Starting and operating method and apparatus for discharge lamps

• US 4,525,650 A
• Filed: 01/10/1984
• Issued: 06/25/1985
• Est. Priority Date: 02/11/1982
• Status: Expired due to Term

• Current Assignee: North American Philips Lighting Corporation (Koninklijke Philips N.V.)
• Original Assignee: North American Philips Lighting Corporation (Koninklijke Philips N.V.)
• Inventors: Elms, Robert T., Engel, Joseph C., Saletta, Gary F., Spreadbury, Robert J., Hicks, John M.
• Primary Examiner(s): Dixon, Harold
• Application Number:
  US06/569,547
• Time in Patent Office: 532 Days
• Field of Search: 315/201, 315/205, 315/226, 315/209 R, 315/222, 315/283, 315/137, 315/219, 315/239, 315/242, 315/243, 315/283, 315/DIG. 7, 363/101, 363/37
• US Class Current: 315/226
• CPC Class Codes: H05B 41/2827 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y10S 315/07 Starting and control circuits for gas discharge lamp using transistors

Abstract

Starting and operating method and apparatus for discharge lamps comprises a current-limiting and rectifying means which provides at its output a low-ripple current-limited direct current. To effect lamp starting, a series-connected inductor and capacitor form a high "Q" resonant circuit with the capacitor connected across the lamp to be operated. This starting circuit connects through a blocking capacitor and charging resistor across the low-ripple source of DC. A pair of transistors which comprise an oscillator are connected emitter-to-collector across the source of DC, with the common-connected emitter and collector connected to the blocking capacitor. A drive air-core transformer has separate feedback windings in the starting and operating circuits and drive windings are associated with the transistors. A trigger diode is used to initially pulse one of the transistors which initially oscillate to generate square waves having a frequency corresponding to the resonant frequency of the starting circuit. After the lamp strikes, the transistors operate in a self-oscillating mode with the operating frequency determined by the rate of current flow into the operating feedback winding.

Claims

1. Apparatus for starting and operating miniature metal-vapor discharge lamp means, said apparatus having input terminals adapted to be connected across a source of AC potential of predetermined magnitude, and said apparatus having output terminals across which said discharge lamp means is adapted to be operatively connected, said apparatus comprising:

AC current-limiting and rectifying means having an input connected to said apparatus input terminals and operable to generate at the output thereof a current-limited low-ripple DC potential;

a lamp means starting circuit comprising series-connected inductor means and capacitor means forming a resonant circuit, said starting circuit capacitor means connected across said apparatus output terminals, a blocking capacitor and a charging impedance connected in series with said starting circuit, and the series combination of said starting circuit, blocking capacitor and charging impedance connected across said output of said AC current-limiting and rectifying means;

a pair of transistors comprising oscillator means electrically connected in series arrangement across said output of said AC current-limiting and rectifying means, and the connection between said transistors being electrically connected to said blocking capacitor means;

air-core transformer means comprising a pair of feedback windings and a pair of driving windings, a first of said feedback windings connecting in series with said starting circuit inductor means and capacitor means, and the second of said feedback windings and a current-controlling impedance means connecting in parallel with said starting circuit inductor means and capacitor means, a first of said driving windings connecting in circuit between the base and the emitter of one of said transistors and the second one of said driving windings connecting in circuit between the base and the emitter of the other of said transistors; and

trigger means responsive to initial energization of said apparatus to apply a turn-on pulse to the base of one of said transistors to initiate oscillations between said transistors to generate square waves;

whereby after initial energization of said apparatus and until said lamp means is started said transistors alternately conduct to deliver square waves of current to said lamp means at an oscillation frequency determined by the resonant frequency of said starting circuit series-connected inductor means and capacitor means, and said air-core transformer having a magnetizing inductance such that after said lamp means is started said transistors alternately conduct to deliver square waves of current to said operating lamp at an oscillation frequency determined by the rate of current flow into said second feedback winding.

