KR200226537Y1 - Electronic ballast for high-voltage discharge lamp without flickers - Google Patents

Abstract

A circuit is provided for eliminating acoustic resonance in high voltage discharge lamps. The electronic ballast according to the present invention includes a power connection part connected to an AC power source and converting into an appropriate AC voltage, a power factor improvement and constant voltage part for rectifying the AC voltage from the power connection part and improving a power factor, and the power factor improvement and constant voltage part from An inverter unit for switching a DC voltage of the inverter to be converted into a pulse to be applied to a discharge lamp, an inverter control unit for turning the inverter unit on and off at a predetermined frequency, and a starting unit for applying a high pressure to turn on the discharge lamp at the beginning of the lamp lighting operation. The ballast further includes an acoustic resonance removing circuit connected to the inverter control unit for converting the predetermined frequency of the inverter control unit at predetermined intervals.

Description

ELECTRONIC BALLAST FOR HIGH-VOLTAGE DISCHARGE LAMP WITHOUT FLICKERS

The present invention relates to an electronic ballast for a high-pressure discharge lamp, and more particularly to an electronic ballast employing a circuit for removing the acoustic resonance phenomenon of the electronic ballast.

For electronic ballasts for high-pressure discharge lamps, Korean Patent Publication No. 97-73235 (published: November 7, 1997), Patent Publication No. 1998-064917 (published: October 7, 1998), and Patent Publication No. 1998-064918 (Publication date: October 7, 1998), Patent Publication No. 1999-002007 (Publication date: January 15, 1999), Patent Publication No. 1999-003730 (Publication date: January 15, 1999) and the like.

By the way, the acoustic resonance phenomenon occurs in the high-pressure discharge lamp operating at a high frequency. Acoustic resonance occurs when the change in pressure in an arc tube coincides with or closes to the natural frequency of the tube. That is, the temperature in the arc tube changes due to the change in the voltage applied to the arc tube according to the change in pressure, and the change in pressure occurs due to the change in temperature, thereby causing the acoustic resonance phenomenon. This acoustic resonance phenomenon causes arc instability, vibration of light output, color temperature and color change, and can increase voltage and, in the worst case, can lead to arc extinction or destruction of arc tube.

The present invention aims to solve the problem of resonant phenomena when high pressure discharge lamp is operated at high frequency, causing unstable light output of arc, shaking color temperature and color change, increasing voltage, extinguishing arc and destroying arc tube. It is done.

1 is a block diagram of a conventional electronic ballast,

2 is a block diagram of an electronic ballast according to the present invention,

3 is a detailed block diagram of an inverter unit, an inverter controller, and an acoustic resonance removing circuit of FIG. 2;

4 is a circuit diagram of an embodiment of the acoustic resonance removing circuit of FIG.

Explanation of symbols on the main parts of the drawings

1: Power supply unit (rectifier circuit and noise filter) 2: Power factor improvement and constant voltage unit

3: inverter section 4: discharge lamp

5: Inverter control unit 6: Starting unit

7: Acoustic resonance elimination circuit 8: Timer circuit

R: Resistor C: Capacitor

Q: MOSFET SW: Switch

In order to solve the acoustic resonance phenomenon, the acoustic resonance phenomenon is prevented from occurring by changing the frequency of vibration of the pressure in the arc tube by changing the input frequency before the acoustic resonance occurs.

Hereinafter, with reference to the accompanying drawings of the present invention will be described in detail.

A block diagram of a conventional electronic ballast is shown in FIG. In Fig. 1, the AC voltage from the power supply connection unit 1 is rectified in the power factor improvement and the constant voltage unit 2 and converted into DC, and this DC voltage is turned on or off by the control of the inverter control unit 5 (inverter unit ( 3) is converted into a pulse to drive the discharge lamp (4). The starting section 6 is for applying a very high voltage at the beginning of the lamp lighting operation.

By the way, in this conventional electronic ballast, the time that the lamp is turned on and the arc becomes unstable, that is, the time taken for the resonance phenomenon to occur is 10 ^-2 seconds to 1 second, which is much smaller than the input frequency.

Therefore, the method of removing the acoustic resonance phenomenon of the present invention uses the principle that the resonance does not occur by changing the frequency of vibration of the pressure in the tube by changing the input frequency before the resonance occurs.

