Boost Control Apparatus Zero Crossing Detection via Current Rate
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Solution Overview
Problem
Existing boost control apparatuses for electric vehicles face challenges in accurately detecting zero crossing, leading to inappropriate duty control and suboptimal output current, particularly in high-frequency states.
Innovation Solution
A boost control apparatus with a rate calculating device and control determining device that switches between first and second duty controls based on the change rate of the output current, determining zero crossing by calculating the change rate of the output current to the duty value, allowing for accurate duty control even if the output current cannot be accurately detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional zero crossing detection methods are used, then the control structure is simple, but the detection accuracy is insufficient especially in high-frequency states
Solution Approach 1:
The patent changes the detection parameter from direct current magnitude to the rate of change of current (di/dt). By detecting zero crossing through the rate of change parameter rather than the absolute current value, the system achieves accurate detection even in high-frequency states where conventional methods fail, without requiring complex additional hardware
Solution Approach 2:
The patent replaces the conventional mechanical/electrical detection method (monitoring current magnitude) with a mathematical differentiation approach (calculating rate of change). This substitution allows for more accurate zero crossing detection by using computational methods rather than direct physical measurement, resolving the accuracy issue in high-frequency operation
2Measurement precision
If duty control is not switched at zero crossing, then the control logic is simple, but the output current accuracy deteriorates
Solution Approach 1:
The patent introduces dynamic switching of duty control based on the detected zero crossing condition. The control system dynamically transitions between different duty control modes (first duty control before zero crossing, second duty control after zero crossing), allowing the output current accuracy to be maintained across different operating conditions while managing complexity through conditional logic
Solution Approach 2:
The patent implements feedback control by continuously monitoring the inductor current and its rate of change, detecting zero crossing events, and adjusting the duty control accordingly. This feedback mechanism ensures accurate output current by adapting the control strategy based on real-time system state, resolving the trade-off between accuracy and complexity
3Loss of energy
If one-side element control is implemented, then the converter loss is reduced, but the zero crossing detection becomes more difficult
Solution Approach 1:
The patent addresses the detection difficulty in one-side element control by changing the detection parameter to the rate of change of current (di/dt). This parameter change enables reliable zero crossing detection even when only one switching element is active, maintaining the low-loss benefit of one-side element control while solving the detection challenge it creates
Data Source
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AI summary
A boost control apparatus (30) is provided with: a controlling device (330) configured (i) to perform first duty control by using a first control parameter if output current (IL) that flows through an inductor (L1) is not near zero, and (ii) to perform second duty control by using a second control parameter if the output current is near zero, during one-side element control during which only either one of a first switching element (Q1) and a second switching element (Q2) is driven; a rate calculating device (310) configured to calculate a change rate of the output current to a change amount of a duty value in the first duty control and the second duty control; and a control determining device (320) configured to control said controlling device to perform the second duty control regardless of the output current, if the change rate is less than a predetermined value.