JPS5915146Y2 - Receiving machine - Google Patents

Description

[Detailed description of the invention] In a small radio receiver, the built-in battery is small, so the battery life is shortened.

Therefore, in order to make the battery last longer, it is possible to reduce the current consumption, but this would reduce the electrical output and make it impossible to obtain a high volume.

In view of these points, this invention is intended to enable effective power saving.

An example of this will be explained below.

In the figure, 1 is an antenna tuning circuit, 2 is a mixer circuit,
3 is a local oscillation circuit, 4 is its resonance circuit, 5 is an intermediate frequency amplifier, 6 is a detection circuit, 7 is a low frequency amplifier, and 8 is a speaker.

Then, a part of the intermediate frequency signal from the intermediate frequency amplifier 5 is supplied to a rectifier circuit 9 for tuning detection and rectified, and the rectified output is supplied to the base of the transistor 11.

Further, the parent contact of the power saving switch 61 is connected to the power supply line, the normal side contact N of the switch 61 is connected to the tuning display LED 21 through the resistor 31, and the LED
21 is connected to the collector of transistor 11, and its emitter is grounded.

Further, the power saving side contact E of the switch 61 is left unconnected.

Further, the audio signal demodulated by the detection circuit 6 is supplied to the base of the transistor 12 through a variable resistor 32 for volume adjustment.

A load resistor 33 is connected to the collector of this transistor 12, and the emitter is grounded through a resistor 34, so that the emitter of the transistor 12 is grounded.

Further, the collector of the transistor 12 is connected to the base of a drive transistor 13, the collector of this transistor 13 is connected to the primary coil of the drive transformer 51, and its emitter is connected to the power saving switch 62 through a resistor 35. The main contact of the switch 62 is connected to the side contact N and is further connected to the power saving side contact E of the switch 62 through the resistor 36, and the parent contact of the switch 62 is grounded through the capacitor 41 and also through the resistor 37 and, for example, the diode 22. Ru.

Further, both ends of the secondary coil of the transformer 51 are connected to the base of the output transistor 14.15, and the center tap of this secondary coil is connected to the connection center of the resistor 37 and the diode 22. The emitters of the transistors 14 and 15 are grounded, their collectors are connected to both ends of the primary coil of the output transformer 52, and their center taps are connected to the power supply line.

Thus, transistors 14 and 15 are class 8 push-pull.

Further, one end of the secondary coil of the transformer 52 is grounded, the other end is connected to the normal side contact N of the power saving switch 63, and the intermediate tap of this secondary coil is connected to the power saving side contact E of the switch 63. Furthermore, the speaker 8 is connected between the parent contact of the switch 63 and the ground.

In this case, the overall impedance of the secondary coil of the transformer 52 is set to a value that matches the speaker 8,
Further, the intermediate tap is located at, for example, a + position from the ground side in terms of the number of turns.

Furthermore, a negative feedback resistor 3 is connected between the hot side of the secondary coil of the transformer 52 and the emitter of the transistor 12.
8 is connected.

Note that 71 is a power switch, and 72 is a battery for power supply.

In such a configuration, the switches 61 to 63 are connected to the contact N
If connected to , normal operation occurs.

That is, when the tuning circuit 1 and the resonant circuit 4 are not tuned, no intermediate frequency signal is obtained, so a rectified output of the rectifier circuit 9 is not obtained, and the transistor 11 is off.

Therefore, the LED 21 does not light up.

However, when the tuning circuit 1 and the resonant circuit 4 are in tune, an intermediate frequency signal is obtained, so a rectified output is obtained in the rectifier circuit 9, which turns on the transistor 11.

Therefore, the LED 21 lights up to indicate that synchronization has been achieved.

Also, at this time, an audio signal is obtained from the detection circuit 6.

The resistors 35 and 37 and the diode 22 act as emitter resistors of the transistor 13, and
Since the capacitor 41 acts as a bypass capacitor, the audio signal from the detection circuit 6 is transferred to the transistor 12.
．． 13 and supplied to transistors 14 and 15 through a transformer 51.

Furthermore, at this time, the DC voltage obtained at the diode 22 is applied to the transistor 1 through the secondary coil of the transformer 51.
4.15 as its base bias, so
Transistors 14 and 15 perform class B push-pull operation.

Therefore, the audio signal from the transformer 51 is transmitted to the transistor 1
4.15, the power is further amplified and supplied to the speaker 8 through the transformer 52.

On the other hand, when switches 61 to 63 are connected to contact E, power is saved.

In other words, in this case, even if the synchronization is achieved, the switch 6
1, the LED 21 is not energized, so the current consumption of the battery 72 during tuning is reduced.

Furthermore, the audio signal is similarly amplified and supplied to the speaker 8, but since the speaker 8 is connected to the center tap of the secondary coil of the transformer 52, the transistor 14.1
The load impedance of transistors 14 and 15 is increased, so the collector current of transistors 14 and 15 is reduced, efficiency is improved, and the current consumption of battery 72 is reduced.

Further, since a resistor 36 is further connected in series to the emitter of the transistor 13, the collector current of the transistors 12 and 13 is reduced, and the current consumption of the battery 72 is also reduced.

Furthermore, since the collector current of transistor 13 decreases, the terminal voltage of diode 22 decreases, and the collector current of transistors 14 and 15 decreases, which also reduces the current consumption of battery 72.

In this case, when the collector current of transistor 13 decreases, the output of transistor 13 for driving transistor 14.15 decreases, but at this time, the load impedance of transistor 14.15 increases and transistor 14.15 Since the maximum output of transistor 13 has decreased, there is no problem even if the output of transistor 13 decreases by 1.

Also, when the collector current of transistors 14.15 decreases, crossover distortion increases, but at this time, since the load impedance of transistors 14.15 increases, there is no increase in crossover distortion, or even if there is It doesn't stand out.

Therefore, the current consumption of the battery 72 can be reduced without deteriorating the characteristics, and power can be saved.

In addition, when saving power, the load impedance of the transistor 14.15 increases, so the bare gain of the transistor 14.15 increases, while the negative feedback voltage increases from the transformer 52.
Since the current is stepped up by the secondary coil of Since the gain is reduced, the amplifier 7 does not become unstable.

Rather, the initial characteristics are improved by the increase in current negative feedback.

Thus, according to this invention, when high output is not required, power can be saved by switching the switches 61 to 63 to the contact point E, and the battery 72 can last for a long time.

Furthermore, a large output can be obtained by switching the switches 61 to 63 to contact N as necessary.

Moreover, in either case, excellent amplification operation can be performed without deterioration of characteristics.

In addition, in the above, the contact E of the switch 61 and the LED 2
A resistor with a relatively large value may be connected between the LED 21 and the LED 21 to reduce the display of the LED 21 when saving power.

[Brief explanation of drawings]

The figure is a connection diagram of an example of this invention. 61 to 63 are power saving switches.

Claims (1)

[Scope of utility model registration request] a drive transistor, an output transistor driven by the drive transistor, a speaker, an output transformer connected between the output transistor and the speaker, and a detection circuit that detects the presence or absence of an intermediate frequency signal. , a display means for displaying the tuning state based on the detection output of the detection circuit; a first switch for controlling operation/non-operation of the display means; and an emitter resistance of the drive transistor in conjunction with the first switch. a second switch that switches the value of , and a third switch that switches the connection between the secondary coil of the output transformer and the speaker in conjunction with the second switch, and the current path of the drive transistor. A receiver that obtains the bias voltage of the upper membrane output transistor from .