PATENT DOCUMENT

Publication Number: US-9825481-B2
Application Number: US-201213648131-A
Country: US
Kind Code: B2

Title: Bleeder circuitry for increasing leakage current during hiccup modes of power adapters

Abstract:
The disclosed embodiments provide a system that facilitates operation of a power adapter in hiccup mode. The system includes a bleeding mechanism that reduces a hiccup time of the hiccup mode by increasing a leakage current of the power adapter. The system also includes an activation mechanism that activates the bleeding mechanism upon detecting a voltage drop associated with the hiccup mode.

Claims:
What is claimed is: 
     
       1. A system for facilitating operation of a power adapter in hiccup mode, comprising:
 an electronic device configured to be coupled to the power adapter, wherein the electronic device comprises:
 a bleeding circuit configured to reduce a duration of the hiccup mode by selectively increasing a leakage current associated with the power adapter, wherein the bleeding circuit comprises a first resistor and a second resistor; and 
 an activation circuit configured to activate at least one of the first and second resistors upon detecting a voltage drop associated with the hiccup mode, wherein the activation circuit comprises a first switching device configured to activate the first resistor when the first switching device is turned on, and a second switching device configured to activate the second resistor when the second switching device is turned on. 
 
 
     
     
       2. The system of  claim 1 , wherein the voltage drop is detected using a diode and a capacitor. 
     
     
       3. The system of  claim 2 , wherein the at least one switching device comprises one or more field-effect transistors (FETs) coupled to the diode and the capacitor. 
     
     
       4. The system of  claim 1 , wherein the first resistor controls turn on timing of the first switching device and the second switching device when the bleeding circuit is activated. 
     
     
       5. The system of  claim 1 , further comprising a connector configured to couple the power adapter to the electronic device, wherein the connector comprises a light indicating a state of charging of the electronic device. 
     
     
       6. The system of  claim 1 , wherein the hiccup mode is associated with low power consumption by the electronic device. 
     
     
       7. A method for facilitating operation of a power adapter in hiccup mode, wherein the power adapter is connected to an electronic device and comprises a bleeding circuit and an activation circuit, the method comprising:
 using the activation circuit to activate the bleeding circuit in the electronic device upon detecting a voltage drop associated with the hiccup mode, the bleeding circuit thereby reducing a duration of the hiccup mode by selectively increasing a leakage current associated with the power adapter; 
 wherein the bleeding circuit comprises a first resistor and a second resistor, and 
 wherein the activation circuit comprises a first switching device configured to activate the first resistor when the first switching device is turned on, and a second switching device configured to activate the second resistor when the second switching device is turned on. 
 
     
     
       8. The method of  claim 7 , wherein the voltage drop is detected using a diode and a capacitor. 
     
     
       9. The method of  claim 8 , wherein the bleeding circuit is activated using one or more field-effect transistors (FETs) coupled to the diode and the capacitor. 
     
     
       10. The method of  claim 7 , wherein the first resistor controls turn on timing of the first switching device and the second switching device when the bleeding circuit is activated. 
     
     
       11. The method of  claim 7 , wherein the power adapter is connected to the electronic device via a connector, wherein the connector comprises a light indicating a state of charging of the electronic device. 
     
     
       12. The method of  claim 7 , wherein the hiccup mode is associated with low power consumption by the electronic device. 
     
     
       13. The method of  claim 11 , wherein the reduced duration of the hiccup mode prevents visible flickering of the light. 
     
     
       14. An electronic device, comprising:
 a bleeding circuit comprising first and second resistors configured to reduce a duration of a hiccup mode in a power adapter connected to the electronic device by selectively increasing a leakage current associated with the power adapter; and 
 an activation circuit comprising first and second switching devices configured to activate the first and second resistors upon detecting a voltage drop associated with the hiccup mode; 
 wherein the first resistor controls turn on timing of the first switching device and the second switching device when the bleeding circuit is activated. 
 
