UCC38500DW

TEXAS INSTRUMENTS  UCC38500DW..  芯片, PFC/PWM控制器, 20-SOIC

The is a BiCMOS PFC/PWM Combination Controller provides all of the control functions necessary for an active power-factor-corrected pre-regulator and a second-stage DC to DC converter. The controller achieves near-unity power factor by shaping the ac input line current waveform to correspond to the ac input-line voltage using average current-mode control. The DC to DC converter uses peak current-mode control to perform the step-down power conversion. 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 feed-forward 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.

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Combines PFC and downstream converter controls

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Controls boost preregulator to near-unity power factor

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Accurate power limiting

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Improved feedforward line regulation

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Peak current-mode control in second stage

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Programmable oscillator

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Leading-edge/trailing-edge modulation for reduced output ripple

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Low start-up supply current

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Synchronized second stage start-up, with programmable soft-start

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Programmable second stage shutdown

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Green product and no Sb/Br