IGNITER CIRCUIT FOR AN HID LAMP

• US 20100141164A1
• Filed: 12/06/2005
• Published: 06/10/2010
• Est. Priority Date: 03/22/2005
• Status: Active Grant

• Current Assignee: Lightech Electronic Industries Ltd. (Savant Systems, LLC)
• Original Assignee: Lightech Electronic Industries Ltd. (Savant Systems, LLC)
• Inventors: Patchornik, Joshua
• Granted Patent: US 7,982,405 B2
• Time in Patent Office: Days
• 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 (10) for an HID lamp (11), the igniter circuit comprising:

a DC input (VBUS) for coupling to a source of DC voltage,

an output (23, 24) for coupling to the HID lamp,

a resonant ignition circuit (12) 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.

2. The igniter circuit according to claim 1, wherein the input includes a pair of storage capacitors (C2, C4) that are adapted to store high voltage DC.

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 any one of the preceding claims, wherein the source of DC voltage is derived by a pair of series connected capacitors (C2, C4).

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

6. The igniter circuit according to any one of the preceding claims, wherein the resonant ignition circuit (12) includes an oscillator (13) controlled by an ignition pulse control circuit (14) coupled thereto.

7. The igniter circuit according to claim 6, wherein the ignition pulse control circuit (14) is coupled to a sensor (16) responsive to a function of power across the HID lamp for disabling the high voltage oscillator circuit upon ignition of the HID lamp.

8. The igniter circuit according to claim 6 or 7, wherein the oscillator (13) comprises:

a drive transformer (T1) having a first winding (20), a second winding (21) and a third winding (22) connected for producing positive feedback,

a first end of the first winding (20) being coupled to the source terminal of a first MOSFET (M1) whose gate terminal is coupled via a resistor (R1) to a second end of the first winding (20),

the drain terminal of the first MOSFET (M1) being coupled to the DC input (VBUS),

the first end of the second winding (21) being coupled via a resistor (R2) to the gate terminal of a second MOSFET (M2) whose source terminal is coupled to a second end of the second winding (21) and constitutes a ground rail (GND),

the drain terminal of the second MOSFET (M2) being coupled to the source terminal of the first MOSFET (M1),

the first end of the second winding (21) being coupled to an ‘

ON’

control output of an ON-OFF splitter (25) that is adapted to convey an ignition pulse conveyed by the ignition pulse control circuit (14) to the second winding (21) of the drive transformer (T1) to enable oscillation; and

to convey a disable signal to the gate of the MOSFET (M2) to prevent oscillation after the lamp (11) has ignited,

a second end of the second winding (21) being coupled to GND,

an ‘

OFF’

control output of the ON-OFF splitter (25) being connected to the gate of the MOSFET (M2),

an input of the ON-OFF splitter (25) being connected to an output of the ignition pulse control circuit (14),

a first end of the third winding (22) of the oscillator drive transformer (T1) being connected to a first capacitor (C1) connected in series with a first end of a resistor (R3),

a second end of the resistor (R3) being coupled to a common junction of a split winding of a transformer (T2) comprising a first coil (L1) and a second coil (L2) wound such that a first end of the first coil (L1) is connected to a second end (23) of the second coil (L2),

a first end of the second coil (L2) being connected to a first end of the HID lamp (11), and

a second end of the third winding (22) being connected to the source of M1 and to the drain of M2.

9. The igniter circuit according to claim 8, wherein the oscillator (13) further comprises:

a pair of zener diodes (D1, D2) coupled back to back across the first winding (20), their anodes being commonly connected and their respective cathodes being connected to opposite ends of the first winding (20), and

a pair of zener diodes (D3, D4) coupled back to back across the first winding (20), their anodes being commonly connected and their respective cathodes being connected to opposite ends of the second winding (21).

10. A method for igniting a HID lamp (11), the method comprising:

using a self-oscillating resonant circuit (12) 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; and

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.

11. The method according to claim 10, further including disabling operation of the resonant circuit after lamp ignition.

12. An igniter circuit (10) for an HID lamp (11) substantially as described herein with reference to the drawings.

13. A method for igniting an HID lamp (11) substantially as described herein with reference to the drawings.