JPS5899011A - Power 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 to single-power amplifiers, such as audio frequency amplifiers that operate over a wide range of voltages, frequencies, and amplitudes to drive an effective load impedance (eg, a speaker).

Music reproduction power amplifiers used in loudspeakers must amplify the input voltage to a suitable value, typically in the range of 20 to 4 Q db, and supply it to the loads, which are normally or Resistive or inductive loads, or a combination of the two, have an average value between 2 and 10 ohms, but can vary between 1 and 100 ohms over the entire audio frequency range. It increases as the temperature rises, and has the property of changing instantaneously depending on the output level. This output voltage varies between 0 and the clip value, typically 5 to 2
Between 0db? - has an output.

One important caveat in this regard is that transformerless output circuits designed with a constant supply voltage and a specific load impedance are extremely inefficient for impedances significantly lower than the design value. The bad news is that it can only output a fraction of its normal output into fairly high impedances.

Varying the supply voltage proportionally to the square root of the load impedance solves this problem, but this is not an optimal solution.

One important object of the present invention is to provide a power supply device for a power amplifier, which is equipped with a constant voltage supply 11 device to provide the effective safe maximum power when the average power of the amplifier is extremely low and extremely high. The aim is to improve the output voltage by equipping the power supply device with an output voltage variable device so that the output voltage is considerably higher than the effective safe maximum output of the amplifier.

A further object of the invention is that when the signal processed by the amplifier is music or a similar irregular waveform and the load is a speaker or the like, the amplifier operates at a relatively high voltage for most of its operating time; Therefore, the purpose is to output a higher effective maximum output level than the output level when used with a regular waveform and a simple resistive load.
This is consistent with the purpose stated above.

A further object of the invention is that the amplifier outputs essentially the same power for load impedances from 2 ohms to 8 ohms, and that the power supply device maintains its output (preset to its maximum voltage) at a constant This does not contradict any of the above objectives.

A further object of the invention is to keep the temperature fluctuations at the amplifier output within a small range, thereby stabilizing the power consumption and therefore the temperature rise, and as a result improving long-term reliability. No contradiction.

Yet another object of the present invention is to create a heavy voltage variable output power supply as an efficient, simple and low cost low frequency thyristor switching power supply, eliminating internal power losses essentially within the transformer circuit of the power supply. This is consistent with any of the aforementioned objectives.

Yet another object of the invention is that an amplifier with a given feeder and power output stage has at least two
It is designed to operate as if it had twice the power rating and is consistent with any of the aforementioned objectives.

The above-mentioned object is a power amplifier according to the present invention, which includes a heat generation power output stage of the power amplifier, a power supply device for supplying power to the power amplifier, detecting the heat generated from the power output stage, and generating a signal inversely proportional to the heat generated from the power output stage. A device for controlling the voltage output value of the power supply device, continuously adjusting the supply voltage to an optimum value according to changes in load impedance, and stabilizing the current at the output stage. This can be achieved by an amplifier.

This feedback is configured to have a non-linear response by increasing the amount of negative feedback when the detected heat (power consumption) reaches a predetermined limit.

The safe operating limits of a power amplifier are determined by the tolerance of the power amplifier output stage and the instantaneous voltage-current product. The heat of the power output stage, and more particularly the heat of the heat sink on which the semiconductor of the output stage is mounted, is roughly proportional to the average power of the output stage. Therefore, the voltage value of the power supply device driving the power amplifier and its output stage can be controlled by negative feedback of the temperature signal of the heat sink. In this way, the temperature of the heat dissipating section of the output stage can be maintained at a safe limit value or below, while at the same time the operating voltage value of the power supply device can be reduced to its maximum possible value TIC. The feedback signal is inversely proportional to the sensed temperature. Therefore, as the temperature increases, the voltage output of the power supply decreases.

If the amplifier were to be operated at very low or very high average power and with a high impedance load for the corresponding music vector, the temperature would be very low and the supply voltage would be at its maximum value, causing output margin (h
This dynamic power margin in which eaaroom ) becomes very high refers to a power margin that lasts for several minutes. This is because the thermal time constant of the heat sink is approximately 10 minutes. Therefore, continuous high-volume melodies, such as voices and solo instrument sounds, are not clipped. This response is essentially insensitive to such short-term peak values. This process is performed automatically using the improved amplifier power supply system of the present invention.

