Switching converter with open-loop input voltage regulation on primary side and closed-loop load regulation on secondary side
First Claim
1. A switching converter with an open-loop nonisolated input voltage regulator and a closed-loop nonisolated output voltage regulator comprising an isolated power processing stage and said nonisolated input and output voltage regulators, one on each side of an isolation transformer in said power processing stage, with said nonisolated input voltage regulator on the primary side of said transformer regulating against input voltage changes in an open-loop control mode and said nonisolated output voltage regulator on the secondary side of said transformer regulating against load current changes as well as any voltage variations in a closed-loop control mode, said isolated power processing stage comprising a dc voltage source in series with an input inductor, an input energy transfer capacitor and the primary winding of said isolation transformer in that sequence and a main current bidirectional switch connecting a junction between said input inductor and input energy transfer capacitor to the return current path of said primary winding to said dc voltage source,and an auxiliary circuit comprising an auxiliary current bidirectional switch and capacitor in series, said auxiliary circuit being connected in parallel with said main current bidirectional switch, and switching means for driving said main current bidirectional switch and said auxiliary current bidirectional switch out-of-phase such that when either one is turned ON the other is OFF turned off,a secondary circuit comprising an output energy transfer capacitor, a series current bidirectional switch, a load and filter capacitor in parallel, and an output inductor in series in that order with the secondary winding of said isolation transformer, and a rectifier diode connecting a junction between said series current bidirectional switch and said load to a junction between said output inductor and said secondary winding of said isolation transformer, andmeans for synchronizing cyclical operation of said nonisolated output voltage regulator controlling said current bidirectional switch of said secondary circuit with a fixed cyclical rate of said open-loop nonisolated input voltage regulator thereby to provide drive signals to turn ON said main and said auxiliary current bidirectional switches and turn ON said current bidirectional switch of said secondary circuit, and to turn OFF both said main and said auxiliary current bidirectional switches as dictated by said open-loop nonisolated input voltage regulator and to turn OFF said current bidirectional switch of said secondary circuit as dictated by said closed-loop nonisolated output voltage regulator.
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Abstract
An isolated switching dc-to-dc converter is provided with a novel open-loop input voltage regulation on the primary side and the full regulation and independent protection of each of multiple outputs on the secondary side using an auxiliary circuit comprising a current bidirectional switch Qa and a capacitor Ca on the primary side in a series circuit connected in parallel with a main current bidirectional switch Q to assure a continuous conduction mode for operation of the primary boost-like converter, and consequently preserves the simplicity of open-loop input voltage regulation for all loads from no load to full load. The auxiliary switch Qa is very efficient with only a fraction (5% or less) of the losses of the main active switch Q. The ideal dynamic response approaching theoretical limits is achieved for both line and load transients together with a high efficiency (85%) and record power density (20 W per cubic inch) for multiple output converters. Finally, the whole power supply needs isolation only at the main power transformer, since the need for isolation in the open-loop input and closed-loop output regulation control and drive circuitry is completely eliminated.
170 Citations
17 Claims
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1. A switching converter with an open-loop nonisolated input voltage regulator and a closed-loop nonisolated output voltage regulator comprising an isolated power processing stage and said nonisolated input and output voltage regulators, one on each side of an isolation transformer in said power processing stage, with said nonisolated input voltage regulator on the primary side of said transformer regulating against input voltage changes in an open-loop control mode and said nonisolated output voltage regulator on the secondary side of said transformer regulating against load current changes as well as any voltage variations in a closed-loop control mode, said isolated power processing stage comprising a dc voltage source in series with an input inductor, an input energy transfer capacitor and the primary winding of said isolation transformer in that sequence and a main current bidirectional switch connecting a junction between said input inductor and input energy transfer capacitor to the return current path of said primary winding to said dc voltage source,and an auxiliary circuit comprising an auxiliary current bidirectional switch and capacitor in series, said auxiliary circuit being connected in parallel with said main current bidirectional switch, and switching means for driving said main current bidirectional switch and said auxiliary current bidirectional switch out-of-phase such that when either one is turned ON the other is OFF turned off,
a secondary circuit comprising an output energy transfer capacitor, a series current bidirectional switch, a load and filter capacitor in parallel, and an output inductor in series in that order with the secondary winding of said isolation transformer, and a rectifier diode connecting a junction between said series current bidirectional switch and said load to a junction between said output inductor and said secondary winding of said isolation transformer, and means for synchronizing cyclical operation of said nonisolated output voltage regulator controlling said current bidirectional switch of said secondary circuit with a fixed cyclical rate of said open-loop nonisolated input voltage regulator thereby to provide drive signals to turn ON said main and said auxiliary current bidirectional switches and turn ON said current bidirectional switch of said secondary circuit, and to turn OFF both said main and said auxiliary current bidirectional switches as dictated by said open-loop nonisolated input voltage regulator and to turn OFF said current bidirectional switch of said secondary circuit as dictated by said closed-loop nonisolated output voltage regulator.
Specification