A secondary side synchronous rectifier circuit with thermal protection and electronic equipment

Abstract

The invention discloses a secondary-side synchronous rectification circuit and electronic equipment with thermal protection. By adding a temperature detection unit in the secondary-side synchronous circuit, the temperature of a power tube is monitored, so that when the temperature of the secondary-side synchronous rectification circuit rises to a thermal level, the temperature of the power tube is monitored. When protecting the threshold value of temperature detection, the temperature detection unit detects the circuit temperature, and outputs the corresponding feedback amount to the optocoupler according to the detected different temperatures, and the optocoupler outputs the corresponding feedback amount to the original according to the received feedback amount. side control module, so as to control the primary side control module to control the size of the primary side input power, by reducing the input power to achieve the effect of reducing the temperature of the secondary side synchronous rectifier circuit, and under normal working conditions, through the constant voltage and constant current unit. The power consumed by the load is detected and controlled, so that the secondary side synchronous rectifier circuit works in a stable state, so that the secondary side synchronous rectifier circuit can not only achieve constant temperature operation, but also realize the thermal protection of the secondary side synchronous rectifier circuit.

Description

technical field [0001] The invention relates to the field of power electronic conversion, in particular to a secondary-side synchronous rectification circuit with thermal protection and electronic equipment. Background technique [0002] With the development of modern electronic technology, the working voltage of the circuit is getting lower and lower and the current is getting higher and higher, so the overall power loss of the circuit has become an important consideration in circuit design. Traditional secondary rectifier circuits usually use Schottky rectifier diodes, but as the operating voltage of the circuit gets lower and lower, the efficiency of the circuit also decreases. Synchronous Rectification (Synchronous Rectification, SR) technology is widely used in low-voltage, high-current power modules due to its low power consumption. [0003] Although the synchronous rectification technology adopts the method of replacing the Schottky rectifier diode with the power tub...

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Problems solved by technology

[0003] Although the synchronous rectification technology adopts the method of replacing the Schottky rectifier diode with the power tube to greatly improve the efficiency of the circuit, but the power device will increase the heat due to the increase of the output power. When it exceeds 165 degrees, the synchronous rectification control circuit and There will be thermal breakdown in the power tube, which will damage the chip. In most existing secondary side synchronous rectification circuits, the thermal protection method adopted is to turn off the power NMOS (N-Metal-Oxide-Semiconductor) tube of the synchronous rectification, but in fact After turning off the NMOS, because the parasitic diode of the power NMOS is turned on, the circuit is still in the conduction state, and the conduction voltage drop is close to 1V, and the conduction voltage drop is larger, so it will cause the instability of the working system and cause oscillation, and there is a huge The hidden danger of abnormal thermal protection

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