JPS59200507A - High-band on circuit of high efficiency amplifier - Google Patents

Abstract

PURPOSE:To prevent the breakdown of an output transistor (TR) due to an unnecessary signal except in an audio frequency band by adding a capacitor to a detecting circuit part. CONSTITUTION:The capacitor C3 is added to the detecting circuit part 3 in parallel to a resistance R2. Therefore, a low-potential DC voltage is developed at a point A at a high frequency except in the audio frequency range because of a time constant C2XR1. Consequently, a control circuit 1 turns on TRs Q3 and Q4 when the potential at the point A is low to apply the output of a power source VL to output TRs Q1 and Q2. Thus, when the frequency is higher than the audio band, the output TRs Q1 and Q2 operate by the power source VL and do not operate by a power source VH, preventing the abnormal heating of the output TRs Q1 and Q2 and their breakdown caused by the abnormal heating. Thus, the output TRs are prevented from breaking down by an unnecessary signal except in the audio frequency range.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency ON circuit for a high-efficiency amplifier that controls the operating state depending on the frequency of an amplifier that has a plurality of power supply circuits that drive the power amplification stage of the amplifier.

It has two power supply circuits, a high-efficiency amplifier, trivL*VH, and is driven by ML or by vacuum depending on the input signal level (details of this operation are omitted).

This switching of the power supply is performed by the control circuit 1 shown in FIG. Q1tQ
2 operates with the cat's power supply and drives the speaker 2.

-Also, when the control circuit 1 turns off the transistors Q3 and Q4, the power source (2) is switched to the diode D2. Via D3, it is applied to the output transistor Q t sQ2, which output transistor Ql.

It operates with the power of Q 2 FiML and drives the speaker 2'.

As shown in FIG.
By turning on and off tQ4, diodes D2. By turning D3 on and off, the power supply for vH and the power supply for (2) are switched to operate the output transistors Q1#Q2.

At this time, when the frequency becomes high, switching pulses are generated, which worsens the distortion of the amplifier.

Therefore, when using a high frequency signal (3KHz or higher), regardless of the input signal level, if the connection drive method is used with only a high voltage, switching of diodes D2 and D3 will be eliminated, and deterioration of distortion will be prevented. can.

This on-circuit in the high frequency range is shown as a specific example in the detection circuit section 3 of FIG. In FIG. 1, the output of the amplifier, that is, the connection of the collectors of the output transistors Q 1 e Q 2, the terminals, and the point B is connected to the input terminal of the control circuit 10 through the capacitor CI, resistor R1, and diode D1. . The connection point between resistor R1 and diode D1 is grounded via resistor R2, and diode D1
The cathode of is grounded via capacitor C3. The detection circuit section 4 on the negative half cycle side is similarly configured.

In the detection circuit section 3 on the positive half cycle side, the time constant '?' due to the resistor R2 and the capacitor C1. 1-After the signal at point B is rectified by the circuit of diode D1 and capacitor C2 using C1 and R2, the level at the input end of control circuit 1, that is, at point A increases at a high frequency.

Control circuit 1 controls transistor Q according to the potential at point A of
By turning on s t Q4, the output transistors Q1 and Q2 are operated with a power source, as described above.

This high-frequency on-circuit will operate even if it receives a signal other than the audio band (for example, an oscillation waveform), or if the amplifier itself oscillates, the amplifier will operate due to the power supply from the cat. transistors, namely output transistors Q1. There are cases where Q2 is destroyed.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional technology.When an unnecessary signal such as an oscillation force that exceeds the audio band is generated, the operation of the high-frequency ON circuit is stopped and the power transistor is destroyed. The purpose of the present invention is to provide a high-frequency on-circuit for a high-efficiency amplifier that can prevent this.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a high-frequency on-circuit for a high-efficiency amplifier according to the present invention will be described with reference to the drawings. FIG. 2 is a circuit diagram showing a main part of one embodiment, and is an improved circuit diagram of the detection circuit section 30 on the positive half cycle side in FIG. 1.

