New and Old Articles Address Power-Control Challenges

Two articles in the May 2009 issue of Power Electronics Technology magazine got my attention.First, “The Secret Mixed-Signal Life of PWM Peripherals,” looks closely at how to better use pulse-width modulators in microcontrollers. Many designs use a “bare” PWM output to control an external device simply by changing the on-off period to a driver circuit under software control. Keith Curtis, a technical staff engineer at Microchip Technology, explains how to include a few analog components in a control loop to handle some external signal-manipulation functions. Sometimes, the upper pulse-frequency limit of an MCU’s PWM output limit some types of control. The analog components help overcome this barrier. (This article is not a pitch for Microchip products.)

Curtis provides several useful examples in which external analog components enhance the operation of power circuits. Although these examples do not specifically aim to solve motor-control problems, they provide food for thought. Here’s the link to the complete article: powerelectronics.com/power_management/secret_mixedsignal_life_pwm_peripherals_0509. You must click back and forth between the article and each of the six diagrams. The printer-compatible version of the online article also lacks diagrams within the text.

A second article, “P-Channel Power MOSFETs Approach N-Channel Performance,” in the same issue offers information about two families of P-channel power MOSFETs developed by Ixys, the author’s employer. This information looks interesting and possibly useful in motor-control circuits. But this article got my attention for a different reason: Power Electronics Technology published a slightly revised version of the October 2008 Ixys application note, “IXYS P-channel Power MOSFETs and Applications,” IXAN0064 without a reference to its original source. Odd.

Unfortunately, the article/application note doesn’t list any Ixys part numbers–the only thing you can use to search for information on the Ixys Web site. So, that makes it difficult to get more information about the “Polar” and “TrenchP” P-channel MOSFETs from Ixys. But wait… Ixys ran a full-page advertisement for its power MOSFETs one page after the article/application note referred to above, so you might yet find some product information. You’ll have to find a paper copy of the paper magazine to see the ad, though. –Jon Titus