Maximum duty cycle limiting of pulse width modulators
AssigneeLambda Electronics, Inc.
InventorItzchak Cohen
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Abstract
An apparatus is disclosed for maintaining accurate control of the maximum duty cycle generated by pulse width modulators. The output signal of a pulse width modulation comparator is averaged and compared to a reference value. This reference value is proportional to the peak value of the comparator's output voltage. A closed loop circuit continually adjusts the duty cycle so the difference between the reference value and the average comparator output is nulled thereby providing an accurate maximum duty cycle output.
Claims6
In a power conversion system employing a pulse width modulated (PWM) system control signal, means for accurately and stably setting the maximum duty cycle of said system signal comprising:
- (a) means for generating a reference PWM signal having a pre-set duty cycle for establishing said maximum duty cycle;
- and
- (b) means for comparing said reference PWM signal with said PWM system control;
- signal for producing a resultant PWM system control signal whose duty cycle does not exceed said maximum duty cycle.
In a power conversion system employing a pulse width modulated (PWM) system control signal, a method for accurately and stably setting the maximum duty cycle of said system control signal, comprising the steps of:
- (a) generating a reference PWM signal having a pre-set duty cycle for establishing said maximum duty cycle;
- and
- (b) comparing said reference PWM signal with said system control signal such that the duty cycle of a resultant PWM signal does not exceed said maximum duty cycle.
Dependencies are inferred from the claim text.