Universal power supply for multiple loads

• US 5,925,278 A
• Filed: 08/23/1996
• Issued: 07/20/1999
• Est. Priority Date: 08/23/1996
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Hirst, B. Mark
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US08/697,387
• Time in Patent Office: 1,061 Days
• Field of Search: 219/661, 219/662, 219/663, 219/665, 219/667, 219/601, 219/671, 307/36, 307/38, 307/39, 307/31, 363/21, 363/89
• US Class Current: 219/662
• CPC Class Codes: H05B 6/04 Sources of current
• CPC Class Codes: H05B 6/06 Control, e.g. of temperature, of power

Abstract

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.

Claims

1. A circuit for generating a first and a second output, said circuit comprising:

a power source operating at a first frequency;

an inductor connected serially to said power source;

a capacitor connected serially to said inductor and said power source;

said inductor and said capacitor having a resonate frequency that is greater than said first frequency;

a first element connected to said inductor and said capacitor;

a first switch connected to said first element and said power source;

a first controller means connected to said first switch for pulse width modulating said first switch at a first PWM frequency that is greater than said resonate frequency thereby generating said first output at said first element;

a second element connected to said inductor and said capacitor;

a second switch connected to said second element and said power source; and

a second controller means connected to said second switch for pulse width modulating said second switch at a second PWM frequency that is greater than said resonate frequency thereby generating said second output at said second element.

2. The circuit of claim 1 wherein said power source further comprising a bridge rectifier.

3. The circuit of claim 1 wherein:

said first element being a heating element; and

said second element being a transformer having a primary side and a secondary side, said primary side being connected to said second switch and said power source.

4. The circuit of claim 3 further comprising:

a diode connected to a secondary side of said transformer; and

a second capacitor connected to said diode and said secondary side of said transformer.

5. The circuit of claim 4 further comprising at least one power converter connected to said second capacitor.

6. A circuit for heating a heating element to a desired temperature and generating an output from a power source, said power source having a periodic varying voltage, said circuit comprising:

said power source operating at a first frequency;

a rectifier connected to said power source;

an inductor connected serially to said rectifier and said heating element;

a capacitor connected serially to said inductor and said rectifier;

said inductor and said capacitor having a resonate frequency that is greater than said first frequency;

a first switch connected to said heating element and said rectifier;

a first controller means connected to said first switch for pulse width modulating said first switch at a first PWM frequency that is greater than said resonate frequency thereby heating said heating element to said desired temperature;

an element connected to said inductor and to said capacitor;

a second switch connected to said element and said rectifier; and

a second controller means connected to said second switch for pulse width modulating said second switch at a second PWM frequency that is greater than said resonate frequency thereby generating said output at said element.

7. The circuit of claim 6 further comprising:

a means for sensing a temperature of said heating element, said first controller means turning said first switch off and on in accordance with said means for sensing.

8. The circuit of claim 6 further comprising:

a means for sensing a voltage of said output, said second controller means turning said second switch off and on in accordance with said means for sensing.

9. The circuit of claim 8 further comprising:

said element being a transformer having a primary side and a secondary side, said primary side being connected to said second switch and said inductor;

a diode connected to said secondary side of said transformer; and

a second capacitor connected to said diode and said secondary side of said transformer.

10. The circuit of claim 9 further comprising at least one power converter connected to said second capacitor.

11. A circuit for heating a heating element to a desired temperature and generating an output from a power source, said power source having a periodic varying voltage, said circuit comprising:

said power source operating at a first frequency;

a means for sensing a temperature of said heating element;

a means for sensing a voltage of said output;

a rectifier connected to said power source;

an inductor connected to said rectifier and said heating element;

a capacitor connected to said inductor and said rectifier;

said inductor and said capacitor having a resonate frequency that is greater than said first frequency;

a first switch connected to said heating element and said rectifier;

a first controller means connected to said first switch and said means for sensing said temperature, said first control means generating an temperature error indicator that is indicative of an error between said desired temperature and said temperature, said first controller means using said temperature error indicator to pulse width modulating said first switch at a first PWM frequency that is greater than said resonate frequency thereby heating said heating element to said desired temperature;

an element connected to said inductor;

a second switch connected to said element and said rectifier; and

a second controller means connected to said second switch and said means for sensing said voltage, said second control means generating an voltage error indicator that is indicative of an error between a desired voltage and said voltage, said second controller means using said voltage error indicator to pulse width modulating said second switch at a second PWM frequency that is greater than said resonate frequency thereby generating said output at said element.

12. The circuit of claim 11 further comprising:

said element being a transformer having a primary side and a secondary side, said primary side being connected to said second switch and said inductor;

a diode connected to said secondary side of said transformer; and

a second capacitor connected to said diode and said secondary side of said transformer.

13. The circuit of claim 12 further comprising at least one power converter connected to said second capacitor.