Apparatus and method for supporting changeable communication speed in wireless power transmission system

A method for transferring a wireless power, the method performed by a wireless power transmitter and comprising:

• receiving, from a wireless power receiver, a configuration packet including information for a negotiation phase;
• transmitting, to the wireless power receiver, an acknowledge (ACK) in response to the configuration packet,
• wherein the ACK has 512 cycles per a bit,
• entering the negotiation phase with the wireless power receiver,
• wherein, in the negotiation phase or a power transfer phase, a number of cycles per bit in an operating frequency for transferring the wireless power is changed from the 512 cycles,
• wherein, in the negotiation phase or the power transfer phase, each bit of data is aligned with n cycles;
• and
• wherein, in the negotiation phase or the power transfer phase, the operating frequency between differential bi-phases is changed based on a value of each bit during the n cycles.