Motor Current Control Using Component Temperature Estimation
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Solution Overview
Problem
Existing current control systems excessively limit drive current due to setting threshold values based on the component with the largest temperature rise, leading to early and unnecessary current restrictions.
Innovation Solution
A current control apparatus that includes a temperature detection circuit, current detection unit, component temperature estimation, and a reduction coefficient setting unit to dynamically adjust current limits based on the temperature and power loss of individual electronic components, using low-pass filters to estimate component temperatures and set appropriate reduction coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a plurality of switches are connected in parallel between the phase line and the neutral line to increase current capacity, then the current handling capability is improved, but the power loss increases due to increased ON-resistance
Solution Approach 1:
The patent divides the single switch into multiple switches (first switch and second switch) that are connected in parallel between the phase line and neutral line. Each switch handles a portion of the total current, allowing the system to achieve higher current capacity while managing power loss through individual control of each switch's resistance characteristics.
2Loss of energy
If the ON-resistance of switches is reduced to decrease power loss, then the energy efficiency is improved, but the current handling capability is reduced
Solution Approach 1:
Instead of using a single switch with low resistance, the patent uses multiple switches in parallel where each switch can have higher individual resistance. The combined parallel configuration achieves both low equivalent resistance (for low power loss) and high current handling capability, as current distributes across multiple paths.
Solution Approach 2:
The control device dynamically adjusts the ON-resistance of each switch based on the magnitude of current flowing through it. When current is small, resistance is kept low for efficiency; when current is large, the system activates additional switches in parallel to maintain low equivalent resistance and prevent overheating.
3Reliability
If the current magnitude is reduced to prevent saturation of the reactive element, then the reliability is improved, but the output performance is reduced
Solution Approach 1:
The control device dynamically changes the ON-resistance of switches based on real-time current magnitude detection. When the reactive element approaches saturation, the system adjusts switch resistance to limit current further, preventing saturation while maintaining optimal output performance under normal operating conditions.
Solution Approach 2:
The system implements feedback control by monitoring the current magnitude and adjusting the ON-resistance of switches accordingly. This feedback mechanism prevents the reactive element from saturating by reducing current when necessary, while allowing maximum output performance when the system operates within safe limits.
Data Source
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AI summary
The current control apparatus includes a component temperature estimating unit (61a1 and 61g) configured to estimate component temperatures, which are temperatures of an electronic components, for each of a plurality of the electronic components based on a current value flowing to each of the plurality of electronic components included in a current control circuit and a detected temperature detected by a temperature detecting element disposed in the vicinity of the current control circuit, and limits output current outputted from the current control circuit to a load based on the estimated component temperature. The component temperature estimating unit (61a1) estimates power loss of the electronic component and estimates the component temperature based on a sum of a first value obtained by filtering the power loss through a plurality of first low-pass filters (74a, 74b, 74c) connected in parallel with each other or connected in series with each other and a second value obtained by filtering the detected temperature detected by a temperature detection circuit through a second low-pass filter.