Learn more about ripple voltage, ripple current, and how to test for switching regulator performance.
Take a closer look at how to improve the performance of switching regulators by looking at different output capacitor technologies in this video from KEMET. To explore this topic, the focus of this video is on output ripple voltage. Output ripple voltage is the voltage fluctuations that you see riding on the top of a DC voltage signal. This is caused by the ESR capacitor and a fluctuating current flowing out of the conductor.
To begin, the TI LM2121-2, also called the TILM2, is considered to demonstrate and investigate ripple voltage. The TI evaluation board is the reference port and the LM2 is a synchronous buck regulator featuring an input voltage range from 2.95 V to 5.5 V. The regulator is capable of delivering 12 amps of continuous output current, as well as a variable switching frequency between 300 KHz and 1.55 MHz. It’s also available in a small outline package, making it easy to hand solder. These features allow for exploration of different power scenarios instead of using a fixed-voltage or fixed-frequency switching regulator. However, the TI evaluation board is hard to use as it has limited capacitor space, and no on/off switch, power status LED, or variable frequency control. To properly investigate the performance of a switching regulator a new board was created, the KAIC-RCE-001, a two-layer FR-4 PCB. This board offers everything the TI evaluation board doesn’t, allowing for the opportunity to look at ripple current evaluation.
Ripple current is looked at as it’s the post-stating current output you see from a switching regulator. The ripple current going through the ESR of a capacitor, creates fluctuations in the voltage, which is called ripple voltage. In this evaluation, four different capacitor technologies are tested: ceramic, AO-Cap, KO-Cap, and aluminum electrolytic. To learn more about this evaluation and to see the testing in action video, watch this short video from KEMET.