JPH10242768A - Power amplifier and electronic device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the power amplifier with a small power loss and the electronic device using it. SOLUTION: A down-converter is formed by a FET 21, a diode 22, a coil 23 and a capacitor 24. A comparator 25 compares a voltage Va at a power supply terminal 11a of an amplifier section 11 with a comparison voltage Vsz1 to apply A discrimination signal CPA to a drive signal generating section 51. A reference signal generating section 53 applies a reference signal CLK to the signal generating section 51. The signal generating section 51 generates a drive signal SWA based on the signals CLK, CPA to drive the FET 21. When an output signal SOUT is small, a voltage (power supply + VPL) is fed to an amplifier section 11 via a diode 26. When an output signal SOUT is large, a voltage (power supply + VPH) is fed to the amplifier section 11 while being reduced by the down-converter depending on the signal SOUT. The negative side configured similarly to above. Thus, the power loss of the amplifier section 11 is reduced. Reception interference of the down-converter due to noise is relieved by varying a frequency of the reference signal CLK depending on the channel selection of a tuner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier and an electronic device using the same. More specifically, a comparison signal whose voltage level is varied based on an output signal from the amplifying means is compared with a power supply voltage of the amplifying means to generate a determination signal. When the comparison voltage exceeds the power supply voltage, the determination signal is generated. A driving signal is generated based on the switching reference signal from the switching reference signal generating means to drive the switching element, and the power supply voltage is varied according to the signal level of the output signal output from the amplifying means. In an electronic device, a switching reference signal is generated by a switching reference signal generating means based on a reference frequency signal used in a tuner, and the frequency of the switching reference signal is controlled to control the basic noise generated by the switching operation of the switching element. The wave component and the harmonic component are set to a frequency of a signal selected by the tuner or a frequency different from a signal obtained by the tuner.

[0002]

2. Description of the Related Art In recent years, audio devices such as mini-components and CD radio-cassettes have been reduced in size and tended to have higher outputs. A power transformer having a large capacity, a power IC, a radiator, or the like may be used. However, using a large-capacity transformer causes an increase in cost and also increases power loss because a high power supply voltage is applied to the power amplifier and the power supply transformer.

For this reason, it is conceivable to pay attention to the output voltage of the power amplifier and switch to using a low power supply voltage when the output voltage is low and using a high power supply voltage when the output voltage is high. For example, as shown in FIG. 5, when the voltage of the output signal SOUT is lower than the predetermined voltage + Vx, a low power supply voltage + VPL (about 10 to 20 volts) is selected as the operating power supply, and when the output signal SOUT is higher than the voltage + Vx, the high power supply voltage + VPH (40 (About 50 volts) is selected as the operating power supply. Similarly, not only the positive side but also the negative side are switched in the negative direction between the high voltage -VPH and the low voltage -VPL according to the voltage of the output signal SOUT.

If the power supply voltage can be changed in accordance with the output voltage in this manner, a high power supply voltage is not used when the signal level of the output signal is low, so that the capacity of the transformer is suppressed from being increased, and heat generation inside the housing is also suppressed. Can be suppressed. As a result, the cost of the apparatus can be reduced.

[0005]

By the way, even when the power supply voltage is switched according to the signal level of the output signal as described above, the voltage of the output signal is selected when the high power supply voltage ± VPH is selected. Is slightly higher than the voltage Vx, the power loss cannot be reduced sufficiently.

Accordingly, the present invention provides a power amplifier having a small power loss and an electronic device using the same.

[0007]

A power amplifier according to the present invention includes an amplifying means for amplifying an input signal and outputting the amplified signal, and a voltage level varying according to the signal level of the output signal output from the amplifying means. Voltage comparison means for comparing the voltage with the power supply voltage supplied to the amplification means to generate a determination signal,
A switching reference signal generating means for generating a switching reference signal having a predetermined frequency, and a drive signal generating means for generating a drive signal based on the determination signal generated by the voltage comparing means and the switching reference signal generated by the switching reference signal generating means. Means, and a power supply voltage control means for driving a switching element based on the drive signal generated by the drive signal generation means and controlling a power supply voltage supplied to the amplification means, and a power supply voltage supplied to the amplification means Is controlled in accordance with the signal level of the output signal of the amplifying means.

