Two-Wire Transmitter Dynamic Voltage Control
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Solution Overview
Problem
Conventional two-wire transmitters face challenges in securing sufficient consumable power while maintaining circuit stability, particularly when the output current is small, limiting their performance and ability to enhance sensor S/N ratio and add functions.
Innovation Solution
The two-wire transmitter dynamically controls circuit voltage according to output current, using a shunt regulator circuit and a reference voltage processing unit to increase consumable power by adjusting the duty ratio of a PWM signal, ensuring sufficient power even at low output states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the shunt regulator fixes the circuit voltage in a low voltage range to stabilize circuit operation, then circuit stability is improved, but consumable power becomes insufficient when output current is small
Solution Approach 1:
The shunt regulator dynamically adjusts the circuit voltage based on the output current magnitude. When output current is small (e.g., 4 mA), the regulator increases circuit voltage to secure sufficient consumable power. When output current is large (e.g., 20 mA), the regulator maintains lower voltage to ensure adequate voltage headroom for operation. This dynamic adjustment resolves the contradiction between stability and power availability.
Solution Approach 2:
The circuit voltage parameter is changed based on operating conditions. The shunt regulator modifies the circuit voltage level according to the output current, transitioning from a fixed low voltage approach to a variable voltage approach. This parameter change enables the circuit to have sufficient power margin at low currents while maintaining stability at high currents.
2Productivity
If the output current increases to provide more signal range, then the signal output capability is improved, but the voltage drops across feedback and detection resistors increase, lowering the securable circuit voltage
Solution Approach 1:
The shunt regulator dynamically compensates for voltage drops caused by increased output current. As output current increases from 4 mA to 20 mA, the regulator adjusts the circuit voltage to maintain adequate headroom for circuit operation. This dynamic compensation allows the full output current range to be utilized without sacrificing circuit voltage margin.
3Productivity
If more consumable power is secured to enhance circuit operation speed and add functions, then performance is improved, but it becomes difficult to maintain circuit operation stability with conventional shunt regulator design
Solution Approach 1:
The shunt regulator provides dynamic voltage adjustment that adapts to power consumption requirements. When high performance is needed, the regulator can increase circuit voltage to provide more power margin for faster operation and additional functions. When standard operation is sufficient, the regulator maintains lower voltage for stability. This dynamic adaptation resolves the contradiction between performance enhancement and stability maintenance.
Data Source
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AI summary
There is provided a two-wire transmitter (100) which is connected to an external circuit (10) by two transmission lines (L1,L2) and which outputs a certain current signal to the external circuit using the external circuit as a power source. The two-wire transmitter includes: a sensor (102) configured to convert a physical quantity into a first electrical signal (51) and output the first electrical signal; a signal processing circuit (104) configured to perform certain processing on the first electrical signal and output a second electrical signal; a constant current circuit (106) configured to determine the certain current signal to be output to the external circuit, based on the second electrical signal; a reference voltage output unit (110) configured to output a reference voltage based on the second electrical signal; and a shunt regulator circuit (108) configured to determine a circuit voltage of the two-wire transmitter based on the reference voltage.