Abstract:
Various embodiments of the present invention relate to a power amplification device and method, wherein the power amplification device can comprise: a power amplifier; a switch mode converter for controlling a bias of the power amplifier; a comparator for providing a switching signal to the switch mode converter according to an envelope signal; and a control unit for determining whether a switching frequency of the switch mode converter is within a specific band and applying an offset to the switching frequency so as to deviate from the specific band if the switching frequency of the switch mode converter is within the specific band. Various other embodiments can be carried out.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to an apparatus and method for power amplification for reducing interference which affects a receiver by a transmitter power amplifier in a communication apparatus. 
       BACKGROUND ART 
       [0002]    A wireless communication system has usually used a digital modulation scheme in order to efficiently use limited frequency resources. A digital modulated signal may be transferred to an antenna through an amplification process of a signal using a Radio Frequency (RF) power amplifier according to the purpose. 
         [0003]    Meanwhile, a multi-carrier transmission scheme and a multidimensional modulation scheme which can transmit a lot of information according to user requirements for high-speed and high-capacity data processing have been developed. When the multi-carrier transmission scheme and the multidimensional modulation scheme are transmitted through a High Power Amplifier (HPA), signal distortion may be caused by nonlinear characteristics which the HPA has. 
         [0004]    The wireless communication system may improve a transmission and reception performance by allowing a power amplifier of a transmitter to have high-linearity/high-efficiency characteristics in various situations other than the case as described above. 
         [0005]    
       25 
     
       DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problem 
       [0006]    In the prior art, when a switching frequency of a DC-DC converter of an ET power amplifier or harmonics of the switching frequency are included in a reception band, reception conduction and a switching noise flows to a reception path by switching harmonics, thereby radiatively generating performance degradation. 
         [0007]    Various embodiments of the present disclosure may provide a power amplification apparatus and method for applying an offset to the switching frequency to allow the switching harmonic frequency to escape from the reception band range when a DC-DC harmonic frequency is included in a reception band range due to the switching operation of a power modulator for controlling the bias voltage of the power amplifier. 
         [0008]    Various embodiments of the present disclosure may provide a power amplification apparatus and method for improving a reception conduction performance by applying an offset to the switching frequency to allow the switching frequency and the harmonics of the switching frequency not to be included in the reception band. 
       TECHNICAL SOLUTION 
       [0009]    According to various embodiments of the present disclosure, a power amplification apparatus may include: a power amplifier; a switch mode converter that controls a bias voltage of the power amplifier; a comparator that provides a switching signal to the switch mode converter according to an envelope signal; and a controller that determines whether a switching frequency of the switch mode converter is included in a specific band, and applies an offset to the switching frequency to escape from the specific band when the switching frequency of the switch mode converter is included in the specific band. 
         [0010]    According to various embodiments of the present disclosure, the controller changes the switching frequency of the switch mode converter by changing an input signal or a reference voltage of the comparator. 
         [0011]    According to various embodiments of the present disclosure, the power amplification apparatus may further include a variable resistance unit that is connected to an input of the comparator and distributes an input voltage. 
         [0012]    According to various embodiments of the present disclosure, the comparator is configured by a Schmidt trigger circuit and the reference voltage of the comparator includes one of a first reference voltage changing from high to low and a second reference voltage changing from low to high. 
         [0013]    According to various embodiments of the present disclosure, the reference voltage of the comparator may be controlled as a value of an element controlling the first reference voltage and the second reference voltage in the Schmidt trigger circuit is changed. 
         [0014]    According to various embodiments of the present disclosure, the switching signal corresponds to a signal according to turning on/off, and frequency characteristics of the switching signal may be controlled by changing an on/off time of a DC-DC output. 
         [0015]    According to various embodiments of the present disclosure, the controller detects a current switching frequency in order to determine whether harmonic frequency components of the DC-DC output are induced to the reception band of a communication band due to the switching operation of a power modulator for controlling a bias voltage of the power amplifier. When a multiplied frequency of the switching frequency is in a state of degrading the conduction of the reception band, the switching frequency may be offset to escape from the specific band. 
         [0016]    According to various embodiments of the present disclosure, the power amplification apparatus may further include a linear amplifier that compensates for an error when a voltage difference between the envelope signal and an output signal of the switch mode converter is applied as the error. 
         [0017]    According to various embodiments of the present disclosure, a power amplification method may include: determining whether a switching frequency of a switch mode converter is included in a specific band; and applying an offset to the switching frequency to allow the switching frequency to escape from the specific band when the switching frequency of the switch mode converter is included in the specific band. 
         [0018]    According to various embodiments of the present disclosure, the switching frequency of the switch mode converter is changed based on an input signal or a reference voltage of a comparator supplying a switching signal to the switch mode converter. 
         [0019]    According to various embodiments of the present disclosure, the input signal of the comparator may be distributed by a variable resistance of an input terminal. 
         [0020]    According to various embodiments of the present disclosure, the comparator is configured by a Schmidt trigger circuit and the reference voltage of the comparator includes one of a first reference voltage changing from high to low and a second reference voltage changing from low to high. 
         [0021]    According to various embodiments of the present disclosure, the reference voltage of the comparator may be controlled as a value of an element controlling the first reference voltage and the second reference voltage in the Schmidt trigger circuit is changed. 
         [0022]    According to various embodiments of the present disclosure, the switching signal corresponds to a signal according to DC-DC turning on/off, and frequency characteristics of the switching signal may be controlled by changing an on/off time of a DC-DC output. 
         [0023]    According to various embodiments of the present disclosure, the method further includes: detecting a current switching frequency in order to determine whether harmonic frequency components of the DC-DC output is induced to the reception band of the communication band due to the switching operation of a power modulator for controlling a bias voltage of the power amplifier; and the switching frequency may be offset to escape from the specific band when a multiplied frequency of the switching frequency is in a state of degrading the conduction of the reception band. 
         [0024]    According to various embodiments of the present disclosure, an electronic device may include: a power amplifier; a switch mode converter configured to control a bias voltage of the power amplifier; a comparator configured to provide a switching signal to the switch mode converter based on an envelope signal; and a controller that determines whether a multiplied frequency of a switching frequency of the switch mode converter is included in a reception band, and applies an offset to the switching frequency to escape from the reception band when the switching frequency of the switch mode converter is included in the reception band. 
         [0025]    According to various embodiments of the present disclosure, the controller changes the switching frequency of the switch mode converter by changing an input signal or a reference voltage of the comparator. 
         [0026]    According to various embodiments of the present disclosure, the electronic device may further include a variable resistance unit that is connected to an input of the comparator and distributes an input voltage. 
         [0027]    According to various embodiments of the present disclosure, the comparator is configured by a Schmidt trigger circuit and the reference voltage of the comparator includes one of a first reference voltage changing from high to low and a second reference voltage changing from low to high. 
         [0028]    According to various embodiments of the present disclosure, the reference voltage of the comparator may be controlled as a value of an element controlling the first reference voltage and the second reference voltage in the Schmidt trigger circuit is changed. 
         [0029]    According to various embodiments of the present disclosure, the switching signal is a pulse signal having a frequency spectrum similar to an envelope signal, and a control of the switching frequency is performed by changing a number of times of turning on/off during a predetermined time. 
         [0030]    According to various embodiments of the present disclosure, the controller determines whether a multiplied frequency of a switching frequency of the switch mode converter is included in the reception band when a bias voltage corresponding to the envelope signal is provided to the power amplifier by the switch mode converter, and applies the offsets to the switching frequency to escape from the reception band when the switching frequency of the switch mode converter is included in the reception band. 
