PATENT DOCUMENT

Publication Number: US-9590519-B2
Application Number: US-201213570063-A
Country: US
Kind Code: B2

Title: Power adapter with a step-down transformer and a voltage step-up circuit

Abstract:
Embodiments of an adapter are disclosed that include a rectifier with an input and an output coupled to a step-down transformer with a primary coil and a secondary coil, wherein the primary coil is coupled to the output of the rectifier. A step-up converter is coupled to the secondary coil.

Claims:
What is claimed is: 
     
       1. An adapter, comprising:
 a rectifier with an input and an output; 
 a step-down transformer with a primary coil and a secondary coil, wherein the primary coil is coupled to the output of the rectifier, and wherein the secondary coil comprises a first end tap and a second end tap; 
 a first switch and a second switch, each of the first switch and the second switch having a first switch end and a second switch end, wherein: 
 the first switch end of the first switch is coupled to the first end tap and the second switch end of the first switch is coupled to ground, and 
 the first switch end of the second switch is coupled to the second end tap and the second switch end of the second switch is coupled to ground; and 
 a controller coupled to the first switch and the second switch; 
 wherein the controller is configured to control a primary positive voltage and a primary negative voltage across the primary coil, wherein the primary positive and negative voltages cause a secondary positive voltage and a secondary negative voltage across the secondary coil; and 
 wherein the controller is configured to alternate activating the first switch and the second switch by activating the first switch during the secondary positive voltage and activating the second switch during the secondary negative voltage based on the secondary positive and negative voltages across the secondary coil. 
 
     
     
       2. The adapter of  claim 1 , further including:
 a first diode with a first anode and a first cathode; and 
 a second diode with a second anode and a second cathode, wherein the secondary coil includes a center tap coupled to a ground, and wherein the first end tap is coupled to the first anode, the second end tap is coupled to the second anode, and wherein the first cathode is coupled to the second cathode and to an output node. 
 
     
     
       3. The adapter of  claim 2 , further including:
 an H-bridge, with an input and an output, wherein the H-bridge input is coupled to the rectifier output and the H-bridge output is coupled to the primary coil. 
 
     
     
       4. The adapter of  claim 2 , wherein a turns ratio of the primary coil to the secondary coil is in the range from 4:1 to 8:1. 
     
     
       5. The adapter of  claim 2 , further including:
 a capacitor coupled to a first end of the primary coil; and 
 a half H-bridge, with an input and an output, wherein the half H-bridge input is coupled to the rectifier output and the half H-bridge output is coupled to a second end of the primary coil. 
 
     
     
       6. The adapter of  claim 2 , wherein the controller is coupled to control inputs for the first switch and the second switch, wherein the controller is configured to control the voltage output on the output node using the first switch and the second switch. 
     
     
       7. The adapter of  claim 1 , further including:
 a capacitor coupled to an output node of the adapter, wherein a maximum voltage rating of the capacitor is less than or equal to a maximum input voltage rating of the adapter. 
 
     
     
       8. The adapter of  claim 1 , further including:
 a capacitor coupled to an output node of the adapter, wherein a maximum voltage rating of the capacitor is less than or equal to 50 volts. 
 
     
     
       9. An adapter, comprising:
 a step-down transformer with a primary coil and a secondary coil, wherein the secondary coil includes a center tap coupled to a ground, and a first end tap and a second end tap; 
 a first diode with a first anode and a first cathode, wherein the first anode is coupled to the first end tap; 
 a second diode with a second anode and a second cathode, wherein the second anode is coupled to the second end tap, and the first cathode is coupled to the second cathode; 
 a first switch and a second switch, wherein each of the first switch and the second switch has a first switch end and a second switch end, wherein the first switch end of the first switch is coupled to the first end tap and the second switch end of the first switch is coupled to ground, and the first switch end of the second switch is coupled to the second end tap and the second switch end of the second switch is coupled to ground; 
 a controller coupled to the first switch and the second switch; 
 wherein the controller is configured to control a primary positive voltage and a primary negative voltage across the primary coil, wherein the primary positive and negative voltages cause a secondary positive voltage and a secondary negative voltage across the secondary coil; and 
 wherein the controller is configured to alternate activating the first switch and the second switch by activating the first switch during the secondary positive voltage and activating the second switch during the secondary negative voltage based on the secondary positive and negative voltages across the secondary coil. 
 
     
     
       10. The adapter of  claim 9 ,
 wherein the controller is coupled to control inputs for the first switch and the second switch, 
 wherein the controller is configured to alternately close the first switch for a portion of a first duration of the secondary positive voltage and open the first switch for a remaining portion of the first duration to control a voltage output on an output node of the adapter, and 
 wherein the controller is configured to alternately close the second switch for a portion of a second duration of the secondary negative voltage and open the second switch for a remaining portion of the second duration to control the voltage output on the output node of the adapter. 
 
