High Voltage SCR Switching Circuit for IMD Latching Control
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Solution Overview
Problem
Conventional high voltage H-bridge circuits in implantable medical devices face operational difficulties due to the latching behavior of Silicon Controlled Rectifier (SCR) switches, which limits their control and substitution for Insulated Gate Bipolar Transistors (IGBTs, especially in delivering high voltage energy effectively.
Innovation Solution
A high voltage switching and control circuit that uses SCR switches connected in series with temporal offset gating signals to ensure simultaneous activation, allowing for efficient delivery of high voltage energy without the risks associated with latching behavior, by staggering the gating signals to turn ON the SCR switches in a serial delayed manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SCR switches are used in high voltage H-bridge circuits, then device size and cost are reduced, but operational control is limited due to latching behavior
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitors to specific voltage levels before SCR activation and using controlled sequencing where one SCR is turned on before the other. This ensures that when the second SCR is activated, the voltage conditions are already favorable, preventing the harmful voltage spike that would otherwise prevent proper operation
Solution Approach 2:
The patent implements dynamics by using a microprocessor-controlled system that dynamically adjusts the timing and sequencing of SCR gate signals based on real-time voltage conditions. The system monitors capacitor voltages and dynamically determines when to activate each SCR, transforming the static latching behavior into a dynamically controlled process
2Power
If SCR switches are triggered simultaneously in parallel output terminals, then high voltage energy delivery is achieved, but voltage potential exceeds control circuit operating voltage
Solution Approach 1:
The patent uses preliminary action by first charging the capacitors to the required voltage levels before initiating SCR activation. The control system prepares the circuit conditions in advance, ensuring that when SCRs are activated, the voltage distribution is already controlled and will not exceed safe levels
Solution Approach 2:
The patent introduces a microprocessor-based control system as an intermediary that mediates between the high voltage power stage and the control circuitry. This intermediary monitors voltage conditions and intelligently sequences SCR activation, preventing harmful voltage spikes while enabling effective power delivery
3Productivity
If one SCR switch turns ON before the other in parallel output terminals, then voltage potential is created across the cathode of the un-triggered SCR, but the control circuit cannot generate enough voltage to drive current into the gate
Solution Approach 1:
The patent implements feedback by using the microprocessor to continuously monitor capacitor voltages and SCR states. Based on this feedback, the control system dynamically adjusts the timing of gate signals to ensure proper sequencing. The system detects when voltage conditions are favorable and responds by activating the appropriate SCR at the optimal moment
Solution Approach 2:
The control system performs preliminary assessment of voltage conditions before initiating SCR activation. By pre-evaluating the electrical state of the circuit, the system ensures that SCRs are activated only when voltage conditions support reliable operation, preventing activation failures
Data Source
AI summary
A high voltage switching and control circuit is provided for an implantable medical device (IMD). The circuit includes a high voltage positive (HVP) node, configured to receive a positive high voltage signal from a high energy storage source, and a high voltage negative (HVN) node, configured to receive a negative high voltage signal from a high energy storage source. Additionally, the circuit includes first, second and third output terminals that are configured to be connected to electrodes for delivering high voltage energy. First and second SCR switches are connected to the first and second output terminals, respectively. The first and second SCR switches are connected in series with one another and are connected to one of the HVP and HVN nodes. The first and second SCR switches have gating terminals. A control circuit is connected to the gating terminals and delivers first and second gating signals to turn ON the first and second SCR switches, respectively. The control circuit temporally offsets the first and second gating signals to turn ON the first and second SCR switches in a serial delayed manner.