JPH0846448A - Power amplifier - Google Patents

Abstract

PURPOSE:To realize a power amplifier capable of performing efficient power amplification by minimizing power loss in the output transistor of an amplifier. CONSTITUTION:Switching voltage VBA is generated by providing a boosting switching power source part 24 and boosting power source voltage VB and this switching voltage is supplied to first and second amplifiers 30 and 32. In accordance with the output signals outputted from the first and second amplifiers 30 and 32, a boosting 15yW switching power source part 24 is controlled by a power source control part 34 and the level of the switching voltage VBA is adjusted. By adjusting the switching voltage level according to the output signals, the voltage VCE between the collector/emitter of the output transistors of the first and second amplifiers 30 and 32 can always be maintained almost constant, the power loss inside the output transistor is reduced and the efficiency of power amplification can remarkably be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier device suitable for an output stage of an audio amplifier.

[0002]

2. Description of the Related Art Conventionally, for example, a power amplifier is used in an output stage of an audio power amplifier for supplying power to a load such as a speaker.

In such a power amplification device, it is required to supply as much output power as possible to the load, and there is known a configuration in which a boosting type switching power supply unit is provided to boost the power supply voltage. .

A conventional power amplifier device will be described with reference to FIG.

FIG. 10 shows a SEPP (Single Ended Push-
1 shows a power amplification device having a pull-type output stage.

In the figure, an AC input signal supplied from a signal source 16 is supplied to an amplifier 10 via an input terminal IN, and an output signal amplified by the amplifier 10 is supplied to a load RL via an output terminal OUT. Is output to. The load RL is, for example, a speaker, and a sound can be generated when a predetermined current based on the output signal flows through the load RL.

The amplifier 10 is, for example, a class B amplifier and has an NPN type output transistor Q20 whose collector side is connected to + Vcc and a PNP type output transistor Q21 whose collector side is connected to -Vcc.

The step-up switching power supply section 20 includes a coil L1, a diode D1, a capacitor C1 and a switch S.
It is a so-called switching regulator which is composed of W1 and which generates an upper side (positive polarity) voltage + Vcc based on the power supply voltage VB and supplies it to the amplifier 10. The step-up switching power supply section (hereinafter referred to as the inverting step-up switching power supply section) 22 whose polarity is reversed is composed of a coil L2, a diode D2, a capacitor C2 and a switch SW2, and is based on the power supply voltage VB. Voltage) -Vcc
Is a switching regulator for generating and supplying to the amplifier 10.

On the upper (positive) power supply side of the amplifier 10,
A first power supply controller 80 is provided. One input terminal of the first power supply controller 80 is connected to the reference power supply (Vref), and the other input terminal is connected to the upper power supply (+ Vcc).

The first power supply controller 80 controls the reference voltage Vref.
And the upper power supply voltage + Vcc. Then, a predetermined comparison output corresponding to the difference between the two is output to the switch SW1 as a control signal for controlling the on / off of the switch SW1 of the step-up switching power supply unit 20.

Here, the control signal is a signal for changing the on / off ratio (duty ratio) of the switch SW1. When the switch SW1 is turned on / off, a counter electromotive force is generated in the coil L1, and as a result, the upper switching voltage + Vcc boosted by a predetermined amount from the power supply voltage + VB can be generated.

On the other hand, a second power supply controller 84 is provided on the lower (negative) power supply side of the amplifier 10. This second
In the power supply control unit 84, one of its input terminals is a reference power supply (-
Vref) and the other input terminal is the lower power supply (-V
cc) is connected.

The second power supply controller 84 has a reference voltage -Vref.
And the lower power supply voltage −Vcc. Then, similarly to the first power supply control unit 80, a control signal for controlling ON / OFF of the switch SW2 of the inverting boost type switching power supply unit 22 is output to the switch SW2.

Also in the inverting boost type switching power supply section 22, duty of ON / OFF of the switch SW2 is controlled,
By using the counter electromotive force generated in the coil L2,
Lower power supply voltage boosted by a predetermined amount from power supply voltage + VB-
Vcc is generated.