As is clear from a comparison with the detection circuit section 3 of FIG. 1, FIG. 2 has a feature 4 in that a capacitor C2 is connected in parallel to the resistor R2. Points A and B in FIG. 2 are the same as points A and #B in FIG. 1, respectively.

In this way, by connecting the capacitor C2 to the resistor R2 in parallel, the signal at the output amplifier, that is, the connection point between the collectors of the output transistors Ql and Q2 in FIG. 7+-CI・R1 and Maz-R1
- The two time constants of C2 will be added to the rectifier circuit made up of diode D1 and capacitor C3.

As a result, the level of the frequency interpersonal point becomes as shown in FIG. In FIG. 3, the broken line characteristic α is for the detection circuit section 3 shown in FIG. 1, and the solid line characteristic β is for the invention shown in FIG. 2.

In FIG. 3, the range between frequencies f and f indicates the audio band, and frequencies below f1 and above frequency f indicate outside the audio band.

In the audio band between frequencies f1 and 12,
Is the detection circuit part Ma J-C1? Depending on the time constant of R2, when the frequency is low, a low potential DC voltage appears at point A,
Furthermore, when the frequency is high, a high potential DC voltage appears at point A.

Furthermore, in the case of a high frequency outside the audio band of 12 or more, a low potential DC voltage appears at point A due to the time constant of IL-C2 and R1.

As a result, the control circuit 1 in FIG.
The output transistors Ql and Q2 operate with the power supply.

Conversely, when the potential at point A is high, the control circuit 1 turns on the transistor Q3tQ4 and applies the corresponding power to the output transistors Q and 'pQ2. The output transistor Q'eQ2 is operated.

Therefore, even in the case of high frequencies outside the audio band, the output transistors Ql and Q2 operate with a power supply of vL,
The output transistors Ql and Q will no longer operate due to the low power supply.
Abnormal heat generation and damage caused by it can be prevented.

Of course, in the audio band, when the frequency is high, the output transistors Q1 and C2 operate with a power supply of 'vH, so as in the conventional case, the diodes D2. D3
This eliminates switching and prevents deterioration of distortion.

As described above, according to the high-frequency on-circuit of the high-efficiency amplifier of the present invention, in an amplifier in which the output transistor is operated by switching between multiple high-voltage and low-voltage power supplies by the control circuit, it is possible to operate the output transistor outside the audio band. When a high frequency signal is generated, this signal is passed through a predetermined time constant (B) path to lower its level and then added to the control circuit, so that the amplifier does not generate heat due to unnecessary signals outside the audio band. Destruction can be prevented at all times.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional high-efficiency amplifier and a high-frequency ON circuit, FIG. 2 is a circuit diagram of an embodiment of a high-frequency ON circuit of a high-efficiency amplifier of the present invention, and FIG. 3 is a circuit diagram of a conventional high-efficiency amplifier and a high-frequency ON circuit of the present invention. FIG. 3 is a diagram showing a comparison of frequency characteristics of high-frequency ON circuits. Ql, C2... Output transistors D1-D3... Diodes C1-C3... Capacitors R1, R2... Resistance 1... Control circuit 2... Speaker 3... Detection circuit section Patent applicant Pioneer Corporation

Claims (1)

[Claims] a switching means for switching between a high voltage power source and a low voltage power source and supplying the same to the output transistor; and a first time constant that detects the frequency of the signal applied to the output transistor and detects the frequency of the signal applied to the output transistor and when this frequency is within the audio band. Detection that outputs a low-level DC voltage at low frequencies, outputs a high-level DC voltage at high frequencies, and generates a low-level DC voltage with a second time constant in the case of high frequencies outside the audio band. When the circuit unit and the detection circuit unit are generating the low level DC voltage, the switching means controls the low voltage power source to be applied to the output transistor.
A high-frequency ON circuit of a high-efficiency amplifier, which is a control circuit that controls the switching means to apply high-voltage power to the output transistor when the detection circuit section generates a high-level DC voltage. Wow