Switching Capacitor Power Conversion Circuit Surge Current Protection
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Solution Overview
Problem
Conventional switching capacitor power conversion circuits face damage due to surge currents caused by voltage discrepancies between the conversion capacitor and output capacitor during switching operations, especially under heavy load conditions.
Innovation Solution
The proposed solution involves a switching capacitor power conversion circuit that pre-charges both the conversion capacitor and output capacitor before switching, using separate pre-charging periods to control the transistors and prevent excessive current flow, thereby reducing surge currents and supporting load operation with a smaller pre-charging current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching capacitor power conversion is performed when voltage across conversion capacitor and output capacitor are greatly different from steady-state voltages, then power conversion can be initiated, but surge current is generated that may damage conversion transistors
Solution Approach 1:
The patent applies preliminary action by implementing a pre-charging mode before the switching capacitor power conversion mode. During this pre-charging phase, the conversion capacitor and output capacitor are pre-charged to predetermined voltage levels, ensuring that when the actual power conversion begins, the voltage difference between capacitors is minimal, thus preventing surge currents that could damage transistors.
Solution Approach 2:
The patent applies preliminary anti-action by using current limiting circuits during the pre-charging phase to prevent excessive current flow. The circuit actively limits the pre-charging current to predetermined levels, counteracting the potential surge current that would otherwise occur when switching between capacitors with significantly different voltages, thereby protecting the conversion transistors from damage.
2Productivity
If pre-charging current is increased to support heavy load start-up, then load start-up capability is improved, but surge current risk increases
Solution Approach 1:
The patent applies dynamics by implementing dynamic current limiting that adapts to different operating conditions. The current limiting circuit dynamically adjusts the pre-charging current based on the charging stage and capacitor voltage levels, allowing sufficient current for heavy load start-up while preventing dangerous surge currents. The system transitions from a controlled pre-charging phase with limited current to a full power conversion mode.
Solution Approach 2:
The patent applies segmentation by dividing the power conversion process into distinct phases: a pre-charging phase with controlled current limits, and a subsequent switching capacitor power conversion phase. This segmentation allows the system to prepare capacitors safely in the first phase, then proceed to heavy load operation in the second phase without exposing the system to surge current risks throughout the entire operation.
3Device complexity
If conventional switching capacitor power conversion is used, then circuit structure is simple, but surge current damages conversion transistors
Solution Approach 1:
The patent applies merging by integrating the pre-charging function and current limiting protection directly into the switching capacitor power conversion circuit. Rather than adding completely separate protection circuits, the patent combines these functions with the existing conversion transistors and capacitors, using the same transistors for both pre-charging and power conversion operations. This approach maintains relative circuit simplicity while providing comprehensive surge current protection.
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
This approach effectively reduces the risk of damage from surge currents and enables reliable start-up under heavy loads by managing current levels during pre-charging, ensuring efficient power conversion while maintaining capacitor voltage balance.
Implementation Method 1
a conversion capacitor; a plurality of conversion transistors, which are coupled to the conversion capacitor CF
Implementation Method 2
provide a first pre-charging current to pre-charge the conversion capacitor CF to a predetermined voltage level; provide a second pre-charging current via the output node to pre-charge the output capacitor Cout
Data Source
AI summary
A switching capacitor power conversion circuit includes: a conversion capacitor, plural conversion transistors and an output capacitor connected to an output node. In a switching conversion mode, the switching capacitor power conversion circuit switches connections of the capacitor to convert the input power into an output power on an output node. During a first pre-charging period, a first conversion transistor is controlled to provide a first pre-charging current to pre-charge the conversion capacitor to a predetermined voltage level, and the output capacitor is prevented from being charged. During a second pre-charging period, a second conversion transistor is controlled to provide a second pre-charging current to pre-charge the output capacitor to the predetermined voltage level, and the second pre-charging current supplies a load current to a load circuit.