[0015]

However, as shown in FIG.
In the conventional power amplifier as shown in FIG. 1, the power supply voltages + Vcc and -Vcc supplied to the amplifier 10 are determined irrespective of the voltage level of the output signal.
There is a problem that the power loss in the output transistors Q20 and Q21 is large.

That is, as shown in FIG. 11, the collectors of the output transistors Q20 and Q21 are constantly supplied with the power supply voltage +
Vcc and -Vcc are supplied. On the other hand, the emitters of the output transistors Q20 and Q21 output output signals of a predetermined voltage according to the input signal applied to the bases.

Therefore, output transistors Q20 and Q2
Power supply voltage + Vcc, -V between the collector and emitter of 1
The voltage obtained by subtracting the output signal voltage from cc is applied. The power of the value obtained by multiplying the collector-emitter voltage VCE by the output current becomes the power loss of the output transistor.

Therefore, the collector-emitter voltage VCE
Varies depending on the output voltage of the output signal, and particularly when VCE is large, that is, when the output voltage is small, the power loss in the output transistors Q20 and Q21 becomes extremely large.
It reduced the efficiency of power amplification.

Further, since the output transistors Q20 and Q21 generate heat due to power loss, expensive transistors or cooling means capable of withstanding this heat generation have been required.

Further, since the power supply voltages + Vcc and -Vcc are supplied to the collectors of the output transistors Q20 and Q21, there is a problem that the breakdown voltage between the collector and the emitter of each transistor is required to be 2 Vcc or more.

The present invention has been made to solve these problems, and an object of the present invention is to realize a power amplification device capable of performing efficient power amplification by minimizing the power loss in the output transistor of the amplifier. And

[0022]

In order to achieve the above object, the power amplification device according to the present invention has the following features.

A step-up switching power supply unit for boosting an output voltage of a power supply to generate a power supply voltage in response to a predetermined control signal, an amplifier for amplifying an input signal using the power supply voltage as an operating voltage, and the switching power supply unit. A first input to which an output terminal of the amplifier is connected, and a second input to which an output terminal of the amplifier is connected via a reference voltage.
A power supply control unit for comparing signals applied to the inputs and applying an output signal corresponding to the difference to the switching power supply unit as the control signal.

The power supply control section has a first power supply control section for controlling an upper voltage of the power supply voltage supplied to the amplifier and a second power supply control section for controlling a lower voltage. The boosting switching power supply unit responds to a control signal output from the second power supply control unit and a boosting switching power supply unit that boosts an upper power supply voltage according to a control signal output from the first power supply control unit. And an inverting boost type switching power supply unit for boosting the lower power supply voltage.

Further, the step-up type switching power supply section is
A coil whose one end side is connected to a power source, a diode which is connected in series to the other end side of the coil and which allows a forward current to flow from the power source toward the amplifier, and a capacitor connected to the output side of the diode, A switch having one end connected to a connection point between the coil and the diode and the other end grounded, the switch being turned on / off according to a control signal from the first power supply control unit;
The inverting boost type switching power supply unit is a switch that is turned on / off in response to a control signal from the second power supply control unit, and has a switch whose one end side is connected to a power supply and a serial connection to the other end side of the switch. A diode for flowing a forward current from the amplifier toward the power supply, and a capacitor connected to the amplifier side of the diode,
A coil having one end connected to a connection point between the switch and the diode and the other end grounded.

Another power amplification device according to the present invention is
It has the following features.

That is, in accordance with a predetermined control signal, a step-up switching power supply unit for boosting an output voltage of a power supply to generate a power supply voltage, and a first amplification circuit for amplifying input signals having opposite phases with the power supply voltage as an operating voltage. First and second amplifiers, and the first
And an adder circuit for adding the output signals of the second amplifier, a first input to which the output terminal of the switching power supply unit is connected, and a second input to which the output terminal of the circuit is connected via a reference voltage. And a power supply controller for comparing the signals applied to the first and second inputs and applying an output signal corresponding to the difference to the switching power supply as the control signal.

