Abstract:
A high efficiency battery charger. The high-efficiency battery charger can include a first transformer to produce a charging current, a second transformer to produce a maintenance current lower than the charging current, a power feed circuit having an input for connection to a power source, and control circuitry configured to detect a depleted battery to cause the power feed circuitry to feed power to the first transformer while disabling the second transformer, and to detect a charged battery to cause the power feed circuitry to feed power to the second transformer while disabling the first transformer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/707,197, filed on Sep. 28, 2012, titled “HIGH-EFFICIENCY BATTERY CHARGER,” as well as U.S. Provisional Patent Application No. 61/733,700, filed Dec. 5, 2012, and titled “HIGH-EFFICIENCY BATTERY CHARGER.” The disclosures of both foregoing applications are incorporated herein by reference along with each and every patent and patent application mentioned herein below. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to a battery charger, and, particularly, to a battery charger which can operate with high efficiency in various circumstances. 
       BACKGROUND 
       [0003]    Linear style battery chargers are well-known in the art. Recently, multi-frequency and high-frequency battery chargers have entered the market and proven effective at providing charge energy to various types of batteries at a much increased efficiency. However, both types of battery chargers suffer from several significant drawbacks. 
         [0004]    Generally, a large transformer provides more current than a smaller transformer, but also experiences greater electrical losses as it operates. Relatively large transformers are needed in order to provide the high current necessary to charge a battery. However, when a battery is fully charged, float charging or trickle charging the battery to maintain its charge only requires a relatively low current. Battery chargers which use only one transformer must select a large transformer in order to provide the high current necessary, but must endure the high losses of the large transformer even when providing only a maintenance charge. Using multiple transformers does little to remedy this if all of the transformers remain active and connected, as transformers experience electrical power loss even when they are not providing current. 
       SUMMARY 
       [0005]    According to an exemplary embodiment of the present invention, a high efficiency battery charger is disclosed. The high-efficiency battery charger can include a first transformer to produce a charging current, a second transformer to produce a maintenance current lower than the charging current, a power feed circuit having an input for connection to a power source, and control circuitry configured to detect a depleted battery to cause the power feed circuitry to feed power to the first transformer while disabling the second transformer, and to detect a charged battery to cause the power feed circuitry to feed power to the second transformer while disabling the first transformer. 
         [0006]    According to another exemplary embodiment, a high-efficiency battery charger is disclosed. The high-efficiency battery charger can include a power source, a plurality of transformers for providing power to a battery, power feed circuitry which can selectively provide power from the power source to one of the plurality of transformers while disconnecting the rest of the plurality of transformers from the power source, and control circuitry. 
         [0007]    According to a still further exemplary embodiment, a method for operating a high-efficiency battery charger is disclosed. The method can include charging the battery using a main transformer that is larger than an auxiliary transformer, determining whether the battery is fully charged, disconnecting the main transformer when the battery is determined to be fully charged, and providing a maintenance charge using the auxiliary transformer while the main transformer is disconnected. 
         [0008]    Further aspects, objectives, and advantages, as well as the structure and function of embodiments, will become apparent from a consideration of the description, drawings, and examples. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The features and advantages of the invention will be apparent from the following drawings wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. 
           [0010]      FIG. 1  is a block diagram of a high efficiency battery charger according to an embodiment of the invention; 
           [0011]      FIG. 2  is a flow chart of the operation of a high efficiency battery charger according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Embodiments of the invention are discussed in detail below. In describing embodiments, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. A person skilled in the relevant art will recognize that other equivalent parts can be employed and other methods developed without departing from the spirit and scope of the invention. 
         [0013]    Generally,  FIGS. 1 and 2  relate to a high-efficiency battery charger  100 . The high-efficiency battery charger  100  can include one or more independently operable transformers in its charging circuitry. The transformers can be optimized for different situations, allowing high-efficiency battery charger  100  to remain efficient across a variety of modes of operation. 
         [0014]      FIG. 1  shows an exemplary embodiment of a high-efficiency battery charger  100 . High-efficiency battery charger  100  can include charging circuitry  102 . Charging circuitry  102  can include one or more transformers, for example main transformer  104  and auxiliary transformer  106 . The transformers of charging circuitry  102  can be any type of transformer, for example linear transformers, high-frequency transformers, or any other type of transformers as desired, and any combination thereof The transformers of charging circuitry  102  can have any desired configuration, for example any desired size or shape. In some exemplary embodiments, the transformers of charging circuitry  102  can include, for example, E-E type core shapes, or E-I type core shapes, or any desired combination thereof. The size of the transformers in charging circuitry  102  can be understood in any desired terms, for example physical size. The size of the transformers in charging circuitry  102  can also be understood in terms of maximum power output capacity, or kilovolt-ampere (KVA) rating, in which a higher KVA rating for a specific input and output voltage indicates a larger transformer, as is well-known in the art. 