Further, the electronic apparatus supplies the tuner, amplifying means for amplifying and outputting the input signal, a comparison voltage whose voltage level is varied based on the signal level of the output signal output from the amplifying means, and an amplifying means. Voltage comparing means for generating a determination signal by comparing the power supply voltage to be supplied, a switching reference signal generating means for generating a switching reference signal of a predetermined frequency, a determination signal generated by the voltage comparing means, and a switching reference signal generation. A driving signal generating means for generating a driving signal based on the switching reference signal generated by the means, and a switching element driven based on the driving signal generated by the driving signal generating means, and a power supply voltage supplied to the amplifying means. Power supply voltage control means for controlling the power supply voltage supplied to the amplification means in accordance with the signal level of the output signal of the amplification means. Rutotomoni, the switching reference signal generating means is for generating a switching reference signal based on the reference frequency signal used by the tuner.

In the present invention, the comparison voltage whose voltage level is varied based on the output signal from the amplifying means and the power supply voltage of the amplifying means are compared by the voltage comparing means to generate a determination signal. A drive signal is generated by the drive signal generation means based on the discrimination signal, and the power supply voltage control means configured using, for example, a down converter is driven by the drive signal, so that the power supply voltage and the comparison voltage become equal. Power supply voltage is controlled as described above. Further, the fundamental component and the harmonic component of the noise generated when the power supply voltage control means is switched by the drive signal are set to have a different frequency band from the frequency band of the signal selected by the tuner or the signal obtained by the tuner. , The frequency of the switching reference signal is controlled.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an embodiment of a power amplifier.

In FIG. 1, a low-frequency signal SIN is supplied to a signal input terminal 11s of an amplifying unit 11, which is an amplifying unit. The low power supply voltage + VPL (10 to 10
(About 20 V) is supplied to the positive power supply input terminal 11 a via the diode 26.

The second power supply voltage, that is, a high power supply voltage + VPH
(About 40 to 50 V) is supplied to the drain of a field effect transistor (hereinafter referred to as “FET”) 21 which is a switching element. The source of FET 21 is diode 2
2 and one terminal of the choke coil 23. The anode of the diode 22 is grounded, and the other terminal of the choke coil 23 is connected to a capacitor 24.
And the positive power supply input terminal 11 a of the amplifier 11. The other terminal of the capacitor 24 is grounded. Further, a drive signal SWA is supplied to a gate of the FET 21 from a drive signal generation unit 51 described later.

The positive power supply input terminal 11a of the amplifier 11 is connected to a non-inverting input terminal of a comparator 25, which is a voltage comparison means.

A negative power supply voltage -VPL (about -10 to -20 V), which is a first power supply voltage, is connected to a diode 36.
To the negative power supply input terminal 11b.

A power supply voltage -VPH (about -40 to -50 V), which is a second power supply voltage and is negatively high, is supplied to the drain of the FET 31 which is a switching element. FET3
One source is connected to the anode of the diode 32 and one terminal of the choke coil 33. The cathode of the diode 32 is grounded, and the other terminal of the choke coil 33 is connected to one terminal of the capacitor 34 and the negative power supply input terminal 11 b of the amplifier 11. The other terminal of the capacitor 34 is grounded. The gate of the FET 21 has a drive signal SWB from a drive signal generation unit 52 to be described later.
Is supplied.

The negative power supply input terminal 11b of the amplifier 11 is connected to a non-inverting input terminal of a comparator 35 which is a voltage comparison means.

The power supply voltage control means includes an FET 21,
31, choke coils 23, 33, diodes 22, 3
2. Ringing choke type down converter composed of capacitors 24 and 34, and diodes 26 and 36.

In the amplifying unit 11, the input low frequency signal S
IN is amplified to produce an output signal SOUT. The output signal SOUT is supplied from the signal output terminal 11t to the speaker 41, and the speaker 41 outputs a reproduced sound.

The signal output terminal 11t has an anode of the Zener diode 27 and a Zener diode 37.
Are connected. This Zener diode 27
Is connected to the inverting input terminal of the comparator 25, and the anode of the zener diode 37 is connected to the inverting input terminal of the comparator 35. For this reason,
The inverting input terminal of the comparator 25 has an output signal SOUT
, And a zener voltage Vz27 of the zener diode 27 is added to apply a comparison voltage Vsz1.

In the comparator 25, the comparison voltage Vsz
1 and the positive power supply input terminal 11a applied to the non-inverting input terminal
Is compared with the power supply voltage Va to indicate a comparison result.
The PA is generated and supplied to the drive signal generation unit 51 configured using, for example, a D-flip-flop. For example, when the comparison voltage Vsz1 is smaller than the power supply voltage Va, the discrimination signal CPA is set to the high level “H”. When the comparison voltage Vsz1 is larger than the voltage Va, the discrimination signal CPA is set.
The signal level of A is set to low level “L”.