Further, in the power amplifier, a pair of input terminals, a pair of differential output terminals connected to the inputs of the first and second amplifiers, and a DC level of the pair of differential output terminals are determined. A first differential amplifier having a common input terminal, a non-linear addition circuit for performing non-linear addition of output signals obtained at the pair of output terminals, an output signal of the linear addition circuit and a reference voltage are compared, and a difference between them is calculated. And a comparator circuit for applying a corresponding output signal to the common input terminal.

The step-up switching power supply unit is connected in series with a coil whose one end is connected to the power supply, and is connected in series to the other end of the coil so that a forward current flows from the power supply toward the first and second amplifiers. , A capacitor that is connected to the output side of the diode, one end side is connected to the connection point between the coil and the diode,
A switch whose other end is grounded and which is turned on / off in response to a control signal from the first power supply controller.

[0030]

In the power amplifying device according to the present invention, the step-up switching power supply unit is provided to boost the power supply voltage, and the level of the power supply voltage is adjusted according to the output signal output from the amplifier. Then, the level of the power supply voltage is adjusted according to the output signal, and the collector-emitter voltage VCE of the output transistor of the amplifier is always maintained substantially constant.

As a result, the collector-emitter voltage V
It is possible to reduce the power loss inside the output transistor caused by the large CE, and it is possible to dramatically improve the efficiency of power amplification.

On the other hand, by boosting the power supply voltage, it becomes easy to control the operation of the output transistor of the amplifier. Further, it is possible to obtain a power amplifier device that can supply large power to a load extremely efficiently without changing the power source and that has low power consumption.

Further, in addition to the structure of the step-up type switching power supply section, a first amplifier for further amplifying an input signal and outputting it to an output terminal, and a second amplifier for inverting and amplifying the input signal and outputting it to an output terminal. By providing an AC output signal of opposite phase at both ends of the load RL, BTL (Balanced
Transformerless) drive is possible.

Therefore, even with a single power supply, the maximum power can be increased, while the power consumption of the power amplifier can be reduced, which is extremely advantageous for downsizing the device.

Further, a differential amplifier which automatically adjusts the DC level at the output terminal and outputs a predetermined signal whose polarities are inverted to each other is provided to the first amplifier and the second amplifier, and a non-linear addition circuit. Then, the DC level of the output of the differential amplifier is automatically adjusted according to the result of the nonlinear addition process. As a result, the DC level of the output can be changed by following the change in the output. Then, the non-linear adder circuit can clamp the DC voltage at the output terminals on both sides of the load so as not to fall below a predetermined voltage value, and reduce the crossover distortion of the output signal.

It should be noted that the half-wave driving requires only one signal path in the device, and the power supply voltage can be constantly boosted with only a single boosting type switching power supply. Therefore, the power consumption is further reduced, and highly efficient power amplification can be realized.

[0037]

【Example】

(Embodiment 1) FIG. 1 is a diagram showing a circuit configuration of a power amplifier device according to an embodiment of the present invention. Note that, in FIG. 1 and the drawings described below, the same parts as those already described are denoted by the same reference numerals and the description thereof will be omitted.

The AC input signal supplied from the signal source 16 is supplied to the amplifier 10 via the input terminal IN. The output signal amplified by the amplifier 10 is output to the load RL via the output terminal OUT.

On the upper (positive polarity) power supply side of the amplifier 10,
A first power supply controller 12 is provided. One input terminal of the first power supply control unit 12 is connected to the reference power supply (VX) via
It is connected to the output terminal OUT side. The other input terminal is connected to the output side of the step-up switching power supply unit 20.

The first power supply controller 12 outputs the value obtained by adding the reference voltage VX to the output voltage and the upper (switching) power supply voltage + V.
Compare with BA. The switching voltage + VBA supplied to the amplifier 10 is always VX with respect to the output signal voltage.
A control signal for increasing the value is output. Further, this control signal is, for example, a pulse signal for duty-controlling ON / OFF of the switch SW1 of the step-up switching power supply unit 20. The control signal also controls the boost amount of the upper switching voltage + VBA with respect to the power supply voltage VB.

On the other hand, a second power supply controller 14 is provided on the lower (negative) power supply side of the amplifier 10. This second
One input terminal of the power supply control unit 14 has a reference power supply (VX)
Is connected to the output terminal OUT side. Also,
The other input terminal is an inverting boost type switching power supply unit 22.
Is connected to the output side of.

