How to select the components for electronic ballasts?

Electronic ballast may be the electrical power frequency (50Hz / 60Hz) alternating present into large frequency alternating current, and may make a or a plurality of fluorescent tube usual startup and steady operate of converter (ballast) standard principles:

AC / DC converter, that is composed of the full bridge rectifier, together with other comprehensive, rectifier by electromagnetic interference (EMI) filter (RFI), consisting of an inductor L and also a capacitor C, avert ballast to produce harmonic feedback to input grid, suppression of pollution of energy grid as well as tools interference. At the similar time, prevent the electrical power grid harmonic interference into the ballast. Ahead of the DC filter, the electrical power element correction (PFC) boost circuit can cut down the current harmonic distortion and enhance the energy aspect. Composed of bipolar or MOS – FET, power transistor DC / AC inverter DC voltage converter for 20 ~ 50KHz high-frequency sine wave voltage, output network uses the LC series resonant self-excited circuit or excitation circuit.

High frequency resonance leads to the commencing capacitor to create high voltage pulse to light the lamp,

Soon after the start out in the inductor recent limiting function, auxiliary circuit to improve the safety, reliability, fix the lamp circuit matching, which includes preheating and beginning circuit, an abnormal state safety circuit, high frequency feedback and control circuit

There are numerous types of inverter topologies used in ballast. Based on the input voltage, load power and value considerations can pick flyback flyback), push pull (push pull) and half bridge (half bridge) this kind of as topological structure.

The typical half bridge topology. The resonant circuit involves series resonant, parallel resonance and series parallel resonant circuit,

Series parallel resonant circuit is typically used in the rectifier circuit. Half bridge inverter circuit topology and series parallel resonant circuit could be composed of D common ballast circuit

Class series parallel resonant converter, the pre – stage rectifier module and also the power component correction (PFC) module supply the DC voltage, typically 400V. Following the switch tube S2, S1 close to 50% duty cycle of rotation, for LCR

The resonant circuit supplies an input voltage close to the square wave. Resonant inductor and resonant capacitor, they are the principle parameters we have to get during the style and design. From the preheating stage,

The equivalent resistance from the fluorescent lamp tube is quite significant, and only an incredibly tiny electric resistance with the filament as well as the resonant inductance and resonant capacitor series resonance,

The resonant circuit can form a high ignition voltage at each ends with the tube. Soon after the fluorescent lamp is ignited, the electrical arc equivalent resistance Rlamp on the lamp tube is in the few hundred ohm,

The filament resistance could be neglected. Rlamp resonant inductor and resonant capacitor series parallel resonance, in the end with the tube is applied to 40KHz about the high frequency sinusoidal voltage, in

Lamp voltage lower than the output voltage on the electronic ballast, as a way to normal light fluorescent lamp will have to rely on existing limiting inductance and capacitance starting up amongst series resonance, to improve and meet the working voltage in the lamp tube; and series resonance of establishment, we need to be sure that in specific perform frequency invariant, recent limiting inductance inductance and capacitance commencing capacitance equal; In electronic ballast, the current limiting inductance plus the worth with the starting up capacitor cannot be changed the moment it truly is established.The accuracy and stability of your electronic ballast working frequency are guaranteed,The important thing trouble on the electronic ballast work top quality.

Fluorescent light fixture belongs towards the cathode preheating commence kind electrical light supply, substantial strain cold get started, effortless to provide filament sputtering harm phenomenon filament, seem cathode tube wall early blacking, shorten the lamp life, start out preheating, reduced voltage beginning (300 ~ 400V. The benefits of PTC thermistor: little size, basic circuit, very low expense, its down sides: line electrical power reduction increases (consumable about 0.8W), luminous flux and luminous coefficient decreases, generates the substantial temperature induced by thermal radiation. Electrical power massive PTC need to opt for lower resistance and massive size, lengthy preheating time PTC must decide on substantial Curie stage, substantial dimension abnormal state refers towards the lamp open circuit, quick circuit, overload, do not get started and so on. five lamp phenomenon is open throughout the resonant capacitor has continued in excess of 700V large stress and big resonant recent, simply broken energy tube.

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