JPH0834388B2 - amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention mainly relates to an amplifier used in an audio device or the like.

(Prior Art and Problems) What is generally known as an audio frequency signal amplifier is an amplifier circuit and a configuration in which a DC power source is supplied to the amplifier circuit as a power supply device.

Among such amplifiers, a circuit as shown in FIG. 7 has been proposed as an amplifier which pursues particularly high power conversion efficiency.

FIG. 7 is composed of a power supply device 11 and a pulse width amplifier 12, and a signal obtained by combining the analog input signal vi input to the pulse width amplifier with a sawtooth wave signal made as a reference signal is grounded by a comparator. It is compared with the level and converted into a pulse width signal c.

The pulse width signal c is sent to the base registers d and e, and every time the transistors Q ₃ and Q ₄ are turned on / off, the output signal f from between the emitters is amplified by the supply of the DC voltage from the power supply device, and the Converted to an analog signal,
Output from load drive R _L such as speaker.

Such an amplifier is characterized by using a pulse width amplifier and a transistor to amplify the analog input signal vi.

The transistor has a problem that it may be destroyed when a large current and a high voltage are supplied, and thermal noise is easily generated.

Furthermore, power supply, etc. Power consumption must shed load supply current always proportional to the voltage value of the input signal to the many diode D ₅ to D ₈ energy loss Ross and transistor Q _3, Q ₄ is increased element Is included.

(Means for Solving Problems) As means for solving the above problems, the present invention provides a pulse width modulation unit for generating a pulse width modulation signal from an input signal, and an output signal from the pulse width modulation unit. A frequency multiplier that multiplies the frequency by 2n times (n is a natural number) for each cycle, an amplifier that amplifies the output from the frequency multiplier, and the output of the amplifier is multiplied by 2n for each cycle before multiplication. And a frequency-reducing regenerator for amplifying the signal of.

(Operation) With such a configuration, in order to make the pulse-width-modulated input signal a signal that does not contain a DC component, the frequency is 2n.
(N is a natural number) times, the power is amplified by switching the DC power source connected to the input side of the amplifier, and the output signal is supplied to the load on the output side.

This output signal is output by the frequency-reducing regenerator for each cycle.
The signal before being multiplied by 1 in 2n is given in an amplified form.

 Therefore, a simple amplifier can be provided.

(Embodiment) Next, an embodiment of the present invention will be described with reference to FIG.

In FIG. 1, 21 is a pulse width modulator, 22 is a frequency multiplier, and 23
Is an amplifier, and 24 is a frequency-reducing regenerator.

This will be described in detail with reference to FIG. 2 showing FIG. 1 in detail.

In FIG. 2, the input signal vi is AD-converted by the AD converter 2 and is sent to the amplifier via the pulse width modulator 3 and the frequency multiplier 4.

The amplifier is composed of two sets of directional switching devices 5 and a primary winding L ₁ on the primary side of the transformer T, and the frequency-reducing regenerator is composed of four sets of inverter circuits with different combinations. Connected AND circuit 9 and transformer T 2
The secondary side is composed of a secondary winding L ₂ and four sets of directional switching devices 9, and is output to a load 7 such as a speaker via a low-pass filter 6.

 Next, the operation in FIG. 2 will be described.

The DC voltage V ₁ is supplied to the midpoint of the primary side of the transformer T.

On the other hand, the AD converter 2 samples the analog input signal vi in the direction of the time axis component and reads the value of the voltage axis component at which the analog input signal and the sampling value intersect.

The pulse width converter 3 shapes the waveform of the digital signal (b) based on the value of the voltage axis component. The frequency of the digital signal (b) is 2n (n is a natural number) by a multiplier.
The multiplied square wave signal (c) is sent to an AND circuit 9 connected to a phase inverting inverter having four different combinations.

A primary switching device SW having directionality depending on whether the multiplied square wave signal is a positive half cycle or a negative half cycle.
ON / OFF control is performed alternately for 1 and SW2.

