JP2009176522A - Dimming circuit of discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dimming circuit of a discharge lamp, in which flickering phenomenon occurring during dimming process when the discharge lamp is dimmed by the dimmer can be prevented. <P>SOLUTION: The dimming circuit 10 of the electric discharge lamp includes a resonance unit 11, a rectifier 21, a half bridge output unit 31, and a voltage feedback device 41. The voltage feedback device 41 is connected to the half bridge output unit 31 and the rectifier 21. Here, the resonance frequency of the resonance unit 11 is a prescribed multiple number of an operational frequency of the half bridge output unit 31. According to this circuit, due to a multiple number relationship between the resonance unit 11 and the half bridge output unit 31, an effect is achieved that efficiency is raised and the current is retained. Accordingly, when this circuit is connected to the dimmer, a current interruption occurring in the dimmer is prevented, and the flickering phenomenon of the discharge lamp can be prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dimming circuit for a discharge lamp.

A dimming electronic ballast for a dimmable discharge lamp or fluorescent lamp that is commercially available usually performs dimming control by the frequency variable function of an integrated circuit (IC) chip. However, since an IC chip having a frequency variable function is not inexpensive, the price of a discharge lamp or dimming electronic ballast capable of such dimming control is high and has not yet been accepted by consumers.
For this reason, a method has been presented in which an IC chip having a frequency variable function is not used and only the dimmer is used. However, such a method may cause a flickering phenomenon because current cannot be maintained in the dimming process, and in a serious case, the discharge lamp or the dimmer may be burned out. In addition, flickering causes discomfort to the user's eyes.

The main object of the present invention is to provide a dimming circuit for a discharge lamp that corresponds to a commercially available standard dimmer and can prevent the occurrence of flickering phenomenon by maintaining current in the dimming process of the discharge lamp. It is to be.
Another object of the present invention is to provide a dimming circuit for a discharge lamp that can reduce costs by using only low-priced parts instead of an IC chip having a frequency variable function, and is more easily accepted from the market. It is.

To achieve the above object, a dimming circuit for a discharge lamp according to the present invention includes a resonance unit, a rectifier, a half-bridge output unit, and a voltage feedback device.
The resonance unit includes a first capacitor and a second capacitor connected in series with each other, and a first inductor connected in parallel in a configuration in which the first capacitor and the second capacitor are connected in series. The rectifier is connected to the resonance unit and can convert alternating current into direct current. The half-bridge output unit has two current control switches connected to the rectifier so that they are connected in series with each other. The current control switch has a control end, and the control end is connected to the oscillation unit. The voltage feedback has a second inductor, a third capacitor and a fourth capacitor connected in series with each other, and the voltage feedback is connected to the half bridge output unit and the rectifier.
The resonance frequency of the resonance unit is a predetermined multiple of the operating frequency of the half-bridge output unit.
As a result, the dimming circuit for the discharge lamp according to the present invention can not only perform dimming of the discharge lamp in combination with a standard dimmer, but also can prevent the occurrence of flickering. is there. Furthermore, cost reduction is possible.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(One embodiment)
A dimming circuit for a discharge lamp according to an embodiment of the present invention is shown in FIG. The dimming circuit 10 of the discharge lamp can fulfill a dimming function by combining with a standard dimmer 51 which is a standard dimmer as shown in FIG. 3, for example. The discharge lamp dimming circuit 10 according to the present embodiment includes a resonance unit 11, a rectifier 21, a half-bridge output unit 31, and a voltage feedback device 41.

  The resonance unit 11 includes a first capacitor C1 and a second capacitor C2 connected in series with each other, and a first inductor L1 connected in parallel with a configuration in which the first capacitor C1 and the second capacitor C2 are connected in series. Have. The resonance unit 11 further includes two third inductors L3. One ends of the two third inductors L3 are separately connected to both ends of the second capacitor C2. The other ends of the two third inductors L3 are separately connected to both ends of the fifth capacitor C5. At the same time, both ends of the fifth capacitor C5 become two power input ends N1 and N2.

  The rectifier 21 is connected to the resonance unit 11 and can convert alternating current into direct current. In this embodiment, the rectifier 21 is a bridge type rectifier.

