GB2120870A

GB2120870A - Electronic ballast for gas discharge lamps and fluorescent lamps

Info

Publication number: GB2120870A
Application number: GB08213773A
Authority: GB
Inventors: Hsiung Chiou Eric De
Original assignee: HSIUNG CHIOU ERIC DE
Current assignee: HSIUNG CHIOU ERIC DE
Priority date: 1982-05-12
Filing date: 1982-05-12
Publication date: 1983-12-07
Also published as: GB2120870B

Abstract

An electronic ballast for single or multi discharge or fluorescent lamps includes a AC to DC converter D1-D4 etc, high frequency oscillator IC1 - Qz, a switching resonant inverter Q3 and a positive feedback circuit D12, IC2. The ballast can be dimmed by external auto or manual control which varies the oscillator duty cycle. The said ballast removes flicker by AC to DC converter. The said ballast can improve the power efficiency by the use of a switching resonant inverter 3. The said ballast is ideally suited to gas discharge lamp and fluorescent lamp applications, because it can accommodate a wide range of resistance loads at high efficiency. <IMAGE>

Description

SPECIFICATION Electronic ballast for gas discharge lamps and fluorescent lamps This invention concerns electronic ballast for gas discharge lamps and fluorescent lamps.

For many years, gas discharge fluorescent lamps have replaced conventional incandescent lamps in many applications. The gas discharge lamp and fluorescent lamp have a negative resistence characteristic once the lamp is ignited. This means the said lamps need a current limiting ballast. Conventional ballast used core coil inductor or transformer which is relatively heavy, and energy inefficient as compared with electronic ballast. Moreover conventional core coil type ballast operates in the audible frequency range, which is undesirable due to accompanying noise and disturbance annoying to the consumer.

Contrastly, electronic ballast normally operates at relatively high frequency, such as 20 KHZ to 50 KHZ for example, which is above the audible frequency range and relatively free from undesired noise. Also operating at such relatively high frequency may be constructed smaller, and energy efficient as compared with the conventional core coil type ballast.

Moreover light flicker of no more than 2% is easily obtained by the present invention, as compared with 35% - 40% for the conventional core coil type ballast.

This invention provides an electronic ballast for a gas discharge lamp or fluorescent lamp, comprising a source of DC voltage.

a switching resonant inverter connected to receive DC voltage from said source, which comprises an inductor, a transformer, two capacitors, a transistor, a diode and inclusive the lamp load, an oscillator and driver connected to switching resonant inverter which generates the operating frequency, and controls light output of the lamp load through varying the ON/OFF duty cycle of the said transistor, a feed back circuit connected to oscillator and driver which senses the transformer output voltage and then varys the output duty cycle of the said oscillator and driver, and an external Auto/manual dimmer added and connected to oscillator and driver and using manual control means or photo sensor type auto-control means to adjust the light lumen output This invention provides an electronic solid-state ballast, which operates standend or energy efficient fluorescent lamp, which use 25% - 30% less power than the conventional core coil type ballast while providing the same visible light output. Moreover this electronic ballast provides a virtually flicker-free light output, audible noise-free, and can dim the lamp lumen output easily.

The invention will be described further, by way of example, with reference to the accompanying drawings in which: Figure 1 is an electrical block diagram of the inventive electronic ballase; Figure 2 is an electrical block diagram with detail circuitry of switching resonant inverter for single lamp of Figure 1; Figure 3 is an electrical block diagram with detail circuitry of switching resonant inverter for multilamp of Figure 1; and Figure 4 is a detailed schematic diagram of this invention.

The AC to DC converter 1 converts the line input AC voltage to DC voltage. This DC voltage contains very small ripple voltage. This can provide virtually flicker-free light output. This converter also contains a fuse which can prevent catastrophe.

The oscillator and driver 2 provides a high frequency to drive the transistor 9 ON-OFF. Changing its ON-OFF duty cycle can do the dimming control.

The switching resonant inverter 3 includes lamp load 6 to be controlled by the said oscillator and driver 2, its function is inverting the DC voltage which from said AC to DC converter 1, to a constant amplitude high frequency current. The frequency is generated by the said oscillator and driver 2, to flow through the lamp load 6.

The feed back circuit 4 senses the transformer output voltage and then feeds back to the oscillator and driver 2 to vary the ON-OFF duty cycle. The main function of this ckt is to protect the transistor from being damaged if the switching resonant inverter is in wrong condition.

