The Clipper CLP1500V15A1 Measurement Probe

The Clipper is a 2013 development from Springburo GmbH. It has been designed as a compact piece of test equipment to measure the on-time switching performance of a high voltage power transistor (FET or IGBT).  

To measure the ON voltage across a switching power transistor is a difficult task. The main problem is the large dynamic range of the input signal. We would like to measure with reasonable accuracy the ON voltages from say 50mV to 500mV, in the presense of switching voltages of many 100s of volts. This causes either a resolution problem, when the Oscilloscope is set to 100V/Div, or Oscilloscope input amplifier overload, when set to 200mV per Division. In this case, distortion and offset of the measured signal can occur, making the measured voltage unusable.

As transistor technology develops (eg GaN and SiC), the RdsON is reducing. This means the ON voltages are also reducing, with the OFF voltages increasing. Also, the power densities in these devices is increasing significantly, with the components getting smaller. It is becoming more important to be able to visualize the power dissipation in the transistor to guarantee the SOA (safe operating area), and to measure the thermal management (Heatsink) design.

The Clipper is a test device which allows the design or reliability engineer to visualize what is happening dynamically inside the Power Transistor.

Functional Description

Although the transistor device may be switching up to 1500V, the Clipper removes the high voltage component by "clipping" the output to either 2V (low range) or 12V (high range).  The test Oscilloscope can then be set to the corresponding max scale (eg 1V or 15V), and the "ON" voltage over the transistor can be seen at a resolution of eg 200mV or 3V per Division.

This effectively provides a method to measure the switching current without the need for sense resistors or current sensing coils.  Simply solder the 2 terminals to the Drain and Source of the Device under Test.

The input is via a standard SMC connector, and the output to an Oscilloscope is via a standard BNC connector.  Some adapters are supplied with the Clipper as shown below:

 The adapter parts supplied are shown below in more detail:

 Everything is packed in a protected aluminium case, with ESD foam as shown below: