JPH0472401B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of intermittent power supply from an external power source to a power amplifier.

Electrodes are supplied from an external power source to a conventional power amplifier by a mechanical switch (simply referred to as a switch) installed on a line that supplies the power amplifier and the external power. Therefore, the switch used for this needs to have a coulometric capacity commensurate with the power supplied to the power amplifier from the external power supply, and naturally the size of the switch increases depending on the amount of power required. However, this restriction on the size of the switch is currently an obstacle to reducing the size and weight of the parts used to make the system smaller and lighter.

FIG. 1 shows a block diagram of a conventional power amplifier. In FIG. 1, when external power supply switch 2 is closed, power is supplied from external power supply 1 to bias circuit 3, and bias circuit 3 becomes operational.
Next, the bias circuit 3 puts the first amplification stage 4 and the predriver stage 5 into the operating state, and after that,
The output amplification stage 6 becomes operational, and the entire power amplifier device becomes operational.

In this way, conventional power amplifiers operate and deactivate depending on the opening and closing of the external power switch, but switch 2 can handle large transient currents at the rated output of the power amplifier and when switch 2 opens and closes. It needs to be durable and is larger than a switch in a small signal system. Therefore, this has been a major obstacle in reducing the size and weight of system components.

An object of the present invention is to provide a power amplifying device that solves the problem of increasing the size of the conventional power switch.

The power amplification device of the present invention connects the first stage amplification stage to the power supply via the bias circuit, connects the output amplification stage to the power supply without going through the bias circuit, and operates the bias circuit by a switch to amplify the first stage. A power amplification device that supplies current from the power supply to the power supply stage through the bias circuit, thereby activating the first amplification stage and activating the output amplification stage, the bias circuit is a first transistor whose collector is connected to the power supply and whose emitter is connected to the first amplification stage, a first resistor connected in series between the base of the first transistor and a reference potential point, and a capacitor, a second transistor whose base is connected to the switch and is turned on and off according to the state of the switch, and the second transistor between the connection point between the first resistor and the capacitor and the power supply. and a second resistor connected in series with the collector-emitter path.

According to this configuration, the operating voltage and current to the first amplification stage are supplied from the bias circuit, and the collector current of the second transistor, which becomes conductive when the switch is turned on, is supplied to the base of the first transistor. The signal is amplified by the first transistor and supplied from the emitter of the first transistor to the first amplification stage. Simply supplying the current flowing through the collector-emitter path of the second transistor to the first amplifier stage without passing through the first transistor.
It is necessary to increase the current flowing through the collector-emitter path of the second transistor, and accordingly, the base current of the second transistor must be increased, and the size of the switch through which this base current flows is reduced. things become difficult. On the other hand, according to the configuration of the present invention, the current flowing through the collector-emitter path of the second transistor may be large enough to put the first transistor into operation. Since the base current only needs to be much smaller, the switch connected to the base of the first transistor can be made very small.

Furthermore, when the bias circuit is operating, a voltage with suppressed ripples superimposed on the power supply voltage can be supplied as the operating voltage to the first amplifier stage, and when the power amplifier is started up by a switch, the charging voltage of the capacitor connected to the circuit node can be supplied as the operating voltage. Since the operating voltage to the first amplifying stage also changes in accordance with the change in the power amplifier, sudden changes in the output of the first amplifying stage can be prevented and shock noise from the output of the power amplifier can be prevented.

Moreover, the power amplifier device of the present invention is integrated circuit,
If the connection point between the first resistor and the capacitor is the input terminal of this integrated circuit, the first resistor will serve as a base protector for the first transistor.

Next, the present invention will be explained by examples.

FIG. 2 is a block diagram showing the basic principle of the present invention. In FIG. 2, an electronic switch 7 is connected between the bias circuit 13 and the power source 1, and one end of the electronic switch 7 is connected to a reference potential point, for example, a ground point 8.
Continuity is established by turning on (closing) the mechanical contact external power switch 12 connected to the power supply switch 12 . Then, when the electronic switch 7 is turned on, the bias circuit 13 is turned on by the power supply 1.
This operation causes the initial amplification stage 4, pre-driver stage 5, and power amplification stage 6 to operate.

FIG. 3 is a circuit diagram of one embodiment of the present invention. In FIG. 3, transistor 7 corresponds to electronic switch 7 in FIG. 2, and by turning on external switch 12, the base of transistor 7 is grounded and transistor 7 is turned on. Therefore,
The capacitor 33 is charged with a time constant determined by its capacitance value and the resistance value of the resistor 32, and the charging voltage is supplied to the base of the transistor 21 via the resistor 31, making the transistor 21 conductive and putting the bias circuit into an operating state. becomes. The transistor 21 forms a ripple filter circuit together with a capacitor connected to its base, suppresses ripples superimposed on the power supply 1, and supplies a stable voltage to the first amplification stage. As a result, the transistor 22 of the first amplification stage,
23 and 24 become operational, and at the same time, the transistor 25 of the pre-driver stage and the transistors 26, 27, 2 of the power amplification stage including the driver
8 and 29 are also in operation, and the input signal applied to the first amplification stage is amplified through each amplification stage to provide the required output power to the load 30.

The power amplifier device of the present invention is turned on by turning on the external power switch 12, and the on-current flowing through the external power switch 12 is used to turn on the transistor 7 of the electronic switch. Since the current is minute, on the order of several to several hundred microamperes, an extremely small device is sufficient to turn this current on and off. Therefore, according to the present invention, the external power switch can be easily downsized. Furthermore, when the switch 12 is turned on, the operating voltage is not immediately supplied to the first amplifier stage 4, but the voltage is supplied with gradual changes due to the actions of the transistor 7, resistor 31, and capacitor 33, so that so-called shock noise is eliminated. It is possible to prevent such output from occurring. That is, according to this embodiment, the switch 12
Not only can the capacitor 33 for the ripple filter be used to prevent the shock noise that may be generated when the switch 12 is turned on.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional power amplifier, Figure 2 is a block diagram showing the basic principle of the present invention, and Figure 3 is a block diagram of a conventional power amplifier.
The figure is a circuit diagram of an embodiment of the present invention. 1...Power supply, 2,12...External power switch,
3, 13...bias circuit, 4...first amplification stage,
5... Pre-driver stage, 6... Power amplification stage, 7...
...Electronic switch (transistor), 8...Grounding,
21...bias circuit transistor, 22,2
3, 24...first stage amplification stage transistor, 25...
Pre-driver stage transistor, 26, 27, 2
8, 29...power amplification stage transistor, 30...
load.

Claims (1)

[Claims] 1 The first amplification stage is connected to the power supply via a bias circuit, the output amplification stage is connected to the power supply without going through the bias circuit, and the bias circuit is operated by a switch to supply current from the power supply to the first amplification stage. is supplied through the bias circuit, thereby activating the first amplification stage and activating the output amplification stage, the bias circuit having a collector connected to the power supply. a first transistor whose emitter is connected to the first amplification stage; a first resistor and a capacitor connected in series between the base of the first transistor and a reference potential point; and a first transistor whose base is connected to the switch. is connected to the switch and turns on/off depending on the state of the switch.
a second transistor that is turned off; and a second resistor connected in series with the collector-emitter path of the second transistor between the connection point between the first resistor and the capacitor and the power supply. A power amplifying device characterized by: