12 CHARGING TECHNOLOGY www.analog.com Issue 3 2023 Power Electronics Europe www.power-mag.com Prototype a power bank charger without hardware headaches Is it possible to prototype a power bank charger application without building dedicated hardware? Diarmuid Carey, Staff Applications Engineer, Central Applications, Analog Devices The short answer to this question is yes. This article will review the process involved in developing an application using existing evaluation boards, discuss the challenges encountered and outline some recommendations for further revisions and improvements. Ideally, any power supply design should start with some basic proof of concept tests, which often involve testing an existing demo board. This demo simply takes this pre-existing step (of testing single rails on the demo hardware) and expands on it to produce a working system using demo hardware. As this demo was needed within a relatively short time frame, the typical development process of design, layout, build, assemble, and test (plus any design iteration) was not possible, so the system was prototyped in its entirety using nothing but readily available hardware. Application It was necessary to choose a high level application as a starting point to prove it is possible to prototype a power bank charger application without building dedicated hardware. This led to the power bank charging application being selected as a proof of concept. As power management is a prerequisite for every electronic project, any other application could have been selected. A power bank charger is a common application, which most consumers have encountered and used. For example, many travellers carry one to ensure their phone remains charged over a long journey. A power bank is essentially a battery pack (capacity varies depending on the price and range required), with one or more USB-A ports as well as a USB-C input port to charge it. It is possible of course to layer additional complexity on top of this basic functionality. For example, the addition of a wireless charging pad or an input to allow solar charging of the bank for outdoor enthusiasts. For this application, the option to charge the battery via solar or to charge via a DC input from a standard 12V AC/DC wall wart was included. The outputs included some basic USB-A charging ports (two in total), producing 5V for use with mobile phones and a range of USB-powered electronics. Hardware selection In this example, the design will support two input power sources (a solar panel and an AC/DC wall wart, which is just a simple AC/DC power supply). For this reason, a clever device called a power path prioritiser is required not only to intelligently switch between the available sources depending on which was available but also to manage the situation where they both were available by assigning priority to one source or the other. A simple version of this implementation can be achieved by using some simple diodes, commonly connecting the two cathodes of the diodes and connecting the anodes to their respective sources. Unfortunately, this particular configuration is lossy due to the diode drop inherent in a typical diode (approximately 0.6V), but it also doesn’t allow for any clever selection criteria to be Table 1: Modes of Operation from the LTC4416 datasheet !V' %67284:3>'_3F7' ,+P%@@QU',+P%@@QV' U' Z' /38F'A<82:>=' !>8BC7F' !>8BC7F' U' ?7>A7' WU':A'C7AA'4<8>'WV' !>8BC7F' ?7>A7' Z' WU':A'=278472'4<8>' WV' !>8BC7F' Z' R' (<8>>7C'U'F:A8BC7F'' 03'>34'EA7' 0:A8BC7F' R' U' (<8>>7C'V'F:A8BC7F' 03'>34'EA7' 0:A8BC7F' Z' U' #34<'9<8>>7CA' F:A8BC7F' 0:A8BC7F' 0:A8BC7F' Figure 1: An LTC4416 typical application circuit.
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