| 摘要 |
A switch mode power supply that may be used for a telephone entry system (TES) or the like with a power factor approaching 1.0. Rectified DC from a full wave rectifier is passed to a pair of inductors that are alternately sinking and sourcing current thereby drawing a more uniform input current because current constantly flows through the full wave rectifier to both of the inductors. A pair of FETs, each connected to one of the pair of inductors, are alternately turned on and off such that current from the current sinking inductor is shunted to ground. When one inductor is sinking current (i.e., through an active one the FETs) the other inductor is sourcing current to charge a filter capacitor and thereby provide an essentially constant unregulated voltage. The unregulated voltage at the capacitor is supplied to voltage regulators which in turn supply regulated voltage. At steady state, all current being supplied by the sourcing inductor is passed directly to and through the voltage regulators.
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