Method and apparatus for power conversion and regulation of two output voltages

• US 7,759,914 B2
• Filed: 12/18/2006
• Issued: 07/20/2010
• Est. Priority Date: 12/18/2006
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Uccelli, Matteo, Odell, Arthur B., Pastore, Tiziano
• Primary Examiner(s): Sterrett; Jeffrey L
• Assistant Examiner(s): Finch, III; Fred E
• Application Number:
  US11/641,425
• Publication Number:
  US 20080143309A1
• Time in Patent Office: 1,310 Days
• Field of Search: 323266-268, 323224-226, 323/315, 363/63
• US Class Current: 323/267
• CPC Class Codes: H02M 1/0045 Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A power supply converter is disclosed. An apparatus according to aspects of the present invention includes a power supply converter having an energy transfer element coupled between a power converter input and first and second power converter outputs. A switch is coupled between the power converter input and the energy transfer element. A control circuit is coupled to the switch to control switching of the switch to generate a first output voltage at the first power converter output and a second output voltage at the second power converter output. A sum of the first and the second output voltages is regulated in response to a first voltage reference. The second output voltage is regulated in response to a second voltage reference. A current in the energy transfer element is coupled to be increased when a voltage across the energy transfer element is a difference between an input voltage at the power converter input and the first output voltage. The current in the energy transfer element is coupled to be decreased when the voltage across the energy transfer element is the sum of the first and second output voltages.

Claims

1. A power converter, comprising:

an energy transfer element coupled between a power converter input and first and second power converter outputs;

a switch having a first terminal coupled to the energy transfer element to provide a conduction path for the energy transfer element to receive an input current supplied from the power converter input;

a control circuit coupled to the switch to control switching of the switch to generate a first output voltage at the first power converter output and a second output voltage at the second power converter output, wherein a sum of the first and the second output voltages is regulated in response to a first voltage reference, wherein the second output voltage is regulated in response to a second voltage reference, wherein a current in the energy transfer element is coupled to be increased when a voltage across the energy transfer element is a difference between an input voltage at the power converter input and the first output voltage, and wherein the current in the energy transfer element is coupled to be decreased when the voltage across the energy transfer element is the sum of the first and second output voltages;

a capacitor having a second terminal and a third terminal, wherein the second terminal is coupled to the first terminal of the switch and the third terminal is coupled between the first power converter output and a feedback terminal of the control circuit, wherein the capacitor is coupled to charge to a voltage approximately equal to the sum of the first and second output voltages, wherein the control circuit is further coupled to regulate the sum of the first and second output voltages in response to a signal proportional to the voltage on the capacitor; and

a shunt circuit coupled across the first power converter output to regulate the second output voltage in response to the second voltage reference.

2. The power converter of claim 1 further comprising a Zener diode coupled to the shunt circuit to provide the second voltage reference.

3. The power converter of claim 2 wherein the shunt circuit comprises a unidirectional transconductance amplifier coupled to the first power converter output to add unidirectional current at the first power converter output if a first load impedance is insufficient to regulate the first output voltage.

4. The power converter of claim 3 wherein the unidirectional transconductance amplifier is coupled to the second voltage reference.

5. The power converter of claim 2 wherein the shunt circuit includes a first bipolar transistor coupled in series with a first resistor coupled across the first power converter output.

6. The power converter of claim 5 wherein the shunt circuit further includes a thermal matching bipolar transistor coupled to cancel variance of a voltage drop based on temperature on the first bipolar transistor.

7. The power converter of claim 1 wherein the energy transfer element comprises an inductor.

8. The power converter of claim 1, wherein the capacitor is a first capacitor, the power converter further comprising a second capacitor coupled across the first power converter output and a third capacitor coupled across the second power converter output.

9. The power converter of claim 1, wherein the capacitor is a first capacitor, the power converter further comprising a second capacitor coupled across the first and second power converter outputs.

