Multi-Level DC Converter Flying Capacitor Precharge Circuit
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Solution Overview
Problem
Existing multi-level direct current converters require additional charging components and complex circuits to precharge flying capacitors, leading to high costs and structural complexity.
Innovation Solution
A multi-level direct current converter is designed with a charging loop formed by configuring existing power transistors, eliminating the need for additional charging components and using a voltage management unit to control the precharging process, thereby simplifying the structure and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional charging components and feedback circuits are used to precharge the flying capacitor, then the precharging function is achieved, but the circuit structure becomes complex and costs increase
Solution Approach 1:
The power transistors Q1 and Q2 are made to serve dual functions: they act as switching elements for normal DC/DC conversion operation and simultaneously function as charging components for precharging the flying capacitor Cf during startup. This eliminates the need for separate dedicated charging components, thereby simplifying the circuit structure while maintaining the precharging function.
Solution Approach 2:
The circuit uses its own existing components (power transistors Q1 and Q2) to perform the precharging function without requiring external or additional charging circuits. The system essentially charges itself using resources already available within the converter, avoiding the need for separate charging infrastructure.
2Reliability
If additional charging components and detection circuits are used to precharge the flying capacitor, then the precharging control is achieved, but the circuit costs increase
Solution Approach 1:
The controller is made to perform multiple functions: it controls the switching of power transistors for normal operation and simultaneously manages the precharging process of the flying capacitor. By integrating these control functions into a single controller, the need for separate detection circuits and charging components is eliminated, reducing overall circuit costs.
Solution Approach 2:
The precharging control function is merged with the main switching control function in a single controller unit. The controller integrates both the detection of startup conditions and the control of charging current, combining what would traditionally be separate circuits into one unified control mechanism, thereby reducing component count and cost.
3Strength
If a flying capacitor is used to store half input voltage, then the voltage levels are reduced and component performance is improved, but the flying capacitor requires precharging which complicates the circuit
Solution Approach 1:
The power transistors are designed to serve dual purposes: they switch during normal multi-level conversion to enable the voltage-stress-reducing topology, and they simultaneously act as charging switches for the flying capacitor during startup. This eliminates the need for separate charging circuits while preserving the benefits of the multi-level topology.
Solution Approach 2:
The converter uses its own power transistors and existing circuitry to precharge the flying capacitor, rather than requiring external or dedicated charging components. The system leverages resources already present in the circuit to perform the precharging function, avoiding additional complexity.
Data Source
AI summary
A multi-level direct current converter includes a direct current conversion unit, a switching unit, a voltage management unit, and a controller. The direct current conversion unit includes a flying capacitor, a first power transistor, and a second power transistor. A first end of the first power transistor is connected to a voltage input end of the multi-level direct current converter, a second end of the first power transistor is connected to a first end of the second power transistor by using the flying capacitor, and a second end of the second power transistor is connected to a reference ground.