Wide-Range Input Circuit With Selectable Zener Thresholds
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Solution Overview
Problem
Existing input circuits for digital systems are limited in their ability to adapt to a wide range of voltage levels, particularly in industrial settings where sensors interface with digital control systems, as they can only implement a single fixed switching threshold for low-voltage signals, failing to provide flexibility in setting standards for different voltage ranges.
Innovation Solution
A wide-range input circuit featuring a series connection of an input-side rectifier, current controller, multiple reverse-biased zener diodes, and an optocoupler, with bridging devices controlled by a microprocessor to adjust switching thresholds dynamically, allowing for flexible and software-adjustable settings across various voltage ranges from ≤120 V to <1500 V.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single zener diode is used to set a switching threshold, then the circuit structure is simple, but only one fixed switching threshold can be implemented
Solution Approach 1:
The patent divides the voltage threshold setting function into multiple zener diodes connected in series, each providing a specific voltage contribution. By selectively bridging individual zener diodes through bypass circuits, the total threshold voltage can be segmented and reconfigured to achieve multiple discrete threshold levels (e.g., 5V, 10V, 15V, 20V) from a single circuit structure.
Solution Approach 2:
The patent transforms the fixed threshold circuit into a dynamic, adjustable system by introducing microprocessor-controlled bypass circuits. These bypass circuits can be activated or deactivated based on software commands, allowing the switching threshold to be dynamically changed without physical circuit modifications, thus achieving adaptability across different voltage ranges.
2Adaptability or versatility
If multiple zener diodes are used to provide multiple switching thresholds, then voltage range adaptability is improved, but the circuit structure becomes more complex
Solution Approach 1:
The patent designs a universal input circuit that can handle multiple voltage ranges (≤120V and <1500V) and both AC and DC signals through a single standardized structure. The same series-connected zener diode array serves multiple functions: setting thresholds for different voltage classes, working with both AC and DC inputs, and interfacing with digital systems through the optocoupler, eliminating the need for multiple dedicated circuits.
Solution Approach 2:
The patent introduces an optocoupler as an intermediary component between the high-voltage input side and the low-voltage digital output side. This optocoupler provides galvanic isolation, allowing the circuit to safely interface with high voltages up to 1500V while protecting the digital system, thus expanding the voltage range adaptability without proportionally increasing complexity.
3Ease of operation
If AC signals are directly processed without rectification, then the circuit is simpler, but DC current cannot be established for proper zener diode operation
Solution Approach 1:
The patent incorporates a rectifier circuit that enables the input stage to universally accept both AC and DC signals. The rectifier converts AC inputs into DC current, which then flows through the series-connected zener diodes to establish the switching threshold. This multi-functional input stage maintains relative simplicity while providing flexibility to operate with either AC or DC signal types.
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
Enables multiple switching thresholds to be implemented with ease, ensuring standard switching thresholds can be set quickly and parameterized for different applications, ensuring adaptability and safety across diverse voltage ranges while maintaining electrical safety even at high voltages like 230 VAC.
Implementation Method 1
an input-side rectifier or a rectifier circuit for converting incoming digital signals in AC form into DC current
Implementation Method 2
two or a plurality n of series-connected, reverse-biased zener diodes
Implementation Method 3
an optocoupler for determining the state of the digital output connection
Implementation Method 4
an optocoupler for determining the state of the digital output connection
Data Source
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AI summary
Disclosed is a large-range input circuit for digital signals in the range of extra-low voltage signals ≤ 120 V and of low voltage signals < 1500 V, said input circuit comprising series-connected Zener diodes which are polarized in the reverse direction, each define at least one switching threshold in the range of the extra-low voltage signals or of the low-voltage signals, and can be selected to be active by not having same bridged, an auxiliary opto-coupler (50), which can be controlled by a microprocessor (8), being used to bridge the inactive Zener diode.