Patent Publication Number: US-2023155507-A1

Title: Charger integrated circuit including bidirectional switching converter, and electronic device including the charger integrated circuit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application Nos. 10-2021-0157096 and 10-2022-0063679, filed on Nov. 15, 2021, and May 24, 2022, respectively, in the Korean Intellectual Property Office, the disclosures of which are incorporated by reference herein in their entireties. 
     BACKGROUND 
     With the rapid development of electronic devices, electronic devices capable of exchanging information or data have been used in various applications. Electronic devices use a rechargeable battery as a power supply and allow mobility of the electronic devices. The capacity of the battery is limited, and a user needs to properly charge the battery before the battery capacity is entirely exhausted. A travel adapter (TA) that enables charging of the battery may convert power supplied from an alternating current (AC) (at about 110 V to about 220 V for household power) or another power supply means (e.g., a computer), into direct current (DC) power necessary for charging the battery. Thus, the TA provides DC power to an electronic device. The electronic device may use the DC power converted by the TA to charge the battery. 
     Recently, mobile devices such as a smartphone and a tablet PC support a switching mode with various charging circuits to stably support wireless and wired operations even when input power is unstable during wired and wireless charging, while simultaneously supporting wired and wireless charging. However, an over-current may occur in the charging circuit when the switching mode transitions to another mode. 
     SUMMARY 
     Example embodiments relate to a bidirectional switching converter that supports a plurality of switching modes and seamlessly transitions the plurality of switching modes, a charger integrated circuit (IC) including the bidirectional switching converter, and an electronic device including the charger IC. 
     According to an example embodiment of the inventive concepts, there is provided a charger integrated circuit (IC) including a bidirectional switching converter including a plurality of switching elements including a first switching element, a second switching element, a third switching element, and a fourth switching element which are connected in series to a first input/output node, an inductor connected between a first end of the third switching element and a second input/output node, and a capacitor connected to a second end of the second switching element and a third end of the third switching element, and a controller configured to generate a first pulse width modulation (PWM) signal and a second PWM signal based on a plurality of sensing signals received from the bidirectional switching converter, in a buck-boost mode, a first switching signal controlling switching operations of the first switching element and the fourth switching element based on the first PWM signal, and a second switching signal controlling switching operations of the second switching element and the third switching element based on the second PWM signal in response to an average value of an inductor current flowing through the inductor being positive, and the first switching signal based on the second PWM signal, and the second switching signal based on the first PWM signal and in response to the average value of the inductor current being negative. 
     According to another example embodiment of the inventive concepts, there is provided a charger integrated circuit (IC) including a 3-level bidirectional switching converter and a controller, wherein the 3-level bidirectional switching converter includes a first switching element connected between a first node and a second node, a first input voltage is applied to or a first output voltage is output from the first node, a second switching element connected between the second node and a third node, a third switching element connected between the third node and a fourth node, a fourth switching element connected between the fourth node and a fifth node, a capacitor connected between the second node and the fourth node, and an inductor connected between the third node and a sixth node, and the controller is configured to, in a first switching mode, in response to an average current of the inductor having a positive value, turn on or off the first switching element and the fourth switching element based on a first pulse width modulation (PWM) signal, turn on and off the second switching element and the third switching element based on a second PWM signal, and in response to the average current of the inductor having a negative value, turn on or off the first switching element and the fourth switching element based on the second PWM signal, and turn on and off the second switching element and the third switching element based on the first PWM signal. 
     According to another example embodiment of the inventive concepts, there is provided an electronic device including a battery and a charger integrated circuit (IC) configured to form a first power path in a first direction to charge the battery based on a first switching operation in a buck mode, form a second power path in a second direction opposite to the first direction based on a second switching operation to provide power to an external device based on a voltage charged in the battery in a boost mode, and charge the battery based on a third switching operation or supply the power to the external device in a buck-boost mode, wherein the charger IC includes a switching circuit including a plurality of switching elements, an inductor, and a capacitor, and the charger IC is further configured to adjust periods in which each of a plurality of switching voltages applied to the plurality of switching elements has an active level and an inactive level according to a direction of an inductor current flowing through the inductor in the buck-boost mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Example embodiments of the inventive concepts will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. 
       In order to more fully understand the drawings recited in the detailed description of the inventive concepts, a brief description of each drawing is provided. 
         FIG.  1    is a block diagram schematically illustrating an electronic device including a charger integrated circuit (IC) according to some example embodiments; 
         FIG.  2    is a circuit diagram illustrating a bidirectional switching converter according to some example embodiments; 
         FIGS.  3 A and  3 B  illustrate a power path during a buck converting operation of a bidirectional switching converter according to some example embodiments; 
         FIGS.  4 A and  4 B  illustrate a power path during a boost converting operation of a bidirectional switching converter according to some example embodiments; 
         FIGS.  5 A and  5 B  are timing diagrams when a bidirectional switching converter performs a buck converting operation according to some example embodiments; 
         FIG.  6    is a block diagram schematically illustrating a controller controlling a bidirectional switching converter according to some example embodiments; 
         FIG.  7    is a circuit diagram schematically illustrating a modulator of  FIG.  6   ; 
         FIG.  8    is a timing diagram illustrating first and second pulse width modulation (PWM) signals generated by the modulator of  FIG.  7   ; 
         FIG.  9    is a circuit diagram schematically illustrating a PWM logic of  FIG.  6   ; 
         FIGS.  10 A and  10 B  are timing diagrams of signals of a bidirectional switching converter and a controller according to some example embodiments; 
         FIG.  11    is a timing diagram of signals of a bidirectional switching converter and a controller according to a comparative example; 
         FIG.  12    is a block diagram schematically illustrating an electronic device including a charger IC according to some example embodiments; and 
         FIG.  13    is a block diagram illustrating a configuration of an electronic device including a charger IC according to some example embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS 
     Hereinafter, example embodiments of the inventive concepts will be described in detail with reference to the accompanying drawings. 
       FIG.  1    is a block diagram schematically illustrating an electronic device  10  including a charger integrated circuit (IC)  100  according to some example embodiments. 
     Referring to  FIG.  1   , the electronic device  10  may include the charger IC  100  and a battery  200 . Besides, the electronic device  10  may further include a main processor and peripheral devices. For example, the electronic device  10  may be a mobile device such as a smart phone, a tablet personal computer (PC), a mobile phone, a personal digital assistant (PDA), a laptop, a wearable device, a global positioning system (GPS) device, an e-book terminal, a digital broadcasting terminal, an MP3 player, a digital camera, etc. For example, the electronic device  10  may be an electric vehicle. 
     The battery  200  may be embedded in the electronic device  10 . In some example embodiments, the battery  200  may be detachable from the electronic device  10 . The battery  200  may include one or a plurality of battery cells. A plurality of battery cells may be connected to each other in series or parallel. When an external charging device is not connected to the electronic device  10 , the battery  200  may supply power to the electronic device  10 . 
     The charger IC  100  may charge the battery  200  and may be referred to as a “battery charger”. In addition, the charger IC  100  may supply power to an external device (e.g., a wired power interface  310  or a wireless power interface  320 ) connected to the charger IC  100  based on a voltage charged in the battery  200 . For example, the charger IC  100  may be implemented as one or more integrated circuit chips, and may be mounted on a printed circuit board. 
     The charger IC  100  may include a bidirectional switching converter  110  and a controller  120 . The bidirectional switching converter  110  may be implemented as a 3-level DC-DC converter including a plurality of switching elements Q 1 , Q 2 , Q 3 , and Q 4  in  FIG.  2   , a flying capacitor CF in  FIG.  2   , and an inductor L in  FIG.  2   . Here, the 3-level means the number of voltage levels used for a switching operation. The 3-level DC-DC converter may generate an output voltage by switching an input voltage, a (½)*input voltage, and a ground voltage (e.g., 0 V). The bidirectional switching converter  110  may perform a buck converting operation of generating an output voltage by stepping down an input voltage or a boost converting operation of generating an output voltage by boosting the input voltage. 
