first, an overview of

< p > Ge Inman Dr. (Inman) and in 1938 invented the practical applications of the fluorescent lamp, and now has nearly 70 years of history. Although the new light source constantly appear, but in a certain period of time, the status of fluorescent lamp as the main lighting source may be difficult to change. In the development process of fluorescent lamps, cheap and practical inductance ballast and starter, to solve the problem of fluorescent lamp starting and limiting, the rapid development and popularization of fluorescent lamps have played a positive role in promoting. However, today, the resources have become more and more nervous, too much consumption of inductance ballast non-ferrous metals make people must think of a way to replace it with more cheap electronic products, electronic ballast in the eighties of the last century arises at the historic moment, up to now has been very popular.

< p > electronic ballasts use fewer components, simple circuit, easy fabrication and large amount of market demand is electronic enthusiasts started the preferred products, qualified students, if you intend to go out after work energetically a words can also be consider manufacturing electronic ballast. As far as I know, there are a few people in Xiantao who specialize in the manufacture of electronic ballast.

the purpose of this lecture is to let the students pay attention to the changes of the lamps and lanterns, to understand the working principle of fluorescent lamp electronic ballast, learn to repair and manufacture of electronic ballast.

two, ordinary fluorescent lamp defects

ordinary fluorescent lamp defects in addition to the consumption of non-ferrous metals too much, the loss of power can not be ignored. The ohmic loss and eddy current loss of the iron core of the winding of the inductance ballast is larger, which is about 15% of the lamp power loss. In the fluorescent lamp so popular today, the total energy consumed by the inductance ballast is very huge. In addition, the inductance ballast power factor is low, generally about 0.5, will cause serious pollution of the power grid, the power sector had to increase the power factor compensation capacitor, increase the cost of electricity.

three, the characteristics of electronic ballast

The working principle of < p > electronic ballast is the power frequency (50Hz or 60Hz) power is converted into 20 ~ 50KHz about high frequency power supply, direct lighting, no need to limit current devices. Compared with the inductance ballast, the electronic ballast has the following advantages:

1, energy saving:

1) lighting efficiency increased by

< p > common fluorescent lamp operating frequency is 50Hz, the lighting efficiency due to the so-called positive (or negative) landing and very low, when the power frequency 1000Hz, the positive (or negative) landing phenomenon disappeared. And electronic ballast operating frequency generally at 20 kHz, does not produce positive or negative potential drop, this is electronic ballast can improve the lighting efficiency.

2) low power loss of electronic ballast.

electronic ballast is difficult to measure its own power consumption, the indirect measurement estimates, the operating point of a better adjustment of electronic ballast, its own consumption is generally below the lamp power of 5%.

2, other advantages

< p > due to the application of the high frequency inductor, electronic ballast has the advantages of small volume, light weight; low voltage starting the lamp is lit; starter; no stroboscopic, no noise and so on.

four, electronic ballast and the main circuit of the main circuit analysis

1, electronic ballast

< p > electronic ballast by the interference filter, rectifier and filter circuit, power factor adjustment device, high frequency converter, resonant circuit, an abnormal state protection circuit and a fluorescent lamp. The block diagram as shown in Figure 1, the function of each part are as follows: < p

1) interference filter: high frequency interference signals to prevent electronic ballast generated into the power grid caused by radiation;

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2) rectifier filter circuit: the 220V power frequency (50Hz or 60Hz) alternating current into 310V DC power, as the power supply of electronic ballast;

3) power factor regulator: to adjust and compensate the power factor of the machine;

4) high frequency conversion circuit: the electronic ballast of the heart circuit, the DC power supply is converted into 20K ~ 50KHz high frequency power supply, to drive the fluorescent lamp. This circuit usually uses a pair of power tube (transistor or field effect tube) composed of a self excited oscillator to achieve;

5) resonant circuit is used to replace common fluorescent lamp starter, it in the fluorescent lamp from Qian Hui, could be the equivalent of a series resonant circuit, the oscillation frequency and the high frequency conversion circuit is equal to the frequency of the, resonance, in the capacitor C produce a very high voltage, ensure lamp fire lit. The equivalent resistance of the lamp is reduced, and the resistance and capacitance C are connected in parallel, which greatly reduces the Q value of the resonant circuit, and the circuit becomes an RL series circuit, and the L becomes a current limiter;

6) abnormal state protection circuit: when the fluorescent lamp is not normal, a high resonant voltage will cause the power device to burn, the circuit's role is to protect the power device in the abnormal state will not be burned;

7) fluorescent lamp: the role is to 20K ~ 50KHz high frequency electric energy into light energy.

2, main circuit analysis

< p > currently commercially available electronic ballast did not according to the block diagram design and manufacturing, some circuit is omitted, figure 2 shows a simple electronic ballast circuit diagram, the principle circuit and most basic consistent. Therefore, we the only analysis the working principle of the circuit;,

(1) after the switch is turned on, the AC 220V voltage is composed of D1 to D4 bridge rectifier circuit, after C1, C2 filter, R1, R2 after the voltage output voltage, +150V and +310V (no load voltage). +310V voltage by C3 to R5 charge, when the voltage on the C3 charge to a certain value (for example, about VT2) when 50V by R4