Multi-path Constant Current Driving Circuit with Current Balancing
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Solution Overview
Problem
Current constant-current control circuits for multipath LEDs suffer from poor current balancing and high costs due to complex and inefficient non-isolated DC/DC constant-current modules, as well as large size and cost of current-balancing transformers caused by unidirectional DC currents.
Innovation Solution
A multipath constant-current driving circuit with a DC/AC converter, a main transformer, and current-balancing transformers arranged between power supply loops, where currents flow in the same direction through the windings of the current-balancing transformers, eliminating DC currents and allowing for efficient current balancing without the need for air gaps, thus reducing transformer size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-isolated DC/DC constant-current modules are used for multipath LED control, then constant-current control is achieved, but the structure becomes complex and costly
Solution Approach 1:
The patent merges multiple DC/DC constant-current modules into a single isolated DC/DC module with multiple secondary windings. This unified structure provides constant-current control for multiple LED paths simultaneously, eliminating the need for separate modules and reducing overall system complexity while maintaining reliable constant-current control.
Solution Approach 2:
The isolated DC/DC module is designed with multi-functionality to serve multiple LED paths. The single module incorporates multiple secondary windings that can independently provide constant-current control to different LED strings, making one module perform the function of what would traditionally require multiple separate modules.
2Reliability
If non-isolated DC/DC constant-current modules are used, then constant-current control is provided, but conversion efficiency is low due to voltage disparity
Solution Approach 1:
The patent employs parameter changes by providing adjustable turns ratios for the secondary windings of the isolated DC/DC module. This allows the output voltage to be matched to the specific LED path requirements, optimizing the voltage transition and improving conversion efficiency while maintaining reliable constant-current control.
3Reliability
If coupled inductor with unidirectional DC current is used for current balancing, then current balancing is attempted, but magnetic core saturation occurs requiring air gaps
Solution Approach 1:
The patent inverts the conventional approach by using bidirectional AC current instead of unidirectional DC current in the coupled inductor. This reversal prevents magnetic core saturation because AC current alternates direction, preventing the accumulation of DC bias that would cause saturation. Consequently, air gaps are unnecessary, reducing transformer size.
4Reliability
If air gaps are created in coupled inductor to prevent saturation, then saturation is avoided, but transformer size and cost increase
Solution Approach 1:
The patent converts the potential harm of magnetic core saturation into a benefit by using AC current that naturally prevents saturation through its bidirectional nature. The alternating current ensures the magnetic flux oscillates around zero, converting what would be a problematic DC bias condition into a beneficial saturation-free operation without requiring physical modifications like air gaps.
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
The circuit achieves good current balancing even with large voltage differences across loads, enabling smaller and less costly current-balancing transformers, thereby lowering overall system costs and improving efficiency.
Implementation Method 1
a DC/AC converter (1101), a main transformer (1102)... the DC/AC converter (1101) is adapted to provide an alternating current (AC) voltage for a primary winding of the main transformer (1102)
Implementation Method 2
a main transformer (1102)... each of the at least two rectification and filtering units (1103) forms a power supply loop with a secondary winding of the main transformer (1102)
Implementation Method 3
each of the at least two rectification and filtering units (1103)... performs rectification and filtering
Implementation Method 4
a current-balancing transformer (1104) is arranged between power supply loops where adjacent rectification and filtering units (1103) are in... the current-balancing transformer (1104) is for current balancing between the power supply loops
Data Source
AI summary
A multi-path constant current driving circuit. In the multi-path constant current driving circuit, a current sharing transformer (T31, T32, T33, T3(n−1)) is provided in power supply circuits which are provided with adjacent rectifier and filter units (Z31, Z32, Z33, Z3n). A first winding of the current sharing transformer (T31, T32, T33, T3(n−1)) is connected between a first terminal of a secondary winding of a first power supply circuit and the rectifier and filter unit (Z31, Z32, Z33, Z3n) of the first power supply circuit. A second winding of the current sharing transformer (T31, T32, T33, T3(n−1)) is connected between a first terminal of a secondary winding of a second power supply circuit and the rectifier and filter unit (Z31, Z32, Z33, Z3n) of the second power supply circuit. In-phase current flows through the dotted terminal of the first winding and the synonym terminal of the second winding of the current sharing transformer (T31, T32, T33, T3(n−1)). The current sharing transformer (T31, T32, T33, T3(n−1)) is used for sharing the current between the power supply circuits which are provided with the adjacent rectifier and filter units (Z31, Z32, Z33, Z3n ). The driving circuit is provided with high current sharing efficiency, a small size and a low cost.