     
     
       11. The adapter of  claim 9 , wherein a turns ratio of the primary coil to the secondary coil is in the range from 4:1 to 8:1. 
     
     
       12. The adapter of  claim 9 , further including:
 a rectifier with an input and an output; and 
 an H-bridge with an input and an output, wherein the output of the rectifier is coupled to the input of the H-bridge and the output of the H-bridge is coupled to the primary coil. 
 
     
     
       13. The adapter of  claim 9 , further including:
 a rectifier with an input and an output; 
 a capacitor coupled to a first end of the primary coil; and 
 a half H-bridge with an input and an output, wherein the output of the rectifier is coupled to the input of the half H-bridge and the output of the half H-bridge is coupled to a second end of the primary coil. 
 
     
     
       14. The adapter of  claim 9 , further including:
 an output node coupled to the first cathode and the second cathode; 
 a capacitor coupled to the output node, wherein a maximum voltage rating of the capacitor is less than or equal to a maximum input voltage rating of the adapter. 
 
     
     
       15. The adapter of  claim 9 , further including:
 an output node coupled to the first cathode and the second cathode; 
 a capacitor coupled to the output node, wherein a maximum voltage rating of the capacitor is less than 50 volts. 
 
     
     
       16. A method for generating an output voltage in an adapter, comprising:
 receiving an alternating current voltage; 
 rectifying the alternating current voltage, thereby forming a rectified voltage; 
 applying the rectified voltage across a primary coil in a step-down transformer; and 
 controlling a primary positive voltage and a primary negative voltage across the primary coil, wherein the primary positive and negative voltages cause a secondary positive voltage and a secondary negative voltage across the secondary coil; and 
 controlling a voltage output on an output node of the adapter with a first switch, coupled between a first end tap of a secondary coil of the step-down transformer and ground, and a second switch, coupled between a second end tap of the step-down transformer and ground, and 
 alternately activating the first switch and the second switch by activating the first switch during the secondary positive voltage and activating the second switch during the secondary negative voltage based on the secondary positive and negative voltages across the secondary coil. 
 
     
     
       17. The method of  claim 16 , wherein voltage output on the output node of the adapter is less than or equal to 50 volts. 
     
     
       18. The method of  claim 16 , wherein a maximum voltage in the adapter is less than or equal to the alternating current voltage. 
     
     
       19. The method of  claim 16 , wherein controlling the voltage output on the output node of the adapter comprises controlling the voltage based on a power demand. 
     
     
       20. The method of  claim 16 , wherein applying a voltage across the primary coil includes switching a polarity of the voltage across the primary coil at a frequency of at least 50,000 Hz. 
     
     
       21. The adapter of  claim 2 , wherein activating the first switch comprises closing the first switch and connecting the first end tap to a second output of the adapter and wherein activating the second switch comprises closing the second switch and connecting the second end tap to the second output of the adapter. 
     
     
       22. The adapter of  claim 9 , wherein activating the first switch comprises closing the first switch and connecting the first end tap to a second output of the adapter and wherein activating the second switch comprises closing the second switch and connecting the second end tap to the second output of the adapter. 
     
     
       23. The method of  claim 16 , wherein activating the first switch comprises closing the first switch and connecting the first end tap to a second output of the adapter and wherein activating the second switch comprises closing the second switch and connecting the second end tap to the second output of the adapter.

