The present invention relates to a power supplying apparatus and a control method thereof.
The digital modulation method applied to the recent wireless communication such as the cellular phone and the wireless LAN (Local Area Network) adopts the modulation format such as QPSK (Quadrature Phase Shift Keying), multi-level QAM (Quadrature Amplitude Modulation) or the like. According to the modulation format, a locus of a signal is amplitude-modulated when a transition between symbols is generated. And, an amplitude (envelope) of a high frequency modulation signal superposed on a carrier signal of the microwave band changes as a time elapses. Here, a ratio of peak electric power to average electric power of the high frequency modulation signal is called PAPR (Peak-to-Average Power Ratio). In the case of amplifying a signal whose PAPR is large, in order to secure accurate linearity, it is necessary to supply an amplifier with sufficiently large electric power from a power supply so as not to make a signal waveform distorted even at a time of peak electric power. In the other words, it is necessary to make the amplifier work with a margin (back off), that is, to make the amplifier work in an electric power domain lower enough than the saturation electric power limited by a power supply voltage. Generally, since a class A or a class B linear amplifier has the maximum electric power efficiency in a vicinity of the saturation output electric-power, average efficiency is low in the case of making the amplifier work at an area where the back off is large.
In the case of the multi-carrier OFDM (Orthogonal Frequency Division Multiplexing) method which the next-generation cellular phone, the wireless LAN, and the digital television broadcasting adopt, PAPR has a tendency to become very large, and consequently the average efficiency of the amplifier is degraded furthermore. Accordingly, it is desirable as characteristics of the amplifier to have high efficiency even at the area where the back off is large.
As a method to amplify a signal at the area where the back off is large, and in a wide dynamic range, the EER (Envelope Elimination and Restoration) method and the ET (Envelope Tracking) method are known.
In the case of the EER method, firstly, an input modulation signal is divided into a phase component and an amplitude component. The phase component is inputted into an electric power amplifier with making phase modulation information unchanged and making an amplitude constant. At this time, the electric power amplifier is always operated near the saturation point used as the maximum in efficiency. Meanwhile, the amplitude component changes an output voltage of a power supplying apparatus on the basis of amplitude modulation information, and the output voltage is used as a power supply of the electric power amplifier. By carrying out the above-mentioned operation, the electric power amplifier works as a multiplier, and then the phase component and the amplitude component of the modulation signal are combined. As a result, it is possible to obtain an output modulation signal with no relation to the back off and with high efficiency.
On the other hand, a configuration, in which an amplitude component of an input modulation signal makes an output voltage of a power supplying apparatus changed on the basis of amplitude modulation information and the changed output voltage is used as the power supply of the electric power amplifier, according to the ET method is the same as the configuration according to the EER method. A different point of the ET method from the EER method is that, while only the phase modulation signal whose amplitude is constant is inputted into the electric power amplifier and the electric power amplifier is worked in a state of saturation according to the EER method, the input modulation signal which includes both the amplitude modulation and the phase modulation is inputted into the electric power amplifier as it is and the electric power amplifier is worked linearly according to the ET method. In this case, since the electric power amplifier works linearly, electric power efficiency of the ET method is more inferior than one of the EER method. However, since only the necessary and minimum electric power is supplied to the electric power amplifier according to the amplitude of the input modulation signal, it is possible to obtain high electric-power efficiency in comparison with the case that the electric power amplifier is worked by use of the constant voltage and with no relation to the amplitude. Furthermore, the ET method has an advantage that a timing margin for combining the amplitude component and the phase component is eased, and consequently realization of the ET method is easy in comparison with the EER method.
Here, it is necessary that a modulation power supplying apparatus is used in the EER method and the ET method can change an own output voltage with accuracy, low noise, and high efficiency according to the amplitude component of the input modulation signal. The reason is that in the case of the wireless communication method such as the cellular phone which uses the recent digital modulation, it is specified by the standard that ACPR (Adjacent Channel Leakage Power Ratio) and EVM (Error Vector Magnitude) should be suppressed so as to be not larger than a predetermined value. In the case that an output voltage of the electric power supplying apparatus is not linear to an input amplitude signal, ACPR and EVM are degraded by the cross-modulation distortion. When noise of the power supplying apparatus is mixed with an output of the amplifier, ACPR is also degraded. In the case of the EER method and the ET method, it is generally considered necessary that a response bandwidth (speed) of the power supplying apparatus is at least two times wider (higher) than a bandwidth (speed) of the modulation signal. For example, the modulation bandwidth based on the WCDMA (Wideband Code Division Multiple Access) specification of the cellular phone is about 5 MHz, and the modulation bandwidth based on the IEEE802.11a/g specification of the wireless LAN is about 20 MHz. It is difficult that the usual power supplying apparatus which has a configuration including a switching converter outputs the above broad bandwidth modulation signal. Here, IEEE used in the above description is an abbreviation of Institute of Electrical and Electronic Engineers.
In order to realize a voltage source with high efficiency and superior quality, two basic configurations of a hybrid voltage source which combines a switching amplification unit with high efficiency and a linear amplification unit with superior accuracy are disclosed in a non-patent literature 1.
A configuration of the hybrid voltage source which combines the switching amplification unit and the linear amplification unit is classified into the configurations shown in
An amplifier which applied the configuration of the first hybrid voltage source shown in
The amplitude signal 9 is inputted to the voltage follower 3 (linear amplification unit 3) including an operational amplifier 31. Here, an envelope of the WCDMA downlink signal is used (refer to 9 shown in
Since Ic at a terminal for the output voltage Vout is expressed by a formula of Ic=Iout−Im, in the case that the switching current Im is excessive in comparison with an output electric current lout which flows through the electric power amplifier (load 1), the output current Ic of the voltage follower 3 (output current of the linear amplification unit) flows reversely (Ic<0), and starts flowing in a direction toward the operational amplifier 31. As a result, the polarity of the hysteresis comparator 41 is reversed to be Low, and then the switching element 21 is turned off (non-conductive state). At this time, in order to maintain the electric current which flows through the inductor 23, the electric current Im flows from GND to the electric power amplifier (load 1) through the diode 22. Moreover, potential of a cathode of the diode 22 (that is, the switching voltage Vsw) is 0V (refer to the waveform indicated by the code 10 in
In a series of these operations, the electric current Ic (refer to the waveform indicated by the code 14 in
By using the output voltage Vout obtained by carrying out the above-mentioned operation as the power supply of the electric power amplifier (load 1), and carrying out the above-mentioned EER operation or the ET operation, only the minimum electric power is supplied from the power supplying apparatus according to the amplitude of the input modulation signal. Accordingly, the electric power amplifier (load 1) always works at the saturation area where efficiency is high, and also electric power efficiency of a whole of a transmitter system equipped with the power supplying apparatus and the electric power amplifier is improved.
[Non-patent literature 1] IEEE TRANSACTIONS ON POWER ELECTRONICS (1986, VOL.PE-1, NO. 1, pp. 48-54,
[Non-patent literature 2] IEEE MTT-S Digest (2004, Vol. 3, pp. 1543-1546,
In order to realize high efficiency of the amplifier (transmitter) shown in
However, in the case that the above-mentioned circuit configuration is applied to an apparatus such as the base station of the cellular phone which uses a large amount of the electric power, the power supply voltage Vcc1 will be several tens volt. It is generally considered difficult to switch such a large amplitude signal at a high speed and with small loss. The reason is that the switching element 21 (for example, MOSFET) and the diode 22 included in the switching amplification unit have an output parasitic capacitor Cp. In the case of switching under the condition of a power supply voltage V and a switching frequency fsw, electric power loss of Cp*V2*fsw is caused. Accordingly, as the power supply voltage V and the switching frequency fsw become large, the electric power loss also becomes large and consequently efficiency of the switching amplification unit 2 is degraded.
Accordingly, it is conceivable to make a value of the inductor 23 large in order to lower the switching frequency.
At a peak area where through-rate of the input signal (waveform indicated by a code 9 of
On the other hand, at an area where the input signal is small, since the value of the inductor 23 is large, the switching electric current Im (waveform indicated by the code 13 in
As mentioned above, since the large electric current flows actually through the linear amplification unit 3 having low power-efficiency at a time when a broadband signal such as WCDMA is inputted, efficiency of a whole of the power supplying apparatus is degraded. A problem that also efficiency of a whole of the transmitter equipped with the electric power amplifier according to the ET method which uses the power supplying apparatus is degraded is caused as a result.
