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The Challenge

To prevent damage to the amplifiers, there must be no voltages at the output of the amplifiers that are greater than the positive supply voltage or less than the negative supply voltage of the amplifiers. The peripherals connected to the 4-quadrant power amplifiers can not always ensure this requirement.

Our Solution

Therefore the new Over Voltage Protection (OVP) monitors the voltages at the amplifier outputs. If a voltage level that is dangerous for the amplifiers sets in, than the OVP generates a short circuit at the amplifier outputs via two silicon diodes. In order to be able to react to very fast events, the switch-off process already starts after 200 ns, after an overvoltage has been detected by the OVP. The voltage is then limited to about 1.5 ... 2 V at the amplifier outputs. The short-term current peak may reach (with any polarity) for a time of 10 ms to 2,000 A. At the same time, the amplifiers are switched off and their outputs are electrically isolated from the connection contacts.

For amplifiers with variable-voltage power supplies, the implemented software automatically adjusts the switching thresholds to the voltages set in the amplifiers. Via a galvanically isolated switching output (with semiconductor contact), which signals the response of the OVP, it is possible to switch off the connected peripherals within a few milliseconds. For example, if a power supply unit implemented in the periphery provides for the excessively high voltage at the amplifier outputs, the power supply can be switched off in a defined manner via its control input.

The OVP is automatically reset to its initial state after tripping when the current drops below 10 ... 150 mA. Depending on the power consumed, it requires a short cooling time and is fully operational shortly afterwards.