Load Drive Circuit Open Load and Supply Fault Detection
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Solution Overview
Problem
The existing load drive circuit with a high-side configuration faces complexity and size issues due to the need for multiple reference power supply circuits to differentiate between open loads and supply faults, and the determination of supply faults is impeded by the connection of a voltage follower to the output terminal.
Innovation Solution
A load drive circuit with a switching element connected between the positive electrode of a DC power supply and an output terminal, including a constant current element and resistors to detect open loads and supply faults, using threshold voltages and MOSFETs to differentiate between the two conditions, and an oscillator to indicate supply faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple reference power supply circuits are provided to distinguish between open load and supply fault, then detection accuracy is improved, but device complexity and size increase
Solution Approach 1:
The patent combines multiple reference power supply circuits into a single shared reference power supply circuit that serves both the open load detection circuit and the supply fault detection circuit. This merging eliminates the need for separate reference power supply circuits for each detection function, thereby reducing device complexity and size while maintaining the ability to distinguish between open load and supply fault conditions through voltage comparisons.
Solution Approach 2:
The reference power supply circuit is designed to provide universal reference voltages for multiple detection purposes simultaneously. It supplies reference voltages to both the open load detection circuit and the supply fault detection circuit, enabling a single circuit to perform multiple functions and avoiding the need for dedicated reference power supplies for each detection type.
2Reliability
If voltage follower output is connected to output terminal to detect supply fault, then detection function is added, but determination is impeded
Solution Approach 1:
The patent segments the detection functions into separate circuits: the open load detection circuit and the supply fault detection circuit. Each circuit independently performs its specific detection function without interfering with the other. The voltage follower output is used specifically for supply fault detection through a dedicated comparison circuit, while open load detection uses a separate voltage comparison mechanism, thereby avoiding determination impediments.
3Device complexity
If simple configuration is used for load drive circuit, then device size and cost are reduced, but ability to differentiate open load and supply fault is compromised
Solution Approach 1:
The patent introduces intermediary comparison circuits that facilitate fault differentiation without requiring complex circuitry. The open load detection circuit uses a comparison circuit to compare the output terminal voltage with a reference voltage, while the supply fault detection circuit uses another comparison circuit to compare the voltage follower output with a reference voltage. These intermediary comparison mechanisms enable accurate fault differentiation using relatively simple circuit configurations.
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 configuration allows for simple differentiation between open loads and supply faults without multiple reference power supply circuits, improving reliability, reducing cost, and minimizing size.
Implementation Method 1
a resistor (31) connected between the constant current element (11) and the negative electrode of the direct current power supply (5)
Implementation Method 2
The voltage of the output terminal accompanying a failure of supply to the load is regulated by, for example, the voltage value of the power supply being divided by the resistance value of the supply fault and the resistance value of the load.
Implementation Method 3
an open load detection circuit (21) that detects an opening of the load when the voltage of the output terminal (9) is higher than the value of a first threshold voltage and lower than the value of a second threshold voltage subtracted from the voltage of the direct current power supply (5) when the switching element (Q1) is in an off-state
Data Source
AI summary
An open load and a supply fault are differentiated between and detected with a simple configuration. A switching element (Q1) connected between the positive electrode of a direct current power supply and an output terminal (9) is caused to carry out a switching operation, thereby driving a load (7) connected to the output terminal (9). A load trouble detection circuit (21) that detects an opening of the load (7) or a supply fault when the voltage of the output terminal (9) is higher than the value of a first threshold voltage, and a supply fault detection circuit (25) that detects a failure of supply to the power supply of the load (7) when the voltage of the output terminal (9) is higher than the value of a second threshold value voltage subtracted from the power supply voltage when the switching element (Q1) is in an off-state, are included.