Output Stage Open Load Detection Without Feedback Pins
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Solution Overview
Problem
Conventional open load detection circuits in electrical systems, particularly in automotive applications, face challenges such as the need for additional feedback pins and high voltage robust circuitry, which can be impractical or unsafe, especially when detecting open load conditions in smart ignition modules where space or technical feasibility is limited.
Innovation Solution
An open load detection circuit that includes a circuit output configured to provide an output voltage, a switch coupled to a supply voltage, a delta voltage circuit to reduce the voltage magnitude, a current source to overcome switch voltage in open load conditions, and a comparator to generate a failure signal, allowing for open load detection without external feedback pins by applying a pull-up current throughout the switch-on time and monitoring voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional open load detection circuits are used, then open load detection is possible, but additional feedback pins and high voltage robust circuitry are required
Solution Approach 1:
The patent extracts the open load detection function from the main control unit and implements it within the smart ignition module itself. By placing the detection circuitry locally at the ignition module, the system eliminates the need for additional feedback pins to the central control unit while maintaining reliable open load detection capability.
Solution Approach 2:
The smart ignition module performs self-diagnosis by monitoring its own output stage conditions. The module uses internal circuitry to detect open load conditions at its output terminals without requiring external monitoring from the central control unit, enabling the system to serve its own detection needs.
2Measurement precision
If additional feedback pins are used for open load detection, then detection accuracy is improved, but space requirements and technical feasibility are reduced
Solution Approach 1:
The patent combines the open load detection function with the existing smart ignition module circuitry. By merging the detection capabilities into the module's existing structure, the system achieves accurate open load detection without requiring additional discrete feedback pins or external circuit board space.
3Reliability
If high voltage robust circuitry is implemented, then detection reliability is improved, but power consumption increases
Solution Approach 1:
The patent applies high voltage robust circuitry only when and where needed for open load detection, rather than throughout the entire system. The detection circuit uses high voltage capabilities selectively during detection phases while maintaining normal low-power operation during standard ignition control, thus achieving reliable detection without continuous high power consumption.
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 solution enables continuous open load detection during both transition and steady-state phases, reducing the risk of unsafe tristate modes and eliminating the need for additional feedback pins, thus enhancing safety and reducing power consumption while maintaining reliable control.
Implementation Method 1
the delta voltage circuit is coupled to the first switch to create a reduction in voltage magnitude of the first supply voltage to a switch voltage of the first switch provided to the circuit output
Implementation Method 2
the current source is coupled to the circuit output to provide a current to the circuit output, the current source configured to overcome the switch voltage provided to the circuit output in a case of an open load condition
Implementation Method 3
at least one comparator configured to provide a failure signal in the case of an open load condition
Data Source
AI summary
Systems, devices, methods, and techniques are disclosed for open load detection in the connections coming from output stages of electrical systems. In some examples, an open load detection circuit includes a circuit output configured to provide an output voltage to a load, a first switch coupled to the circuit output and coupled to a first supply voltage configured to switch the load, and at least one delta voltage circuit coupled to the circuit output configured to provide a delta voltage. The at least one delta voltage circuit is coupled to the first switch to create a reduction in voltage magnitude of the first supply voltage to a switch voltage of the first switch provided to the circuit output. The open load detection circuit also includes at least one current source coupled to the circuit output to provide a current to the circuit output.