To design a stable input filter for a switching converter, measuring input impedance is crucial. Picotest’s J2121A High Power Line Injector simplifies this by using a VNA (like the Bode 100 or Bode 500) to modulate input voltage and measure current. This method enables precise calculation of input impedance, crucial for maintaining stability.
Picotest Products for measuring Converter Input Impedance
- J2121A High Power Line Injector: Supports PSRR, input impedance, and DC biased inductor testing.
- Bode 100 and 500 VNAs: Ideal for accurate impedance measurement and analysis.
The J2121A can handle up to 400V and 20A at 1MHz, making it perfect for high-power applications. Using the included calibration fixture, the setup ensures accurate measurements, even for demanding conditions.
Converter Input Impedance Test Set-up
- Setup: Connect the J2121A between the input source and converter.
- Calibration: Use the 1-ohm fixture for through calibration to correct for current monitor scaling.
- Measurement: The VNA will display the input impedance by dividing the input voltage at the converter by the current from the J2121A.
Conclusion
Measuring the input impedance of a switching converter is vital for designing a stable input filter and countering negative input resistance.
The combination of the J2121A High Power Line Injector and a VNA like the Bode 100 or Bode 500 provides a comprehensive solution for these measurements. With its ability to handle high voltages and currents, the J2121A is well-suited for high-power applications, ensuring accurate and reliable impedance analysis.
This setup is especially beneficial for high-power scenarios, such as military and satellite systems, ensuring robust filter design by addressing the negative input resistance characteristic of switching converters.
