Discharge lamp lighting circuit

• US 20060261756A1
• Filed: 05/16/2006
• Published: 11/23/2006
• Est. Priority Date: 05/17/2005
• Status: Active Grant

• Current Assignee: Koito Manufacturing Company Limited
• Original Assignee: Koito Manufacturing Company Limited
• Inventors: Ichikawa, Tomoyuki, Matsui, Kotaro, Yagi, Soichi
• Granted Patent: US 7,479,742 B2
• Time in Patent Office: Days
• US Class Current: 315/307
• CPC Class Codes: H05B 41/2887 characterised by a controllable bridge in the final stage
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y10S 315/05 Starting and operating circuit for fluorescent lamp
• CPC Class Codes: Y10S 315/07 Starting and control circuits for gas discharge lamp using transistors

Abstract

A discharge lamp lighting circuit 1 includes a direct current-alternating current converting circuit 3, a starting circuit 4, controlling means 15 for controlling power, switching elements 5H, 5L driven by the controlling means 15 and a series LC resonance circuit (7p, 8, 9). A frequency modulating circuit is provided for restraining acoustic resonance by modulating a frequency of driving the switching element. When a basic frequency related to the drive frequency is equal to or higher than 1 MHz, a modulation width is set to be equal to or higher than 20 kHz.

Claims

1. A discharge lamp lighting circuit comprising:

a direct current-alternating current converting circuit for receiving a direct current input voltage and converting the direct current input voltage to an alternating current voltage,

a starting circuit for supplying a starting signal to a discharge lamp, and

controlling means for controlling a power provided by the direct current-alternating current converting circuit;

wherein the direct current-alternating current converting circuit comprises switching elements driven by the controlling means and a series resonating circuit including a capacitor and at least one of an inductance element or a transformer, the direct current-alternating current converting circuit further including;

a frequency modulating circuit for restraining an acoustic resonance by modulating a frequency of driving the switching elements.

2. The discharge lamp lighting circuit according to claim 1, further including:

a limiter circuit for preventing the frequency of driving the switching elements from exceeding an upper limit frequency capable of maintaining a state of lighting the discharge lamp (Fmax).

3. The discharge lamp lighting circuit according to claim 1 further including:

a limiter circuit for preventing the frequency of driving the switching elements from being less than a frequency lower limit value.

4. The discharge lamp lighting circuit according to claim 1 wherein an output of the frequency modulating circuit has a shape of a triangular wave or substantially a shape of a triangular wave.

5. The discharge lamp lighting circuit according to claim 1 configured so that the frequency of driving the switching elements starts to be modulated after a predetermined time period elapses after starting the discharge lamp by the starting signal.

6. The discharge lamp lighting circuit according to claim 1 wherein the controlling means includes a voltage-frequency converting portion for outputting a signal of a frequency changed in accordance with an input voltage;

and the controlling means is configured so that the output signal of the voltage-frequency converting portion is subjected to a frequency modulation by an output signal of the frequency modulating circuit, and a drive signal generated based on the frequency-modulated output signal of the voltage-frequency converting portion is supplied to the switching elements.

7. The discharge lamp lighting circuit according to claim 1 wherein the controlling means includes a voltage-frequency converting portion for outputting a signal of a frequency changed in accordance with an input voltage;

and the controlling means is configured so that the input voltage modulated by an output signal of the frequency modulating circuit is supplied to the voltage-frequency converting portion, and a drive signal generated based on the output signal of the voltage-frequency converting portion is supplied to the switching elements.

8. The discharge lamp lighting circuit according to claim 2, configured so that a basic frequency (Fc) related to control of driving the switching elements is equal to or higher than 1 MHz, and an allowable width related to the frequency modulation is equal to or higher than 20 kHz and equal to or lower than Δ

max, where Δ

max=2×

(Fmax−

Fc).