The second power supply controller 14 compares the output voltage plus the reference voltage VX with the lower power supply voltage -VBB. Then, a control signal for constantly lowering the power supply voltage -VBB supplied to the amplifier 10 with respect to the output signal voltage by VX is output to the switch SW2 of the inverting boost type switching power supply unit 22. The control signal is, for example, on / off of the switch SW2 of the inverting boost type switching power supply unit 22.
It is a pulse signal for duty control, and the boosting amount of the switching voltage -VBB with respect to the power supply voltage -VB is also controlled by this control signal.

With the above configuration, the collectors of the output transistors Q20 and Q21 are supplied with the switching voltages + VBA and -VBB, which are always higher than the voltage level of the output signal by ± VX, as shown in FIG. Will be done.

Therefore, the voltage VCE between the collector and the emitter, which is shaded in the figure, is constantly almost constant. Then, the power loss of the output transistor corresponding to the area of the shaded area in the figure can be made extremely smaller than that of the conventional power amplifier device, as is apparent from the area of the shaded area of FIG. Becomes This makes it possible to dramatically improve the efficiency of power amplification.

Further, by boosting the power supply voltage, it becomes easy to control the operation of the output transistor of the amplifier. Further, it is possible to obtain a power amplifier device that can supply large power to a load extremely efficiently without changing the power source and that has low power consumption.

Since the device can be downsized and the power consumption can be reduced, the power amplification device of this embodiment can be used for portable audio equipment and the like.

(Embodiment 2) In FIG. 3, a first differential amplifier 40 includes an input terminal IN1 and a (inverting) input terminal IN2.
, And two differential output terminals respectively connected to the first amplifier 30 and the second amplifier 32, and a common input terminal C that determines the DC level of the two differential output terminals.

An input signal from the signal source 16 is supplied between the input terminal IN1 and the inverting input terminal IN2. The first differential amplifier 40 amplifies the input signal with a gain determined by the ratio of the resistors R1 and R2, and outputs differential output signals having opposite phases from the two differential output terminals. The mutually output differential output signals having opposite phases are output to the first amplifier 30 and the second amplifier 32 which form a BTL amplifier.

Output terminals OUT1 and OUT2 are connected to the output sides of the first and second amplifiers 30 and 32, respectively. The first and second amplifiers 30 and 32 are connected to the load RL.
Is BTL driven.

Further, a non-linear addition circuit 44 which will be described later is provided.
From the first and second amplifiers 30, 32 to the output terminal OU
The two output signals respectively output to T1 and OUT2 are substantially added, and fluctuations of the two output signals are clamped to a predetermined value or less.

The second differential amplifier 36 is a nonlinear addition circuit 4
4 is connected to the output side of the first differential amplifier 40 and outputs a comparison output signal corresponding to the difference between the output signal from the nonlinear addition circuit 44 and the reference voltage VBC to the common input terminal C of the first differential amplifier 40.

The adder circuit 42 has two output terminals OUT.
Two output signals respectively output to 1 and OUT2 are added, and a predetermined addition signal is supplied to one input terminal of the power supply control unit 34 via the reference voltage VX.

The other input terminal of the power supply control unit 34 is connected to the output side of the step-up switching power supply unit 24.

The power supply control unit 34 adds the reference voltage VX to the output voltage of the adder circuit 42 and the switching voltage + V.
Compare with BA. Then, it outputs a control signal for constantly increasing the switching voltage + VBA supplied to the amplifiers 30 and 32 by VX with respect to the output signal voltage. The control signal is, for example, a pulse signal for duty-controlling ON / OFF of the switch SW1 of the step-up switching power supply unit 24, and the control signal also controls the step-up amount of the switching voltage + VBA with respect to the power supply voltage VB.

The circuit configuration of the step-up switching power supply section 24 is similar to that of the step-up switching power supply section 20 of FIG. 1, and is composed of a coil L3, a capacitor C3, and a switch SW3.

Next, a concrete circuit configuration example of the first differential amplifier 40 and the first amplifier 30 and the second amplifier 32 will be described with reference to FIG.

