Low-Voltage Protection Switching With Dynamic IGBT Gate Boost
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Solution Overview
Problem
Existing low-voltage protective devices face issues with reduced service life due to heavy loading of IGBT circuits during short circuits, leading to thermal overload and increased power loss, and complex constructions with high loop inductance, which complicates current commutation.
Innovation Solution
A low-voltage protective device using a single power semiconductor component, such as an IGBT or MOSFET, with a control and driver unit that manages the gate voltage to prevent desaturation during overcurrents and short circuits, allowing for fast commutation and reduced thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single IGBT is used in the protective device, then the device complexity is reduced, but the IGBT becomes heavily loaded during short circuits leading to thermal overload and reduced service life
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gate-emitter voltage (Uge) of the IGBT beyond its rated value during short-circuit conditions. The control unit increases Uge to a higher level (e.g., from typical 15V to 25-30V or higher) to force the IGBT into deep saturation, thereby reducing collector-emitter voltage and preventing thermal overload. This temporary parameter change allows the single IGBT to handle short-circuit currents without damage, resolving the contradiction between simple construction and reliable operation.
2Power
If multiple IGBTs are connected in parallel to handle high short-circuit currents, then the current carrying capacity and thermal overload protection are improved, but the loop inductance increases leading to longer commutation times
Solution Approach 1:
The patent segments the current handling function between a mechanical bypass switch (for normal operation and short-circuit isolation) and a single IGBT circuit (for controlled current interruption). The bypass switch carries the bulk current during normal operation, while the IGBT handles only the commutation process. This segmentation allows the use of a single IGBT without requiring multiple parallel devices, thus maintaining low loop inductance and fast commutation speed while still achieving high current carrying capacity through the combined system.
3Speed
If the IGBT is constantly energized to be ready for short-circuit protection, then the response time to short circuits is reduced, but the power loss and thermal stress on the IGBT increase
Solution Approach 1:
The patent applies preliminary action by pre-charging the IGBT gate capacitor to the rated gate-emitter voltage before a short circuit occurs. When a short circuit is detected, the IGBT is already in a ready state with its gate charged, enabling immediate turn-on response. The control unit then dynamically adjusts the gate voltage to higher levels during the short-circuit event. This preliminary charging action reduces response time while avoiding continuous high-power dissipation, as the IGBT remains in its normal low-loss operating state between events.
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 device extends the service life of the power semiconductor by minimizing thermal stress and reducing loop inductance, enabling reliable switching of high currents with low power loss and faster commutation times.
Implementation Method 1
a control and driver unit (13) configured to drive the first semiconductor circuit arrangement (11) with a control voltage
Implementation Method 2
the bypass switch (8) is opened, thereby causing the current to commutate to the IGBT circuit via the low-voltage protective device
Data Source
Figure 1~2
Figure 3
AI summary
A low-voltage protective device (1), comprising a first semiconductor circuit arrangement (11) with a power semiconductor, a control and driver unit (13) to drive the first semiconductor circuit arrangement (11) with a control voltage, the control and driver unit (13) configure the first semiconductor circuit arrangement (11): - in a switching-on process for a switching-on time (30) with a first voltage value (31 ), which is a threshold control voltage, of the control voltage, and - increase the control voltage from the first voltage value (31) to a second voltage value (32), which is a peak control voltage, after the switching-on time (30), and - increase the control voltage to a third voltage value (33), which is greater than the peak control voltage, upon detection of a short-circuit current or an overcurrent in a first shut-down step (34), and to de-energize the first semiconductor circuit arrangement (11) in a second shut-down step (35).