Buck-boost DC converter and its control method

Abstract

The present disclosure relates to a BUCK-BOOST DC converter and a control method thereof. The converter includes a BUCK-BOOST circuit module, a drive module, an output voltage sampling module, a mode control module and a current detection module, and the current detection module is connected to the BUCK-BOOST circuit module for detecting the inductance in the BUCK-BOOST circuit current, and send the current detection signal to the mode control module; the mode control module generates a corresponding PWM mode control signal or PSM mode control signal according to the current detection signal and the output voltage sampling signal, and according to the PWM mode control signal or PSM mode control signal , the driving module drives the BUCK-BOOST circuit to work in the BUCK mode in the PWM mode, the BOOST mode or the BUCK-BOOST mode or the BUCK-BOOST mode in the PSM mode. The disclosure achieves the purpose of outputting a stable voltage in the full load range of the DC converter, and reduces the power consumption of the switching tube and the static loss of the circuit during the mode switching process, thereby improving the conversion efficiency.

Description

technical field [0001] The present disclosure relates to the technical field of power supplies, and in particular, to a BUCK-BOOST DC converter and a control method thereof. Background technique [0002] With the rapid development of electronic technology, all kinds of mobile terminals represented by smart phones and tablet computers have entered thousands of households, and the industry is also making further technological development. It is hoped that through various functions and perfect and reliable Performance brings more convenience to people's life. Among them, standby time and terminal heating are the performances that the industry is trying to improve. At present, the standby time of most terminals is not long enough, and the problem of terminal heating still needs to be further optimized. In order to solve the above two problems, one method is to strive to increase the battery capacity, improve the thermal conductivity of materials, etc.; the other method is to o...

AI Technical Summary

Problems solved by technology

There are two problems with this solution, first: if the battery is full capacity, its output voltage will be relatively high, then the efficiency of the LDO will be very low, which will shorten the battery life and cause more heat

Second: If the battery capacity is getting lower and lower, its output voltage will also be lower and lower. When the voltage is lower than 3.3V, the LDO will not be able to output 3.3V voltage for system use. In order to ensure the stability and reliability of the system, The solution is generally when the battery voltage drops to about 3.6V, it will alarm for low battery, or even shut down directly

But the problem with this solution is that in the BUCK-BOOST mode, the power switches in the circuit will be turned on or off in pairs at the same time according to a certain timing (such as Image 6 P1 and P3 are turned on or off at the same time, P2 and P4 are turned on or off at the same time), so the dynamic loss is very large, which affects the efficiency

Moreover, due to the influence of factors such as the on-resistance of the switch tube and the parasitic resistance of the wiring, the effective value of the input voltage will change with the change of the load. That is to say, when the load becomes larger, the effective input voltage will decrease. This will cause the converter's operating mode to change depending on the input voltage

If the working mode of the converter is controlled according to the ideal relationship between the input voltage and the output voltage, it is obvious that the buck-boost type DC converter will not be in the best working state

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