Igniter circuit for an HID lamp

• US 7,982,405 B2
• Filed: 12/06/2005
• Issued: 07/19/2011
• Est. Priority Date: 03/22/2005
• Status: Expired due to Fees

• Current Assignee: Lightech Electronic Industries Ltd. (Savant Systems, LLC)
• Original Assignee: Lightech Electronic Industries Ltd. (Savant Systems, LLC)
• Inventors: Patchornik, Joshua
• Primary Examiner(s): Owens; Douglas W
• Assistant Examiner(s): A; Minh D
• Application Number:
  US11/909,341
• Publication Number:
  US 20100141164A1
• Time in Patent Office: 2,051 Days
• Field of Search: 315/224, 315/209.R, 315/219, 315/246, 315/209.T, 315/291, 315/307
• US Class Current: 315/224
• CPC Class Codes: H05B 41/2883 the controlled element being a DC/AC converter in the final stage, e.g. by harmonic mode starting
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

An igniter circuit (10) for an HID lamp (11) has a DC input (VBUS) for coupling to a source of DC voltage, and an output (23, 24) for coupling to the HID lamp. A resonant ignition circuit (12) operating at a controlled resonant frequency is coupled to the DC input for producing successive bursts of voltage having a frequency equal to the resonant frequency and having an amplitude that increases with time. The resonant ignition circuit (12) feeds the bursts of voltage across the output of the igniter until an HID lamp coupled thereto reaches breakdown.

Claims

1. An igniter circuit for an HID lamp, the igniter circuit comprising:

a DC input for coupling to a source of DC voltage,

an output for coupling to the HID lamp,

a resonant ignition circuit including;

an oscillator operating at a self-oscillating resonant frequency coupled to said DC input for producing successive bursts of voltage having a frequency equal to the resonant frequency and having an amplitude that increases with time and for feeding said bursts of voltage across the output of the igniter until an HID lamp coupled thereto reaches breakdown, so as to cause the lamp impedance to fall to a low value and load the resonant circuit so that its Q factor falls significantly and stops resonating thereby stopping the oscillator from oscillating;

a current source having a low frequency component and high frequency component;

a transformer comprising a first coil and a second coil connected in series with each other, the second coil being connected in series with the lamp, the first coil being part of the oscillator prior to ignition and, after ignition, serving to block the high frequency component so as to pass the low frequency component to the lamp; and

a first capacitor having a first end coupled to the first coil and having a second end coupled to both the lamp and to a first end of a second capacitor having a second end connected to ground (GND), said first capacitor and second capacitor being configured for passing the high frequency component from the current source to GND.

2. The igniter circuit according to claim 1, wherein the input includes a pair of storage capacitors that are adapted to store high voltage DC, one of said storage capacitors being constituted by the second capacitor.

3. The igniter circuit according to claim 2, wherein the pair of storage capacitors serve to connect directly to respective outputs of a half-wave bridge rectifier.

4. The igniter circuit according to claim 3, wherein said storage capacitors are integral components of an inverter having a half-bridge topology.

5. The igniter circuit according to claims 1, wherein the ignition pulse control circuit is coupled to a sensor responsive to a function of power across the HID lamp for disabling the high voltage oscillator circuit upon ignition of the HID lamp.

6. The igniter circuit according to claim 1, wherein the oscillator comprises:

a drive transformer having a first winding, a second winding and a third winding connected for producing positive feedback,

a first end of the first winding being coupled to the source terminal of a first MOSFET whose gate terminal is coupled via a resistor to a second end of the first winding,

the drain terminal of the first MOSFET being coupled to the DC input,

the first end of the second winding being coupled via a resistor to the gate terminal of a second MOSFET whose source terminal is coupled to a second end of the second winding and constitutes a ground rail,

the drain terminal of the second MOSFET being coupled to the source terminal of the first MOSFET,

the first end of the second winding being coupled to an ON control output of an ON-OFF splitter that is adapted to convey an ignition pulse conveyed by the ignition pulse control circuit to the second winding of the drive transformer to enable oscillation; and

to convey a disable signal to the gate of the second MOSFET to prevent oscillation after the lamp has ignited,

a second end of the second winding being coupled to GND,

an OFF control output of the ON-OFF splitter being connected to the gate of the second MOSFET,

an input of the ON-OFF splitter being connected to an output of the ignition pulse control circuit,

a first end of the third winding of the oscillator drive transformer being connected to a first capacitor connected in series with a first end of a resistor,

a second end of the resistor being coupled to a common junction of a split winding of a transformer comprising a first coil and a second coil wound such that a first end of the first coil is connected to a second end of the second coil,

a first end of the second coil being connected to a first end of the HID lamp, and

a second end of the third winding being connected to the source of the first MOSFET and to the drain of the second MOSFET.

