Method and apparatus for regulating the input impedance of PWM converters
AssigneeGreen Power Technologies Ltd.
InventorsShmuel Ben Yaakov, Menachem Hadar
Life of this patent
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Abstract
A controller for a PWM converter. The low frequency input impedance is an important parameter of PWM converters. In active power factor correction schemes, this impedance needs to resistive in order to keep the power factor near unity. The controller of the present invention will force the input terminals of a PWM converter, and in particular that of a Boost converter, to look resistive, or with a reactive component as desired. The advantages of the controller according to the present invention are simplicity, low cost, robustness and the fact that it does not require an analog multiplier and does not require sensing the input voltage.
Claims10
A method for controlling the duty cycle of a duty switch within a boost converter in order to regulate the input impedance of the boost converter, the boost converter having an output voltage and an input current, the method comprising the steps of:
- (a) providing a ramp signal having a slope determined by the output voltage;
- (b) putting the duty switch into a first state when said ramp signal is reset;
- (c) providing a threshold determined by the input current;
- (d) comparing said ramp signal to said threshold;
- and
- (e) putting the duty switch into a second state when said ramp signal reaches said threshold.
A control circuit for controlling the duty cycle of a duty switch within a boost converter in order to regulate the input impedance of the boost converter, the duty switch assuming one of a plurality of states, the boost converter having an output voltage and an input current, the control circuit comprising:
- (a) a dependent ramp signal generator for generating a ramp signal, wherein the slope of said ramp signal is controlled by the output voltage;
- (b) a mechanism for sensing the input current and outputting a threshold signal which is a function of the input current;
- (c) a threshold detector for comparing said ramp signal to said threshold signal;
- and
- (d) a mechanism for controlling the state of the duty switch according to said comparing.
Dependencies are inferred from the claim text.