Electronic Load Circuit Using FET for Stable Voltage Testing
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Solution Overview
Problem
Existing electronic loads, such as sliding rheostats, are unsuitable for testing power source stability due to their lack of constant current load characteristics and inductive properties, leading to inaccurate testing results.
Innovation Solution
An electronic load circuit comprising a voltage supply device, amplification circuit, field effect transistor, current sampling resistor, and protection circuits that provide a constant or dynamic current load, using a programmable control unit and FET to accurately sample current and prevent overheating, replacing coil-wound rheostats with a transistor-based design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a sliding rheostat is used as the electronic load, then the device can provide variable resistance for testing, but it lacks constant current load characteristics and has inductive properties that reduce measurement precision
Solution Approach 1:
The patent replaces the mechanical sliding rheostat with an electronic circuit using a field effect transistor (FET) as a voltage-dependent resistor. This substitution eliminates the inductive characteristics of coil-wound rheostats and provides true constant current load capability, thereby resolving the measurement precision issue while maintaining variable resistance functionality through electronic control.
Solution Approach 2:
The patent changes the resistance characteristic from inductive (sliding rheostat) to purely resistive (FET-based voltage-dependent resistor). By controlling the gate voltage of the FET, the resistance can be varied electronically to provide constant current load characteristics, improving measurement accuracy for power source stability testing.
2Device complexity
If a sliding rheostat is used, then the structure is simple, but the inductive characteristic causes inaccurate testing results
Solution Approach 1:
The patent replaces the mechanical sliding rheostat structure with an electronic FET-based voltage-dependent resistor circuit. This substitution eliminates the inductive characteristics inherent in coil-wound rheostats while providing the same variable resistance function, thereby improving measurement precision without significantly increasing device complexity.
3Reliability
If protection circuits are added to prevent damage from sudden power changes, then reliability improves, but device complexity increases
Solution Approach 1:
The patent incorporates protection circuits that are activated beforehand to prevent damage from sudden power changes. The first protection circuit prevents overheating of the voltage-dependent resistor, and the second protection circuit protects the amplification circuit from voltage spikes. These circuits are designed to activate automatically under abnormal conditions, improving reliability while maintaining reasonable device complexity through targeted protection rather than comprehensive system redesign.
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
The electronic load achieves accurate and stable power voltage testing by maintaining a constant or dynamic current load, providing more reliable testing results and preventing damage from sudden power changes, while being suitable for various testing scenarios.
Implementation Method 1
a field effect transistor (FET) 30 configured to function as a voltage dependent resistor
Implementation Method 2
an operational amplifier 25, a first feedback resistor R2, a second feedback resistor R3
Implementation Method 3
The compensation circuit 29 filters out high-frequency interference signals in the amplified control voltage
Implementation Method 4
a current sampling resistor R0... sampling the current flowing therethrough
Data Source
AI summary
An electronic load for testing stability of a power voltage of a power source under test (PSUT) includes a voltage supply device, a field effect transistor (FET), an amplification circuit, and a current sampling resistor. The amplification circuit includes a first input, a second input, and an output. The voltage supply device is connected to the first input. The second input is connected to a source electrode of the FET. The output is connected to a gate electrode of the FET. A drain electrode of the FET is connected to the PSUT. One end of the current sampling resistor is grounded, and the other end of the current sampling resistor is connected to the source electrode of the FET and the second input. The voltage supply device outputs a control voltage. The amplification circuit amplifies the control voltage and drives the FET using the amplified control voltage.