The first differential amplifier 40 has two input terminals I
It has PNP type transistors Q1 and Q2 whose bases are connected to N1 and IN2, respectively, and a variable constant current source I1. Here, the emitters of the transistors Q1 and Q2 are connected to each other, and the variable constant current source I1 and the constant current source I2 whose one end is connected to the switching power source (+ VBA) are connected to the connection point. Also, the transistor Q
The 1st amplifier 30 and the 2nd amplifier 32 are connected to the collector side of 1 and Q2.

The first and second amplifiers 30 and 32 respectively include driving circuits 50 and 54 and a first SEPP circuit (single circuit).
ended push-pull) 52 and a second SEPP circuit 56. And, in particular, the first and second SEPPs
BTL driving load RL by circuits 52 and 56
An amplifier is configured.

The drive circuits 50 and 54 are constant current sources I3, one end of which is connected to the switching power source (+ VBA), respectively.
I4, two diodes, NPN transistor Q
The collectors of Q3 and Q4 are connected in series in this order. The bases of the transistors Q3 and Q4 are connected to the collectors of the transistors Q1 and Q2, respectively, and the differential output signal from the first differential amplifier 40 is supplied.

The first SEPP circuit 52 has an NPN whose base is connected to the connection point of the constant current source I3 and the diode.
Type output transistor Q5 and PNP whose base is connected to the connection point of the diode and the collector of transistor Q3
Mold output transistor Q6.

The collector of the output transistor Q5 is connected to the switching power supply (+ VBA), and the emitter of the output transistor Q5 is connected to the emitter of the output transistor Q6. And the output transistor Q5
One end of the load RL is connected to the emitter of the output transistor Q6 via the output terminal OUT1. The emitter of the output transistor Q6 is grounded.

The second SEPP circuit 56 has the same structure as the first SEPP circuit 52, and is composed of an NPN type output transistor Q7 and a PNP type output transistor Q8.
It is connected to a drive circuit (bias circuit) 54. Then, at the connection point of the emitters of the output transistor Q7 and the output transistor Q8, the load R is connected via the output terminal OUT2.
The other end of L is connected.

The operation of the circuit configuration shown in FIG. 4 will be described below.

First, when an input signal from the signal source 16 of FIG. 3 is supplied to the inverting input terminal IN2, it is amplified in accordance with the input signal, and differential output signals having mutually opposite phases are supplied to the transistors Q1 and Q2. It is output from the collector side.

The transistors Q3 and Q4 operate according to the differential output signal output to their bases, and the first and second transistors Q3 and Q4 operate.
A signal corresponding to the differential output signal is applied to the SEPP circuits 52 and 56.

In the first and second SEPP circuits 52 and 56, when both the PNP type output transistor Q6 and the NPN type output transistor Q7 are on, the NPN type output transistor Q5 and the PNP type output transistor Q8.
And are off.

Conversely, when both the output transistors Q6 and Q7 are off, the output transistors Q5 and Q8 are on.

Then, a predetermined alternating current is supplied to the load RL.

As described above, in this embodiment, the load RL is set to B.
By the TL driving, a large power can be output with a single power source, while the power consumption of the power amplification device can be reduced, which is extremely advantageous for downsizing the device.

Next, the nonlinear adder circuit 44 and the second
The configuration of the differential amplifier 36 will be described with reference to FIG.

In the nonlinear addition circuit 44, the output terminal OUT
1 and OUT2, resistors R10 and R1 of equal value
1 and 1 are connected in series.

A diode D10 and a diode D11 are further connected in series between the output terminals OUT1 and OUT2. The anode sides of the diodes D10 and D11 are connected to the output terminals OUT2 and OUT1 sides,
The cathode side of the diode D10 and the cathode side of the diode D11 are connected. Further, the connection point PR between the resistors R10 and R11 and the connection point PD between the diodes D10 and D11 are connected to each other.

One input terminal of the second differential amplifier 36 is
It is connected to the connection point PD of the diodes D10 and D11. The other input terminal of the second differential amplifier 36 is connected to the reference power source (VBC).

