High-Side Switch Low-Load Detection via Saturation Current Sensing
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Solution Overview
Problem
High-side switch arrangements in circuit breakers face complexity in diagnosing low-load situations due to the need for large resistors and complex circuitry to sense small currents, which increases resistance and requires high common-mode rejection, making it challenging to accurately determine low-load states without impairing the switch's performance.
Innovation Solution
A high-side switch arrangement that includes a switching transistor, an actuating transistor, and a diagnosis transistor with a saturation collector, where the diagnosis transistor senses its own saturation current to identify low-load situations, using a resistor between the base and emitter of the switching transistor to prevent unintended switching at high temperatures, and employing PNP transistors for precise threshold setting, allowing for reduced circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistor is used to sense small currents for low-load detection, then the low-load situation can be identified, but the resistance of the high-side switch increases significantly
Solution Approach 1:
The patent introduces a diagnosis transistor as an intermediary element that senses the saturation current of the actuating transistor. This mediator allows indirect measurement of the load current without placing a resistor in the main current path, thus avoiding the increase in switch resistance while still enabling accurate low-load detection through the saturation current measurement.
2Measurement precision
If large resistors are used to sense small currents, then small currents can be detected, but the circuit complexity and common-mode rejection requirements increase
Solution Approach 1:
The patent replaces the traditional mechanical/resistive current sensing method with a transistor-based saturation current sensing mechanism. Instead of using large resistors to convert small currents into measurable voltages, the invention uses the saturation current characteristics of a transistor to directly indicate small load currents, thereby reducing circuit complexity and eliminating the need for high common-mode rejection.
3Measurement precision
If the saturation current of the actuating transistor is evaluated directly, then the load current can be determined, but a wide spread and large load current range are obtained with no further saturation current
Solution Approach 1:
The patent applies local quality by introducing a dedicated diagnosis transistor with specific design characteristics optimized for saturation current sensing. This specialized component focuses the measurement function on a local level, providing clear and distinct saturation current signals that accurately reflect low-load conditions without the ambiguity present in direct actuating transistor evaluation.
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 efficient low-load identification with minimal circuit complexity, effectively preventing parasitic saturation currents and maintaining safe operation at high temperatures, while allowing for precise threshold setting and reduced impact on the high-side switch's resistance.
Implementation Method 1
a diagnosis transistor, the emitter of which is connected to the battery connection of the high-side switch arrangement and the collector of which is connected to the output connection of the high-side switch arrangement, wherein the diagnosis transistor has a saturation collector for sensing the saturation current of the diagnosis transistor
Implementation Method 2
The switching transistor in the high-side switch arrangement may contain a resistor connected between the base and the emitter of the switching transistor. Such a resistor has the particular advantage that the switching transistor remains safely off at high temperatures, when leakage currents can flow from PN junctions into the base
Implementation Method 3
Charge carriers which flow into the base zone, e.g. the epitaxial layer in the case of a lateral PNP transistor, of a lateral PNP transistor when the transistor is saturated can be picked up by means of known lateral structures. This additional collector collects the charge carriers which would flow into the base zone of the PNP transistor when the transistor is saturated
Data Source
AI summary
High-side switch arrangement having a switching transistor, the collector of which is connected to a battery connection of the high-side switch arrangement and the emitter of which is connected to an output connection of the high-side switch arrangement, an actuating transistor, the emitter of which is connected to the battery connection of the high-side switch arrangement and the collector of which is connected to the base of the switching transistor, and a diagnosis transistor, the emitter of which is connected to the battery connection of the high-side switch arrangement and the collector of which is connected to the output connection of the high-side switch arrangement, wherein the diagnosis transistor has a saturation collector for sensing the saturation current of the diagnosis transistor.