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THV6530 Datasheet(PDF) 6 Page - THine Electronics, Inc. |
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THV6530 Datasheet(HTML) 6 Page - THine Electronics, Inc. |
6 / 11 page ![]() THine Electronics, Inc. 6/11 Copyright© 2013 THine Electronics, Inc. All rights reserved. THL6530_Rev.1.00_E Function Boost converter The LCD panel VLS supply is generated from a high-efficiency PWM boost converter operating with current mode control, and the switching frequency is 1.2MHz. During the on-period, TON, the synchronous FET connects one end of the inductor to ground, therefore increasing the inductor current. After the FET turns off, the inductor switching node, LX, is charged to a positive voltage by the inductor current. The freewheeling diode turns on and the inductor current flows to the output capacitor. The converter operates in continuous conduction mode when the load current IVLS is at least one-half of the inductor ripple current ΔIrip. VLS F L V V VLS I I I OSC IN IN rip rip IN ) ( 2 The output voltage (VLS) is determined by the duty cycle(D) of the power FET on-time and the input voltage, VIN. D V VLS IN 1 The average load current, IVLS, can be calculated from the power conservation law. VLS IN IN I VLS I V where η is the power conversion efficiency. For a lower load current, the inductor current would decay to zero during the free-wheeling period and the output node would be disconnected from the inductor for the remaining portion of the switching period. The converter would operate in the discontinuous conduction mode . Current mode control is well known for its robustness and fast transient response. An inner current feedback loop sets the on-time and the duty cycle such that the current through the inductor equals to the current computed by the compensator. This loop acts within one switching cycle. A slope compensation ramp is added to suppress sub-harmonic oscillations. An outer voltage feedback loop subtracts the voltage on the FB pin from the internal reference voltage and feeds the difference to the compensator operational transconductance amplifier. This amplifier is compensated by an external R-C network to allow the user to optimize the transient response and loop stability for the specific application conditions. The output voltage VLS can be set by external resistor divider R1 and R2 connected to FB. 2 1 1 R R V VLS FB Fig. 1 FB setup [Compensator selection] This current mode boost converter has a current sense loop and a voltage feedback loop. The current sense loop does not need any compensation. The voltage feedback loop is compensated by an external series R-C network RPC and CPC from PC pin to ground. RCOMP is set to define the high frequency integrator gain for loop bandwidth which relates to the transient response. CPC is set to ensure the loop stability. [Output capacitor selection] The output voltage ripple due to converter switching is R2 R1 FB VLS LX R2 R1 FB VLS LX |
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