         [0031]    According to various embodiments of the present disclosure, the controller determines whether a baseband signal corresponds to a voice signal or whether a band of the baseband signal is smaller than a threshold value so as to determine whether the bias voltage corresponding to the envelope signal may be provided to the power amplifier by only the switch mode converter. 
         [0032]    According to various embodiments of the present disclosure, the electronic device may further include a linear amplifier that compensates for an error when a voltage difference between the envelope signal and an output signal of the switch mode converter is applied as the error. 
       Effects of the Invention 
       [0033]    As described above, a switching frequency is offset such that harmonics of the switching frequency or a switching frequency are not included in a reception band, thereby improving a reception conduction performance. 
         [0034]    Further, even when a radiation noise is induced to a reception path through an antenna because the antenna is adjacent to a power amplifier or radiation shielding is incompleteness, conduction degradation can be prevented. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]      FIG. 1  briefly illustrates an Envelope Tracking (ET) power amplifier according to various embodiment of the present disclosure. 
           [0036]      FIG. 2  briefly illustrates a linear amplifier of an ET power amplifier. 
           [0037]      FIG. 3  illustrates a diagram of a buck converter according to various embodiments of the present disclosure. 
           [0038]      FIG. 4  illustrates a diagram of the ET power amplifier according to various embodiments of the present disclosure. 
           [0039]      FIG. 5  illustrates a diagram of a buck converter of the ET power amplifier according to various embodiments of the present disclosure. 
           [0040]      FIG. 6  illustrates a Schmidt trigger circuit of the ET power amplifier according to various embodiments of the present disclosure. 
           [0041]      FIG. 7  is a graph illustrating a hysteresis characteristic of the Schmidt trigger circuit according to various embodiments of the present disclosure. 
           [0042]      FIG. 8  illustrates an example in which a pulse width or a duty cycle is changed when a first reference voltage is changed according to various embodiments of the present disclosure. 
           [0043]      FIG. 9  illustrates an example in which a pulse width or a duty cycle is changed when a second reference voltage is changed according to various embodiments of the present disclosure. 
           [0044]      FIG. 10  illustrates an example in which a pulse width or a duty cycle is changed when the first reference voltage and the second reference voltage are changed according to various embodiments of the present disclosure. 
           [0045]      FIG. 11  illustrates an example in which a pulse width control signal is generated using one reference voltage according to various embodiments of the present disclosure. 
           [0046]      FIG. 12  illustrates an example in which the pulse width control signal is generated when a reference voltage is reduced according to various embodiments of the present disclosure. 
           [0047]      FIG. 13  illustrates an example in which the pulse width control signal is generated when an input voltage of a hysteresis comparator increases according to various embodiments of the present disclosure. 
           [0048]      FIG. 14  illustrates an example in which the pulse width control signal is generated when the input voltage of the hysteresis comparator decreases according to various embodiments of the present disclosure. 
           [0049]      FIG. 15  illustrates an example in which the pulse width control signal is generated when the input voltage of the hysteresis comparator decreases according to various embodiments of the present disclosure. 
           [0050]      FIG. 16  illustrates an example in which a pulse width control signal is generated when an input voltage of the hysteresis comparator increases according to various embodiments of the present disclosure. 
           [0051]      FIG. 17  is a flowchart illustrating a power amplification method according to various embodiments of the present disclosure. 
           [0052]      FIG. 18  is a flowchart for changing a switching frequency of a switch mode converter according to various embodiments of the present disclosure. 
           [0053]      FIG. 19  is a flowchart for changing the switching frequency of the switch mode converter according to various embodiments of the present disclosure. 
           [0054]      FIG. 20  is a flowchart illustrating a power amplification method according to various embodiments of the present disclosure. 
           [0055]      FIG. 21  is a flowchart illustrating the power amplification method according to various embodiments of the present disclosure. 
           [0056]      FIG. 22  illustrates a lookup table according to various embodiments of the present disclosure. 
           [0057]      FIG. 23  illustrates an example in which harmonic components for the switching frequency are included in a reception band according to various embodiments of the present disclosure. 
           [0058]      FIG. 24  illustrates a configuration for distributing an input voltage of the hysteresis comparator according to various embodiments of the present disclosure. 
       
    
    
     MODE FOR CARRYING OUT THE INVENTION 
       [0059]    Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Further, in the following description of various embodiments of the present disclosure, a detailed description of known functions or configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear. The terms as described below are defined in consideration of the functions in the embodiments, and the meaning of the terms may vary according to the intention of a user or operator, convention, or the like. Therefore, the definition should be made based on the overall contents of the present specification. 
         [0060]    A power amplification device according to various embodiments of the present disclosure may be a device included in an electronic device. For example, the electronic device may be one or a combination of a smart phone, a tablet Personal Computer (PC), a mobile phone, a video phone, an e-book reader, a desktop PC, a laptop PC, a netbook computer, a Personal Digital Assistant (PDA), a Portable Multimedia Player (PMP), an MP3 player, a mobile medical device, an electronic bracelet, an electronic appcessary, a camera, a wearable device, an electronic clock, a wrist watch, a home appliance (for example, refrigerator, air conditioner, cleaner, oven, microwave oven, washing machine, and air cleaner), an artificial intelligence robot, a TeleVision (TV), a Digital Video Disk (DVD) player, an audio player, various types of medical devices (for example, Magnetic Resonance Angiography (MRA), Magnetic Resonance Imaging (MRI), Computed Tomography (CT), scanner, an ultrasonic device, and the like), a navigation device, a Global Positioning System (GPS) receiver, an Event Data Recorder (EDR), a Flight Data Recorder (FDR), a set-top box, a TV box (for example, Samsung HomeSync™, Apple TV™, or Google TV™), an electronic dictionary, a vehicle infotainment device, electronic equipment for a ship (for example, a navigation device for ship, a gyro compass, and the like), avionics, a security device, electronic clothes, an electronic key, a camcorder, game consoles, a Head-Mounted Display (HMD), a flat panel display device, an electronic frame, an electronic album, furniture or a part of buildings/structures having a communication function, an electronic board, an electronic signature receiving device, a wearable device, and a projector. It is obvious to those skilled in the art that the electronic device according to the present disclosure is not limited to the aforementioned devices. 
         [0061]    Hereinafter, various embodiments of the present disclosure will describe an apparatus and method for power amplification, which allows a switching frequency of a switch mode converter, which controls a bias voltage of a voltage amplifier, to be offset so as to make the switching frequency be not included in a reception band. 
         [0062]    An RF power amplifier may be used in various applications. The RF power amplifier may be operated to allow an RF input signal (RFin) having a small amount of energy to be converted into an RF output signal (RFout) having a large amount of amplified energy. Energy required to complete the conversion process may be generally provided by a Direct Current (DC) voltage supply (Vsupply), i.e, a battery power supply. 
         [0063]    In order to supply a power to the RF power amplifier, the RF power amplifier may apply a “fixed drain bias” scheme in which a fixed DC voltage supply (Vsupply) is directly connected to a drain of a transistor (generally, Field Effect Transistor (FET) having a gate, a drain, and a source). Efficiency of a power amplifier operated by the fixed drain bias may be reduced because a width of an RF input signal (RFin) is lower than the fixed DC voltage supply (Vsupply). 
