Yuan Sheng Da analysis smart phone is how to achieve PD fast charge

In many electronic products as long as the use of lithium battery, then will face a battery life problem, especially in smart phones is more obvious, now on the market in the sale of smart phones without exception all support fast charge, but each fast charge agreement is not the same, let's take a look at the nextUSB-IFThe organization's" PDQuick chargeHow does it work?

Fast charge thisUSB PD The communication of the protocol layer is made up of messages 24MHZ the FSK The signal is coupled to VBUS Up or down VBUS Upper acquisition FSK Signal to realize the phone and charger communication process.

in USB PD In the correspondence, is will 24MHz the FSK pass cAC-Coupling The coupling capacitance is coupled to VBUS On the DC level, while in order to make 24MHz the FSK wrong PowerSupply or USBHost the VBUS The DC voltage has an effect and is added simultaneously in the loop zIsolation The inductance is filtered out by a low pass filter FSK The signal. Both phone and charger supportPDAs an example, the explanation is as follows:

1,USBOTG the PHY monitor VBUS Voltage, if any VBUS the 5V Voltage is present and detected OTGID Foot is 1K Pull-down resistors (not OTGHost The pattern,OTGHost modal ID The resistance is less than 1K ), it means that the cable is supported USBPD Of;

2,USBOTG Do normal BCSV1.2 The standard charger detects and starts USBPD Device policy manager, policy manager monitor VBUS Whether the DC level is coupled FSK Signal, and decode the message to say yes CapabilitiesSource Information, based on USBPD The specification parses the message USBPD A list of all voltages and currents supported by the charger;

3The mobile phone is configured according to the user CapabilitiesSource Select a voltage and current pair in the message and add the voltage and current pair to Request informational payload Then the policy manager will FSK Signal coupling to VBUS On DC level;

4, charger decoding FSK Signal and send Accept Message to the phone while adjusting PowerSupply The DC voltage and current output;

5Receive by mobile phone Accept Message, adjust ChargerIC The charging voltage and current;

6The phone can be dynamically sent during charging Request Message to request the charger to change the output voltage and current, so as to achieve a fast charging process.

If you also want to know more about the different meanings of fast charge information, welcome to consultYuan Shengda, you can also consult online/Leave a message and communicate directly with customer service.