     
     
       15. The electronic device of  claim 14 , wherein the voltage drop is detected using a diode and a capacitor. 
     
     
       16. The electronic device of  claim 15 , wherein the first and second switching devices are coupled to the diode and the capacitor. 
     
     
       17. The electronic device of  claim 14 , wherein the first switching device is configured to activate the first resistor when the first switching device is turned on and the second switching device is configured to activate the second resistor when the second switching device is turned on. 
     
     
       18. The electronic device of  claim 14 , wherein the hiccup mode is associated with low power consumption by the electronic device. 
     
     
       19. The electronic device of  claim 14 , wherein the electronic device is further configured to be connected to the power adapter via a connector, wherein the connector comprises a light indicating a state of charging of the electronic device.

Description:
RELATED APPLICATION 
     This application hereby claims priority under 35 U.S.C. §119 to U.S. Provisional Application No. 61/656,932, entitled “Circuitry to Reduce the Hiccup Time Without Increasing the Loss,” by Kisun Lee, Baratkumar K. Patel, Abby Cherian, filed 7 Jun. 2012. 
    
    
     BACKGROUND 
     Field 
     The disclosed embodiments relate to techniques for facilitating the operation of power adapters in hiccup mode. More specifically, the disclosed embodiments relate to bleeder circuitry for increasing leakage current during hiccup modes of power adapters. 
     Related Art 
     Rechargeable batteries are presently used to provide power to a wide variety of portable electronic devices, including laptop computers, tablet computers, mobile phones, personal digital assistants (PDAs), digital music players, and cordless power tools. The most commonly used type of rechargeable battery is a lithium battery, which can include a lithium-ion or a lithium-polymer battery. 
     During operation, a portable electronic device may be connected to a power adapter that converts alternating current (AC) mains electricity into direct current (DC) and/or a voltage compatible with the battery and/or components of the portable electronic device. Power from the power adapter may then be used to charge the battery and/or supply power to components in the portable electronic device. In the absence of the power adapter and/or mains electricity, the portable electronic device may be powered by the battery until the battery is fully discharged. 
     To prevent no-load power consumption by the power adapter, the power adapter may switch off if the portable electronic device is disconnected from the power adapter. Before switching off, the power adapter may use a hiccup mode to detect if the portable electronic device is connected to the power adapter or not. For example, the power adapter may operate in hiccup mode whenever the portable electronic device draws a small amount of power, such as when the portable electronic device is in a sleep mode and the battery of the portable electronic device is fully charged. 
     During the hiccup mode, the power adapter may periodically open a switch that disconnects the power adapter from mains electricity and monitor the subsequent voltage drop in the power adapter&#39;s voltage. If the voltage drops quickly, the power adapter may determine that the portable electronic device is connected to the power adapter and continue supplying power to the portable electronic device. If the voltage drops slowly, the power adapter may determine that the portable electronic device is not connected to the power adapter and switch off to prevent components in the power adapter from unnecessarily drawing mains electricity while the power adapter is not being used to supply power to the portable electronic device. 
     However, the hiccup mode may interfere with the operation and/or use of other components associated with the portable electronic device and/or power adapter. For example, the portable electronic device may be connected to the power adapter using a MagSafe (MagSafe™ is a registered trademark of Apple Inc.) connector that includes a set of light-emitting diodes (LEDs) indicating the charging and/or fully charged state of the portable electronic device. During the hiccup mode, the LEDs may turn off after the voltage in the power adapter drops below a pre-specified threshold. If the hiccup time of the hiccup mode extends past a certain point, the LEDs may flicker visibly, which may negatively impact the user experience with the portable electronic device. 
     Hence, what is needed is a mechanism for reducing hiccup times of hiccup modes in power adapters. 
     SUMMARY 
     The disclosed embodiments provide a system that facilitates operation of a power adapter in hiccup mode. The system includes a bleeding mechanism that reduces a hiccup time of the hiccup mode by increasing a leakage current of the power adapter. The system also includes an activation mechanism that activates the bleeding mechanism upon detecting a voltage drop associated with the hiccup mode. 
     In some embodiments, the voltage drop is detected using a diode and a capacitor. 
     In some embodiments, the bleeding mechanism is activated using one or more field-effect transistors (FETs) coupled to the diode and the capacitor. 
     In some embodiments, the bleeding mechanism is further activated using a resistor connected to the capacitor. 
     In some embodiments, the bleeding mechanism comprises a resistor. 
     In some embodiments, the activation mechanism and the bleeding mechanism are associated with a computer system connected to the power adapter. 
     In some embodiments, the hiccup mode is associated with low power consumption on the computer system. 
     In some embodiments, the reduced hiccup time prevents visible flickering of a light-emitting diode (LED) connected to the power adapter. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows the use of a power adapter in accordance with the disclosed embodiments. 
         FIG. 2  shows a set of voltages associated with the operation of a power adapter in hiccup mode over time in accordance with the disclosed embodiments. 
         FIG. 3  shows bleeder circuitry for increasing leakage current during a hiccup mode of a power adapter in accordance with the disclosed embodiments. 
         FIG. 4  shows a system for facilitating operation of a power adapter in accordance with the disclosed embodiments. 
         FIG. 5  shows a flowchart illustrating the process of facilitating operation of a power adapter in hiccup mode in accordance with the disclosed embodiments. 
     