         [0064]    An “Envelope Tracking (ET)” power amplifier for acquiring power efficiency higher than the fixed drain bias scheme is briefly illustrated in  FIG. 1 . The ET power amplifier  100  may be configured by an envelope modulator  102  and an RF power amplifier  104 . The envelope modulator  102  may modulate the supply voltage (Vsupply) according to an envelope signal (Venv). Herein, the RF input signal (RFin) is provided to an input terminal of an RF power amplifier  104  and the envelope signal (Venv) may include envelope information of the RF input signal (RFin). 
         [0065]    An envelope modulated power supply signal (VOUT) caused by the envelope modulator  102  may be connected to a supply voltage input of the RF power amplifier  104 . That is, the envelope modulated power supply signal (VOUT) caused by the envelope modulator  102  may be used as a bias voltage or current of the RF power amplifier  104 . In this event, the RF power amplifier  104  may amplify an RF input signal (RFin) according to the envelope modulated power supply signal (VOUT) and provide an RF output signal (RFout). Since the envelope modulated power supply signal (VOUT) tracks an envelope of the RF input signal (RFin), the RF power amplifier  104  may be operated with a power efficiency higher than the RF power amplifier using the fixed drain bias. 
         [0066]    In an ET power amplifier  100  of  FIG. 1 , the envelope modulator  102  may be implemented by various methods. One method is to use a linear amplifier (regulator). The linear amplifier may generate an output signal by linearly processing an input signal. Therefore, an envelope signal (Venv) may be applied to an input of the linear amplifier as shown in  FIG. 2 . The linear amplifier may provide the envelope modulated power supply signal (VOUT) linearly tracking an amplitude change of the linear envelope signal (Venv). 
         [0067]    The linear amplifier  200  may quickly react according to a rapid change of the envelope signal (Venv). Therefore, when the linear amplifier  200  is used in implementing the envelope modulator  102  in the ET power amplifier  100  of  FIG. 1 , the ET power amplifier  100  may provide an ability which can be operated in a wide band width. Since a current communication system such as an Orthogonal Frequency-Division Multiplexing (OFDM) based system and a Wideband Code Division Multiple Access (W-CDMA) cellular communication system uses a wideband signal, a wide band width operation is preferable. 
         [0068]    A switch-mode converter may be used for implementing the envelope modulator  102  of the ET power amplifier  100  of  FIG. 1  and corresponds to another conversion apparatus having efficiency higher than the linear amplifier  200 .  FIG. 3  is a diagram of a switch mode converter  300  (or a “step down” converter or a “buck” converter can be used) according to various embodiments of the present disclosure. The switch mode converter  300  may include a power supply (or “switching”) transistor  302  which is configured to be operated as a switch, an inductor  304 , and a condenser  306 . The switching transistor  302  may be controlled by a pulse width modulated switch control signal provided by a comparator  308  which is configured to be operated as a pulse width modulator. The pulse width modulated switch control signal is a square wave having a Duty cycle (D) according to a change of an amplitude of an envelope signal (Venv). The duty cycle refers to a ratio, is displayed as a percentage, of a high portion to a low portion during a period in the square wave. When the pulse width modulated switch control signal is applied to a gate of the switching transistor  302 , the switching transistor  302  is turned on/off so that a connection and a disconnection between the DC supply voltage (Vsupply) and the inductor  304  may be alternately performed. The inductor  304  and the capacitor  306  may be operated as a low-pass filter for filtering an inductor current before being transmitted to a load resistance  310 . The output voltage signal (VOUT) may be represented in proportion to a product of a size of the duty cycle (D) and a size of the DC supply voltage (Vsupply). That is, the output voltage signal (VOUT) corresponds to an envelope modulated power supply signal tracking an amplitude change of the envelope signal (Venv). 
         [0069]    While the switch mode converter  300  of  FIG. 3  effectively generates an envelope modulated power supply signal, a switching speed is slow and a switching noise may be generated. The switching noise corresponds to a noise by the switching operation of the switching transistor  302 . Filtering may not completely remove the switching noise and the switching noise may be inevitably induced to the RF output signal (RFout) of the RF power amplifier. It may be difficult for the switching noise to satisfy signal-to-noise ratio requirements required in a wireless standard. The switch mode converter  300  may be slowed down by a large-sized gate capacitance represented by a large-sized switching transistor. In order to generate and supply a large current, a transistor having a large-sized gate area may be required. However, the large-sized gate area may cause a large parasitic capacitance (about 1000 pF) which restricts a switching speed of the switching transistor  402  by about 5 MHZ. In order to track an accurate envelope, a switching frequency of 20 times to 50 times, which is larger than a required envelope band width, is required and many kinds of signal have 1 MHz or more signal envelope band widths. 
         [0070]    In order to satisfy the ET power amplifier satisfying both things in an effective and wide band width, it may be considered that a high-efficiency performance of the switch mode converter and a high bandwidth and a low noise performance of the linear amplifier are combined.  FIG. 4  illustrates an embodiment of an ET power amplifier  400 . The ET power amplifier  400  may be configured by an envelope modulator  402  and an RF power amplifier  404 . The envelope modulator  402  may be configured by a linear amplifier  406 , a hysteresis comparator  408 , and a switch mode converter  410 . The hysteresis comparator  408  may provide a pulse width modulated switch control signal to a switching transistor  412  of the switch mode converter  410  on the basis of a direction of a current flow detected by a current sense resistance  414 . The direction of the current may be determined by whether the linear amplifier  406  supplies (sources) a current to the RF power amplifier  404  or reduces (sinks) a supply over-current from the switch mode converter  410 . When the switch mode converter  410  provides excessive currents to a bias input terminal  405  of the RF power amplifier  404 , excess currents which are not required by the RF power amplifier  404  may be reduced (sunk) by the linear amplifier  406 . At a time point in which an instantaneous current required by the RF power amplifier  404  is larger than an instantaneous switch current supplied by the switch mode converter  410 , the remaining current required by the RF power amplifier  404  may be supplied to the RF power amplifier  404  by the linear amplifier  406 . 
         [0071]    With reference to a configuration of the switch mode converter  410  according to an embodiment of the present disclosure, the switch mode converter  410  may include a Metal Oxide Silicon Field Effect Transistor (MOSFET)  412  of p type having a gate, a source, and a drain, an inductor  417 , and a diode  418 . In the gate of the P-MOSFET  412 , may receive a pulse width switch control signal from the hysteresis comparator  408 , the source may be connected to the system supply voltage (Vsupply), and the drain may be connected to a first input terminal of the inductor  417  and a cathode of the diode  418 . A second terminal of the inductor  418  may be connected to a supply voltage input of the RF power amplifier  404 . 
         [0072]    In addition, the current sense resistance  414 , which has a resistance value much lower than a load resistance value, of the RF power amplifier  404  may be configured in a current supply path of the linear amplifier  406 . Terminals of the current sense resistance  414  are connected to an input of the hysteresis comparator  408  so as to control a value of a pulse width switch control signal applied to the P-MOSFET  412  of the switch mode converter  410 . 
         [0073]    For example, when an instant current supplied to the RF power amplifier  404  by the envelope modulator  412  is larger than a current required by the RF power amplifier  404 , the current may be absorbed in the linear amplifier  406 . When the instant current supplied to the RF power amplifier  404  by the envelope modulator  412  is smaller than the current required by the RF power amplifier  404 , the linear amplifier  406  may compensate for an insufficient current. 
