| 摘要 |
<p>A power supply circuit with a high power factor includes circuitry for receiving an a.c. voltage from an a.c. power source supplying a.c. input current, and circuitry for generating a rectified voltage from the a.c. voltage. The circuit further includes a filter network coupled to the rectifier circuitry for receiving the rectified voltage and, in response, providing a filtered voltage for powering a load. The filter network comprises at least first and second filter capacitors, first circuit circuitry for placing the filter capacitors in series when the capacitors are being charged from the rectified voltage, and second circuit circuitry for placing each capacitor in a respective parallel discharge path when the capacitors are discharging energy into the load. The first circuit circuitry of the filter network includes a resistor with a resistance value selected to reduce harmonic distortion of the a.c. input current to such an extent that the power factor of the circuit exceeds about 90 percent. The load for the mentioned power supply circuit preferably comprises a low pressure discharge lamp contained within a resonant ballast circuit, and a half-bridge switching network for supplying bi-directional power to the resonant ballast circuit. <IMAGE></p> |