2. Apparatus for starting and operating metal-vapor discharge lamp means, said apparatus having input terminals adapted to be connected across a source of AC potential of predetermined magnitude, and said apparatus having output terminals across which said discharge lamp means is adapted to be operatively connected, said apparatus comprising:

AC current-limiting and rectifying means having an input connected to said apparatus input terminals and operable to generate at the output thereof a current-limited low-ripple DC potential;

a lamp means starting circuit comprising series-connected inductor means and capacitor means forming a high "Q" resonant circuit, said starting circuit capacitor means connected across said apparatus output terminals, and said starting circuit series-connected inductor means and capacitor means connecting via a charging resistor and blocking capacitor means across said output of said AC current-limiting and rectifying means;

a pair of transistors comprising oscillator means are connected emitter-to-collector in series arrangement across said output of said AC current-limiting and rectifying means, with the common-connected emitter and collector of said transistors connected to said blocking capacitor means;

a drive air-core transformer means comprising a pair of feedback windings and a pair of driving windings, a first of said feedback windings connecting in series with said starting circuit inductor means and capacitor means, and the second of said feedback windings and a current-controlling resistor means connecting in parallel with said starting circuit inductor means and capacitor means, a first of said driving windings connecting between the emitter and base of one of said transistors and the second of said driving windings connecting between the emitter and base of the other of said transistors; and

trigger means responsive to initial energization of said apparatus to apply a turn-on pulse to the base of one of said transistors to initiate oscillations between said transistors to generate square waves;

whereby after initial energization of said apparatus and until said lamp means is started, said transistors alternately conduct to deliver square waves of current to said lamp means at an oscillation frequency determined by the resonant frequency of said starting circuit series-connected inductor means and capacitor means, and after said lamp means is started, said transistors alternately conduct to deliver square waves of current to said operating lamp at an oscillation frequency determined by the rate of current flow into said second feedback winding.

3. The apparatus as specified in claim 2, wherein said discharge lamp means is a miniature-type metal-vapor discharge lamp.

4. The apparatus as specified in claim 3, wherein a standby incandescent light source is energized after power is interrupted and said discharge lamp is not yet started, and also during periods of warm-up for said discharge lamp.

5. The apparatus as specified in claim 2, wherein said discharge lamp means is of the low-pressure positive-column fluorescent type.

6. The apparatus as specified in claim 2, wherein said air-core transformer means also includes a pair of supplemental windings, one of each of said supplemental windings connect in series with diode means between the base and collector of one of each of said pair of transistors to prevent transistor saturation during operation of said apparatus.

7. The apparatus as specified in claim 6, wherein capacitor means connects across the output of said AC current limiting and rectifying means to by-pass from the AC source any high frequency components which are generated by said oscillator means.

8. A circuit for starting and operating a miniature metal-vapor discharge lamp, comprising:

a DC power supply circuit for supplying a current-limited DC electrical signal;

a lamp starting circuit comprised of an inductor and a capacitor connected in series and having respective values effective to define a resonant circuit;

an air-core transformer comprising a pair of feedback windings and a pair of driving windings;

a first of said feedback windings connected in series with said starting circuit for inducing driving winding currents in response to a current flowing through said starting circuit, a current-limiting impedance connected in series with the second of said feedback windings, and the series combination of said current-limiting impedance and said second feedback winding being connected in parallel with the series combination of said starting circuit and said first feedback winding for inducing driving winding currents in response to a current flowing through said current-limiting impedance and said second feedback winding;

a square wave oscillator circuit energized by the current-limited DC electrical signal for generating a square wave output signal, said oscillator circuit comprising a pair of transistors each having a base and a collector-emitter signal path with their respective collector-emitter signal paths connected in series, a first of said driving windings connected between the base and emitter of a first of said transistors and the second of said driving windings connected between the base and emitter of the second of said transistors; and

said square wave oscillator connected for applying a square wave output signal to said resonant starting circuit.

