| 摘要 |
The present invention provides a circuit for heating a heating element to a desired temperature and generating an output from a single common AC power source. First, the AC power is rectified. An inductor and a capacitor form an L section type filter for the DC from the rectifier. The inductor and the capacitor have a resonate frequency that is greater than the AC power frequency. A switch is connected to the heating element. Next, a controller receives a signal that indicates the actual temperature of the heating element along with an indication of the desired temperature. The controller generates an error signal that PWMs the switch thereby controlling the heating element. Another switch is connected to a transformer. A separate controller PWMs the second switch generating the output at the secondary side of the transformer. The two controllers use a pulse width modulating frequency that is greater than the resonate frequency of the inductor and capacitor. The output of the transformer is rectified by a diode and then filtered by a large capacitor. The intermediate voltage across the capacitor is fed-back to the second controller which in-turn changes the PWM signal to regulate the intermediate voltage. Finally, several power converters convert the intermediate voltage to the desired working voltages.
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