Flight capacitance balancing circuit and method for three-level step-down DC-DC converter

Abstract

The invention relates to a three-level step-down DC-DC converter flight capacitance balancing circuit and method, and belongs to the field of power management circuits. By adding an auxiliary capacitor CA and switches S1, S2 and S3 which are equal to a flying capacitor CF in capacitance value, and by controlling the series-parallel connection mode of the flying capacitor CF and the auxiliary capacitor CA, the balance control over the voltage of the flying capacitor is achieved. According to the invention, in the two modes that the duty ratio D is smaller than 0.5 and larger than 0.5, the balance adjustment of the flight capacitor voltage of the three-level step-down converter can solve the problem that the flight capacitor voltage of the three-level buck converter is unbalanced in different duty ratio states, and the system stability is improved. Compared with a control scheme (CF-AOT) with fixed frequency and adaptive turn-on time proposed in the background technology, the structure can realize balance control of the flight capacitor voltage VCF without a complex control loop, and has the advantages of simple structure, easy adjustment and strong stability.

Description

technical field [0001] The invention belongs to the field of power management circuits, in particular to a three-level step-down DC-DC converter. Background technique [0002] Due to the continuous expansion of application scenarios such as lithium-ion batteries and Internet of Things products, the demand for step-down DC-DC converters is also growing rapidly, especially for step-down converters with low conversion ratios, but with such characteristics The traditional two-level buck converter usually has large parasitic capacitance and switching loss, and also produces large inductor current ripple. [0003] The normalized inductor current ripple and output voltage ripple of the three-level step-down converter can be reduced by 4 times and 8 times respectively, which is very beneficial to reduce the conduction loss and switching loss of the converter. However, the three-level conversion In actual work, the converter will be affected by factors such as switching frequency, p...

AI Technical Summary

Problems solved by technology

[0002] Due to the continuous expansion of application scenarios such as lithium-ion batteries and Internet of Things products, the demand for step-down DC-DC converters is also growing rapidly, especially for step-down converters with low conversion ratios, but with such characteristics The traditional two-level buck converter usually has large parasitic capacitance and switching loss, and also produces large inductor current ripple

[0003] The normalized inductor current ripple and output voltage ripple of the three-level step-down converter can be reduced by 4 times and 8 times respectively, which is very beneficial to reduce the conduction loss and switching loss of the converter. However, the three-level conversion In actual work, the converter will be affected by factors such as switching frequency, parasitic capacitance, gate control signal, etc., which will cause the voltage of the flying capacitor to be unable to balance to the input voltage V IN half of , thus having a more significant impact on the system performance of the converter

However, the circuit design is complex, which increases the area and power consumption of the system, and the feedback loop may be easily affected by the operating conditions, which is not conducive to the normal operation of the converter.

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