Patent Publication Number: US-2021175745-A1

Title: Wireless power tx to tx conflict and protection

Description:
TECHNICAL FIELD 
     Embodiments of the present invention are related wireless transmission of power and, in particular, to avoiding Tx to Tx conflicts in wireless power systems. 
     DISCUSSION OF RELATED ART 
     Mobile devices, for example smart phones, tablets, wearables and other devices are increasingly using wireless power charging systems. In general, wireless power transfer involves a transmitter driving a transmit coil and a receiver with a receiver coil placed proximate to the transmit coil. The receiver coil receives the wireless power generated by the transmit coil and uses that received power to drive a load, for example to provide power to a battery charger. 
     There are multiple different standards currently in use for the wireless transfer of power. The most common standard for wireless transmission of power is the Wireless Power Consortium standard, the Qi Standard. Under the Wireless Power Consortium, the Qi specification, a magnetic induction coupling system is utilized to charge a single device that is coupled through the receiver coil circuit. In the Qi standard, the receiving device coil is placed in close proximity with the transmission coil while alternate or amended standards may allow the receiving device coil be placed near the transmitting coil, potentially along with other receiving coils that belong to other charging devices. 
     Typically, a wireless power system includes a transmitter coil that is driven to produce a time-varying magnetic field and a receiver coil, which can be part of a device such as a cell phone, PDA, computer, or other device, that is positioned relative to the transmitter coil to receive the power transmitted in the time-varying magnetic field. 
     However, these devices may have both transmit functions and receive functions. For example, a phone can be used to receive power and may also be used to transmit power to other devices. If two devices are brought into proximity and both are performing a transmit function, damaging conflicts may result. 
     Therefore, there is a need to develop better wireless power devices that do not result in transmit conflicts. 
     SUMMARY 
     According to some embodiments, a wireless power device is presented that avoids transmit conflicts for devices capable of receiving and transmitting wireless power. The wireless power device can include a rectifier circuit coupled to a coil; a transmit driver coupled to the rectifier circuit; a transmit detect circuit configured to detect receipt of transmitted wireless power at the coil; and a controller coupled to the transmit driver and the transmit detect circuit, the controller receiving a signal from the transmit detect circuit and providing an alert of the presence of the transmitted wireless power, the controller activating the transmit driver to transmit wireless power in absence of the signal. A method of operating a wireless power device to avoid transmit conflicts includes determining an operating mode of the wireless power device; and in a transmit mode determining presence of a transmit power, if transmit power is detected, providing an alert and proceeding to an off state, and if transmit power is not detected, activating a transmit driver to transmit wireless power. 
     These and other embodiments are discussed below with respect to the following figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates a wireless power transmission system. 
         FIG. 2  illustrates a wireless power device. 
         FIG. 3  illustrates a process for operation of the device as illustrated in  FIG. 2 . 
     
    
    
     These figures are further discussed below. 
     DETAILED DESCRIPTION 
     In the following description, specific details are set forth describing some embodiments of the present invention. It will be apparent, however, to one skilled in the art that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are meant to be illustrative but not limiting. One skilled in the art may realize other elements that, although not specifically described here, are within the scope and the spirit of this disclosure. 
     This description illustrates inventive aspects and embodiments should not be taken as limiting—the claims define the protected invention. Various changes may be made without departing from the spirit and scope of this description and the claims. In some instances, well-known structures and techniques have not been shown or described in detail in order not to obscure the invention. 
       FIG. 1  illustrates an example wireless power transmission system  100 . As illustrated in  FIG. 1 , a first device  102  is coupled to a coil  106  and a second device  104  is coupled to a coil  108 . In general, one of wireless device  102  and wireless device  104  is in a transmit mode and the opposite one in a receive mode. For example, if wireless device  102  is in a transmit mode and wireless device  104  is in a receive mode, then coil  106  is driven to produce a time varying magnetic field that in turn induces a current in coil  108 . Coil  108  is coupled to device  104 , which can receive the power transmitted through the time varying magnetic field from wireless device  102 . 
     Wireless device  102  and wireless device  104  can be any devices with wireless power functions. Many phones, laptops, tablets, and other devices include a wireless power function. In many cases, these devices can both receive and transmit wireless power. In some examples, one of device  102  and device  104  may be a transmit only device, such as in a stationary wireless power charger, and the opposite device may have a transmit mode and a receive mode. 
