BQ51050B_16 Datasheet, PDF (13/43 Pages) Texas Instruments – High-Efficiency Qi v1.1-Compliant Wireless Power Receiver

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8 Detailed Description
bq51050B, bq51051B, bq51052B
SLUSB42E – JULY 2012 – REVISED MARCH 2015
8.1 Overview
8.1.1 A Brief Description of the Wireless System
A wireless system consists of a charging pad (primary, transmitter) and the secondary-side equipment. There are
coils in the charging pad and in the secondary equipment which magnetically couple to each other when the
equipment is placed on the charging pad. Power is transferred from the primary to the secondary by transformer
action between the coils. Control over the amount of power transferred is achieved by changing the frequency of
the primary drive.
The secondary can communicate with the primary by changing the load seen by the primary. This load variation
results in a change in the primary coil current, which is measured and interpreted by a processor in the charging
pad. The communication is digital - packets are transferred from the secondary to the primary. Differential bi-
phase encoding is used for the packets. The rate is 2-kbps.
Various types of communication packets have been defined. These include identification and authentication
packets, error packets, control packets, power usage packets, end of power packet and efficiency packets.
The primary coil is powered off most of the time. It wakes up occasionally to see if a secondary is present. If a
secondary authenticates itself to the primary, the primary remains powered up. The secondary maintains full
control over the power transfer using communication packets.
AC to DC
Power
Drivers
bq5105x
Voltage/
Rectification ^Current
Conditioning
Communication
System
Controller
V/I
Sense
bq500210
Transmitter
Controller
Battery
Charger
LI-Ion
Battery
Receiver
Figure 19. WPC Wireless Power Charging System Indicating the Functional Integration of the bq5105x
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