the gas.
  • the duration of a preheat cycle prior to the operating cycle may be based on a predetermined period of time, based on a resistor with heating characteristics similar to the lamp, or a current or voltage supplied the lamp.
  • an optimal preheat duration maximizes lamp life.
  • the drive circuit uses some form of generic predetermined value of time, current, voltage or resistance to determine the duration of the preheat cycle. Accordingly, the specific type of fluorescent lamp used with the drive circuit must be known and previously tested to determine the predetermined value to be used for the preheat cycle. Furthermore, variations in materials and manufacturing of fluorescent lamps makes the optimal preheat duration of a lamp vary significantly. Thus, an optimal preheat duration for one lamp may be significantly reduce the life or reliability of another similar fluorescent lamp.
  • CFLs Compact Fluorescent Lamps
  • Embodiments utilize a conventional existing sweep capacitor (which typically sets the frequency of operation of a fluorescent lamp drive circuit) to also control the duration of the preheat cycle.
  • embodiments can employ existing packages, such as 8-pin DIP8 packages, whilst adding extra functionality like a pre-heat function.
  • embodiments may regulate the internal preheat current through a low-side half-bridge MOSFET of a fluorescent lamp drive circuit in order to define the preheat cycle.
  • a preheat control circuit for a fluorescent lamp drive circuit having a low-side switching element and high-side switching element connected in series, a controller adapted to switch the switching elements on and off alternately at a frequency of operation, and a sweep capacitance adapted to control the frequency of operation of the controller, the preheat cycle circuit comprising: an integrator circuit adapted to regulate a current through the low-side switching element; and a switch operable to connect the integrator circuit to the controller in a first configuration and to connect the sweep capacitor to the in a second configuration.
  • a preheat cycle control method for use with a fluorescent lamp drive circuit having a low-side switching element and high-side switching element connected in series, a controller adapted to switch the switching elements on and off alternately at a frequency of operation, and a sweep capacitance adapted to control the frequency of operation of the controller, the method comprising the steps of: connecting an integrator circuit to the controller in a first configuration so as to regulate a current through the low-side switching element; and connecting the sweep capacitor to the controller in a second configuration.
  • Proposed embodiments of the invention arrange a sweep capacitor to have two functions. In this way, during a preheat cycle, the sweep capacitor is used for timing the pre-heat cycle and, during the ignition and burn period (i.e. during the operating period) the frequency is set by the sweep capacitor.
  • embodiments are arranged to regulate the peak current through a low side half bridge MOSFET. This current determines the preheat current through the electrodes.
  • a switched capacitor filter with a long integration time in the range of milliseconds can be employed, because the transient response of the half bridge is also long.
  • Figure 1 shows a fluorescent lamp drive circuit according to an embodiment of the invention.
  • the circuit comprises a conventional halfbridge arrangement coupled to an oscillator arrangement 2 and a preheat circuit 3 according to an embodiment of the invention.
  • the halfbridge arrangement is provided with a pair of MOSFET switching elements T1,T2 connected in series, driver circuits 1,2 for controlling the MOSFET switching elements T1,T2 to switch on and off alternately, and fly wheel diodes D1, D2 connected in inverse parallel with the switching elements T1,T2.
  • the oscillator arrangement 2 will now be described with reference to Figure 2 .
  • An input voltage is provided to a voltage controlled oscillator (VCO).
  • the oscillator frequency is determined by this input voltage.
  • the output (OscOut) of the VCO is provided to a non-overlap circuit 7 which generates the signals, HSout and LSout, that are used drive the gate of the high-side (T1) and the low-side (T2) MOSFETs, respectively.
  • the gate drive signals, HSout and LSout are generated with non-overlap time, T NO .
  • This non-overlap time T NO can be fixed or variable (in other words, adaptive) according to requirements.
  • the circuit comprises a switch 10 adapted to connect the SW-pin 12 of the circuit package to the preheat circuit 3 during a pre-heat period, and to connect the SW-pin 12 to the VCO of the oscillator arrangement 2 during an operating period.
  • a sweep capacitor Csw (connected to the SW-pin 12) and the preheat circuit 3 form a switched capacitor integrator adapted to regulate a current through the low-side switching MOSFET T2 and to control the duration of the pre-heat period.
  • the VCO is connected to the output of a switched capacitor filter circuit 3 comprising an amplifier 14.
  • the positive (+) input of the amplifier 14 is connected to a 0.5V voltage source, whereas the negative (-) input of the amplifier 14 is connected to the output of the amplifier 14 via a first filter capacitor C1.