An object of the present invention is to provide a power supplying apparatus and a control method which are superior in electric power efficiency.
Means to Solve the Problem
A power supplying apparatus according to the present invention includes a switching amplification unit supplying a first load with most of electric power, and a linear amplification unit correcting an output voltage applied to the first load according to an input signal. Furthermore, an electric current which flows into the linear amplification unit at the time of the correcting is supplied to a second load from a power supply terminal of the linear amplification unit.
Moreover, a power supplying apparatus according to the present invention, generating an output voltage according to an input signal, includes a linear amplification unit carrying out correction so as to make a relation between the input signal and the output signal linear, a control signal generating unit generating a control signal based on a flowing direction and a magnitude of an output current of the linear amplification unit, and a switching amplification unit outputting an electric current switching-amplified on the basis of the control signal. Furthermore, the linear amplification unit and the switching amplification unit are arranged in parallel, a total electric current of the output electric current of the linear amplification unit and an output electric current of the switching amplification unit are added and outputted to a first load, and an electric current which flows into the linear amplification unit at the time of the correcting is supplied to a second load from a power supply terminal of the linear amplification unit.
Moreover, a power supplying apparatus according to the present invention, generating an output voltage according to an input signal, includes a linear amplification unit carrying out correction so as to make a relation between the input signal and the output signal linear, a control signal generating unit generating a control signal based on the input signal, and a switching amplification unit outputting a voltage switching-amplified on the basis of the control signal. Furthermore, the linear amplification unit and the switching amplification unit are arranged in series, a total output voltage of an output voltage of the linear amplification unit and an output voltage of the switching amplification unit are added and outputted to a first load, and an electric current which flows into the linear amplification unit at the time of the correcting is supplied to a second load from a power supply terminal of the linear amplification unit.
Moreover, a control method according to the present invention which controls a power supplying apparatus including a switching amplification unit and a linear amplification unit includes supplying a first load with most of electric power by use of the switching amplification unit, and correcting an output voltage applied to the first load according to an input signal by use of the linear amplification unit, and supplying an electric current which flows into the linear amplification unit at the time of the correcting to a second load from a power supplying terminal of the linear amplification unit.
According to the present invention, it is possible to improve electric power efficiency.
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The switching amplification unit 2 works as a current source and supplies an electric current to the first load 1. The linear amplification unit 3 works as a voltage source and corrects so that an output voltage applied to the first load 1 may be identical with an input signal. The switching amplification unit 2 and the linear amplification unit 3 are connected each other in parallel for the first load 1. Electric power is supplied from a power supplying terminal of the linear amplification unit 3 to a second load 30.
The reference signal Vref inputted into the power supplying apparatus is inputted specifically into the linear amplification unit 3, and is amplified linearly. The electric current detecting resistor 7 detects a flowing direction and a magnitude of the output electric current Ic of the linear amplification unit 3, and outputs the detection result to the control signal generating unit 4. The control signal generating unit 4 generates a pulse width modulation signal which has two levels of High and Low based on the detected direction and magnitude of the electric current, and outputs the pulse width modulation signal to the switching amplification unit 2 as a control signal. The switching amplification unit 2 makes the switching elements 21 and 22 carry out an on/off work on the basis of the control signal, and converts an output of the switching elements 21 and 22 into the electric current Im by use of the inductor 23 and outputs the electric current Im. An output terminal of the switching amplification unit 2 and an output terminal of the linear amplification unit 3 are connected each other. The output electric current Im (hereinafter, may be described as switching electric current Im) of the switching amplification unit 2 and the output electric current Ic of the linear amplification unit 3 are added each other and the added electric current is supplied to the first load 1. The second load 30 is connected with power supplies V1 and V2 of the linear amplification unit 3. In this case, the second load 30 is corresponding to another block included in the system.
Hereinafter, an operation of the first exemplary embodiment of the present invention will be described in detail with reference to
As shown in
When the output electric current Ic which flows from the linear amplification unit 3 toward the first load 1 increases to be IC(+) and the output electric current Ic is equal to a high voltage side threshold value of the hysteresis comparator 41, or larger than the threshold value, the output of the hysteresis comparator 41 is High. This signal is inputted into a gate of the switching element 21 which is composed of MOSFET etc. to turn the switching element 21 on (conductive state). As a result, an electric current flows from the power supply Vcc1 through the switching element 21, and is smoothed by the inductor 23. Afterward, the smoothed electric current flows in a direction toward the first load 1 as the electric current Im. At this time, since the switching voltage Vsw is equal to Vcc1, a reverse voltage is applied to the diode 22, and consequently an electric current does not flow.
