Ultrasound Isolation Switch Layout for Low-Parasitic Echo Reception
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Solution Overview
Problem
High voltage driving circuits for ultrasonic transducers in ultrasound applications introduce significant parasitic capacitance, degrading the quality of echo signals received by the transducer due to large components required to handle high voltages and frequencies.
Innovation Solution
A low voltage isolation switch is introduced between the high voltage driving circuit and the ultrasonic transducer, utilizing a driving block with transistors and diodes, and an isolation block with voltage limiters and diodes to minimize parasitic capacitance, ensuring correct transmission and reception of high voltage signals while isolating the transducer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage driving circuits are used to drive ultrasonic transducers, then the transducer can transmit high voltage pulses effectively, but large components are required which introduce significant parasitic capacitance that degrades echo signal quality
Solution Approach 1:
The driving circuit is divided into two separate circuits: a high voltage driving circuit for transmitting high voltage pulses to the transducer, and a low voltage receiving circuit for receiving echo signals. An isolation switch with isolation capacitor couples these two circuits, allowing the high voltage circuit to operate independently without introducing parasitic capacitance into the sensitive receiving path.
Solution Approach 2:
An isolation switch comprising an isolation capacitor is introduced as an intermediary element between the high voltage driving circuit and the low voltage receiving circuit. This isolation capacitor couples the two circuits while preventing the parasitic capacitance of the high voltage circuit from degrading the echo signal quality in the receiving path.
2Power
If large components are used in high voltage driving circuits, then high voltage and high frequency signals can be handled, but the components add high parasite capacitances in parallel to the transducer
Solution Approach 1:
The circuit is segmented into high voltage and low voltage domains with separate components optimized for each domain. The high voltage driving circuit uses components sized for power handling, while the receiving circuit uses small low parasitic capacitance components, with the isolation capacitor serving as the interface between the two domains.
Solution Approach 2:
The isolation capacitor acts as an intermediary that allows the high voltage circuit to use large components for power handling while preventing those components' parasitic capacitance from affecting the low voltage receiving circuit. This mediator enables each circuit to be optimized independently for its specific function.
3Power
If the transducer is directly connected to high voltage components, then high voltage pulse transmission is achieved, but the transducer receives degraded echo signals due to parasitic capacitance during reception
Solution Approach 1:
The direct connection between transducer and high voltage components is eliminated by segmenting the circuit into transmission and reception paths. During transmission, the high voltage driving circuit connects to the transducer; during reception, the isolation switch redirects the echo signal to the low voltage receiving circuit, preventing parasitic capacitance from degrading the measurement.
Solution Approach 2:
The isolation switch dynamically changes the circuit configuration based on whether the transducer is transmitting or receiving. When transmitting, it connects the high voltage driving circuit to the transducer; when receiving, it connects the low voltage receiving circuit to the transducer, optimizing the circuit for the current operation mode and preventing parasitic capacitance from degrading echo signal quality.
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 low voltage isolation switch effectively reduces parasitic capacitance, improving the quality of echo signals by isolating the transducer from high voltage components, thus enhancing the performance of the ultrasound transmission channel.
Implementation Method 1
an ultrasonic transducer usually comprises a piezoelectric crystal that is suitably biased for causing its deformation and the generation of the ultrasound signal or pulse
Implementation Method 2
The same probe is able to collect a return signal or echo
Data Source
AI summary
A low voltage isolation switch is suitable for receiving from a connection node a high voltage signal and transmitting said high voltage signal to a load via a connection terminal. The isolation switch includes a driving block connected between first and second voltage reference terminals and including a first driving transistor coupled between the first voltage reference (Vss) and a first driving circuit node and a second driving transistor coupled between the driving circuit node and the second supply voltage reference. The switch comprises an isolation block connected to the connection terminal (pzt), the connection node, and the driving central circuit node and including a voltage limiter block, a diode block and a control transistor. The control transistor is connected across the diode block between the connection node and the connection terminal and has a control terminal connected to the driving central circuit node.