The nonlinear addition circuit 44 has an output terminal OUT.
When the absolute value of the output voltage difference (V01-V02) at 1 and OUT2 is 2VF (VF = diode forward voltage) or less, the addition operation is performed. That is, in the section below 2VF, the slope of the straight line is 1/2 as shown in FIG.
Then, by the action of the resistors R10 and R11, VC = (V01 +
It operates as a V02) / 2 adder. The action of the diodes D10 and D11 prevents the absolute value of (V01-V02) from becoming VF or less. Also, 2
When the voltage exceeds VF, the diodes D10 and D11
One of the two is turned on, and the non-linear addition circuit 44 operates as a circuit for clamping the lower voltage.

The two input terminals of the second differential amplifier 36 are imaginary shorts, and the voltage levels of the two input terminals are compared. Then, the current amount of the variable constant current source I1 of FIG. 4 is set so that these two voltage levels become equal (that is, the voltage VD at the connection point PD of the diodes D10 and D11 becomes equal to the reference voltage VBC). Control.

When the amount of current in the variable constant current source I1 in FIG. 4 changes, the transistors Q1 and Q2 of the first differential amplifier are changed.
The amount of current between the emitter and collector of the transistor changes, which causes the transistor Q built in the bias circuits 30 and 32.
3, the base voltage of Q4 changes.

As a result, the base voltages of the output transistors Q5 and Q6 and the output transistors Q7 and Q8 change, and the amount of change in the DC voltage at the output terminals OUT1 and OUT2 is controlled to be equal.

Here, assume that the voltage V01 having the level shown in FIG. 7A is generated at the output terminal OUT2 and the voltage V02 having the level shown in FIG. 7B is generated at the output terminal OUT1. Take for example.

First, in the period of t1, the first time in FIG.
It shows a state in which the output transistor Q6 of the amplifier and the output transistor Q7 of the second amplifier are on. The voltage V01 level at the output terminal OUT2 rises from the reference voltage VBC as shown in FIG. 7 (a).

From the time when V01 rises and the absolute value of (V01-V02) exceeds 2VF, the above-mentioned non-linear addition circuit 44 performs the clamp operation. Therefore, the level of the voltage V02 at the output terminal OUT1 is fixed at a voltage level lower than VBC by VF and does not drop below (VBC-V02).

During the next period of t2, the output transistor Q5 of the first amplifier and the output transistor Q8 of the second amplifier are on. Contrary to the period t1, the voltage V02 level at the output terminal OUT1 is the reference voltage V2.
Rise from BC. On the other hand, the level of the voltage V01 at the output terminal OUT2 is fixed at a voltage level lower than VBC by VF and does not drop below (VBC-V01).

Then, as described above, the second differential amplifier 36
Thus, the voltage VD at the connection point PD of the diodes D10 and D11 is controlled to be equal to the reference voltage VBC.

Next, a configuration example of the adder circuit 42 of FIG. 3 will be described with reference to FIG.

The bases of the NPN transistors Q11 and Q12 are connected to both ends of the load RL shown in FIG. 3 via the input terminals 60 and 62, respectively. Transistor Q11,
Both collectors of Q12 are connected to a predetermined power source + V. The emitter is connected to a predetermined current source CS,
An output terminal 64 is provided at a connection point between the emitters of the two transistors Q11 and Q12 and the current source CS.
Then, the addition signal obtained by adding the two output signals is output from the output terminal 64, and is supplied to the input terminal of the power supply control unit 34 via the predetermined reference power supply (VX) shown in FIG. ing.

In the power supply control unit 34 of FIG. 3, the voltage which is always higher than the voltage level of the output signal supplied to the load RL by the reference voltage VX and the switching voltage + VBA boosted by the switching power supply unit 24 become equal. Then, the switching power supply unit 24 is controlled.

According to this embodiment, as shown in FIGS. 7A and 7B, the level + VBA of the switching voltage supplied to the first and second amplifiers can be adjusted according to the output signal. . As a result, the collector-emitter voltage VCE of the output transistors of the first and second amplifiers can always be kept substantially constant. Therefore, the power loss inside the output transistor can be reduced, and highly efficient power amplification can be realized. Furthermore, since the power supply voltage is boosted,
The operation control of the output transistor is easy.

