PWM Coil Drive Circuit for Stable Inrush and Latching Current
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Solution Overview
Problem
Existing coil driving devices struggle to supply predetermined inrush and latching currents across a wide voltage range while maintaining reliability and stability, particularly under temperature changes, and require additional components like current sensors and feedback circuits.
Innovation Solution
A coil driving device with an input voltage sensing unit, switch unit, PWM circuit, impedance adjustment unit, and control unit that adjusts impedance and PWM signal parameters based on input voltage to stabilize inrush and latching currents, eliminating the need for current sensors and feedback circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PWM control with current sensor and feedback circuit is used to maintain constant coil current, then operating characteristics are maintained constantly, but device complexity increases due to additional components
Solution Approach 1:
The patent extracts and removes the current sensor and feedback circuit from the PWM control system. Instead of using active sensing and feedback components, the invention uses a simple impedance adjustment unit that directly modifies the PWM signal based on detected voltage levels, achieving current control without the complex sensing and feedback infrastructure.
Solution Approach 2:
The patent replaces the electronic feedback control mechanism with a voltage-based impedance adjustment mechanism. The control unit detects input voltage and directly adjusts PWM duty ratio or frequency through impedance control, substituting the mechanical/electronic feedback loop with a simpler voltage-responsive control system.
2Force
If high inrush current is supplied to drive the coil initially, then the moving core is actuated effectively, but coil temperature increases and lifespan decreases
Solution Approach 1:
The patent applies periodic PWM control to the coil, delivering current in controlled pulses rather than continuous high current. The PWM signal provides the necessary inrush current peaks for actuation while allowing cooling intervals between pulses, preventing excessive temperature buildup while maintaining effective magnetic force generation.
Solution Approach 2:
The patent uses dynamic adjustment of PWM duty ratio and frequency based on detected input voltage levels. The control unit modifies the PWM parameters in real-time to optimize the balance between delivering sufficient inrush current for actuation and limiting average current to prevent overheating, adapting the current profile to operational requirements.
3Power
If PWM circuit operates at maximum duty ratio to supply sufficient current at low voltage, then inrush current requirement is met, but power consumption and heat generation increase
Solution Approach 1:
The patent changes the PWM signal parameters (duty ratio and frequency) dynamically based on the detected input voltage level. Instead of operating continuously at maximum duty ratio, the control unit adjusts PWM parameters to match the actual voltage conditions, ensuring sufficient driving current is delivered while minimizing unnecessary power consumption and heat generation.
4Power
If impedance adjustment unit modifies PWM signal to limit driving current, then current control is improved, but device complexity increases
Solution Approach 1:
The patent merges the impedance adjustment function directly into the PWM control circuitry. The impedance adjustment unit is integrated with the control unit, allowing current control to be achieved through unified voltage detection and PWM parameter adjustment without adding separate complex control stages or components.
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
The device provides stable inrush and latching currents across a wide voltage range, reduces coil stress, extends lifespan, and minimizes heat generation, all while simplifying the design and reducing component count.
Implementation Method 1
an internal coil acts as an actuator, and when a current flows at the coil, a switch operates to conduct electricity... uses the principle of an electromagnet... a magnetic force is generated by the fixed core
Data Source
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AI summary
The present invention provides a coil driving device comprising: an input voltage sensing unit for sensing an input voltage; a switch unit configured to make a switching operation to supply a driving current to a coil; a PWM circuit unit for outputting a pulse width modulation (PWM) signal for the switching operation of the switch unit; an impedance adjustment unit for varying an impedance value such that the PWM signal is adjusted, thereby limiting the driving current; and a control unit for causing the impedance adjustment unit to vary the impedance value on the basis of the input voltage, thereby adjusting at least one of the duty ratio of the PWM signal and the frequency thereof.