OVERVOLTAGE PROTECTION CIRCUIT FOR A POWER SEMICONDUCTOR AND METHOD FOR PROTECTING A POWER SEMICONDUCTOR FROM OVER-VOLTAGES

摘要

The invention relates to an overvoltage protection circuit (5) and a method for protecting a power semiconductor (31, 32) from over-voltages. For this purpose, a voltage applied across a power semiconductor switch is first converted to a lower voltage signal corresponding to the voltage applied to the power semiconductor switch by means of a resistance voltage divider. The reduced voltage signal is then evaluated by means of an overvoltage detector, such as a Zener or suppression diode, and the power semiconductor switch to be protected is activated if the response voltage of said diode is exceeded. By lowering the voltage level by means of a voltage divider, a Zener or suppression diode having a lower voltage level can be used for monitoring the overvoltage, said Zener or suppression diode having improved operating properties in comparison with corresponding diodes having a higher voltage level.

主权项

1. An overvoltage protection circuit (5) for a power semiconductor switch (31, 32), comprising:
a first resistor (R1) which is disposed between a first terminal point (E) of the overvoltage protection circuit (5) and a node (K), a second resistor (R2) which is disposed between the node (K) and a second terminal point (A) of the overvoltage protection circuit (5), a semiconductor switch (Q2) comprising a control terminal, an input and an output, wherein the output is connected to the second terminal point (A) of the overvoltage protection circuit (5), and an overvoltage detector (22), which is configured to enter an at least partially electrically conductive state if a predefined voltage between two terminals of the overvoltage detector (Z2) is exceeded, wherein the overvoltage detector (Z2) is disposed in a current path between the node (K) and the control terminal of the semiconductor switch (Q2).