Further, as described above, in the present embodiment, since the lower side voltage is clamped by using the non-linear addition circuit 44 and the second differential amplifier 36, the load RL is grounded as a reference. In the case of seeing, the AC signal as shown in FIG. 7C is applied, and the load RL is normally driven.

Therefore, even with a single power source (VB), the dynamic range can be extremely widened to a maximum of 2 Vcc (Vcc is the maximum voltage that can be boosted). Then, the power supply voltage can be boosted by only a single boosting type switching power supply.

Therefore, the power consumption is small and highly efficient power amplification can be realized, which is advantageous for downsizing of the device. Further, as in the first embodiment, the device can be downsized and the power consumption can be reduced, so that the power amplification device of the present embodiment can be used for a portable audio device or the like.

As a method of driving the load RL,
Other than the BTL drive described above, a configuration as shown in FIG. 9 may be used. This will be explained below.

The bases of NPN type transistors Q13 and Q14 are connected to the two input terminals 66 and 68, respectively. The collectors of the transistors Q13 and Q14 are both connected to the switching power supply (+ VBA). On the other hand, the switch SW10 is connected to the emitter of the transistor Q13, and the switch SW14 is connected to the emitter of the transistor Q14. The emitters of the transistors Q13 and Q14 are connected to the load RL, respectively.

When a positive half-wave signal is supplied to the input terminal 66, the switch SW10 is turned off and the switch SW11 is turned on. Then, a current flows from the emitter of the transistor Q13 to the switch SW11. on the other hand,
When the positive half-wave signal is supplied to the input terminal 68, the switch SW10 is turned on and the switch SW11 is turned off. As a result, a current flows from the emitter of the transistor Q14 to the switch SW10.

In this way, even if the load RL is driven by a half-wave signal, the power supply voltage can be steadily boosted with only a single step-up switching power supply in the same manner as described above, resulting in extremely low power consumption. It is possible to realize a power amplifier with high power efficiency.

[0094]

As described above, in the power amplifying device according to the present invention, the step-up switching power supply unit is provided to boost the power supply voltage, and the power supply voltage of the amplifier is increased in accordance with the output signal output from the amplifier. Since I am adjusting the level,
The collector-emitter voltage VCE of the output transistor of the amplifier can always be kept substantially constant. As a result, the power loss inside the output transistor can be reduced, and highly efficient power amplification becomes possible.

Then, by boosting the power supply voltage,
The operation of the output transistor of the amplifier can be easily controlled, and a large amount of power can be supplied to the load.

Further, in addition to the configuration of the step-up type switching power supply section, a first amplifier for amplifying an input signal and outputting it to an output terminal and a second amplifier for inverting and amplifying the input signal and outputting it to an output terminal are provided. It is provided so that BTL drive can be performed to generate an AC output signal of opposite phase at both ends of the load RL.

With this configuration, the dynamic range can be widened, the power that can be supplied by a single power source can be increased, and the power loss of the power amplification device can be reduced, which is extremely useful for downsizing the device. Be advantageous.

In addition to the BTL drive, a differential amplifier for outputting a predetermined signal whose polarities are inverted to each other is provided to the first amplifier and the second amplifier, and a non-linear addition circuit. The output signal of one of the first and second amplifiers is clamped according to the result of the non-linear addition process.

As a result, only one signal path in the device is required,
It is possible to steadily boost the power supply voltage with only a single boosting type switching power supply. Therefore, the power consumption is further reduced, and highly efficient power amplification can be realized.

[Brief description of drawings]

FIG. 1 is a schematic circuit configuration diagram of a power amplification device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an output state when the power amplification device of FIG. 1 is used.

FIG. 3 is a schematic circuit configuration diagram of a power amplification device according to a second embodiment of the present invention.

4 is a schematic circuit configuration diagram of a first differential amplifier 40, a first amplifier 30, and a second amplifier 32 of FIG.

5 is a circuit diagram of a non-linear adder circuit 44 and a second differential amplifier 3 of FIG.
6 is a schematic circuit configuration diagram of FIG.

