Overvoltage protection for hid lamp ballast

• US 6,919,695 B2
• Filed: 07/05/2002
• Issued: 07/19/2005
• Est. Priority Date: 07/19/2001
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van Casteren, Dolf Henricus Jozef
• Primary Examiner(s): Vo, Tuyet Thi
• Application Number:
  US10/483,863
• Publication Number:
  US 20040183459A1
• Time in Patent Office: 1,110 Days
• Field of Search: 315/291, 315/307, 315/224, 315/209.R, 315/225, 315/246, 315/209.M, 361/91.1, 361/91.2, 361/15, 361/16
• US Class Current: 315/291
• CPC Class Codes: H05B 41/2925 against abnormal lamp operating conditions
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

The present invention relates to a device for operating a high-pressure discharge lamp, comprising a switched mode power supply circuit (SMPS) for supplying power to the high pressure discharge lamp from a supply voltage, the power supply circuit comprising a half bridge commutating forward (HBCF) circuit including an inductance^(Lhbcf?), a capacitor circuit of a first capacitor (C_s1) and a second capacitor (C_s2) in series, the lamp (LA) being connectable between the inductance (L_hbcf) and a point (M) between the first and second capacitor (C_s1,C_s2); wherein overvoltage protection means are connected parallel to the lamp, which switch from an off-state with a high resistance operation to an on-state with a low resistance operation when the voltage difference across the protection means exceeds a breakover voltage (V_bo), the breakover voltage (V_bo) being selected to correspond to a predetermined maximum voltage across the first or the second capacitor (C_s1,C_s2).

Claims

1. Device for operating a high-pressure discharge lamp, comprising a switched mode power supply circuit (SMPS) for supplying power to the high pressure discharge lamp from a supply voltage, the power supply circuit comprising a half bridge commutating forward (HBCF) circuit including an inductance (L_hbcf), a capacitor circuit of a first capacitor (C_s1) and a second capacitor (C_s2) in series, the lamp (LA) being connectable between the inductance (L_hbcf) and a point (M) between the first and second capacitor (C_s1, C_s2);

wherein overvoltage protection means are connected parallel to the lamp, which switch from an off-state with a high resistance operation to an on-state with a low resistance operation when the voltage difference across the protection means exceeds a breakover voltage (V_bo), the breakover voltage (V_bo) being selected to correspond to a predetermined maximum voltage across the first or the second capacitor (C_s1, C_s2).

2. Device according to claim 1, wherein the overvoltage protection means switch from the on-state to the off-state when the current through the protection means {optie van interruptie van de stroom verwijderd} drops below a minimum holding current Ih.

3. Device according to claim 1, wherein the breakover voltage is selected to be in a range between 0,5 and 0,7 times the operating voltage (V_rail) of the switched mode power supply.

4. Device according to claim 1, comprising control means for controlling the switched-mode power supply (SMPS) so as to limit the current through the protection means when the protection means are in the on-state.

5. Device according to claim 1, wherein the overvoltage protection means comprise one or more bidirectional voltage-triggered semiconductor devices.

6. Device according to claim 5, wherein the bidirectional semiconductor device is of a type with substantially symmetrical current-voltage (I-V) characteristics.

7. Device according to claim 5, comprising an additional inductor (L_air) in series with the semiconductor device.

8. Device according to claim 5, wherein the semiconductor device is a SIDAC.

9. Device according to claim 8, wherein the additional inductor is an air inductor.