     When the bidirectional switching converter  110  steps down the input voltage, that is, during the buck converting operation, a first power path may be formed in a first direction in which power is supplied to the battery  200  from at least one external device connected through the wired power interface  310  and/or the wireless power interface  320 , and, when the bidirectional switching converter  110  boosts the input voltage, that is, during the boost converting operation, a second power path may be formed in a second direction through which power is supplied from the battery  200  to the at least one external device. Hereinafter, in the example embodiments, the first direction will be referred to as a forward direction, and the second direction will be referred to as a reverse direction. Accordingly, the buck converting operation of the bidirectional switching converter  110  will be used along with a forward buck converting operation, and the boost converting operation will be used along with a reverse boosting converting operation. 
     The bidirectional switching converter  110  may operate in a buck mode (also called a forward buck mode or a buck single mode), a boost mode (also called a reverse boost mode or a boost single mode) or a buck-boost mode (also called a forward buck-reverse boost mode or a buck-boost composite mode). 
     In the buck mode, the bidirectional switching converter  110  may step down an input voltage by performing the forward buck converting operation, and may charge the battery  200  based on the step-down voltage. In the boost mode, the bidirectional switching converter  110  may boost a voltage input from the battery  200  by performing the reverse boost converting operation, and may supply power to an external device based on the boosted voltage. In the buck-boost mode, the bidirectional switching converter  110  may perform the forward buck converting operation or the reverse boosting converting operation according to an amount of power supplied from a connected external device or an amount of power supplied to the external device. 
     The controller  120  may control a mode transition between a plurality of switching modes of the bidirectional switching converter  110 , for example, the forward buck mode, the reverse boost mode, and the forward buck-reverse boost mode. Also, the controller  120  may control a switching operation of the bidirectional switching converter  110  according to the switching mode. 
     The controller  120  may control the switching operation of the bidirectional switching converter  110  so that an output voltage of the bidirectional switching converter  110  may maintain a target level, for example, a first target level set with respect to the output voltage. In addition, the controller  120  may control the switching operation of the bidirectional switching converter  110  so that a voltage (hereinafter referred to as a flying capacitor voltage) between both ends of a flying capacitor (C F  in  FIG.  2   ) provided in the bidirectional switching converter  110  may maintain a target level, for example, a second target level set with respect to the flying capacitor voltage. 
     The controller  120  may generate switching signals for controlling a switching operation of the bidirectional switching converter  110  in each switching mode. For example, the controller  120  may receive sensing currents and voltages from the bidirectional switching converter  110 , and generate switching signals based on the sensing currents and the voltages. The controller  120  may generate a first pulse width modulation (PWM) signal and a second PWM signal based on the sensing currents and the voltages, generate a first switching signal and a second switching signal based on the first PWM signal and the second PWM signal, and provide the first switching signal and the second switching signal to the bidirectional switching converter  110 . At least two switching elements among a plurality of switching elements provided in the bidirectional switching converter  110  may be turned on and off based on the first switching signal, and at least two other switching elements may be turned on and turned off based on the second switching signal. 
     In some example embodiments, in the buck-boost mode, the controller  120  may control the flying capacitor voltage to maintain the second target voltage by adjusting an on period and an off period of each of (or alternatively, at least one of) the first switching signal and the second switching signal, based on whether an average value of an inductor current flowing through an inductor L provided in the bidirectional switching converter  110  is positive or negative. 
     The controller  120  may determine whether the average value of the inductor current is positive or negative based on the sensed currents from the bidirectional switching converter  110 . In the buck mode and the boost mode, the controller  120  may control the inductor current flowing through the inductor L to flow in one direction. For example, in the buck mode, the controller  120  may control the inductor current to flow in a forward direction (e.g., from a first end of the inductor L to a second end) and not to flow in a reverse direction (e.g., from the second end of the inductor L to first end), and in the boost mode, may control the inductor current to flow in the reverse direction and not to flow in the forward direction. The controller  120  may control the inductor current to flow in both directions in the buck-boost mode. When the inductor current flows in the forward direction, the inductor current has a positive value, and when the inductor current flows in the reverse direction, the inductor current may have a negative value. 
     The controller  120  may determine whether the average value of the inductor current is positive or negative for a unit time, when the average value of the inductor current is positive, generate the first switching signal based on the first PWM signal, and generate the second switching signal based on the second PWM signal. When the average value of the inductor current is negative, the controller  120  may generate the first switching signal based on the second PWM signal and generate the second switching signal based on the first PWM signal. 
     As such, generating the first switching signal and the second switching signal based on whether the average value of the inductor current is positive or negative will be described below with reference to  FIGS.  2  to  11   . 
     In some example embodiments, the charger IC  100  may support at least one function among various functions such as an under-voltage lockout (UVLO) function, an over-current protection (OCP) function, an over-voltage protection (OVP) function, a soft-start function to reduce an inrush current, a foldback current limit function, a hiccup mode function for short circuit protection, an over-temperature protection (OTP) function, etc. 
     In some example embodiments, the electronic device  10  may support wired charging and wireless charging, and may include a wired power interface  310  and a wireless power interface  320  respectively for wired charging and wireless charging. In some example embodiments, the wired power interface  310  may include a wired charging circuit, and the wireless power interface  320  may include a wireless charging circuit. For example, each of (or alternatively, at least one of) the wired charging circuit and the wireless charging circuit may include a rectifier, a regulator, etc. 
     The charger IC  100  may receive a first input voltage CHGIN from the wired power interface  310  and/or a second input voltage WCIN from the wireless power interface  320 , and charge the battery  200  based on the first input voltage CHGIN and/or the second input voltage WCIN in the buck mode. 
     The charger IC  100  may provide power to the wired power interface  310  and/or the wireless power interface  320  based on the voltage of the battery  200  in the reverse boost mode. 
     The charger IC  100  may receive the first input voltage CHGIN from the wired power interface  310 , and charge the battery  200  based on the first input voltage CHGIN or provide power to the wireless power interface  320  based on the first input voltage CHGIN in the buck-boost mode. Alternatively, the charger IC  100  may receive the second input voltage WCIN from the wireless power interface  320  and charge the battery  200  based on the second input voltage WCIN or provide power to the wired power interface  310  based on the second input voltage WCIN. Charging the battery  200  and providing power to the wired power interface  310  or the wireless power interface  320  may be simultaneously or contemporaneously performed. 
     The charger IC  100  may also provide power to the wireless power interface  320  based on the first input voltage CHGIN and the voltage of the battery  200  or provide power to the wired power interface  310  based on the second input voltage WCIN and the voltage of the battery  200 . 
     For example, a travel adapter (TA) or an auxiliary battery may be electrically connected to the wired power interface  310 . The TA may convert power supplied from alternating current (AC) about 110 V to about 220 V which is household power or another power supply means (e.g., a computer) into direct current (DC) power necessary for charging the battery  200 , and provide the DC power to the electronic device  10 . In the buck mode or the buck-boost mode, the charger IC  100  may charge the battery  200  using the first input voltage CHGIN received from the TA or the auxiliary battery, or provide power to the wireless power interface  320 . 
     For example, an on the go (OTG) device (e.g., an OTG USB device, etc.) may be connected to the wired power interface  310 , and the charger IC  100  may provide power to the OTG device through the wired power interface  310 . In this regard, the charger IC  100  may provide power to the OTG device based on the voltage of the battery  200  in the boost mode, or provide power to the OTG device simultaneously or contemporaneously while charging the battery  200  based on the second input voltage WCIN of the wireless power interface  320  in the buck mode. 
