| A high performance Boost DC-DC converter has been designed for protableelectronic products.The converter is designed based on bipolar process and mainlyused as white LED driver for LCD display backlights and cellular phones.The currentcontrolled PWM modulation mode was used in the converter with a bulit-in1.5MHzfrequency oscillator.The converter has a wide input voltage range, from2.5V to16V,with a steady output voltage as high as24V.Based on the analyse of the basic priciple and the topology of SMPS(switchingmode power supply),the system operation mode has been discussed according to thefunciton and performance. Then the block diagram of the whole chip and the circuitdesign of different module are proposed. To overcome the unstability problem andsub-harmonic oscillation when duty cycle is over50%, a simple dynamic slopecompensation circuit is proposed.To assure the system stability and safety, soft-startcircuit and over voltage protection circuit are included.The system contains bandgap voltage reference, error amplifier, the oscillator, thePWM comparator and dynamic slope compensation circuit. Under Cadence designenviroment, the simulation of the circuit and system is compeleted based on2μm36Vbipolar process. The simulation results indicate the circuit design according to therequirement. |
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