At a terminal for the output voltage Vout of the power supplying apparatus shown in
Ic=Iout−Im
Here, in the circuit shown in
Iout=Vout/R
Accordingly, if Vref is fixed, also a value of Iout is fixed. Meanwhile, since the linear amplification unit 3 (voltage follower) works as a voltage source, Ic can have any value. Accordingly, if the excessive electric current Im flows from the switching amplification unit 2 in comparison with the fixed Tout, the excessive electric current has to be adjusted by Ic since Tout is fixed. Accordingly, when the switching electric current Im is excessive in comparison with the output electric current Tout which flows through the first load 1, the operational amplifier electric current Ic (Ic=Ic(−)) flows reversely and starts flowing in a direction flowing into the operational amplifier 31. When a voltage applied to the electric current detecting resistor 7 by the operational amplifier electric current Ic(−) is smaller than a low voltage side threshold value of the hysteresis comparator 41, the polarity of the hysteresis comparator 41 is reversed, and then the switching element 21 is turned off (non-conductive state). At this time, in order to maintain the electric current which flows through the inductor 23, an electric current flows from GND to the first load 1 through the diode 22. Moreover, the potential of the cathode of the diode 22 (that is, switching voltage Vsw) is 0V. The above-mentioned switching operation is repeated and the switching electric current Im is supplied from Vcc1 or from GND alternately to the first load 1. The linear amplification unit (voltage follower) 3 makes the output voltage Vout of the power supplying apparatus identical with the reference signal Vref (or, output voltage Vout is scaled linearly).
Meanwhile, the second load 30 (for example, another block included in the system) is connected with the negative side power supply V2 of the operational amplifier 31, and the operational amplifier electric current Ic(−) is used as a part of an electric current supplied to the second load 30. In this case, a capacitor 37 with large capacitance is arranged at a location of the negative side power supply V2 to remove influence due to a temporal fluctuation of Ic(−).
In the case of a general power supplying apparatus which has the hybrid configuration including the switching amplification unit 2 (current source) and the linear amplification unit 3 (voltage source), electric power of V2*IC(−) which the linear amplification unit 3 consumes for correcting the output voltage results in a loss to degrade efficiency of a whole of the system. In contrast, according to the exemplary embodiment, the second load 30, for example, another block included in the system reuses the electric power. As a result, it is possible to achieve high efficiency as a whole of the system.
Here, while the configuration that the second load 30 is connected with the negative side power supply V2 of the linear amplification unit 3 is described in the example shown in
According to the power supplying apparatus shown in
Ic=Iout−Im
First, an operation which is carried out in the case that the electric current Im from the switching amplification unit 2 is short in comparison with the electric current Tout which flows through the first load 1 will be described. In this case, the electric current Ic (Ic=Ic(+)) flows from the n type transistor 314 included in the output-stage source follower push-pull amplifier of the linear amplification unit 3, and flows into the first load 1 as a part of Tout.
Next, an operation carried out in the case that the electric current Im from the switching amplification unit 3 is excessive in comparison with the electric current Tout which flows through the first load 1. The electric current Ic (Ic=Ic(−)) flows into the p type transistor 315 included in the output-stage source follower push-pull amplifier of the linear amplification unit 3, and the electric power of V2*Ic(−) is consumed. The electric current Ic(−) is unnecessary for the first load 1 originally, and results in a loss from a view point of the system. By connecting a power supply of another block included in the system as the second load 30 with the terminal V2, it is possible to reuse the electric current Ic(−) within the system, and to reduce the loss as a whole of the system.
