CN1874638A - Electronic ballast in use for light tunable gas discharge lamp in high intensity - Google Patents

Abstract

An electronic ballast for dimmable high-intensity gas discharge lamps, mainly composed of a main circuit composed of a low-pass filter rectifier circuit, a power factor correction circuit, a bridge inverter circuit, and a filter resonance circuit, and an isolated drive circuit and a start-up circuit , a frequency adjustment circuit, a start control circuit, and a dimming signal control circuit. switching current. The inverter stage of the present invention has high operating frequency, silent resonance occurs, and the inductor and capacitor of the resonance circuit are small in size, low in cost, small in loss and high in efficiency.

Description

Electronic ballasts for dimmable high intensity discharge lamps

Technical field

The invention belongs to the field of power electronics, and relates to an electronic ballast for high-intensity gas discharge lamps.

Background technique

High-intensity discharge lamps (HID), including high-pressure mercury lamps, high-pressure sodium lamps, metal halide lamps, xenon lamps, krypton lamps, etc., have become a It is the third-generation light source after incandescent lamps and fluorescent lamps, and it is used as the main light source for green lighting projects. It has the advantages of wide working voltage range, small size, light weight, no flicker, no noise, high efficiency, high luminous efficiency, good lighting effect, long life, easy dimming and intelligent control, high power factor, etc. Electronic ballasts will gradually replace magnetic ballasts.

Acoustic resonance phenomenon exists in the high frequency operation of gas discharge lamps, which will cause unstable light output, flickering, and rolling, seriously affecting the lighting effect, and may even cause arc extinguishing or damage to electronic ballasts, so acoustic resonance is an electronic ballast. A problem that must be solved by the controller. At present, the relatively mature solution is low-frequency square wave lighting. The energy provided by the low-frequency square wave operation to the HID lamp has no periodic change, and its operating frequency is lower than the lower limit frequency of acoustic resonance, so no acoustic resonance phenomenon will occur. The commonly used three-level circuit has complex structure, high cost, large volume, low reliability, and is prone to low-frequency noise. However, in the improved two-stage and single-stage circuits, the stress on the switch tube and capacitor increases, the structure is complex, the efficiency is low, and the reliability decreases.

When working at ultra-high frequency, the current change rate of the switching tube is very large, which will generate a lot of electromagnetic interference (EMI). Therefore, making the switching tube work in a soft switching state can reduce the EMI at the operating frequency.

For electronic ballasts with dimming requirements, in order to ensure high efficiency in the entire dimming range, the switching tube must work in a soft switching state within the entire dimming working range. Usually used in series and parallel inverter circuits, it is very difficult to achieve deep dimming with a large frequency range, so that the switching tube can achieve a soft switching state in a wide frequency range. The third-order low-pass T-type filter is used The filtering feature enables narrow frequency dimming. When the T-type filter is used to realize deep dimming, the frequency range is narrow, so the soft switching state of the switching tube in the whole working frequency range is easy to realize.

The traditional T-type filter can make the inverter stage of the electronic ballast realize the characteristics of a third-order low-pass filter and meet the requirements of deep dimming, but the voltage stress on the capacitor and inductor is large, and the current passing through is large, making the The loss on the capacitor and the inductor is large and the cost is high. The operating point is set near the operating frequency of the short circuit, which makes the traditional T-type filter more suitable for high-pressure sodium lamps. When applied to metal halide lamps, the approximate short-circuit working conditions at start-up will damage the switching tube in the inverter circuit at the moment of start-up.

Contents of Invention

The object of the present invention is to provide an electronic ballast for dimmable high-intensity gas discharge lamps which uses a T-shaped filter resonator to limit the current of the inverter circuit and increase the starting voltage.

The purpose of the present invention is achieved by the following scheme: the main loop mainly consists of a low-pass filter rectifier circuit, a power factor correction circuit, a bridge inverter circuit, and a filter resonant circuit; A control loop composed of an optical circuit, a starting control circuit, and a dimming signal control circuit is formed, and a capacitor is set at the inductor output end of the filter resonant circuit to limit the switching tube current through the bridge inverter circuit when the high-intensity gas discharge lamp is started.

