Switching power supply vco

Abstract

An inventive oscillator, inter alia, is disclosed which can be used to generate a frequency modulated control signal or a pulsewidth modulated control signal for application to a switching means in a switching power supply. The output voltage of a power supply is used to control the magnitude of a high bias voltage and a low bias voltage applied to a plus terminal of a voltage comparator, wherein when the output of the voltage comparator is high, the high bias voltage is applied to the plus terminal, and when the output of the voltage comparator is low, the low bias voltage is applied to the plus terminal. A capacitor, coupled to the output of the voltage comparator via a resistor, is coupled between the minus terminal of the voltage comparator and a ground so that when the output of the voltage comparator is high the capacitor charges. When the voltage across the capacitor exceeds that of the high bias voltage, the output of the voltage comparator goes low, discharging the capacitor until the voltage across the capacitor reaches the low bias voltage now applied to the plus terminal of the voltage comparator. The output of the voltage comparator then goes high, and the cycle repeats, thus generating a squarewave output corresponding to the output voltage of the power supply.