Similarly, in the comparator 35, a determination signal CPB is generated based on the comparison voltage Vsz2 obtained by adding the signal level of the output signal SOUT and the zener voltage Vz37 of the zener diode 37 and the power supply voltage Vb of the negative power supply input terminal 11b. And supplied to the drive signal generator 52.

The drive signal generators 51 and 52 receive the switching reference signal CL from the switching reference signal generator 53.
K is supplied.

Next, the operation will be described with reference to FIG. FIG. 2A shows the power supply voltage Va of the positive power supply input terminal 11a and the output signal SOUT.

Here, the comparator 25 supplies the power supply voltage V
a, the signal level of the output signal SOUT and the Zener voltage Vz27
Is added to the comparison voltage Vsz1 (shown by a broken line in FIG. 2A).

In the comparator 25, the power supply voltage Va and the comparison voltage Vsz1 are compared, and a determination signal CPA shown in FIG.
Is output. For example, since the voltage level of the power supply voltage Va is large until time t1, the signal level of the determination signal CPA is set to the high level "H". When the voltage of the comparison voltage Vsz1 becomes higher than the power supply voltage Va at the time point t1, the signal level of the determination signal CPA is set to the low level “L”.

FIG. 2C shows a switching reference signal generator 53.
3 shows the switching reference signal CLK supplied from the control signals to the drive signal generators 51 and 52. The drive signal generator 51,
Reference numeral 52 includes, for example, a D-flip-flop, and generates the drive signal SWA based on the signal level of the determination signal CPA at the time when the signal level of the switching reference signal CLK rises.

For example, at time t0, the signal level of the discrimination signal CPA is at the high level "H", so that the signal level of the drive signal SWA shown in FIG. 2D is at the high level "H". At time t2, the switching reference signal CL
When the signal level of K rises, the signal level of the determination signal CPA is set to the low level “L”, so that the signal level of the drive signal SWA is set to the low level “L”.

Here, when the signal level of the drive signal SWA is set to the low level "L", the FET 21 is turned on and the voltage level of the power supply voltage Va is increased.

Thereafter, when the power supply voltage Va becomes higher than the comparison voltage Vsz1 at time t3, the signal level of the discrimination signal CPA is set to the high level "H" and the signal level of the switching reference signal CLK at time t4. Is high when the signal level of the determination signal CPA is high.
Therefore, the signal level of the drive signal SWA is set to the high level “H”. For this reason, the FET 21 is turned off, and the speaker 41 is
Is driven, the power supply voltage Va is reduced.

When the power supply voltage Va becomes lower than the comparison voltage Vsz1 at time t5, the signal level of the discrimination signal CPA is set to the low level "L", and the signal level of the switching reference signal CLK rises at time t6. Synchronously, the signal level of the drive signal SWA is set to the low level “L”. Therefore, the FET 21 is turned on, and the power supply voltage Va is increased.

Similarly, the switching reference signal C
A drive signal SWA is generated according to the signal level of the discrimination signal CPA at the time of the rise of the signal level of LK, and the FET 21 is driven by the drive signal SWA, so that the power supply voltage Va is varied according to the signal level of the output signal SOUT. You.
Therefore, power loss can be reduced.
Since the signal level of the drive signal SWA is switched in synchronization with the rise of the signal level of the switching reference signal CLK, the cycle of the drive signal SWA is set to an integral multiple of the switching reference signal CLK. Although not shown, the same operation is performed on the negative power supply side, and the output signal SOUT
, The power supply voltage Vb is controlled.

As described above, when the signal level of the output signal SOUT is lower than the predetermined level, the low power supply voltage ± V
When the PL is supplied to the amplifier 11 and the signal level of the output signal SOUT becomes higher than a predetermined level, the power supply voltage ±
VPH is reduced according to the output signal SOUT by a ringing choke type downconverter constituting the power supply voltage control means. For this reason, power loss in the amplifier 11 can be reduced.

When the signal level of the output signal SOUT is lower than the signal level, the switching operation is not performed, so that generation of noise caused by the switching operation can be prevented, and the signal level of the output signal SOUT is higher than a predetermined level. And the switching element F
Even when the ETs 21 and 31 are switched, the frequencies of the fundamental component and the harmonic component of the noise generated by the switching operation are not constant but are dispersed, so that the frequency of the fundamental component and the harmonic component of the noise can be reduced in a short time. The noise amount can be reduced to reduce the amount of noise per unit time at a predetermined frequency, and the effect of the generated noise can be reduced to a level that does not cause any practical problem.

By the way, such a power amplifier can also be used for electronic equipment having a tuner. next,
A case where this power amplifier is used in an electronic device having a tuner will be described. In this case, the switching reference signal CLK is generated using the reference frequency signal used in the tuner.