In the present invention, since a capacitor is arranged in the filter resonant circuit, it effectively limits the current passing through the switch tube in the inverter circuit when the high-intensity gas discharge lamp is started while increasing the starting voltage, so that the high-intensity gas discharge lamp can be started The current is large enough to enable it to start smoothly, and the current passing through the switching tube in the inverter circuit is very small, which will not damage the switching tube. Setting capacitors in the filter resonant circuit makes the voltage stress at both ends of the capacitor and inductor small, small in size, low in cost, and low in loss, and can well meet the third-order low-pass filter characteristics of the inverter stage and meet the requirements of deep dimming.

Compared with the existing technology, the operating frequency of the inverter stage is above the upper limit frequency of the acoustic resonance, and no acoustic resonance occurs; the operating frequency of the inverter stage is high, and the inductor and capacitor of the filter resonance circuit are small in size and low in cost; the traditional The structure of T-type filter, the loss of inductor and capacitor is small, and the efficiency of electronic ballast is high.

Description of drawings

Fig. 1 is a schematic structural diagram of the present invention;

Fig. 2 is a half-bridge inverter circuit structure diagram of the present invention;

Fig. 3 is the structural diagram of the T-shaped filter resonant circuit of the present invention

Detailed ways

With reference to Fig. 1, the present invention mainly consists of low-pass filter rectifier circuit 2, power factor correction circuit 3, bridge inverter circuit 4, T-type filter resonant circuit 5, isolation drive circuit 7, start-up circuit 8, frequency adjustment circuit 9, start-up The control circuit 10 and the dimming signal control circuit 11 are composed. Among them, the low-pass filter rectifier circuit 2, the power factor correction circuit 3, the bridge inverter circuit 4 and the T-type filter resonance circuit 5 are sequentially connected to form the main circuit of the electronic ballast, the isolation drive circuit 7, the start circuit 8, the frequency adjustment The circuit 9, the starting control circuit 10 and the dimming signal control circuit 11 form the control loop of the electronic ballast, and complete the control functions of starting control and frequency modulation and dimming. 1 is mains electricity.

The start circuit 8 and the start control circuit 10 connected between the power factor correction circuit 3 and the bridge inverter circuit 4 are respectively connected to the metal halide lamp 6, and the start control circuit 10 detects the working state of the metal halide lamp 6 , to control the start-up circuit 8 to generate a high-voltage pulse to complete the start-up of the metal halide lamp 6 . The isolation drive circuit 7 , frequency adjustment circuit 9 and dimming signal control circuit 11 connected in sequence are connected by the isolation drive circuit 7 to the bridge inverter circuit 4 , and the power factor correction circuit 3 is connected to the frequency adjustment circuit 9 . The frequency adjustment circuit 9 is controlled by the dimming signal control circuit 11 and the working state of the metal halide lamp 6 to generate different frequencies, and the functions of dimming and constant power are realized through frequency changes. The isolated drive circuit 7 generates an ultra-high frequency drive signal to make the bridge inverter circuit work normally.

The bridge inverter circuit 4 is a half-bridge inverter circuit, which is composed of switching tubes Q1, Q2 and a DC blocking capacitor Cd, the switching tubes Q1, Q2 are connected in series, and its connection point is connected with the DC blocking capacitor Cd, as shown in Figure 2 .

The T-shaped filter resonant circuit 5 is composed of inductors L1, L2, capacitors C1, and C2. One end of the capacitor C1 is connected to the series midpoint of the inductors L1 and L2, and the other end is connected to the input end. One end of the capacitor C2 is connected to the inductor L2. As the output, as shown in Figure 3.

Claims (1)

1. An electronic ballast for dimmable high-intensity gas discharge lamps, mainly composed of a low-pass filter rectifier circuit (2), a power factor correction circuit (3), a bridge inverter circuit (4), a filter resonance circuit (5) ), and a control loop consisting of an isolated drive circuit (7), a start-up circuit (8), a frequency dimming circuit (9), a start-up control circuit (10), and a dimming signal control circuit (11), It is characterized in that: the output terminal of the inductor (L2) of the filter resonant circuit (5) is set to limit the current passing through the switch tubes (Q1, Q2) of the bridge inverter circuit (4) when the high-intensity gas discharge lamp (6) is started capacitor (C2).

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