Here, it is assumed that the system is a transmitter whose first load 1 is an electric power amplifier. In the case of a transmitter used in the base station of the cellular phone, an output electric power of the electric power amplifier is so large that V2*Ic(−) may reach to several watts. Then, by connecting a driver amplifier, a transceiver IC, a baseband IC, ADC/DAC or the like which is other than the amplifier included in the transmitter as the first load 30, it is possible to use the electric power which has been discarded as the loss as effective electric power, and to reduce power consumption of a whole of the transmitter. Here, IC used in the above is an abbreviation of Integrated Circuit. ADC is an abbreviation of Analog-to-Digital Converter. DAC is an abbreviation of Digital-to-Analog Converter.
As a summary of the above, the power supplying apparatus according to the first exemplary embodiment includes the switching amplification unit to supply the electric power to the first load 1 with high efficiency, and the linear amplification unit with superior accuracy to correct so that the voltage applied to the first load 1 may change linearly according to the input signal waveform. Furthermore, the power supplying apparatus reuses the power loss caused during correcting the voltage as the power supply of another block in the system. Accordingly, the power supplying apparatus has the function to change the output voltage according to the magnitude of the input signal, and has high efficiency and superior linearity.
Here, while the case that the electric current Ic(−) flows into the V2 side in
Moreover, in the first exemplary embodiment described above, configurations of the switching amplification unit 2, the linear amplification unit 3 and the control signal generating unit 4 are not limited to the circuit configuration shown in
The switching amplification unit 2 works as a voltage source and supplies a voltage to the first load 1. The linear amplification unit 3 works as a voltage source, and corrects an output voltage applied to the first load 1 so that it may be identical with an input voltage. The switching amplification unit 2 and the linear amplification unit 3 are connected in series for the first load 1. Electric power is supplied from a power supplying terminal of the linear amplification unit 3 to the second load 30.
The control signal generating unit 4 generates a pulse width modulation signal which has two levels of High and Low based on the reference signal Vref inputted into the power supplying apparatus, and the output voltage Vm, and outputs the pulse width modulation signal to the switching amplification unit 2 as a control signal. The switching amplification unit 2 makes the switching elements 21 and 22 carry out an on/off work on the basis of the control signal. The output voltage Vsw is converted to the voltage Vm by being smoothed by a low pass filter including the inductor 23 and a capacitor 26. The linear amplification unit 3 compares the reference signal Vref and the voltage Vout applied to the first load 1, and outputs a differential voltage Vc. The differential voltage Vc is added with the voltage Vm (hereinafter, voltage Vm may be described as switching voltage Vm) of the switching amplification unit 2 by the transformer 35, and the added voltage is supplied to the first load 1. The second load 30 is connected with the power supplies V1 and V2 of the linear amplification unit 3. In this case, the second load 30 is corresponding to another block included in the system.
Hereinafter, an operation according to the second exemplary embodiment of the present invention will be described in detail with reference to
As shown in
The switching amplification unit 2 has an inverter configuration including the p type switching MOSFET 21, and the n type switching MOSFET 22, and reverses the control signal provided by the control signal generating section 4 and inputs the reversed control signal into the switching MOSFETs 21 and 22. When the control signal is High, the switching MOSFET 21 is turned on (conductive state), and the switching MOSFET 22 is turned off (non-conductive state), and an electric current flows from Vcc1, and the electric current is outputted in a direction toward the first load 1 through the inductor 23. At this time, the output voltage Vsw is corresponding to Vcc1. On the other hand, when the control signal is Low, the switching MOSFET 21 is turned off (non-conductive state), and the switching MOSFET 22 is turned on (conductive state). Then, in order to maintain an electric current which flows through the inductor 23, a current flows from GND in a direction toward the first load 1. At this time, the output voltage Vsw is 0. The pulse-shaped output voltage Vsw obtained by carrying out the above-mentioned operation is smoothed by the low pass filter including the inductor 23 and the capacitor 26, and the smoothed output voltage Vsw is outputted as the voltage Vm. Moreover, since the switching amplification unit 2 does not consume any electric power in an ideal state, it is possible to supply the voltage Vm to the load with high power-efficiency. In the case that the clock frequency fclk of the sample-hold circuit 43 is high sufficiently, the output voltage Vm of the switching amplification unit 2 obtained by carrying out the above-mentioned operation is approximately equal to the reference signal Vref. However, in the case that the clock frequency fclk is too high, a switching rate of the switching amplification unit 2 also is high, and power loss caused by the parasitic capacitors of the switching MOSFETs 21 and 22 is large. That is, since it is impossible to make fclk high too much in order to maintain high power-efficiency, the output voltage Vm includes residual switching noise, and consequently the output voltage Vm is not identical with the reference signal Vref.