     For example, a wireless power receiving circuit or a wireless power transmitting circuit may be connected to the wireless power interface  320 . The charger IC  100  may charge the battery  200  using the second input voltage WCIN received from the wireless power receiving circuit in the buck mode or the buck-boost mode. Alternatively, the charger IC  100  may provide power to the wireless power transmitting circuit through the wireless power interface  320 . The charger IC  100  may provide power to the wireless power transmitting circuit based on the voltage of the battery  200  in the boost mode, or provide power to the wireless power transmitting circuit simultaneously or contemporaneously while charging the battery  200  based on the first input voltage CHGIN of the wired power interface  310  in the buck mode. 
     As described above, because the electronic device  10  supports wired and wireless charging, the charger IC  100  may operate in the plurality of switching modes including the buck mode, the boost mode, and the buck-boost mode in order to support wired charging and/or wireless charging, wired charging-wireless power supply, and wireless charging-wired power supply. 
     As described above, in the charger IC  100  according to some example embodiments, the bidirectional switching converter  110  may be implemented as the 3-level DC-DC converter including the plurality of switching elements, the flying capacitor (e.g., CF in  FIG.  2   ), and the inductor L. The charger IC  100  may maintain the flying capacitor voltage at the second target level by changing the control of switching operations of the plurality of switching elements according to whether the average value of the inductor current flowing through the inductor L is positive or negative in the buck-boost mode. This may be referred to as flying capacitor balancing. In this way, an operation transition may be seamlessly performed between the buck converting operation and the boost converting operation while flying capacitor balancing is maintained in the buck-boost mode, 
       FIG.  2    is a circuit diagram illustrating the bidirectional switching converter  110  according to some example embodiments. 
     Referring to  FIG.  2   , the bidirectional switching converter  110  may include an input/output selection circuit  111  and a switching circuit  112 . 
     The input/output selection circuit  111  may include a first input transistor QI 1  and a second input transistor QI 2 . The first input transistor QI 1  and the second input transistor QI 2  may be connected in parallel to a first node N 1 . The first node N 1  may be referred to as a first input/output node. 
     The first input voltage CHGIN may be applied to the first input transistor QI 1  or an OTG device may be connected to the first input transistor QI 1 . The second input voltage WCIN may be applied to the second input transistor QI 2  or a wireless power transmitting circuit may be connected to the second input transistor QI 2 . 
     The first input transistor QI 1  may be turned on and off in response to a first input control signal SI 1 , and the second input transistor QI 2  may be turned on and turned off in response to a second input control signal SI 2 . For example, when the first input voltage CHGIN is applied to the first input transistor QI 1  or the OTG device is connected to the first input transistor QI 1 , the first input control signal SI 1  may have an active level, and the first input transistor QI 1  may be turned on in response to the first input control signal SI 1 . When the second input voltage WCIN is applied to the second input transistor QI 2  or the wireless power transmitting circuit is connected to the second input transistor QI 2 , the second input control signal SI 2  may have an active level, and the second input transistor QI 2  may be turned on in response to the second input control signal SI 2 . The first input control signal SI 1  and the second input control signal SI 2  may be received from the controller ( 120  of  FIG.  1   ). 
     The switching circuit  112  may include a plurality of switching elements, for example, a first switching transistor Q 1 , a second switching transistor Q 2 , a third switching transistor Q 3  and a fourth switching transistor Q 4 , the inductor L, a first capacitor Ci, a second capacitor Co, a third capacitor CF, and a current sensor CS. 
     The first capacitor Ci may stabilize an input voltage applied to the first input node N 1  when the switching circuit  112  performs a buck converting operation, and rectify an output voltage of square waves output to the first node N 1  into a DC voltage when the switching circuit  112  performs a boost converting operation. 
     The first switching transistor Q 1 , the second switching transistor Q 2 , the third switching transistor Q 3 , and the fourth switching transistor Q 4  may be connected in series to the first node N 1 . A first end of the first switching transistor Q 1  may be connected to the first node N 1 , and a second end thereof may be connected to a second node N 2 . A first end of the second switching transistor Q 2  may be connected to the second node N 2 , and a second end thereof may be connected to a third node N 3 . A first end of the third switching transistor Q 3  may be connected to the third node N 3 , and a second end thereof may be connected to a fourth node N 4 . A first end of the fourth switching transistor Q 4  may be connected to the fourth node N 4 , and a second end thereof may be connected to a fifth node N 5 . A ground voltage may be applied to the fifth node N 5 . 
     The first switching transistor Q 1  may be turned on and turned off in response to a first switching voltage VG 1 , the second switching transistor Q 2  may be turned on and turned off in response to a second switching voltage VG 2 , the third switching transistor Q 3  may be turned on and turned off in response to a third switching voltage VG 3 , and the fourth switching transistor Q 4  may be turned on and turned off in response to a fourth switching voltage VG 4 . 
     The first to fourth switching voltages VG 1 , VG 2 , VG 3 , and VG 4  may be periodic signals having a frequency, and the frequency may vary according to a step-down ratio during a buck converting operation and a step-up ratio during a boost converting operation. 
     The first switching voltage VG 1  and the fourth switching voltage VG 4  may be complementary signals, and the second switching voltage VG 2  and the third switching voltage VG 3  may be complementary signals. Accordingly, the first switching transistor Q 1  and the fourth switching transistor Q 4  may perform a complementary switching operation, and the second switching transistor Q 2  and the third switching transistor Q 3  may perform a complementary switching operation. 
     A third capacitor CF may be connected to the second node N 2  and the fourth node N 4 . In other words, a first end of the capacitor C F  may be connected to the second end of the first switching transistor Q 1  and the first end of the second switching transistor Q 2 , and a second end of the capacitor CF may be connected to the second end of the third switching transistor Q 3  and the first end of the fourth switching transistor Q 4 . The capacitor C F  may be referred to as a flying capacitor. 
     The inductor L may be connected to the third node N 3  and a sixth node N 6 . The sixth node N 6  may be referred to as a second input/output node. The second capacitor Co may be connected to the sixth node N 6 . 
     The inductor L may store energy generated by an inductor current IL flowing through the inductor L, and discharge the stored energy. According to the buck converting operation and the boost converting operation of the bidirectional switching converter  110 , the inductor current IL may flow in a direction from the third node N 3  to the sixth node N 6 , for example, in a forward direction, or the inductor current IL may flow in a direction from the sixth node N 6  node to the third node N 3 , for example, in a reverse direction. It may be assumed that when the inductor current IL flows in the forward direction, a value of the inductor current IL is positive, and when the inductor current IL flows in the reverse direction, the value of the inductor current IL is negative. 
     The current sensor CS may be a bidirectional current sensor that senses the inductor current IL. The current sensor CS may provide a sensing current Isen to the controller ( 120  of  FIG.  1   ). One current sensor CS sensing the inductor current IL is illustrated in  FIG.  2    but the inventive concepts are not limited thereto, and the switching circuit  112  may further include at least one current sensor sensing at least one current flowing through at least one of the first switching transistor Q 1 , the second switching transistor Q 2 , the third switching transistor Q 3 , or the fourth switching transistor Q 4 . 
     The respective voltages of the first node N 1 , the second node N 2 , the third node N 3 , and the fourth node N 4 , for example, a voltage VBYP, a voltage VCH, a voltage VL, and a voltage VCL, may be provided to the controller ( 120  in  FIG.  1   ), and the controller  120  may generate the first to fourth switching voltages VG 1  to VG 4  based on a plurality of voltages and at least one sensing current provided from the bidirectional switching converter  110 . 
     The bidirectional switching converter  110  may operate as a buck converter in a partial period of the buck mode or the buck-boost mode, and may generate a first output voltage by stepping-down the first voltage VBYP. Here, the first voltage VBYP may be the first input voltage CHGIN and/or the second input voltage WCIN. The first output voltage may be output as a system voltage V SYS  through the sixth node N 6 , that is, the second input/output node. Also, the battery  200  may be charged based on the first output voltage. The battery  200  may include an internal resistor R INT , and a battery voltage V BAT  of the charged battery  200  may be the same as the first output voltage. 