9. In a discharge lamp starting and driving circuit including a controllable square wave oscillator circuit responsive to control signals for generating a square wave lamp driving output signal having a frequency determined by said control signals, and a resonant lamp starting circuit responsive to said oscillator circuit output signal for generating a lamp starting signal, the improvement comprising:

means response to a current in said resonant lamp starting circuit for applying first control signals to said oscillator circuit effective to control said oscillator circuit to generate an output signal applied to said starting circuit and having a frequency determined by the resonant frequency of said starting circuit for generating a high amplitude lamp starting signal; and

means for applying second control signals to said oscillator circuit effective to control said oscillator circuit to generate a square wave lamp driving signal having a frequency different from that of the lamp starting circuit resonant frequency after lamp starting is achieved;

wherein said lamp starting circuit is a series resonant circuit comprised of an inductor and a capacitor in series, and a pair of output terminals for developing the lamp starting signal thereacross;

said means for applying first control signals is comprised of an air-core transformer having a primary winding connected in series with said inductor and said capacitor and adjacent said capacitor for receiving current flowing through said series resonant starting circuit, and a secondary winding for developing in response to the current flowing through said series resonant circuit respective currents constituting the first control signals;

said means for applying second control signals is comprised of a second primary winding of said air core transformer, an impedance element connected in series with said second primary winding, and the series combination of said second primary winding and said impedance element connected in parallel with said lamp starting circuit inductor and the opposite output terminal for developing the second control signals when a discharge lamp is operated by the starting and driving circuit; and

one of said output terminals being connected to an end of said primary winding away from said capacitor and the second of said output terminals being connected to a side of said capacitor away from primary windings, whereby the lamp starting signal developed across said pair of output terminals is substantially equal to a voltage developed across said starting circuit capacitor, and a discharge lamp connected across said output terminals which in a conductive state is effective to shunt said capacitor and primary winding to reduce the current flowing through said primary winding to a sufficiently low value to render the first control signals ineffective to control said oscillator circuit.

10. In a discharge lamp starting and driving circuit including a controllable square wave oscillator circuit responsive to control signals for generating a square wave lamp driving output signal having a frequency determined by said control signals, and a resonant lamp starting circuit responsive to said oscillator circuit output signal for generating a lamp starting signal, the improvement comprising:

means response to a current in said resonant lamp starting circuit for applying first control signals to said oscillator circuit effective to control said oscillator circuit to generate an output signal applied to said starting circuit and having a frequency determined by the resonant frequency of said starting circuit for generating a high amplitude lamp starting signal; and

means for applying second control signals to said oscillator circuit effective to control said oscillator circuit to generate a square wave lamp driving signal having a frequency different from that of the lamp starting circuit resonant frequency after lamp starting is achieved;

wherein said oscillator circuit is comprised of a pair of transistors each having a control electrode and a principal conduction path, said pair of transistors connected with their respective conduction paths in series and said pair of transistors responsive to control signals applied to their respective control electrodes to change the conductivity of their respective conduction paths according to the applied control signals;

said lamp starting circuit is a series resonant circuit comprised of an inductor and a capacitor in series, and a pair of output terminals for developing the lamp starting signal thereacross;

said means for applying first control signals is comprised of an air-core transformer having a primary winding connected in series with said inductor and said capacitor and adjacent said capacitor for receiving current flowing through said series resonant starting circuit, and secondary winding for developing in response to the current flowing through said series resonant circuit respective currents constituting the first control signals;

said means for applying second control signals is comprised of a second primary winding of said air-core transformer, an impedance element connected in series with said second primary winding, and the series combination of said second primary winding and said impedance element connected in parallel with said lamp starting circuit inductor and the opposite output terminal for developing the second control signals when a discharge lamp is operated by the starting and driving circuit; and

one of said output terminals being connected to an end of said primary winding away from said capacitor and the second of said output terminals being connected to a side of said capacitor away from primary windings, whereby the lamp starting signal developed across said pair of output terminals is substantially equal to a voltage developed across said starting circuit capacitor, and a discharge lamp connected across said output terminals which in a conductive state is effective to shunt said capacitor and primary winding to reduce the current flowing through said primary winding to a sufficiently low value to render the first control signals ineffective to control said oscillator circuit.