Description:
BACKGROUND 
     Field 
     The present embodiments relate to power adapters. More specifically, the present embodiments relate to stepping-up the voltage in a power adapter after the voltage is stepped-down using a transformer. 
     Related Art 
     Adapters that are designed to supply power to electronic devices such as laptop computers often include a power factor correction (PFC) circuit. Typically, the PFC circuit steps-up the input voltage to a voltage higher than the input voltage, and in order to safely handle this voltage, the PFC circuit must include one or more high-voltage components. These high-voltage components are often physically large and may take up a sizable portion of the adapter volume, which may interfere with other design considerations for the adapter. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows an adapter in accordance with an embodiment. 
         FIG. 2  shows an adapter including a center-tapped secondary coil in accordance with an embodiment. 
         FIG. 3  shows an adapter including a half H-bridge in accordance with an embodiment. 
         FIG. 4A  depicts an exemplary graph of a control signal controlling a first switch in a half H-bridge coupled to the primary coil of a transformer in accordance with an embodiment. 
         FIG. 4B  depicts an exemplary graph of a control signal controlling a second switch in a half H-bridge coupled to the primary coil of a transformer in accordance with an embodiment. 
         FIG. 4C  depicts an exemplary graph of the voltage across the primary coil of an adapter transformer in accordance with an embodiment. 
         FIG. 5  shows an adapter including a half H-bridge and a center-tapped secondary coil in accordance with an embodiment. 
         FIG. 6  shows an adapter including an H-bridge in accordance with an embodiment. 
         FIG. 7A  depicts an exemplary graph of a control signal controlling two switches in an H-bridge coupled to the primary coil of a transformer in accordance with an embodiment. 
         FIG. 7B  depicts an exemplary graph of a control signal controlling two other switches in an H-bridge coupled to the primary coil of a transformer in accordance with an embodiment. 
         FIG. 7C  depicts an exemplary graph of the voltage across the primary coil of an adapter transformer in accordance with an embodiment. 
         FIG. 8  shows an adapter including an H-bridge and a center-tapped secondary coil in accordance with an embodiment. 
         FIG. 9  shows an adapter including a half H-bridge and a center-tapped secondary coil with an inductor in accordance with an embodiment. 
         FIG. 10A  depicts an exemplary graph of the voltage across the primary coil of an adapter transformer in accordance with an embodiment. 
         FIG. 10B  depicts an exemplary graph of a control signal controlling switch  906  in accordance with an embodiment. 
         FIG. 10C  depicts an exemplary graph of a control signal controlling switch  910  in accordance with an embodiment. 
         FIG. 11  shows an adapter including an H-bridge and a center-tapped secondary coil with an inductor in accordance with an embodiment. 
     
    
    