     In situations where both first device  102  and second device  104  are capable of transmitting wireless power, then a potential power conflict results when coils  106  and  108  are brought into contact with both devices  102  and  104  transmitting power. In this case, high current can be induced in both transmitting devices  102  and  104  and high voltages can result on the driver supply rails for both transmitting devices  102  and  104 . 
     Embodiments of the present invention include a detection mode that detects wireless power transmitted by another wireless device that is brought into proximity. If wireless power is detected, then a device that includes the embodiment is prevented from also transmitting wireless power. 
       FIG. 2  illustrates a wireless power device  200  according to some embodiments of the present invention. Wireless power device  200  can be either one of wireless device  102  or wireless device  104  as illustrated in  FIG. 1 . As is illustrated in  FIG. 2 , components of wireless power device  200  can be formed on an integrated circuit that can be coupled to a coil  202 . 
     Coil  202  can, in some embodiments, function as both a transmit coil and a receive coil. In some embodiments, coil  202  can be optimized to function as a transmit coil in a transmit mode and optimized to function as a receive coil in a receive coil and, as such, may include difference coil taps for transmit and receive. Coil  202  is coupled to a rectifier  208 . Rectifier  208  can function as a rectifier circuit to receive wireless power from coil  202  in a receive mode or as an inverter to drive wireless power through coil  202  in a transmit mode. As such, rectifier  208  can be a full-bridge rectifier formed by a four-transistor bridge coupled across the nodes AC 1  and AC 2 . 
     In a receive mode, RX driver  204  operates the transistors of rectifier  208  to receive a rectified DC signal from rectifier  208 . Rectifier  208  receives an alternating signal from coil  202 , which is configured to receive the transmitted wireless magnetic field. The DC signal from rectifier  208  can be provided to a DC circuit  206 , which in turn provides an output voltage VOUT. DC circuit  206  can, for example, include filtering and DC conversion circuitry to provide the output voltage VOUT at a particular voltage level or range of voltages. External circuitry can receive the voltage VOUT, which can be used to power circuitry and for charging batteries. 
     In a transmit mode, TX driver  212  receives an input voltage VIN and drives rectifier  208  to generate an alternating magnetic field through coil  202 , which is configured for transmission. In accordance with embodiments of the present invention, a TX detect circuit  214  detects the presence of transmitted wireless power energy at coil  202  and provides signals indicating the presence or absence of transmitted power. In some embodiments, TX detect circuit  214  can be configured to receive a signal from rectifier  208 , or directly from coil  202 , and indicates the presence of transmitted wireless power if the signal exceeds a threshold level. In some embodiments, the presence of transmitted power can be detected prior to activating TX driver  212  to transmit power. In some embodiments, TX detect circuit  214  monitors to detect the presence of transmitted power while TX driver  212  is activated to transmit power. In either case, in transmit mode, if wireless power is detected incoming in conflict with the operation of sending outbound power, TX detect circuit  214  provides signals to halt TX driver  212  from transmitting power and alerts to the presence of a transmitter power collision. 
     Detecting incoming power at coil  202  in TX detect  204  may be accomplished in many different ways. For example, a simple rectified level can be obtained using discrete diode and demodulation circuitry (e.g., circuitry intended for decoded messages from a valid receiver) connected to an analog-to-digital converter (ADC) can be used for voltage monitoring. The digital output can be received by control circuit  210 . An alternate method may include a frequency counter capable of detecting the incoming voltage or current received by coil  202  at the coil or AC inputs AC 1  and AC 2 . In this frequency detection case an additional protection mechanism may be to use the frequency of the incoming signal to identify the source of the incoming power (e.g. wireless power transmitter, random white noise, RFID, Bluetooth, NFC, etc.). In yet another method, TX detect  214  may include a DC current or voltage sensor capable of detecting voltage or current increases in the direction normally associated with receiving power opposed to the direction naturally occurring when transmitting power. In each of these example cases, a signal indicating that a Tx conflict exists can be generated at control circuit  210 . 
