Multi-mode buck-boost converter and control method with shared capacitor
AssigneeJoulwatt Technology (Hangzhou) Co., Ltd.
InventorsLinjue Li, Yangwei Yu
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Abstract
The present disclosure relates to a buck-boost converter and a control method therefor. The buck-boost converter includes a boost unit and a buck unit. The boost unit has a first capacitor and a first group of switches. The buck unit has an inductor and a second group of switches. The buck-boost converter has a cascaded structure of the boost unit and the buck unit to achieve multiple voltage conversion modes. The inductor of the buck unit is coupled to the output terminal. Therefore, not only can it achieve a smooth transition of the DC output voltage, but also reduce voltage ripple and improve dynamic response speed.
Claims13
A buck-boost converter, comprising:
- a boost unit having a first capacitor and a first group of switches;
- and
- a buck unit having an inductor and a second group of switches,
- wherein the boost unit and the buck unit are coupled in sequence between an input terminal and an output terminal, with a first node being formed therebetween and the inductor of the buck unit is coupled to the output terminal,
- the boost unit and the buck unit operate together in various states to achieve a buck mode, a boost mode and a buck-boost mode, such that:
- in switching cycles of the buck mode, the boost unit is used to couple the input terminal with the first node, and to couple the first capacitor between the input terminal and ground,
- in switching cycles of the buck-boost mode, a first end of the first capacitor switches between the input terminal and the inductor, and a second end of the first capacitor switches between the input terminal and ground,
- wherein the first group of switches are turned on and off according to a first control signal, the second group of switches are turned on and off according to a second control signal to control charging and discharging of the first capacitor and the inductor to obtain a DC output voltage related to the duty cycles of the first control signal and the second control signal, the first control signal and the second control signal having the same switching period,
- wherein the DC output voltage of the buck-boost converter in a steady state in continuous switching cycles is as follows:
- Vout=2*D1*Vin+D2*Vin,
- where Vout represents an output voltage, Vin represents an input voltage, D1 represents a duty cycle of the first control signal, and D2 represents a duty cycle of the second control signal.
A control method for a buck-boost converter, the buck-boost converter comprising a first capacitor and an inductor, the control method comprising:
- selecting a conversion mode according to a relationship between a DC input voltage and a DC output voltage, the conversion mode being one of a buck mode, a boost mode and a buck-boost mode;
- controlling connections of the first capacitor and the inductor and their charging and discharging processes according to the selected conversion mode, so as to obtain a corresponding DC output voltage,
- wherein in switching cycles of the buck mode, the input terminal is coupled with the first node and the first capacitor remains coupled between an input terminal and ground,
- in switching cycles of the boost mode, a first end of the first capacitor remains coupled to the inductor, and a second end of the first capacitor switches between the input terminal and ground,
- in switching cycles of the buck-boost mode, a first end of the first capacitor switches between the input terminal and the inductor, and a second end of the first capacitor switches between the input terminal and ground,
- wherein the first capacitor switches between charging and discharging states according to a first control signal, the inductor switches between charging and discharging states according to a second control signal, and the first control signal and the second control signal have the same switching period,
- wherein the DC output voltage of the buck-boost converter in a steady state in continuous switching cycles is as follows:
- Vout=2*D1*Vin+D2*Vin,
- where Vout represents an output voltage, Vin represents an input voltage, D1 represents a duty cycle of the first control signal, and D2 represents a duty cycle of the second control signal.
Dependencies are inferred from the claim text.