Ground Fault Detection Circuit for Isolated Analog and Digital Grounds
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Solution Overview
Problem
Existing ground fault detection systems in circuits with multiple ground references struggle to accurately detect open circuits or resistive disconnections between isolated analog and digital ground nodes, leading to potential operational errors and noise interference.
Innovation Solution
A ground fault detection circuit that compares voltages between isolated ground nodes using diodes for electrostatic discharge protection, minimum and maximum voltage detection circuits, and a reference voltage circuit to determine voltage differences and indicate faults, with optional noise filtering using an analog delay circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple isolated ground references are used for analog and digital portions, then noise interference from digital switching is reduced, but ground fault detection becomes difficult and measurement precision deteriorates
Solution Approach 1:
The patent introduces an intermediary ground fault detection circuit that mediates between the isolated analog and digital ground references. This circuit includes voltage comparators and reference voltage sources that enable indirect measurement of ground faults without directly connecting the isolated ground nodes, thus maintaining noise isolation while enabling fault detection
Solution Approach 2:
The patent transitions from direct voltage measurement between ground nodes to measuring voltage differences through a third reference dimension. By introducing reference voltage sources and comparators that measure against a common reference, the system can detect ground faults in isolated grounds without compromising the noise isolation benefit
2Reliability
If voltage comparison method is used for ground fault detection, then detection capability is improved, but circuit complexity increases due to additional detection circuits
Solution Approach 1:
The ground fault detection circuit is designed to perform multiple functions: detecting open circuits, detecting resistive disconnections, and providing fault indication through existing output stages. By making the detection circuit multi-functional, the patent reduces the need for separate dedicated circuits for each detection type, thereby managing complexity while maintaining comprehensive detection capability
Solution Approach 2:
The detection circuit utilizes existing circuit elements and voltage sources within the system to perform ground fault detection, rather than requiring entirely separate external testing equipment. The circuit self-diagnoses ground faults by comparing voltages that are already present in the operational circuit, reducing additional complexity
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
Effectively detects open circuits and resistive disconnections between ground nodes, reducing noise interference and ensuring proper circuit operation by providing accurate fault indication and noise reduction.
Implementation Method 1
a first diode having an anode coupled to the first ground node and a cathode coupled to the second ground node, and a second diode having an anode coupled to the second ground node and a cathode coupled to the first ground node may be included. The first and second diodes may be electrostatic discharge protection diodes coupled between the first and second ground nodes.
Implementation Method 2
The minimum detection circuit may include one or more transistors coupled in a common drain/source follower configuration with a source terminal of the one or more transistors providing the voltage at the output node. The one or more transistors may be P-channel transistors.
Implementation Method 3
The maximum detection circuit may include two input nodes and an output node wherein the voltage at the output node follows a higher voltage of the first and second input nodes. The maximum detection circuit may include one or more transistors coupled in a common drain/source follower configuration with a source terminal of the one or more transistors providing the voltage at the output node.
Implementation Method 4
The reference circuit may include a voltage divider in parallel to the reference diode and configured to generate the reference voltage as a fraction of a voltage across the reference diode.
Implementation Method 5
A comparator configured to compare the reference voltage to a difference between the voltage at the first ground node and the voltage at the second ground node may be included.
Data Source
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AI summary
A ground fault detection circuit is configured to detect a ground fault in a circuit or system that has more than one ground reference. In an embodiment, an electronic circuit includes a first circuit coupled to a first ground node. The first ground node is coupled to a first ground reference. The electronic circuit also includes a second circuit coupled to a second ground node. The second ground node is coupled to a second ground reference. The ground fault detection circuit is configured to detect an open circuit between the first ground node and the first ground reference or between the second ground node and the second ground reference by comparing a voltage at the first ground node to a voltage at the second ground reference or comparing a voltage at the second ground node to a voltage at the first ground reference.