     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 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. 
       FIG. 1  shows an adapter in accordance with an embodiment. Alternating current (AC) voltage  102  is coupled to transformer  104 , which includes primary coil  106  and secondary coil  108 . Secondary coil  108  is coupled through rectifier  110 , across capacitor  112  through step-up converter  114  and across capacitor  116  to output  118 . 
     AC voltage  102  is any device that outputs an AC voltage and may include but is not limited to a wall plug that can be plugged into an AC voltage outlet. For example, AC voltage  102  may be a standard wall plug that is plugged into an electrical outlet, and may be in any standard available in any country. In some embodiments, AC voltage  102  also includes a line filter that filters the voltage from AC voltage  102 . 
     Transformer  104  is any step-down transformer with a primary coil and a secondary coil that can receive AC voltage from AC voltage  102  and step-down the received voltage and may be implemented in any technology. The turns ratio between primary coil  106  and secondary coil  108  may be set to any value based on the input voltage to transformer  104  and the desired output voltage. For example, in some embodiments, for an expected input voltage of 90 to 120 volts from AC voltage  102  and a desired output voltage in the range of 20 to 30 volts, a turns ratio between primary coil  106  and secondary coil  108  may be chosen to be about 4:1, while for an expected input voltage of 220 to 240 volts from AC voltage  102  for the same desired output voltage range, the turns ratio may be chosen to be about 8:1. In other embodiments, a turns ratio in the range of 4:1 up to 8:1 may be used. 
     Rectifier  110  is a voltage rectifier that converts the positive and negative voltage output from secondary coil  108  into voltage that is going positive only. Rectifier  110  may include but is not limited to a full-bridge rectifier, a half-bridge rectifier, or any other rectifier that outputs only a positive-going voltage from an input that is positive and negative, and it may be implemented in any technology. 
     Capacitor  112  and capacitor  116  are each any suitable capacitor selected based on factors including but not limited to voltage, capacity and leakage requirements, and may be implemented in any technology. Step-up converter  114  can be any type of step-up converter that steps-up an input voltage to a higher output voltage and may include a step-up converter controller (not shown) that controls the step-up converter based on feedback including but not limited to the power demanded from the adapter (e.g., from output  118 ), the output voltage of step-up converter  114 , and/or a power factor correction of the adapter. Step-up converter  114  may also include a bypass diode (not shown). In some embodiments, step-up converter  114  includes a boost converter. 
     Output  118  may be coupled to or configured to be coupled to any electronic device that uses direct current (DC) voltage to operate, including but not limited to a laptop computer, a tablet computer, a smartphone, and/or a battery charger. 
     The adapter of  FIG. 1  operates as follows. AC voltage is output from AC voltage  102  to primary coil  106 . The AC voltage input to primary coil  106  is stepped-down by transformer  104  to a lower voltage that is output across secondary coil  108 . The AC voltage output across secondary coil  108  is then rectified in rectifier  110  and input into step-up converter  114  across capacitor  112 . Step-up converter  114  then steps-up the voltage to a higher voltage for output across capacitor  116 . In some embodiments, step-up converter  114  steps-up the voltage to a value lower than the input voltage from AC voltage  102 . 
     In one embodiment, AC voltage  102  is a standard wall plug that plugs into a household electrical outlet and receives from 80 volts to 240 volts AC electricity at from 50 Hz to 60 Hz, transformer  104  has a turns ratio of 8:1, and step-up converter  114  is a boost converter that outputs 40 volts to capacitor  116  and output  118 . Capacitor  116  is a capacitor with a 50 volt maximum voltage rating. Output  118  is a laptop computer charger plug that is configured to power and/or charge a laptop computer. 
       FIG. 2  shows an adapter similar to the one depicted in  FIG. 1 , but with transformer  104  and rectifier  110  replaced by transformer  202 , diode  208  and diode  210  in accordance with an embodiment. In  FIG. 2 , AC voltage  102  is coupled to transformer  202  through primary coil  204 . Secondary coil  206  has a center tap coupled to ground, one end tap coupled to diode  208 , and the other end tap coupled to diode  210 . Diode  208  and diode  210  are coupled together and across capacitor  112  to step-up converter  114 , and across capacitor  116  to output  118 . 
     Transformer  202  is any step-down transformer with a primary coil and a center-tapped secondary coil that can receive AC voltage from AC voltage  102  and step-down the received voltage, and it may be implemented in any technology. The turns ratio between primary coil  204  and each arm of secondary coil  206  may be set to any value based on the input voltage to transformer  202  and the desired output voltage. For example, in some embodiments, for an expected input voltage of 90 to 120 volts from AC voltage  102  and a desired output voltage in the range of 20 to 30 volts, a turns ratio between primary coil  204  and each arm of secondary coil  206  may be chosen to be about 4:1, while for an expected input voltage of 220 to 240 volts from AC voltage  102  for the same desired output voltage range, the turns ratio may be chosen to be about 8:1. In other embodiments, a turns ratio of 4:1 up to 8:1 may be used. 
     Diode  208  and diode  210  can be any suitable diodes implemented in any technology and may be implemented using any combination of discrete or integrated technology. 
     The adapter of  FIG. 2  operates as follows. AC voltage is output from AC voltage  102  to primary coil  204 . On one-half of a cycle of the AC voltage applied to primary coil  204  (e.g., positive voltage from top to bottom of primary coil  204 ), the AC voltage is stepped-down and rectified in one arm of secondary coil  206  (e.g., between the center tap and diode  208 ), while in the other half-cycle of the AC voltage (e.g., negative voltage from top to bottom of primary coil  204 ), the AC voltage is stepped-down and rectified in the other arm of secondary coil  206  (e.g., between the center tap and diode  210 ). 