  • the negative (-) input of the amplifier 14 is also connected to a 1.25V voltage source via a first switch 16, and to the resistor Rsh via second 18 and third 20 switches arranged in series. Between the second 18 and third 20 switches there is connected to second filter capacitor C2 to ground.
  • the first 16, second 18 and third 20 switches are controlled by a hard switching HardSW, high-side gate drive signal HSout, and low-side gate drive signal LSout, respectively.
  • the peak current through the low side MOSFET T2 is regulated by regulating the voltage across Rsh to 0.5V (the plus input of the amplifier).
  • the voltage across Rsh is set on capacitor C1.
  • the high-side gate drive signal HSout is high, charge from C1 is pushed in C2. In this way the control regulates the peak voltage across Rsh to 0.5V.
  • the sweep capacitor Csw is connected to the VCO of the oscillator arrangement 2 and controls the frequency of operation of the VCO.
  • the variation of signals in the circuit of Figure 1 is plotted against elapsed time T.
  • the sweep (SW) pin 12 is connected to the preheat timing circuit 3.
  • the sweep capacitor Csw is used for timing, since the voltage of the SW-pin increases linearly (see dashed line of Figure 3a ) to a first reference voltage Vref1 and then decreases linearly.
  • the integrator reference voltage value in this case, the regulation voltage of the integrator (see solid line of Figure 4a )
  • the preheat period is ended.
  • the output of the integrator is connected to the input of the VCO (See solid line of Figure 4b ).
  • the sweep capacitor Csw is connected to the VCO, so the sweep capacitor determines the frequency of the VO.
  • FIG. 5 shows the variation of signals in the circuit of Figure 1 being operated according to an alternative embodiment.
  • the sweep (SW) pin 12 is connected to the input of the VCO.
  • the operating frequency of the VCO is then determined by the sweep capacitor Csw.
  • the integrator voltage Vint determines the input of the VCO.
  • the sweep capacitor Csw is used for timing, since the voltage of the SW-pin increases linearly (see dashed line of Figure 5a ) to a first reference voltage Vref1 and then decreases linearly.
  • the voltage of the SW-pin decreases to below the integrator reference voltage value (in this case, the regulation voltage of the integrator (see solid line of Figure 5a )
  • the preheat period is ended.
  • the sweep capacitor Csw is connected to the VCO, so the sweep capacitor determines the frequency of the VO.
  • the preheat timing circuit 3 (or integrator circuit) can be implemented in a different way, because the capacitor ratio between C1 and C2 is preferably very large. Such an arrangement may require a small second filter capacitor C2, (which very sensitive to noise), and a large first filter capacitor C1.
  • Figure 6 shows a preheat timing circuit 50 according to an alternative embodiment of the invention wherein the capacitor values are of improved practicality.
  • the preheat timing circuit 50 of Figure 6 is an inverting integrator circuit comprising an amplifier 52.
  • the positive (+) input of the amplifier 52 is connected to a 0.5V voltage source, whereas the negative (-) input of the amplifier 52 is connected to a 1.25V voltage source via a first switch 54, and to the sensed Voltage Vsense of a low side resistor (such as Rsh of Figure 1 ) via a second switch 56. Between the first 54 and second 56 switches there is connected a first capacitor C1 to ground.
  • the negative (-) input of the amplifier 52 is also connected to the output of the amplifier 52 via a second capacitor C2.
  • the positive (+) input of the amplifier 52 is also connected to the output of the amplifier 52 via a third switch 58 connected in series with a third capacitor C3, and also connected to the second switch 56 via a fourth switch 60 in series.
  • the negative (-) input of the amplifier 52 is connected to the third switch 58 via a fifth switch 62.
  • the first 54 switch is controlled by a hard switching signal HardSW
  • the second 56 and third 5 switches are controlled by a low-side gate drive signal LSout
  • the fourth 60 and fifth 62 switches are controlled by a high-side gate drive signal HSout.
  • first C1, second C2 and third C3 capacitors have values 2pF, 10pF and 1pF, respectively.
  • embodiments use a packaging pin, which is normally used to control oscillator frequency, to provide it will an additional function during the preheat cycle.
  • the pin is used for timing the pre-heat cycle.
  • embodiments control the peak current through the low-side mosfet of the conventional halfbridge arrangement.
  • an integrated switched capacitor integrator may be employed to define the input of the VCO.
  • the positive (+) input of an amplifier employed for the integrator may be set to a required voltage of the peak voltage of the low-side resistor Rsh.
  • the preheat circuit may be forced to go a maximum frequency by forcing the minus input of the switched capacitor amplifier.
EP09165323A 2009-07-13 2009-07-13 Vorwärmzyklussteuerkreis für eine Leuchtstofflampe Withdrawn EP2285192A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP09165323A EP2285192A1 (de) 2009-07-13 2009-07-13 Vorwärmzyklussteuerkreis für eine Leuchtstofflampe

