초록 ▼

A power supply system for providing uninterruptible DC output power with momentary failure of the primary or AC mains supply utilizing a DC power source for back-up includes a power transformer having two primary windings, rectifying means, a serially-connected high voltage switching device coupling

A power supply system for providing uninterruptible DC output power with momentary failure of the primary or AC mains supply utilizing a DC power source for back-up includes a power transformer having two primary windings, rectifying means, a serially-connected high voltage switching device coupling one primary winding to the AC primary mains supply, and a low voltage switching device coupling the second primary winding to the back-up DC supply. An output winding on the power transformer is coupled to a rectifying device for providing a DC output voltage. A transition circuit arrangement senses the DC output voltage and the resulting DC voltage generated by rectifying the AC mains supply and controls the duty cycle of the high voltage and low voltage switching devices by gradually increasing the duty cycle of the low voltage switching device to supply additional power when the AC mains voltage and resulting DC voltage decreases, thereby providing a virtually transient-free DC output voltage. The present circuit arrangement is capable of supplying continuous output power with severe or minor brown-out conditions of the AC mains supply.

대표청구항 ▼

A power supply system for providing uninterruptible DC output power comprising, in combination: (a) a power transformer having first and second primary windings, one end of said first primary winding being coupled to a source of AC power, one end of said second primary winding being coupled to a sou

A power supply system for providing uninterruptible DC output power comprising, in combination: (a) a power transformer having first and second primary windings, one end of said first primary winding being coupled to a source of AC power, one end of said second primary winding being coupled to a source of DC power isolated from said source of AC power, the other ends of said first and second primary windings being coupled to different reference grounds; (b) first and second switching means, said second switching means being coupled between said DC power source and said second primary winding, wherein said first and second switching means including: (i) a first and second power transistor disposed in a DC current path to said first and second primary power windings, respectively, (ii) first and second driver means having input and output terminals, said driver means output terminals being coupled to the base electrodes of said first and second power transistors, respectively, each said driver means being capable of driving said respective power transistors between a normally open non-conducting state between their respective emitter and collector electrodes to a closed conducting state therebetween; (c) input rectifying means connected in series with said first switching means between said AC power source and said first primary transformer winding, said rectifying means rectifying said AC power resulting in a DC voltage being coupled to said first switching means; (d) at least one secondary output winding disposed upon said power transformer; (e) at least one output rectifying means for providing a DC output voltage, said output rectifying means being connected to one of said secondary windings; and (f) transition means coupled to said DC output voltage, said resulting DC voltage and said first and second swtiching means, for sensing the amplitude of said DC output voltage and said resulting DC voltage and controlling the duty cycle of said second switching means by increasing the duty cycle of said second switching means to supply additional power when said resulting DC voltage decreases, thereby providing a virtually transient-free DC output voltage, wherein said transition means including: (i) drive pulse modulator means having an input and an output terminal, for providing a rectangularly-shaped switching voltage at said output terminal with a frequency directly proportional to the amplitude of said DC output voltage within a preselected range, said modulator means input terminal being coupled to said DC output voltage, said modulator means output terminal being coupled to said first driver means input terminal, (ii) variable pulse width generator means, having a pair of input terminals and an output terminal, for providing on said generator means output terminal a variable pulse width switching voltage, one of said generator means input terminals having an internally generated saw-tooth voltage coupled thereon, the other of said generator means input terminals being coupled to said driving pulse modulator means output terminals, (iii) gating means having an output terminal and a pair of input terminals for providing a proportional variable duty cycle switching output voltage on said gating means output terminal, said gating means output terminal being coupled to said second driver means, said first gating means input terminal being coupled to said variable pulse width generator means output terminal, and (iv) ramp generator means, having an input and an output terminal, for generating a ramp output voltage on said ramp generator means output terminal, said ramp generator means output terminal being coupled to said variable pulse generator means other input terminal, said ramp generator providing said ramp output voltage on said ramp generator means output terminal when receiving a voltage change appearing on its input terminal.