         [0015]    In some exemplary embodiments, main transformer  104  and auxiliary transformer  106  can have different configurations, for example different shapes or sizes. In some exemplary embodiments, main transformer  104  can be larger than auxiliary transformer  106 . For example, auxiliary transformer  104  can be an E-E or E-I type transformer with a core diameter in the range of 12 mm-16 mm, and main transformer can be an E-E or E-I type transformer with a core diameter in the range of 28 mm-55 mm, or even larger as desired. As a result, main transformer  104  can be capable of providing more current than auxiliary transformer  106 , but can also be subject to higher energy losses during operation. As an example, in some embodiments main transformer  104  can provide current in a range of approximately 1 ampere to approximately 100 amperes, and auxiliary transformer  106  can provide current in a range of approximately 0 amperes to approximately 2 amperes. In further exemplary embodiments, main transformer  104  can also provide a boost current in a range of approximately 50 amperes to approximately 400 amperes. 
         [0016]    Charging circuitry  102  can also include filter and rectifier circuits, for example filter and rectifier circuits  108  and  110 , which can be coupled to main transformer  104  and auxiliary transformer  106 , respectively. As an example, the rectifiers in the filter and rectifier circuits of charging circuitry  102  can be any desired number of diodes, for example one diode or four diodes. Additionally, the filters in the filter and rectifier circuits of charging circuitry  102  can be one or more capacitors or inductors, in any desired combination. The filter and rectifier circuits of charging circuitry  102  can be configured to rectify and condition the alternating current output of the transformers of charging circuitry  102  so that it is suitable for charging a battery, as is well-known to one skilled in the art. 
         [0017]    Still referring to  FIG. 1 , high-efficiency battery charger  100  can also include power feed circuitry  112  and power source  114 . Power source  112  can be any source of electrical power, for example a standard wall socket providing alternating current power. Power feed circuitry  112  can receive input from power source  114  and can filter or otherwise condition it in order to provide suitable output for charging circuitry  102 . If, for example, one or more of the transformers of charging circuitry  102  is a high-frequency transformer, for example as known from U.S. Pat. No. 6,822,425, the entirety of which is incorporated herein by reference, then power feed circuitry  112  can include one or more switches suitable to drive the high-frequency transformers. The switches can be any type of switch as desired. In some exemplary embodiments, the switches can be field effect transistor (FET) switches, and can be controlled with pulse width modulation (PWM) controllers, as is well-known to one skilled in the art. Power feed circuitry  112  can selectively provide suitable output to any of the transformers of charging circuitry  102 , alone or in combination. Power feed circuitry  112  can also disconnect transformers from power source  114  when the transformers are not in use. This can reduce the overall amount of electrical power loss in high-efficiency battery charger  100 , as transformers generally experience electrical power loss whenever they are connected to a power source. In some exemplary embodiments, power feed circuitry  112  can isolate charging circuitry  102  from power source  114  using, for example, opto-couplers, opto-isolators, isolating transformers, or any other desired technique, as is well-known to one skilled in the art. 
         [0018]    Again referring to  FIG. 1 , high-efficiency battery charger  100  can include control circuitry  116 . Control circuitry  116  can be logic circuitry, can be programmable, such as a central processing unit (CPU) with associated memory, or can be any other desired type of control circuitry or combination thereof. Control circuitry  116  can include any type of control circuitry as desired, for example integrated circuits such as power management circuits or PWM controllers, or can be discrete logic components, as desired. Control circuitry  116  can receive input from and provide control output to any other component of high-efficiency battery charger  100 , as desired. For example, control circuitry  116  can accept clock input from clock  122 . Control circuitry  116  can also receive input relating to information regarding the state of the battery connected to high-efficiency battery charger  100 , for example battery type, battery connection status, or battery polarity. Control circuitry  116  can also receive input regarding the status of high-efficiency battery charger  100 , for example operating mode, transformer operation status, power supply voltage, battery voltage, charging voltage, charging current, frequency, engine start detection, the amount of time any of the above has been applied or has left to be applied, or any other information as desired. 
         [0019]    In some exemplary embodiments, control circuitry  116  can also accept input from user input  120 . User input  120  can be one or more buttons, switches, keyboards, dials, or any other type of input as desired. User input  120  can allow a user to provide information regarding the operation of high-efficiency battery charger  100 , for example battery type, battery size, battery voltage, power source type, or any other information as desired. User input  120  can allow a user to make selections regarding the desired function of high-efficiency battery charger  100 , for example desired operating mode, transformer operation status, power supply voltage, charging voltage, charging current, frequency, amount of time desired for any function, or any other function as desired. 
