Master-Slave Current Sharing Control Circuit for Power Converters
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Solution Overview
Problem
Power supplies with master-slave current sharing relationships experience undesirable output fluctuations and continuous role reversal of power converters during dynamic load conditions due to differences in voltage-loop responses, leading to oscillations and instability.
Innovation Solution
A control circuit that detects dynamic load conditions and disables the current sharing correction function, transitioning the power converters from a default master-slave mode to a modified mode to prevent oscillation between output currents, using a proportional-integral (PI) controller to manage the transition and maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If power converters are controlled in a master-slave current sharing relationship with matching voltage-loop responses and increased current-share loop bandwidths, then current sharing precision is improved, but oscillation and instability occur during dynamic load conditions
Solution Approach 1:
The control system dynamically transitions between two different control modes based on operating conditions. During dynamic load conditions, the system switches to a modified master-slave mode with relaxed current sharing to prevent oscillation, while during steady-state conditions, it operates in the default mode with tight current sharing for precision. This dynamic adaptation resolves the contradiction by adjusting control parameters according to system state.
Solution Approach 2:
The system changes control parameters (current sharing correction function enabled/disabled) based on detected load conditions. By monitoring whether the system is in a dynamic or steady-state condition, the controller adjusts the degree of current sharing correction applied, thereby maintaining both precision and stability across different operating regimes.
2Measurement precision
If the current sharing correction function is continuously applied to maintain master-slave roles, then current sharing accuracy is improved, but output voltage creep-up and oscillation occur during dynamic transitions
Solution Approach 1:
The system detects dynamic load conditions in advance and preemptively disables the current sharing correction function before oscillation and voltage creep-up can occur. This preliminary anti-action prevents the harmful effects by removing the corrective control during transitions, allowing the system to settle smoothly before re-enabling precision control.
Solution Approach 2:
The current sharing correction function is applied periodically rather than continuously - it is enabled during steady-state conditions for accuracy and disabled during dynamic transitions to prevent oscillation. This periodic application of correction aligns control intensity with system needs, eliminating harmful effects while maintaining accuracy when required.
Data Source
AI summary
A control circuit is provided for controlling two power converters in a master-slave current sharing relationship. The control circuit is adapted to detect a presence of a dynamic load condition, control the two power converters in a default master-slave current sharing mode based on a current sharing correction function, and in response to detecting the presence of the dynamic load condition, disable the current sharing correction function so that the two power converters are controlled in a modified master-slave current sharing mode to substantially prevent oscillation between output currents of the two power converters. The control circuit may be one or more components of the power supply including the two power converters. Other example power supplies, control circuits and control methods are also disclosed.