10. The power converter of claim 1 wherein the first and second power converter outputs are coupled to a common ground terminal.

11. The power converter of claim 1, wherein the conduction path is a first conduction path, wherein the switch is coupled to provide the first conduction path when the current in the energy transfer element is coupled to increase when the voltage across the energy transfer element is a difference between an input voltage at the power converter input and the first output voltage, and wherein the switch is coupled to provide a second conduction path when the current in the energy transfer element is coupled to decrease when the voltage across the energy transfer element is the sum of the first and second output voltages.

12. The power converter of claim 1 wherein the control circuit further includes circuitry to employ at least one of constant frequency pulse width modulation (PWM), variable frequency PWM, or on/off control.

13. The power converter of claim 1 wherein the switch is coupled to be set in one of three settings, wherein when the switch is in a first setting, a current in the energy transfer element is the same as the input current supplied from the power converter input, wherein when the switch is in a second setting, the current in the energy transfer element is the same as a freewheeling current from the second power converter output, and wherein when the switch is in a third setting, the current in the energy transfer element is zero.

14. The power converter of claim 1, further comprising a diode coupled between the second output and the switch, wherein the capacitor is coupled to charge to the voltage approximately equal to the sum of the first and second output voltages when the diode is conducting a freewheeling current.

15. The power converter of claim 14, wherein the diode is a first diode having a cathode coupled to the second terminal of the capacitor and an anode coupled to the second output, the power converter further comprising a second diode having a cathode coupled to the third terminal of the capacitor and an anode coupled to the first output.

16. The power converter of claim 1, wherein the shunt circuit comprises:

a first transistor coupled across the first output; and

a second transistor having a base terminal coupled to a base terminal of the first transistor and an emitter terminal coupled to receive the second voltage reference, wherein a base to emitter voltage of the first transistor is substantially equal to a base to emitter voltage of the second transistor for temperature compensation.

17. A power converter, comprising:

an energy transfer element coupled between a power converter input and first and second power converter outputs;

a switch having a first terminal coupled to the energy transfer element to provide a conduction path for the energy transfer element to receive an input current supplied from the power converter input;

a control circuit coupled to the switch to control switching of the switch to generate a first output voltage at the first power converter output and a second output voltage at the second power converter output, wherein the first output voltage is regulated in response to a voltage reference, wherein a current in the energy transfer element is coupled to increase when a voltage across the energy transfer element is a difference between an input voltage at the power converter input and the first output voltage, wherein the current in the energy transfer element is coupled to decrease when the voltage across the energy transfer element is a sum of the first and second output voltages;

a capacitor having a second terminal and a third terminal, wherein the second terminal is coupled to the first terminal of the switch and the third terminal is coupled between the first power converter output and a feedback terminal of the control circuit, wherein the capacitor is coupled to charge to a voltage approximately equal to the sum of the first and second output voltages, wherein the control circuit is further coupled to regulate the sum of the first and second output voltages in response to a signal proportional to the voltage on the capacitor; and

a shunt circuit coupled across the second power converter output to regulate the first output voltage at the first power converter output in response to the voltage reference.

18. The power converter of claim 17, further comprising a diode coupled between the second output and the switch, wherein the capacitor is coupled to charge to the voltage approximately equal to the sum of the first and second output voltages when the diode is conducting a freewheeling current.

19. The power converter of claim 18, wherein the diode is a first diode having a cathode coupled to the second terminal of the capacitor and an anode coupled to the second output, the power converter further comprising a second diode having a cathode coupled to the third terminal of the capacitor and an anode coupled to the first output.

20. The power converter of claim 17, wherein the shunt circuit comprises:

a first transistor coupled across the first output; and

a second transistor having a base terminal coupled to a base terminal of the first transistor and an emitter terminal coupled to receive the second voltage reference, wherein a base to emitter voltage of the first transistor is substantially equal to a base to emitter voltage of the second transistor for temperature compensation.