Datasheet

bq51013B
www.ti.com SLUSB62A –MARCH 2013–REVISED OCTOBER 2013
Using the bq5101xB as a Wireless Power Supply: (See Figure 3)
Figure 3 is the schematic of a system which uses the bq51013B as power supply while power multiplexing the
wired (adapter) port.
When the system shown in Figure 3 is placed on the charging pad, the receiver coil is inductively coupled to the
magnetic flux generated by the coil in the charging pad which consequently induces a voltage in the receiver coil.
The internal synchronous rectifier feeds this voltage to the RECT pin which has the filter capacitor C3.
The bq5101xB identifies and authenticates itself to the primary using the COM pins by switching on and off the
COM FETs and hence switching in and out C
COMM
. If the authentication is successful, the transmitter will remain
powered on. The bq5101xB measures the voltage at the RECT pin, calculates the difference between the actual
voltage and the desired voltage V
RECT-REG
, (threshold 1 at no load) and sends back error packets to the primary.
This process goes on until the input voltage settles at V
RECT-REG
. During a load transient, the dynamic rectifier
algorithm will set the targets specified by V
RECT-REG
thresholds 1, 2, 3, and 4. This algorithm is termed Dynamic
Rectifier Control and is used to enhance the transient response of the power supply.
During power-up, the LDO is held off until the V
RECT-REG
threshold 1 converges. The voltage control loop ensures
that the output voltage is maintained at V
OUT-REG
to power the system. The bq5101xB meanwhile continues to
monitor the input voltage, and maintains sending error packets to the primary every 250ms. If a large overshoot
occurs, the feedback to the primary speeds up to every 32ms in order to converge on an operating point in less
time.
Details of a Qi Wireless Power System and bq5101xB Power Transfer Flow Diagrams
The bq5101xB family integrates a fully compliant WPC v1.1 communication algorithm in order to streamline
receiver designs (no extra software development required). Other unique algorithms such has Dynamic Rectifier
Control are also integrated to provide best-in-class system performance. This section provides a high level
overview of these features by illustrating the wireless power transfer flow diagram from startup to active
operation.
During startup operation, the wireless power receiver must comply with proper handshaking to be granted a
power contract from the Tx. The Tx will initiate the hand shake by providing an extended digital ping. If an Rx is
present on the Tx surface, the Rx will then provide the signal strength, configuration and identification packets to
the Tx (see volume 1 of the WPC specification for details on each packet). These are the first three packets sent
to the Tx. The only exception is if there is a true shutdown condition on the EN1/EN2, AD, or TS-CTRL pins
where the Rx will shut down the Tx immediately. See Table 4 for details. Once the Tx has successfully received
the signal strength, configuration and identification packets, the Rx will be granted a power contract and is then
allowed to control the operating point of the power transfer. With the use of the bq5101xB Dynamic Rectifier
Control algorithm, the Rx will inform the Tx to adjust the rectifier voltage above 7 V prior to enabling the output
supply. This method enhances the transient performance during system startup. See Figure 27 for the startup
flow diagram details.
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