Switch control circuit and control method

Abstract

The invention discloses a switch control circuit and control method. When an external input voltage is needed to be switched, a logic control circuit outputs a feedback control signal, a feedback circuit participating the switching process is used for selectively accessing a reference voltage signal to a feedback loop needed to be switched according to a feedback control signal, so that the switch action of the corresponding switch circuit is controlled, and the purpose of switching the input voltage is achieved. By the switching mode, an output voltage can be enabled not to be drop during the channel switching process, and an output value is stable.

Description

technical field [0001] The invention relates to the field of switching power supplies, and more specifically, to a switching control circuit and a control method. Background technique [0002] In some applications with multiple input interfaces and single output ports, it is necessary to switch between different input power sources to output desired output voltage signals. Such as Figure 1A Shown is the first voltage switching method in the prior art, such as Figure 1A In the circuit diagram shown, taking two input interfaces as an example, the switching of multiple inputs is realized through the unidirectional conduction characteristic of the diode. Figure 1B shown as Figure 1A The waveform diagram shown. [0003] A diode is connected to the branch of each input port, the anode of the diode is connected to the input port, and the cathode is connected to the output port. When the voltage VIN1 of the first input terminal needs to be used, the voltage VIN1 is powered on,...

AI Technical Summary

Problems solved by technology

Compared with the first solution, this method can reduce the system loss due to the use of transistors, but the disadvantage is that in order to achieve the effect of unidirectional conduction (to prevent current backflow), the MOS transistor will be turned off before the ready voltage switching and after the complete switching, such as Figure 2B From t1 to t3, this will result in an output conversion drop voltage that is one diode drop lower than the output voltage during the switching process, such as Figure 2B In some applications (such as USB PD) the output conversion drop voltage of a diode drop voltage has far exceeded the allowable range

The disadvantage of this method is that there will be a drop in the output voltage during the switching process, and the value of this drop is related to the load, the size of the output capacitor, and the length of the dead time of the signal GATE1 and GATE2. When the output capacitor is small, it may be It leads to an unacceptable output voltage drop, and in some applications, there is an upper limit on the output capacitor, which causes greater fluctuations in the output voltage

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