Synchronous rectification control circuit and flyback switching power supply
A control circuit and synchronous rectification technology, applied in the direction of control/regulation system, high-efficiency power electronic conversion, electrical components, etc., can solve the problem that it is difficult to avoid parasitic attenuation oscillation and misoperation
Pending Publication Date: 2020-10-30
BCD (SHANGHAI) MICRO ELECTRONICS LTD
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Problems solved by technology
Therefore, controlling the rectifier tube M2 according to the amplitude of the voltage at both ends of the secondary winding is difficult to avoid malfunctions caused by parasitic attenuation oscillations
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[0044] The core of the present invention is to provide a synchronous rectification control circuit and a flyback switching power supply, which can use the volt-second product of the voltage at both ends of the secondary winding as the judgment standard to distinguish the two secondary windings aroused by the normal primary switching action. Terminal voltage and parasitic attenuation oscillation, so as to avoid the phenomenon of mistakenly turning on the secondary side rectifier tube during parasitic attenuation oscillation; moreover, the volt-second product threshold value of this application can follow the adaptive adjustment of the output voltage of the switching power supply, so it is suitable for multi-output voltage Switching power system.
[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described b...
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The invention discloses a synchronous rectification control circuit and a flyback switching power supply. A volt-second integrating circuit is used for obtaining a volt-second product of voltages at two ends of a secondary winding of the switching power supply; a volt-second product threshold adaptive circuit is used for changing the volt-second product threshold along with the change of the output voltage of the switching power supply to obtain a volt-second product threshold in positive correlation with the output voltage of the switching power supply; a comparison circuit is used for generating a turn-on permission signal if the current volt-second product is greater than a volt-second product threshold value; and a rectifier tube control circuit is used for controlling the rectifier tube to be conducted after receiving the turn-on permission signal. Visibly, the volt-second product of the voltages at the two ends of the secondary side winding is used as a judgment standard, the voltages at the two ends of the secondary side winding excited by normal primary side switch action and parasitic attenuation oscillation are distinguished, and therefore the phenomenon that a secondaryside rectifier tube is turned on by mistake when parasitic attenuation oscillation occurs is avoided; and moreover, the volt-second product threshold value can be adaptively adjusted along with the output voltage of the switching power supply, thereby being suitable for a switching power supply system with multiple output voltages.
Description
technical field [0001] The invention relates to the field of switching power supply control, in particular to a synchronous rectification control circuit and a flyback switching power supply. Background technique [0002] The flyback switching power supply controlled by the primary side has gradually become an important electronic component power supply device due to its small size and high efficiency. Generally, a rectifier diode is connected in series at the output end to provide a DC output voltage. With the development of electronic technology, the output voltage required by the load electronic components is getting lower and higher, and the output power is getting higher and higher. Therefore, the forward conduction voltage drop of the rectifier diode has become the main factor limiting the efficiency of the switching power supply. [0003] The commonly used solution at present is to use a rectifier to simulate a diode for rectification, which is the so-called synchrono...
Claims
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Login to View More IPC IPC(8): H02M3/335
CPCH02M3/33592Y02B70/10
Inventor 窦森邹聪丁雪征
Owner BCD (SHANGHAI) MICRO ELECTRONICS LTD