Patent Publication Number: US-2023163588-A1

Title: Input Power Control and Protection

Description:
BACKGROUND 
     Wearable products are typically physically small enclosures with elegant industrial design. The circuitry within such products often has voltage input limits. A typical voltage supplied by a USB type-A charging cable may be around 5V, which may be within the voltage input limits. Other USB Type C power sources, such as PD compliant Type-C however, may deliver up to 20V after negotiation, which may exceed the voltage input limits for the circuitry. Such excessive power delivery can result in damage to the circuitry and the wearable products. 
     BRIEF SUMMARY 
     The present disclosure provides for input voltage protection, without blockage of a power path. In particular, an AC signal is used to turn off a transistor coupled across a power path, such that the power does not pass through the transistor. Such transistor may also be turned off in response to receipt of a voltage exceeding a predetermined threshold. 
     One aspect of the disclosure provides a voltage protection circuit for an electronic device, comprising a control line coupled to a first transistor, an input power line, and a power interrupt transistor coupled across the input power line and electronically coupled to the first transistor, wherein receipt of a square wave signal at the first transistor through the control line causes the power interrupt transistor to turn off, thereby interrupting the flow of power on the input power line. 
     The voltage protection circuit may further comprise a capacitor coupled across junctions of the first transistor, wherein receipt of the square wave signal at the first transistor causes the capacitor to drain. The circuit may further comprise a second transistor coupled between the capacitor and the power interrupt transistor, wherein the second transistor turns on when the capacitor is drained. The power interrupt transistor turns off when the second transistor turns on. 
     According to some examples, the voltage protection circuit may further comprise a resistor coupled between the power line input and the second transistor, the resistor having an ohmic value based on voltage tolerance limits of the electronic device, wherein receipt of voltages exceeding a threshold trigger activation of the second transistor. 
     According to some examples, the control line may be coupled to a control unit and the square wave signal is received from the control unit in response to detection of an error. 
     Another aspect of the disclosure provides an electronic device, comprising an input port, electronic components, and a voltage protection circuit between the input port and the electronic components. The voltage protection circuit comprises a control line coupled to a first transistor, an input power line, a power interrupt transistor coupled across the input power line and electronically coupled to the first transistor, wherein receipt of a square wave signal at the first transistor through the control line causes the power interrupt transistor to turn off, thereby interrupting the flow of power on the input power line. 
     Yet another aspect of the disclosure provides a method of operating an electronic device, comprising receiving a voltage at a power line of the electronic device, the power line coupled between an input and circuitry of the electronic device, detecting, at a control unit, when an error condition exists, and transmitting, in response to detection of the error condition, a square wave signal through a control line to a first transistor, the square wave signal causing a power interrupt transistor to turn off, the power interrupt transistor blocking receipt of the voltage by the circuitry of the electronic device. Transmitting the square wave signal may cause a capacitor coupled across the first transistor to discharge. Discharging the capacitor may activate a second transistor, the activation of the second transistor causing the power interrupt transistor to turn off. 
     According to some examples, the control line remains steady when the error condition is not detected by the control unit. 
     According to some examples, the method may further comprise activating a second transistor when the received voltage exceeds a predetermined threshold. Even further, the method may comprise turning off the second transistor when the received voltage no longer exceeds the predetermined threshold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a functional block diagram illustrating an example system according to aspects of the disclosure. 
         FIG.  1 B  is an example pictorial diagram of the system of  FIG.  1 A . 
         FIG.  2    is an example circuit diagram according to aspects of the disclosure. 
         FIG.  3    is a flow diagram illustrating an example method according to aspects of the disclosure. 
         FIG.  4    is a flow diagram illustrating an example method according to aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes a system and method for protecting an electronic device from high voltages that may exceed tolerance limits for circuitry within the electronic device. A protection circuit blocks high voltages from the device components through gating techniques. Such gating techniques may similarly be used to control whether power is received by the electronic components when an error condition is detected by a control unit. 
     Example Systems 
       FIGS.  1 A- 1 B  illustrate an example of a power source  110  which supplies power to an electronic device  160 . For example, the power source  110  may supply power through a cable  150 , such as a charging cable. In some examples, the charging cable may be connected through an intermediate device, such as a charging brick  112  inserted into a wall outlet, a laptop or other computing device connected to a power source, etc. 
     The power source  110  may be, for example, a battery, an electrical outlet, a computing device, or any other type of device capable of delivering voltage to another device. 
     The cable  150  may be, for example, a USB cable or any other type of cable capable of delivering voltage from the power source  110  to the electronic device  160 . The cable may include any of a variety of types of connectors at either end, such as USB-A, USB-C, micro-USB, mini-USB, 8-pin lightning, etc. 