Refer to the Figure 2, an inductor 7, a transformer 8, a transistor 9, a diode 10, two capacitors 11, 12 and a lamp load 13(6), which are constructed as a switching resonant inverter. The advantages of this construction are getting relatively more sinusoidallike output waveform, which will reduce third harmonic distortion and then reduce the radio frequency interference. Moreover the sinusoidal-like output can make the life of lamp bulb longer than the non-sinusoidal-like output of other types of electronic ballast.

Refer to the Figure 3, an inductor 15, two transfor mers 16,21, a transistor 17, a diode 18, two capacitors 19, 20 and a lamp load 22(6). These parts are constructed as a switching resonant inverter. The advantages of this construction, First is getting relatively more sinusoidal-like output waveform which can reduce, third harmonic distortion and then reduce the radio frequency interference.

Moreover the sinusoidal-like output can make the life of a lamp bulb longer than the non-sinusoidallike output of the other electronic ballasts. Second is this construction can drive one or multi-fluorescent lamp if increases the numbers of secondary windings of transformer 18.

In Figure 4, R, can be used as a fuse or opens to prevent burning from over heat when Q3 or rectifier circuit shorts. C1 inhibits instantaneous pulse voltage of AC external power source. D1, D 2, D3 and D4 are bridge rectifier, and C2, L1 are designed for wave filtration. T1 is input transformer, D5, D6, D3 are designed for full wave rectification and provide oscillatory circuit with DC power source. IC1 is square wave oscillatory circuit, R6, C6 may affect the time of square wave HIGH, D8, C5, R3, R4, and VR may adjust the time of square wave LOW. D9 uses the square wave generated by IC1 as the signal of Q2 INPUT through R5 limiting current, C7 may accelerate the time of Q2 OFF.R7, Rs provides Q2 with bias. Rlo limits Q2 Collector current I,to be not too large, T2 primary coil PR1 per se will also be a coupling signal to push Q3when Q2 is loaded. R11 controls Q3 BASE 13 at a suitable value, Rg, Dlo inhibit the instantaneous pulse of T2 PR1 TURN OFF. As a wave form shaping circuit, D13, C1O, T3 PR1 are in combination with Q3 ON/OFF SWITCH to achieve an approximate half-sinusoidal wave at Q3-C and to transmit the sinusoidal wave voltage to lamp tube load through T3, C9 coupling and shaping. IC2 is an integrated circuit consisting of OP AMP and C8 wherein the third terminal is connected to Vcc as a reference voltage, T3 secondary coil output terminal is connected to D12, C11 rectifying wave filter, and through R12, R13 voltage divider, the said voltage is put in the INVERTER of OP AMP so as to change the output terminal voltage which decides the volume of ICr current divider R5, D11 and therefore changes the time of LOW thereof. Q1, R2, C4, D7 are SOFT START circuit, take advantage of C4 instantaneous short action to make instantaneous conductance volume large, affect the time of IC1 LOW so as to achieve the delay of instantaneous output, and protect the life of lamp tube and Q3 instantaneous impact.

Claims

1. An electronic ballast for a gas discharge lamp of fluorescent lamp, comprising a source of DC voltage, a switching resonant inverter connected to receive DC voltage from said source, which comprises an inductor, a transformer, two capacitors, a transistor, a diode and inclusive the lamp load, an oscillator and driver connected to switching resonant inverter which generates the operating frequency, and controls light output of the lamp load through varying the ON/OFF duty cycle of the said transistor, a feed back circuit connected to oscillator and driver which the transformer output voltage and then varys the output duty cycle of the said oscillator and driver, and an external Auto/manual dimmer added and connected to oscillator and driver and using manual control means or photo sensor type auto-control means to adjust the light lumen output.

2. An electronic ballast for one or multi fluorescent lamp as claimed in claim 1, comprising a source of DC voltage, a switching resonant inverter is connected to receive DC voltage from said source which inverter comprises an inductor, two transformers, two capacitors, a transistor, a diode and a lamp load; an oscillator and driver connected to the said switching resonant inverter to generate operating frequency, and control light lumen output of the lamp load through varying the ON/OFF duty cycle of the said transistor; a feed back ckt connected to the said oscillator and driver to sense the transformer output voltage and then vary the output duty cycle of the said oscillator and driver; ; an external Auto/manual dimmer added and connected to the said oscillator and driver, which dimmer uses manual control means or photo-sensor type auto control means to adjust the light lumen output.

3. An electronic ballast for a gas discharge lamp or a fluorescent lamp substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.