When power consumption is very high, for example when playing rock music, its peak value is 4 ab compared to the average over a long period of time.
In some cases, the supply voltage is reduced to reduce power consumption until the temperature settles to a safe value. Fortunately, music of the type that requires the maximum dynamic range does not put much strain on the amplifier in terms of energy consumption. In most classical music, the average power over time is very low for most of the time, eg less than 5 watts on average, although there are occasional very high level peaks. In contrast, short-term peaks occur when passages with an average output of more than 150 watts last for several minutes, with a peak output of 400 watts.
There are some things that are different.

The amplifier power supply according to the invention allows the following amplifier conditions: 1. The amplifier has a very large dynamic output margin (4(ib)) when loaded with any impedance; 2. Short term (several minutes) during which, if necessary, there is virtually continuous output clipping for solos and solos (in conventional amplifiers with large dynamic output margins, the power supply would quickly fail).

3. It has the maximum output margin when it is most needed, that is, when the ratio of peak value to average power is very large.

4. In dormitory conditions, the amplifier outputs power to an 8 ohm load and an 8 ohm rated speaker with less distortion than prior art amplifiers.

5. Designed for long term reliability with unique applicability and tolerance for very extreme changes in operating conditions for professional applications; 6. Short term (I HIP)
It is operated at an output of over 400 watts, with a medium-term continuous rating of about 300 watts and a minimum rating of 100 watts, which is sufficient to satisfy the requirements for artistic stereo listening. and the short-term output of Z exceeds 1 kW, which indicates that even a low-efficiency speaker can be driven at a sound pressure level of approximately 120 AB.

Other objects, features and advantages are set forth in the following description of the presented embodiments, with reference to the accompanying drawings.

FIG. 1 shows the proposed embodiment of the invention, 1i! : Zuku power supply [10 is shown. The components of the power supply device are shown. (Typical rating values are also shown.) Part name Symbol
Notes (model name), Transformer TR-1117V Shore phase rectifier - Diode Dl-D4 Engineering N54
01 diode D5 engineering N40021
D6 Engineering N914 Thyristor 5
cR-10116B Tranzosta TI, T2. T3 BD139 resistor R-127 to Dl '/4 ""
Ω to R-222, 〃# R-327
Ω to I/I R-41 Ω, 〃#
Dl 1/2" to R-51 Constant current source 10YG2.0 Capacitor C-110μ? # O-24700μF + 8ov Rectifier DI-D4
This is a slow-switching power supply device that switches a thyristor for each period of the full-wave rectified signal (how the output of the signal is generated). The phase shift circuit PSN varies the firing angle and controls such that sufficient current can flow during each cycle so that the average neutral voltage at terminals 12.14 is maintained at the desired value.

The power supply device 10 supplies its output voltage to the amplifier A (the long side is OFF and the output is 0) via the terminal 12.14. The feedback circuit from the output stage of the amplifier comprises a current 9 which is considered to vary in the circuit of FIG. 1 in direct proportion to the instantaneous voltage-current product of the output stage of the amplifier.

When a single phase 60 cycles are supplied, the period (wavelength) of the supply power frequency is approximately 18 i 1) seconds.

The conduction interval of 5OR-1' typically ranges from 3 to 15 milliseconds of each period. The components selected as above for the device 10 meet the general conditions of the invention, i.e. the response time of said device is approximately half the supply frequency, i.e. 18
The noise is made when the condition of 36 milliseconds is met. The resulting transient high level peaks can be passed through without introducing distortion before the supply voltage at terminals 12.14 is reduced by The short-time performance of the amplifier can be used to increase the dynamic output to the amplifier.1 Even if the amplifier's output transistor is rated for operation at 3.5 amps and 150 volts, the short-time performance of the amplifier can be used to increase the dynamic output power to the amplifier. That means it can tolerate up to 7 amperes.

In order to implement this control restriction in order to allow a larger dynamic power application area, a device must be provided to limit the maximum consumption in absolute value. This means that the output transistor temperature of the amplifier is gj
This can be solved by introducing a feedback loop gain when A (corresponding to the voltage-current product as shown above, or the temperature & measured face-to-face at the heat sink of the transistor) is reached.

