JPH0115218Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention is a PCM that encodes analog signals in binary.
In an amplifier that operates using a signal as an input signal,
The present invention relates to an amplifier that changes power supply voltage according to the amplitude of an input signal. Conventionally, amplifiers have been known that detect the amplitude of an input signal in an analog manner and change the power supply voltage based on the detection output. The circuit configuration of control circuits etc. becomes complicated, and
There were also problems with the adjustment required to carry out the prescribed control and its responsiveness. In view of these points, the present invention converts analog signals into two
This system focuses on an amplifier that operates using a base-encoded PCM signal as an input signal, and has improved the conventional drawbacks as described above, and will be explained in the following figure. In FIG. 1, an amplifier 1 converts a PCM signal extracted from a recording medium into an original audio signal (analog signal) using a D/A converter 2, and then amplifies the power using a power amplifier 3 to load the This is a configuration that drives (speaker) 4. Note that the PCM signal is obtained by sampling an audio signal at regular intervals and pulse code modulating the amplitude at each sampling point.
It is given by [Q _o Q _o-1 ……Q ₂ Q ₁ ]. For example, the relationship between the amplitude of the PCM signal represented by 4 bits, which is obtained by sampling the amplitude of the audio signal in 16 steps, and the amplitude of the audio signal is shown in FIG.
i.e. the amplitude of the audio signal

[0] as PCM
Signal [0000], amplitude [1] as PCM signal [0001]...
...Make each amplitude [15] correspond to the PCM signal [1111]. 5 are different power supply voltages V _n , V _n-1 ...V ₂ , V ₁
A power supply circuit that outputs (V _n >...>V ₂ > V ₁ ),
Each power supply voltage is determined by the switching circuit S _n , S _n-1 ...S ₂ ,
The signals are supplied to the power amplifying section 3 via _S1 , respectively. 6 is a logic circuit that detects the amplitude of the analog signal corresponding to the PCM signal in multiple stages, and each detection output C _n , C _n-1 ... C ₂ , C ₁ is connected to the above switching circuit.
By inputting S _n , S _{n - 1} . The different power supply voltages are switched by the detection output of the logic circuit 6, and the power supply voltage supplied to the power amplification section 3 is increased or decreased in response to an increase or decrease in the amplitude of the analog signal. . Hereinafter, a specific example will be described in which the power supply voltage is changed in three stages when the PCM signal is represented by a 4-bit signal. FIG. 3 shows the power supply circuit used in this embodiment, in which taps T ₃ , T ₂ , and T ₁ for outputting different AC voltages are provided on the secondary side of the power transformer 7 on both the positive and negative sides. The AC voltages between T ₃ -T ₃ , T ₂ -T ₂ and T ₁ -T ₁ are rectified and smoothed by known rectifier circuits 8, 9 and 10, respectively, and positive and negative voltages are applied to each output terminal. Obtain DC voltages V ₃ , V ₂ , V ₁ , −V ₁ , −V ₂ , −V ₃ . Here, each DC voltage has a relationship of V ₃ > V ₂ > V ₁ . FIG. 4 is a diagram showing a specific example of the logic circuit 6, switching circuits S ₃ and S ₂ and the amplifier 1. For simplicity, the switching circuits S ₃ and S ₂ will only be described on the positive side. They each have the same configuration, and include a driving transistor Q ₂ to which the detection output of the logic circuit 6 is input, and a driving transistor Q _{2 .}
It consists of a switching transistor _Q1 that is turned on and off by the collector output of the transistor Q1. The DC voltages V ₃ , V ₂ are applied to the switching transistors Q ₁ , Q ₁ of each switching circuit S ₃ , S ₂ , and the diodes D ₃ , D connected in the forward direction to the switching transistors Q ₁ , Q ₁ . ₂ to the positive power supply terminal of the amplifier 1, respectively. In addition, the lowest voltage, DC voltage V ₁ , is used to supply power to amplifier 1 via diode D ₁ connected in the forward direction, in order to always supply a constant DC voltage to amplifier 1 and maintain it in an operating state. Supplied directly to the terminal. The negative side switching circuit is also constructed in the same manner as shown. The logic circuit 6 obtains the OR output of the fourth digit [Q ₄ ] and third digit [Q ₃ ] of _the PCM signal [Q ₄ Q 3 Q ₂ Q ₁ ].
It is composed of an OR circuit 11 and an AND circuit 12 that obtains an AND output, and the OR output of [Q ₄ ] and [Q ₃ ] is sent to the drive transistor Q ₂ of the switching circuit S ₂ , and
The output is the driving transistor of switching circuit _S3
Each is input to Q ₂ . Furthermore, since the PCM signal [Q ₄ Q ₃ Q ₂ Q ₁ ] is shown in Table 1, the logical sum and logical product of [Q ₄ ] and [Q ₃ ] are as shown in the same table, and the logical sum is When the amplitude is [4] or more, it becomes a high level [1], and when the AND amplitude is [12] or more, it becomes a high level [1]. That is, the amplitude is

