Area of Safe Operation Measurement for Switching Devices

At the transient state (On to Off / Off to On) of a power device the current draw becomes large due to the high voltage level. As the voltage and current levels increase so does the device's internal temperature which can result in the device malfunctioning or failing altogether. Every power device has its own area of safe operation (ASO) specification.
Engineers must measure the ASO of inverters and/or switching power supplies to ensure proper operation. To measure the ASO you must capture the transient state of the power device. To observe the ASO, engineers usually apply a load to the output of the inverter or switching power supply while varying the load. Due to the time required to vary the load, the ASO measurement device must have a long record length. For this reason long memory Digital Oscilloscopes are used.

Tm Appli Power01 1

Solutions
The Yokogawa Model DL7440/DL7480 2GSPS/500MHz/16MW Digital Oscilloscope provides the following solutions for this application :

  1. X-Y Display Function To Get ASO Drawing
  2. As a example, if you measure ASO of a switching transistor, you can set Ic as Y and Vce as X. Then, you can get the ASO.
  3. Provide the X-Y Display By Specified Interval
  4. Set the interval by two cursors to get the ASO of a specified transient state area.
  5. Maximum 16MW Long Record Length Will Capture All Data While Varying The Load
  6. Calculating the X-Y for all acquired data will help you to understand the trend and to easy get the ASO at each transient state with a specified interval X-Y.

Tm Appli Power01 2
The figure above is an example of an ASO measurement by using the DL7400's X-Y Display Function. This example is showing the ASO trend using the total data.

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