Universal-Voltage Discrete Input Circuit Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing discrete voltage input circuits are limited to specific narrow voltage ranges, are inaccurate and unreliable over temperature variations, and require different configurations or reconfiguration methods to handle varying voltage levels, leading to increased current draw and potential component malfunction.
Innovation Solution
A universal-voltage discrete input circuit utilizing a depletion-mode field effect transistor (FET) with an adjustable shunt regulator and resistor network to maintain a constant current over a wide range of input voltages, coupled with an isolation circuit to ensure stable operation across varying temperatures and voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a zener diode and current limiting resistors are used to limit voltage and current in a discrete input circuit, then the circuit can protect the digital logic input, but the circuit is limited to a narrow voltage range and draws excessive current at higher voltages
Solution Approach 1:
The patent changes the operating parameters of the FET by using a depletion-mode device that operates in its ohmic region, allowing the circuit to maintain constant current over a wide voltage range. The FET's drain-source resistance is controlled by gate voltage to compensate for input voltage variations, enabling the circuit to handle voltages from 5V to over 100V while maintaining stable current draw.
Solution Approach 2:
The patent introduces a high-voltage FET as an intermediary component between the input voltage source and the low-voltage digital logic circuit. The FET acts as a voltage-dependent resistor that automatically adjusts its resistance to maintain constant current, eliminating the need for zener diodes and multiple current limiting resistors while protecting the downstream circuit.
2Adaptability or versatility
If different circuit configurations or reconfiguration methods are used to handle different voltage levels, then the circuit can adapt to various voltage requirements, but the device complexity increases
Solution Approach 1:
The patent creates a universal input circuit design using a depletion-mode FET that can handle multiple voltage levels (5V, 12V, 24V, 48V, and higher) with a single fixed configuration. The FET's inherent characteristics allow it to automatically adapt to different input voltages without requiring changes to the circuit topology, component values, or additional configuration elements.
Solution Approach 2:
The depletion-mode FET automatically adjusts its own drain-source resistance based on the applied gate voltage, which is derived from the input voltage itself. This self-regulating behavior allows the circuit to adapt to different voltage levels without external control or reconfiguration, as the FET serves itself by using the input signal to control its own operating point.
3Adaptability or versatility
If higher input voltages are applied to increase the voltage handling capability, then the circuit can accept higher voltages, but the power dissipation and component stress increase significantly
Solution Approach 1:
The patent implements implicit feedback through the FET's gate control mechanism. The gate voltage, derived from the input voltage through a voltage divider network, automatically adjusts the FET's channel resistance in response to changes in drain-source voltage. This feedback mechanism ensures that power dissipation remains constant across the entire voltage range by dynamically adjusting the FET's operating point.
Solution Approach 2:
The patent transitions from static resistance components (fixed resistors and zener diodes) to a dynamic device (FET) whose resistance automatically adjusts with operating conditions. The FET's drain-source resistance changes dynamically in response to input voltage variations, allowing the circuit to maintain constant power dissipation and current draw regardless of the applied voltage level.
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 solution allows for a wide range of input voltages to be handled without increasing current draw, providing stable thermal characteristics and reliable operation across the desired temperature and voltage range, reducing the need for multiple circuit configurations and minimizing component stress.
Implementation Method 1
a depletion-mode field effect transistor (FET) having a drain, gate and source, wherein the drain thereof is adapted for coupling to the voltage source
Implementation Method 2
an adjustable shunt regulator having an anode, cathode and reference input
Implementation Method 3
an isolation circuit having an isolated input and an isolated output; wherein the isolated input of the isolation circuit is coupled between the source of the depletion-mode FET and the resistor network
Data Source
AI summary
A universal-voltage discrete input circuit uses a high voltage depletion-mode field effect transistor in combination with a low-voltage, adjustable precision shunt regulator and an isolation circuit for interfacing a low voltage digital logic circuit to a switched external voltage ranging from about 7 volts to about 1000 volts AC or +/â DC, at a low fixed current. In addition to the wide input voltage range accepted at a uniform low current value, very high voltage isolation is provided between the external voltage and the low voltage digital logic circuit, and elimination of ground loops and common mode noise.