It is detected in three stages: [0] to [3], [4] to [11], and [12] to [15]. Next, the operation of a specific example of the above configuration will be explained. The amplitude is

When the PCM signal is between [0] and [3], that is, between [0000] and [0011], the OR circuit 11's logical sum output and the AND circuit 12's logical product output are both output.

[0], both switching circuits S ₃ and S ₂ are in a cutoff state, and therefore, the lowest voltage, DC voltage V ₁ , is supplied to amplifier 1 via diode D ₁ . Next, when the amplitude is from [4] to [11] (PCM signal [0100] to [1011]), the logical sum output of the OR circuit 11 is [1], so the switching circuit _S2 becomes conductive. A direct voltage V ₂ is supplied to the amplifier 1 via a diode D ₂ . At this time, since the DC voltages V ₁ and V ₂ have a relationship of V ₂ >V ₁ , the diode D ₁ is biased in the opposite direction. The amplitude is [12] ~ [15] (PCM signal [1100] ~
[1111]) is the logical sum output of OR circuit 11, AND
The AND output of the circuit 12 becomes [1], and both switching circuits S ₃ and S ₂ become conductive.
Since the DC voltages V ₃ , V ₂ , and V ₁ have a relationship of V ₃ > V ₂ > V ₁ , the diodes D ₂ and D ₁ are both biased in the opposite direction, and only the DC voltage V ₃ is passed through the diode D ₃ . The signal is then supplied to the amplifier 1. As is clear from the above explanation, the present invention samples an analog signal at regular intervals and generates a PCM signal [Q _o Q _o-1 ...Q ₂ Q ₁ ] in which the amplitude at each sampling point is binary encoded. In an amplifier that operates as an input signal, the PCM signal is
It is equipped with a logic circuit 6 that detects the amplitude of an analog signal corresponding to the signal, and a power supply circuit 5 that outputs different power supply voltages.The power supply voltage of the power supply circuit 5 is switched by the detection output of the logic circuit 6, and the The power supply voltage is increased or decreased in response to an increase or decrease in the amplitude of the analog signal.
Since the detection is performed digitally using PCM signals, the detection accuracy is increased, the operation is reliable, and the response is significantly improved, which has excellent practical advantages.

【table】 [Brief explanation of drawings]

Figure 1 is a diagram showing the configuration of the amplifier of the present invention, Figure 2 is a diagram showing the configuration of the amplifier of the present invention.
This figure shows the relationship between the amplitude of an audio signal and a PCM signal, and FIGS. 3 and 4 are diagrams showing an embodiment of the amplifier of the present invention. 5 is a power supply circuit, and 6 is a logic circuit.

Claims (1)

[Scope of utility model registration request] The analog signal was sampled at regular intervals and the amplitude at each sampling point was binary encoded.
An amplifier that operates with a PCM signal [Q _o Q _o-1 ...Q ₂ Q ₁ ] as an input signal, and converts the PCM signal to a D/
Convert to the original analog signal by A converter 2,
In the amplifier that amplifies the analog signal by the power amplification section 3, the PCM signal is extracted from the PCM signal.
The logic circuit 6 includes a logic circuit 6 that detects the amplitude of an analog signal corresponding to a signal, and a power supply circuit 5 that outputs different power supply voltages.
An amplifier characterized in that the power supply voltage supplied to the power amplifying section 3 is increased or decreased in response to an increase or decrease in the amplitude of the analog signal by switching based on the detection output of the analog signal.