A loop detection and control circuit

Abstract

The invention belongs to the technical field of electronic device detection and the field of switching power supply, and relates to a loop detection and control circuit, which includes a primary circuit as an input terminal, and its primary winding is connected to a main control chip U1, and the main control chip U1 is connected to a voltage divider. There is an auxiliary winding of the transformer T1, and the auxiliary winding is connected to a voltage dividing resistor to supply power to the FB1 pin of the main control chip U1, so that the loop detection and control circuit working mode is switched by the FB1 pin; the secondary circuit, as an output terminal, The secondary winding is connected to the main control chip U2; the QG pin of the main control chip U2 performs RC damping connection or short-circuit or semi-short-circuit connection of the secondary winding; the first voltage of the FB1 pin is preset in the main control chip U1 The threshold is used to switch the working mode of the circuit, and the second voltage threshold is used to judge the output voltage of the secondary circuit. The invention can realize multi-loop detection and self-power supply functions, thereby saving space and reducing costs.

Description

technical field [0001] The invention belongs to the technical field of electronic device detection and relates to a loop detection and control circuit. Background technique [0002] At present, the main switching power supplies on the market, especially low-power power supplies within 100W, no matter DC to DC or AC to DC, the main control circuit can usually only be made into constant current mode (commonly used in LED circuits), constant voltage plus constant current Mode (both PSR architecture and SSR architecture can be realized), constant voltage mode (conventional SSR architecture can be realized), or constant power mode (SSR architecture can be realized). However, since the feedback usually only has one output voltage feedback loop, it is impossible to realize the constant current mode in accordance with the requirements under certain conditions, and switch to the constant power mode under another condition. To realize this function, only constant power or constant cur...

AI Technical Summary

Problems solved by technology

[0008] At present, PSR primary side feedback is used for fast charging, and some Ewatts also use transformer mutual inductance feedback. When square wave detection technology is used to transmit current and voltage signals, it takes a long time to transmit the voltage and current signals to the primary. After the primary receives the signal, it readjusts. FB foot reference constant pressure and CS foot current reference, time delay, usually need several MS or even dozens of MS, and the detection and judgment are complicated and only digital chips can be used, which is costly; in addition, PI also uses mutual inductance feedback, but it is not directly in In the transformer, the process is more complicated, and it straddles the primary pole, taking up a lot of space

And these two are powered by auxiliary windings, resulting in the need for additional voltage regulation on VCC

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