         [0074]    In this event, the current sense resistance  414  detects a direction of a sense current flow and the hysteresis comparator  408  may respond by turning off the P-MOSFET  412  of the switch mode converter  410  when the instant current supplied to the RF power amplifier  404  by the envelope modulator  412  is larger than the current required by the RF power amplifier  404 . When the inductor  417  is separated from the supply voltage (Vsupply), the inductor  417  discharges charged energy so as to supply a current to the RF power amplifier  404 . When the current supplied to the RF power amplifier  404  is stabilized as a current required by the RF power amplifier  404 , the current direction is reversed through the current sense resistance  414  and the switch mode converter  410  may again supply most currents to the RF power amplifier  404 . 
         [0075]    Further, when the instant current provided to the RF power amplifier  404  is insufficient for power requirements of the RF power amplifier in the switch mode converter  410 , the hysteresis comparator  408  may respond by changing the pulse width switch control signal in the P-MOSFET  412  so as to allow the P-MOSFET  412  to be turned on. Until a current demand of the RF power amplifier  404  is fulfilled, the current supplied by the switch mode converter  410  may be supplemented by the current supplied by the linear amplifier  406 . 
         [0076]    That is, the envelope signal is amplified through the linear amplifier  406  and switching of the P-MOSFET  412  of the switch mode converter  410  may be turned on/off according to an output current direction. Further, the switch mode converter  410  supplies a power to a load through the inductor  417  and, a load terminal voltage (Vout) is negative fed back so as to be fed back as a differential input of the linear amplifier  406 . Herein, a difference between the original envelope signal and the load terminal voltage (Vout) acts as an error so that the error may be compensated for by the linear amplifier  406  according to an operation of the negative feedback. 
         [0077]    The hysteresis comparator  408  provides a pulse width modulated control signal, which is a control signal for switching the switch mode converter  410 , to the switch mode converter  410 . Further, in this event, the hysteresis comparator  408  may generate a switching noise repeating high and low according to turning on/off of the switch mode converter  410 . 
         [0078]    When the switching noise is overlapped with a reception band as shown in  FIG. 19  below, a noise affects reception conduction so that reception degradation may occur. Specifically, a radiated noise may be induced to an antenna. 
         [0079]    In various embodiments of the present disclosure, the controller  416  may apply an offset to the switching frequency of the switch mode converter  410  such that the switching noise is not included in a reception band. 
         [0080]    The switching frequency may be changed by adjusting a parameter of the hysteresis comparator  408  generating the switching signal. For example, the switching frequency is controlled by changing a first reference voltage  700  or a second reference voltage  710  of the hysteresis comparator  408  and controlling a pulse width and a duty cycle as shown in  FIGS. 8 to 10 , the switching frequency is controlled by changing the reference voltages and controlling the pulse width or the duty cycle during a predetermined time when one reference voltage is used as shown in  FIGS. 11 and 12 , and the pulse width or the duty cycle may be changed during a predetermined time by changing an input signal of the hysteresis comparator  408  as shown in  FIGS. 13 to 16 . For example, the input signal of the hysteresis comparator  408  may be changed using a variable resistance unit  415  connected to an input terminal. That is, as shown in  FIG. 24 , the variable resistance unit  415  is combined with the current sense resistance  414  and the input voltage is distributed, thereby being provided as an input of the hysteresis comparator  408 . 
         [0081]    The switching mode converter  410  in  FIG. 4  is configured by a P-MOSFET  412  having a gate, a source, and a drain, a diode, and inductor. However, in the configuration, an operation identical to operations of the P-MOSFET  412  and the diode can be implemented by a connection (couple) of another element. For example, in the switch mode converter  410  as shown in  FIG. 5A , a diode can be replaced with an N-MOSFET  535 , a gate of the N-MOSFET  535  is connected to an output terminal of the hysteresis comparator  408  as like the gate of the P-MOSFET  525 , and the N-MOSFET  535  and the P-MOSFET  525  may be turned on/off according to the pulse width control signal of the hysteresis comparator  408 . For example, the P-MOSFET  525  may be in an off state when the N-MOSFTE  535  is in an on state, and the P-MOSFET  525  may be in the on state when the N-MOSFET  535  is in the off state. 
         [0082]    In addition, in the switch mode converter  410  as shown in  FIG. 5B , a drain instead of the P-MOSFET  525  is accessed by the Vsupply and a source can be replaced with the N-MOSFET  436  accessed by the inductor  428 . In this event, the input terminal of the hysteresis comparator  408  may be changed and configured. That is, the hysteresis comparator  408  may drive the N-MOSFET  535  with an output signal (nVcout) on the contrary to a case of driving the P-MOSFET  525 . 
         [0083]    According to an embodiment of the present disclosure, the hysteresis comparator  408  may be configured by a Schmidt trigger circuit as shown in  FIG. 6  below. 
         [0084]      FIG. 6A  illustrates a Schmidt trigger circuit including two N type Bipolar transistors (Q 1   601  and Q 2   602 ) and a plurality of resistances (RC 1   603 , RC 2   604 , R 1   607 , RE  605 , and R 2   606 ), and  FIG. 6B  illustrates a Schmidt trigger circuit including one comparator and two resistances. 
         [0085]    In the case of  FIG. 6A , in the two transistors  601  and  602 , when one transistor is in a cut-off state, the other transistor is in a conducting state. Therefore, when there is no input voltage (e.g., Vin 1   450 ), the Q 1   601  is in the cut-off state, and a collector voltage of the Q 1   601  is divided by two resistances Rc 1   603  and R 1   607  into divided voltages, which are then applied to a base of the Q 2   602 . As a result, the base of the Q 2   602  may be in a saturation state and then be in a conducting state. When the input voltage (e.g., Vin 1   450 ) increases, the Q 1   601  is in the conducting state and the collector voltage gets lower so that the Q 2   602  may be in the cut-off state. 
         [0086]    For example, an operation in which, when one transistor of the two transistors  601  and  602  is in the cut-off state, the other transistor is in the conducting state is alternately performed so that the output voltage may be output as a waveform in which a pulse width is a rectangle. 
         [0087]    In other words, the Schmitt trigger circuit may perform an operation in which an output waveform rises when an input voltage (e.g., Vin 1   450 ) increases to be larger than or equal to a first predetermined value, and the output waveform descends when the input voltage decreases to be less than or equal to a second predetermined value. Therefore, the Schmitt trigger circuit may obtain a wave in which a pulse width corresponding to a conversion level is a rectangle when the input waveform enters. The Schmitt trigger circuit corresponds to a circuit sensitively operated according to the input voltage value and an output state may be converted by two different trigger voltage values (i.e., the first reference voltage  700  and the second reference voltage  710  of  FIG. 7  below). The hysteresis voltage refers to a voltage in which a value is changed according to a previous voltage state change, not a voltage which is defined as a regular value in a constant state. When an output voltage with respect to the input voltage is determined, an output voltage value determined when an input voltage value increases is different from an output voltage value determined when the input voltage value lowers. The voltage characteristic as described above refers to having the hysteresis characteristic. The hysteresis characteristic may prevent the output voltage value from being shaken with respect to the input value near threshold value when the output voltage is determined as high or low with respect to any threshold value for the input voltage value. In this event, using the hysteresis characteristic, the output voltage may maintain high before the threshold value decreases to be less than or equal to a specific value, after becoming high at a predetermined value or higher. On the contrary, the output voltage may maintain low before the threshold value increases to be larger than or equal to a specific value, after becoming low at a predetermined value or less. That is, it may be prevented that the output voltage value is changed by a small change near the threshold value. 
         [0088]    Two different trigger voltage values may be adjusted by a resistance RC 1   603  or a resistance RC 2   604 . For example, the first trigger voltage may increase as the resistance RC 1   603  decreases, the first trigger voltage may decrease as the resistance RC 1   603  increases, the second trigger voltage may increase as the resistance RC 2   604  decreases, and the second trigger voltage may decrease as the resistance RC 2   604  increases. 
