JPS5887903A - Direct current power supply circuit driving power amplyfying circuit - Google Patents

Abstract

PURPOSE:To improve the utilizing efficiency of power supply, by increasing the supply voltage to a circuit unit, when the envelope voltage of an input or output signal exceeds a prescribed value. CONSTITUTION:Power is applied to a circuit integrated circuit for general- pupose amplifier from ordinary terminals 27 and 28. A variable voltage in response to an amplification signal level is applied to power inputs 37, 38 of the output stage from PWM amplifying circuits 4, 4' via diodes 6, 6'. If a signal inputted to a terminal 1 exceeds an output voltage of the circuits 4, 4', switching transistors 8, 8' are conductive and the power supply path to output stage transistors 5, 5' is switched to a constant voltage power supply path applied to the terminals 27, 28. The efficiency of power supply of general-purpose amplifier can be improved by using externally mounted components.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an auxiliary power supply circuit for driving an audio power amplification circuit, and in particular a DC power supply circuit that can reduce the loss of the circuit and improve the overall power conversion efficiency. The present invention is intended to provide a suitable circuit arrangement for application to a power amplifier circuit constructed of circuit units such as a power supply circuit or the like.

Conventionally, class A amplification circuits, class B amplification circuits, and the like have been known as audio amplification circuits.

Most amplifiers in practical use use one of these methods. Among these, those with an output of several tens to several 1 oor are called power amplifiers, and class A and class B are used at the same time. Class B is often adopted from the viewpoint of The voltage is (+, Vc) - the signal amplitude is (
V.

), these mountains (2) are respectively shown by the following equations.
As is clear from the equation (2), the maximum efficiency is obtained when the signal amplitude (Vo) is equal to the power supply voltage, that is, at the maximum output, and in the case of class A, 7jACme
t3:)-50%, ηB (rrLetx) in class B
= 78.5%. From the point of view of efficiency, path width modulation (PWM PtLlse Width Modulation)
A so-called class D multiplier circuit of the tion) type is well known.

This switches and supplies power to the load f2 at high speed, and the duty of this switching (darkness when ON and Q F
By making the ratio between F and M directly proportional to the signal, the average power applied to the load l2 is controlled. Theoretically, the force control element has no indication of conduction or interruption, so it is known that there is no heat generation μm in this part, and there is no loss, resulting in extremely high efficiency.However, on the other hand, it is known that the switching pulse waveform is distorted. There are many harmonic distortions in the annular shape, and there are few examples of it being put to practical use.

(1) Figure 1 shows examples of the theoretical efficiency curves of class A and BIJk amplifier circuits shown by formula 121, and the measured efficiency curves of class D amplifiers.

Now, the maximum output of such class A and class B amplifiers is '4
It is determined by the source voltage (CVD) and load resistance, but of course it is not always used at maximum output.

It is known that the average power energy of a music signal is 1/8 to 1/1D of the maximum power (peak value).

Therefore, as shown from equation (1) or (2), the actual efficiency of these amplifiers is extremely low, for example, R-1
Capable of outputting up to 10oIV to a 3Ω speaker #
In a 4-width amplifier, the efficiency when outputting IQF is - From equation (2) for a class B amplifier, if the output power is (Pop) and the human power is (Pi), then the loss power (Pi-Po) In other words, this results in a loss of 30F for the output C of the IQF, which is a waste.This is because in order to provide maximum power (2 Since the amplitude of the output signal is small, this difference becomes a loss as a voltage drop in the output stage element.If the power supply voltage is always maintained at the peak of the output signal amplitude, the efficiency will decrease. is 78.5, and the power loss is 10×(., 78
．． -1) -2.7F is sufficient.

Taking these points into consideration, the originator of a patent application should first file a patent application in
No. 5-67276 was filed. 1, the power supply voltage is controlled according to the pressure signal amplitude (2) in accordance with the output of the amplifier, and the voltage drop in the output stage element is kept to the necessary minimum, reducing the loss generated in this part, and reducing the overall amplifier output. We proposed an amplifier that improves efficiency.

To explain in more detail, the conduction of the power amplifier section including the output stage of the amplifier is made into a variable voltage source, and the envelope change of the output signal amplitude,
That is, it is controlled according to the signal envelope. Further, the control signal of the variable voltage power supply is obtained by rectifying the output signal.

Of the time constants that determine the response binary of this rectifier circuit, the rise time constant that determines the rise time (attack time) is of course sufficiently small, and the rising distance of the variable voltage source 4 in response to this is as early as possible.

