Three-Level Buck Circuit With Flying Capacitor Voltage Balancing
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Solution Overview
Problem
Conventional three-level buck circuits suffer from flying capacitor voltage imbalance, leading to reduced efficiency and over-voltage damage due to inconsistencies in control and drive circuits, and require an inductor for voltage regulation, resulting in significant power losses.
Innovation Solution
Incorporating a first capacitor and a switching transistor to form a voltage balancer circuit, pre-charging the capacitor to 0.5*Vin, and connecting it in series or parallel with the flying capacitor at appropriate times to stabilize its voltage at 0.5*Vin, and implementing a charge pump mode by short-circuiting the inductor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional three-level buck circuit is used, then voltage step-down function is achieved, but flying capacitor voltage imbalance occurs leading to reduced efficiency and over-voltage damage
Solution Approach 1:
An auxiliary capacitor is introduced as an intermediary element to balance the flying capacitor voltage. The auxiliary capacitor connects to the flying capacitor through a switching network, enabling charge transfer and voltage equalization between them, thereby preventing voltage imbalance and improving reliability without significant energy loss
Solution Approach 2:
The circuit dynamically changes the connection configuration of the auxiliary capacitor relative to the flying capacitor. By controlling the switching states, the auxiliary capacitor can be connected in parallel with the flying capacitor to equalize voltages, or disconnected to allow normal operation, thus maintaining voltage stability while minimizing energy loss
2Power
If an inductor is used for voltage regulation, then voltage control is achieved, but significant power losses occur
Solution Approach 1:
The inductor is extracted or removed from the circuit topology. The patent implements a buck circuit that achieves voltage regulation without requiring an inductor by using a novel switching network with capacitors, thereby eliminating the power losses associated with inductor resistance while maintaining voltage control capability
Solution Approach 2:
The switching network performs multiple functions: it regulates output voltage, balances capacitor voltages, and eliminates the need for an inductor. This multi-functional approach achieves voltage control without the energy losses typical of inductor-based solutions
Data Source
AI summary
Embodiments of the present disclosure provide a buck circuit, and a device and a control method therefor. The buck circuit includes four power transistors, a flying capacitor, an inductor, a first capacitor, a first switching module, and a switching control module. The switching control module is configured to control the first switching module to turn on when controlling the first power transistor and the third power transistor to turn on such that the first capacitor and the flying capacitor are connected in series, and further configured to control the first switching module to turn on when controlling the second power transistor and the fourth power transistor to turn on such that the first capacitor and the flying capacitor are connected in parallel. The buck circuit according to the embodiments of the present disclosure improves efficiency and prevent over-voltage damage.