COMMUNICATION SLOTS IN A WIRELESS POWER SYSTEM
This disclosure provides systems, methods and apparatuses for a managing timing of communication slots in a wireless power system. The communication slots are centered on zero-cross instances. The Power Transmitter and/or Power Receiver can use a phase locked loop (PLL) to determine the timing of the zero-cross instances. The wireless power system can determine when to begin a communication slot based on the timing of the zero-cross instance and the slot width. For example, the beginning of the communication slot can begin at a time that is half the slot width before the time of the zero-cross instance.
1 . A method of a Power Transmitter, comprising:
generating a wireless power signal for transmission to a Power Receiver based on an alternating current (AC) main power signal; and
communicating with the Power Receiver during one or more communication slots, wherein the one or more communication slots are centered on one or more corresponding zero-cross instances based on a slot width of the one or more communication slots.
2 . The method of claim 1 , further comprising:
determining a timing of a future zero-cross instance of the AC main power signal;
calculating a start time for at least a first communication slot based on the timing of the future zero-cross instance and the slot width of the first communication slot such that approximately half of the slot width occurs before the future zero-cross instance; and
configuring a communication unit to begin the first communication slot at the start time.
3 . The method of claim 2 , wherein determining the timing of the future zero-cross instance includes:
calculating the timing of the future zero-cross instance based on an amount of time between a half cycle of the AC main power signal and a previous zero-cross instance.
4 . The method of claim 1 , further comprising:
locking onto a frequency of the AC main power signal using a phase locked loop (PLL), wherein a phase output of the PLL indicates a phase value that changes in relation to a phase of the AC main power signal; and
determining a timing of the one or more corresponding zero-cross instances based on an output of the PLL.
5 . The method of claim 4 , wherein determining the timing of the one or more corresponding zero-cross instances includes:
measuring a duration of at least a prior half cycle of the AC main power signal based on a period in which the phase output of the PLL changes from zero (0) to π radians or from π to 2π radians;
detecting an occurrence of a previous zero-cross instance when the output of the PLL is 0, π, or 2π radians; and
calculating the timing of the one or more corresponding zero-cross instances based on the duration of at least the prior half cycle and the occurrence of the previous zero-cross instance.
6 . The method of claim 1 , further comprising:
determining the slot width based on an amount and periodicity of information to communicate to the Power Receiver.
7 . The method of claim, wherein a duration of the first communication slot is not dependent on a voltage and frequency of the AC main power signal.
8 . A Power Transmitter comprising:
a driver circuit configured to generate a wireless power signal for transmission to a Power Receiver based on an alternating current (AC) main power signal; and
a communication unit configured to communicate with the Power Receiver during one or more communication slots, wherein the one or more communication slots are centered on one or more corresponding zero-cross instances based on a slot width of the one or more communication slots.
9 . The Power Transmitter of claim 8 , further comprising:
a controller configured to:
determine a timing of a future zero-cross instance of the AC main power signal;
calculate a start time for at least a first communication slot based on the timing of the future zero-cross instance and the slot width of the first communication slot such that approximately half of the slot width occurs before the future zero-cross instance; and
configure the communication unit to begin the first communication slot at the start time.
10 . The Power Transmitter of claim 9 , wherein the controller is configured to:
calculate the timing of the future zero-cross instance based on an amount of time between a half cycle of the AC main power signal and a previous zero-cross instance.
11 . The Power Transmitter of claim 8 , further comprising:
a phase locked loop (PLL) configured to lock onto a frequency of the AC main power signal, wherein a phase output of the PLL indicates a phase value that changes in relation to a phase of the AC main power signal, and wherein the controller is configured to determine a timing of the one or more corresponding zero-cross instances based on the phase output of the PLL.
12 . The Power Transmitter of claim 8 , wherein the controller is configured to:
measure a duration of at least a prior half cycle of the AC main power signal based on a period in which the output of the PLL changes from zero (0) to π radians or from π to 2π radians;
detect an occurrence of a previous zero-cross instance when the output of the PLL is 0, π, or 2π radians; and
calculate the timing of the one or more corresponding zero-cross instances based on the duration of at least the prior half cycle and the occurrence of the previous zero-cross instance.
13 . The Power Transmitter of claim 8 , wherein the controller is configured to determine the slot width based on an amount and periodicity of information to communicate to the Power Receiver.
14 . The Power Transmitter of claim 8 , wherein the slot width is not dependent on a voltage and frequency of the AC main power signal.