Integrated Current Flow Sensing Using PCB Trace Impedance
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Solution Overview
Problem
Existing half-bridge circuit designs for power electronics require external resistors to monitor current, which increase cost, complexity, and energy loss due to added voltage drop.
Innovation Solution
A method to determine current through a power switch circuit by measuring voltage across the inherent impedance of the circuit connections using a four-wire measurement, eliminating the need for external resistors and incorporating a temperature sensor for accurate current calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external resistor is used to monitor current in a half-bridge circuit, then current measurement capability is achieved, but circuit complexity and cost increase
Solution Approach 1:
The patent extracts the current measurement function from the external resistor and relocates it to the PCB trace itself. By using the inherent impedance of the PCB trace as the sensing element and eliminating the external resistor, the circuit complexity is reduced while maintaining current measurement capability through voltage measurement across the trace impedance.
Solution Approach 2:
The patent merges the current carrying function and the current sensing function into a single component - the PCB trace. The same trace that carries the current also serves as the sensing element, eliminating the need for separate external resistors and reducing overall circuit complexity.
2Measurement precision
If an external resistor is used to monitor current, then current measurement is enabled, but cost increases
Solution Approach 1:
The patent removes the external resistor component entirely and extracts the sensing function to the PCB trace. This elimination of discrete components reduces Bill of Materials (BOM) cost and simplifies the manufacturing process.
Solution Approach 2:
The patent utilizes the PCB trace itself, which is already present and inexpensive, as the sensing element. The inherent impedance of the copper trace provides sufficient sensing capability without requiring expensive external resistors, making the solution cost-effective.
3Measurement precision
If an external resistor is used for current monitoring, then current measurement is achieved, but energy loss increases due to voltage drop
Solution Approach 1:
The patent changes the impedance parameter of the sensing element from a fixed external resistor value to the variable inherent impedance of the PCB trace. By optimizing the trace geometry (width, length, thickness), the impedance can be controlled to minimize voltage drop and energy loss while maintaining adequate sensing capability.
4Reliability
If through-hole technology is used to construct a half-bridge circuit, then stability and electrical connections are achieved, but manufacturing complexity increases
Solution Approach 1:
The patent replaces the mechanical through-hole mounting system with a planar PCB trace-based system. The electrical connections are achieved through conductive traces on the PCB rather than physical wire connections through holes, eliminating the need for drilling, plating, and soldering of through-holes, thereby reducing manufacturing complexity.
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 provides accurate current measurement without external resistors, reducing costs and complexity while allowing the use of common, less expensive materials like copper, and improving manufacturability and reliability.
Implementation Method 1
a temperature sensor, wherein the temperature sensor is configured to determine the temperature of the current path
Implementation Method 2
the first current sense terminal and the second current sense terminal are configured to determine an amount of current in the current path
Data Source
AI summary
This disclosure is directed to techniques that may accurately determine the amount of current flowing through a power switch circuit by measuring the voltage across the inherent impedance of the circuit connections. One connection may include a low impedance connection between the power switch output and ground, where the low impedance connection may be on the order of milliohms. By using a four-wire measurement, the sensing connections are not in the current path, so the measured value may not be affected by the current. The connection that makes up the current path can be accomplished with a variety of conductive materials. Conductive materials may have a temperature coefficient of resistivity that may impact a measurement of electric current as the temperature changes. Measuring the temperature of the current path, along with the voltage across the connection, may allow a more accurate current measurement.