     The bidirectional switching converter  110  may operate as a boost converter in another partial period of the boost mode or the buck-boost mode, and may generate an output voltage, for example, a second output voltage, by boosting the battery voltage V BAT . The second output voltage may be output through the first node N 1 , that is, the first input/output node, and the bidirectional switching converter  110  may provide power to the wired power interface ( 310  in  FIG.  1   ) and/or the wireless power interface ( 320  in  FIG.  1   ) based on the second output voltage. 
       FIGS.  3 A and  3 B  illustrate a power path during a buck converting operation of the bidirectional switching converter  110  according to some example embodiments. It is assumed that the first input voltage CHGIN is applied to the input/output selection circuit  111  in  FIG.  3 A , and that the first input voltage CHGIN is applied to the input/output selection circuit  111 , and a wireless power transmitting circuit TX is connected to the input/output selection circuit  111  in  FIG.  3 B . 
     Referring to  FIG.  3 A , the first input voltage CHGIN may be applied from a first input power source, for example, the wired power interface  310  of  FIG.  1   , and the first input transistor QI 1  may be turned on in response to the first input control signal SI 1  having an active level. In this regard, the second input control signal SI 2  may have an inactive level, and the second input transistor QI 2  may be turned off in response to the second input control signal SI 2 . 
     The bidirectional switching converter  110  may operate as a buck converter in a forward direction. The bidirectional switching converter  110  may perform a switching operation based on the first input voltage CHGIN, and accordingly, a first power path (a forward buck power path) may be formed in the forward direction. Current supplied from the first input power source may be supplied to the battery  200  and/or an internal system of the electronic device  10  through the inductor L. As described above, the bidirectional switching converter  110  may charge the battery  200  and supply power to the internal system of the electronic device ( 10  in  FIG.  1   ) by performing the buck converting operation. 
     Referring to  FIG.  3 B , the wired power interface ( 310  in  FIG.  1   ) as well as the wireless power interface ( 320  in  FIG.  1   ), for example, the wireless power transmitting circuit TX, may be connected to the input/output selection circuit  111 , and the second input transistor QI 2  may be turned on in response to the second input control signal SI 2  having an active level. 
     The first input power source may provide power to the wireless power transmitting circuit TX through the first input transistor QI 1  and the second input transistor QI 2 . Accordingly, in addition to the first power path formed according to the buck converting operation of the bidirectional switching converter  110 , the power path may be formed in a direction from the wired power interface  310  to the wireless power interface  320  in the input/output selection circuit  111 . 
       FIGS.  3 A and  3 B  illustrate a forward buck power path formed when the bidirectional switching converter  110  performs a forward buck converting operation based on the first input voltage CHGIN provided from the wired power interface  310 . However, the inventive concept is not limited thereto, and the bidirectional switching converter  110  may perform the forward buck converting operation based on the second input voltage WCIN provided from the wireless power interface  320 . The forward buck power path may be formed based on the second input voltage WCIN, and the power path may be formed in a direction from the wireless power interface  320  to the wired interface  310  in the input/output selection circuit  111 . 
       FIGS.  4 A and  4 B  illustrate a power path during a boost converting operation of the bidirectional switching converter  110  according to some example embodiments. It is assumed that the wireless power transmitting circuit TX is connected to the input/output selection circuit  111  in  FIG.  4 A , and that the first input voltage CHGIN is applied to the input/output selection circuit  111  and the wireless power transmitting circuit TX is connected to the input/output selection circuit  111  in  FIG.  4 B . 
     Referring to  FIG.  4 A , the wireless power transmitting circuit TX may be connected to the input/output selection circuit  111 . The second input transistor QI 2  may be turned on in response to the second input control signal SI 2  having an active level. The first input control signal SI 1  may have an inactive level, and the first input transistor QI 1  may be turned off in response to the first input control signal SI 1 . 
     The bidirectional switching converter  110  may operate as a boost converter in a reverse direction. The bidirectional switching converter  110  may perform a switching operation based on an input voltage provided to the battery  200 , for example, the battery voltage V BAT , and accordingly, a second power path, for example, a reverse boost power path, may be formed in the reverse direction. Current supplied from the battery  200  may be provided to the wireless power transmitting circuit TX through the inductor L. 
     In some example embodiments, an OTG device may be connected to the input/output selection circuit  111 , and the current supplied from the battery  200  may be provided to the OTG device. 
     Referring to  FIG.  4 B , the wireless power transmitting circuit TX may be connected to the input/output selection circuit  111 , and the first input voltage CHGIN may be applied to the input/output selection circuit  111 . The first input transistor QI 1  and the second input transistor QI 2  may be turned on in response to the first input control signal SI 1  and the second input control signal SI 2  having an active level. 
     Current supplied from a first input power source providing the first input voltage CHGIN, for example, the wired power interface  310  of  FIG.  1   , may be provided to the wireless power transmitting circuit TX. Accordingly, in addition to the second power path formed according to the boost converting operation of the bidirectional switching converter  110 , a power path may be formed in a direction from the wired power interface  310  to the wireless power interface  320  in the input/output selection circuit  111 . 
     In some example embodiments, the OTG device may be connected to the input/output selection circuit  111 , and the second input voltage WCIN may be applied from the wireless power interface ( 320  of  FIG.  1   ). Current supplied from a second power source may be provided to the OTG device based on the current supplied from the battery  200  and the second input voltage WCIN. 
       FIGS.  5 A and  5 B  are timing diagrams when the bidirectional switching converter  110  performs a buck converting operation according to some example embodiments.  FIG.  5 A  is a waveform diagram when a duty ratio D is more than 0.5, and  FIG.  5 B  is a waveform diagram when the duty ratio D is equal to or less than 0.5.  FIGS.  5 A and  5 B  will be described with reference to  FIG.  2    together. 
     Referring to  FIGS.  2  and  5 A , the bidirectional switching converter  110  may perform the buck converting operation based on the first to fourth switching voltages VG 1  to VG 4 . For example, when the first switching voltage VG 1  is at an active level (e.g., logic high), the first switching transistor Q 1  may be turned on, and when the first switching voltage VG 1  is at an inactive level (e.g., logic low), the first switching transistor Q 1  may be turned off. 
     The first to fourth switching voltages VG 1  to VG 4  are signals of the same frequency. A period in which each of (or alternatively, at least one of) the first to fourth switching voltages VG 1  to VG 4  has the active level and the inactive level within one period T may be varied based on a ratio of an input voltage to an output voltage and feedback voltages of the switching circuit  112 . 
     The first switching voltage VG 1  and the fourth switching voltage VG 4  are complementary signals, and the second switching voltage VG 2  and the third switching voltage VG 3  are complementary signals. Accordingly, when the first switching transistor Q 1  is turned on, the fourth switching transistor Q 4  may be turned off, and when the first switching transistor Q 1  is turned off, the fourth switching transistor Q 4  may be turned on. When the second switching transistor Q 2  is turned on, the third switching transistor Q 3  may be turned off, and when the second switching transistor Q 2  is turned off, the third switching transistor Q 3  may be turned on. 
     At a time t 0 , when the first switching transistor Q 1  and the second switching transistor Q 2  are turned on, an input voltage, for example, the voltage VBYP of the first node N 1 , may be applied to the third node N 3 , the voltage VL of the third node N 3  may have the same voltage level as that of the voltage VBYP, and the inductor current IL may increase. 
     At a time t 1 , when the second switching transistor Q 2  is turned off and the third switching transistor Q 3  is turned on, current may flow to the inductor L through the first switching transistor Q 1 , a third capacitor C F , and the third switching transistor Q 3 . The voltage VL of the third node N 3  may have a voltage level reduced by a voltage VCF between both ends of the third capacitor C F  from the voltage VBYP. For example, when the voltage VCF is ½ times the voltage VBYP (e.g., ½×VBYP), the voltage VL may have the same level (e.g., ½×VBYP) as that of the voltage VCF. Due to a reduction in the level of the voltage VL, the inductor current IL may be reduced. 
