Flyback switching power supply
First Claim
1. A flyback switching power supply, comprising a main power switch, a transformer and a rectifier, wherein the transformer comprises a primary winding and a secondary winding, the main power switch is connected with the primary winding, the rectifier is connected with the secondary winding, a control terminal of the main power switch is connected with a primary-side controller, a control terminal of the rectifier is connected with a secondary-side controller;
- wherein when an output voltage of the flyback switching power supply is lower than a first threshold value, the rectifier is controlled to be turned on for a transient period by the secondary-side controller;
wherein the primary-side controller is configured to detect a negative current flowing through the main power switch for determining whether the rectifier is turned on or not, to determine that the output voltage at secondary side is lower than a threshold voltage when the negative current reaches a second threshold value and to control the main power switch to be turned on when the negative current reaches the second threshold value.
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Accused Products
Abstract
A flyback switching power supply, comprising a main power switch, a transformer and a rectifier is described. The transformer comprises a primary winding and a secondary winding, the main power switch is connected with the primary winding, the rectifier is connected with the secondary winding. When the output voltage of the flyback switching power supply is lower than a first threshold value, the rectifier is controlled to be turned on for a transient period; by detecting the negative current flowing through the main power switch, performing integral operation on the voltage across the auxiliary winding, and sampling the peak voltage of the drain-to-source voltage of the main power switch for several times, whether the rectifier is turned on can be determined if the output voltage at the secondary side is lower than the threshold voltage, and the main power switch is controlled to be turned on accordingly.
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Citations
14 Claims
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1. A flyback switching power supply, comprising a main power switch, a transformer and a rectifier, wherein the transformer comprises a primary winding and a secondary winding, the main power switch is connected with the primary winding, the rectifier is connected with the secondary winding, a control terminal of the main power switch is connected with a primary-side controller, a control terminal of the rectifier is connected with a secondary-side controller;
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wherein when an output voltage of the flyback switching power supply is lower than a first threshold value, the rectifier is controlled to be turned on for a transient period by the secondary-side controller; wherein the primary-side controller is configured to detect a negative current flowing through the main power switch for determining whether the rectifier is turned on or not, to determine that the output voltage at secondary side is lower than a threshold voltage when the negative current reaches a second threshold value and to control the main power switch to be turned on when the negative current reaches the second threshold value. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A flyback switching power supply, comprising a main power switch, a transformer and a rectifier, wherein the transformer comprises a primary winding and a secondary winding, the main power switch is connected with the primary winding, the rectifier is connected with the secondary winding, a control terminal of the main power switch is connected with a primary-side controller, a control terminal of the rectifier is connected with a secondary-side controller;
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wherein when an output voltage of the flyback switching power supply is lower than a first threshold value, the rectifier is controlled to be turned on for a transient period by the secondary-side controller; wherein the flyback switching power supply further comprises an auxiliary winding coupled with the transformer, the auxiliary winding is connected with a voltage detecting module configured to detect a voltage across the auxiliary winding, to sample the voltage across the auxiliary winding for obtaining a first voltage signal, and to perform a volt-second integral operation to obtain a result, when the result of the volt-second integral operation reaches a third threshold value, it is determined that the output voltage of the flyback switching power supply is lower than the first threshold value and the main power switch is controlled to be turned on when the voltage across the auxiliary winding is less than a low threshold value. - View Dependent Claims (8, 9, 10, 11)
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12. A flyback switching power supply, comprising a main power switch, a transformer and a rectifier, wherein the transformer comprises a primary winding and a secondary winding, the main power switch is connected with the primary winding, the rectifier is connected with the secondary winding, a control terminal of the main power switch is connected with a primary-side controller, a control terminal of the rectifier is connected with a secondary-side controller;
wherein the flyback switching power supply further comprises an auxiliary winding coupled with the transformer, the auxiliary winding is connected with the primary-side controller;
when the output voltage of the flyback switching power supply is lower than a first threshold value, the rectifier is controlled to be turned on for a transient period by the secondary-side controller;
a voltage at a common node connected between the main power switch and the primary winding, a drain-to-source voltage of the main power switch or a voltage across the auxiliary winding is sampled to obtain a peak voltage, it is determined that the output voltage is lower than the first threshold value when a difference between the peak voltage sampled last time and the peak voltage sampled at current time reaches a difference threshold value, and the main power switch is controlled to be turned on by the primary-side controller when the voltage across the auxiliary winding is lower than a low threshold value.- View Dependent Claims (13, 14)
Specification