Implantable Pulse DAC Slew Rate Control for Ringing Reduction
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Solution Overview
Problem
Current implantable pulse generators (IPGs) face limitations in producing stimulation pulses with controlled slewed amplitude transitions, leading to unwanted oscillations and inefficiencies due to sharp transitions, which can impact the reliability and power consumption of the device.
Innovation Solution
The development of a programmable digital-to-analog converter (DAC) circuitry that includes a master DAC with stages for digital-to-analog voltage conversion, slew rate control, and current generation, allowing for the formation of pulses with programmable slew rates and controlled amplitude transitions, reducing ringing and improving pulse reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional DAC circuitry is used to generate stimulation pulses, then the device structure is simple, but sharp amplitude transitions cause unwanted oscillations and reduce reliability
Solution Approach 1:
The DAC circuitry is divided into multiple independent stages: a first stage performing digital-to-analog voltage conversion and a second stage performing slew rate control. This segmentation allows each stage to be optimized for its specific function, reducing oscillations through controlled transitions while keeping the overall device manageable through modular design.
Solution Approach 2:
The patent introduces an intermediate slew rate control stage between the digital-to-analog conversion stage and the current generation stage. This intermediary stage acts as a buffer that smooths sharp transitions by controlling the rate of change of the analog signal, thereby reducing unwanted oscillations without adding excessive complexity to the overall system.
2Loss of energy
If sharp amplitude transitions are used in stimulation pulses, then the circuit operation is simple, but oscillations increase and power efficiency decreases
Solution Approach 1:
The patent implements dynamic slew rate control in the second stage, where the rate of change of the analog signal is actively managed during transitions. This dynamic control allows the circuit to operate efficiently by adjusting the transition characteristics in real-time, reducing energy loss from oscillations while maintaining operational simplicity through automated control mechanisms.
Solution Approach 2:
The patent changes the temporal parameters of the stimulation pulse by controlling the slew rate (rate of change of amplitude) in the second stage. By adjusting this parameter, the system reduces energy loss from oscillations without fundamentally changing the circuit operation, as the same DAC architecture is used but with optimized timing characteristics.
3Adaptability or versatility
If programmable slew rate control is added to DAC circuitry, then waveform complexity increases, but the ability to produce complex waveforms is limited by traditional DAC architecture
Solution Approach 1:
The two-stage DAC architecture serves multiple functions: the first stage performs standard digital-to-analog voltage conversion, while the second stage provides slew rate control that enables both simple and complex waveform generation. This multi-functional design increases adaptability without requiring completely different circuit architectures for different waveform requirements.
Solution Approach 2:
The patent implements a nested structure where the slew rate control stage is functionally embedded within the DAC architecture. The second stage processes the output of the first stage, creating a hierarchical arrangement where complex waveform capabilities are achieved through nested functional layers rather than requiring a complete architectural overhaul.
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
This solution enables the generation of stimulation pulses with controlled slewed transitions, reducing unwanted oscillations, improving reliability, and optimizing power usage, while allowing for more complex waveform shapes that were previously difficult to produce with traditional DAC circuitry.
Implementation Method 1
digital-to-analog converter (DAC) circuitry configured to receive a plurality of digital amplitude signals defining an input pulse
Implementation Method 2
the DAC circuitry is further configured to receive a plurality of digital slew rate signals prescribing a slew rate, and to form the input pulse as an output pulse at one of the plurality of electrode nodes that is slewed proportionally with the slew rate
Data Source
Figure 1A~1C
Figure 2A
Figure 2B
AI summary
Digital-to-analog converter (master DAC) circuitry is disclosed that is programmable to set a controlled slew rate for pulses that are otherwise defined as having sharp amplitude transitions. For example, when producing a biphasic pulse, the constant amplitude and duration of first and second pulses phases can be defined and provided to the DAC in traditional fashion. Slew rate control signals control a slew rate DAC within the master DAC, which prescribes a slew rate that will appear at sharp transitions of the defined biphasic pulses, i.e., at the beginning of the first phase, at the transition from the first to the second phase, and at the end of the second phase. The slew rate can vary with the duration or frequency of the pulses, with lower slew rates used with longer durations and/or lower frequencies, and with higher slew rates used with shorter durations and/or higher frequencies.