LLC DC-DC Converter Input Voltage Frequency Control
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Solution Overview
Problem
Existing solutions for controlling the input voltage of LLC DC-DC converters in electric vehicle chargers are complex, computationally expensive, and inadequate for wide variations in battery voltage, particularly between 250V and 430V, lacking a satisfactory method for reliable and efficient regulation.
Innovation Solution
A frequency-controlled method for LLC DC-DC converters with a 50% duty cycle, involving a preliminary step of defining a setpoint voltage, calculating control frequency, and applying it through a feedforward process with a discrete regulator to adjust frequency based on error thresholds, ensuring quick and robust voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If output voltage regulation using switching frequency control is applied, then the DCDC output voltage can be controlled, but the control system becomes complex and computationally expensive
Solution Approach 1:
The patent changes the control parameter from switching frequency to input voltage regulation. By controlling the input DC voltage of the LLC DC-DC converter rather than using complex frequency control, the system achieves effective voltage regulation while significantly reducing control system complexity and computational requirements
Solution Approach 2:
Instead of controlling the output voltage through complex frequency modulation of the DCDC converter, the patent inverts the approach by regulating the input DC voltage. This inverse control strategy simplifies the control architecture while maintaining effective voltage regulation performance
2Ease of manufacture
If the DC bus voltage is not regulated, then the charger can operate with simple control, but the input voltage to the DCDC converter varies widely causing inefficient operation
Solution Approach 1:
The patent applies preliminary action by regulating the input DC voltage before it enters the DCDC converter. By pre-controlling the voltage level at the converter input, the system ensures stable and efficient DCDC operation across varying battery voltage conditions, improving reliability without adding complex control to the DCDC stage itself
3Measurement precision
If frequency control is used to adjust DCDC converter gain, then the DC bus voltage can be controlled, but the control response is slow and not robust for wide battery voltage variations
Solution Approach 1:
The patent changes the controlled parameter from switching frequency to input voltage magnitude. By directly regulating the input DC voltage to the DCDC converter, the system achieves faster and more robust control response compared to frequency-based methods, particularly when dealing with wide battery voltage variations from 250V to 430V
Data Source
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AI summary
The invention relates to a method (4) for controlling the input voltage frequency of a DC-DC converter comprising: - a prior step of defining a setpoint voltage value (Vdc req); and - a step (40) of computing a control frequency value (f sw (ω)) of said DC-DC converter (12), as a function of the battery voltage (Vbat), a power setpoint (Preq) and said setpoint input voltage (Vdc req); and - a step of applying the control frequency to said converter.