Switching Element Thermal Load Reduction via Periodic Drive Control
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Solution Overview
Problem
Electronic fuses face thermal loading issues during the switching on of capacitive loads, leading to rapid temperature increases and potential damage to switching elements, which reduces their lifetime and triggers additional protection devices unnecessarily.
Innovation Solution
A method where the switching element is driven by a drive signal with a predefined period consisting of switched-on and switched-off durations, with a temporal profile of output voltage, current, and temperature monitored to adjust these durations to limit temperature increases within a permissible range, thereby reducing thermal loading and extending the switching element's lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the switching element is fully turned on during switching on of a capacitive load, then the load can be energized quickly, but the inrush current causes rapid temperature increase and thermal damage to the switching element
Solution Approach 1:
The patent applies periodic action by implementing a drive signal with a predefined drive period that includes alternating switched-on and switched-off durations. The switching element is not continuously on but is periodically switched on for a limited duration and then switched off, allowing the capacitive load to charge in stages. This periodic switching pattern limits the inrush current and prevents rapid temperature increase while still achieving load energization, directly resolving the contradiction between switching speed and temperature control.
2Temperature
If the switching element is operated in linear operation to limit inrush current, then thermal loading is reduced, but the switching element requires higher power rating and increases cost
Solution Approach 1:
The patent applies dynamics by making the switching element's operating state variable rather than fixed. The drive signal dynamically adjusts the switched-on duration within the drive period based on the charging state of the capacitive load and temperature conditions. This dynamic control allows the switching element to operate in a controlled manner that limits thermal loading without requiring a permanently oversized component, thereby reducing cost while maintaining temperature control.
Solution Approach 2:
The patent applies parameter changes by modifying the drive signal parameters (switched-on duration, drive period) based on the operating conditions. The control device adjusts these parameters to optimize the balance between limiting inrush current and maintaining efficient operation. This allows the use of a switching element with appropriate power rating rather than requiring an oversized component, reducing cost while controlling temperature.
3Loss of energy
If the switched-on duration is extended to reduce switching losses, then efficiency improves, but the temperature increase per cycle increases and may exceed permissible limits
Solution Approach 1:
The patent applies continuity of useful action by maintaining a repetitive drive signal with continuous cycles of switched-on and switched-off durations. Rather than using isolated pulses, the switching element operates in continuous periodic cycles that steadily charge the capacitive load while distributing thermal loading over time. This continuous operation reduces switching losses compared to intermittent pulsing while the controlled duty cycle ensures temperature increase per cycle remains within permissible limits.
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 approach effectively limits temperature increases to a fraction of the maximum permissible value, distributing energy loss efficiently and reducing mechanical stress, thus extending the lifetime of the switching element and minimizing the triggering of additional protection devices.
Implementation Method 1
the switching element is connected up such that it is used, e.g., as a controlled current source, i.e., with the use of a transistor (e.g., MOS-FET) as switching element, the transistor is operated in 'linear operation'
Implementation Method 2
such inrush currents can still reach values which, e.g., within a few milliseconds or shorter, can result in a very rapid increase in the temperature of the switching element
Data Source
AI summary
A method for reducing a thermal load on a switching element of an electronic fuse when switching on a load, wherein (a) a switching element is activated, (b) the switching element is deactivated and (c) the switching element is re-activated after reaching a set value of a switch-off duration, where steps (b) and (c) are repeated until an output voltage reaches a value that falls below a specified difference with respect to an input voltage of an electronic fuse or an output current reaches a specified duration current, where set values of a switch-on duration and/or switch-off current and the switch-off duration are maintained until new set values have been determined based on the output voltage, output current, and/or temperature, a pulse duty factor between the switch-on duration and the switch-off duration is adapted, and the specified maximum allowable temperature increase of the switching element is further observed.