(2017-11-19, 11:13 PM)tocan Wrote: https://youtu.be/m20o3P-S5s8
Although this works, it is not a very robust design:
- Since the capacitor is connected directly on the USB voltage, they are only 4.5 V when he initiates shutdown, and he looses 19 % of the energy.
- He has no boost regulator, so he looses even more energy.
- He does not have any current limit on the charging, which can lead to stress on the supply and the capacitor, reducing the lifetime of both. A simple resistor or a one transistor constant current source would be enough.
- USB power supplies have often 5.5 V to 6 V no-load voltage, and he does not have any over voltage protection.
- He has no voltage balancing, which will reduce the lifetime. An opamp can be used for this.