Ballast circuit of fluorescent tube

Abstract

The invention provides a ballast circuit of a fluorescent tube, comprising a power driving circuit, a resonance circuit, a slow start power switch and a timing circuit, wherein the resonance circuit is formed by a resonant inductor and a resonant capacitor; the slow start power switch comprises a bridge rectifier, a buffer capacitor and a switch, when the switch is short circuited, an AC power source generated by the power driving circuit can preheat two filaments, when the switch is open circuited, the resonance circuit can oscillate out high voltage to charge the buffer capacitor so that the voltage between the two filaments is slowly risen till generated thermions can sufficiently light the fluorescent tube, and the fluorescent tube can be prevented from internally generating a great amount of mercury ions which impact the two filaments at a starting moment; and the timing circuit sends a switching signal to switch the switch to be open circuited when reaching preheating time, thus at a lighting moment of the fluorescent tube, not only electric powder coated on the two filaments has no loss, but also parts adjacent to the ends of the two filaments inside the fluorescent tube can not be blackened after the fluorescent tube is lighted on and lighted off for more than ten thousand times, thereby the times of the fluorescent tube to be lighted on is increased, and the service life of the fluorescent tube is prolonged.

Description

technical field [0001] The present invention relates to a ballast circuit for a fluorescent lamp, especially a ballast circuit that can make the thermal electrons generated by the filament of the fluorescent lamp sufficient to suppress a large amount of mercury ions generated in the fluorescent lamp at the moment of lighting the fluorescent lamp. The ballast circuit that hits the filament in the fluorescent tube and prevents the electronic powder coated on the filament from being worn out. Background technique [0002] The principle of light emission of general fluorescent lamps, refer to figure 1 As shown, a closed space is formed in a glass lamp tube 10, and the closed space is filled with an inert gas such as argon (argon, referred to as Ar) and a trace amount of mercury (mercury, referred to as Hg). Coat the particle phosphor coating layer (PhosphorLayer), its material includes manganese zinc silicate crystal (Zinc Silicate, Zn2SiO4: Mn), as the luminescent substance of...

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Problems solved by technology

[0015] (a) The method proposed by Wolfram Sowa in US 6,747,418 in 2004, see Figure 7 As shown, a coupling inductor La is used to reduce the voltage during preheating, so that the circuit design is not restricted by formula (1), but the preheating current still needs to pass through the resonant capacitor Cr, so the voltage design of the lamp tube terminal cannot be completely independent On the resonant capacitor Cr

[0016] (b) The paper published by T.-F.Wu et al. in IEEE 2001 in 2001, see Figure 8 , IR Application Example AN-1020, see Figure 9 As shown, the preheating method is changed from current to voltage, so that the lamp voltage during preheating and the filament current in steady state operation are reduced. Therefore, in the circuit, it is necessary to cooperate with the resonant inductor L1a and add two sets of preheating windings L1b , L1c and matching capacitors Cp1, Cp2, although this circuit design gets rid of the constraint of the preheating current and lamp voltage in formula (1), but because the loop current passes through the resonant capacitor Cr1 during preheating, therefore, the lamp tube during preheating The voltage still cannot be completely reduced to zero

[0017] (c) Preheating circuit published by Dietmar Klien in IEEE in 2000, see Figure 10 As shown, the lamp voltage and current during the preheating period can be designed completely separately, but a set of switches S1, S2, preheating inductance elements L2a, L2b, L2c and additional control circuits need to be added to the circuit, so not only the circuit design more complex and more expensive to manufacture

[0018] (d) The circuit published by Chin S.Moo et al. on IEEE 2001 in 2001, see Figure 11 As shown, an AC switch 20 is connected in parallel with the resonant capacitor Cr. Although this method can ensure that the voltage of the lamp tube is almost zero during the preheating period and no arc discharge occurs, the resonant inductance L1a on the loop will The energy of the resonant capacitor Cr will be charged immediately, so that the two ends of the lamp reach the highest withstand voltage of the AC switch 20. If a switching element with a lower withstand voltage is used, the switching element is almost in the Avalanch Breakdown area, and the continuous lighting of all The generated heat will make the switching element more vulnerable to damage, and at low temperature, it may not be possible to light the lamp smoothly. However, if a high withstand voltage switching element is used, arc discharge is likely to occur due to the instantaneous high voltage at both ends of the lamp. Refer to Figure 12 As shown, the loss of filament electronic powder and tube wall phosphor is caused. Therefore, when designing this circuit, it will be difficult to select components in the design, and because the preheating current and the stable lamp current are both related to resonance It is related to inductance, which also makes it difficult to develop and design

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