  The half-bridge output unit 31 has two current control switches Q1 and Q2 connected to the rectifier 21 so as to be connected in series with each other. Each of the current control switches Q1 and Q2 has a control terminal G, and each control terminal G is connected to the oscillation unit 35 separately. In the present embodiment, the current control switches Q1 and Q2 are transistors, and the oscillation unit 35 is an RL oscillation circuit configured by connecting a resistor R and an inductor L in series.

The voltage feedback device 41 includes a second inductor L2, a third capacitor C3, and a fourth capacitor C4 that are connected in series with each other. Further, the voltage feedback device 41 is connected to the half-bridge output unit 31 and the rectifier 21.
The resonance frequency of the resonance unit 11 is a predetermined multiple of the operating frequency of the half-bridge output unit 31, more specifically, a predetermined multiple ± 10%. The predetermined multiple is an integer multiple or 1 / N times (N is a natural number), for example, 1 time, 2 times, 3 times or 1/2 times, 1/3 times, 1/4 times, and the like. In the present embodiment, description will be given assuming that the resonance frequency of the resonance unit 11 is, for example, a value of ½ times ± 10%.

  At this time, when the operating frequency of the half-bridge output unit 31 is about 55 KHz, the resonance frequency of the resonance unit 11 is about 27 KHz. The multiple relationship between the operating frequency of such a half-bridge output unit and the frequency of the resonance unit is as shown in FIG. The resonance frequency of the resonance unit 11 can be calculated based on the following formula (1), and can be adjusted by changing the values of the first capacitor C1, the second capacitor C2, and the first inductor L1. .

  A dimming circuit for a discharge lamp according to an embodiment of the present invention can be used by connecting to a standard dimmer 51 and a discharge lamp 99 shown in FIG. Since the standard dimmer 51 is connected to the two power input terminals N1 and N2, the luminance of the discharge lamp 99 can be adjusted by the standard dimmer 51. The discharge lamp 99 is connected to the second inductor L2 and the rectifier 21. Since the circuit configuration of the standard dimmer 51 is a well-known structure as shown in FIG. 3, the description of the unit and the operating principle is omitted.

  If the resonance frequency of the resonance unit 11 is set to ½ times the operating frequency of the half bridge output unit 31 by the above-described configuration and frequency setting, the third capacitor C3 feeds back the current to the two power input terminals N1 and N2. EMI (electromagnetic interference) interference phenomenon can be reliably improved.

  In the process of adjusting the discharge lamp 99 from the bright state to the dark state when dimming, the ringing phenomenon (to be described in detail later) occurs as the power input to the discharge lamp 99 gradually decreases. Occurs). At this time, since the standard dimmer 51 can sufficiently obtain a current sufficient for maintenance by the electric energy stored in the first inductor L1, no current interruption occurs in the bidirectional thyristor 52 in the standard dimmer 51. . Therefore, the flickering problem of the lamp 99 does not occur.

  Further, since the first inductor L1 has a direct current resistance, not only can the amplitude of ringing generated in the dimming process be delayed, and the current interruption phenomenon generated in the standard dimmer 51 can be suppressed, but also in the dimming process. The flicker problem can be prevented.

  The aforementioned ringing phenomenon is an oscillation phenomenon caused by harmonics. That is, in a general circuit, there exists a specific resonance frequency due to a combination of an inductor and a capacitor at the input site, and the current before the dimmer triggers contains a large amount of harmonics. The ringing phenomenon is an oscillation phenomenon caused by the interaction between these harmonics existing in the same current as the resonance frequency.

  When the power is input, the discharge lamp 99 is started to generate a lamp voltage and a current, and a feedback voltage is obtained from the connection point between the second inductor L2 and the discharge lamp 99. Resonance caused by the multiple relationship between the resonance frequency of the resonance unit 11 and the operating frequency of the half-bridge output unit 31 can increase the feedback voltage. Therefore, by increasing the efficiency, the standard dimmer 51 has a current within the entire half cycle. The conduction current can be maintained at.

