JPS6028307A - Audio amplifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to audio amplifiers, and more particularly to audio amplifiers coupled with remote location speakers.

Public address systems and audio broadcast systems are well known and widely used. Generally, such systems include an audio source, amplification means, and one or more centrally located or remotely located speakers. One such configuration
One example is a system that includes a central audio source, with or without some amplification device, and one or more remote amplifier/speaker combinations. Such systems require the transmission of both the audio signal to be amplified from the central audio source to the location of the remote amplifier speaker and the power signal used by the amplifier in amplifying the audio signal. One example of such a device is disclosed in U.S. Pat.
No. 258,832. The device of the US patent uses a two-wire transmission system to transmit both audio signals and DC power voltage. The amplifier includes means for separating the audio signal and power. The audio signal is separated by a capacitor and the power is separated by a magnetic core inductor that passes only DC voltage and blocks the audio signal. Unfortunately, such systems are susceptible to variations in power output due to variations in the DC voltage transmitted for power amplification. Additionally, disadvantages may arise due to the size and weight of the magnetic core inductance used to separate the DC voltage from the audio signal.

Accordingly, the present invention provides amplifier means, a single two
In an audio amplifier of the type having terminal input means and circuit means for isolating the signal from the power,
capacitor means for coupling and amplifying the signal from the terminal input means to the amplifier means and for blocking the power; and capacitor means for isolating and amplifying the power from the signal and directing the power to the amplifier means. an audio amplifier characterized in that it includes voltage regulator means coupled to said input terminal means for supplying said signal for use in amplifying said signal.

The present invention will be described in detail with reference to the accompanying drawings. In the attached diagram,
An audio amplifier circuit 10 is shown generally including an input section 12, a filtrate or separation section 14, and an amplification section 16. Speaker means 18 are shown connected to the output of amplifier section 16.

Generally, input section 12 includes two pairs of input terminals 20-23. The second pair of terminals 22 and 23 are directly joined to terminals 20 and 21, respectively. The purpose of duplicating the input terminals is to easily connect the amplifier and speaker combination to a transmission line having other amplifier/speaker combinations. Input terminals 2 and 22 are coupled to the separation or filtrate section 14, while input terminals 21 and 28 are connected to circuit 1.
Connected to 0 ground. Input terminals 2o and 21 are used to receive an input signal that is a combination of an alternating audio frequency signal and a direct voltage that powers the circuit 1o.

Terminals 20 and 22 are coupled to the anode of diode 24, and the cathode of diode 24 is coupled to the voltage regulator means 260 input and to the capacitor 280 edges. Voltage regulator 26 and capacitor 28 constitute a separation section or filtrate section used to separate the audio signal and DC voltage power. voltage regulator 2
Many types of voltage regulators are used in the 6.

National Sem for equipment in very good working order
There is a unit manufactured by 1con-ductor. This device is an integrated circuit type three terminal voltage regulator called LM317. Manufacturer National se
According to the Micronduc-907 standard, this voltage regulator requires the addition of two resistors, designated 3o and 32, to adjust the output voltage. When connected in this way, the voltage regulator 26 separates DC power from the input terminal and uses it as power to be supplied to the amplification section 16 . The LM81'l type voltage regulator used is 80
It has performance including decibel ripple rejection rate. That is, the ripple or alternating current appearing at the input terminal of voltage regulator 26 is reduced by 80 decibels at the output terminal of the voltage regulator. As mentioned above, the separation or filtrate section 14 includes a condenser 28 . In this example, an electrolytic capacitor with a positive terminal connected to the cathode of diode 240 is used.

The other terminal of the capacitor 28 is used to supply the audio signal to the amplifier section 16 for amplifying the audio signal. A plurality of resistors 34-39 are coupled in series and a voltage divider formed by these resistors is coupled between the other end of capacitor 28 and ground of circuit 10.

This voltage divider (thus provides multiple audio signal voltage levels that are used to vary the output signal from the amplifier). The other terminals of each of these pairs of jumper terminals are brought together and connected through a capacitor 42 to the input of amplifier means 44. Place jumper 41 on (
and the audio signal is coupled to an amplifier means 440 input. Which pair of jumper terminals is used determines the signal level coupled to amplifier means 44 and therefore the output signal level of amplifier means 44.