    
    
     In the figures, like reference numerals refer to the same figure elements. 
     DETAILED DESCRIPTION 
     The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. 
     The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing code and/or data now known or later developed. 
     The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium. 
     Furthermore, methods and processes described herein can be included in hardware modules or apparatus. These modules or apparatus may include, but are not limited to, an application-specific integrated circuit (ASIC) chip, a field-programmable gate array (FPGA), a dedicated or shared processor that executes a particular software module or a piece of code at a particular time, and/or other programmable-logic devices now known or later developed. When the hardware modules or apparatus are activated, they perform the methods and processes included within them. 
     The disclosed embodiments provide a method and system for facilitating use of a power adapter. As shown in  FIG. 1 , a computer system  102  may be connected to an external power adapter  104  that converts alternating current (AC) mains electricity into direct current (DC) and/or a voltage that can be used to charge a battery of computer system  102  and/or operate components in computer system  102 . For example, computer system  102  may be a personal computer, laptop computer, tablet computer, mobile phone, portable media player, and/or other type of battery-powered electronic device that is connected to power adapter  104  using a Universal Serial Bus (USB) connector, MagSafe (MagSafe™ is a registered trademark of Apple Inc.) connector, and/or other type of power connector. 
     To reduce and/or prevent no-load power consumption by power adapter  104 , power adapter  104  may switch off upon detecting that computer system  102  is disconnected from power adapter  104 . Before switching off, power adapter  104  may use a hiccup mode to verify the connection or disconnection of computer system  102 . For example, power adapter  104  may operate in hiccup mode whenever computer system  102  consumes a relatively low amount of power, such as when computer system  102  is in a sleep mode. 
     During the hiccup mode, power adapter  104  may periodically open a switch and monitor the subsequent voltage drop in power adapter  104  caused by leakage current associated with power adapter  104 . If the voltage drops quickly (e.g., if the leakage current is high), power adapter  104  may determine that computer system  102  is connected to power adapter  104  and continue supplying power to computer system  102 . If the voltage drops slowly (e.g., if the leakage current is low), power adapter  104  may determine that computer system  102  is not connected to power adapter  104  and switch off. 
     However, the hiccup mode may interfere with the operation and/or use of other components associated with the portable electronic device and/or power adapter. For example, the hiccup mode may cause a light-emitting diode (LED)  106  in the connector (e.g., a MagSafe connector) to turn off after the voltage in the power adapter drops below a pre-specified threshold. If the hiccup time of the hiccup mode extends past a certain point, the off-state of LED  106  may be visible to a user and negatively impact the user&#39;s experience with computer system  102 . 
     More specifically,  FIG. 2  shows a set of voltages associated with the operation of a power adapter (e.g., power adapter  104  of  FIG. 1 ) in hiccup mode over time  206  in accordance with the disclosed embodiments. As shown in  FIG. 2 , an adapter voltage  204  of the power adapter and a switch voltage  202  of a switch in the power adapter may initially be relatively constant over time  206 . For example, adapter voltage  204  and switch voltage  202  may stay at a high level while the switch is closed and the power adapter is connected to mains electricity and/or another voltage source. 
     Once time  206  reaches t 1 , the switch may be opened, effectively disconnecting the power adapter from mains electricity and/or another voltage source. Adapter voltage  204  may then begin to drop from leakage current caused by components connected to the power adapter. As a result, adapter voltage  204  may drop relatively quickly if a computer system (e.g., computer system  102  of  FIG. 1 ) is connected to the power adapter and relatively slowly if the computer system is disconnected from the power adapter. 
