Method and apparatus for damping ringing in self-driven synchronous rectifiers
First Claim
1. A method of damping unwanted ringing in self-driven synchronous rectifiers including first and second self-driven synchronous devices each having respective activation terminals, comprising:
- (a) activating a first switching device to dampen any unwanted ringing on said activation terminal of said second self-driven synchronous device at a first time when said first self-driven synchronous device is active and said second self-driven synchronous device is inactive; and
(b) activating said second self-driven synchronous device at a second time when said first self-driven synchronous device is inactive.
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Abstract
Apparatus and method for eliminating cross conduction of self-driven synchronous rectifiers in power converters caused by non-idealized ringing of parasitic capacitances and inductors. In an exemplary embodiment, the apparatus includes synchronous rectifiers or some hybrid topology having at least one synchronous rectifier coupled to a damping circuit having at least one switching device. The switching device is activated (ON) at a time when at least one of the synchronous rectifiers is supposed to remain inactive (OFF). Accordingly, when the switching device is ON, the device effectively dampens any ringing present at the synchronous rectifier that may cause the rectifier to inappropriately transition ON. The damping circuit of the present invention utilizes the same signals present to control the synchronous rectifier(s) and requires no additional control circuitry. Additionally, the damping circuit dramatically improves the efficiency of self synchronous power converters and is topology independent.
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Citations
21 Claims
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1. A method of damping unwanted ringing in self-driven synchronous rectifiers including first and second self-driven synchronous devices each having respective activation terminals, comprising:
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(a) activating a first switching device to dampen any unwanted ringing on said activation terminal of said second self-driven synchronous device at a first time when said first self-driven synchronous device is active and said second self-driven synchronous device is inactive; and (b) activating said second self-driven synchronous device at a second time when said first self-driven synchronous device is inactive. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A power converter with improved efficiency and dampened ringing, comprising:
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self-driven synchronous rectifiers comprising first and second self-driven synchronous devices each having respective activation terminals; and a switching device, coupled to said self-driven synchronous rectifiers, activated at a time when said first self-driven synchronous device is active and said second self-driven synchronous device is inactive to dampen any unwanted ringing on said activation terminal of said second self-driven synchronous device. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A circuit for damping unwanted ringing in self-driven synchronous rectifiers, comprising:
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self-driven synchronous rectifiers comprising first and second self-driven synchronous rectifiers each having respective gate terminals; and means, coupled to said self-driven synchronous rectifiers, for conducting at a time when said first self-driven synchronous rectifier is active and said second self-driven synchronous rectifier is inactive to dampen any unwanted ringing on said gate terminal of said second self-driven synchronous device. - View Dependent Claims (18, 19, 20)
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21. A power converter, comprising:
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a primary side power circuit for receiving an input voltage; a secondary side power circuit, coupled to said primary side power circuit, for supplying an output voltage, comprising; first and second synchronous rectifiers each having a source, drain and gate, said first and second synchronous rectifiers are coupled together such that said drain of said first synchronous rectifier is coupled to said gate of said second synchronous rectifier and said drain of said second synchronous rectifier is coupled to said gate of said first synchronous rectifier; and a damping drive circuit coupled to said first and second synchronous rectifiers comprising; first and second switches, each having a source, drain and gate, said first and second switches are coupled together, such that said drain of said first switch is coupled to said gate of said second switch and said drain of said second switch is coupled to said gate of said first switch, wherein said first switch is active when said first synchronous rectifier is active and said second switch is active when said second synchronous rectifier is active.
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Specification