FIG. 6 is a diagram for explaining the operation of the nonlinear addition circuit 44 of FIG.

FIG. 7 is a diagram illustrating an output state when the power amplification device according to the second embodiment is used.

8 is a diagram showing a circuit configuration example of an adding circuit 42 in FIG.

9 is a diagram showing a circuit configuration of a power amplification device having a configuration different from that of FIG.

FIG. 10 is a schematic circuit configuration diagram of a conventional power amplification device.

11 is a diagram illustrating an output state when the power amplification device of FIG. 10 is used.

[Explanation of symbols]

 10 Amplifiers 12, 14, 34 Power Supply Control Unit 16 Signal Source 20, 24 Boosting Switching Power Supply Unit 22 Inverting Boosting Switching Power Supply Unit 30 First Amplifier 32 Second Amplifier 36 Second Differential Amplifier 40 First Differential Amplifier 42 Addition Circuit 44 Non-linear addition circuit

Claims (6)

[Claims] 1. A step-up switching power supply unit that boosts an output voltage of a power supply to generate a power supply voltage according to a predetermined control signal, an amplifier that amplifies an input signal using the power supply voltage as an operating voltage, and the switching. Comparing signals applied to the first and second inputs, which has a first input connected to an output terminal of a power supply unit and a second input connected to an output terminal of the amplifier via a reference voltage And a power supply control unit that applies an output signal according to the difference to the switching power supply unit as the control signal. 2. The power amplification device according to claim 1, wherein the power supply control unit controls a first power supply control unit that controls an upper voltage of a power supply voltage supplied to the amplifier, and a lower power control unit that controls a lower voltage. A booster switching power supply unit for boosting an upper power supply voltage in accordance with a control signal output from the first power supply control unit, and the second power supply unit. An inversion boosting type switching power supply unit for boosting a lower power supply voltage according to a control signal output from a control unit. 3. The power amplification device according to claim 2, wherein the step-up switching power supply unit is connected in series to a coil whose one end side is connected to a power supply and to the other end side of the coil, and from the power supply to the amplifier. A switch for supplying a current in the forward direction, a capacitor connected to the output side of the diode, a switch having one end connected to a connection point between the coil and the diode and the other end grounded, First
A switch for turning on / off according to a control signal from a power supply control unit, wherein the inverting boost type switching power supply unit is a switch for turning on / off according to a control signal from the second power supply control unit, A switch whose one end side is connected, a diode which is connected in series to the other end side of the switch and flows a forward current from the amplifier toward the power supply, and a capacitor connected to the amplifier side of the diode, A coil having one end connected to a connection point between the switch and the diode and the other end grounded. 4. A step-up switching power supply unit for boosting an output voltage of a power supply to generate a power supply voltage in response to a predetermined control signal, and amplifying input signals of opposite phases with the power supply voltage as an operating voltage. First and second amplifiers, an adder circuit for adding the output signals of the first and second amplifiers, a first input to which the output terminal of the switching power supply unit is connected, and an output terminal of the circuit via a reference voltage. And a second input connected thereto, comparing the signals applied to the first and second inputs and applying an output signal corresponding to the difference as the control signal to the switching power supply. And a power amplification device. 5. The power amplification device according to claim 4, wherein a pair of input terminals, a pair of differential output terminals connected to inputs of the first and second amplifiers, and a pair of differential output terminals are provided. A first differential amplifier having a common input terminal for determining a direct current level; a non-linear addition circuit for performing non-linear addition of output signals obtained at the pair of output terminals; and comparing an output signal of the linear addition circuit with a reference voltage. And a comparator circuit for applying an output signal corresponding to the difference to the common input terminal, and a power amplifier device. 6. The power amplification device according to claim 4, wherein the step-up switching power supply unit has a coil whose one end side is connected to a power supply and a series connection to the other end side of the coil. A diode that allows a forward current to flow from the power source toward the first and second amplifiers, a capacitor connected to the output side of the diode, and one end side connected to a connection point between the coil and the diode, A power amplifier having a switch whose other end is grounded and which is turned on / off in response to a control signal from the first power supply controller.