High-Voltage Op Amp Power Management for Ultrasound Imaging
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Solution Overview
Problem
High-voltage operational amplifiers in ultrasound equipment generate spurious signals during power-up and power-down transients, leading to power consumption and potential image defects in ultrasound imaging systems, as they struggle to efficiently manage low-voltage signals and alternate between transmission and reception phases.
Innovation Solution
A high-voltage operational amplifier design with a source follower output stage and current mirror circuits that use different bias currents for active and inactive states, allowing for nearly zero power consumption during inactivity and minimizing spurious signals by controlling node voltages during power transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the operational amplifier is kept active to handle low-voltage signals, then signal processing capability is maintained, but power consumption from high-voltage supplies increases
Solution Approach 1:
The operational amplifier is designed with dynamic power management capability, allowing it to switch between active and powered-down states. The circuit includes control logic that monitors the operational state and dynamically adjusts power supply connections, enabling the amplifier to be fully powered down during inactive periods while remaining readily activatable when needed.
2Use of energy by moving object
If the operational amplifier is powered down to save power, then power consumption is reduced, but spurious signals are generated during power-up and power-down transients
Solution Approach 1:
Before the operational amplifier is fully powered down, its output is preemptively disconnected from the load using a switch or transmission gate. This preliminary disconnection prevents spurious transient signals generated during the power-down process from reaching the load (ultrasound probe), while allowing the amplifier to be completely powered off to minimize power consumption.
3Power
If the operational amplifier operates in high-voltage mode, then output voltage capability is achieved, but efficiency in handling low-voltage signals decreases
Solution Approach 1:
The system is segmented into two distinct operational paths: a high-voltage linear driver path for transmission phases and a low-voltage receiver path for reception phases. During reception, the high-voltage amplifier is completely powered down and the low-voltage receiver handles the signal, optimizing efficiency for low-voltage signal processing while maintaining high-voltage capability when needed.
Data Source
AI summary
An operational amplifier including an input stage coupled to an input terminal, an output stage coupled to an output terminal, and a gain node between the input stage and the output stage. A bias current source is couplable to the input stage to supply a bias current thereto and a current mirror circuit mirrors the bias current toward the gain node and the output stage. A switch circuit includes a switch activatable to bring the gain node to a pre-bias voltage and a switch coupled to the output stage and switchable between a first state and a second state in which the output stage is active and non-active, respectively—. A further switch circuit is coupled to the output terminal and switchable between a first state and a second state in which the output stage is coupled to the output terminal and to a reference level, respectively.