Switch mode power supply controllers

• US 20080037294A1
• Filed: 06/07/2007
• Published: 02/14/2008
• Est. Priority Date: 05/23/2006
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Cambridge Semiconductor Limited (Power Integrations Incorporated)
• Inventors: Kumar, Jay, Lalithambika, Vinod A., Indika de Silva, Mahesh Devarahandi
• Granted Patent: US 7,499,295 B2
• Time in Patent Office: Days
• US Class Current: 363/21.12
• 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: 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

This invention generally relates to discontinuous conduction mode switch mode power supply (SMPS) controllers employing primary side sensing. We describe an SMPS controller which integrates a feedback signal from a point determined by a target operating voltage to a peak or trough of an oscillatory or resonant portion of the feedback signal when substantially no energy is being transferred to the SMPS output. When regulation is achieved this value should be zero; the difference from zero can be used to regulate the output voltage of the SMPS.

Claims

1. A method of regulating the output of a switch mode power supply (SMPS) operating in a discontinuous conduction mode, the method comprising:

monitoring a feedback signal from a primary or auxiliary winding of a magnetic energy storage device forming part of an output circuit of said SMPS, said feedback signal including a decaying portion representing a decaying voltage in said output circuit of said SMPS followed by an oscillatory portion when substantially no energy is being transferred to said SMPS output;

integrating said feedback signal from a point in said decaying portion of said feedback signal defined by a target output voltage for said SMPS; and

regulating said SMPS output responsive to a comparison, at a defined point in said oscillatory portion of said feedback signal, of a result of said integrating with a second, reference value.

2. The method of claim 1, wherein regulating includes regulating said feedback signal between two amplitudes such that said feedback signal maintains an integrated value of substantially zero.

3. The method of claim 1, wherein integrating includes integrating after said feedback signal is less than or equal said target output voltage.

4. The method of claim 1, wherein regulating includes generating a reset signal when said feedback signal is greater than said target output voltage.

5. The method of claim 1, wherein regulating includes regulating a duty cycle of a logical signal generator in response to said feedback signal being less than said target output voltage.

6. A system for regulating the output of a switch mode power supply (SMPS) operating in a discontinuous conduction mode, the system comprising:

means for monitoring a feedback signal from a primary or auxiliary winding of a magnetic energy storage device forming part of an output circuit of said SMPS, said feedback signal including a decaying portion representing a decaying voltage in said output circuit of said SMPS followed by an oscillatory portion when substantially no energy is being transferred to said SMPS output;

means for integrating said feedback signal from a point in said decaying portion of said feedback signal defined by a target output voltage for said SMPS; and

means for regulating said SMPS output responsive to a comparison, at a defined point in said oscillatory portion of said feedback signal, of a result of said integrating with a second, reference value.

7. The system of claim 6, wherein said means for integrating includes means for differentiating said feedback signal.

8. The system of claim 6, wherein said means for regulating includes a circuit for comparing a timing signal phase with a zero crossing point of a differential voltage waveform associated with said primary winding.

9. The system of claim 6, wherein said means for integrating includes means for producing a reset signal responsive to said target output voltage.

10. The system of claim 9, wherein said means for integrating includes means for generating a phase lag signal using said feedback signal, and wherein said means for generating is responsive to said means for producing a reset signal.

11. A power converter comprising:

a transformer and a switch that electrically couples and decouples the transformer to and from a power source; and

a sensing module to indirectly sense an output voltage of said power converter and thereby regulate an output of said power converter;

wherein

said sensing module is configured to integrate part of a primary or auxiliary winding flyback voltage waveform of the transformer between two points, said two points including a resonant portion of said voltage waveform, such that when in regulation said part of said waveform between said two points has an integrated value of substantially zero.

12. The converter of claim 11, wherein said sensing module includes two output nodes coupled to a digital controller, each node to provide zero crossing information to said digital controller.

13. The converter of claim 12, wherein one of said two output nodes is configured to provide zero crossing information based on a slope of said flyback voltage waveform.

14. The converter of claim 11, wherein said sensing module is configured to provide information for generating an error signal when out of regulation.

15. The converter of claim 11, wherein said sensing module is configured to substantially prevent said integration of said flyback voltage waveform if a magnitude of said flyback voltage waveform exceeds a target operating voltage.