     At a time t 2 , when the third switching transistor Q 3  is turned off and the second switching transistor Q 2  is turned on, the voltage VL of the third node N 3  may have the same level as that of the voltage VBYP, and the inductor current IL may increase. 
     At a time t 3 , when the fourth switching transistor Q 4  is turned on and the first switching transistor Q 1  is turned off, the current may flow to the inductor L through the fourth switching transistor Q 4 , the third capacitor CF, and the second switching transistor Q 2 . The voltage VL of the third node N 3  may have the same level (e.g., ½*VBYP) as that of the voltage VCF, and due to a reduction in the level of the voltage VL, the inductor current IL may be reduced. 
     Referring to  FIG.  5 B , when the fourth switching transistor Q 4  and the third switching transistor Q 3  are turned on at the time t 0 , a ground voltage may be applied to the third node N 3  and the voltage VL of the third node N 3  may have the same level as that of the ground voltage. The inductor current IL generated by the energy charged in the inductor L may be output, and the inductor current IL may be reduced. 
     At the time t 1 , when the fourth switching transistor Q 4  is turned off and the first switching transistor Q 1  is turned on, the current may flow to the inductor L through the first switching transistor Q 1 , the third capacitor CF, and the third switching transistor Q 3 . The voltage VL of the third node N 3  may have a level reduced by the voltage VCF between both ends of the third capacitor C F  from the voltage VBYP. For example, when the voltage VCF is ½ times the voltage VBYP (e.g., ½*VBYP), the voltage VL may have a level (e.g., ½*VBYP) that is ½ times the voltage VBYP. Due to an increase in the level of the voltage VL, the inductor current IL may increase. 
     At the time t 2 , when the fourth switching transistor Q 4  is turned on and the first switching transistor Q 1  is turned off, the voltage VL of the third node N 3  may have the same level as that of the ground voltage, and the inductor current IL may be reduced. 
     At the time t 3 , when the second switching transistor Q 2  is turned on and the third switching transistor Q 3  is turned off, the current may flow to the inductor L through the fourth switching transistor Q 4 , the third capacitor C F , and the second switching transistor Q 2 . The voltage VL of the third node N 3  may have the same level (e.g., ½*VBYP) as that of the voltage VCF, and the inductor current IL may increase. 
     As described above with reference to  FIGS.  5 A and  5 B , switching operations of the first to fourth switching transistors Q 1  to Q 4  may be repeated for one period T, and accordingly, an output voltage obtained by stepping-down the input voltage, for example, the voltage VBYP, may be output through the sixth node N 6 . Here, a voltage drop rate may be determined according to the duty ratio D. 
     Meanwhile, in the bidirectional switching converter  110  implemented as a 3-level DC-DC converter, the voltage VL may be determined by the voltage VBYP and the voltage VCF as described above. The controller  120  may reduce a ripple of the output voltage, by controlling the voltage VCF between both ends of the third capacitor C F  to be an intermediate value of the voltage VBYP. As described above, controlling the voltage VCF between both ends of the third capacitor C F  to the intermediate value of the voltage VBYP will be referred to as flying capacitor balancing. 
     In the buck mode, the inductor current IL flows in a forward direction, and in the boost mode, the inductor current IL flows in a reverse direction. However, in the buck-boost mode, the inductor current IL may flow in both directions. In the buck-boost mode, the controller  120  may control the bidirectional switching converter  110  to perform a switching operation according to the buck mode or the boost mode. However, depending on the direction of the inductor current IL, the bidirectional switching converter  110  may perform a buck converting operation or a boost converting operation. 
     For example, in a case where the first to fourth switching voltages VG 1  to VG 4  are provided as shown in  FIGS.  5 A and  5 B , when the inductor current IL flows in the forward direction, the bidirectional switching converter  110  may perform the buck converting operation in the forward direction, and when the inductor current IL flows in the reverse direction, the bidirectional switching converter  110  may perform the boost converting operation in the reverse direction. 
     The bidirectional switching converter  110  may perform the buck converting operation in the forward direction based on the first input voltage applied to the first node N 1 , for example, the voltage VBYP, and generate the first output voltage output to the sixth node N 6 . In addition, the bidirectional switching converter  110  may perform the boost converting operation in the reverse direction based on the input voltage applied to the sixth node N 6 , for example, the battery voltage V BAT , and generate the second output voltage output to the first node N 1 . 
     Meanwhile, when the bidirectional switching converter  110  performs the buck converting operation in the forward direction and the boost converting operation in the reverse direction based on the first to fourth switching voltages VG 1  to VG 4  as described above, flying capacitor balancing may be difficult. However, as will be described below, the controller  120  according to some example embodiments may perform flying capacitor balancing by adjusting a period in which each of (or alternatively, at least one of) the first to fourth switching voltages VG 1  to VG 4  has the active level and the inactive level according to the direction of the inductor current IL when the bidirectional switching converter  110  performs the buck converting operation in the forward direction and the boost converting operation in the reverse direction. 
       FIG.  6    is a block diagram schematically illustrating the controller  120  controlling the bidirectional switching converter  110  according to some example embodiments. 
     Referring to  FIG.  6   , the controller  120  may include a modulator  121 , a PWM logic  122 , a gate driver  123 , and a sensing circuit  124 . 
     The modulator  121  may generate a first PWM signal PWM 1  and a second PWM signal PWM 2  based on voltages and sensing current provided from the bidirectional switching converter ( 110  of  FIG.  1   ). In some example embodiments, the modulator  121  may generate the first PWM signal PWM 1  and the second PWM signal PWM 2  based on the voltages VBYP and VCF and the sensing current Isen, for example, the inductor current (IL in  FIG.  2   ), provided from the bidirectional switching converter  110 . 
       FIG.  7    is a circuit diagram schematically illustrating the modulator  121  of  FIG.  6   . 
     Referring to  FIG.  7   , the modulator  121  may include an error detection circuit  21  and a comparison circuit  22 . 
     The error detection circuit  21  may detect an error of am output voltage, e.g., a first error voltage VE_VO and an error of a capacitor voltage, e.g., a second error voltage VE_VCF, based on the voltage VBYP and the voltage VCF. The error detection circuit  21  may include a plurality of controllers, for example, a proportional integral (PI) controller  21 _ 1 , a proportional integral derivative (PID) controller  21 _ 2 , a proportional (P) controller  21 _ 4 , and a plurality of adders  21 _ 3 ,  21 _ 5  and  21 _ 6 . 
     An error of the voltage VBYP according to a difference between the voltage VBYP and the reference voltage VREF may be output from the adder  21 _ 3 . The PID controller  21 _ 2  may generate a control value obtained by summing a proportional value, an integral value, and a differential value of the error of the voltage VBYP. A current error according to a difference between the control value output from the PID controller  21 _ 2  and the sensing current Isen may be output from the adder  21 _ 5 . The PI controller  21 _ 1  may output the first error voltage VE_VO obtained by adding a proportional value and an integral value of the current error. 
     An error of the voltage VCF according to a difference between the voltage VCF and a voltage (e.g., 0.5*VIN) corresponding to ½ times the input voltage VIN may be output from the adder  21 _ 6 . The P controller  21 _ 4  may output a proportional value of the error of the voltage VCF as the second error voltage VE_VCF. 
     The comparison circuit  22  may include a first comparator  22 _ 1 , a second comparator  22 _ 2 , and a plurality of adders  22 _ 3  and  22 _ 4 . The adder  22 _ 3  may output the sum of the first error voltage VE_VO and the second error voltage VE_VCF as a first comparison voltage VPOS. The adder  22 _ 4  may output a difference between the first error voltage VE_VO and the second error voltage VE_VCF as a second comparison voltage VNEG. A voltage level of the first error voltage VE_VO may be higher than a voltage level of the second error voltage VE_VCF, and a voltage level of the first comparison voltage VPOS may be higher than a voltage level of the second comparison voltage VNEG. 
