Current-Sharing Circuit for Parallel DC-DC Converters
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Solution Overview
Problem
Standard DC-DC power converters lack integrated current-sharing and balancing circuits, leading to uneven current distribution among parallel converters, known as current hogging, where one converter supplies most of the current while others provide less, resulting in inefficient power delivery.
Innovation Solution
The integration of a current-sharing and balancing circuit within DC-DC power converters, utilizing a feedback loop with op amps, voltage dividers, and PWM to compare and adjust output voltages across multiple converters, ensuring even current distribution by generating an adjustment signal to modulate the power transistor's gate pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple DC-DC power converters are placed in parallel to supply high power currents, then the power delivery capacity is improved, but current distribution becomes uneven leading to current hogging
Solution Approach 1:
The patent implements a feedback mechanism where the output voltage of each parallel DC-DC converter is monitored and fed back to a control circuit. The control circuit compares these voltages and generates adjustment signals to modify the operating point of converters with higher output voltage, thereby balancing the current distribution among parallel converters and preventing current hogging while maintaining high power delivery capacity
Solution Approach 2:
The patent changes the operating parameters of parallel converters dynamically. By detecting output voltage differences and adjusting the duty cycle or switching frequency of PWM signals to the power transistors, the control circuit modifies the electrical parameters of individual converters to achieve balanced current sharing, transforming the system from static to adaptive parameter control
2Device complexity
If standard DC-DC power converters are used without integrated current-sharing circuits, then the device complexity is reduced, but current balancing capability is lost
Solution Approach 1:
The patent merges the current-sharing control functionality into the existing DC-DC converter structure. By integrating voltage sampling circuits, comparison circuits, and PWM adjustment mechanisms within the converter module itself, the system achieves current balancing without requiring separate external control systems, thus maintaining relative simplicity while adding essential current-sharing capability
Solution Approach 2:
The control circuit implemented in the patent serves multiple functions: it monitors output voltage, compares voltages among parallel converters, generates adjustment signals, and modifies switching duty cycles. This multi-functional control circuit is integrated into each converter module, allowing standard converters to gain current-sharing capability without requiring fundamentally different hardware architectures
Data Source
AI summary
Two or more power converters are connected in parallel to supply power current to a joining node through connecting resistors. An output voltage before the connecting resistor in each power converter is sampled and divided by a sampling ratio to generate sampled voltages for each power converter. A current sharing circuit for each power converter receives the local sampled voltage and another sampled voltage from another power converter. The current sharing circuit generates an adjustment voltage that is injected into a feedback loop. The adjustment voltage modifies the output voltage of the power converter, adjusting and balancing the power current delivered by that power converter. Power currents from several power converters are reduced and balanced when the same sampling ratio is used for all power converters. Current hogging by one power converter is prevented.