     The rectified voltage output from secondary coil  206  through diode  208  and diode  210  is then sent to step-up converter  114  across capacitor  112 . Then, as described above with reference to  FIG. 1 , step-up converter  114  steps-up the voltage to a higher voltage for output across capacitor  116 . 
       FIG. 3  shows an adapter including a half H-bridge in accordance with an embodiment. AC voltage  102  is coupled through rectifier  302 , across capacitor  304  and to the input of half H-bridge  306 . The output of half H-bridge  306  is coupled to primary coil  310  of transformer  308  and then to capacitor  312 . Secondary coil  314  is coupled to rectifier  316  which is coupled across capacitor  112  through step-up converter  114 , and across capacitor  116  to output  118 . Controller  324  is coupled to and controls switches S 1  and S 2  in half H-bridge  306  and also is coupled to and controls step-up converter  114 . In some embodiments, controller  324  may also receive input from the output of rectifier  302  across capacitor  304 , the output of rectifier  316  across capacitor  112 , and/or from output  118 . 
     Rectifier  302  is a voltage rectifier that converts the positive and negative voltage output from AC voltage  102  into voltage that is positive only. Rectifier  302  may include but is not limited to a full-bridge rectifier, a half-bridge rectifier, or any other rectifier that outputs only a positive-going voltage from an input that is positive and negative, and it may be implemented in any technology. 
     Capacitor  304  may be implemented in any technology and may be selected to have a peak voltage capacity based on the input voltage from AC voltage  102 , and its size may be selected based on factors including but not limited to the expected peak output power of the adapter. 
     Half H-bridge  306  is any half H-bridge that includes two individual switches S 1  and S 2 , each of which is controlled by controller  324 . Half H-bridge  306  uses switches S 1  and S 2  in combination with capacitor  312  to control the voltage across primary coil  310  in transformer  308 . For example, when switch S 1  is closed and switch S 2  is open, the voltage from the top to the bottom of primary coil  310  is positive and capacitor  312  is charging; when switch S 1  is open and switch S 2  is closed, the voltage from the top to the bottom of primary coil  310  is negative and capacitor  312  is discharging. Note that switches S 1  and S 2  can each be any type of switch implemented in any technology that can switch in response to a control signal. For example, switches S 1  and S 2  may include but are not limited to relays, or transistors such as FETs, including MOSFET transistors, and may be implemented using any combination of discrete and integrated components, and analog and/or digital technology. Note that capacitor  312  may be any capacitor selected based on factors including but not limited to the peak voltage from AC voltage  102 , the switching frequency of half H-bridge  306  and/or the output power of the adapter. 
     Transformer  308  is any step-down transformer with a primary coil and a secondary coil that can receive a switched voltage wave from half H-bridge  306  at the required frequency, voltage and power, and step-down the received voltage, and it may be implemented in any technology. The turns ratio between primary coil  310  and secondary coil  314  may be set to any value based on the input voltage to transformer  308  and the desired output voltage. In some embodiments, the turns ratio between primary coil  310  and secondary coil  314  may be 4:1, 8:1 or anywhere in the range from 4:1 and 8:1. 
     Rectifier  316  is a voltage rectifier that converts the positive and negative voltage output from secondary coil  314  into voltage that is positive only. Rectifier  316  may include but is not limited to a full-bridge rectifier, a half-bridge rectifier, or any other rectifier that outputs only a positive-going voltage from an input that is positive and negative, and it may be implemented in any technology. 
     Controller  324  is a controller implemented in any combination of hardware and/or software and in any technology, and may include any combination of integrated and discrete components and may be implemented in any hardware module or apparatus. Controller  324  controls each switch S 1  and S 2  in half H-bridge  306  and may receive input (not shown) from one or more of rectifier  302  across capacitor  304 , rectifier  316  across capacitor  112  and/or output  118 . Step-up converter  114  may be controlled by controller  324  or by a separate controller (not shown) to step up the input voltage to step-up converter  114  based on feedback including but not limited to the power demanded from the adapter (e.g., from output  118 ), the output voltage of step-up converter  114 , and/or a power factor correction of the adapter. Note that any inputs and outputs to controller  324  from the secondary side of transformer  308  may include an isolation device or circuit (not shown) to electrically isolate the secondary side of transformer  308  from the primary side such as an opto-isolator. 
     The adapter in  FIG. 3  operates as follow. AC voltage output from AC voltage  102  is rectified in rectifier  302  and input into half H-bridge  306  across capacitor  304 . Controller  324  controls switches S 1  and S 2  to alternately open and close, resulting in an alternately positive and negative voltage across primary coil  310 , as discussed below with respect to  FIGS. 4A-C . 
       FIGS. 4A and 4B  depict exemplary graphs of control signals from controller  324  controlling, respectively, switch S 1  and switch S 2  in half H-bridge  306  in accordance with an embodiment.  FIG. 4C  depicts an exemplary graph of the voltage across primary coil  310  as a result of the switching signals depicted in  FIGS. 4A and 4B . 