         [0089]    In  FIG. 6B , an output voltage Vout 1  may be saturated regardless of a positive or negative direction by a positive feedback amount of a non-inverted input voltage (e.g., Vin 1   450 ). When the output voltage Vout 1  is saturated with a positive voltage, the positive (+) voltage may be fed back in the non-inverted input voltage (e.g., Vin 1   450 ). The output voltage (Vout)  1  may maintain a state in which the voltage is saturated with a positive voltage while an inverted input voltage (e.g., Vin 2   451 ) is less than a first threshold value. When an input voltage (e.g., Vin 1   450 ) rises, the input voltage increases to be larger than the first threshold value. In this event, an error voltage may change polarity and then operate the comparator  650  in a negative saturation state. When the output voltage Vout 1  becomes negative, the negative voltage may be fed back towards the non-inverted input (+) by feedback resistances R 1   651  and R 2   652 . The negative voltage is referred to as a second threshold value. When the input voltage (e.g., Vin 1   450 ) is larger than a second threshold value, the output voltage Vout 1  maintains the negative saturation state. When the input voltage (e.g., Vin 1   450 ) is lower than the second threshold value, the error voltage changes polarity and an amount of the output voltage Vout 1  may be again changed to the positive saturation state. 
         [0090]    Herein, the first trigger voltage and the second trigger voltage may be adjusted by adjusting the feedback resistance R 1   651  or the resistance R 2   652 . For example, the first trigger voltage may increase as the resistance RC 1  decreases, the first trigger voltage may decrease as the resistance RC 1  increases, the second trigger voltage may increase as the resistance RC 2  decreases, and the second trigger voltage may decrease as the resistance RC 2  increases. 
         [0091]      FIG. 7  is a graph illustrating a relationship between an input voltage and an output voltage indicating a hysteresis characteristic in the Schmidt trigger circuit. 
         [0092]    Referring to  FIG. 7 , an output state maintains 0 or low until an input voltage increases to reach to a second reference voltage  710 , and the output state is changed to 1 or high when the input voltage has reached the second reference voltage  710 . In addition, the output state maintains 1 or high until the input voltage decreases to be less than or equal to the first reference voltage  700 , and the output state may be changed to 0 or low when the input voltage has reached the first reference voltage  700 . 
         [0093]    A difference between the first reference voltage  700  and the second reference voltage  710  refers to hysteresis of a Schmitt trigger. 
         [0094]      FIGS. 8 to 12  illustrate a change in the number of duty cycles of a pulse width when the first reference voltage  700  and the second reference voltage  710  are changed in the Schmitt trigger circuit. 
         [0095]    According to various embodiments of the present disclosure, an output signal of the Schmitt trigger circuit may be used as a pulse width control signal of the switch mode converter  420  in  FIG. 4 . The pulse width control signal may be used as a control signal for turning on/off P type Metal Oxide Silicon Field Effect Transistors (MOSFET)  412 ,  525 , and  536  of the switch mode converter  410 . 
         [0096]      FIG. 8  illustrates an example in which a duty cycle of a pulse width is changed when a first reference voltage is changed according to various embodiments of the present disclosure. 
         [0097]    Referring to  FIG. 8 , a case, in which a pulse width is changed when a first reference voltage  700  decreases, is described. 
         [0098]      FIG. 8A  illustrates that a first reference voltage  700  and a second reference voltage  710  of a Schmitt trigger circuit are compared, and  FIG. 8B  illustrates an output signal of the Schmitt trigger circuit before the first reference voltage  700  decreases and the second reference voltage  700  increases, and  FIG. 8C  illustrates an output signal of the Schmitt trigger circuit after the first reference voltage  700  decreases as indicated by reference numeral  800 . 
         [0099]    When comparing the output signals of  FIGS. 8B and 8C , it may be considered that a pulse width or the number of duty cycles is changed during a predetermined time interval  850 . Herein, the pulse width may refer to a period in which the transistor is turned on/off, and the duty cycle may refer to a section, in which the transistor is turned on for one period, of the pulse width. The number of times by which the transistor is tuned on/off during a predetermined period may be defined as a switching frequency of the switch mode converter  420 . That is, the switching frequency may be defined as the number of times by which the P-MOSFETs  412 ,  525 , and  536  of the switch mode converter  410  is turned on/off during the predetermined time interval  850 . 
         [0100]    Further, that a plurality of pulse widths or the number of duty cycles is changed during the predetermined interval  850  according to the change of the first reference voltage  700  may refer to that the switching frequency of the switch mode converter  420  is changed. For example, since 2.5 pulses, i.e., three on sections and two off sections exist during a predetermined time interval  850  in  FIG. 8B , the switching frequency may be 2.5 (=5/2)Hz when the predetermined time interval  850  is one second. Further, since two pulses, i.e., two on section and two off sections exist during the predetermined time interval  850  in  FIG. 8C , the switching frequency may be 2 Hz when the predetermined time interval  850  is one second. 
         [0101]      FIG. 9  illustrates an example in which a duty cycle of a pulse width is changed when a second reference voltage is changed according to various embodiments of the present disclosure. 
         [0102]      FIG. 9  illustrates a case in which a pulse width or the number of duty cycles is changed when the second reference voltage  710  increases. 
         [0103]      FIG. 9A  illustrates that a first reference voltage  700  and a second reference voltage  710  of a Schmitt trigger circuit are compared, and  FIG. 9B  illustrates an output signal of the Schmitt trigger circuit before the first reference voltage  700  decreases and the second reference voltage  710  increases, and  FIG. 9C  illustrates an output signal of the Schmitt trigger circuit after the second reference voltage  710  increases as indicated by reference numeral  900 . 
         [0104]    When comparing the output signals of  FIGS. 9B and 9C , it may be considered that a pulse width or the number of duty cycles is changed during a predetermined time interval  950 . For example, since two pulses, i.e., two on sections and two off sections exist during a predetermined time interval  950  in  FIG. 9B , the switching frequency may be 2 Hz when the predetermined time interval  950  is one second. Further, since one pulse, i.e., one on section and one off section exist during the predetermined time interval  950  in  FIG. 9C , the switching frequency may be 1 Hz when the predetermined time interval  950  is one second. 
         [0105]      FIG. 10  illustrates an example in which a pulse width or a duty cycle is changed when a first reference voltage and a second reference voltage are changed according to various embodiments of the present disclosure. 
         [0106]    Referring to  FIG. 10 , a case, in which a pulse width is changed when both a first reference voltage  700  and a second reference voltage  710  have decreased, is described. 
         [0107]      FIG. 10A  illustrates that the first reference voltage  700  and the second reference voltage  710  of a Schmitt trigger circuit are compared, and  FIG. 10B  illustrates an output signal of the Schmitt trigger circuit before the first reference voltage  700  decreases and the second reference voltage  710  increases, and  FIG. 9C  illustrates an output signal of the Schmitt trigger circuit after the first reference voltage  700  decreases as indicated by reference numeral  1000  and the second reference voltage  710  increases as indicated by reference numeral  1010 . 
         [0108]    When comparing the output signals of  FIGS. 10B and 10C , it may be considered that a pulse width or the number of duty cycles is changed during a predetermined time interval  1050 . For example, since two pulses, i.e., two on sections and two off sections exist during a predetermined time interval  1050  in  FIG. 10B , the switching frequency may be 2 Hz when the predetermined time interval  1050  is one second. Further, since 1.5 pulses, i.e., one on section and two off sections exist during the predetermined time interval  1050  in  FIG. 10C , the switching frequency may be 1.5 Hz when the predetermined time interval  1050  is one second. 
