Pulse Width Modulated Defroster for Plastic Windows
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Solution Overview
Problem
Plastic windows in vehicles face challenges with lower electrical and thermal conductivity compared to glass, leading to inefficient defrosting systems that often result in overheating and potential damage when using standard battery voltages, necessitating high-wattage resistors to step down voltage and manage excessive heat.
Innovation Solution
A system comprising a heater grid and a controller with a pulse width modulator that provides an initial overdriving voltage followed by a pulsed signal to efficiently heat the grid, optimizing energy use and preventing overheating by maintaining an effective voltage within the optimal operating range of the heater grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If standard battery voltage is applied to the heater grid, then the defrosting speed is improved, but the heater grid overheats and may cause damage to the plastic panel
Solution Approach 1:
The patent applies periodic pulsed voltage to the heater grid instead of continuous standard battery voltage. The controller delivers voltage in controlled pulses with specific duty cycles, allowing the heater to reach effective defrosting temperatures while preventing sustained overheating that would damage the plastic panel or grid.
Solution Approach 2:
The patent dynamically adjusts the voltage delivery parameters including pulse width, duty cycle, and timing based on the defrosting requirements. The controller modulates the voltage dynamically rather than applying a fixed standard battery voltage, enabling optimal balance between defrosting speed and temperature control.
2Reliability
If voltage is stepped down using a high-wattage resistor, then the heater grid operates at optimal voltage, but the resistor dissipates excessive power and generates heat that must be managed
Solution Approach 1:
The patent replaces the passive resistive voltage dropping mechanism with an active electronic control system using pulse width modulation. Instead of using a high-wattage resistor to continuously dissipate power, the controller electronically switches the voltage on and off in pulses, achieving effective voltage reduction without continuous power loss in a resistor.
Solution Approach 2:
The patent changes the temporal parameters of voltage delivery through pulse width modulation. By varying the duty cycle and pulse duration, the controller effectively reduces the average voltage to optimal levels without requiring power-dissipating resistive elements, thereby minimizing energy loss.
3Area of stationary object
If long grid lines are used on plastic panels, then the heater grid coverage is improved, but the lower thermal conductivity of plastic reduces heating efficiency
Solution Approach 1:
The patent uses periodic pulsed voltage delivery to compensate for the lower thermal conductivity of plastic panels. The pulsed heating pattern allows heat to accumulate and distribute through the long grid lines more effectively than continuous low-power operation, maintaining heating efficiency across extended areas.
Solution Approach 2:
The controller applies preliminary high-voltage pulses to quickly raise the temperature of the heater grid elements before transitioning to maintenance pulsing. This preliminary heating action overcomes the thermal lag inherent in long grid lines on low-conductivity plastic substrates, ensuring efficient heat distribution across the entire covered area.
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 solution effectively defrosts plastic windows by efficiently managing heat energy, reducing the risk of overheating and damage, while minimizing power handling requirements for the defroster circuit and managing heat generated by resistors.
Implementation Method 1
The driving signal provides a voltage across the heater grid causing the heater grid to emit heat energy
Implementation Method 2
The pulsed portion provides a pulsed signal with a pulsed high voltage greater than the optimal operating voltage. However, the pulsed portion provides the heater grid with an effective voltage substantially equal to the optimal operating voltage of the heater grid due to the duty cycle of the pulsed portion
Data Source
AI summary
A window defroster system that includes a heater grid and a controller. The controller includes a pulse width modulator configured to provide a driving signal to the heater grid. The driving signal has an initial heating portion and a pulsed portion. The initial heating portion provides an initial voltage that is greater than an optimal operating voltage of the heater grid, the pulsed portion provides a pulsed signal with a pulsed high voltage that is greater than the optimal operating voltage.