     During time period T 0 , controller  324  controls switch S 1  to close and S 2  to open so that the voltage across primary coil  310  is positive (i.e., from top to bottom) and capacitor  312  charges up. In time period T 1 , controller  324  controls switch S 1  to open and switch S 2  to close so that the voltage across primary coil  310  is negative as capacitor  312  discharges. As depicted in  FIGS. 4A-C , time periods T 0  and T 1  repeat, as controller  324  controls switches S 1  and S 2 . Note that controller  324  may control the duration of time periods T 0  and T 1  so that the frequency of the voltage-switching cycle is any desired frequency, and may include, but is not limited to frequencies from 10 kHz to 1 MHz. 
     The voltage from primary coil  310  is stepped-down across secondary coil  314 , rectified in rectifier  316  and output across capacitor  112  to step-up converter  114 . In some embodiments, controller  324  controls step-up converter  114  to continuously step-up the voltage from the input of step-up converter  114 , while in other embodiments, controller  324  controls step-up converter  114  to step-up the voltage input from rectifier  316  when the power demand from the adapter in  FIG. 3  exceeds a predetermined level or when the output voltage demanded at output  118  exceeds the voltage output from rectifier  316 . 
       FIG. 5  shows an adapter including a half H-bridge and a center-tapped secondary coil in accordance with an embodiment. AC voltage  102  is coupled through rectifier  302 , across capacitor  304  and to the input of half H-bridge  306 . The output of half H-bridge  306  is coupled to primary coil  504  of transformer  502  and then to capacitor  312 . Secondary coil  508  has a center tap coupled to ground, and one end tap is coupled to diode  512  and the other end tap is coupled to diode  514 . Diode  512  and diode  514  are coupled together and across capacitor  318  to step-up converter  114 , and across capacitor  116  to output  118 . Controller  324  is coupled to and controls switches S 1  and S 2  in half H-bridge  306  and also is coupled to and controls step-up converter  114 . In some embodiments, controller  324  may also receive input from the output of rectifier  302  across capacitor  304 , the output of diode  512  and diode  514  across capacitor  318 , and/or from output  118 . 
     Transformer  502  is any step-down transformer with a primary coil and a center-tapped secondary coil that can receive a switched voltage signal from half H-bridge  306  and step-down the received voltage, and it may be implemented in any technology. The turns ratio between primary coil  504  and each arm of secondary coil  508  may be set to any value based on the input voltage to transformer  502  and the desired output voltage. The turns ratio between primary coil  504  and secondary coil  508  may be set to any value based on the input voltage to transformer  502  and the desired output voltage. In some embodiments, the turns ratio between primary coil  504  and each arm of secondary coil  508  may be 4:1, 8:1 or anywhere in the range from 4:1 and 8:1. 
     Diode  512  and diode  514  can be any suitable diodes implemented in any technology and may be implemented using any combination of discrete or integrated technology. 
     The embodiment of  FIG. 5  operates similarly to that of  FIG. 3 , except that the voltage induced in secondary coil  508  between the center tap and diode  512  and diode  514  on each half cycle of the voltage across primary coil  504  is rectified in the same manner as described with respect to transformer  202  of  FIG. 2 . 
       FIG. 6  shows an adapter including an H-bridge in accordance with an embodiment. AC voltage  102  is coupled through rectifier  302  across capacitor  304  to the input to H-bridge  602 . The output of H-bridge  602  is coupled to primary coil  606  of transformer  604 . Secondary coil  608  of transformer  604  is coupled to rectifier  316 , across capacitor  318 , through step-up converter  114  and to output  118  across capacitor  116 . Controller  610  is coupled to and controls switches S 1 -S 4  in H-bridge  602  and also is coupled to and controls step-up converter  114 . In some embodiments, controller  610  may also receive input from the output of rectifier  302  across capacitor  304 , the output of rectifier  316  across capacitor  318 , and/or from output  118 . Note that in some embodiments a separate controller may be used to control step-up converter  114 . 
     H-bridge  602  is any H-bridge that includes four individual switches S 1 -S 4 , each of which is controlled by controller  610 . H-bridge  602  uses switches S 1  to S 4  to control the voltage across primary coil  606  in transformer  604 . For example, when switches S 1  and S 4  are closed and switches S 2  and S 3  are open, the voltage from the top to the bottom of primary coil  606  is positive; when switches S 1  and S 4  are open and switches S 2  and S 3  are closed, the voltage from the top to the bottom of primary coil  606  is negative. Note that switches S 1  to S 4  can each be any type of switch implemented in any technology that can switch in response to a control signal. For example, switches S 1  to S 4  may include but are not limited to relays, or transistors such as FETs, including MOSFET transistors, and may be implemented using any combination of discrete and integrated components, and analog and/or digital technology. 
     Transformer  604  is any step-down transformer with a primary coil and a secondary coil that can receive a switched voltage wave from H-bridge  602  at the required frequency, voltage and power, and step-down the received voltage, and it may be implemented in any technology. The turns ratio between primary coil  606  and secondary coil  608  may be set to any value based on the input voltage to transformer  604  and the desired output voltage. In some embodiments, the turns ratio between primary coil  606  and secondary coil  608  may be 4:1, 8:1 or anywhere in the range from 4:1 and 8:1. 
