Power Supply Current Control Device for EPS
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Solution Overview
Problem
Existing power supply current control systems face challenges in setting appropriate upper limit current values, often resulting in excessively small or large settings, leading to unstable power supply current and voltage, especially when the actual resistance of the power supply circuit differs from the modeled resistance.
Innovation Solution
A power supply current control device that includes a voltage detecting means, current detecting means, current limit value calculation unit, and power supply current limit unit, which calculates the current limit value based on the difference between the power supply voltage and a set voltage, as well as the detected power supply current and resistance model of the power supply circuit, and a change rate limit value calculation unit to stabilize the power supply current and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper limit current value is set solely on the basis of power supply voltage, then the power supply voltage can be maintained above a lower limit, but the upper limit current value becomes excessively small or excessively large leading to instability
Solution Approach 1:
The control device uses feedback control by detecting the power supply voltage and power supply current, calculating the deviation from set values, and adjusting the upper limit current value dynamically. The proportional component responds to current deviation while the differential component anticipates future trends, creating a stable feedback mechanism that prevents excessive limitation.
Solution Approach 2:
The system dynamically changes the upper limit current value parameter based on multiple inputs including power supply voltage deviation, power supply current magnitude, and resistance model. This parameter adaptation allows the system to maintain appropriate current limits under varying operating conditions without manual intervention.
2Reliability
If the upper limit current value is lowered in response to power supply voltage drop, then power supply voltage can be maintained, but the current limit value becomes excessively small causing instability
Solution Approach 1:
The system dynamically adjusts the upper limit current value parameter based on the actual operating conditions including power supply voltage, power supply current magnitude, and resistance model. This prevents excessive limitation by adapting the current limit to the specific situation rather than applying a fixed or overly aggressive reduction.
Solution Approach 2:
The feedback mechanism continuously monitors both power supply voltage and power supply current, and adjusts the upper limit current value accordingly. The proportional and differential components work together to respond to voltage deviations while considering the actual current flow, preventing unstable excessive limitation.
3Reliability
If the upper limit current value is set based on proportional and differential components of voltage deviation, then feedback control can maintain set voltage, but the current limit value may still be excessively small or large
Solution Approach 1:
The system extends parameter adaptation by incorporating not only voltage deviation but also power supply current magnitude and resistance model into the upper limit current value calculation. This multi-parameter adaptation enhances the system's versatility to handle various operating conditions appropriately.
Solution Approach 2:
The system makes the upper limit current value dynamic by continuously adjusting it based on real-time measurements of power supply voltage, power supply current, and resistance model. This dynamic adaptation allows the system to respond appropriately to changing conditions rather than relying on fixed proportional-differential control alone.
Data Source
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Figure 3~4
Figure 5A~5B
AI summary
To suppress, when limiting power supply current by an upper limit current value to mitigate power supply voltage drop, the upper limit current value from being set excessively small or excessively large. A power supply current control device including: a voltage detecting unit (35) configured to detect a power supply voltage applied from a power supply circuit; a current detecting unit (36) configured to detect a power supply current supplied from the power supply circuit; a current limit value calculation unit (41) configured to calculate a current limit value on a basis of a difference between the power supply voltage detected by the voltage detecting unit and a predetermined set voltage, the power supply current detected by the current detecting unit, and a resistance model representing a resistance component of the power supply circuit; a power supply current limit unit (42) configured to limit a magnitude of the power supply current on a basis of the current limit value; a change rate limit value calculation unit (43) configured to calculate a change rate limit value on a basis of the difference and a change speed of the power supply voltage; and a power supply current change rate limit unit (44) configured to limit a change rate of the power supply current on a basis of the change rate limit value.