Amplifier Load Current Sensing Without a Shunt Resistor
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Solution Overview
Problem
Traditional load current sensing techniques require an additional shunt resistor, increasing component cost and complexity due to the need for a temperature-insensitive low-resistance shunt resistor, which complicates the sensing process.
Innovation Solution
Sensing the load current by obtaining a voltage drop across the internal impedance of the amplifier and computing the load current using this voltage drop and the internal impedance, eliminating the need for a shunt resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an additional shunt resistor is placed in series with the load to sense load current, then load current sensing is achieved, but component cost increases and device complexity increases
Solution Approach 1:
The patent extracts the sensing function from an external shunt resistor and relocates it to the amplifier's internal output impedance. By measuring the voltage drop across the internal output impedance, the system eliminates the need for an external shunt resistor while maintaining load current sensing capability. This is achieved through the relationship I_load = V_out / Z_out, where the internal impedance serves the dual purpose of signal output and current sensing.
Solution Approach 2:
The patent makes the amplifier's internal output impedance serve multiple functions: it continues to provide the output signal to the load while simultaneously functioning as the sensing element for load current measurement. This multi-functionality eliminates the need for separate sensing components, reducing both component count and system complexity while maintaining accurate current sensing.
2Ease of operation
If a shunt resistor with low resistance value is used to be non-intrusive to the amplifier and load, then signal transmission is not affected, but temperature sensitivity becomes a problem requiring extra attention
Solution Approach 1:
The patent leverages the amplifier's existing internal output impedance characteristics to perform sensing without requiring external temperature compensation components or circuits. The internal impedance already exhibits the necessary temperature stability properties, and the amplifier's existing temperature compensation mechanisms (if present) automatically compensate for any drift, eliminating the need for additional compensation circuitry.
3Measurement precision
If an additional shunt resistor is added for load current sensing, then current measurement is enabled, but manufacturing cost increases
Solution Approach 1:
The patent makes the amplifier's internal output impedance serve dual purposes: delivering the output signal to the load and enabling load current sensing. This eliminates the need for an additional shunt resistor component, directly reducing bill of materials cost and simplifying the manufacturing process while maintaining accurate current measurement capability.
4Measurement precision
If a shunt resistor is used for load current sensing, then current sensing is achieved, but the sensing process becomes more complex due to temperature insensitivity requirements
Solution Approach 1:
The patent extracts the sensing function from an external temperature-sensitive shunt resistor and relocates it to the amplifier's internal output impedance. This internal impedance is inherently more stable and integrates seamlessly with the amplifier's existing temperature compensation mechanisms, thereby simplifying the overall sensing process and reducing the difficulty of maintaining measurement accuracy across temperature variations.
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 method reduces component costs and simplifies the sensing process by eliminating the need for a shunt resistor, while maintaining accurate load current measurement, suitable for applications like loudspeaker protection and linearization.
Implementation Method 1
obtaining a voltage drop across internal impedance of the amplifier and computing the load current using the internal impedance and the voltage drop across the internal impedance
Data Source
Figure 1
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Figure 3A~3B
AI summary
A system and method for sensing a load current that flows from an amplifier into a load of the amplifier involves obtaining a voltage drop across internal impedance of the amplifier and computing the load current using the internal impedance and the voltage drop across the internal impedance.