Surge Voltage Detection Circuit for Power Transistors
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Solution Overview
Problem
High-speed switching in power transistors generates surge voltages due to parasitic inductance, which are difficult to detect because of their high voltage and short duration, potentially damaging gate insulating films and causing circuit ringing.
Innovation Solution
A surge voltage detection circuit comprising a first capacitor, a first diode, a second capacitor, a sample and hold circuit, a switch, and a second diode, which accumulates and detects the surge voltage, and includes a controller to discharge the accumulated charge, allowing for frequent measurement and minimizing disruption to the power conversion device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed switching operation is performed in power transistors, then switching speed is improved, but surge voltage is generated due to parasitic inductance
Solution Approach 1:
A detection circuit is introduced as an intermediary between the power transistor and measurement equipment. This circuit includes a capacitor that couples to the power transistor's electrode, a voltage divider circuit that scales down the high surge voltage to a measurable level, and a sample-and-hold circuit that captures and holds the voltage waveform. This intermediary system enables safe measurement of surge voltage without directly exposing measurement equipment to high voltage while maintaining the ability to detect high-speed switching effects.
Solution Approach 2:
The patent replaces direct electrical measurement of surge voltage with an indirect measurement system using capacitive coupling and voltage division. Instead of directly connecting measurement equipment to the high-voltage node, the system uses a capacitor to transfer charge and a voltage divider to scale the signal, substituting a mechanical-like charge transfer process for direct electrical measurement.
2Speed
If surge voltage is generated, then switching performance is improved, but gate insulating film is destroyed or circuit ringing occurs
Solution Approach 1:
The detection circuit provides feedback information about surge voltage characteristics (peak value, waveform shape, duration) to enable monitoring and analysis of switching events. This feedback mechanism allows for assessing whether surge voltage levels are within safe limits for the gate insulating film, enabling preventive measures to be taken before damage occurs.
3Ease of operation
If conventional measurement methods are used, then measurement simplicity is maintained, but surge voltage cannot be detected due to high voltage and short duration
Solution Approach 1:
The patent transforms the measurement parameters by using a capacitor to integrate the high-voltage, short-duration surge signal into a measurable voltage level across the capacitor. The voltage divider circuit further transforms the voltage parameter to a safe measurement range. The sample-and-hold circuit transforms the time parameter by extending the measurement window through holding the captured voltage level, making it possible to measure nanosecond-scale events with standard equipment.
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
Effectively detects and measures surge voltages in power transistors, preventing damage to gate insulating films and improving the reliability of power conversion devices by accurately capturing peak surge voltages and discharging accumulated charge.
Implementation Method 1
a first capacitor (112) having a first end and a first other end, the first end being electrically connected to a first electrode and a second electrode of a power transistor
Implementation Method 2
a first diode (114) having a first anode and a first cathode, the first anode being electrically connected to the first other end of the first capacitor (112)
Implementation Method 3
a second capacitor (118) having a second end and a second other end, the second end being electrically connected to the first cathode of the first diode (114)
Data Source
AI summary
A semiconductor device according to an embodiment includes: a first capacitor having a first end and a first the other end, the first end for electrically connecting to at least one of a first electrode and a second electrode of a transistor having the first electrode, the second electrode, and a gate electrode; a first diode having a first anode and a first cathode, the first anode electrically connected to the first the other end; a second capacitor having a second end and a second the other end, the second end electrically connected to the first cathode; a sample and hold circuit electrically connected to the first cathode and the second end; a switch electrically connected in parallel with the second capacitor between the second end and the second the other end; and a second diode having a second anode and a second cathode, the second cathode electrically connected to the first the other end and the first anode.