Electronic device components such as processors and other integrated circuits typically require a power source from which the power to operate the integrated circuit is drawn. The power source ideally provides a constant voltage, and is capable of providing a current that is sufficient to power the various devices it supplies without resulting in a drop in supplied voltage. The task of providing a constant voltage to a load that demands varying degrees of current is typically done by an electronic circuit known as a voltage regulator. Voltage regulators are typically designed to react to changes in load condition to ensure that enough power is provided to the circuit so that the voltage of the supplied power signal remains at or very near the desired level.
Voltage regulators typically are supplied with a voltage greater than the voltage to be supplied by the regulator itself, so that the task of the voltage regulator is to use a power supply providing a large voltage and produce a power supply having a constant lower voltage. One example is a personal computer having a processor running at 3.3 volts. A power supply and voltage regulator operate together to convert the 120 volts of alternating current provided by a wall outlet power connection to a 3.3 volt direct current signal of approximately constant voltage that is used to power the processor.
One method of designing a voltage regulator is to change the supplied high voltage signal into a pulse width modulated signal that feeds an energy storage filter, so that the resulting output signal's voltage is dependent on the width of the high voltage pulses created in the pulse width modulation circuit. The wider the pulses are, the more energy and power is transferred to the energy storage filter circuit, and a higher voltage output signal results. Because the load on voltage regulators varies, and because changing loads will require changing current and therefore changing power be provided by the voltage regulator, the width of pulses can also be varied to change the power provided by the voltage regulator circuit at a certain voltage level. As the load varies to draw more current and therefore draw more power, the width of the pulses must be increased to provide the energy storage filter circuit with more power and therefore maintain the desired voltage at a higher current level. Circuits such as these typically therefore monitor the current drawn and the voltage level, and adjust the width of the pulses produced by the pulse width modulation circuit accordingly.
The frequency of the pulses created by the pulse width modulation circuit is determined by considering a number of factors, including efficiency and size of the voltage regulator circuit. Selecting too low a frequency results in components that are relatively large in physical size and that produce significant ripple or voltage variation in the output signal, while selecting a frequency that is too high results in lower overall efficiency due to the losses from the resulting large number of changes in the electronic state of the various electronic components in the voltage regulator circuit.
A voltage regulator circuit offering minimal ripple and high efficiency that is capable of providing a constant voltage over a wide variety of load conditions is therefore desired.