     The first comparator  22 _ 1  may output the first PWM signal PWM 1  by comparing a first ramp signal RAMP 1  and the first comparison voltage VPOS. For example, when a level of the first ramp signal RAMP 1  is lower than that of the first comparison voltage VPOS, the first comparator  22 _ 1  may output the first PWM signal PWM 1  having an active level, and when the level of the first ramp signal RAMP 1  is equal to or higher than that of the first comparison voltage VPOS, the first comparator  22 _ 1  may output the first PWM signal PWM 1  having an inactive level. 
     The second comparator  22 _ 2  may output the second PWM signal PWM 2  by comparing a second ramp signal RAMP 2  and the second comparison voltage VNEG. For example, when a level of the second ramp signal RAMP 2  is lower than that of the second comparison voltage VNEG, the second comparator  22 _ 2  may output the second PWM signal PWM 2  having an active level, and when the level of the second ramp signal RAMP 2  is equal to or higher than that of the second comparison voltage VNEG, the second comparator  22 _ 2  may output the second PWM signal PWM 2  having an inactive level. 
       FIG.  8    is a timing diagram illustrating the first and second PWM signals PWM 1  and PWM 2  generated by the modulator  121  of  FIG.  7   . 
     Referring to  FIG.  8   , a voltage level of the first comparison voltage VPOS in a first period T 1  is higher than the voltage level thereof in a second period T 2 , and a voltage level of the second comparison voltage VNEG in the first period T 1  is lower than the voltage level thereof in the second period T 2 . When a second error voltage VE_VCF in the second period T 2  is lower than in the first period T 1 , the first comparison voltage VPOS may be reduced and the second comparison voltage VNEG may increase. As another example, when the first error voltage VE_VO in the second period T 2  is lower than in the first period T 1 , both the first comparison voltage VPOS and the second comparison voltage VNEG may be reduced. 
     The first PWM signal PWM 1  may be generated based on a comparison result of the first comparison voltage VPOS and the first ramp signal RAMP 1 , and the second PWM signal PWM 2  may be generated based on a comparison result of the second comparison voltage VNEG and the second ramp signal RAMP 2 . 
     Accordingly, a period Ta 1 ′ in which the first PWM signal PWM 1  has an active level in the second period T 2  may be reduced compared to a period Ta 1  in which the first PWM signal PWM 1  has an active level in the first period T 1 , and a period Tua 1 ′ in which the first PWM signal PWM 1  has an inactive level in the second period T 2  may be increased compared to a period Tua 1  in which the first PWM signal PWM 1  has an inactive level in the first period T 1 . 
     A period Ta 2 ′ in which the second PWM signal PWM 2  has an active level in the second period T 2  may be increased compared to a period Ta 2  in which the second PWM signal PWM 2  has an active level in the first period T 1 , and a period Tua 2 ′ in which the second PWM signal PWM 2  has an inactive level in the second period T 2  may be reduced compared to a period Tua 2  in which the second PWM signal PWM 2  has an inactive level in the first period T 1 . As such, based on a change in voltage level of each of (or alternatively, at least one of) the first comparison voltage VPOS and the second comparison voltage VNEG, the periods in which each of (or alternatively, at least one of) the first PWM signal PWM 1  and the second PWM signal PWM 2  has an active level and an inactive period may be changed. 
     Subsequently, referring to  FIG.  6   , the PWM logic  122  may generate a first switching signal SS 1  and a second switching signal SS 2  based on the first PWM signal PWM 1 , the second PWM signal PWM 2 , and a direction signal POSD_D. 
       FIG.  9    is a circuit diagram schematically illustrating the PWM logic  122  of  FIG.  6   . 
     Referring to  FIG.  9   , the PWM logic  122  may include a first de-multiplexer (DMUX)  122 _ 1  and a second de-multiplexer  122 _ 2 . The first de-multiplexer  122 _ 1  and the second de-multiplexer  122 _ 2  may output respectively output signals, for example, the first switching signal SS 1  and the second switching signal SS 2 , based on the direction signal POS_D as a selection input SEL. 
     The first de-multiplexer  122 _ 1  may receive the first PWM signal PWM 1  as a first input IN 1  and the second PWM signal PWM 2  as a second input IN 2 . The first de-multiplexer  122 _ 1  may output one of the first input IN 1  and the second input IN 2  as the first switching signal SS 1  based on the direction signal POS_D. For example, when the direction signal POS_D is at a logic high, the first de-multiplexer  122 _ 1  may output the first input IN 1 , for example, the first PWM signal PWM 1 , as the first sensing signal SS 1 , when the direction signal POS_D is at a logic low, the first de-multiplexer  122 _ 1  may output the second input IN 2 , for example, the second PWM signal PWM 2 , as the first switching signal SS 1 . 
     The second de-multiplexer  122 _ 2  may receive the second PWM signal PWM 2  as the first input IN 1 , and receive the first PWM signal PWM 1  as the second input IN 2 . The second de-multiplexer  122 _ 2  may output one of the first input IN 1  and the second input IN 2  as the second switching signal SS 2  based on the direction signal POS_D. For example, when the direction signal POS_D is at a logic high, the second de-multiplexer  122 _ 2  may output the first input IN 1 , e.g., the second PWM signal PWM 2 , as the first switching signal SS 1 , and when the direction signal POS_D is at a logic low, the second de-multiplexer  122 _ 2  may output the second input IN 2 , for example, the first PWM signal PWM 1 , as the second sensing signal SS 1 . 
     Accordingly, when the direction signal POS_D is at a logic high, the PWM logic  122  may output the first PWM signal PWM 1  as the first switching signal SS 1  and output the second PWM signal PWM 2  as the second switching signal SS 2 , and when the direction signal POS_D is at a logic low, the PWM logic  122  may output the second PWM signal PWM 2  as the first switching signal SS 1 , and the first PWM signal PWM 1  as the second switching signal SS 2 . 
     Subsequently, referring to  FIG.  6   , the gate driver  123  may generate the first to fourth switching voltages VG 1 , VG 2 , VG 3 , and VG 4  based on the first switching signal SS 1  and the second switching signal SS 2 . 
     The gate driver  123  may convert a voltage level of the first switching signal SS 1  to generate the first switching voltage VG 1 , and invert the first switching signal SS 1  and convert the voltage level to generate the fourth switching voltage VG 4 . For example, the gate driver  123  may convert a logic low level of the first switching signal SS 1  to a voltage level suitable for turning off the first switching transistor (Q 1  in  FIG.  2   ), and convert the logic high level to a voltage level suitable for turning on the first switching transistor Q 1 . 
     The gate driver  123  may convert a voltage level of the second switching signal SS 2  to generate the second switching voltage VG 2 , and invert the second switching signal SS 2  and convert the voltage level to generate the third switching voltage VG 3 . 
     As described with reference to  FIG.  6   , the first switching signal SS 1  and the second switching signal SS 2  are changed according to the direction signal POS_D, and thus, the first to fourth switching voltages VG 1 , VG 2 , VG 3 , and VG 4  may be changed. 
     In some example embodiments, the gate driver  123  may receive an over-current control signal OCP and a zero current control signal ZCS from the sensing circuit  124 , and generate or block the first to fourth switching voltages VG 1 , VG 2 , VG 3 , and VG 4 , based on the over-current control signal OCP and the zero current control signal ZCS. 
     For example, when the inductor current IL is reduced to a certain value, for example, ‘0’, when the bidirectional switching converter ( 110  in  FIG.  1   ) operates in a buck-mode, the sensing circuit  124  may generate the zero current control signal ZCS. The gate driver  123  may block generation of the first to fourth switching voltages VG 1 , VG 2 , VG 3 , and VG 4 . Accordingly, it is possible to prevent or reduce the inductor current IL from flowing in a reverse direction. 
