Ultrasound Probe T/R Switch Circuit With Shunt-Controlled MOSFET Isolation
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Solution Overview
Problem
Existing switch circuits for ultrasound probes require a large area and high power consumption, particularly due to the need for multiple high-voltage MOSFETs and capacitors, which complicates the integration of transmitter/receiver circuits and increases heat generation, limiting the miniaturization and efficiency of ultrasonic diagnosis apparatuses.
Innovation Solution
A switch circuit utilizing three high-voltage MOSFETs with a shunt circuit that includes a resistor and capacitor, allowing for adjustable time constants and low power consumption by eliminating steady-state current flow, and incorporating a PMOSFET for voltage control to manage switch states effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple high-voltage MOSFETs and capacitors are used to protect the receiver circuit from high-voltage signals, then the receiver circuit is reliably protected, but the circuit area increases and power consumption increases
Solution Approach 1:
The patent combines multiple protection functions into a single transmit receive switch circuit that integrates the switching function and protection function. The switch circuit uses three MOSFETs (two NMOSFETs and one PMOSFET) with shared gates and sources to achieve both transmission and reception modes while protecting the receiver circuit, thereby reducing the overall circuit area compared to using separate protection circuits.
Solution Approach 2:
The transmit receive switch circuit serves multiple functions: it acts as a switch to control signal transmission, protects the receiver circuit from high-voltage damage, and enables both transmit and receive modes. This multi-functionality eliminates the need for separate protection circuits and reduces the total number of components required.
2Reliability
If multiple high-voltage MOSFETs and capacitors are used to protect the receiver circuit from high-voltage signals, then the receiver circuit is reliably protected, but the power consumption increases due to steady-state current
Solution Approach 1:
The patent employs periodic switching action where the transmit receive switch alternates between transmit mode and receive mode. During transmit mode, the switch is in the off state to protect the receiver; during receive mode, the switch is in the on state to allow signal passage. This periodic switching eliminates continuous steady-state current flow, thereby reducing power consumption while maintaining protection reliability.
3Power
If a large area circuit is used to implement high-voltage device, then the high-voltage signal handling capability is sufficient, but the ultrasound probe cannot be miniaturized
Solution Approach 1:
The patent merges the high-voltage switching function and receiver protection function into a single integrated transmit receive switch circuit. By sharing gates and sources between MOSFETs and using a compact three-MOSFET configuration, the circuit achieves sufficient high-voltage signal handling capability while minimizing the occupied area, thereby enabling ultrasound probe miniaturization.
4Reliability
If multiple high-voltage devices are used in the circuit, then the high-voltage signal protection is adequate, but the heat generation increases
Solution Approach 1:
The transmit receive switch operates in periodic transmit and receive modes, eliminating continuous steady-state current flow. During transmit mode, the switch is off, blocking high-voltage signals and preventing heat generation in the receiver path. During receive mode, the switch is on but only for brief periods to capture reflected signals. This periodic operation significantly reduces overall heat generation while maintaining adequate high-voltage protection.
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 solution achieves a compact switch circuit with low power consumption, enabling smaller area occupation and reduced heat generation, thus improving the efficiency and image quality of ultrasonic diagnosis apparatuses by effectively isolating high-voltage signals from low-voltage receiver circuits.
Implementation Method 1
a capacitor is connected between the gate and source of two NMOSFETs, which are basic elements, and adapted to retain a gate-source voltage in order to maintain a switch-on state and a switch-off state
Implementation Method 2
When a signal having a negative voltage relative to a reference voltage is applied to the input terminal, a switch that temporarily turns on causes the shunt circuit to short-circuit the common gate and the common source
Data Source
AI summary
A transmit receive switch circuit has a first MOSFET (MN1) and a second MOSFET (MN2), goes into a switch-off state at the time of transmission, and goes into a switch-on state at the time of reception. The first MOSFET (MN1) and the second MOSFET (MN2) are connected between an input terminal (SWIN) and an output terminal (SWOUT). The switch circuit includes a shunt circuit (SHNT) that is connected between a common gate (COMG) and a common source (COMS), the common gate being connected to the gates of the first and second MOSFETs, and the common source being connected to the sources of the first and second MOSFETs. When a signal having a negative voltage relative to a reference voltage is applied to the input terminal, a switch that temporarily turns on causes the shunt circuit to short-circuit the common gate and the common source.