Here is the first of three short tech nuggets (courtesy of Rich Nowakowski, TI) before our “Ask the experts” session on Wednesday, July 23 at 1:00 p.m. ET (10:00 a.m. PT). Hopefully these brief blogs will help stir your curiosity and questions, which you can post on our chat site here either before the session or during the session.
When designing with DC/DC converters, power supply designers face the compromise between small size and high efficiency. Hopefully, one is more important than the other in the application. Considering the trade-off is important. With advancements in MOSFET and process technology and shorter controllable minimum on-times, the envelope continues to be pushed. Here is an excerpt from an article that discusses the affects switching frequency has on the transient response of a DC/DC converter with 48V input and 5V output.
Transient response is a good indicator of the performance level of a power supply. In this example, a Bode plot of each power supply was taken to show a comparison at higher switching frequencies (see Figure 1). As shown, the phase margin of each power supply is between 45o and 55o , indicating a well dampened transient response. The crossover frequency is approximately one-eighth of the switching frequency. When using a fast switching DC/DC converter, the designer should make sure the power IC’s error amplifier has enough bandwidth to support a high crossover frequency. The unity gain bandwidth of the error amplifier, in this case the TPS54160, is typically 2.7 MHz. The actual transient-response times are shown in Table 1 with the associated values for voltage peak overshoot. The overshoot value is significantly lower with the higher switching frequency, due to the wider bandwidth.
Will improvements to increase switching frequencies affect pre-conceived notions on how DC/DC converters are chosen or used?