In the linear amplification unit 3, the reference signal Vref is inputted into the operational amplifier 31 which composes a feed back amplifier, and the voltage Vout applied to the load 1 is fed back to the operational amplifier 31, and then the operational amplifier 31 outputs the differential voltage Vc. The differential voltage Vc is inputted into a first side coil of the transformer 35 whose second side coil is connected with the output of the switching amplification unit 2. At this time, the linear amplification unit 3 works so as to amplify only an AC component and so as to make a DC current not flow through the transformer 35. Hereinafter, a reason why only the AC component is amplified will be described. For example, the operational amplifier 31 of the linear amplification unit 3 shown in
The second load 30 (for example, another block included in the system) is connected with the negative side power supply V2 of the operational amplifier 31, and Ic(−) is used as a part of the electric current supplied to the second load 30. At this time, a capacitor 37 with large capacitance is arranged at a location of the negative side power supply V2 to remove influence due to a temporal fluctuation of Ic(−).
In the case of a general power supplying apparatus which has the hybrid configuration including the switching amplification unit 2 (voltage source) and the linear amplification unit 3 (voltage source), electric power of IC(−)*V2 which the linear amplification unit 3 consumes for correcting the output voltage results in a loss to degrade efficiency of a whole of the system. In contrast, according to the exemplary embodiment, by the second load 30 (for example, another block included in the system) reusing the electric power, it is possible to achieve high efficiency of a whole of the system.
Here, while the configuration that the second load 30 is connected with the negative side power supply V2 of the linear amplification unit 3 is described in the example shown in
Here, as mentioned above, in the case that electric potential of the power supply V2 is fixed to an ideal value, it is not essential to arrange the capacitor 37 for stabilizing the voltage. The reason why the capacitor 37 with large capacitance is required is that, in the case that there is a possibility that potential applied to the second load 30 fluctuates due to influence caused by a parasitic electric resistance or the like, it is necessary to suppress potential fluctuation ΔV (ΔV=ΔQ/C≈0) by using the capacitor with large capacitance. In this case, while the displacement current flows, a change component ΔQ of the charge saved in the capacitor 37 is switched with the power supply V2 or is supplied to the second load 30. Accordingly, the electric charge charged by Ic(−) does is not useless, and the effect of the present invention is maintained. In other words, the displacement current flows through the capacitor 37, but energy of Ic(−) is not consumed by the capacitor 37 and is consumed minutely by the parasitic electric resistance. Accordingly, it is conceivable that almost all energy is reused by the second load 30.
At an output terminal Vout of the power supplying apparatus shown in
Vc=Vout−Vm
While the switching amplification unit 2 carries out the high-efficient switching amplification so that the output voltage Vm may be near to the output voltage Vout of a whole of the power supplying apparatus, Vout is generally not identical to Vm. The linear amplification unit 3 has a feed back loop so that the output Vout of the power supplying apparatus and the reference signal Vref may be identical (or Vout is scaled linearly). Accordingly, in the case that the voltage Vm supplied by the switching amplification unit 2 is low in comparison with Vout which should be applied to the first load 1 (Vm<Vout), the electric current Ic (Ic=Ic(+)) flows from the n type transistor 314 included in the output-stage source follower push-pull amplifier of the linear amplification unit 3, and the voltage Vc (Vc=Vout−Vm(>0)) is generated in the first side of the transformer 35. The voltage Vc is transferred to the second side of the transformer 35, and then the transferred Vc, and Vm are added so that the desired output voltage Vout is generated. On the other hand, in the case that the voltage Vm supplied by the switching amplification unit 2 is high in comparison with Vout applied to the first load 1 (Vm>Vout), the electric current Ic (Ic=Ic(−)) flows into the p type transistor 315 included in the output-stage source follower push-pull amplifier of the linear amplification unit 3, and the voltage Vc (Vc=Vout−Vm(<0)) is generated in the first side of the transformer 35. The voltage Vc is transferred to the second side of the transformer 35, and then the transferred Vc, and Vm are added so that the desired output voltage Vout is generated. The electric current Ic(−) is unnecessary for the first load 1 originally, and results in a loss from a view point of a whole of the system. By connecting a power supply of the second load 30 (for example, another block included in the system) with a terminal V2, it is possible to reuse the electric current Ic(−) within the system, and to reduce the loss as a whole of the system.