     Controller  610  is a controller implemented in any combination of hardware and/or software and in any technology, and may include any combination of integrated and discrete components and may be implemented in any hardware module or apparatus. Controller  610  controls each switch S 1  to S 4  in H-bridge  602  and may receive input (not shown) from one or more of rectifier  302  across capacitor  304 , rectifier  316  across capacitor  318  and/or output  118 . Step-up converter  114  may be controlled by controller  610  or by a separate controller (not shown) to step up the input voltage to step-up converter  114  based on feedback including but not limited to the power demanded from the adapter (e.g., from output  118 ), the output voltage of step-up converter  114 , and/or a power factor correction of the adapter. Note that any inputs and outputs to controller  610  from the secondary side of transformer  604  may include an isolation device or circuit (not shown) to electrically isolate the secondary side of transformer  604  from the primary side such as an opto-isolator. 
     The adapter in  FIG. 6  operates as follow. AC voltage output from AC voltage  102  is rectified in rectifier  302  and input into H-bridge  602  across capacitor  304 . Controller  610  controls switches S 1  and S 4 , and S 2  and S 3  to alternately open and close, resulting in an alternately positive and negative voltage across primary coil  606 , as discussed below with respect to  FIGS. 7A-D . 
       FIGS. 7A and 7B  depict exemplary graphs of control signals from controller  610  controlling, respectively, switches S 1  and S 4 , and switches S 2  and S 3  in H-bridge  602  in accordance with an embodiment.  FIG. 7C  depicts an exemplary graph of the voltage across primary coil  606  as a result of the switching signals depicted in  FIGS. 7A and 7B . 
     During time period T 0 , controller  610  controls switches S 1  and S 4  to close and switches S 2  and S 3  to open so that the voltage across primary coil  606  is positive (i.e., from top to bottom). In time period T 1 , controller  610  controls switches S 1  and S 4  to open and switches S 2  and S 3  to close so that the voltage across primary coil  606  is negative. As depicted in  FIGS. 7A-C , time periods T 0  and T 1  repeat, as controller  610  controls switches S 1  to S 4 . Note that controller  610  may control the duration of time periods T 0  and T 1  so that the frequency of the voltage-switching cycle is any desired frequency, and may include, but is not limited to frequencies from 10 kHz to 1 MHz. Note that controller  610  may also control switches S 1  and S 4  and switches S 2  and S 3  as described in the U.S. patent application entitled “Controlling an Adapter Transformer Voltage,” by Louis Luh, Eric Smith, and P. Jeffrey Ungar, Ser. No. 13/568,414 filed on 7 Aug. 2012, which is hereby fully incorporated by reference. 
     The voltage from primary coil  606  is stepped-down across secondary coil  608 , rectified in rectifier  316  and output across capacitor  318  to step-up converter  114 . In some embodiments, controller  610  controls step-up converter  114  to continuously step-up the voltage from the input of step-up converter  114 , while in other embodiments, controller  610  controls step-up converter  114  to step-up the voltage input from rectifier  316  when the power demand from the adapter in  FIG. 6  exceeds a predetermined level or when the output voltage demanded at output  118  exceeds the voltage output from rectifier  316 . 
       FIG. 8  shows an adapter similar to the one depicted in  FIG. 6 , but with transformer  604  and rectifier  316  replaced by transformer  502 , diode  512  and diode  514  in accordance with an embodiment. AC voltage  102  is coupled through rectifier  302  across capacitor  304  to the input to H-bridge  602 . The output of H-bridge  602  is coupled to primary coil  504  of transformer  502 . Secondary coil  508  has a center tap coupled to ground, one end tap coupled to diode  512 , and the other end tap coupled to diode  514 . Diode  512  and diode  514  are coupled together and across capacitor  318  to step-up converter  114 , and then across capacitor  116  to output  118 . Controller  610  is coupled to and controls switches S 1 -S 4  in H-bridge  602  and also is coupled to and controls step-up converter  114 . In some embodiments, controller  610  may also receive input from the output of rectifier  302  across capacitor  304 , the output of diode  512  and diode  514  across capacitor  318 , and/or from output  118 . 
     The embodiment of  FIG. 8  operates similarly to that of  FIG. 6 , except that the voltage induced in secondary coil  508  between the center tap and diode  512  and diode  514  on each half cycle of the voltage across primary coil  504  is rectified in the same manner as described above with respect to transformer  202  of  FIG. 2  rectifying the voltage from primary coil  204  using center-tapped secondary coil  206  and diode  208  and diode  210 . Controller  610  controls switches S 1  and S 4 , and switches S 2  and S 3  in H-bridge  602  as described above with reference to  FIGS. 6 and 7 . 
       FIG. 9  shows an adapter with a half H-bridge and a center-tapped secondary coil with an inductor in accordance with an embodiment. AC voltage  102  is coupled through rectifier  302  across capacitor  304  to the input to half H-bridge  306 . The output of half H-bridge  306  is coupled to primary coil  504  of transformer  502  and capacitor  506 . Secondary coil  508  has a center tap coupled through inductor  902  to ground, and end tap  904  is coupled to diode  512  and end tap  908  is coupled to diode  514 . Switch  906  is coupled from end tap  904  to ground, and switch  910  is coupled from end tap  908  to ground. Diode  512  and diode  514  are coupled together and across capacitor  116  to output  118 . Controller  912  is coupled to and controls switches S 1  and S 2  in half H-bridge  306 , and also switch  906  and switch  910 . In some embodiments, controller  912  may also receive input from the output of rectifier  302  across capacitor  304 , and/or from output  118 . 
     Inductor  902  can be any type of inductor implemented in any technology. The inductance of inductor  902  can be selected based on parameters including the inductance of secondary coil  508 . In some embodiments, the ratio between the inductance of each arm of secondary coil  508  and the inductance of inductor  902  is 5, 10 or in the range from 2 to 20. For example, in one embodiment, the inductance of one arm of secondary coil  508  is 100 microhenries and the inductance of inductor  902  is selected to be 10 microhenries. 
