Study On Driving Power Of LCD TV With High-power LED Backlight

With the development of science and technology and the increase of living standards,the traditional CRT TV is emerging of high performance such as LCD TV, plasma TV, TV sets.LED back light television is a new type of environmental protection and energy saving way.LED back light has the characteristics of long service life, low power consumption, nopollution. LED back light TV on its driving power supply also puts forward manyrequirements, such as high power density, high reliability, low EMC, etc.According to the requirement of the LED TV driver power supply, this paper firstdeduces the BOOST topology structure booster principle, parameter design of main circuitand the feedback loop; this study shows that the LLC resonant converter has the switch highworking frequency, small switch loss, a wide input voltage range permission, high efficiency,light weight, small volume, low EMI noise, and the advantages of small switch stress.LLCresonant converter has the primary side switch tube which is easy to realize the full load rangeof ZVS opening, switch of secondary diodes is easy realize ZCS, resonant inductor andtransformer is easy to realize the integration of the magnetic components, as well as the wideinput voltage range, etc. With a half-bridge LLC resonant converter as the DC/DC converter,a half-bridge LLC resonant converter is analyzed in each switch frequency range of theworking principle and specific work waveform; Using the fundamental frequency componentapproximation method to establish the equivalent circuit model of the converter, throughanalyzing the voltage gain of the model, load characteristic, the impedance characteristicanalysis, the author obtains a half-bridge LLC resonant converter parameters optimizationdesign method. At last, A180W drive power supply is designed, Power factor correctionNCP1607is adopted as the control chip, and design the parameters of PFC main circuit andcontrol circuit, select NCP1397as a half-bridge LLC resonant converter control chip, andthen design the main circuit and control circuit of DC-DC transformation parameters. Finally,simulate PFC and LLC resonant and analyze the waveform to show that the design parametersachieves the expected effect.