Controlling method and apparatus for four switch step-up step-down DC-DC converter

Abstract

The invention discloses a method for controlling a four-switch buck-boost DC-DC converter. The method integrates the advantages of the linear control and the nonlinear control, adopts the control of a current mode during the steady state and carries out the voltage sampling at a voltage output terminal; the sampling voltage and the benchmark voltage are input in an error amplifier; the output signal of the error amplifier is used as the benchmark input of a current comparator; the output terminal of the error amplifier is also connected with a compensation network which consists of resistances and capacitors; when the loaded jumps, the nonlinear control is carried out. The invention also discloses a device used for implementing the method. The invention realizes the application of the nonlinear control on the four-switch buck-boost topology, simultaneously solves the technical problem that the oscillation occurs when the load jumps during the nonlinear control process, thereby leading the output voltage to reach the stable value quickly, and improving the response speed of the buck-boost converter.

Description

technical field [0001] The invention relates to a control method of a buck-boost DC-DC converter and a buck-boost DC-DC converter for realizing the method. Background technique [0002] In portable devices powered by lithium batteries, it is very important to improve battery utilization. The normal operating voltage range of a single-cell lithium battery is 2.7V to 4.2V, and digital modules such as processors and decoders in the device are generally powered by 3.3V, so a DC- The DC converter can effectively improve the utilization rate of the battery. [0003] In the topology that can realize the buck-boost function, such as figure 1 The four-switch buck-boost topology shown can be regarded as a buck topology and a boost topology cascaded without increasing the number of inductors. The four-switch single-inductor buck-boost topology includes field effect switch tubes 1, 2, 3 and 4, an inductor 5 and a capacitor 6. In addition to realizing the buck-boost function, this co...

AI Technical Summary

Problems solved by technology

This is why voltage loop control is always slower than current loop control

[0006] In addition, the nonlinear control strategy in the prior art is generally easier to implement in buck control, but in boost control, the above-mentioned nonlinear control is not applicable

To put it simply, in the boost topology, when jumping from light load to heavy load, the corresponding full duty cycle control only realizes the input to charge the inductor, but the energy is not transferred to the output, so the output voltage still cannot recover quickly

However, when jumping from heavy load to light load, the zero duty cycle control only realizes that the input is always transmitted to the output. Although the input current will gradually decrease, the output voltage will gradually decrease, but the speed is not fast.

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