Sensing current utilizing MOSFET’s Rds(on) and Inductor’s DCR in different location discussed in this app note from Alpha and Omega semiconductor. Link here (PDF)
In current mode converters, current sense resistor can be placed in three locations: input loop, output loop and freewheeling loop. The pros and cons are discussed in details. The principles and features of peak current mode and valley current mode are also presented. The cautions and tips for using Rds(on) of high-side MOSFET, low-side MOSFET and DCR of the inductor as the current sense resistor are also mentioned at the end.
Application note from Alpha and Omega semiconductor on proper design of circuit and PCB layout to balance parallel MOSFETs. Link here (PDF)
This paper discusses issues involved in paralleling MOSFETs in high-power, high-frequency switching applications. It investigates root cause problems such as unbalanced voltage and current by taking a closer examination of PCB layouts and important circuit design parameters for driving paralleled MOSFETs
Nothing brings joy to a hacker’s heart like taking a cheap gizmo and making it useful. Over at Hackaday.io [AndyHull] popped open some cheap LiPo battery power packs to see if he could power a Canon Powershot camera. The entire shebang would be left in the wilderness for photography so keeping it inexpensive was a big goal since it might be destroyed or lost.
The power packs [Andy] looked at have a TP4221 controlling the charge cycle for up to four 18650 LiPo cells connected in parallel. The controller also boosts the voltage to 5 volts for one or two USB ports while providing automatic shutdown if the LiPo cell voltage drops below 3.2v. Below that voltage the cells can be damaged and might possibly cause a fire.
The packs [Andy] used also had a torch output to drive an LED almost directly from the cells. That output is a nominally 3.8 V at 100 mA which is just what he needed to power the Canon Powershot. It could be used to power small micros or other low power devices.
The LED was removed and replaced by a connection to outside the pack. The torch output is triggered by two quick presses on a switch that was also replaced with a connector to allow remote control.
If you’re looking for powerful battery options, give LiPo a try and have a look at [Andy]’s LiPo battery safety issues post, also on Hackaday.io. For a broader LiPo overview, see this obsessive rundown of various batteries.
Filed under: digital cameras hacks
Introduction to hearing aids app note (PDF!) from Maxim:
This application note introduces the styles of hearing aids, including behind the ear (BTE), in the ear (ITE), in the canal (ITC), and completely in the canal (CIC), as well as a brief summary of both analog and digital hearing aid technologies. Also discussed is the importance of the audio-processing path, the functions of electrical components, and some critical elements that designers must consider when selecting products.
This month’s ware is shown below:
And below are views of the TO-220 devices which are folded over in the top-down photo:
We continue this month with the campaign to get Nava Whiteford permission to buy a SEM. Thanks again to Nava for providing another interesting ware!
The ware for October 2015 was a Lecroy LT342L. Nava notes that it was actually manufactured by Iwatsu, but the ASICs on the inside all say LeCroy. Congrats to Carl Smith for nailing it, email me for your prize and happy Thanksgiving!