By the ON / OFF operation of the primary switching devices SW1 and SW2, the direction of the current on the primary side of the transformer T starts from the midpoint of the primary winding toward both ends of the primary winding.

Transformer T secondary switching device having a directionality to the secondary side SW3, SW4, SW5, SW6 are connected in parallel to the secondary winding L _2, the secondary winding L ₂ midpoint A ground, a load 7 such as a speaker, and a low-pass filter 6 are connected to the position.

The DC voltage V ₁ on the primary side is converted into each of the square-wave AC voltages V ₂ and V ₃ generated between both ends of the secondary winding L ₂ and the midpoint of L ₂ , and the direction of the current is switched. SW1, SW2, SW3, SW4,
Determined by the combination of ON and OFF of SW5 and SW6.

The secondary switching devices SW3, SW4, SW5 and SW6 are switched on when the output value from the AND circuit 9 is in a positive state, and are switched off when the output value is in a negative state.

The deciding factor for whether the output value from the AND circuit is in the positive state or the negative state is a combination of whether the signals (b) and (c) are positive half cycles or negative half cycles with respect to each other. Determined by

FIG. 4 shows an output signal (b) from the pulse width converter which is a factor that determines the direction of the current flowing through the secondary side of the transformer T.
The ON / OFF states of the switching devices SW1, SW2, SW3, SW4, SW5, and SW6 are summarized according to the timing of the signal and the multiplied signal (c).

The waveform in FIG. 3 (d) is shaped with respect to the load resistance R _{L in} FIG. 2 with the position in (d) as a base point and the direction flowing to the winding L ₂ as a positive component. On the contrary, the direction flowing from the winding L ₂ to (d) is shaped as a negative component.

As a result, the signal waveform shown in FIG. 3 (d) is a signal having the same frequency as that in (b). By applying the signal of the item (d) to the load resistance R _L through the low-pass filter 6, a waveform having the same frequency as the analog signal vi input as the input means is amplified and output (e).

FIGS. 3 (a) to 3 (e) show operation waveforms of respective parts with respect to a predetermined input signal vi.

The above is the description when n is 1, but the same can be said when n is 2 or more.

In the present embodiment, the switching device having a unidirectional property has been described, but it can be implemented by using a bidirectional switching device, and a circuit diagram at that time is shown in FIG.

Although the detailed operation principle is omitted, FIG. 6 shows a combination table for turning on / off each switching device which controls the direction of current by a combination of the signal (b) and the signal (c) in the positive half cycle or the negative half cycle.

(Effect of the Invention) According to the present invention, it is possible to obtain an amplifier that efficiently amplifies a signal including a DC component with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a circuit diagram in the case where the switching device is unidirectional in the embodiment of the present invention shown in FIG. 3 (a) to 3 (e) are waveform diagrams showing the circuit operation of FIG. 2, respectively, and FIG. 4 shows the direction of the current depending on the timing of the signal (b) and the signal (c) of FIG. It is a figure which shows the combination table which turns on / off each switching device to control. FIG. 5 shows an embodiment in which the switching device has bidirectionality. FIG. 6 is a view showing a combination table for turning on / off each switching device in FIG. FIG. 7 is a circuit diagram showing a conventional example. 2 ... AD converter, 3 ... pulse width converter, 4 ... frequency multiplier, 5 ... primary switching device, 8 ... secondary switching device, 9 ... AND circuit connected to inverter, T ……Trance.

Claims (1)

[Claims] 1. A pulse width modulator that generates a pulse width modulated signal from an input signal, and a frequency multiplier that multiplies the frequency by 2n (n is a natural number) for each cycle of the output signal from the pulse width modulator. It is composed of an amplifier for amplifying the output from the frequency multiplier and a frequency-reducing regenerator for multiplying the output of the amplifier by 1 / n for each cycle to obtain an amplified signal before multiplication. Characteristic amplifier.