     When the inductor current IL increases to a certain value, for example, ‘0’, when the bidirectional switching converter  110  operates in a boost-mode, the sensing circuit  124  may generate the over-current control signal OCP. The gate driver  123  may block the generation of the first to fourth switching voltages VG 1 , VG 2 , VG 3 , and VG 4 . Accordingly, it is possible to prevent or reduce the inductor current IL from flowing in a forward direction. 
     The sensing circuit  124  may generate the direction signal POS_D based on a plurality of voltages (e.g., the voltages VBYP, VCH, VCL, and VL) and the sensing current Isen provided from the bidirectional switching converter  110 . Also, the sensing circuit  124  may generate the over-current control signal OCP and the zero current control signal ZCS. 
     For example, the sensing circuit  124  may average the sensing current Isen from which the inductor current IL is sensed for each certain unit time to calculate an average value of the inductor current IL, generate the direction signal POS_D at a logic high when the average value is positive, and generate the direction signal POS_D at a logic low when the average value is negative. 
     However, the inventive concept is not limited thereto, and the sensing circuit  124  may generate the direction signal POS_D according to various methods. For example, the sensing circuit  124  may generate the over-current control signal OCP and the zero current control signal ZCS with respect to each of (or alternatively, at least one of) the first to fourth switching transistors (Q 1  to Q 4  in  FIG.  2   ), and generate the direction signal POS_D based on the over-current control signals OCP and the zero current control signals ZCS. 
     The sensing circuit  124  may detect intermediate points at which the inductor current IL is charged and discharged based on the first PWM signal PWM 1  and the second PWM signal PWM 2 , and sense the third and fourth switching transistors Q 3  and Q 4  at the intermediate points when the direction signal POS_D is at a logic high. The sensing circuit  124  may change the direction signal POS_D from a logic high to a logic low when the zero current control signal ZCS is generated with respect to the third and fourth switching transistors Q 3  and Q 4 . Also, the sensing circuit  124  may sense currents of the first and second switching transistors Q 1  and Q 2  at the intermediate points when the direction signal POS_D is at a logic low. When the over-current control signal OCP is generated with respect to the first and second switching transistors Q 1  and Q 2 , the sensing circuit  124  may change the direction signal POS_D from a logic low to a logic high. 
       FIGS.  10 A and  10 B  are timing diagrams of signals of the bidirectional switching converter  110  and the controller  120  according to some example embodiments. In  FIG.  10 A , it is assumed that the voltage VCF is less than a target voltage T_VCF, and in  FIG.  10 B , it is assumed that the voltage VCF is higher than the target voltage T_VCF. 
     Referring to  FIG.  10 A , when the voltage VCF is less than the target voltage T_VCF, the first comparison voltage VPOS may be higher than the second comparison voltage VNEG. In the period T 1 , an average value IL_AVG of an inductor current may be positive, and in the period T 2 , the average value IL_AVG of the inductor current may be negative. As described with reference to  FIG.  7   , the first PWM signal PWM 1  may be generated based on the first ramp signal RAMP 1  and the first comparison voltage VPOS, and the second PWM signal PWM 2  may be generated based on the second ramp signal RAMP 2  and the second comparison voltage VNEG. 
     Because the average value IL_AVG of the inductor current in the period T 1  is positive, the direction signal POS_D is at a logic high, and in response to the direction signal POS_D at a logic high, the PWM logic ( 122  in  FIG.  6   ) may generate the first switching signal SS 1  based on the first PWM signal PWM 1 , and generate the second switching signal SS 2  based on the second PWM signal PWM 2 . 
     As described with reference to  FIGS.  5 A and  5 B , current flows through the third capacitor C F  which is a flying capacitor during a period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on and during a period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on. When the average value IL_AVG of the inductor current is positive, because current flows in a forward direction, for example, from the second node N 2  to the fourth node N 4 , during the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on, the third capacitor C F  may be charged, and the voltage level of the voltage VCF may increase. Meanwhile, because current flows in a reverse direction, for example, from the fourth node N 4  to the second node N 2 , during the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on, the third capacitor C F  may be discharged, and the voltage level of the voltage VCF may be reduced. 
     In the period T 1 , the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on is longer than the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on. Accordingly, in the period T 1 , the voltage VCF increases in a direction close to the target voltage T_VCF. 
     Because the average value IL_AVG of the inductor current is negative in the period T 2 , the direction signal POS_D is at a logic low, and in response to the direction signal POS_D at a logic low, the PWM logic  122  may generate the first switching signal SS 1  based on the second PWM signal PWM 2 , and generate the second switching signal SS 2  based on the first PWM signal PWM 1 . 
     When the average value IL_AVG of the inductor current is negative, because current flows in the reverse direction, for example, from the fourth node N 4  to the second node N 2 , during the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on, the third capacitor C F  may be discharged, and the voltage level of the voltage VCF may be reduced. Meanwhile, because current flows in the forward direction, for example, from the second node N 2  to the fourth node N 4 , during the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on, the third capacitor C F  may be charged, and the voltage level of the voltage VCF may increase. 
     In the period T 2 , the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on may be shorter than the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on. Accordingly, in the period T 2 , the voltage VCF may increase in a direction close to the target voltage T_VCF. 
     Referring to  FIG.  10 B , when the voltage VCF is higher than the target voltage T_VCF, the first comparison voltage VPOS may be less than the second comparison voltage VNEG. In the period T 1 , the average value IL_AVG of the inductor current may be positive, and in the period T 2 , the average value IL_AVG of the inductor current may be negative. 
     When the average value IL_AVG of the inductor current is positive, because current flows in the forward direction, for example, from the second node N 2  to the fourth node N 4 , during the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on, the third capacitor CF may be charged, and the voltage level of the voltage VCF may increase. Meanwhile, because current flows in the reverse direction, for example, from the fourth node N 4  to the second node N 2 , during the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on, the third capacitor CF may be discharged, and the voltage level of the voltage VCF may be reduced. 
     In the period T 1 , the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on may be shorter than the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on. Accordingly, in the period T 1 , the voltage VCF may decrease in a direction close to the target voltage T_VCF. 
     Because the average value IL_AVG of the inductor current is negative in the period T 2 , the direction signal POS_D is at a logic low, and in response to the direction signal POS_D at a logic low, the PWM logic  122  may generate the first switching signal SS 1  based on the second PWM signal PWM 2 , and generate the second switching signal SS 2  based on the first PWM signal PWM 1 . 
     When the average value IL_AVG of the inductor current is negative, because current flows in the reverse direction, for example, from the fourth node N 4  to the second node N 2 , during the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on, the third capacitor C F  may be discharged, and the voltage level of the voltage VCF may be reduced. Meanwhile, because current flows in the forward direction, for example, from the second node N 2  to the fourth node N 4 , during the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on, the third capacitor CF may be charged, and the voltage level of the voltage VCF may increase. 
     In the period T 2 , the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on may be longer than the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on. Accordingly, in the period T 2 , the voltage VCF may be reduced in a direction close to the target voltage T_VCF. 
     As such, the charger IC ( 100  in  FIG.  1   ) according to some example embodiments may adjust the voltage VCF between both ends of a flying capacitor, i.e., the third capacitor CF, to be close to the target voltage T_VCF, by adjusting the first and second switching signals SS 1  and SS 2  controlling switching operations of the first to fourth switching transistors Q 1  to Q 4  according to whether the average value IL_AVG of the inductor current is positive or negative. The controller  120  may adjust the periods in which each of (or alternatively, at least one of) the first and second switching signals SS 1  and SS 2  has an active level and an inactive level according to the direction of the inductor current, and thus the bidirectional switching converter  110  may again properly perform flying capacitor balancing. 
       FIG.  11    is a timing diagram of signals of the bidirectional switching converter  110  and the controller  120  according to a comparative example. 