FIG. 3 is a diagram showing a configuration of a switching reference signal generating section for generating a switching reference signal CLK using a reference frequency signal used in a tuner. In FIG. 3, a signal RS received by an antenna 60 is supplied to a signal processing unit 61. The signal processing unit 61 selectively amplifies the signal of the broadcast radio wave to be selected based on the tuning voltage Vc supplied from the phase comparison unit 64 described later. The signal processing section 61 has a voltage controlled oscillation section, and generates a local oscillation signal FO based on the tuning voltage Vc. The signal of the broadcast wave selected on the basis of the generated local oscillation signal F0 is converted into a single frequency signal, and the frequency signal is subjected to band limitation and detection to perform the audio signal SA.
Is generated. The audio signal SA is supplied as a low-frequency signal SIN to the signal input terminal 11s of the amplifier 11, and the audio is output from the speaker 41. Also, the local oscillation signal F0
Is supplied to the frequency divider 62.

The frequency dividing section 62 is supplied with a control signal TC for selecting a desired broadcast wave from a control section 63 which is a frequency control means constituted by using a microcomputer or the like. , The local oscillation signal F0 is frequency-divided to generate a frequency-divided signal FD. This divided signal F
D is supplied to the phase comparison unit 64.

The phase comparison section 64 includes a reference frequency generation section 6
5, the reference frequency signal MCK and the frequency-divided signal FD are compared in phase, and a voltage signal indicating a phase difference is supplied to the signal processing unit 61 as a tuning voltage Vc. .

The frequency dividing control signal UC is supplied from the control unit 63 to the frequency dividing unit 66. In the frequency divider 66, the oscillation signal SCK supplied from the voltage control oscillator 68, which will be described later, is frequency-divided at a frequency division ratio based on the frequency division control signal UC to generate a frequency divided signal GD. This frequency-divided signal GD is supplied to the phase comparing section 67. In the frequency divider 66, the oscillation signal SCK is frequency-divided by a frequency division ratio based on the frequency division control signal UC to generate a switching reference signal CLK, which is supplied to the drive signal generators 51 and 52.

The phase comparator 67 includes a reference frequency generator 6
The reference frequency signal MCK generated in step 5 is supplied. The reference frequency signal MCK and the frequency-divided signal GD are compared in phase, and an error voltage signal ER indicating a phase error is supplied to the voltage control oscillator 68. In the voltage controlled oscillator 68, the frequency of the oscillation signal SCK generated by the voltage controlled oscillator 68 is controlled based on the error voltage signal ER.

As described above, since the reference frequency signal MCK and the frequency-divided signal GD are synchronized, the switching reference signal CLK is also synchronized with the reference frequency signal MCK.

Here, in the control section 63, the frequency division control signal U
Drive signals SWA and SWB generated based on a switching reference signal CLK whose frequency is set at C,
The frequency of the fundamental wave component of the noise generated when the FETs 21 and 31 are switched and the harmonic component thereof are generated by the reception band of the broadcast radio wave selected based on the control signal TC and the signal processing unit 61. The frequency division control signal UC is generated so as not to coincide with the frequency of the intermediate frequency signal.

Therefore, even when the signal level of the output signal of the amplifying unit 11 is increased while the broadcast wave is being received by the tuner and the power supply voltage is varied according to the output signal, the reception disturbance due to noise is reduced. can do.

In the above-described electronic apparatus, the oscillation reference signal CLK is generated by dividing the oscillation signal SCK generated by the voltage control oscillator 68 by the frequency divider 66. The switching reference signal CLK may be generated by using the reference frequency signal MCK generated in step (1).

FIG. 4 shows a configuration for generating the switching reference signal CLK using the reference frequency signal MCK. In FIG. 4, portions corresponding to those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The reference frequency signal MCK generated by the reference frequency generating section 65 is supplied to the phase comparing section 64 and also to the frequency dividing section 71. The frequency dividing section 71 is supplied with a frequency dividing control signal WC from a control section 70 which is a frequency control means. Based on the frequency dividing control signal WC, the reference frequency signal MCK is frequency-divided and a switching reference signal CL is outputted.
K is generated. The control unit 70 controls the frequency division control so that the frequency of the fundamental wave component of the noise or its harmonic component does not coincide with the reception band of the selected broadcast radio wave or the frequency of the intermediate frequency signal, similarly to the control unit 63. A signal WC is generated. For this reason, it is possible to reduce a reception failure due to noise, and to generate the switching reference signal CLK with a simple configuration and at low cost.

As described above, according to the above-described embodiment,
The power loss of the power amplifier can be reduced, and the power amplifier can be used, for example, in an electronic device having a tuner.

