FEATURES
D Combines PFC and Downstream Converter Controls D Controls Boost Preregulator to Near-Unity Power Factor D Accurate Power Limiting D Improved Feedforward Line Regulation D Peak Current-Mode Control in Second Stage D Programmable Oscillator D Leading-Edge/Trailing-Edge Modulation for Reduced Output Ripple D Low Start-up Supply Current D Synchronized Second Stage Start-Up, with Programmable Soft-start D Programmable Second Stage Shutdown DESCRIPTION
The PFC stage is leading-edge modulated while the second stage is trailing-edge synchronized to allow for minimum overlap between the boost and PWM switches. This reduces ripple current in the bulk-output capacitor.In order to operate with over three-to-one range of input-line voltages, a line feedforward (VFF) is used to keep input power constant with varying input voltage. Generation of VFF is accomplished using IAC in conjunction with an external single-pole filter. This not only reduces external parts count, but also avoids the use of high-voltage components, offering a lower-cost solution.
Texas Instruments
