Switch Drive Circuit Surge Voltage Control
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Solution Overview
Problem
Existing drive circuits for switches fail to effectively reduce surge voltage when the switch is switched to an off state, particularly due to the correlation between the current flowing through the switch in the on state and the resulting surge voltage.
Innovation Solution
A drive circuit that includes an acquisition section to measure the surge-correlated value, such as inter-terminal voltage or time period from an on command to a determination voltage, and a setting section that adjusts the switching speed of the switch to a lower speed when the surge-correlated value is large, thereby reducing the surge voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switch is switched to an off state with high switching speed, then productivity is improved, but surge voltage increases
Solution Approach 1:
The patent applies dynamics by making the switching speed adjustable rather than fixed. The control section dynamically changes the switching speed based on real-time detection of surge-correlated values (inter-terminal voltage or time period). When surge-correlated values indicate high risk, the switching speed is reduced; when risk is low, normal switching speed is maintained. This dynamic adjustment resolves the contradiction between maintaining high productivity and reducing surge voltage.
Solution Approach 2:
The patent changes the parameter of switching speed based on detected surge-correlated values. The control section monitors parameters such as inter-terminal voltage or time period from on command to determination voltage, and adjusts the switching speed parameter accordingly. This parameter change strategy allows the system to optimize between productivity and surge voltage reduction by adapting the switching speed to actual operating conditions.
2Object-generated harmful factors
If the switching speed is reduced to lower surge voltage, then surge voltage is reduced, but productivity decreases
Solution Approach 1:
The patent changes the parameter of switching speed based on detected surge-correlated values. The control section monitors parameters such as inter-terminal voltage or time period from on command to determination voltage, and adjusts the switching speed parameter accordingly. This parameter change strategy allows the system to optimize between productivity and surge voltage reduction by adapting the switching speed to actual operating conditions.
Solution Approach 2:
The patent implements feedback by having the control section continuously detect surge-correlated values and adjust switching speed based on this feedback. The detection of inter-terminal voltage or time period provides feedback about the likelihood of surge voltage generation, and the control section uses this feedback to adjust the switching speed in real-time, creating a closed-loop control system that resolves the contradiction between surge voltage reduction and productivity maintenance.
3Reliability
If surge voltage is reduced by adjusting switching speed, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the control section to perform multiple functions: detecting surge-correlated values (inter-terminal voltage or time period), determining surge risk, and adjusting switching speed. This multi-functional approach consolidates what could be separate complex circuits into a single control unit, improving reliability through integrated surge voltage control while minimizing the increase in device complexity.
Solution Approach 2:
The control section serves itself by using its own detection capabilities to monitor surge-correlated values and automatically adjust switching speed without requiring external intervention. This self-service mechanism improves reliability by enabling autonomous surge voltage control while avoiding the complexity of external control systems.
Data Source
AI summary
A drive circuit Dr for a switch that reduces a surge voltage caused when a switch SW is switched to an off state. The drive circuit Dr detects, as an on voltage Von, a collector-emitter voltage of the switch SW while the switch SW is in an on state. When the detected on voltage Von is large, the drive circuit Dr sets a resistance value Rd of a discharging resistor 53 when the switch SW is switched to an off state to be larger than the resistance value Rd when the detected on voltage Von is small. More specifically, the drive circuit Dr sets the resistance value Rd to a larger value as the detected on voltage Von is increased.