High-Side Switch Current Sensing Using On-Resistance Isolation
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Solution Overview
Problem
Current detection methods for power electronic switches driven by high side are bulky, costly, and require expensive operational amplifiers due to high common-mode voltage, which is a challenge particularly in applications like automobiles.
Innovation Solution
A high-side current acquisition and safety protection circuit that utilizes the on-state internal resistance of the power electronic switch for current sensing, eliminating the need for additional sensors and incorporating an isolated power source and control module with a logic control unit to provide safe and reliable protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensor in the form of a current loop or Hall device is used, then current detection accuracy is improved, but device volume and cost increase
Solution Approach 1:
The patent extracts the current sensing function from external sensors and implements it using the intrinsic on-state resistance of the power electronic switch itself. By utilizing the voltage drop across the switch's internal resistance during conduction, the system eliminates the need for separate current loop or Hall effect sensors, thereby reducing device volume while maintaining detection capability
Solution Approach 2:
The power electronic switch serves dual purposes: it performs its primary switching function while simultaneously providing the sensing element through its on-state resistance. The voltage developed across its internal resistance during conduction is used for current detection, making the switch self-sufficient for both power delivery and measurement functions
2Measurement precision
If an operational amplifier with high common-mode characteristic is used, then current detection accuracy is improved, but cost increases
Solution Approach 1:
The patent introduces an isolated power source as an intermediary element that references its negative terminal to the positive electrode of the power supply. This configuration serves as a mediator that establishes a stable voltage reference point, enabling accurate current measurement through the switch's on-state resistance without requiring expensive operational amplifiers with high common-mode rejection ratios
Solution Approach 2:
The patent changes the reference voltage parameter by connecting the negative terminal of the isolated power source to the positive electrode of the power supply instead of ground. This parameter change creates a floating reference system that accurately measures the voltage drop across the switch's on-state resistance, achieving precise current detection with standard operational amplifiers
3Measurement precision
If an integrated circuit current sensor is used, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent makes the power electronic switch multi-functional by enabling it to perform both its primary power switching role and current sensing function simultaneously. Through the isolated power source configuration, the same switch that controls power flow also provides the sensing signal, eliminating the need for separate integrated circuit current sensors and reducing overall system cost
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 approach reduces system volume and cost while ensuring reliable performance by using the internal resistance of the power electronic switch for current sensing, providing a simple, intelligent, and cost-effective solution for current detection and protection.
Implementation Method 1
a control module for sensing the current source signal contained in the power electronic switch and converting the sensed current source signal into a control signal for safety protection of the power electronic switch
Data Source
AI summary
The present invention provides a high-side current acquisition and safety protection circuit of a power electronic switch, including a power electronic switch for driving a load, a power supply for providing power energy for the power electronic switch, a control module for sensing the current source signal contained in the power electronic switch and converting the sensed current source signal into a control signal for safety protection of the power electronic switch, and an isolated power source that provides working power for the control module, wherein the negative pole of the isolated power source is connected to the positive pole of the power supply. The invention has simple structure, reliable control, and low cost.