Proportional Solenoid Valve Current Feedback for Ventilator Flow Control
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Solution Overview
Problem
Existing methods for controlling proportional solenoid valves in medical ventilation devices fail to compensate for systematic current drift due to coil heating, leading to inaccurate pressure and flow rate regulation.
Innovation Solution
An electronic control system adjusts the intensity of the electric current supplied to the solenoid valve coil using a DC/DC converter and feedback loop to maintain precise control of the orifice opening, compensating for temperature-induced resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If variable voltage or fixed voltage with current chopping is used to control the solenoid valve coil, then the degree of opening of the orifice can be varied proportionally, but the current intensity drifts systematically when the coil heats up due to Joule heating
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the actual current intensity through a shunt resistor and compares it with the reference current. When drift is detected due to coil heating, the system automatically adjusts the PWM duty cycle to compensate and maintain the desired current level, ensuring stable orifice opening control throughout operation
Solution Approach 2:
The system dynamically adjusts the PWM duty cycle parameter in response to changing coil resistance caused by temperature increase. By modifying this control parameter based on real-time current measurements, the system compensates for thermal effects and maintains consistent current delivery to the solenoid valve
2Manufacturing precision
If the coil current is increased to maintain orifice opening, then the desired pressure or flow rate can be achieved, but the coil resistance increases due to temperature rise
Solution Approach 1:
The feedback loop continuously monitors current through the shunt resistor and detects changes caused by temperature-induced resistance variations. The system compensates by adjusting the PWM duty cycle to maintain the reference current level, ensuring stable pressure and flow rate regulation without manual intervention
Solution Approach 2:
The control system automatically detects and compensates for its own thermal drift through the feedback mechanism. The electronic circuit self-regulates by comparing actual current with reference current and adjusting the PWM output accordingly, eliminating the need for external calibration or manual adjustment
3Adaptability or versatility
If pulse-width modulated rectangular signal is used for current chopping, then the current sent to the coil can be varied, but compensation for systematic drift is lacking
Solution Approach 1:
The system uses the shunt resistor to measure actual current intensity and feeds this information back to the control circuit. The feedback loop compares measured current with the reference current derived from the PWM signal, automatically adjusting the duty cycle to compensate for drift and maintain accurate current control throughout the operational range
Solution Approach 2:
The shunt resistor serves as an intermediary element that enables precise current measurement without significantly affecting the circuit operation. By placing this low-value resistor in series with the coil, the system can accurately monitor current intensity and use this information for feedback control, bridging the gap between PWM control and actual current delivery
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 approach ensures precise regulation of gas pressure and flow rate by compensating for coil heating, thereby improving the accuracy of ventilation device operation.
Implementation Method 1
comprising an electrically powered coil and electronic control means configured to control the degree of opening of the gas passage orifice by acting on the electrical current supplied to the coil
Implementation Method 2
the lack of compensation for the systematic drift of the set current (i.e. intensity) when the coil heats up due to Joule heating
Implementation Method 3
the electronic control means include an electronic circuit configured to adjust the intensity of the electric current supplied to the coil according to a pre-set voltage setpoint
Data Source
Figure 1~2
AI summary
The invention relates to a ventilation apparatus (1) comprising an internal gas circuit (2) for conveying a gas, and at least one proportional solenoid valve (4, 40, 400) with a gas passage orifice (4.1) having an adjustable degree of opening, arranged on the internal gas circuit and comprising an electrically powered coil (4.2). Electronic control means (5) control the degree of opening of the gas passage orifice of the proportional solenoid valve by acting on the electrical current supplied to the coil of the proportional solenoid valve so as to deliver a desired gas flow rate or pressure. The electronic control means comprise an electronic circuit (10) configured to adjust the intensity of the electrical current supplied to the coil according to a predetermined voltage setpoint (Vset).