Power Semiconductor Switch Control Device for Half-Bridge Dead Time
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Solution Overview
Problem
In power electronics, maintaining a short 'dead time' for power semiconductor switches in a half-bridge circuit is challenging due to high switching off speed, which results in high current variation and potential damage from electrical voltages generated by stray inductances, especially when using low resistance switching off resistors.
Innovation Solution
A control device for power semiconductor switches incorporates a switching off acceleration circuit with a diode, resistor, and capacitor in parallel with the switching off resistor, along with a gate series resistor and actuating gate series resistor, to manage the discharge of the gate-emitter capacitance and reduce switching off speed, ensuring a shorter dead time without excessive current variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a low resistance switching off resistor is used to rapidly discharge the gate-emitter capacitance, then the dead time is reduced, but the switching off speed increases causing high current variation and electrical voltages that can damage the power semiconductor switch
Solution Approach 1:
The discharge path for the gate-emitter capacitance is segmented into two parallel paths: one through the switching off resistor and another through the switching off acceleration circuit (comprising diode, resistor, and capacitor). This segmentation allows the discharge current to be divided, enabling rapid discharge while limiting the peak current and reducing the harmful voltage spikes caused by stray inductances.
Solution Approach 2:
The switching off acceleration circuit acts as an intermediary element between the actuating device and the gate-emitter capacitance. It provides a controlled discharge path that mediates between the need for rapid discharge (to reduce dead time) and the need to limit current variation (to prevent damage), thereby resolving the contradiction through intermediate control.
2Speed
If the switching off speed is increased to maintain short dead time, then the time interval for switching off is reduced, but the rate of current variation increases generating high electrical voltages
Solution Approach 1:
The switching off acceleration circuit introduces dynamic behavior to the discharge process. The capacitor in the acceleration circuit charges and discharges dynamically, providing a time-varying discharge path that initially allows fast discharge to achieve short dead time, then gradually limits the current variation rate to prevent excessive voltage generation, thus dynamically balancing the contradictory requirements.
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 solution effectively reduces the switching off speed of power semiconductor switches, minimizing current variation and electrical voltages, thereby preventing damage and allowing for a shorter dead time in half-bridge circuits.
Implementation Method 1
a capacitor (13) which is electrically connected in parallel to said resistor (12), wherein the cathode of the diode (11) is connected to a second electrical terminal of the capacitor (13) in an electrically conductive manner, and a first electrical terminal of the capacitor (13) is connected to a first electrical terminal of the switching off resistor (10), which is electrically oriented towards the actuating device (3), in an electrically conductive manner
Implementation Method 2
a diode (11), an electrical resistor (12), and a capacitor (13) which is electrically connected in parallel to said resistor (12), wherein the cathode of the diode (11) is connected to a second electrical terminal of the capacitor (13) in an electrically conductive manner
Data Source
AI summary
A control device for a power semiconductor switch, includes an actuating device, a first current path, a second current path, which connects the second output of the actuating device to a circuit node of the control device in an electrically conductive manner, wherein the second current path incorporates an electrical switching off resistor which is electrically connected in-circuit between a second output of the actuating device and the circuit node of the control device, a third current path, which connects the circuit node of the control device to a control device terminal of the control device in an electrically conductive manner, and an switching off acceleration circuit, which is electrically connected in parallel with the switching off resistor, comprising a diode, an electrical resistor, and a capacitor which is electrically connected in parallel with said resistor, wherein the cathode of the diode is connected to a second electrical terminal of the capacitor in an electrically conductive manner, and a first electrical terminal of the capacitor is connected to a first terminal of the switching off resistor, which is electrically oriented towards the actuating device in an electrically conductive manner, and the anode of the diode is connected to a second electrical terminal of the switching off resistor in an electrically conductive manner.