In addition, when it is impossible to follow the sudden rise in the output signal,
Temporarily switch to a separately provided constant voltage power supply with a sufficiently high voltage. Here, the @distributed variable voltage power supply must maintain high efficiency over the entire voltage control range, and therefore, as such an acid m device, it is especially important to switch the pulse width modulation method! This is achieved by using a power supply (hereinafter abbreviated as PWM power supply). The specific contents of this type of amplifier will be explained in detail below based on FIG.

Figure 2 is a block diagram explaining the principle of this type of amplifier. The signal is manually input to the PWM amplification circuit (4) through an envelope voltage generation circuit (3) consisting of a rectifier circuit for rectifying the signal. The output of the PWM amplifier circuit (4) is connected via a diode (6) as shown in the figure as a variable DC conductor of a power amplifier circuit (5) cascaded to the voltage amplifier circuit (2), while a separately provided constant voltage The DC power supply circuit (7) is transistor 1
Power is supplied to the power amplifier circuit (5) via 81,
The transistor +81 is a voltage amplification circuit (2) as shown in the figure.
Since it is an emitter follower type in which the 7th pace is connected via the level shift circuit (signal level conversion circuit) (9) on the side, the pace potential is the emitter potential, that is, the PWM amplifier circuit (4).
), it is reverse biased and in a cutoff state. In this case, the power for the power amplifier circuit +51 is supplied by the PIVM circuit +41. When the base position of the 111th transistor (8), which adds a certain value to the output signal of the voltage amplification circuit (2), exceeds the output of the PWM circuit (4), the transistor (8) becomes active as an emitter-follower connection. It enters the state, receives power from the constant voltage DC power supply (7), and energizes the power amplifier circuit +51 to approximately the pace compensation level. At this time, the diode 6) becomes like an inverted 7-large IA, and the current increases. Prevents backflow to the PiVMm path A4) side. Note that qO is an output terminal. In addition, the human power of the rectifier circuit (3) may be supplied from the voltage amplifier circuit (2) and the output terminal rm of the f output terminal.If configured as described above, the 'i4i willow voltage will change to the amplitude of the output signal of the amplifier. Since it is controlled, the voltage drop at the output stage element is kept to the necessary minimum f2, and the loss occurring in this part is minimized.
Lively 11i! ! A specific example of such a power amplifier circuit that can be used is shown in FIG.

That is, the signal input to the input terminal (1) is the transistor + 141 Qfl - resistor (1 Δ port 3, constant current source 0
After being amplified by a differential amplifier configured by 0.

Level shift element such as Zener diode +211 B
A signal level conversion circuit consisting of 8 transistors and 09 resistors constitutes an m-width stage.
The output stage transistor f5M51θ) is connected to both ends of the level shift element (2), and after the power #11 is drained from the transistor C2, the output voltage is outputted to the output terminal Qfj. Here, the output stage transistor +51151 is supplied with a 100-current rotary power supply that amplifies the output signal of the rectifier circuit +31131 that rectifies the output signal from the output terminal QO, and the crosspiece power supply voltage varies depending on the amplified signal level. The pace of the switching transistor (8) that is changing is connected to the positive terminal of the level shift element (8f), and the pace of the switching transistor (8f) is connected to the negative terminal 1 of the level shift element (to), respectively, to the diode (to) ( When the output signal of the transistor (a) exceeds the output potential of the PWM amplifier circuit +41 or +41, switching occurs. Since the transistors +81 +81 are conductive, the power supply path to the output stage transistors +51 +51 is switched to the constant voltage power supply supplied to the terminal @(5).The resistor (to) is a feedback resistor or a resistor. vcanaη is for connecting the conductor of transistor a9 to the circuit ground.

In the specific example explained above, it is easy to realize a power amplifier circuit because it is composed of individual parts. However, the number of parts is larger than that of a normal power amplifier, For example, if a general-purpose integrated circuit is used for a circuit component including a voltage amplification circuit and an output stage transistor, it will be difficult to put it into practical use for the following reasons. In other words, the general-purpose power amplifier integrated circuit generally has the circuit configuration shown within the dashed line in Figure 4, and the literati output terminals are also shown in terminals ~ (41). Since σ) is normal, −+iiJ, Figure 6 (2-t
This means that it is difficult to obtain a signal that drives the transistor (8) or 18).

