PWM Energy Supply Circuit for Plasma Ignition and Maintenance
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Solution Overview
Problem
Existing electrosurgical systems face challenges in providing efficient, safe, and cost-effective high-frequency voltage supply for both igniting and maintaining plasma in electrosurgical instruments, particularly in controlling electrical power during different operational phases.
Innovation Solution
An energy supply device utilizing multiple PWM stages and a transformer, controlled by a control device to switch between synchronous and staggered modes, enabling efficient power delivery during plasma ignition and precise control during plasma maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single high-power circuit is used to ignite plasma, then ignition reliability is improved, but circuit complexity and cost increase
Solution Approach 1:
The power delivery is segmented into two distinct phases: ignition phase using high power from all PWM stages simultaneously, and maintenance phase using lower power. This segmentation allows the system to achieve reliable ignition without requiring a continuously complex high-power circuit, as the high power is only needed temporarily during ignition.
Solution Approach 2:
The control device dynamically switches between synchronous control mode (all PWM stages in phase) for ignition and staggered control mode (PWM stages offset) for maintenance. This dynamic adaptation allows the circuit to simplify its operation after ignition, reducing effective complexity while maintaining reliability during the critical ignition phase.
2Reliability
If high electrical power is provided continuously, then plasma ignition is ensured, but energy efficiency deteriorates
Solution Approach 1:
The system employs periodic high-power pulses during the ignition phase to reliably establish plasma, then transitions to lower continuous power for maintenance. This periodic high-power action ensures ignition reliability while avoiding continuous high-power consumption that would waste energy.
Solution Approach 2:
The control device changes the operating parameters of the PWM stages between phases: during ignition, all stages operate at high duty cycle simultaneously; during maintenance, the duty cycles are reduced and staggered. This parameter adaptation optimizes energy efficiency while ensuring reliable ignition when needed.
3Loss of energy
If precise power control is implemented during plasma maintenance, then energy efficiency is improved, but control complexity increases
Solution Approach 1:
The control device implements dynamic switching between two control modes: synchronous control for ignition and staggered control for maintenance. This dynamic approach provides precise power control during maintenance through the staggered configuration, while avoiding the need for continuously complex control algorithms by using a simpler synchronous mode during ignition.
Solution Approach 2:
The system changes control parameters between phases: during maintenance, individual PWM stages are controlled with staggered duty cycles to achieve precise power delivery and energy efficiency. This parameter change from synchronous to staggered control provides the needed precision without requiring continuously complex control mechanisms.
4Device complexity
If multiple PWM stages are controlled synchronously, then circuit simplicity is maintained, but power control precision deteriorates
Solution Approach 1:
The control device dynamically selects between synchronous control mode (simple but less precise) for ignition and staggered control mode (more precise) for maintenance. This dynamic switching allows the system to use the simpler synchronous control when precision is less critical, while transitioning to precise staggered control when power control accuracy is needed during maintenance.
Solution Approach 2:
The system periodically uses synchronous control during the ignition phase when simplicity is acceptable, then transitions to staggered control during the maintenance phase when precision is required. This periodic switching between control modes allows the system to maintain simplicity when needed while achieving precision when necessary.
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 allows for high efficiency during plasma ignition while ensuring precise power control during maintenance, reducing circuit complexity and cost, and enhancing safety with galvanic isolation.
Implementation Method 1
The transformer comprises a primary side and a secondary side. A first connection point of the primary side of the transformer is electrically coupled to the common node of the several PWM stages. The second connection point of the primary side of the transformer can be connected to a reference potential.
Implementation Method 2
Each PWM stage comprises an input terminal and an output terminal. The PWM stages are configured to be electrically coupled to a DC voltage source at their input terminal. The output terminals of the several PWM stages are electrically coupled to each other at a common node.
Implementation Method 3
In medical procedures using minimally invasive endoscopy, fast and reliable tissue sealing is of great importance, since even a very small amount of blood can obstruct a surgeon's view. This could make the procedure more difficult or even impossible. To seal the tissue, the relevant tissue can be heated and sealed using a high-frequency current
Data Source
AI summary
An energy supply device for an electrosurgical instrument provides several operational phases. In a first operating phase for igniting a plasma at the electrosurgical instrument, several pulse width modulated (PWM) stages are controlled synchronously to generate a rectangular voltage waveform. In a second operating phase to maintain the plasma, the several PWM stages are controlled individually and, if necessary, with multiple switching operations per period of the output signal to be generated.