     The electronic device  160  may be any type of electronic device, including wearable devices such as earbuds  164 , a smartwatch, a headset, smartglasses, smart helmets, rings, pendants, clothing, etc., or non-wearable devices, such as phones, home assistant devices, displays, speakers, etc. According to some examples, the electronic device  160  may include a case  166 . For example, the case  166  may be used to house an electronic accessory, such as earbuds  164 , when the accessory is not in use. In addition, the case  166  may be used to deliver a charge to the accessory. For example, the accessory may include electrical contacts that establish an electrical connection with the case when the accessory is housed within the case. Moreover, the voltage supplied to the accessory from the power source  110  and through the charging cable  150  may be supplied through the case. For example, the case  166  may include an input for receiving the charging cable  150 , and may relay the charge received from the power source  110  to the earbuds  164 . According to some examples, the case  166  may include a battery, capacitor, or electronic components for storing a charge from the power source  110  for later use in charging the earbuds  164  when the earbuds  164  are housed within the case  166  but the charging cable  150  is no longer connected. While the example of  FIG.  1 B  illustrates earbuds within a case, it should be understood that the electronic device  160  may include any of a number of electronic devices, including wearable and non-wearable electronic devices. 
     The electronic device  160  may include one or more processors  130 , one or more memories  120 , as well as other components. For example, the electronic device  160  may include a battery  162 . 
     The memory  120  may store information accessible by the one or more processors  130 , including data  122  and instructions  128  that may be executed or otherwise used by the one or more processors  130 . For example, memory  120  may be of any type capable of storing information accessible by the processor(s), including a computing device-readable medium, or other medium that stores data that may be read with the aid of an electronic device, such as a volatile memory, non-volatile as well as other write-capable and read-only memories. By way of example only, memory  120  may be a static random-access memory (SRAM) configured to provide fast lookups. Systems and methods may include different combinations of the foregoing, whereby different portions of the instructions and data are stored on different types of media. 
     The data  122  may be retrieved, stored, or modified by the one or more processors  130  in accordance with the instructions  128 . Although the claimed subject matter is not limited by any particular data structure, the data may be stored in computing device registers, in a relational database as a table having a plurality of different fields and records, XML documents or flat files. The data may also be formatted in any computing device-readable format. 
     The instructions  128  may be any set of instructions to be executed directly (such as machine code) or indirectly (such as scripts) by the one or more processors  130 . For example, the instructions may be stored as computing device code on the computing device-readable medium. In that regard, the terms “instructions” and “programs” may be used interchangeably herein. The instructions may be stored in object code format for direct processing by the processor, or in any other computing device language including scripts or collections of independent source code modules that are interpreted on demand or compiled in advance. Functions, methods and routines of the instructions are explained in more detail below. 
     The one or more processors  130  may be microprocessors, logic circuitry (e.g., logic gates, flip-flops, etc.) hard-wired into the device  110  itself, or may be a dedicated application specific integrated circuit (ASIC). It should be understood that the one or more processors  130  are not limited to hard-wired logic circuitry, but may also include any commercially available processing unit, or any hardware-based processors, such as a field programmable gate array (FPGA). In some examples, the one or more processors  130  may include a state machine. 
     When instructions  128  are executed by the one or more processors  130 , the one or more processors may detect an error condition and activate a power control feature in response. For example, the power control feature may include transmitting a square wave signal through a control line to a first transistor, causing a capacitor coupled to the first transistor to drain, which in turn keeps second transistor on, subsequently prevents a third transistor from turning on, thereby blocking receipt of input voltage. 
       FIG.  2    provides an example block diagram illustrating electronic device  160  with power control circuit  200  positioned between a power input, such as a charging cable input port, and other device components  261 . As described below, gating components, such as transistors, in-between power  210  and the device components  261  can stop current flow when an input voltage is too high, thereby preventing damage to the device components  261 . 
     The circuit  200  includes a control line VBUS_C coupled to a micro control unit (MCU)  230 . As shown, the control line VBUS-C is coupled to a first transistor Q 101 , and a capacitor C 102  is coupled in parallel across junctions of the first transistor Q 101 . The capacitor C 102  is further coupled to second transistor Q 2  between input power line V_BUS and third transistor Q 1  gate. A third transistor Q 1  coupled to the second transistor Q 2  and the device components  261  interrupts input power line V_BUS and outputs modified input power line V_BUS_IN. 
     During normal operation, the input V_BUS line is at normal voltage of 5V. The D 4  Zener diode will not conduct, therefore Q 2  base is biased to V_BUS level by R 6  and R 7 , Q 2  is off. The VBUS_C line is at a steady level, no current can pass DC blocking capacitor C 101 , Q 101  gate is pulled to ground by R 101 , and Q 101  is off. Q 1  will not draw current from Q 2  base. Q 2  keeps being off, then Q 1  gate is pulled to ground by R 8 , Q 1  is on and supply current to Device  261 . 
     The MCU may monitor for and detect errors. For example, the MCU can detect a condition that will require powering down the circuit. MCU is monitoring the voltage on V_BUS, V_BUS_IN and several other nodes, and can generate an event to turn off power path. 
     When an error is detected, the MCU  230  sends a square wave to control line VBUS_C, for example, by sending an AC signal that toggles on and off repeatedly. In response, Q 101  toggles on at the positive edge and discharges capacitor C 102 , and keeps the node low. Second transistor Q 2  is turned on, and third transistor Q 1  is off. This AC control feature protects against error in the MCU at corner conditions, such as during booting, or when there is power brown out. If there were no C 101 , high level on control line VBUS_C may turn on first transistor Q 101 , keeping third transistor Q 1  in the “off” state and cutting power to system, thereby preventing the circuit from starting. 
