Capacitive Charger Circuit Scaling Current via Reverse Blocking Switch
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Solution Overview
Problem
Existing charger circuits face limitations in scaling up charging current using standard cables, such as USB cables, which restrict charging speed due to maximum current constraints, and require specialized fast charging cables that are inconvenient and difficult to optimize for power conversion efficiency.
Innovation Solution
A charger circuit incorporating a capacitive power conversion circuit with a conversion switch circuit and a reverse blocking switch circuit that allows for increased charging current by using a standard cable, blocking parasitic body currents and optimizing power conversion efficiency without the need for an inductor, thereby enabling faster charging with standard USB cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a standard USB cable is used for charging, then cable compatibility and flexibility are maintained, but the maximum charging current is limited to 5A or lower, resulting in longer charging time
Solution Approach 1:
The charging system is segmented into multiple functional blocks: a power delivery unit for voltage conversion, a capacitive power conversion circuit with multiple conversion capacitors for current scaling, and a control circuit for coordinated operation. This segmentation allows each component to be optimized independently, enabling the system to achieve high current output while maintaining standard cable compatibility.
Solution Approach 2:
The system dynamically changes electrical parameters by using multiple conversion capacitors with different capacitance values and switching them in different configurations. By adjusting the capacitance ratio and switching patterns, the system can scale the charging current by different factors (e.g., 2x, 3x, 4x) while maintaining compatibility with standard 5V USB power delivery, effectively transforming the limited 5A input into higher output currents without requiring specialized cables.
2Productivity
If a specially-designed fast charging cable with larger diameter is used, then charging current can be raised to 8A or higher, but the cable becomes less flexible and more inconvenient to use
Solution Approach 1:
The capacitive power conversion circuit acts as an intermediary device between the standard USB power source and the battery. Instead of relying on the cable to handle high currents directly, the circuit uses capacitive energy transfer to scale up the current from the standard 5A USB power delivery to higher levels (8A or more) at the output, while the cable itself continues to operate within its rated current capacity, maintaining flexibility and compatibility.
3Power
If a switching conversion circuit with inductor is used to convert power, then power conversion can be achieved, but it is very difficult to optimize the specifications of inductor and switches to maximize power conversion efficiency
Solution Approach 1:
The patent replaces the traditional inductor-based magnetic energy storage mechanism with a capacitor-based electric field energy storage mechanism. This substitution eliminates the need for bulky inductors and their associated optimization challenges regarding core materials, winding configurations, and magnetic saturation. The capacitive approach uses standard ceramic or film capacitors that are easier to select and optimize, simplifying the overall design while maintaining efficient power conversion capability.
4Power
If conversion switches with body diode are used in the charging path, then power conversion function is achieved, but parasitic body current flows through the body diode causing reverse current
Solution Approach 1:
The patent acknowledges the inherent body diode in MOSFET switches but converts this potentially harmful element into a useful feature. By carefully designing the switching sequence and control logic, the body diode's natural reverse recovery characteristics are utilized to prevent reverse current flow during certain switching transitions. The control circuit coordinates the switching of multiple capacitors and switches to ensure that body diodes conduct only in desired directions, transforming what would normally be a source of reverse current into part of the legitimate current path.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for scalable charging current without the need for specialized cables, optimizing power conversion efficiency and preventing reverse currents, thus reducing charging time while maintaining compatibility with standard USB cables.
Implementation Method 1
the conversion switch control signal operates the plural conversion switches so as to electrically connect the conversion capacitor between a pair of nodes selected from one or more charging voltage division nodes, the DC voltage, and a ground node periodically
Implementation Method 2
the reverse blocking switch circuit includes at least one reverse blocking switch which has a body diode, and the body diode of the reverse blocking switch is reversely coupled to said body diode of the conversion switch
Data Source
AI summary
A charger circuit for providing a charging current and voltage to a battery includes a power delivery unit, a capacitive power conversion circuit and a reverse blocking switch circuit. The power delivery unit converts an input power to a DC voltage and current. The capacitive power conversion circuit includes a conversion switch circuit including plural conversion switches coupled with one or more conversion capacitors, and a conversion control circuit. The DC current is regulated to a predetermined DC current level, and the conversion control circuit controls the connections of the plural conversion capacitors such that the charging current is scaled-up of the predetermined DC current level substantially by a current scale-up factor. The reverse blocking switch circuit is coupled in series with the capacitive power conversion circuit. The body diode of the reverse blocking switch is reversely coupled to the body diode of the conversion switch.