Here, it is assumed that a transmitter, whose first load 1 is a power amplifier. In the case of a transmitter used in the base stations of the cellular phone, an output power of the power amplifier is so large that V2*Ic(−) may reach to several watts in some cases. Then, by connecting a driver amplifier, a transceiver IC, a baseband IC, ADC/DAC or the like which is other than the amplifier and which is included in the transmitter as the second load 30 with the terminal V2, it is possible to use the electric power which has been discarded as the loss as an effective electric power, and to reduce power consumption of a whole of the transmitter.
As a summary of the above, the power supplying apparatus according to the second exemplary embodiment includes the switching amplification unit to supply the electric power to the first load 1 with high efficiency, and the linear amplification unit with superior accuracy to correct so that the voltage applied to the first load 1 may change linearly according to the input signal waveform. Furthermore, the power supplying apparatus reuses the power loss caused during correcting the voltage as the power supply of another block in the system. Accordingly, the power supplying apparatus has the function to change the output voltage according to the magnitude of the input signal, and has high efficiency and superior linearity.
Here, while the case that the electric current Ic(−) flows into the V2 side in
Moreover, while, in the example of
Moreover, in the second exemplary embodiment described above, configurations of the switching amplification unit 2, the linear amplification unit 3 and the control signal generating unit 4 are not limited to the circuit configuration shown in
Since a configuration and an operation principle of a power supplying apparatus are the same as ones described by use of
According to the transmitter of the exemplary embodiment, an electric power amplifier is connected as the first load 1 connected to the power supplying apparatus. The amplitude signal 9 of the input modulation signal 8 is inputted to the power supplying apparatus as the reference signal Vref. A waveform of the inputted amplitude signal 9 is amplified linearly and the amplified amplitude signal 9 is outputted as the output voltage Vout (waveform indicated by a code 11 in
The second load 30 (for example, another block included in the transmitter) is connected to the negative side power supply V2 of the linear amplification unit 3 included in the power supplying apparatus. And, Ic(−) is used as a part of the electric current supplied to the second load 30. At this time, the capacitor 37 with large capacitance is arranged at a location of the negative side power supply V2 of the linear amplification unit 3 to remove influence due to a temporal fluctuation of Ic(−).
By carrying out the operation mentioned above, the power supplying apparatus supplies the first load 1 (for example, the electric power amplifier) with necessary and minimum electric power according to the amplitude of the inputted modulation signal 8. As a result, since useless electric power is not generated in comparison with a case that the power supplying apparatus supplies a constant voltage, it is possible to operate with high power-efficiency. Moreover, since the second load 30 (for example, another block included in the transmitter) uses useless electric power caused at a time when the power supplying apparatus generates the modulation voltage Vout, it is possible to realize quite high power-efficiency as a whole of the transmitter.
As another block included in the transmitter, a driver amplifier, a transceiver IC, a baseband IC, ADC/DAC or the like is exemplified. Since electric power consumption of the electric power amplifier is quite large in general in comparison with power consumption of another block included in the transmitter, even electric power which has the same order of magnitude of the electric power consumption for correcting an error of the output voltage Vout in the power supplying apparatus can be a power supply sufficiently effective for another block.
Moreover, while the transmitter shown in
A case that “electric power amplifier” is connected as the first load 1 connected with the power supplying apparatus, and “driver amplifier” of the electric power amplifier is connected as the second load 30 in the transmitter of the exemplary embodiment is exemplified.
A configuration and an operation principle of the power supplying apparatus are almost the same as ones described by use of
Since the following formula is satisfied at the output terminal Vout of the power supplying apparatus shown in
Ic=Iout−Im
when the switching electric current Im is excessive in comparison with the output electric current Tout which flows through the first load 1, the output electric current Ic of the linear amplification unit 3 flows reversely (that is, Ic=Ic(−)), and starts flowing in a direction toward the linear amplification unit 3. When the voltage applied to the electric current detecting resistor 7 by the output electric current Ic of the linear amplification unit 3 is smaller than a low voltage side threshold value of the hysteresis comparator 41, a polarity of the hysteresis comparator 41 is reversed, and the switching element 21 is turned off (non-conductive state). At this time, in order to maintain the electric current which flows through the inductor 23, an electric current flows at the second side of the transformer 25 from Voffset to the first load 1 through the diode 22. Then, the electric potential Vsw of the cathode of the diode 22 is Voffset. The above-mentioned switching operation is repeated, and the diode 24 or the diode 22 alternately supplies the electric current Im to the load 1. In the operation of the power supplying apparatus, the positive side power supply voltage V1 and the negative side power supply voltage V2 of the linear amplification unit 3 are shifted typically by an amount of Voffset.
