Vehicle Circuit Assembly Using Current Mirroring for Overload Detection
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Solution Overview
Problem
Existing vehicle circuit arrangements face challenges in cost-effectively supplying power-intensive external loads due to the limitations of integrated high-side switches with low output power, requiring additional expensive components for high-performance supply.
Innovation Solution
Incorporating a Widlar current mirror circuit in PNP configuration, which mirrors the current drawn by the load onto the high-side switch output, allowing detection of overload conditions and enabling automatic error correction or load shutdown through a microcontroller-controlled shutdown device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an integrated high-side switch with low output power is used, then the device complexity and cost are reduced, but the power delivery capability to the load is insufficient
Solution Approach 1:
A Widlar current mirror circuit is introduced as an intermediary between the high-side switch and the load. This current mirror circuit amplifies the limited current from the low-power high-side switch to deliver sufficient current to the high-power load, resolving the power delivery limitation without requiring a high-power switch
Solution Approach 2:
The current mirror circuit changes the current parameter through a defined transformation ratio. The circuit transforms the small current from the high-side switch output into a larger current at the load side, enabling the low-power switch to control a high-power load
2Power
If the current carrying capacity of the high-side switch output is increased to match the load's nominal current consumption, then the power delivery capability is improved, but the overload detection capability is lost
Solution Approach 1:
The current mirror circuit acts as an intermediary that decouples the current carrying capacity requirement from the overload detection point. The high-side switch only needs to carry a small monitoring current, while the current mirror handles the power delivery, enabling both adequate power supply and sensitive overload detection
Solution Approach 2:
The current path is segmented into a monitoring path (through the high-side switch) and a power delivery path (through the current mirror to the load). This segmentation allows the high-side switch to operate within its current carrying capacity while still enabling control and detection of higher power loads
3Power
If additional expensive components are added to increase the output power of the high-side switch, then the power delivery capability is improved, but the cost-effectiveness deteriorates
Solution Approach 1:
The current mirror circuit creates a current copy with amplification. Instead of using an expensive high-power switch, the circuit copies and amplifies the current from a low-power switch, achieving the same effect at lower cost
Solution Approach 2:
The solution uses inexpensive standard components (transistors, resistors) to build the current mirror circuit, replacing the need for expensive high-power switch components. The individual components are low-cost, even though they work together to achieve high-power delivery
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 the integration of high-side switches with low output power to supply loads with significantly higher nominal power, providing cost-effective and reliable overload protection and automatic error handling.
Implementation Method 1
a Widlar current mirror circuit in PNP configuration, wherein the emitter of a first transistor of a first mirror half of the Widlar current mirror circuit is connected to the output of the high-side switch via a series-connected ohmic scaling resistor
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a vehicle circuit assembly (1) for supplying an electric load (2) with a vehicle on-board voltage (UFB) in order to detect an overload, said electric load (2) having a specifiable nominal power. The vehicle circuit assembly comprises: - a vehicle on-board voltage input (E1) and - a controller (3) for controlling a vehicle function, wherein the controller (3) has an integrated semiconductor component (3a), for example a system basis chip (SBC), and the integrated semiconductor component has an integrated high-side switch (S1) which is connected to the vehicle on-board voltage input (E1) in order to switch a vehicle on-board voltage (UFB) being applied to the vehicle on-board voltage input (E1) to a high-side switch output (A1). The high-side switch output (A1) has a specified current-carrying capacity, and the controller (3) is designed to detect the output current (IA1) of the high-side switch output (A1), the nominal power consumption of the nominal power to be provided lying above the specified current-carrying capacity of the high-side switch output (A1).