     Switch  906  and switch  910  can each be any type of switch implemented in any technology that can switch in response to a control signal. For example, switch  906  and/or switch  910  may include but are not limited to relays, or transistors such as FETs, including MOSFET transistors, and may be implemented using any combination of discrete and integrated components, and analog and/or digital technology. Controller  912  is similar to controller  324  and also includes control logic, programming and/or circuitry to control switch  906  and switch  910  as described below. 
     The embodiment of  FIG. 9  operates similarly to the embodiment of  FIG. 5 . Controller  912  controls half H-bridge  306  in the same manner as controller  324 . In addition, controller  912  may control switch  906  and switch  910  to boost the voltage from secondary coil  508  as depicted in  FIGS. 10B and 10C  discussed below. 
       FIG. 10A  depicts an exemplary graph of the voltage across the primary coil  504 , and  FIGS. 10B and 10C  depict the relative timing of the control signals, respectively, for switch  906  and switch  910  from controller  912  to boost the voltage from secondary coil  508 . As depicted in  FIG. 10A , during time period T 0  the voltage across primary coil  504  is positive. This induces a positive voltage in secondary coil  508  between the center tap and end tap  904 . As depicted in  FIG. 10B , controller  912  controls switch  906  to remain closed during the first portion of time period T 0 ; then, during the second portion, controller  912  controls switch  906  to open, boosting the voltage from the top arm of secondary coil  508 . Controller  912  may vary the portion of T 0  during which switch  906  is open/closed in order to vary the magnitude of the voltage boost generated. Note that as depicted in  FIG. 10C , controller  912  controls switch  910  to remain open during time period T 0 . 
     As depicted in  FIG. 10C , during time period T 1 , controller  912  controls switch  910  in a similar fashion to boost the voltage when the voltage across primary coil  504  is negative and the induce voltage in secondary coil  508  is positive from the center tap to end tap  908  across the bottom arm of secondary coil  508 . Controller  912  controls switch  910  to remain closed during the first portion of time period T 1 ; then, during the second portion, controller  912  controls switch  910  to open, boosting the voltage from the bottom arm of secondary coil  508 . Note that as depicted in  FIG. 10B  controller  912  controls switch  906  to remain open during time period T 1 . Controller  912  may vary the portion of T 1  during which switch  910  is open/closed in order to vary the magnitude of the voltage boost generated. 
     Also note that if transformer  502  has the opposite polarity, then positive voltage is induced in the opposite arm of secondary coil  508  during time periods T 0  and T 1 , and the switching signals for switch  906  are switch  910  are interchanged. Additionally, if controller  912  is not going to boost the voltage from transformer  502 , then controller  912  controls switch  906  and switch  910  both to remain open 
       FIG. 11  shows an adapter similar to the one depicted in  FIG. 9 , with half H-bridge  306  replaced by H-bridge  602  and controller  912  replaced by controller  1102 . AC voltage  102  is coupled through rectifier  302  across capacitor  304  to the input to H-bridge  602 . The output of H-bridge  602  is coupled to primary coil  504  of transformer  502 . Secondary coil  508  has a center tap coupled through inductor  902  to ground, and end tap  904  is coupled to diode  512  and end tap  908  is coupled to diode  514 . Switch  906  is coupled from end tap  904  to ground, and switch  910  is coupled from end tap  908  to ground. Diode  512  and diode  514  are coupled together and across capacitor  116  to output  118 . 
     Controller  1102  is coupled to and controls switches S 1  to S 4  in H-bridge  602 , and also switch  906  and switch  910 . In some embodiments, controller  1102  may also receive input from the output of rectifier  302  across capacitor  304 , and/or from output  118 . Controller  1102  includes control logic, programming and/or circuitry to control H-bridge  602  in the same manner as controller  610  described above, and switch  906  and switch  910  in the same manner as controller  912  described above. The embodiment of  FIG. 11  operates similarly to the embodiment of  FIG. 9 , except instead of controller  912  controlling the voltage across primary coil  504  using half H-bridge  306 , the voltage across primary coil  504  is controlled by controller  1102  using H-bridge  602 . 
     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: 20120808
Publication Date: 20170307
Grant Date: 20170307
Priority Date: 20120808
Inventors: LUH LOUIS
SMITH ERIC G.
Assignee: APPLE INC
CPC Classifications: [{"code": "H02M7/53871", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/2176", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M2001/007", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/4208", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/335", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M3/337", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M7/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/156", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02B70/126", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M7/2176", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M3/33573", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/33571", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/2176", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M3/33573", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/33571", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M1/007", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/007", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M7/53871", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/335", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M3/335", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02B70/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/4208", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02B70/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M3/156", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M3/156", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/4208", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/10", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 48877544