7. The igniter circuit according to claim 6, wherein the oscillator further comprises:

a pair of zener diodes coupled back to back across the first winding, their anodes being commonly connected and their respective cathodes being connected to opposite ends of the first winding, and

a pair of zener diodes coupled back to back across the first winding, their anodes being commonly connected and their respective cathodes being connected to opposite ends of the second winding.

8. A method for igniting a HID lamp, the method comprising:

using a self-oscillating resonant circuit connected across the lamp to generate successive bursts of voltage having a frequency equal to the resonant frequency and having an amplitude that increases with time;

applying said bursts of voltage across the HID lamp until the lamp ignites, thereby loading the resonant circuit so that its Q factor falls sufficiently to stop the resonant circuit self-resonating;

providing a current source having a low frequency component and a high frequency component;

feeding the current source to the lamp through a transformer having a first coil and a second coil connected in series with each other and the second coil being connected in series with the lamp;

prior to ignition, using the first coil as part of the oscillator for generating the resonant frequency; and

after ignition, using the first coil as part of a choke for blocking the high frequency component so as to feed the low frequency component of the current source to the lamp for maintaining the lamp operative while filtering the high frequency component.

9. The method according to claim 8, further including substantially immediately disabling operation of the resonant circuit after lamp ignition.

10. An igniter circuit for an HID lamp, the igniter circuit comprising:

a DC input for coupling to a source of DC voltage,

an output for coupling to the HID lamp,

a resonant ignition circuit operating at a controlled resonant frequency coupled to said DC input for producing successive bursts of voltage having a frequency equal to the resonant frequency and having an amplitude that increases with time and for feeding said bursts of voltage across the output of the igniter until an HID lamp coupled thereto reaches breakdown;

wherein the resonant ignition circuit includes an oscillator controlled by an ignition pulse control circuit coupled thereto and the oscillator comprises;

a drive transformer having a first winding, a second winding and a third winding connected for producing positive feedback,

a first end of the first winding being coupled to the source terminal of a first MOSFET whose gate terminal is coupled via a resistor to a second end of the first winding,

the drain terminal of the first MOSFET being coupled to the DC input,

the first end of the second winding being coupled via a resistor to the gate terminal of a second MOSFET whose source terminal is coupled to a second end of the second winding and constitutes a ground rail,

the drain terminal of the second MOSFET being coupled to the source terminal of the first MOSFET,

the first end of the second winding being coupled to an ON control output of an ON-OFF splitter that is adapted to convey an ignition pulse conveyed by the ignition pulse control circuit to the second winding of the drive transformer to enable oscillation; and

to convey a disable signal to the gate of the second MOSFET to prevent oscillation after the lamp has ignited,

a second end of the second winding being coupled to GND,

an OFF control output of the ON-OFF splitter being connected to the gate of the second MOSFET,

an input of the ON-OFF splitter being connected to an output of the ignition pulse control circuit,

a first end of the third winding of the oscillator drive transformer being connected to a first capacitor connected in series with a first end of a resistor,

a second end of the resistor being coupled to a common junction of a split winding of a transformer comprising a first coil and a second coil wound such that a first end of the first coil is connected to a second end of the second coil,

a first end of the second coil being connected to a first end of the HID lamp, and

a second end of the third winding being connected to the source of the first MOSFET and to the drain of the second MOSFET.

11. The igniter circuit according to claim 10, wherein the oscillator further comprises:

a pair of zener diodes coupled back to back across the first winding, their anodes being commonly connected and their respective cathodes being connected to opposite ends of the first winding, and

a pair of zener diodes coupled back to back across the first winding, their anodes being commonly connected and their respective cathodes being connected to opposite ends of the second winding.

12. The igniter circuit according to claim 10, wherein the ignition pulse control circuit is coupled to a sensor responsive to a function of power across the HID lamp for disabling the high voltage oscillator circuit upon ignition of the HID lamp.

13. The igniter circuit according to claim 10, wherein the input includes a pair of storage capacitors that are adapted to store high voltage DC, one of said storage capacitors being constituted by the second capacitor.

14. The igniter circuit according to claim 13, wherein the pair of storage capacitors serve to connect directly to respective outputs of a half-wave bridge rectifier.

15. The igniter circuit according to claim 13, wherein said storage capacitors are integral components of an inverter having a half-bridge topology.

16. The igniter circuit according to claims 10, wherein the ignition pulse control circuit is coupled to a sensor responsive to a function of power across the HID lamp for disabling the high voltage oscillator circuit upon ignition of the HID lamp.