PWM Solenoid Current Detection Despite Amplifier Delay
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric current detection apparatuses using inexpensive amplifiers with low slew rates face challenges in accurately measuring electric current values due to long delay times, especially when detecting current changes corresponding to signal rises and falls in PWM-controlled solenoids.
Innovation Solution
An electric current detection apparatus that includes a switch controlled by PWM, an electric current value detection portion to measure first and third electric current values at specific timings, and a second electric current value calculation portion to calculate the electric current value at the second timing, using a resistor and amplifier to minimize the impact of delay times, with the first time period set to be longer than the amplifier's response delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an inexpensive amplifier with low slew rate is used, then cost is reduced, but measurement precision deteriorates due to long delay time
Solution Approach 1:
The patent applies preliminary action by detecting the electric current value at a timing before the PWM signal transitions (when the switch is still in the same state) and then calculating the current value at the transition timing based on this preliminary detection. This allows the system to use an inexpensive amplifier with delay characteristics while still obtaining accurate current values at critical transition moments, resolving the contradiction between cost reduction and measurement precision.
2Speed
If the electric current value is detected with a trigger corresponding to signal rise and fall, then response speed is improved, but measurement precision deteriorates due to amplifier delay
Solution Approach 1:
The system performs current detection at a timing preceding the PWM transition (when the switch state has already been established) and then calculates the current value at the actual transition timing. This preliminary detection approach maintains fast response to signal transitions while avoiding the delay problem that would occur if detection were triggered exactly at the transition moment, thus resolving the contradiction between response speed and measurement precision.
3Measurement precision
If the first time period is set longer than the amplifier response delay, then measurement precision is improved, but productivity deteriorates due to increased measurement time
Solution Approach 1:
The patent sets the first time period longer than the amplifier response delay to ensure the detected current value stabilizes, improving measurement precision. However, it compensates for the increased measurement time by using calculation based on preliminary detection values rather than waiting for direct detection at transition moments. This approach maintains productivity while achieving precise measurements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for accurate detection of electric current values at each timing, reducing processing load and maintaining detection accuracy even with inexpensive amplifiers, thereby contributing to cost reduction and improved control of PWM-controlled solenoids.
Implementation Method 1
many of such inexpensive amplifiers include a low slew rate. At the amplifier including a low slew rate, a delay time of an output signal relative to an input signal is long
Data Source
AI summary
An electric current detection apparatus, the electric current detection apparatus is configured to detect an electric current flowing in a solenoid configured to be electrified by a PWM control, the apparatus includes a switch, an electric current value detection portion configured to detect a first electric current value at a first timing corresponding to a timing when the switch transitions from a closed state to an open state, the electric current value detection portion being configured to detect a third electric current value at a third timing, and a second electric current value calculation portion configured to calculate a second electric current value on the basis of the first electric current value and the third electric current value, the second electric current value being an electric current value of the electric current at the second timing.