Abi sabah alternatif bulacağım.
ben ciddiyim. otomatik switch lazım değil ki bize. Zaten harici 5V izole adaptörle kullanmak mantıklı. Harici adaptör takılınca host tarftan alınan USB gücü mekanik olarak kesilir.
Power Transmission
On the host side, the incoming 5V power is demultiplexed by the TPS2111A power mux chip.
When "DC IN" is connected, TPS2111A switches the board to use external DC power, otherwise, the board is powered from the USB port.
Immediately after the TPS2111A, the demultiplexed 5 V power is passed through an LC filter to prevent too much differential-mode noise from entering or leaving the USB port. Then, the filtered 5 V power is first sent to the ISOUSB211 ASIC, which creates 3.3 V local power via its internal LDO. Simultaneously, the 5 V power is also sent to a LMR10510 DC-DC converter to create the 1.8 V core voltage supply for ISOUSB211 (ISOUSB211 does have an internal LDO for 1.8 V as well, but LDO is too inefficient).
Finally, the 5 V power is also sent to an SIP isolated DC-DC converter module to derive an isolated 5 V rail at the secondary side, which then derives 3.3 V and 1.8 V just like how it's done at the primary side. When the 5 V power enters and leaves the DC-DC converter, it's filtered by common-mode chokes to reduce the common-mode noise across the isolation barrier.
The isolated converter module has a Functional Insulation rating, with a dielectric withstand voltage of 3000 VDC for 60 seconds. Note that this dielectric withstand voltage is a measure of immunity to transient voltages, and should not be confused with the rating working voltage. Also, the Functional Insulation means the converter has a low design margin and should be assumed to have no safety guarantees, thus this board design should not be used in safety-critical applications. The continuous operating voltage should stay within the Safety Extra-Low Voltage limit (42.4 VRMS, or 60 VDC).
Better isolated DC-DC converter modules with Reinforced Insulation exist, but those modules have limited suppliers and much more expensive. On the other hand, DC-DC converters in a SIP package are a de-facto standard in the industry with many options. Thus, as a tradeoff, a SIP converter is selected and the development board is designed for Functional Insulation. In addition, even when a DC-DC converter with Reinforced Insulation is used, the board is probably still unable to meet the standard of Reinforced Insulation anyway - Reinforced Insulation involves more than component selection - the whole board must be assumed to contain dangerous voltages and be covered by an insulated enclosure, which obviously is unsuitable for a development board. Thus, this is another reason for this compromise.