In view of this point, the present invention provides a circuit configuration that can be applied to a circuit unit (2) such as a power amplifier integrated circuit for σL, and seven embodiments are shown in FIG. That is, as stated in AiJ, the area within the straight two broken lines is a general-purpose integrated circuit for power amplifiers, and the input/output terminals are terminals 0 and 1, which are non-inverting inputs for audio signals 1g, terminals (to) and inverting inputs for audio signals, Terminal → is ", voltage amplification stage glass input, terminal (b)
is the positive power input of the output stage, the terminal (to) is the negative power input of the output stage, and the terminal (to) is the negative 1 of the voltage amplification stage.
i source input, terminal 00 is the audio signal output, and terminal (4
1) is the circuit ground.

A constant voltage is supplied to the current input input (to) (to) of the voltage amplification stage by a constant voltage power supply connected to terminal - (to), while a diode is connected to the output stage's source input (g). (6
) The fact that a variable voltage is supplied according to the switching transistor (2) is consistent with Figure 3 mentioned above.
8) The output signal of the pressure amplifier (8), which is composed of the arithmetic amplifier c3n that amplifies the signal from the input terminal (1), the resistor wire, and the resistor (to) is transferred to the level shift element +21.
1 and resistance (A), or level shift element resistance V
The resistor is driven by a signal whose level is shifted by a constant voltage by C (g), and is configured to supply a constant voltage to the output stage power input terminal (b) or (to) of the integrated circuit when necessary. The ratio between the value of the resistor and the value of the resistor (7) will be set approximately equal to the ratio of the value of the resistor 0η and the value of the resistor vr, (2). According to such a configuration, a general-purpose integrated circuit can be used. Even when using the above-mentioned PIVM amplifier circuit +41+41
The variable voltage output of the amplified signal (2) can provide a drive signal for the transistor 181+8'l which is activated when tracking is not possible.

In addition, F#M amplifier circuit +41 which is a variable DC power supply circuit
Envelope of signal used for +41 ``4 pressure generation circuit 13) 1
The signal at the input terminal (1) may be used directly as the signal supplied to the operational amplifier 31, or the output signal at the output end QO of the output force amplification circuit +5115'l may be used as the manual signal to the operational amplifier 3B. It's okay. However, since the signal at the output terminal IIO is delayed from the input terminal (1), when used as an input signal to the operational amplifier C11l, the operation of the switching transistor +81+8'l is slower than the human input signal of the output stage transistor 151151. It means I'm going to be late, which I don't like.

As mentioned above, according to the power amplifier circuit drive 1 of the present invention, the flow source circuit 52 allows the use of circuit units such as general-purpose power and amplifier integrated circuits. Moreover, a lightweight and highly efficient tortoise force increasing device can be obtained.

[Brief explanation of drawings]

Figure 1 is a diagram showing the efficiency characteristics of the amplifier, and Figure 2 is 1! FIG. 6 is a block diagram of a driving DC power supply circuit for a power amplifier circuit that obtains high efficiency by controlling the aspirating pressure a; FIG. 6 is a circuit diagram for explaining the driving DC power supply circuit for a power amplifier circuit of the present invention;
FIG. 4 shows a specific embodiment of a driving DC power supply circuit for a power amplifier circuit according to the present invention. (1)...Input terminal, +21f141Q5 circle...
Voltage amplification circuit, (3)...Envelope i voltage generation circuit, +4+
(4'+... Pulse width amplification circuit (variable DC 1! Western supply circuit), +51+5'+... Power amplifier circuit, (6)
(61...unidirectional conductive element, +71UcJ=constant voltage DC power supply circuit, 5osf...switching, transistor, (9)lme 1
Published by Katsubo) q, 31 Kori 1

Claims (1)

[Claims] (1) A voltage amplification circuit that connects the human input signal terminal and the DC drive power supply terminal to which input signals are applied; a circuit unit comprising an amplifier circuit, an envelope voltage generation apposition for generating an envelope voltage of a signal of the input signal terminal or the output signal terminal, and an output voltage according to an output color final voltage of the circuit; A variable m-current power supply circuit that changes, the variable II DC source supply circuit, and the DC drive power supply terminals of the power amplifier 1 and 2 circuits are connected in series in the direction in which current is supplied from the variable DC power supply circuit. an amplifier circuit for amplifying the signal of the human input signal terminal or the output signal terminal; and a signal level converter for converting the amplitude level C signal exceeding the output signal terminal of the width surface road. A switching circuit 1, which is ON-OFF controlled by the output of the level conversion circuit and connected in a 100-row line between the 1 current drive power supply terminal of the power amplifier circuit and the constant voltage 100 current power supply circuit. When the output signal of the signal level conversion circuit becomes larger than the output voltage of the variable DC power supply circuit, the constant voltage II current power supply circuit power
101 paths of ``four direct current driving sources for a power amplifier circuit, characterized by supplying a direct current driving ring source to the squid amplifier circuit;