The output supply voltage v8 of the device f110 is connected to the resistor circuit group R1 to R4.
and the pace-emitter voltage of transistor T6 os
It is determined according to the following formula: Power consumption &C By substituting the related current 1, the following becomes: x4. vb, -[51 Figure 2 shows the same or an equivalent circuit in the form of a block diadem. Power amplifier A It'! .

Current is applied to an impedance load (e.g. a speaker coil) at voltage V-. and at least its final output stage K) uses a supply voltage V. Reference voltage v1 is v8
The analog voltage multiplier VM is generated using a resistor from VM
Applying v2 ” (VB - vO) from K creates a feedback signal; feed/four-trick signal b3
Engineering. (V8-Vo) is sent to contact X via a polarizer. The feedback signal from the final output stage of the person [a value that varies directly with the power consumption in that part] is passed through a resistor Rth and a temperature/voltage converter T/v (for example a thyristor) to the signal xIPa.

We supply contact XK. This total: (3) KxPd + 2P (12 is contact Y (as a negative addition coefficient) iC reference voltage ref
and is supplied with the active element E to create an overall control signal.

Figure 2 is a generalized example, and Figure 1 is an example of the IC% determination.
The correspondence with the circuit shown in the figure is as follows.

Fig. 2 1 Fig. 1 vrof11 source/P TR-1, Dl ~ D4, 8
OR-1, PANR, R5 AVM R1-R4 T/VT3 Various variations can be made within the scope of the invention with the elements specifically and generically described above. For example, in the circuit of FIG. 1, the feedback circuit signal 1 is connected to the temperature circuit, i.e.
(made of a thermistor) replaces the temperature of the output transistor of amplifier A with a thermal iIE path,
It is possible to add this temperature circuit.

feedback? It is also possible to replace o1j *- with a transformer TR-IK, for example, by winding a high-resistance auxiliary winding υ in the transformer and equipping it with a basic resistor.

Figures 3A and 6B show two output margin states,
The first figure 6A shows, for example, a case where rock music is played with a dynamic range of 4 dB, that is, a range of 400 watts compared to an average output of 150 watts. The supply voltage is gradually reduced until its clip value is 200 watts. Therefore, the peak value is 3 d
Only B is clipped. However, the present invention (Figure 3B)
Clips performed by do not change the tone.

It will be apparent to those skilled in the art that, given the advantages mentioned above, many other uses and modifications can be made based on the embodiments described herein without departing from the concept of the invention. The scales are obvious. Accordingly, the present invention is hereby incorporated by reference as to all novel features and novel combinations of features shown and retained in the apparatus and technology that are limited solely in spirit and scope to the appended claims. It is interpreted as operating each of the following.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an amplifier equipped with a power supply according to an embodiment of the invention; FIG. 2 is a block diagram of a more generalized form of the device of FIG. M3A and FIG. It is a logarithmic graph with time on the horizontal axis and power on the vertical axis, showing the operating effect of the effective power level as it moves away from and approaches the effective clip power level. FIG. 4 shows the relationship between power consumption and output power at the primary supply voltage. 10... Power supply device 12. 14... Output reservoir PSN... Phase shifter AVM... Analog voltage multiplier O Patent application No. ri) θri 8 No. 2, Name of the invention 4@flea 3, Person making the amendment Relationship to the case Patent applicant 4, Agent 5, Date of amendment order February n, 1988 6 , Number of inventions increased by amendment 7, Subject of amendment

Claims (1)

[Scope of Claims] (1) A power amplifier, comprising: a device forming a power output stage that generates heat within the power amplifier; a device forming a power supply device providing power to a front power amplifier; It detects the heat generated from the power output stage, generates a signal inversely proportional to it, controls the voltage output level of the power supply, adjusts the supply voltage to an optimal value in relation to changes in load impedance, and controls the current in the output stage. A power amplifier consisting of a stabilizing device. (2. In the power amplifier according to claim 1, the feedback is a power amplifier (3 ) !!#Claim 2. The power amplifier according to claim 1 or 2, further comprising a device that is insensitive to a short-term peak value of the voltage-current product in the output stage. (4) The power at the output stage of the amplifier is included in the amplifier and power supply used for widely varying frequency and amplitude amplifier inputs, such as those used in audio frequency amplifiers with a dynamic range near 4ab. A power amplifier and power supply device characterized in that output power is continuously controlled by measuring consumption and using the measured power consumption signal as a negative feedback V-back signal to limit the supply voltage.