Primary side voltage sense for AC/DC power supplies

• US 20060083032A1
• Filed: 10/15/2004
• Published: 04/20/2006
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Jenkins, Daniel E., McDonald, Brent A.
• Granted Patent: US 7,280,376 B2
• Time in Patent Office: Days
• US Class Current: 363/21.120
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• 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

In a method and system for providing isolated power, a flyback controller includes a transformer operable to receive a primary voltage input and generate a secondary voltage output. A switch electrically coupled in series with a primary side of the transformer receives a control signal for controlling a duty cycle of the primary voltage. A controller is operable to generate the control signal responsive to receiving a plurality of inputs from the primary side. The controller regulates the secondary voltage output without receiving feedback input from a secondary side of the transformer by computing the secondary voltage as a predefined function of the plurality of the inputs when the switch is open.

Claims

1. A flyback converter comprising:

a transformer operable to receive a primary voltage input and generate a secondary voltage output, wherein the transformer generates the secondary voltage output responsive to a duty cycle of the primary voltage input;

a switch electrically coupled in series with a primary side of the transformer, wherein the switch receives a control signal for controlling the duty cycle; and

a controller operable to generate the control signal responsive to receiving a plurality of inputs from the primary side, wherein the secondary voltage is computed as a predefined function of the plurality of the inputs when the switch is open.

2. The converter of claim 1, wherein the plurality of inputs include the primary voltage input, a primary current flowing through the primary side, and a temperature input indicative of a temperature measurement of the transformer.

3. The converter of claim 1, wherein the predefined function is a proportional function, wherein the secondary voltage is proportional to the primary voltage input, a turns ratio of the transformer and the duty cycle.

4. The converter of claim 1, the controller adjusts the duty cycle to enable a continuous conductance mode (CCM), wherein a secondary current of the transformer is greater than zero while operating in the CCM.

5. The converter of claim 1, wherein the controller includes a sense and logic circuit operable to receive the plurality of the inputs and generate a plurality of computed outputs, wherein the plurality of computed outputs include a first computed output computed as the primary voltage input multiplied by a turns ratio of the transformer, and a second computed output indicative of an error in the secondary voltage output, wherein the error is caused as a result of drops in voltages across components included in a secondary side of the transformer.

6. The converter of claim 5, wherein the components include a secondary winding of the transformer, a conductor path to a load, and a synchronous rectifier switch.

7. The converter of claim 6, wherein the second computed output is computed by adding resistances of the secondary winding of the transformer, the conductor path to the load, and the synchronous rectifier switch to compute a combined resistance of the secondary side, wherein the combined resistance is multiplied by a primary current flowing through the primary side and the turns ratio.

8. The converter of claim 5, wherein the second computed output is further adjusted in response to the temperature input.

9. The converter of claim 5, wherein the controller includes a ramp generator circuit operable to generate a ramp signal having a selectable frequency, wherein the control signal is disabled when a value of the ramp signal is greater than a third computed output, wherein the third computed output regulates the secondary voltage output without receiving feedback from the secondary side.

10. The converter of claim 9, wherein the third computed output is computed as a function of the first computed output and the second computed output being subtracted from a voltage reference defined for a load voltage.

11. A method for controlling a flyback converter, the method comprising:

receiving a plurality of inputs from a primary side of a transformer included in the converter;

computing a secondary voltage output of the transformer as a predefined function of the plurality of the inputs; and

controlling a duty cycle of a primary voltage input of the transformer without receiving feedback from a secondary side of the transformer, the duty cycle being controlled by a switch coupled in series with the primary side in response to receiving the plurality of the inputs.

12. The method of claim 11, when the computing is performed when the switch is open.

13. The method of claim 11, wherein the plurality of inputs include the primary voltage input, a primary current flowing through the primary side, and a temperature input indicative of a temperature measurement of the transformer.

14. The method of claim 11, wherein the predefined function is a proportional function, wherein the secondary voltage is proportional to the primary voltage input, a turns ratio of the transformer and the duty cycle.

15. The method of claim 11, wherein the duty cycle is controlled to enable a continuous conductance mode (CCM) of operation, wherein a secondary current of the transformer is greater than zero while operating in the CCM.

16. The method of claim 11, wherein the computing comprises:

generating a plurality of computed outputs in response to receiving the plurality of the inputs, wherein the plurality of computed outputs include a first computed output computed as the primary voltage multiplied by a turns ratio of the transformer, and a second computed output indicative of an error in the secondary voltage output, wherein the error is caused as a result of drops in voltages across components included in the secondary side.

17. An information handling system (IHS) comprising:

a processor; and

a flyback converter operable to provide power to the processor, the converter including;

a transformer operable to receive a primary voltage input and generate a secondary voltage output, wherein the transformer generates the secondary voltage output responsive to a duty cycle of the primary voltage input;

a switch electrically coupled in series with a primary side of the transformer, wherein the switch receives a control signal for controlling the duty cycle; and

a controller operable to generate the control signal responsive to receiving a plurality of inputs from the primary side, wherein the secondary voltage is computed as a predefined function of the plurality of the inputs when the switch is open.

18. The system of claim 17, wherein the controller regulates the secondary voltage output without receiving feedback input from a secondary side of the transformer.

19. The system of claim 17, wherein the plurality of inputs include the primary voltage input, a primary current flowing through the primary side, and a temperature input indicative of a temperature measurement of the transformer.

20. The system of claim 17, wherein the controller generates a plurality of computed outputs in response to receiving the plurality of the inputs, wherein the plurality of computed outputs include a first computed output computed as the primary voltage multiplied by a turns ratio of the transformer, and a second computed output indicative of an error in the secondary voltage output, wherein the error is caused as a result of drops in voltages across components included in a secondary side of the transformer.