JPS5848508A - Power supply circuit for amplifier - Google Patents

Abstract

PURPOSE:To improve the efficiency of power conversion, by decreasing the conducting period of a transistor (TR) through the use of a terminal voltage of a capacitor in place of a part of a power supply. CONSTITUTION:TRs Q1, Q1' are provided between the collector functioning as a power supply receiving end of TRs Q1, Q1' constituting an output stage of a power amplifier. A series connection circuit of switching elements 3, 3', charging resistors R1, R1' and capacitors C1, C1' is provided between the power supply and the ground. While the elements 3, 3' are nonconductive, diodes D1, D1' supply a storage voltage of the capacitors C1, C1' to the collector. Further, level comparators 4, 4' are provided to compare each output voltage + or -Vb of the capacitors C1, C1' with the level of a voltage + or -Vc having the level of a circuit output V0 shifted and the elements 3, 3' are on/off-controlled with this output.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply circuit for an amplifier, and more particularly to a power supply circuit for supplying a power supply voltage to an output amplifying element constituting an output stage of a power amplifier.

In a class B push-pull amplifier, which is commonly used as a power amplifier, the power consumed by a pair of complementary transistors forming the output stage is instantaneously: PC=tc@vcE=ic@(voc- vo), and this amount of power is dissipated inside the amplifier, causing a decrease in efficiency. For example, the efficiency is theoretically 78.5% when the amplitude is at maximum, but it is further reduced when the signal is small.

In order to improve the power conversion efficiency, a so-called class E amplifier shown in FIG. 1 has been proposed. In such a class E amplifier, an output stage 1 for power amplifying an input signal IN applied via a voltage amplification stage 2 is composed of a complementary pair of transistors QI+Q;
As shown in the figure, the output signal υ. When is small, the power supply Eb
Let the voltmeter VD given by E and g via diodes D□ and D1' be the collector voltage va of the transistor Qs*Q+, and output signal υ. When the signal level is large, the transistor Q2 connected between the transistor Ql + Ql and the circuit power supply E, ,
*The structure is such that the loss of the transistor Ql w Ql is reduced by making C2 conductive and providing υa.

However, in such a configuration, transformer 9 and star Q
When s is conductive, the power loss in transistor Q2 is large, so that the loss reduction in transistors Q+ and C2) is small. Also, Eα, Eα′, Eh, Eb′
This method has the disadvantage of high cost because it requires equicomplex and isometric number sources.

An object of the present invention is to provide an amplifier power supply circuit that can improve power conversion efficiency by shortening the conduction period of transistors Q2s and Qt.

The power supply circuit for an amplifier according to the present invention includes a transistor provided between the power receiving end of the amplifier and the circuit power supply, and drives this transistor with a voltage corresponding to the output voltage of the amplifier. A control signal that is generated when power is supplied from the power storage means to the power receiving end of the amplifier, and when the absolute value of the difference between the voltage corresponding to the output voltage of the amplifier and the stored power output voltage of the power storage means becomes less than a predetermined value. The structure is such that power is supplied to the power storage means by the switching means which becomes conductive in response to the current.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a circuit diagram showing one embodiment of the present invention, in which parts equivalent to those in FIG. 1 are designated by the same symbols. Each transistor Q+'+Ql that constitutes the output stage of the power amplifier
The collector, which is the power receiving end of the power supply, and the circuit power supply Eαr E(Z
A transistor Q2*C2 is provided between these transistors Q! 's C2 uses the pace voltage of the transistors Q1e and Ql whose levels are shifted by Ef and Ef' as a pace input. Here transistor Q
The pace voltage at t + Ql is the amplifier output υ. Therefore, the transistor Qly C2 becomes conductive depending on the magnitude of the output signal level.

Circuit power supply Ea, E, 7. A series connection circuit of a switching element 3.3', a charging resistor R,, R,', and a storage capacitor CI + CI is provided between ' and ground.
Due to the conduction of switching elements 3 and 3', capacitor C,
, Cζ is charged in accordance with the time constants C1·a, , C;·huan. Also, capacitor c, 1*CI
A diode D, ,D,' as a unidirectional element is connected between each output terminal of and each collector of the transistor Q, ,Q;'.
are provided, and the switching elements 3, 3' are connected in polarity such that the voltage stored in the capacitors C, , C; is supplied to the collector terminal while the switching elements 3, 3' are non-conducting. Furthermore, capacitor c1. c, 'each storage output voltage ±υb and circuit output V. The level-shifted voltage of ±vCCv(1+ESs vQ
A level comparator 4.4' is provided for the comparison, and the switching element 3.3' is controlled on/off based on the comparison output.