  The waveforms of the conduction current and the input current are as shown in FIG. As a result, it is possible to maintain a conductive state, so that no flicker phenomenon occurs. Further, due to the discharge characteristics of the discharge lamp 99, when the discharge lamp 99 is adjusted from a bright state to a dark state, as the voltage of the discharge lamp 99 rapidly increases from the normal state, the feedback voltage increases and the efficiency increases. Thus, the effect of increasing the above-described efficiency is achieved, and the flicker phenomenon is not generated.

As described above, the effects of the present invention are as follows.
(1) No flickering phenomenon occurs in the dimming process. The dimming circuit for a discharge lamp according to the present invention achieves the effect of increasing the efficiency and maintaining the current mainly by the multiple relationship of the resonance frequency between the resonance unit and the half-bridge output unit. If the dimming circuit of the discharge lamp according to the present invention is connected to the dimmer, not only the current interruption generated in the TRIAC on the dimmer can be prevented, but also the flicker problem can be prevented.
(2) Cost reduction can be realized. Since the present invention mainly uses only the multiple relationship of the resonance frequency between the resonance unit and the half-bridge output unit, the effect of preventing the flicker phenomenon can be achieved without depending on the frequency variable function of the IC chip. Further, the present invention employs only parts with a low unit price, so the cost is low and it is more easily accepted from the market.

It is a circuit diagram of the light control circuit of the discharge lamp by one Embodiment of this invention. It is a characteristic view which shows the multiple relationship of the operating frequency of the half-bridge output unit and the frequency of a resonance unit in the light control circuit of the discharge lamp by one Embodiment of this invention. It is a circuit diagram of the standard dimmer in the dimming circuit of the discharge lamp by one Embodiment of this invention. It is a characteristic view which shows the waveform of the conduction | electrical_connection current and input current when efficiency is improved in the light control circuit of the discharge lamp by one Embodiment of this invention.

Explanation of symbols

  10: Dimming circuit of discharge lamp, 11: Resonance unit, 21: Rectifier, 31: Half bridge output unit, 41: Voltage feedback, 51: Standard dimmer, 51: TRIAC (bidirectional thyristor), 99: Discharge Lamp, C1: first capacitor, C2: second capacitor, C3: third capacitor, C4: fourth capacitor, C5: fifth capacitor, L1: first inductor, L2: second inductor, L3: third inductor, N1, N2: power input terminals, Q1, Q2: current control switches, G: control terminals

Claims (8)

A resonance unit having a first capacitor and a second capacitor connected in series with each other, and a first inductor connected in parallel to the configuration in which the first capacitor and the second capacitor are connected in series;
A rectifier connected to the resonant unit and capable of converting alternating current into direct current;
Two current control switches connected to the rectifier in series with each other, the current control switch has a control end, the control end is a half-bridge output unit connected to an oscillation unit;
A voltage feedback device connected to the half-bridge output unit and the rectifier and having a second inductor, a third capacitor and a fourth capacitor connected in series with each other;
With
A dimming circuit for a discharge lamp, wherein a resonance frequency of the resonance unit is a predetermined multiple of an operating frequency of the half-bridge output unit.   The dimming circuit for a discharge lamp according to claim 1, wherein the resonance frequency of the resonance unit is ± 10% of a predetermined multiple of the operating frequency of the half-bridge output unit.   3. The discharge lamp dimming circuit according to claim 2, wherein the predetermined multiple is an integer multiple.   The dimming circuit for a discharge lamp according to claim 2, wherein the predetermined multiple is 1 / N times, and N is a natural number.   The resonance unit further includes two third inductors, one end of the two third inductors is separately connected to both ends of the second capacitor, and the other end of the two third inductors is a fifth capacitor. The dimming circuit for a discharge lamp according to claim 1, wherein the dimming circuit is connected to both ends separately.   The dimming circuit for a discharge lamp according to claim 1, wherein the rectifier is a bridge rectifier.   2. The dimming circuit for a discharge lamp according to claim 1, wherein the current control switch is a transistor.   2. The dimming circuit for a discharge lamp according to claim 1, wherein the oscillation unit is an RL oscillation circuit configured by connecting a resistor and an inductor in series. 3.

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