Parallel Resonant Converter Current Balance Control
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Solution Overview
Problem
High power converter apparatuses with multiple resonant converters connected in parallel face challenges in achieving symmetrical current output due to inherent differences in circuit layouts, leading to inefficiencies and thermal losses.
Innovation Solution
A control module with voltage and current control loops is used to balance output currents across resonant converters by adjusting PWM control signals, including a time shift mechanism to reduce voltage ripple, ensuring equal current output and improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple resonant converters are connected in parallel to deliver high output current, then the reliability and maintenance capability are improved, but the current balance between converters deteriorates due to inherent circuit layout differences
Solution Approach 1:
The patent implements a control module with voltage sensing and current sensing that continuously monitors output parameters and adjusts PWM control signals accordingly. The voltage control loop compares sensed output voltage with reference voltage, and the current control loop compares sensed output currents between converters, creating closed-loop feedback that dynamically compensates for circuit layout differences and maintains current balance.
Solution Approach 2:
The patent dynamically adjusts the switching frequency of individual resonant converters based on their output current measurements. By generating frequency adjusting variables from current comparison results and applying them to modify PWM control signals, the system changes operational parameters to compensate for inherent differences between parallel converters, achieving current balance without requiring identical circuit layouts.
2Power
If multiple resonant converters are connected in parallel, then the high power output capability is improved, but the thermal loss increases due to current imbalance
Solution Approach 1:
The current control loop continuously monitors output currents from each converter and adjusts PWM control signals to equalize current distribution. By maintaining balanced current sharing through real-time feedback, the system prevents excessive current in individual converters, thereby reducing I²R thermal losses and improving overall efficiency while delivering high total output power.
3Power
If PWM control signals are applied to multiple resonant converters, then the output power is improved, but the voltage ripple increases
Solution Approach 1:
The patent introduces a time shift unit that applies different time shifts to PWM control signals for different converters. By periodically varying the timing of switching operations across parallel converters, the system creates phase-distributed switching patterns that cause voltage ripples to partially cancel each other out, reducing overall voltage ripple while maintaining high output power capability.
Data Source
AI summary
A resonant converter apparatus includes a plurality of resonant converters connected in parallel, and a control module outputting a pulse width modulation (PWM) control signal to the resonant converters. The control module includes a voltage control loop and a circuit control loop. The voltage control loop compares the sensed output voltage with a predetermined reference voltage, and outputs a PWM control signal to one of the resonant converters so the output voltage of the one converter is equal to the predetermined reference voltage. The current control loop uses the sensed output current of the one converter as a reference current, compares the reference current with the sensed output current from each of the other resonant converters, generates a frequency adjusting variable, and calculates the individual PWM control signal for each of the other converters so the output currents of the plurality of converters are the same.