The amplitude signal 9 of the input modulation signal 8 is inputted to the power supplying apparatus as the reference signal Vref. According to the above-mentioned operation principle of the power supplying apparatus, an output voltage is generated by amplifying a waveform of the inputted amplitude signal 9, and the output voltage is shifted by an amount of Voffset and the shifted output voltage is outputted as the output voltage Vout (waveform indicated by a code 11 in
A driver amplifier corresponding to the second load 30 is connected to the negative side power supply V2 of the linear amplification unit 3 included in the power supplying apparatus through a choke inductor 36. And, Ic(−) is used as a part of an electric current supplied to the driver amplifier. At this time, the capacitor 37 with large capacitance is arranged at a location of the negative side power supply V2 of the linear amplification unit to remove influence of a temporal fluctuation of Ic(−). The modulation signal 8 is inputted to the driver amplifier, and an output of the driver amplifier is inputted to the electric power amplifier.
By carrying out the above-mentioned operation, the power supplying apparatus supplies the electric power amplifier with only the necessary and minimum electric power according to the amplitude of the inputted modulation signal 8. As a result, since useless electric power is not generated in comparison with a case that the power supplying apparatus supplies a constant voltage, it is possible to operate with high power-efficiency. Moreover, since the second load 30 (for example, a driver amplifier included in the transmitter) uses useless electric power caused at a time when the power supplying apparatus generates the modulation voltage Vout, it is possible to realize quite high power-efficiency as a whole of the transmitter.
Furthermore, according to the transmitter of the exemplary embodiment, since the output voltage is shifted by an amount of the offset voltage Voffset, and also the voltages V1 and V2 of the linear amplification unit 3 can be adjusted according to the offset voltage, design flexibility according to an operational condition of the block connected to the second load 30 is improved. Moreover, it is desirable to set the offset to Vout to some extent from a view point of avoiding influence caused by noise and non-linearity of the power supplying apparatus on the output signal 12 of the electric power amplifier which operates according to the ET method.
Here, while the case that the driver amplifier is connected as the second load 30 is exemplified in
Moreover, while the transmitter shown in
As understood from
As a case that the configuration is effective in particular, for example, a case that “power amplifier” is connected as the first load 1 as shown in
Here, while the second load 30A is connected with the negative side power supply V2 of the linear amplification unit 3 according to the example shown in
Moreover, it is quite apparent that the second load 30A described above is applicable to the second load 30 according to the first to the fourth exemplary embodiments.
According to the sixth exemplary embodiment described above, since the linear amplification unit 212 reuses electric power loss (electric power based on an electric current which flows into the linear amplification unit 212 at the time of the correcting) caused at a time when correcting the output voltage as a power supply of the second load 216 (for example, another block included in a system), it is possible to improve electric power efficiency.
Each exemplary embodiment described above can be applied to a terminal or a base station of the cellular phone, the wireless LAN, or WiMAX (Worldwide Interoperability for Microwave Access) or can be applied to a transmitter of the terrestrial digital broadcasting office.
While the present invention has been described with reference to the exemplary embodiment, the invention of the present application is not limited to the above-mentioned exemplary embodiment. Various changes which a person skilled in the art can understand can be added to the composition and the detail of the present invention in the scope of the present invention.
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2011-046502 filed on Mar. 3, 2011, the disclosure of which is incorporated herein in its entirety by reference.
A part of or a whole of the exemplary embodiment mentioned above can be described as the following supplementary notes, but the present invention is not limited to the following supplementary notes.
Number | Date | Country | Kind |
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2011-046502 | Mar 2011 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2012/055499 | 2/28/2012 | WO | 00 | 9/3/2013 |