I've a huge amount of various development boards. These boards almost exclusively powered from USB. It is just happened that I've no powered USB hub (I even tried to buy one, but the one I was coosing, wont fit into my needs).
Some of the boards really require the 5V. If you measure the voltage on the USB - hubs, cables included, with a load of a high power dev board (like STM32F429-DISCOVERY), it could fall to 4V or even lower. It happend to not enough to this board. The application USB wasn't working.
It pop into my mind, what if I just put a switch mode boost converter into the USB power line, and allow the data lines to connect to the board?
It is a simple dongle put between two USB cables, no external supply needed and done.
I was thinking to build it with the common MC34063, because it is easy and cheap. Later I realized, that the result will not be cheap because the big external components (low switching frequency), and in addition it be big and inefficient. So I dropped it.
The project kept in this state for months.
A few weeks ago I was searching for a cheap boost converter for an other project. Suddenly I found Microchip MCP1642. It turned out, that it is not suitable to that project, but nicely fits into this.
So the story begin here...