Parallel LLC Converter Current Balancing Without Output Sensing
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Solution Overview
Problem
Existing LLC converters for DC to DC voltage conversion in parallel arrangements face challenges such as significant power losses during output current measurement, limited flexibility in system design, and complex reconfiguration requirements for replacing or adjusting the number of converters.
Innovation Solution
A LLC voltage converter design that includes a transformer with a current sensor to measure primary current, a controller to determine output current parameters, and the ability to communicate and balance output currents with other parallel converters, thereby reducing the need for direct measurement of output currents and enhancing system flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct measurement of output current is performed in step-down applications, then output current can be determined, but significant power losses occur due to high output current
Solution Approach 1:
The patent uses an intermediary approach by measuring the primary current through the transformer's first winding instead of directly measuring the high output current. The controller determines output current parameters based on the measured primary current and transformer characteristics, thereby avoiding direct measurement of high output current and reducing power losses
Solution Approach 2:
The patent replaces direct electrical current measurement with an indirect measurement system that uses voltage sensing across a known impedance (transformer winding). This substitution allows current determination without placing a direct measurement path in the high-current circuit, reducing power losses
2Ease of operation
If a master controller or master/slave arrangement is used to control parallel LLC converters, then current balancing between parallel converters can be achieved, but reconfiguration is required when replacing a converter
Solution Approach 1:
The patent implements self-service by enabling each LLC converter to autonomously determine its own output current parameters based on its measured primary current. Each converter independently controls its own operation without requiring master controller coordination or reconfiguration during replacement, as the converter simply continues to measure its primary current and adjust its operation accordingly
3Reliability
If the system is designed with a fixed number of parallel LLC converters, then the controller can be configured for that specific arrangement, but flexibility is limited when changing the number of converters
Solution Approach 1:
The patent applies dynamics by making the system adaptable to changing configurations. Each converter independently determines its operation based on real-time primary current measurements rather than relying on fixed master controller configuration. This allows the system to dynamically adjust when converters are added or removed, maintaining reliability while providing flexibility
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
This solution minimizes power losses by avoiding direct measurement of high output currents, allows for flexible system configuration without the need for extensive reconfiguration, and simplifies the process of replacing converters by eliminating the requirement for reconfiguring the master controller.
Implementation Method 1
a transformer comprising a first input winding and a second output winding
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A LLC voltage converter (1000') for converting a DC input voltage (1001) to a DC output voltage (1002). The LLC voltage converter (1000') includes a transformer (1201), a controller (1400) and a current sensor (1401). The current sensor (1401) provides a measurement of the current (1207) through a first winding of a transformer (1201) to the controller (1400). The controller (1400) determines a parameter relating to an output current (1004) of the LLC voltage (1000') converter using the current measurement. The controller (1400) also receives a parameter relating to an output current of at least one other LLC voltage converter, configured in parallel with the LLC voltage converter (1000'). The controller (1400) is arranged to control the LLC voltage converter (1000') based on both the parameter relating to the output current of the LLC converter (1000') and the parameter relating to the output current of the other LLC voltage converter.