Method and Circuit for Enabling Dimming Using Triac Dimmer

• US 20080203934A1
• Filed: 05/08/2006
• Published: 08/28/2008
• Est. Priority Date: 05/09/2005
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van Meurs, Jos
• Application Number:
  US11/913,685
• Publication Number:
  US 20080203934A1
• Time in Patent Office: Days
• US Class Current: 315/224
• CPC Class Codes: H05B 41/2853 against abnormal power supply conditions
• CPC Class Codes: H05B 41/3924 by phase control, e.g. using a triac H05B41/3922 takes precedence

Abstract

To enable dimming of an energy-saving lamp, in particular a gas discharge lamp, using a standard TRIAC dimmer circuit, a large additional current is drawn when the TRIAC is in a non-conductive state, and a small additional current is drawn when the TRIAC is in a conductive state. A current control circuit may be connected between the supply voltage and the ballast circuit of the lamp for drawing said additional currents. The current control circuit comprises two switches and a number of resistors for providing a large or a small resistance. In an embodiment, the amount of current drawn is controlled instead of the resistance using additional circuitry in the current control circuit.

Claims

1. Method for operating an electronic gas discharge lamp, the method enabling dimming of the gas discharge lamp using a TRIAC dimmer circuit (1), the method comprising:

drawing a relatively large current from the dimmer circuit (1) when the TRIAC (5) is in a non-conductive state to bring the TRIAC (5) in the conductive state;

characterized in that the method further comprises;

reducing the current drawn from the dimmer circuit (1) when the TRIAC (5) is in a conductive state.

2. Method according to claim 1, wherein the relatively large current is drawn from the dimmer circuit (1) by connecting a small resistance between the output terminals (7,8) and the current is reduced by connecting a large resistance between output terminals (7,8).

3. Current control circuit (20) for controlling a current drawn from a voltage power source (6), the circuit comprising a first series connection of a first resistive circuit (R1) and a parallel circuit of

a first switch (T2);

and

a second series connection of a second switch (T1) and a second resistive circuit (R2), the first and the second switch (T1, T2) being controlled by the voltage supplied by the voltage power source (6) such that the first switch (T2) is conductive when the supply voltage is below a predetermined level and the second switch (T1) is conductive when the supply voltage is above the predetermined level.

4. Current control circuit according to claim 3, wherein the first and the second switch (T1, T2) are transistors, a control terminal of the transistors (T1, T2) being operatively connected to the supply voltage.

5. Current control circuit according to claim 4, wherein a third transistor (T3) is provided, the third transistor (T3) being connected in series to the first series connection, and a parallel circuit of a capacitor (C1) and a zener diode (D1) being connected to the control terminal of the third transistor (T3) and to a voltage source (V1).

6. Ballast circuit for operating a gas discharge lamp, the ballast circuit comprising a rectifier circuit (10) for receiving a low frequency alternating voltage, an inverter circuit (30) for providing a high frequency lamp current, and a current control circuit (20) according to claim 3, connected between the rectifier circuit (10) and the inverter circuit (30), a buffer capacitor (Cb) being connected between input terminals of the inverter circuit (30) and a diode (D3) being connected between an output terminal of the current control circuit (20) and a terminal of the buffer capacitor (Cb) to prevent current being drawn from the buffer capacitor (Cb).

7. Assembly of a gas discharge lamp (L) and a ballast circuit according to claim 6.

8. Dimmer circuit for dimming an electronic gas discharge lamp (L), the dimmer circuit comprising a TRIAC dimmer circuit (1), a current control circuit (20) according to claim 3 and a rectifier circuit (10) connected between the TRIAC dimmer circuit (1) and the current control circuit (20).