Pulsed-output power supply with high power factor

摘要

A pulsed-output power supply having a high input power factor. The rate at which energy is transferred from a power supply unit (PSU) to an energy storage element such as a capacitor is monitored and adjusted such that the charging rate substantially matches the time interval between output pulses. In this manner, input power to the PSU is smoothed to a substantially constant level, thereby eliminating input power surges traditionally associated with pulsed-output power supplies and providing a high input power factor (PF). In an embodiment of the invention, energy transfer from the PSU to the capacitor is sensed by a current sensor. The period of current flow to the capacitor is compared to the historical or predicted period between capacitor discharge pulses. The rate of energy transfer from the power supply is automatically adjusted to make these two periods approximately equal. The energy required to charge the capacitor is spread over the time available to minimize the peak current draw from the power source, thus improving the measured power factor.