         [0109]    Although  FIGS. 8 to 10  have used hysteresis characteristics using two reference voltages, a pulse width control signal may be generated using one reference voltage in various embodiments. 
         [0110]      FIG. 11  illustrates an example in which a pulse width control signal is generated using one reference voltage according to various embodiments of the present disclosure. 
         [0111]      FIG. 11A  illustrates that the input voltage  1100  and one reference voltage  1110  are compared, and  FIG. 11B  illustrates a pulse width modulated signal which is in a high state when the input voltage  1100  is higher than the reference voltage  1110 , and is in a low state when the input voltage  1100  is lower than the reference voltage  1110 . 
         [0112]      FIG. 12  illustrates an example in which a pulse width control signal is generated when a reference voltage is reduced according to various embodiments of the present disclosure. 
         [0113]      FIG. 12A  illustrates that an input voltage  1100  and one reference voltage  1110  are compared, as like  FIG. 11A  and the  FIG. 12B  illustrates an output signal when the reference voltage  1110  decreases as indicated by reference numeral  1200 . 
         [0114]    When comparing the output signals of  FIGS. 11B and 12B , it may be considered that the number of duty cycles of a pulse width is changed during predetermined time intervals  1150  and  1250 . For example, since four pulses, i.e., four on sections and four off sections exist during a predetermined time interval  1150  in  FIG. 11B , the switching frequency may be 4 Hz when the predetermined time interval  1150  is one second. Further, since two pulses, i.e., two on sections and two off sections exist during the predetermined time interval  1250  in  FIG. 12B , the switching frequency may be 2 Hz when the predetermined time interval  1250  is one second. 
         [0115]    As shown in  FIGS. 8 to 12 , when at least one reference voltage is changed, a pulse width or the number of duty cycles during a predetermined time interval may be changed, and that the pulse width or the number of duty cycles during the predetermined time interval is changed may be considered as meaning that a switching frequency is changed. 
         [0116]    In other various embodiments, the first reference voltage  700  and the second reference voltage  710  of the hysteresis comparator  408  are changed to control the pulse width or the duty cycle. Therefore, as shown in  FIGS. 13 to 16 , the pulse width or the duty cycle may be changed by changing an input signal of the hysteresis comparator  408  instead of the first reference voltage  700  and the second reference voltage  710  although the switching frequency for controlling an input voltage of the power amplifier may be changed. For example, the input signal of the hysteresis comparator  408  may be changed by a variable resistance unit  415  connected to an input terminal. That is, the variable resistance unit  415  may distribute a voltage across the current sense resistance  414  and then provide the voltage to an input of the hysteresis comparator  408 . 
         [0117]      FIG. 13  illustrates an example in which a pulse width control signal is generated by controlling an input voltage of the hysteresis comparator  408  according to various embodiments of the present disclosure. 
         [0118]      FIG. 13A  illustrates that an input voltage  1300  and a changed input voltage  1310  of a Schmitt trigger circuit are compared. The input voltage of the Schmitt trigger circuit may be changed by a voltage distribution by the variable resistance unit  415  and the current sense resistance  414 . 
         [0119]      FIG. 13B  illustrates an output signal according to the input voltage  1300  of the Schmitt trigger circuit, and  FIG. 13C  illustrates an output signal according to the changed input voltage  1310  of the Schmitt trigger circuit. 
         [0120]    When comparing the output signals of  FIGS. 13B and 13C , it may be considered that a pulse width or the number of duty cycles is changed during a predetermined time interval  1350 . For example, since 2.5 pulses, i.e., three on sections and two off sections exist during a predetermined time interval  1350  in  FIG. 13B , the switching frequency may be 2.5 Hz when the predetermined time interval  1350  is one second. Further, since 0.5 pulses, i.e., one on section exists during the predetermined time interval  1350  in  FIG. 13C , the switching frequency may be 0.5 Hz when the predetermined time interval  1350  is one second. 
         [0121]      FIG. 14  illustrates an example in which a pulse width control signal is generated by controlling an input voltage of the hysteresis comparator  408  according to various embodiments of the present disclosure. 
         [0122]      FIG. 14A  illustrates that an input voltage  1400  and a changed input voltage  1410  of a Schmitt trigger circuit are compared. The input voltage of the Schmitt trigger circuit may be changed by a voltage distribution by the variable resistance unit  415  and the current sense resistance  414 . 
         [0123]      FIG. 14B  illustrates an output signal according to the input voltage  1400  of the Schmitt trigger circuit, and  FIG. 14C  illustrates an output signal according to the changed input voltage  1410  of the Schmitt trigger circuit. 
         [0124]    When comparing the output signals of  FIGS. 14B and 14C , it may be considered that a pulse width or the number of duty cycles is changed during a predetermined time interval  1450 . For example, since two pulses, i.e., two on sections and two off sections exist during a predetermined time interval  1450  in  FIG. 14B , the switching frequency may be 2 Hz when the predetermined time interval  1450  is one second. Further, since off sections exist during the predetermined time interval  1450  in  FIG. 14C , the switching frequency may be 0.5 Hz when the predetermined time interval  1450  is one second. 
         [0125]      FIG. 15  illustrates an example in which a pulse width control signal is generated by controlling an input voltage of the hysteresis comparator  408  according to various embodiments of the present disclosure. 
         [0126]      FIG. 15B  illustrates an output signal according to an input voltage  1500  of a Schmitt trigger circuit, and  FIG. 15C  illustrates an output signal according to a changed input voltage  1510  of the Schmitt trigger circuit. The input voltage of the Schmitt trigger circuit may be changed by a voltage distribution by the variable resistance unit  415  and the current sense resistance  414 . 
         [0127]    When comparing the output signals of  FIGS. 15B and 15C , it may be considered that a pulse width or the number of duty cycles is changed during a predetermined time interval  1550 . For example, since four pulses, i.e., four on sections and four off sections exist during a predetermined time interval  1550  in  FIG. 15B , the switching frequency may be 4 Hz when the predetermined time interval  1550  is one second. Further, since 2.5 pulses, i.e., two on sections and three off sections exist during the predetermined time interval  1550  in  FIG. 15C , the switching frequency may be 2.5 Hz when the predetermined time interval  1550  is one second. 
         [0128]      FIG. 16  illustrates an example in which a pulse width control signal is generated by controlling an input voltage of the hysteresis comparator  408  according to various embodiments of the present disclosure. 
         [0129]      FIG. 16B  illustrates an output signal according to an input voltage  1600  of a Schmitt trigger circuit, and  FIG. 16C  illustrates an output signal according to a changed input voltage  1510  of the Schmitt trigger circuit. The input voltage of the Schmitt trigger circuit may be changed by a voltage distribution by the variable resistance unit  415  and the current sense resistance  414 . 
         [0130]    When comparing the output signals of  FIGS. 16B and 16C , it may be recognized that the number of duty cycles of a pulse width is changed. For example, since four pulses, i.e., four on sections and four off sections exist during a predetermined time interval  1650  in  FIG. 16B , the switching frequency may be 4 Hz when the predetermined time interval  1650  is one second. Further, since two pulses, i.e., two on sections and two off sections exist during the predetermined time interval  1650  in  FIG. 16C , the switching frequency may be 2 Hz when the predetermined time interval  1650  is one second. 
