Driving circuit, control circuit and method for refreshing bootstrap voltage of switching converter

Abstract

Disclosed are a drive circuit, a control circuit and a bootstrap voltage refreshing method for a buck-boost switching converter. The buck-boost switching converter includes a first power switch and a second power switch. The drive circuit includes a first bootstrap capacitor and a second bootstrap capacitor, respectively providing a first bootstrap voltage for driving the first power switch and a second bootstrap voltage for driving the second power switch. When the converter works in buck mode and the second bootstrap voltage is lower than the second preset threshold voltage, the driving circuit charges the second bootstrap capacitor with the first bootstrap voltage when the first power switch is turned on; When the converter works in boost mode and the first bootstrap voltage is lower than the first preset threshold voltage, the driving circuit charges the first bootstrap capacitor with the second bootstrap voltage when the second power switch is turned on. The driving circuit has a simple circuit topology and can automatically refresh the first and second bootstrap voltages.

Description

technical field [0001] The invention relates to an electronic circuit, in particular to a driving circuit, a control circuit and a bootstrap voltage refreshing method of a buck-boost switching converter. Background technique [0002] The buck-boost switching converter can convert the input voltage to an output voltage higher than, equal to or lower than the input voltage, and the input voltage conversion range is wide, so it has been greatly developed in the field of power supply. [0003] figure 1 It is a schematic circuit diagram of a conventional buck-boost switching converter 50 with a driving circuit. The buck-boost switching converter 50 converts an input voltage V1N into an output voltage VOUT, and includes power switches 11 - 14 , an inductor 15 and a capacitor 16 . The first power switch 11 and the third power switch 13 are coupled in series between the input terminal of the buck-boost switching converter 50 and the logic ground. A common terminal of the first po...

AI Technical Summary

Problems solved by technology

However, in the step-down mode, it is necessary to keep the second power switch 12 normally on and the fourth power switch 14 normally off. At this time, the voltage of the second switch node SW2 is equal to the output voltage VOUT, so the power supply voltage signal VCC cannot be supplied to the second self. The charging of the boost capacitor 33 to a sufficient level causes the second bootstrap voltage signal VBST2 to drop, which is not enough to make the second power switch 12 turn on and off normally, and the buck-boost switching converter 50 cannot work normally.

As another example, in the boost mode, it is necessary to keep the first power switch 11 normally on and the third power switch 13 normally off. At this time, the voltage of the first switch node SW1 is equal to the input voltage VIN, so the power supply voltage signal VCC cannot be given to the first power switch 13. The bootstrap capacitor 31 is charged to a sufficient level, causing the first bootstrap voltage signal VBST1 to drop, which is not enough to make the first power switch 11 turn on and off normally, and the buck-boost switching converter 50 cannot work normally.

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