The operation of the positive side circuit having such a configuration will be explained using the waveform diagram shown in FIG. 4. For the purpose of explanation, it is assumed that the forward voltage drop of the diode D1 and the pace-to-emitter voltage of the transistors Q+ +Q2 are ideally zero.

In addition, in the system of comparator 4 and switching element 3,
For example, switching element 30 may be turned on due to a slight time delay in switching from switching element 30 to off with respect to the control signal from comparator 4, or because comparator 4 has hysteresis characteristics with respect to the detected voltage.・The off operation shall be performed smoothly.

Hereinafter, the operating modes will differ depending on the magnitude relationship between the offset voltage generation voltage sources Es and Ef, so cases will be considered separately. Note that the circuit outputs υ are shown in FIGS. 4(α) to (d). An example of the waveform response of each part when is a burst wave is shown.

(1) When Ef > Es (R3 may be zero), Figure 4(a) shows the circuit output V. The frequency of is low, and the capacitor C is determined by the time constant of R8・C1 with respect to the rising slope of vo.
This shows a waveform when the charging curve of No. 1 has a steeper slope. In FIG. 4(α), the pace voltage and output V of transistor Q1 when there is no input signal.

is zero port, the transistor Q2 has a base voltage ν given by the voltage source Ef. The transistor Q is turned on (conducting) and a constant voltage va is applied to the collector of the transistor Q, while the output V is applied to the collector of the transistor Q. Since vc (vo + Es) = Es, since vc (vo + Es) = Es, vb > Es, and the comparator 4 turns off the switching element 3 (non-conducting). here va ) ZJh
Since the diode D1 is off, the voltage vh maintains its state without a discharge path.

At time T, the output V. A positive half-cycle signal appears and rises, and when vc≧vb, the output of comparator 4 is inverted and switching element 3 is instantly turned on, so voltage vh of capacitor C1 rises with time constant R8・CI. do. When vc<vb, the comparator 4 is inverted and the switching element 3 is turned off, so the capacitor C
Charging of I is stopped again.The above operation is repeated one after another until time T arrives, and after vE<vh and □, transistor Q2 is turned off. This turns on diode D, so capacitor C1 outputs V. Voltage va# is applied to the collector of transistor Q1 while continuing to discharge until becomes zero.
Continue to supply vb.

Furthermore, the next positive half-cycle signal appears, the pace input of transistor Q increases, and at time T2 when vE>vb, transistor Q2 is turned on again, and the voltage va according to the magnitude of the output signal level increases. will be applied to the collector of transistor Q. When vc≧vb, the switching element 3 is turned on and the capacitor C1
Charging is started, and the above-described operation is repeated thereafter.

FIG. 4(h) shows the circuit output V. The waveform when the frequency of is high is shown, and the slope of the charging curve of capacitor C1 is V. Since the rising slope of +7. When the voltage starts to fall, vc<vh, and the switching element 3 turns off.

As can be seen from the figure, the output υ. After the end of the positive half circle, vh is held at a fairly high voltage and the next arriving output V. In the positive half cycle of Zlc≧
The timing at which the voltage becomes vh is the output V. The timing at which the switching element 3 is turned on (ν0≧vb) is delayed even further after the third wave, and the transition to a steady state occurs later than during the first wave.

(2) When Bf<Bs FIG. 4(C) shows the circuit output V. The waveform is shown when the frequency of is low and the slope of the charging curve of capacitor C1 is steeper than the rising slope of ν0. In such a case, since vh>vE, the transistor Q2 is always in an off state, and the output voltage vh of the capacitor C8 is supplied as the collector voltage of the transistor Q via the diode D1. Charging and discharging of capacitor C1 is shown in Figure 4 (α)
As in the case of , this is done by turning on and off the switching element 30 based on the level comparison between vb and vc.