         [0131]      FIG. 17  is a flowchart illustrating the power amplification method according to various embodiments of the present disclosure. 
         [0132]    Referring to  FIG. 17 , an envelope signal is detected from a baseband signal in step  1700 , and a bias of the power amplifier  404  may be controlled according to the envelope signal in the switch mode converter  410  in step  1702 . For example, the switch mode converter  410  modulates a voltage supply or a battery power supply according to a pulse width control signal supplied by the hysteresis comparator  408 , thereby controlling the bias of the power amplifier  404 . The hysteresis comparator  408  may provide a pulse width modulated switch control signal to the switching transistor  412  of the switch mode converter  410  on the basis of the direction of the current flow detected by the current sense resistance  414 . The direction of the current may be determined according to whether the linear amplifier  406  supplies (sources) a current to the RF power amplifier  404  or reduces (sinks) a supply over-current from the switch mode converter  410 . 
         [0133]    The controller  416  may determine whether the switching frequency of the switch mode converter  410  is included in a reception band in step  1704 , and when the switching frequency of the switch mode converter  410  is included in a corresponding band, change a reference voltage of the hysteresis comparator  408  or control an input voltage, thereby changing the switching frequency of the switch mode converter  410  in step  1706 . 
         [0134]    The switch mode converter  410  turns on/off the switching transistor  412  according to the changed switching frequency so as to a bias voltage to the power amplifier  404  in step  1708 . 
         [0135]      FIG. 18  is a flowchart for changing the switching frequency of the switch mode converter according to various embodiments of the present disclosure. 
         [0136]    Referring to  FIG. 18 , the controller  416  may load a look-up table of  FIG. 23  indicating a relationship between a channel in a band and a reference voltage or a variable resistance change value in step  1800 , select a reference voltage or variable resistance change value corresponding to a channel in a corresponding band with reference to the look-up table in step  1802 , and adjust a parameter using the corresponding reference voltage or variable resistance change value in step  1804 . For example, an Rc 1  or Rc 2  value corresponding to the corresponding reference voltage change may be adjusted in  FIG. 6A , an R 1  or R 2  value corresponding to the corresponding reference voltage change may be adjusted in  FIG. 6B , or a variable resistance of the variable resistance unit  415  in  FIG. 5  may be adjusted. 
         [0137]      FIG. 19  is a flowchart for changing the switching frequency of the switch mode converter according to various embodiments of the present disclosure. 
         [0138]    Referring to  FIG. 19A , the controller  416  applies an offset to a switching frequency by Δf in step  1900 , calculates a reception conduction corresponding to the switching frequency which is applied the offset by Δf in step  1902 , proceeds to step  1906  when the calculated reception conduction is satisfied with a threshold value, adjusts a parameter to allow the switching frequency to be offset by a frequency spaced distance which the switching frequency is satisfied with, and returns to step  1900  when the calculated reception conduction is not satisfied the threshold value. That is, the controller  1900  may apply the offset to the switching frequency by Δf until the reception conduction is satisfied. 
         [0139]    In other embodiments, referring to  FIG. 19B , the controller  416  may calculate an offset value to determine how much the current switching frequency will be spaced from the corresponding band frequency band on the basis of the current reception conduction in step  1908 , and adjust the parameter to move the switching frequency by the calculated offset value in step  1910 . For example, Rc 1  or Rc 2  value corresponding to a corresponding reference voltage change may be adjusted in  FIG. 6A , R 1  or R 2  value corresponding to a corresponding reference voltage change may be adjusted in  FIG. 6B , or a variable resistance of the variable resistance unit  415  of  FIG. 5  may be adjusted. 
         [0140]    In various embodiments of the present disclosure, in a case of Voice Over LTE (VoLTE), since a bandwidth of an input envelope is small, most energy can be supplied by DC-DC switching so that the power amplifier can be operated by only a DC-DC converter. For example, in  FIG. 4 , a bias voltage may be supplied to the RF amplifier  404  by only the switch mode converter  410 . When the bias voltage has been supplied to the RF amplifier  404  by only the switch mode converter  410 , since a change amount of the switching frequency of the switch mode converter  410  is small according to a time, harmonic components depending on a fixed switching frequency may increase. The switching frequency may be offset with respect to a case in which the harmonic frequency component brings actual reception conduction degradation by determining whether the harmonic frequency component invades a reception band of the communication band. 
         [0141]      FIGS. 20 and 21  illustrate a power amplification method performing the switching frequency change operation in a voice signal or a low-band signal. 
         [0142]      FIG. 20  is a flowchart illustrating the power amplification method according to various embodiments of the present disclosure. 
         [0143]    Referring to  FIG. 20 , the controller  416  may determine whether a baseband signal corresponds to a voice signal such as a VoLTE in step  2000 . For example, the controller  416  may receive control information notifying that the baseband signal corresponds to the voice signal such as the VoLTE, or recognize whether the baseband signal corresponds to the voice signal such as the VoLTE by analyzing the baseband signal. 
         [0144]    The controller  416  may determine, when the baseband signal is determined as the voice signal in step  2002 , whether the switching frequency of the switch mode converter  410  is included in a reception band in step  2004 , and when the switching frequency of the switch mode converter  410  is included in a corresponding band, change a reference voltage of the hysteresis comparator  408  or control an input voltage, thereby changing the switching frequency of the switch mode converter  410  in step  2006 . 
         [0145]    In step  2008 , in the switch mode converter  410 , the switching transistor  412  is turned on/off according to the changed switching frequency and a voltage supply or a battery power supply is modulated, thereby providing a bias voltage to the power amplifier  404 . 
         [0146]      FIG. 21  is a flowchart illustrating the power amplification method according to various embodiments of the present disclosure. 
         [0147]    Referring to  FIG. 21 , the controller  416  may determine a band of a baseband signal through a spectrum analysis in step  2100 . For example, the controller  416  may determine whether a band of the baseband signal corresponds to a low-band lower than a threshold value or a high-band larger than the threshold value. 
         [0148]    When the baseband signal is determined as the low-band in step  2102 , the controller  416  may determine whether the switching frequency of the switch mode converter  410  is included in a reception band in step  2104 . 
         [0149]    For example, the switching frequency band of the switch mode converter  410  may be calculated on the basis of the input envelope signal characteristics and signal characteristics of the output terminal (Vout) of the switch mode converter  410 , and it is possible to determine whether the switching frequency of the switch mode converter  410  is included in the reception band by comparing the calculated switching frequency band and a reception band used in current communication. 
         [0150]    When the switching frequency of the switch mode converter  410  is included in the corresponding reception band in step  2106 , the switching frequency of the switch mode converter  410  may be changed by changing a reference voltage of the hysteresis comparator  408  or controlling an input voltage through a configuration change of the variable resistance unit  415 . 
         [0151]    Meanwhile, the switching frequency of the switch mode converter  410  is not included in a corresponding reception band, a bias voltage may be provided to the power amplifier  404  without the switching frequency change in a corresponding mode. 
         [0152]    In step  2108 , in the switch mode converter  410 , the switching transistor  412  is turned on/off according to the changed switching frequency and a voltage supply or a battery power supply is modulated, thereby providing the bias voltage to the power amplifier  404 . 