The amplifier means of this example is also a Nation-a
l LM3B'i3 manufactured by Semlconductor
It is an integrated circuit operational amplifier called . A compatible alternative is an amplifier manufactured by Fairchild, Inc. called the TDA2002. Capacitor 42 is coupled to the non-inverting input of the amplifier. Amplifier means 44 includes power input terminals 46 and 48. Note that the terminal 48 is connected to the circuit 1.
0 ground, and terminal 46 is connected to voltage regulator 2
6 output. Voltage regulator 26 thus powers amplifier means 44 to perform its amplification function. Capacitor 50 is voltage regulator 26
The other end is connected to the amplifier's ground for the purpose of filtering out any unwanted signals that may occur on this power line. Another capacitor 52 is used for a similar purpose between the output of amplifier 44 and amplifier ground. Amplifier 44 uses a feedback path between its output terminal and its inverting input terminal. This path includes a resistor 54 connected in series with a capacitor 56. A midpoint between resistor 54 and capacitor 56 is connected to ground through resistor 58.

It should be noted that the LM38B type amplifier and amplifiers of that type have the performance advantage of 80 dB power rejection. That is, the signals appearing at power input terminals 46 and 48 will be reduced by 80 decibels at the output terminals. This performance improves the separation between the audio signal and the DC power signal.

The output of the amplifier means 44 is connected through a DC blocking capacitor 60 to the power terminal of the drive coil 62 of the loudspeaker means 18. The other end of the drive coil 62 is grounded.

The operation will be explained below. Circuit 10 functions as follows. An input signal comprising a DC voltage and an audio signal superimposed on the DC voltage is sent to terminals 20 and 21. The DC voltage is generally positive at terminal 20 relative to terminal 21. The composite signal (well, except for a forward bias voltage drop of about 0.6V, passes through diode 24 entirely unchanged).

Capacitor 28 separates the audio signal from the composite signal and passes it to the amplifier 440 input while blocking any further DC voltage. A voltage regulator 26 coupled to the diode 240 power source conversely conducts a DC voltage and at the same time blocks the audio signal. DC voltage does not pass through completely. Only the portion representing the regulated output voltage passes through. This section is coupled to the power input of amplifier 44 and is used to amplify the audio signal. As mentioned above, the audio signal is connected to the resistor 34.
. . . 39. From this voltage divider, audio signals of various voltage levels are sent to an amplifier 44.
is coupled to the non-inverting input of Such a connection is made by a jumper 41 disposed on any one pair of jumper terminals of jumper block 40. Amplifier 44 uses the supplied DC voltage to amplify the audio signal and energizes speaker means 18 for broadcasting the audio signal.

With the above structure, even if the supplied DC voltage fluctuates, the output of the amplifier remains constant up to the speaker means 18. Additionally, there is no need to place unnecessarily bulky or heavy magnetic core inductance in the amplifier/speaker enclosure.

[Brief explanation of drawings]

The accompanying drawing is a circuit diagram of one embodiment of the present invention. 12...2-terminal input means 14...Voltage regulator means 16...Amplifier means 28 Capacitor means Patent applicant: Mnauto Industries, Inc. (4 others)

Claims (1)

Claims: 1) amplifier means, a single two-terminal input means for receiving both a signal for amplification by the amplifier means and power used by the amplifier means in amplifying the signal; and from the power; In an audio amplifier of the type having circuit means for isolating said signal, capacitor means for coupling said signal from said two terminal input means to said amplifier means for amplification and for blocking said power; voltage regulator means coupled to the input terminal means for separating and amplifying the power from the signal and supplying the power to the amplifier means for use in amplifying the signal. audio amplifier. 2) An audio amplifier as claimed in claim 1, characterized in that said voltage regulator means comprises an integrated circuit type voltage regulator. 8) The audio amplifier of claim 2, wherein the voltage regulator has a ripple rejection of approximately 80 decibels. 4) Audio according to claim 2, characterized in that said amplifier means includes an integrated circuit operational amplifier means having a power rejection ratio to improve the separation between said audio signal and said power. amplifier. 5) An audio amplifier as claimed in claim 4, characterized in that the power rejection ratio of said operational amplifier means is approximately 80 decibels.