Flying Capacitor Balancing in Standby Multilevel Converters
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Solution Overview
Problem
Existing multi-level power converters face challenges in balancing flying capacitor voltages during standby operations, which often require additional components like balancing resistors, increasing the bill of materials and causing constant losses.
Innovation Solution
A control mechanism for multi-level power converters that switches at least two of the four switching elements to balance flying capacitor voltages during standby operation without additional circuit elements, using a feedback loop to regulate the voltage based on a setpoint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external balancing resistors are used to balance flying capacitor voltage during standby operation, then the flying capacitor voltage is balanced, but additional components are required which increases the bill of materials and overall footprint
Solution Approach 1:
The power converter module uses its own existing switching elements and capacitors to balance the flying capacitor voltage during standby operation, without requiring external balancing resistors. The controller activates specific switching elements to create charge transfer paths that self-regulate the voltage balance
Solution Approach 2:
The existing switching elements and capacitors in the power converter module are made to serve dual functions: their primary power conversion function and an additional voltage balancing function during standby operation. This eliminates the need for dedicated balancing components
2Reliability
If external balancing resistors are used to balance flying capacitor voltage, then the flying capacitor voltage is balanced, but constant losses occur even in normal operation
Solution Approach 1:
The controller periodically activates specific switching elements during standby operation to transfer charge between capacitors, creating a pulsed balancing action rather than continuous resistive discharge. This periodic charge transfer occurs only when needed to maintain voltage balance
Solution Approach 2:
The system uses controlled charge transfer through switching elements rather than passive resistive discharge, allowing the power converter to self-regulate its capacitor voltages without continuous energy dissipation
3Reliability
If duty cycle variation is used to balance flying capacitor voltage during normal operation, then the voltage is balanced, but additional control effort is required
Solution Approach 1:
The controller dynamically selects which switching elements to activate based on the real-time voltage state of the capacitors. During standby operation, the controller monitors capacitor voltages and activates specific switching elements to transfer charge from overcharged to undercharged capacitors, adapting the balancing action to the current system state
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
Achieves balanced flying capacitor voltages during standby without additional components, reducing costs and losses by reusing existing hardware and minimizing footprint.
Implementation Method 1
a flying capacitor coupled between the first capacitor node and the second capacitor node
Implementation Method 2
alter a flying capacitor voltage across the flying capacitor by switching at least two of the four switching elements
Data Source
AI summary
A power converter module and a corresponding method is presented. The power converter module may comprise a first switching element coupled between a first terminal of the power converter module and a first capacitor node, a second switching element coupled between the first capacitor node and a switching node, a third switching element coupled between the switching node and a second capacitor node, and a fourth switching element coupled between the second capacitor node and a reference node. The power converter module may comprise a flying capacitor coupled between the first capacitor node and the second capacitor node. The power converter module may be configured to, in standby operation, alter a flying capacitor voltage across the flying capacitor by switching at least two of the four switching elements.