Our customer would like to charge small device with small battery capacity. For example, 100mA is enough to charge the battery in CC mode.
What is the minimum power (current) which can be transferred without terminating power transmission?
Is there any specified minimum power in WPC specification?
The bq51013 does NOT have a min power termination; the device could operate at a low or no load current. We do have options for terminating the device at low current using an external circuit or future spin of the device.
Bill Johns, Applications Engineer
bqTESLA Wireless Power Products
Texas Instruments Inc
Thank you for your feedback.
I learned that bqTESLA TX controls transmission power by shifting switching frequency. (ie. maximum power transmission at resonance frequency and reduced power transmission by increasing switching frequency.)
But, it is impossible to reduce the transmission power down to 0W only by increasing switching frequency. So, I guess bqTESLA TX controls both of switching frequency and primary coil voltage/current to reduce transmission power down to 0W.
Is this correct understanding?
The transmitter will change switching frequency to adjust power, freq range is 110kHz to 205kHz. Power transfer will increase at low freq closer to 110kHz and decrease at higher freq closer to 205kHz. Also the transmitter will use PWM at light load to further control the power transfer.
BUT this is the voltage applied (rectified voltage or V-RECT) to the bq51013 LDO. The voltage out is a regulated 5V. The bq51013 will monitor output current and this information is used to adjust the transmitter operating point to set receiver V-RECT at the set point.
Information the RX uses to control the transmitter operating point is output current and V-RECT. The V-RECT set point will change with load at light load it is about 7V and full load it is about 5.2V.
Primary coil voltage or input voltage is fixed at 19V +/- 1V.
Do you know resonance frequency, inductance, parasitic capacitance and wire guage of the coil in this transmitter?
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