Power Converter Rate-of-Change Control for Voltage Stability
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Solution Overview
Problem
Conventional power conversion apparatuses face issues with audible noise due to switching frequencies in the audible frequency band, response lag leading to high-voltage requirements, and inaccurate control of output voltage, especially during load changes, which increases manufacturing costs.
Innovation Solution
A power conversion apparatus with a switch circuit, feedback section, and operation determining unit that monitors the rate of change of the output value to accurately control the operation of switching elements, minimizing the need for high-voltage components and ensuring precise output voltage control by determining operation stop and start based on rate of change and controlled variables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional feedback control is used without rate of change monitoring, then the control structure is simple, but response lag occurs when load current drastically decreases causing output voltage to increase excessively
Solution Approach 1:
The operation stop determination section monitors the rate of change of output voltage in advance before excessive voltage increase occurs. When the rate of change exceeds a predetermined threshold, the control section preemptively stops switching element operation, preventing the output voltage from rising to dangerous levels and eliminating the need for high-voltage components.
2Ease of manufacture
If two thresholds are used for controlling switching element operation, then the control logic is simple, but the average output voltage value deviates from the instructed value reducing control accuracy
Solution Approach 1:
The patent dynamically adjusts the threshold for operation stop determination based on the instructed output voltage value. The threshold is set as a proportional relationship to the instructed voltage, allowing the control system to maintain high accuracy across different operating points while keeping the control logic relatively simple.
3Reliability
If high-voltage parts are provided on the output side to withstand voltage increases, then output voltage control stability is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts and removes the need for high-voltage components from the output side by implementing rate of change monitoring and preemptive control. The control section stops switching element operation before output voltage can increase to levels that would require high-voltage parts, thereby reducing manufacturing cost while maintaining voltage control stability.
4Object-affected harmful factors
If switching frequencies are controlled to avoid audible frequency band, then audible noise is reduced, but control complexity increases
Solution Approach 1:
The patent implements periodic burst mode operation where switching elements are turned on and off in predetermined cycles. By controlling the duty ratio and burst period, the switching frequencies are kept outside the audible frequency band, reducing audible noise while maintaining relatively simple control logic based on standard pulse width modulation techniques.
Data Source
AI summary
A power conversion apparatus includes a switch circuit which drives switching elements based on a control signal, a feedback section which performs feedback control, a signal output section which outputs the control signal based on a controlled variable of the feedback control, an output value detecting section which detects an output value outputted from the switch circuit, and an operation determining unit which has an operation stop determination section which determines whether to stop operation of the switching elements based on a rate of change of the output value, and an operation start determination section which determines whether to start operation of the switching elements based on the controlled variable.