     As is further illustrated in  FIG. 2 , device  200  may include a control circuit  210 . Control circuit  210  is coupled to receive control signals with and receive signals from RX driver  204 , DC circuit  206 , TX driver  212 , TX detector  214 , and rectifier  208 . Control circuit  210  may include any circuitry that controls the operation of device  200 . In some embodiments, control circuit  210  may include a microcomputer or microprocessor with sufficient memory (both volatile and non-volatile) to execute instructions for performing functions described here. Control circuit  210 , in particular, receives signals from TX detect circuit  214 . As such, TX detect circuit  214  can indicate to control circuit  210  the presence of wireless power at coil  202 . In the presence of wireless power, control circuit  210  can instruct TX driver  212  to not transmit power and not provide a PING (which is often provided by a transmitting device in order to detect a receiving device) since the user has placed device  200  in the presence of a transmitting device. In addition, control circuit  210  can excerpt a TX collision signal indicating the presence of wireless transmission. Additionally, control circuit  210  can indicate to DC circuit  206  the presence of a wireless power transmission to prevent high incoming voltage from being provided to the VOUT signal. In these cases, control circuit  210  may activate internal or external circuits that can block the conflicting incoming energy from passing from rectifier  212  to RX driver  204  to prevent the conflicting incoming power to affect VOUT and subsequently affect other devices connected to VOUT. Those devices can then provide voltage and/or current protection. Control circuit  210  may also provide digital or analog signals, shown as TX Collision signal, to other devices indicating the event to allow for user notification of a conflict so that action may be taken by the user to correct the conflict. 
     In some examples, device  200  may be a transmit only device. In that case, receive driver  204  and DC circuit  206  may be absent and control circuit  210  only operates transmit functions. In general, device  200  can include both a receive function and a transmit function, determined by a device mode in control circuit  210 . The device mode may be determined by user input or a receive mode may be initiated when device  200  is placed in the presence of a transmitting device. 
     As is further illustrated in  FIG. 2 , control circuit  210  may be coupled to a user input  218 . User input  218  may further receive the TX Collision signal, which can alert a user to the presence of a transmit collision. User interface  218  may also be used so that a user can determine the mode of operation of device  200  (e.g. transmit mode, receive mode, or off). In some embodiments, device  200  may automatically enter receive mode in the presence of wireless power. 
       FIG. 3  illustrates a process  300  for operation of device  200  as illustrated in  FIG. 2 . In step  302  of process  300 , device  200  determines an operating mode for device  200 . In particular, device  200  may be in a receive mode RX, a transmit mode TX, or off. Device  200  may be in a receive mode RX when device is brought into proximity with a transmitting device. A user input may place device  200  in a transmit mode TX or place device  200  in an off mode (OFF) where the wireless power function is disabled. As discussed above, in some embodiments, device  200  may only include a transmit mode and an off mode. 
     In step  304 , process  300  decides, based on the determination of step  302 , the functional mode. If the functional mode is an OFF mode, process  300  proceeds to OFF state  310 . In state  310 , control circuit  210  prevents either of RX driver  204  or TX driver  212  from activating so that device  200  is neither transmitting or receiving wireless power. From the Off state  310 , process  300  may return to determination step  302  to determine whether the mode has changed. 
     If, in step  304 , a receive mode RX is determined, process  300  proceeds to step  306 . In step  306 , control circuit  210  activates RX driver  204  and DC circuit  206  to receive wireless power through coil  202 . From step  306 , process  300  may proceed to step  320 , where it is determined whether device  200  is finished receiving power (e.g., a battery charging by device  200  is fully charged). If not, then process  300  returns to step  306  to continue receiving wireless power. If finished, then process  300  proceeds to off state  310 . 
     If in step  304  a transmit mode TX is determined, process  300  proceeds to step  308 . In step  308 , control circuit  210  checks TX detect circuit  214  to determine if there is wireless power already present at coil  202 . As discussed above, TX detect circuit  214  can indicate the presence of wireless power if a signal from rectifier  208  exceeds a threshold signal. In step  312 , process  300  proceeds to step  314  if step  308  determines the presence of wireless power and step  316  if no wireless power is detected. In step  314 , a TX collision alert is provided and process  300  proceeds to OFF state  310 . 
     In the absence of wireless power, process  300  proceeds from step  312  to step  316 . In step  316 , control circuit  210  activates TX driver  212  to transmit wireless power through coil  202 . In some embodiments, process  300  may proceed to step  318 . In step  318 , process  300  determines whether or not wireless transmission is finished. This may be determined when the receiving device is removed, when the receiving device signals cessation of charging, or when a user changes the device operation mode. If finished, then process  318  can proceed to OFF state  310  and then to step  302 . If not finished, process  300  may proceed back to step  308  to monitor for the presence of wireless transmission. 
     Embodiments of the invention described herein are not intended to be limiting of the invention. One skilled in the art will recognize that numerous variations and modifications within the scope of the present invention are possible. Consequently, the present invention is set forth in the following claims.