Figure 4(d) shows the circuit output υ. The waveform when the frequency of is high is shown, and as in the case of FIG. 4(b), the slope of the charging curve of capacitor C7 is V. Since the rising slope of is steeper, the on-period of the switching element 30 becomes longer, and when vE>vb during the on-period, the transistor Q2 turns on and the voltage υ4 according to the magnitude of the output signal level increases. It will be supplied to the collector of transistor Q.

Although each of the above operations has been explained only for the positive half cycle of the signal, it is clear that the same operation is performed for the negative half cycle. Further, the present invention is not limited to the above embodiments, and the output V inside the amplifier.

Since a signal similar to (for example, the pace voltage of transistor Q+ + Ql) is generated, this similar signal may be appropriately used as the manual input of the level converter noscillator 401 (also, if the pace of transistor Q2 + Q2 is set to the voltage It is also possible to connect, for example, to the circuit output terminal via the sources El and F4'.Furthermore, although a class B amplifier has been described,
The same can be applied to class A and class AB amplifiers.

In such a circuit, the power source is Ba (EJ) only,
Capacitor C obtained by turning on/off switching element 3 (3') instead of conventional power supply Eb (Eh')
By using the terminal voltage υb (-vh') of 1 (CO), the on period of transistor Q2 (QJ) is shortened compared to the conventional one, so the power consumption in transistor Q2 (QJ) is reduced, and the transistor Q1 (QO9Q2
(Q2)) - Power loss in the barrel is reduced and power conversion efficiency is improved.

FIG. 5 is a circuit diagram showing a specific example in which the circuit of FIG. The circuit parts are designated with the symbols L and R. In the figure, the circuit parts for generating the output voltage vb which can vary to some extent depending on the output signal level are designated L,
It is also used as the R channel, and its control is by diode bridge circuit 5.

This is done by obtaining the MIX component of the R output.

As the switching elements 3, 3', transistors Q, hQ, , Q; and Q:, which have an inverted Darlington configuration, are used to increase the current amplification factor. Further, as a charging means for the capacitors C, , C,', choke coils L, , L; are used to eliminate power loss in the resistors R, , TL, ' in FIG.

Note that the diode D2. The tuft is a switching element 3゜3'
A freewheel diode for commutating the electromagnetic energy accumulated in the choke coils L, , L; when turned off. Level comparators 4, 4' are transistors Q, ,Q
, and a current source 6. Transistor Qs-(L and current source 6
It has a differential amplifier configuration including feedback resistors TL*, R
; Niyo? ) The comparator level has a hysteresis characteristic to smooth the on/off operation of the switching element 3.3'.

As detailed above (according to the present invention, the transistor Q2
v Since the ON period of Q2 is short, transistor Q2
+ Power consumption in Q2 is reduced and transistor Qt+Q
Otsu Q2, Q2 Since the total power loss can be reduced and the power conversion efficiency can be improved, there is an advantage that the heat sink can be made smaller or a transistor with a lower maximum rated power can be used. In particular, it is possible to easily achieve miniaturization and increase in output of audio power amplifiers and the like. In addition, the power supply voltage is determined by turning on and off switching elements.

Since there is no sudden rise or fall of 9g, there are few harmonic components included in the power supply voltage waveform, so the transistor Ql e
υ on the output signal due to the influence of Coh and hoe of Ql.

Another advantage is that there are fewer changes.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a diagram showing changes in supply voltage with respect to an output signal in the circuit of FIG. 1, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. , FIG. 4 is a waveform diagram for explaining the operation of the circuit of FIG. 3, and FIG. 5 is a circuit diagram showing a specific example in which the circuit of FIG. 3 is applied to a stereo power amplifier. Explanation of symbols of main parts 3.3' ... Switching element 4.4' ... Lebel comparator Ql + Ql ... Amplification transistor c,, c
ζ ...Capacitor Ll + Ll ...Choke coil applicant Pioneer Co., Ltd. agent Patent attorney Motohiko Fujimura

Claims (1)

[Claims] a transistor provided between a power receiving end of the amplifier and a circuit power supply and having a base input as a voltage corresponding to the output voltage of the amplifier; a power storage means; and a power storage means that is electrically connected by a predetermined control signal to supply the circuit power supply voltage to the power storage means. a unidirectional element that applies a storage output voltage of the power storage means to the power receiving end during a non-conducting period of the switching means; and control signal generating means for generating the predetermined control signal when the absolute value of the difference between the voltage and the voltage becomes equal to or less than a predetermined value.