         [0020]    Control circuitry  116  can make use of the inputs received to provide output to other components of high-efficiency battery charger  100 . For example, control circuitry  116  can provide control output to display  118 . Display  118  can be any type of display, for example one or more cathode ray tubes (CRT), light-emitting diodes (LED), electroluminescent displays (ELD), electronic paper or E-Ink displays, plasma display panels (PDP), liquid crystal displays (LCD), or any other type of display as desired. Display  118  can display any type of information relating to the function of high-efficiency battery charger  100 , for example operating mode, battery type, battery connection status, battery polarity, power supply voltage, battery voltage, charging voltage, charging current, frequency, engine start detection, the amount of time any of the above has been applied or has left to be applied, or any other information as desired. 
         [0021]    Control circuitry  116  can also provide control output to power feed circuitry  112  and charging circuitry  102 . In some exemplary embodiments, control circuitry  116  can instruct power feed circuitry to provide power from power source  114  to one of the transformers of charging circuitry  102  and to disconnect the rest of the transformers of charging circuitry  102 . This can reduce the overall amount of electrical power loss in high-efficiency battery charger  100 , as transformers generally experience electrical power loss whenever they are connected to a power source. 
         [0022]    In some exemplary embodiments, high-efficiency battery charger  100  can also include any other components, as desired, for example fans or other cooling devices. 
         [0023]    High-efficiency battery charger  100  can operate according to any desired protocol. High-efficiency battery charger  100  can operate in one or more modes, for example charge mode and maintenance charge mode. In some exemplary embodiments, when high-efficiency battery charger  100  is in charge mode, control circuitry  116  can instruct power feed circuitry  112  to provide power to main transformer  104  while disconnecting auxiliary transformer  106 . In further exemplary embodiments, when high-efficiency battery charger  100  is in maintenance charge mode, control circuitry  116  can instruct power feed circuitry  112  to provide power to auxiliary transformer  106  while disconnecting main transformer  104 . In this way, high-efficiency battery charger  100  can enter charge mode when the high current which can be provided by main transformer  104  is required, and can enter maintenance charge mode to provide a low-loss no-load, float, or trickle charge from auxiliary transformer  106  when the high losses associated with main transformer  104  are not desirable. 
         [0024]    Turning now to  FIG. 2 , an exemplary embodiment of a protocol for operating high-efficiency battery charger  100  is shown. At step  202 , control circuitry  116  can determine that AC power source  114  has been connected to power feeds  112 . At step  204 , control circuitry can determine which mode has been selected based on user input  120 . If charge mode has not been selected, high-efficiency battery charger  100  can enter another mode at step  206 . If charge mode has been selected, control circuitry  116  can determine at step  208  whether the battery is properly connected. If the battery is not properly connected, for example the polarities are reversed at clamps connecting the charger to battery terminals, control circuitry  116  can move to step  110  and instruct display  118  to display this information and stand by for further user input. If the battery is well-connected, control circuitry  116  can, at step  212 , instruct power feed circuitry  112  to provide power from the power source  114  to main transformer  104  while disconnecting auxiliary transformer  106 . At step  214 , control circuitry  116  can determine whether the battery is fully charged. If the battery is not fully charged, high-efficiency battery charger  100  can continue charging the battery with main transformer  104  and return to step  214 . If the battery is fully charged, control circuitry  116  can proceed to step  218  and instruct power feed circuitry  112  to disconnect main transformer  104 . The control circuitry  116  can then, at step  220 , charge the battery in maintenance charge mode using only auxiliary transformer  106 , and can do so at step  222  until the battery is disconnected. 
         [0025]    In other exemplary embodiments, high-efficiency battery charger  100  can use any protocol as desired. For example, high-efficiency battery charger  100  can enter charge mode for an amount of time set by the user, or on a schedule specified by the user. High-efficiency battery charger  100  can switch from charge mode to maintenance charge mode when the battery is detected to be full, when the battery has reached a pre-determined voltage, or under any other desired conditions. 
         [0026]    The embodiments illustrated and discussed in this specification are intended only to teach those skilled in the art the best way known to the inventors to make and use the invention. Nothing in this specification should be considered as limiting the scope of the present invention. All examples presented are representative and non-limiting. The above-described embodiments of the invention may be modified or varied, without departing from the invention, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the claims and their equivalents, the invention may be practiced otherwise than as specifically described.