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US 2016/0261201 A1Published application
Power supply with near valley switching
AssigneeFairchild Semiconductor Corporation
InventorsZhibo TAO, Jung-Sheng CHEN, Li LIN, Kai-Fang WEI, Chih-Hsien HSIEH, Hangseok CHOI, Yue-Hong TANG
Life of this patent
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Abstract
A switched-mode power supply with near valley switching includes a quasi-resonant converter. The converter includes a switch element that is turned on not only at the valley, but also in a window range of ΔtNVW close to the valley, where the voltage across the switch element is at its minimum. This advantageously reduces switching loss and maintains a balance between efficiency and frequency variation.
Claims20
An electrical circuit comprising:
- a controller that is configured to detect a zero-crossing of a drain-source resonance voltage of a metal oxide field effect transistor (MOSFET) that is coupled to a primary winding of a transformer relative to an input voltage, to generate a signal indicating occurrence of a near valley window time period in response to detecting the zero-crossing of the drain-source resonance voltage of the MOSFET, and to turn on the MOSFET within a range of time during the near valley window time period when a blanking period during which the MOSFET is prohibited from being turned on ends within the near valley window time period.
A method comprising:
- sensing a drain-source resonance voltage of a primary switch at resonance, the primary switch being at resonance when an inductance of a primary winding of a transformer to which the primary switch is coupled resonates with a capacitance when the primary switch is turned off;
- allowing the primary switch to be turned on within a range of time during a near valley window time period that occurs during a negative half cycle of the drain-source resonance voltage of the primary switch relative to an input voltage;
- and
- turning on the primary switch during the near valley window time period.
1 more element
A switched mode power supply comprising:
- a transformer having a primary winding and a secondary winding;
- a metal oxide semiconductor (MOS) transistor that is coupled to the primary winding;
- and
- a controller that is configured to control a switching operation of the primary switch to couple and decouple the primary winding to an input voltage, to detect a drain-source resonance voltage of the MOS transistor at resonance, to start a near valley window time period in response to zero-crossing of the drain-source resonance voltage, and to allow the MOS transistor to be turned on within a range of time during the near valley window time period.
1 more element
Dependencies are inferred from the claim text.