     If a high voltage is received from the power source  210 , the high voltage will go through resistor R 6  and Zener diode D 4 . If the voltage is more than a predetermined threshold, such as more than 6.5V, the resistor R 6  will have voltage drop above a second threshold, such as more than 0.7 which will cause second transistor Q 2  to turn on, which in turn causes third transistor Q 1  to shut off. As a result, no power passes through the third transistor Q 1  or along modified input power line V_BUS_IN to the device components  261 . 
     The predetermined threshold voltage triggering second transistor Q 2  to turn on may be determined based on, for example, acceptable voltage limits for the device components  261 . This predetermined threshold voltage may be used to determine values for the resistor R 6 . For example, where the predetermined threshold voltage is 6.5V, the value of resistor R 6  may be 10 k ohms. However, if the predetermined threshold voltage were set to be higher or lower than 6.5V, the value of resistor R 6  may be correspondingly adjusted such that the resulting voltage drop would cause the second transistor Q 2  to turn on. 
     The MCU  230  may be an MCU or any other type of processing unit, for example, a System On Chip (SOC), an ASIC, or a FPGA/CPLD, etc. 
     The first transistor Q 101  as illustrated in the example of  FIG.  2    is a metal oxide semiconductor field effect transistor (MOSFET). In other examples, the first transistor Q 101  may be a field effect transistor (FET), bipolar junction transistor (BJT), or any other type of transistor. Similarly, while second transistor Q 2  is shown as a BJT and third transistor Q 1  is shown as a MOSFET, other types of transistors may be used in other examples. 
     Example Methods 
     In addition to the operations described in connection with the systems above, various operations will now be described in connection with example methods. It should be understood that the following operations do not have to be performed in the precise order described below. Rather, various operations can be handled in a different order or simultaneously, and operations may also be added or omitted. 
       FIG.  3    provides a flow diagram illustrating an example method  300  of operating an electronic device with an AC power control feature. 
     In block  310  it is determined whether an error is detected. For example, an MCU may determine whether an error condition exists. Examples of such error conditions include any condition that would require powering down the circuit. 
     If a failure is detected in block  310 , the MCU sends a square wave through a control line to a first transistor (block  320 ). The square wave causes a capacitor coupled across the transistor to discharge (block  330 ). As a result of the discharged capacitor, a second transistor coupled to the capacitor is turned on (block  340 ). This causes a third transistor, coupled to the second transistor and the input power line, to turn off (block  350 ). When the third transistor is off, it interrupts the flow of power across the input power line, thereby preventing the power from reaching other components of the electronic device. 
     If a failure is not detected at block  310 , the electronic device operates in a default operating state. In this default operating state, the control line from the MCU remain steady (block  325 ). As such, the first transistor remains off (block  335 ), the second transistor remains off, and the third transistor remains on, allowing the voltage received from the input to pass through the third transistor to the other components of the electronic device (block  345 ). 
       FIG.  4    provides a flow diagram illustrating an example method  400  of operating the electronic device. This method relates to handling excessive voltages received at the input, wherein the excessive voltages exceed a tolerance limit for circuitry in the electronic device. 
     In block  410 , the voltage is received at the input. If the voltage exceeds a first threshold (block  420 ), a resistor coupled to the input will have a voltage drop exceeding a second threshold (block  430 ). For example, the resistor may be selected to have an ohmic value based on the first threshold, such that a resulting voltage drop will exceed the second threshold when the received voltage exceeds the first threshold. 
     In block  440 , a second transistor coupled to the resistor is turned on as a result of the voltage drop exceeding the second threshold. In block  450 , the turning on of the second transistor causes a third transistor to turn off. As the third transistor interrupts a power line, such that first and second junctions of the third transistor are coupled to the power line between an input for the power and other circuitry, turning off the third transistor blocks receipt of voltage by the other circuitry. 
     If the voltage does not exceeds the threshold in block  420 , the electronic device operates in a default mode, wherein the third transistor outputs the voltage it receives from the input (block  425 ). 
     The foregoing systems and methods are advantageous in that they provide a mechanism for protection of a wearable device from high voltage input that could potentially damage components within the device. The protection operates without pins becoming stuck or the device becoming stuck in an off state. 
     While some of the foregoing examples are described in relation to a case delivering a reset to an accessory, such as a pair of earbuds, it should be understood that other examples of the system and method may include any of a number of other electronic devices. 
     Unless otherwise stated, the foregoing alternative examples are not mutually exclusive, but may be implemented in various combinations to achieve unique advantages. As these and other variations and combinations of the features discussed above can be utilized without departing from the subject matter defined by the claims, the foregoing description of the embodiments should be taken by way of illustration rather than by way of limitation of the subject matter defined by the claims. In addition, the provision of the examples described herein, as well as clauses phrased as “such as,” “including” and the like, should not be interpreted as limiting the subject matter of the claims to the specific examples; rather, the examples are intended to illustrate only one of many possible embodiments. Further, the same reference numbers in different drawings can identify the same or similar elements.