Flyback converter with secondary side regulation
First Claim
Patent Images
1. A flyback converter, comprising:
- a transformer, including;
a primary winding, including a first end to receive an input voltage signal, and a second end,a secondary winding, including a first end to provide an output voltage signal, and a second end, andan auxiliary winding including a first end, and a second end coupled with a first constant voltage node;
a first switch, including a first terminal coupled with the second end of the primary winding, a second terminal coupled with the first constant voltage node, and a first control terminal to receive a first switching control signal;
a second switch, including a first terminal coupled with the second end of the secondary winding, a second terminal coupled with a second constant voltage node, and a second control terminal to receive a second switching control signal;
a first control circuit, including an input coupled with the first end of the auxiliary winding to receive a first signal representing a voltage of the auxiliary winding, and an output to provide the first switching control signal to the first switch, the first control circuit operative in a first mode to independently turn the first switch on and off in a plurality of power transfer cycles, the first control circuit operative in a second mode to initiate a power transfer cycle by turning the first switch on and off, in response to detecting a predetermined cycle start request signal at the input; and
a second control circuit, including an output to provide the second switching control signal to the second switch, the second control circuit operative to generate the predetermined cycle start request signal to regulate the output voltage signal by turning the second switch on and off after a current of the secondary winding returns to zero in a given power transfer cycle to cause the first control circuit to initiate a new power transfer cycle.
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Accused Products
Abstract
Disclosed examples include flyback converters, control circuits and methods to facilitate secondary side regulation of the output voltage. A primary side control circuit operates a primary side switch to independently initiate power transfer cycles to deliver power to a transformer secondary winding in a first mode. A secondary side control circuit operates a synchronous rectifier or secondary side switch to generate a predetermined cycle start request signal via a transformer auxiliary winding to assume secondary side regulation and to cause the primary side controller to initiate new power transfer cycles.
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Citations
16 Claims
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1. A flyback converter, comprising:
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a transformer, including; a primary winding, including a first end to receive an input voltage signal, and a second end, a secondary winding, including a first end to provide an output voltage signal, and a second end, and an auxiliary winding including a first end, and a second end coupled with a first constant voltage node; a first switch, including a first terminal coupled with the second end of the primary winding, a second terminal coupled with the first constant voltage node, and a first control terminal to receive a first switching control signal; a second switch, including a first terminal coupled with the second end of the secondary winding, a second terminal coupled with a second constant voltage node, and a second control terminal to receive a second switching control signal; a first control circuit, including an input coupled with the first end of the auxiliary winding to receive a first signal representing a voltage of the auxiliary winding, and an output to provide the first switching control signal to the first switch, the first control circuit operative in a first mode to independently turn the first switch on and off in a plurality of power transfer cycles, the first control circuit operative in a second mode to initiate a power transfer cycle by turning the first switch on and off, in response to detecting a predetermined cycle start request signal at the input; and a second control circuit, including an output to provide the second switching control signal to the second switch, the second control circuit operative to generate the predetermined cycle start request signal to regulate the output voltage signal by turning the second switch on and off after a current of the secondary winding returns to zero in a given power transfer cycle to cause the first control circuit to initiate a new power transfer cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A control circuit to operate a switch connected to a primary winding of a transformer in a flyback converter, the control circuit comprising:
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a driver circuit including an output to provide a switching control signal to the switch; and a logic circuit coupled with the driver circuit, the logic circuit including an input coupleable to an auxiliary winding of the transformer to receive a signal representing a voltage of the auxiliary winding; wherein the logic circuit is operative in a first mode to independently cause the driver circuit to turn the switch on and off in a plurality of power transfer cycles to deliver power to a secondary winding of the transformer, the logic circuit operative in a second mode to initiate a power transfer cycle by turning the first switch on and off, in response to detecting a predetermined cycle start request signal at the input, wherein the logic circuit is operative to detect the predetermined cycle start request signal as an interruption of a ringing waveform of the signal at the input. - View Dependent Claims (15, 16)
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Specification