Linear Regulator With Dual Input Switching for Limp Home Reliability
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Solution Overview
Problem
Existing linear regulators fail to output a normal voltage when either of the input voltages is not supplied, limiting their functionality in vehicles with advanced automation systems where a limp home function is essential.
Innovation Solution
A linear regulator design that includes a control circuit to manage two input voltages, allowing it to output a normal voltage even if one of the input voltages is not supplied by switching between input voltages and using diodes to prevent backflow, and is packaged in a semiconductor format with specific terminal arrangements to prevent short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linear regulator uses a single input voltage configuration, then the device complexity is reduced, but the reliability deteriorates because it cannot operate when the input voltage is not supplied
Solution Approach 1:
The linear regulator is divided into two independent input channels (first input terminal with first output transistor, second input terminal with second output transistor), each capable of independently supplying power to the output terminal. This segmentation allows the regulator to tolerate input voltage loss by switching to the other channel when one fails.
Solution Approach 2:
The linear regulator is designed with multi-functionality to accept power from either the first input terminal or the second input terminal, or both simultaneously. The control circuit universally manages both input channels, enabling the device to maintain output voltage under various input conditions, thereby improving reliability without excessive complexity.
2Reliability
If the linear regulator uses both input voltages simultaneously, then the power supply redundancy is improved, but the difficulty of detecting and measuring deteriorates due to voltage selection complexity
Solution Approach 1:
The control circuit continuously monitors the voltage levels at both input terminals and automatically selects the appropriate input source based on real-time feedback. When both inputs are available, the control circuit detects which voltage is more suitable (higher stability or higher level) and switches accordingly, simplifying the detection and measurement process while maintaining redundancy.
Solution Approach 2:
The linear regulator employs dynamic voltage selection where the control circuit adapts the input source based on operating conditions. The system can dynamically switch between first and second input voltages, or between single-input and dual-input modes, making the power supply configuration flexible and easier to manage under varying conditions.
Data Source
AI summary
There is provided a linear regulator including: a first output transistor connected between a first input terminal to which a first input voltage is applied and an output terminal from which an output voltage is outputted; a second output transistor connected between a second input terminal to which a second input voltage is applied and the output terminal; and a control circuit configured to control the first output transistor when the second input voltage of a predetermined range is not supplied to the second input terminal, and to control the second output transistor when the first input voltage of the predetermined range is not supplied to the first input terminal.