Frequency adjusting convertor circuit with variable pulse width and its controlling method

Abstract

A pulse width adjustable frequency controllable current converter able to regulate the pulse width of the signal output by power switch driver according to the value of input current to make the input power of fluorescent tube constant is composed of power switch driver, power switch, transformer unit, feedback detecting unit and voltage controlled oscillator.

Description

technical field [0001] The invention relates to a pulse frequency modulation circuit, in particular to a pulse width adjustable frequency-controlled commutation circuit capable of adjusting the pulse width according to the magnitude of the input DC voltage source voltage and a control method thereof. Background technique [0002] The cold cathode fluorescent lamp is a low-pressure mercury discharge lamp. When the two ends of the cold cathode fluorescent lamp are directly connected to the power supply, the mercury electrons and gas atoms in the tube will collide with each other to generate ultraviolet rays, and then the ultraviolet rays will be converted into visible light when they hit the phosphor on the tube wall. Light. Since the cold cathode lamp does not use a filament, there is no problem of filament burning or breaking, so it has a very reliable service life. [0003] When the cold cathode fluorescent lamp is in stable operation, the required power frequency range is...

AI Technical Summary

Problems solved by technology

[0009] However, although the operating current of the CCFL tube can be effectively adjusted by changing the operating frequency of the resonant tank 205, the figure 1 It can be known from the diagram that the closer the system is to the resonant frequency of the resonant tank 205, the higher the output voltage will be, so the efficiency will be higher, while the farther the operating frequency is from the resonant frequency, the lower the efficiency will be.

Therefore, in many systems where the voltage range of the input DC voltage source is relatively large, if the pulse frequency modulation circuit operates at a relatively high input voltage, it is often necessary to operate away from the resonance frequency to stabilize the output CCFL tube current, which is also As a result, although the input voltage of the circuit is very high, the output efficiency is very low, which is quite uneconomical.

[0010] It can be seen that the above-mentioned existing pulse frequency modulation converter circuit obviously still has inconvenience and defects in structure, control method and use, and needs to be further improved urgently.

In order to solve the problems existing in the pulse frequency modulation converter circuit and its control method, the relevant manufacturers have tried their best to find a solution, but for a long time, no suitable design has been developed, and the general product has no suitable structure. Able to solve the above problems, this is obviously a problem that the relevant industry is eager to solve

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