Control arrangement for a switch mode power supply
First Claim
1. A control arrangement for interfacing a main converter in a switched mode power supply with a full wave rectified mains power supply, the control arrangement receiving an average input voltage Vi having a rectified sinusoidal waveform from the rectified mains supply and providing an average output d.c. voltage Vo as the input to the main converter, and comprising a voltage converter having an inductance, a switching means to connect the inductance across said input voltage, and a control means determining the average input current I to the voltage converter and operable to control a switching duty ratio D of the switching means in dependence thereon, wherein the voltage converter has a voltage transfer function which is a function f(D) of the duty ratio, and said control means is arranged so that f(D) is substantially inversely proportional to I so that the average input current has substantially the same waveform as said average input voltage.
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Accused Products
Abstract
Control arrangement for interfacing a convertor (4) in a switched mode power supply with a mains power supply (1) comprising a switch (14) for controlling input current to the arrangement from the mains power supply to have the same waveform as the input voltage to the arrangement from the mains supply, wherein there is provided a controller (16, 17, 25) operable to control the duty ratio of the switching means in dependence on a predetermined relation between a predetermined time varying signal generated by the controller, and a signal I derived from the input current.
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Citations
10 Claims
- 1. A control arrangement for interfacing a main converter in a switched mode power supply with a full wave rectified mains power supply, the control arrangement receiving an average input voltage Vi having a rectified sinusoidal waveform from the rectified mains supply and providing an average output d.c. voltage Vo as the input to the main converter, and comprising a voltage converter having an inductance, a switching means to connect the inductance across said input voltage, and a control means determining the average input current I to the voltage converter and operable to control a switching duty ratio D of the switching means in dependence thereon, wherein the voltage converter has a voltage transfer function which is a function f(D) of the duty ratio, and said control means is arranged so that f(D) is substantially inversely proportional to I so that the average input current has substantially the same waveform as said average input voltage.
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10. A control arrangement for interfacing a main converter in a switched mode power supply with a full wave rectified mains power supply, the control arrangement receiving an average input voltage Vi having a rectified sinusoidal waveform from the rectified mains supply and providing an average output d.c. voltage Vo as the input to the main converter, and comprising a voltage converter having an inductance, a switching means to connect the inductance across said input voltage, and a control means operable to control the switching means, wherein said control means includes a secondary winding on said inductance to provide a signal indicative of energy in the inductor, and is arranged to close the switch means when said energy falls to zero and to open the switch means after a predetermined interval dependent on error in said output voltage.
Specification