         [0153]    According to various embodiments, a power amplification method of an electronic device may include: determining whether a switching frequency of a switch mode converter is included in a reception band; and applying an offset to the switching frequency to allow the switching frequency to escape from the reception band when the switching frequency of the switch mode converter is included in a reception specific band. According to an embodiment, the switching frequency of the switch mode converter is changed on the basis of an input signal or a reference voltage of a comparator supplying a switching signal to the switch mode converter. According to an embodiment, the input signal of the comparator is distributed by a variable resistance of an input terminal. According to an embodiment, the comparator is configured by a Schmidt trigger circuit and the reference voltage of the comparator includes one of a first reference voltage changing from high to low and a second reference voltage changing from low to high. According to an embodiment, the reference voltage of the comparator may be controlled as a value of an element controlling the first reference voltage and the second reference voltage in the Schmidt trigger circuit is changed. According to an embodiment, the switching signal is a pulse signal having a frequency spectrum similar to an envelope signal, and a control of the switching frequency is performed by changing a number of times of turning on/off during a predetermined time. According to an embodiment, the method may further include: determining whether a bias voltage corresponding to the envelope signal is provided to the power amplifier by the switch mode converter before determining whether the switching frequency of the switch mode converter is included in the reception band. According to an embodiment, the determining of whether the bias voltage corresponding to the envelope signal in the switch mode converter is provided to the power amplifier may include: determining whether a baseband signal corresponds to a voice signal; and determining whether a band of the baseband signal is smaller than a threshold value. 
         [0154]      FIG. 22  illustrates a lookup table according to various embodiments of the present disclosure. 
         [0155]    Referring to  FIG. 22 , in a look-up table, an in-band channel and a reference voltage or variable resistance change value are mapped. Therefore, when the switching frequency is included in a channel of the corresponding band in the case of reception or transmission using a channel of the corresponding band by a transmitter, a reference voltage or a variable resistance change value mapped in the channel of the corresponding band may be provided to the controller  416 . 
         [0156]      FIG. 23  illustrates an example in which harmonic components for the switching frequency are included in a reception band according to various embodiments of the present disclosure. 
         [0157]    Referring to  FIG. 23 , a periodically repeated waveform which is not a sine wave decomposes into a sine wave having a basic frequency and a wave having integer multiple frequencies, and indicates components other than a basis frequency configuring a harmonic repeated waveform. 
         [0158]    That is, the switching frequency may be generated as an n-th harmonic frequency other than the basis frequency and a part of multiple high-frequency components of the switching frequency may be included in the reception band. 
         [0159]    In various embodiments of the present disclosure, the switching frequency is offset to allow the multiple high-frequency component of the switching frequency to be not overlapped with the reception band. Therefore, it is made not to affect the reception or transmission performance. 
         [0160]      FIG. 24  illustrates a configuration for distributing an input voltage of the hysteresis comparator  408  according to various embodiments of the present disclosure. 
         [0161]    Referring to  FIG. 24 , the variable resistance unit  415  and the current sense resistance  414  may be connected (coupled) in parallel for a voltage distribution, and a voltage across the current sense resistance  414  may be transferred to the variable resistance unit  415 . In various embodiments of the present disclosure, the variable resistance unit  415  may distribute a voltage of the current sense resistance  414  according to a location of a tab. For example, when a tab is performed in a ½ position of the variable resistance, only 50% of voltage across the current sense resistance  414  is provided to an input of the hysteresis comparator  408 . Further, when a tab is performed in a ⅓ position of the variable resistance, only 33% of the voltage across the current sense resistance  414  may be provided to the input of the hysteresis comparator  408 . 
         [0162]    Various embodiments of the present disclosure are not limited to an example in which the voltage across the current sense resistance  414  is distributed according to a positon of the tab of the variable resistance, and may be implemented as a digital variable resistance. 
         [0163]    According to various embodiments, a power amplification apparatus may include: a power amplifier; a switch mode converter that controls a bias voltage of the power amplifier; a comparator that provides a switching signal to the switch mode converter according to an envelope signal; and a controller that determines whether a multiplied frequency of a switching frequency of the switch mode converter is included in a reception band, and applies an offset to the switching frequency to escape from the reception band when the switching frequency of the switch mode converter is included in the reception band. According to an embodiment, the controller changes the switching frequency of the switch mode converter by changing an input signal or a reference voltage of the comparator. According to an embodiment, the power amplification apparatus may further include: a variable resistance unit that is connected to an input of the comparator and distributes an input voltage. According to an embodiment, the comparator is configured by a Schmidt trigger circuit and the reference voltage of the comparator includes one of a first reference voltage changing from high to low and a second reference voltage changing from low to high. According to an embodiment, the reference voltage of the comparator may be controlled as a value of an element controlling the first reference voltage and the second reference voltage in the Schmidt trigger circuit is changed. According to an embodiment, the switching signal is a pulse signal having a frequency spectrum similar to an envelope signal, and a control of the switching frequency is performed by changing a number of times of turning on/off during a predetermined time. According to an embodiment, the controller determines whether a multiplied frequency of a switching frequency of the switch mode converter is included in the reception band when a bias voltage corresponding to the envelope signal is provided to the power amplifier by the switch mode converter, and applies the offset to the switching frequency to escape from the reception band when the switching frequency of the switch mode converter is included in the reception band. According to an embodiment, the controller determines whether a baseband signal corresponds to a voice signal or whether a band of the baseband signal is smaller than a threshold value so as to determine whether the bias voltage corresponding to the envelope signal may be provided to the power amplifier by only the switch mode converter. According to an embodiment, the power amplification apparatus may further include a linear amplifier that compensates for an error when a voltage difference between the envelope signal and an output signal of the switch mode converter is applied as the error. 
         [0164]    According to various embodiments, an electronic device may include: a power amplifier; a switch mode converter that controls a bias voltage of the power amplifier; a comparator that provides a switching signal to the switch mode converter according to an envelope signal; and a controller that determines whether a multiplied frequency of a switching frequency of the switch mode converter is included in a reception band, and applies an offset to the switching frequency to escape from the reception band when the switching frequency of the switch mode converter is included in the reception band. According to an embodiment, the controller changes the switching frequency of the switch mode converter by changing an input signal or a reference voltage of the comparator. According to an embodiment, the power amplification apparatus may further include: a variable resistance unit that is connected to an input of the comparator and distributes an input voltage. According to an embodiment, the comparator is configured by a Schmidt trigger circuit and the reference voltage of the comparator includes one of a first reference voltage changing from high to low and a second reference voltage changing from low to high. According to an embodiment, the reference voltage of the comparator may be controlled as a value of an element controlling the first reference voltage and the second reference voltage in the Schmidt trigger circuit is changed. According to an embodiment, the switching signal is a pulse signal having a frequency spectrum similar to an envelope signal, and a control of the switching frequency is performed by changing a number of times of turning on/off during a predetermined time. According to an embodiment, the controller determines whether a multiplied frequency of a switching frequency of the switch mode converter is included in the reception band when a bias voltage corresponding to the envelope signal is provided to the power amplifier by the switch mode converter, and applies the offset to the switching frequency to escape from the reception band when the switching frequency of the switch mode converter is included in the reception band. According to an embodiment, the controller determines whether a baseband signal corresponds to a voice signal or whether a band of the baseband signal is smaller than a threshold value so as to determine whether the bias voltage corresponding to the envelope signal may be provided to the power amplifier by only the switch mode converter. According to an embodiment, the power amplification apparatus may further include a linear amplifier that compensates for an error when a voltage difference between the envelope signal and an output signal of the switch mode converter is applied as the error. 
         [0165]    Meanwhile, although the concrete embodiments of the present disclosure have been described in the detailed description of the present disclosure, various modifications can be made without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the aforementioned embodiments, but should be defined by the equivalents to the appended claims as well as the claims.