That is, as shown in FIG. 2, the acoustic resonance removing circuit 7 is added to the inverter control unit 5 of the conventional electronic ballast, and the frequency of the inverter control unit is changed before the resonance phenomenon occurs to eliminate the resonance phenomenon.

This will be described in more detail with reference to FIG. 3.

As shown in FIG. 3, the frequency of the interlock control unit is determined by the capacitance values of the capacitors C9, C10, and C11. Capacitors C9 and C10 are inserted to make a fundamental frequency, and C11 is a capacitor connected in parallel with C10 to determine the change in frequency.

At this time, when the timer circuit 8 outputs a square wave of a constant frequency, for example 500 Hz, the switch SW is turned on and off at the same frequency. When the switch SW is turned on, the capacitor C11 is connected to ground, so that the frequency of the inverter controller 5 is determined by the parallel circuit of C10 and C11 and the series circuit of C9. On the contrary, when the switch SW is turned off, the capacitor C11 is opened, so that the frequency of the inverter control section 5 is determined by the series circuit of C10 and C9. Accordingly, the frequency of the inverter controller 5 when the switch SW is turned on and the frequency of the inverter controller 5 when the switch SW is turned off are different.

Thus, the frequency of the inverter control part 5 changes by the same period of the output waveform of the timer circuit 8, and, as a result, the vibration frequency of the pressure in the tube changes. Therefore, if the period in which the frequency of the inverter control section 5 changes is shorter than the time taken for the above-mentioned resonance phenomenon to occur, the resonance phenomenon is eliminated.

However, the frequency at which the resonance phenomenon can be removed (that is, the frequency of the inverter control unit is the inverse of the cycle = the output frequency of the timer circuit) varies depending on the structure of the lamp tube, the value of the circuit elements, and the inverter frequency. Each design requires a separate set, but generally appears to fall within the range of 100 Hz to 10 kHz.

Next, an embodiment of the present invention will be described with reference to FIG. 4.

In FIG. 4, the FET Q4 is employed as the switch SW of FIG. 3, and a timer circuit using the 555 timer U3 is employed as the timer circuit 8.

The timer circuit of this embodiment divides the full-wave rectified voltage Vdc into R4 and R5 as shown in FIG. 4 and rectifies it to C14 to use the power supply voltage and the reset voltage of U3. This voltage is charged with a constant time constant to C13 via R2 as shown in FIG. 4, and the output becomes HIGH during this charging time. When the voltage charged in C13 becomes the threshold voltage of pin 6 of U3, it is discharged to pin 7 through R3. At this time, timer output goes LOW. Thus, the timer output frequency is determined by R2, C13, and R3, and Q4 is turned on and off at this frequency.

In the present embodiment, a 555 timer is employed in the timer circuit 8, and a FET is used as the switch SW. However, this is merely an example, and the present invention is not limited thereto.

By varying the frequency before the resonance occurs, the vibration frequency of the pressure in the tube is changed so that resonance does not occur, thereby preventing arc instability and light output, color temperature and color change, turning off the arc, or breaking the arc tube. can do.

Claims (3)

A power connection part connected to an AC power source and converting into an appropriate AC voltage, a power factor improvement and a constant voltage part for rectifying the AC voltage from the power connection part and improving a power factor, and a pulse by switching the DC voltage from the power factor improvement and the constant voltage part; An electronic ballast comprising: an inverter section for converting a light into a discharge lamp, an inverter control section for turning the inverter section on and off at a predetermined frequency, and a starting section for applying a high pressure to turn on the discharge lamp at the beginning of a lamp lighting operation. And an acoustic resonance removing circuit connected to the inverter control unit for converting the predetermined frequency of the inverter control unit at predetermined intervals. The method of claim 1, wherein the acoustic resonance cancellation circuit A timer circuit for outputting a pulse having a predetermined frequency; A switch turned on and off by the output pulse of the timer circuit; A capacitor connected to change the total capacitance value that determines the predetermined frequency of the inverter control part by turning on and off the switch Electronic ballast characterized in that it comprises a. 3. The ballast of claim 2, wherein the switch is a FET and the timer circuit comprises a 555 timer.