     At time t 2 , adapter voltage  204  may fall below a threshold  208  that turns off an LED (e.g., LED  106  of  FIG. 1 ) connected to the power adapter. An off period  212  for the LED may then continue until time  206  reaches t 3 , when adapter voltage  204  reaches another threshold  210 . In addition, a hiccup time  214  between t 1  and t 3  may be used to determine the connection of the computer system to the power adapter. For example, if adapter voltage  204  reaches threshold  210  within a pre-specified period (e.g., 300 ms), the power adapter may detect that the computer system is connected to the power adapter. In turn, the switch may be closed, and both switch voltage  202  and adapter voltage  204  may return to the constant levels seen before t 1 . The power adapter may then repeat the hiccup mode periodically to verify that the computer system is still connected to the power adapter and/or detect a disconnection of the computer system from the power adapter. 
     Conversely, if adapter voltage  204  does not reach threshold  210  within the pre-specified period, the power adapter may detect that the computer system has been disconnected from the power adapter. The power adapter may then be switched off, causing the LED to remain off. In turn, adapter voltage  204  may continue to decrease until adapter voltage  204  reaches 0 and/or the computer system is reconnected to the power adapter. 
     Those skilled in the art will appreciate that the LED may alternate between an on-state and an off-state as the switch is opened and closed during the hiccup mode. Moreover, such toggling of the LED may cause visible flickering in the LED if hiccup time  214  and/or off period  212  are extended past a certain point. For example, hiccup time  214  and/or off period  212  may be extended if the leakage current of the computer system is reduced to increase the efficiency of the computer system. Moreover, techniques for averting such flickering by decreasing hiccup time  214  without increasing the leakage current, such as modifying an output capacitor to produce a larger voltage drop with the same leakage current, may result in increased electromagnetic interference (EMI) with other components of the computer system. 
     In one or more embodiments, hiccup time  214  is reduced by increasing the leakage current of the computer system during only the hiccup mode. To selectively increase the leakage current during the hiccup mode, the voltage drop in adapter voltage  204  may be detected, and a bleeding mechanism may be activated to increase the leakage current during the hiccup mode. 
     As shown in  FIG. 3 , bleeder circuitry for increasing the leakage current during the hiccup mode may include a diode  302 , a capacitor  304 , a p-channel field-effect transistor (PFET)  306 , an n-channel FET (NFET)  308 , and two resistors  310 - 312 . While the power adapter is connected to mains electricity and/or another power source (e.g., while the switch is closed), diode  302  conducts, and adapter voltage (“V adapter ”) from the power adapter may charge capacitor  304 , allowing the voltage of capacitor  304  to follow the adapter voltage. In addition, both FETs  306 - 308  may be turned off, and the leakage current of the computer system is not increased. 
     However, when the adapter voltage decreases (e.g., when the switch is open), the voltage across capacitor  304  becomes higher than the adapter voltage, and FET  306  turns on, increasing the gating voltage of FET  308  until FET  308  also turns on. In addition, resistor  310  may regulate the discharging of capacitor  304  and, in turn, the timing between the on times of FETs  306 - 308 . Once FET  308  conducts, resistor  312  causes the leakage current to increase, thus “bleeding” the adapter voltage. Bleeding of the adapter voltage may also be caused by resistor  310 , but resistor  312  may be selected to be significantly smaller than resistor  310  and thus affect the leakage current much more than resistor  310 . 
     After capacitor  304  has discharged to the same level as the adapter voltage, FETs  306 - 308  may turn off and stop bleeding of the adapter voltage. As with the on times of FETs  306 - 308 , the off times of FET  306 - 308  may be based on resistor  310 . Once the power adapter is reconnected to the voltage source, the increase in adapter voltage may cause diode  302  to conduct and charge capacitor  304 , returning the bleeder circuitry to the state before disconnection of the power adapter from the voltage source. 