[0047]

According to the present invention, the drive signal is generated by the drive signal generation means based on the determination signal from the voltage comparison means and the power supply voltage control means is driven, so that the power supply voltage supplied to the amplification means is provided. Is varied according to the output signal output from the amplifying means, so that power loss in the amplifying means can be reduced.

The fundamental wave component and the harmonic component of the noise generated by the power supply voltage control means are controlled by the frequency control means so as to have a frequency band different from the frequency band of the signal selected by the tuner or the signal obtained by the tuner. Therefore, even if the power supply voltage supplied to the amplifying unit is varied according to the output signal, it is possible to reduce reception disturbance due to noise.

Further, when the signal level of the output signal is higher than a predetermined level, the power supply voltage is controlled by the power supply voltage control means. it can.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an embodiment of a power amplifier.

FIG. 2 is a diagram showing an operation on a positive side of a power amplifier.

FIG. 3 is a diagram illustrating a configuration of a switching reference signal generation unit.

FIG. 4 is a diagram illustrating another configuration of the switching reference signal generation unit.

FIG. 5 is a diagram showing a power supply switching operation.

[Explanation of symbols]

 Reference Signs List 11 amplifying section 21, 31 field effect transistor (FET) 25, 35 comparator 51, 52 drive signal generating section 53 switching reference signal generating section 62, 66, 71 frequency dividing section 63, 70 control section 64, 67 phase comparing section 65 reference Frequency generator 68 Voltage controlled oscillator

Claims (6)

[Claims] Amplifying means for amplifying and outputting an input signal; a comparison voltage whose voltage level is varied according to a signal level of an output signal outputted from the amplifying means; and a power supply voltage supplied to the amplifying means. Voltage comparison means for generating a determination signal by comparing the switching reference signal with a predetermined frequency, a switching reference signal generation means for generating a switching reference signal of a predetermined frequency, and a determination signal generated by the voltage comparison means and the switching reference signal generation means. A drive signal generation unit that generates a drive signal based on the generated switching reference signal; and a drive element that drives a switching element based on the drive signal generated by the drive signal generation unit, and supplies a power supply voltage supplied to the amplification unit. Power supply voltage control means for controlling the power supply voltage supplied to the amplification means in accordance with the signal level of the output signal of the amplification means. Power amplifier, characterized by. 2. The power supply voltage control means includes a first power supply voltage and a second power supply voltage having a higher voltage level than the first power supply voltage.
The power supply voltage control means drives a switching element based on the drive signal generated by the drive signal generation means to vary the voltage level of the second power supply voltage. If the second power supply voltage whose voltage level has been changed is higher than the voltage level of the first power supply voltage, the second power supply voltage whose voltage level has been changed is replaced with the first power supply voltage. The power amplifier according to claim 1, wherein the power is supplied to the amplification means. 3. A tuner, amplifying means for amplifying and outputting an input signal, a comparison voltage whose voltage level is varied based on a signal level of an output signal output from the amplifying means, and a comparison voltage supplied to the amplifying means. Voltage comparing means for generating a determination signal by comparing with a power supply voltage, a switching reference signal generating means for generating a switching reference signal of a predetermined frequency, a determination signal generated by the voltage comparing means, and the switching reference signal A drive signal generation unit that generates a drive signal based on the switching reference signal generated by the generation unit; and a switching element that is driven based on the drive signal generated by the drive signal generation unit and is supplied to the amplification unit. And a power supply voltage control means for controlling a power supply voltage. The power supply voltage supplied to the amplification means is controlled by a signal level of an output signal of the amplification means. An electronic apparatus, wherein the switching reference signal generating means generates a switching reference signal based on a reference frequency signal used in the tuner, while controlling according to a bell. 4. The switching reference signal generating means has an oscillator and a frequency divider. The oscillator generates an oscillation signal synchronized with a reference frequency signal used in the tuner. 4. The electronic device according to claim 3, wherein a frequency of the oscillation signal generated by the oscillation unit is divided to generate a switching reference signal. 5. The switching reference signal generating means according to claim 3, wherein said switching reference signal generating means has a frequency divider, and said frequency divider divides said reference frequency signal to generate a switching reference signal. Electronics. 6. A frequency control means for controlling a frequency of a switching reference signal generated by said switching reference signal generation means, wherein said frequency control means comprises a fundamental wave of noise generated by driving said switching element. 4. The electronic device according to claim 3, wherein the frequency of the switching reference signal is controlled so that the frequency of the component and the harmonic component is different from the frequency of the signal selected by the tuner or the frequency of the signal obtained by the tuner. machine.