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP09165323A EP2285192A1 (de) 2009-07-13 2009-07-13 Vorwärmzyklussteuerkreis für eine Leuchtstofflampe

Publications (1)

Publication Number Publication Date
EP2285192A1 true EP2285192A1 (de) 2011-02-16

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EP09165323A Withdrawn EP2285192A1 (de) 2009-07-13 2009-07-13 Vorwärmzyklussteuerkreis für eine Leuchtstofflampe

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Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997042794A1 (en) * 1996-05-03 1997-11-13 Philips Electronics N.V. Ballast
WO1998004103A1 (en) * 1996-07-24 1998-01-29 Motorola Inc. Inverter protection method and protection circuit for fluorescent lamp preheat ballasts
US6002214A (en) * 1997-02-12 1999-12-14 International Rectifier Corporation Phase detection control circuit for an electronic ballast
EP1022932A1 (de) * 1998-07-30 2000-07-26 Mitsubishi Denki Kabushiki Kaisha Gerät zum betreiben einer entladungslampe
WO2004008814A1 (en) * 2002-07-15 2004-01-22 Koninklijke Philips Electronics N.V. Ballast circuit for operating a gas discharge lamp
WO2004071136A1 (en) * 2003-02-04 2004-08-19 Koninklijke Philips Electronics N.V. Circuit arrangement
WO2004079471A2 (en) * 2003-03-03 2004-09-16 International Rectifier Corporation Digital lighting ballast oscillator
WO2004086463A2 (en) * 2003-03-24 2004-10-07 International Rectifier Corporation High voltage offset detection circuit and method
US20050168165A1 (en) * 2003-12-03 2005-08-04 Qinghong Yu Electronic ballast with open circuit voltage control and cable compensation

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997042794A1 (en) * 1996-05-03 1997-11-13 Philips Electronics N.V. Ballast
WO1998004103A1 (en) * 1996-07-24 1998-01-29 Motorola Inc. Inverter protection method and protection circuit for fluorescent lamp preheat ballasts
US6002214A (en) * 1997-02-12 1999-12-14 International Rectifier Corporation Phase detection control circuit for an electronic ballast
EP1022932A1 (de) * 1998-07-30 2000-07-26 Mitsubishi Denki Kabushiki Kaisha Gerät zum betreiben einer entladungslampe
WO2004008814A1 (en) * 2002-07-15 2004-01-22 Koninklijke Philips Electronics N.V. Ballast circuit for operating a gas discharge lamp
WO2004071136A1 (en) * 2003-02-04 2004-08-19 Koninklijke Philips Electronics N.V. Circuit arrangement
WO2004079471A2 (en) * 2003-03-03 2004-09-16 International Rectifier Corporation Digital lighting ballast oscillator
WO2004086463A2 (en) * 2003-03-24 2004-10-07 International Rectifier Corporation High voltage offset detection circuit and method
US20050168165A1 (en) * 2003-12-03 2005-08-04 Qinghong Yu Electronic ballast with open circuit voltage control and cable compensation

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