     The bleeder circuitry may additionally be added to and/or utilize existing circuitry in the computer system. As shown in  FIG. 4 , a power adapter  412  may include a switch  408  that is controlled by a processor  402  (e.g., a microprocessor). Processor  402  may also monitor the adapter voltage (“V adapter ”) of power adapter  412  during a hiccup mode of power adapter  412 . For example, processor  402  may use the hiccup mode to detect if a computer system  418  is connected to power adapter  412  via a connector  416  and a cable  414  during low-power states of computer system  418  (e.g., a sleep mode). 
     On computer system  418 , one or more components of the bleeder circuitry of  FIG. 3  may be added to circuitry associated with a charger  406  and/or a charger integrated circuit (IC)  404  that process electricity from power adapter  412  into a form that is compatible with components and/or a battery of computer system  418 . More specifically, FETs  306 - 308  and resistors  310 - 312  may be added to existing circuitry on computer system  418  that includes diode  302  and capacitor  304 . For example, FETs  306 - 308  may be packaged together into the same IC, and the packaged IC and two resistors  310 - 312  may be added to the existing layout of computer system  418  to implement the bleeder circuitry. 
     As mentioned above, the bleeder circuitry may reduce the hiccup time of the hiccup mode by increasing the leakage current of power adapter  412 . For example, the bleeder circuitry may increase the leakage current after switch  408  is opened by processor  402 , causing the adapter voltage to drop at a faster rate than if computer system  418  did not include the bleeder circuitry. The faster voltage drop may cause processor  402  to close switch  408  before an off-state of an LED  410  in connector  416  can be observed by a user, thus preventing visible flickering of LED  410 . 
       FIG. 5  shows a flowchart illustrating the process of facilitating operation of a power adapter in hiccup mode in accordance with the disclosed embodiments. In one or more embodiments, one or more of the steps may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIG. 5  should not be construed as limiting the scope of the technique. 
     First, a bleeding mechanism is activated upon detecting a voltage drop associated with the hiccup mode (operation  502 ). The voltage drop may be initiated after a switch in the power adapter is opened. In addition, the voltage drop may be detected using a diode and/or a capacitor, and the bleeding mechanism may be activated using one or more FETs coupled to the diode and/or capacitor. 
     Next, the bleeding mechanism is used to reduce a hiccup time of the hiccup mode by increasing a leakage current of the power adapter (operation  504 ). The bleeding mechanism may include one or more resistors that “bleed” the adapter voltage from the power adapter, causing the leakage current to increase during the hiccup mode. For example, the bleeding mechanism may be used to prevent visible flickering of an LED connected to the power adapter that is caused by a longer hiccup time of the hiccup mode. The bleeding mechanism may then be deactivated once the power adapter exits the hiccup mode and/or before the end of the hiccup mode to prevent the increased leakage current from decreasing the efficiency of the computer system while the power is supplied to the computer system from the power adapter. 
     The foregoing descriptions of various embodiments have been presented only for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention.

Metadata:
Filing Date: 20121009
Publication Date: 20171121
Grant Date: 20171121
Priority Date: 20120607
Inventors: LEE KISUN
PATEL BHARAT K.
CHERIAN ABBY
Assignee: APPLE INC
CPC Classifications: [{"code": "Y02B70/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M3/337", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M2001/0032", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/022", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M3/335", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J9/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T307/858", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M1/0032", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/0032", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02B70/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02B70/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M3/335", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J9/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J9/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 48539406