     According to the comparative example, regardless of whether the average value IL_AVG of the inductor current is positive or negative, the PWM logic  122  may generate the first switching signal SS 1  based on the first PWM signal PWM 1 , and generate the second switching signal SS 2  based on the second PWM signal PWM 2 . 
     During the periods T 1  and T 2 , a period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on may be longer than a period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on. During the period T 1 , the third capacitor C F  may be charged to increase the voltage VCF during the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on, and the third capacitor C F  may be discharged to reduce the voltage VCF during the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on. Accordingly, in the period T 1 , the voltage VCF may increase in a direction close to the target voltage T_VCF. 
     However, because the average value IL_AVG of the inductor current is negative in the period T 2 , the third capacitor C F  may be discharged to reduce the voltage VCF during the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on, and the third capacitor C F  may be charged to increase the voltage VCF during the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on. Accordingly, in the period T 2 , the period in which the first switching transistor Q 1  and the third switching transistor Q 3  are turned on may be longer than the period in which the second switching transistor Q 2  and the fourth switching transistor Q 4  are turned on, and thus the voltage VCF may be reduced in a direction away from the target voltage T_VCF. 
     In this way, unlike the control of the controller  120  according to some example embodiments, when the first and second switching signals SS 1  and SS 2  are generated irrespective of whether the average value IL_AVG of the inductor current is positive or negative, the bidirectional switching converter  110  may not properly perform flying capacitor balancing. 
       FIG.  12    is a block diagram schematically illustrating an electronic device  20  including the charger IC  100  according to some example embodiments. 
     Referring to  FIG.  12   , the electronic device  20  may include the charger IC  100 , the battery  200 , the wired power interface  310 , the wireless power interface  320 , and an application processor  400 . Operations between the charger IC  100 , the battery  200 , the wired power interface  310 , and the wireless power interface  320  have been described with reference to  FIG.  1   , and thus redundant descriptions thereof will be omitted. 
     In the electronic device  20  of  FIG.  12   , the application processor  400  may recognize voltages, for example, the first input voltage CHGIN and the second input voltage WCIN, provided from a device connected to the wired power interface  310  and the wireless power interface  320  or provided from the wired power interface  310  and the wireless power interface  320 . The application processor  400  may generate a mode signal MD determining a switching mode according to a recognized interface or input voltage, and provide the mode signal MD to the controller  120  of the charger IC  100 . 
     For example, when the first input voltage CHGIN is applied through the wired power interface  310  and a wireless power transmitting circuit is connected to the wireless power interface  320 , the application processor  400  may recognize the first input voltage CHGIN and the wireless power transmitting circuit, and generate the mode signal MD indicating a buck-boost mode. When an OTG device is connected to the wired power interface  310  or the wireless power transmitting circuit is connected to the wireless power interface  320 , the application processor  400  may generate the mode signal MD indicating a boost mode. 
     As such, the application processor  400  may generate the mode signal MD representing a plurality of switching modes and provide the mode signal MD to the controller  120 . The controller  120  may control the bidirectional switching converter  110  to perform a switching operation corresponding to the mode signal MD. 
       FIG.  13    is a block diagram illustrating a configuration of an electronic device  1000  including a charger IC  1910  according to some example embodiments. 
     The electronic device  1000  may include various electronic circuits. For example, the electronic circuits of the electronic device  1000  may include an image processing block  1100 , a communication block  1200 , an audio processing block  1300 , a buffer memory  1400 , a nonvolatile memory  1500 , a user interface  1600 , a main processor  1800 , a power manager circuit  1900 , and the charger IC  1910 . 
     The electronic device  1000  may be connected to a battery  1920 , and the battery  1920  may supply power used for an operation of the electronic device  1000 . However, the inventive concept is not limited thereto, and the power supplied to the electronic device  1000  may be provided from an internal/external power source other than the battery  1920 . 
     The image processing block  1100  may receive light through a lens  1110 . An image sensor  1120  and an image signal processor  1130  included in the image processing block  1100  may generate image information related to an external object based on the received light. 
     The communication block  1200  may exchange signals with an external device/system through an antenna  1210 . A transceiver  1220  and a modulator/demodulator (MODEM)  1230  of the communication block  1200  may process signals exchanged with the external device/system according to one or more of various wired/wireless communication protocols. 
     The audio processing block  1300  may process sound information using an audio signal processor  1310 . The audio processing block  1300  may receive an audio input through a microphone  1320  and may output audio through a speaker  1330 . 
     The buffer memory  1400  may store data used for an operation of the electronic device  1000 . For example, the buffer memory  1400  may temporarily store data processed or to be processed by the main processor  1800 . For example, the buffer memory  1400  may include volatile memory such as static random access memory (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), etc., and/or nonvolatile memory such as phase-change RAM (PRAM), magneto-resistive RAM (MRAM), resistive RAM (ReRAM), ferro-electric RAM (FRAM), etc. 
     The nonvolatile memory  1500  may store data regardless of whether power is supplied. For example, the nonvolatile memory  1500  may include at least one of various nonvolatile memories such as flash memory, PRAM, MRAM, ReRAM, FRAM, etc. For example, the nonvolatile memory  1500  may include removable memory such as a secure digital (SD) card or a solid state drive (SSD), and/or embedded memory such as an embedded multimedia card (eMMC). 
     The user interface  1600  may mediate communication between a user and the electronic device  1000 . For example, the user interface  1600  may include an input interface receiving input from the user and an output interface providing information to the user. 
     The main processor  1800  may control overall operations of components of the electronic device  1000 . The main processor  1800  may process various calculations to operate the electronic device  1000 . For example, the main processor  1800  may be implemented as a general-purpose processor, a special-purpose processor, an application processor, a microprocessor, etc., and may include one or more processor cores. 
     The power manager circuit  1900  may supply power to components of the electronic device  1000  and manage the power. For example, the power manager circuit  1900  may output a system voltage based on power provided from the charger IC  1910  and/or the battery  1920 . The power manager circuit  1900  may adjust a frequency of each of (or alternatively, at least one of) the components, a voltage level of the provided system voltage, etc., according to temperatures, operation modes (e.g., a performance mode, a standby mode, and a sleep mode), etc. of the components. 
     The charger IC  1910  may charge the battery  1920  based on power provided from an external power source or may provide power to the power manager circuit  1900 . Alternatively, the charger IC  1910  may provide power to an external device through a wired or wireless power interface based on power provided from the battery  1920 . 
     The charger IC  100  described with reference to  FIGS.  1  to  12    may be applied to the electronic device  1000  as the charger IC  1910 . The charger IC  100  may include a bidirectional switching converter implemented as a 3-level DC-DC converter. The bidirectional switching converter may operate in a buck mode, a buck-boost mode, and a boost mode. In the buck-boost mode, the charger IC  100  may adjust periods in which switching signals controlling a switching operation of a switching element have an active level and an inactive level based on a direction of current flowing through an inductor. Accordingly, flying capacitor balancing may be properly performed, and a ripple of the output voltage may be reduced. 
     Any of the elements and/or functional blocks disclosed above may include or be implemented in processing circuitry such as hardware including logic circuits; a hardware/software combination such as a processor executing software; or a combination thereof. For example, the controller  120  and application processor  400  may be implemented as processing circuitry. The processing circuitry specifically may include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, application-specific integrated circuit (ASIC), etc. The processing circuitry may include electrical components such as at least one of transistors, resistors, capacitors, etc. The processing circuitry may include electrical components such as logic gates including at least one of AND gates, OR gates, NAND gates, NOT gates, etc. 
     Processor(s), controller(s), and/or processing circuitry may be configured to perform actions or steps by being specifically programmed to perform those action or steps (such as with an FPGA or ASIC) or may be configured to perform actions or steps by executing instructions received from a memory, or a combination thereof. 
     While the inventive concept has been particularly shown and described with reference to example embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.