JPS63156433A - Radio receiver - Google Patents

Abstract

PURPOSE:To realize an AM radio receiver requiring small current consumption, by reducing the consumption in a power amplifying stage when an electric field is weak or a sound volume is lowered. CONSTITUTION:A first detecting stage 10 detects electric field strength corresponding to the amount of an operating current to settle the gain of an IF amplifying stage 5. A second detecting stage 11 detects the state of sound volume adjustment. A control stage 12 controls the idling current of the power amplifying stage 8 corresponding to the output signal of the first detecting stage 10 or the second detecting stage 11. Therefore, it is possible to decrease the idling current of a power amplifier circuit when the electric field is weak or the sound volume is lowered, and to reduce unrequired current consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to improvements in radio receivers, and particularly to radio receivers with reduced current consumption.

(B) Prior Art One of the requirements for a portable AM radio receiver using a battery as a power source is low current consumption. Generally, the AM radio receiver is configured using a high frequency IC and a power amplification IC, but the power amplification IC has a larger current consumption than other ICs, and the AM radio receiver is In order to reduce current consumption, it is necessary to reduce the current consumption of the power amplification IC.

Incidentally, a push-pull amplifier circuit operating in class B is usually used in the output stage of a power amplification IC. The push-pull amplifier circuit has a basic problem of generating crossover distortion and switching distortion, but if a sufficient idling current flows through the amplification transistor, the crossover distortion and switching distortion can be reduced. I can do it. However, in portable type AM radio receivers, it is not possible to allow a large amount of idling current to flow due to the battery life, so either the battery life or the distortion rate has to be sacrificed.

In order to solve the above-mentioned problems, a push-pull amplifier circuit designed to reduce current consumption has been proposed and put into use, as disclosed in Japanese Patent Laid-Open No. 108208/1983. The push-pull amplifier circuit has an improved circuit configuration and can reduce crossover distortion and switching distortion with low current consumption.

(c) Problems to be Solved by the Invention However, in the conventional push-pull amplifier circuit, the idling current is fixed at a predetermined low value that can reduce crossover distortion and switching distortion. Even when the electric field strength decreases and the distortion factor worsens in the RF amplification stage or the IF amplification stage, an idling current that can reduce the distortion in the power amplification stage continues to flow. In a state where the distortion factor has worsened in the previous stage, it is meaningless to reduce the distortion in the power amplification stage, and will only lead to a needless increase in current consumption, so some kind of improvement has been desired.

Furthermore, as mentioned above, the idling current required to improve crossover distortion and switching distortion and the idling current required to obtain maximum output are relatively burdensome currents for the battery, and are unnecessary in abnormal listening conditions. be. For example, if a phone call is received while listening to a radio broadcast, the volume is usually turned down, but there is no point in running an idling current in such a situation, and it will only lead to battery consumption.

(d) Means for Solving the Problems The present invention has been made in view of the above points, and includes a first detection means for detecting the electric field strength of the received signal, and a first detection means for detecting the volume adjustment state of the receiver. The present invention is characterized in that it comprises two detection means, and a control means for controlling the idling current of the power amplification stage according to the output signal of the first detection means or the second detection means.

(f) Effect According to the present invention, when the electric field strength of the received signal is small,
By reducing the idling current of the power amplification stage, it is possible to reduce the current consumption of AM radio receivers. Furthermore, when the volume is turned down, the idling current can be reduced to reduce current consumption.

(f) Embodiment FIG. 1 shows an embodiment of the present invention, and (1) is A.
(2) is an RF amplification stage that amplifies the received signal; (3) mixes the output signal of the RF amplification stage (2) with the output signal of the local oscillation circuit (4); I
(5) is an IF amplification stage that amplifies the IF multiplied signal; (6) is a detection stage that detects the AM multiplied signal; (7) is a volume adjustment that controls the level of the detected output signal. (8) is a power amplification stage that amplifies the output signal of the volume adjustment stage (7) and applies it to the speaker (9); (10) is a first detection stage that detects the electric field strength of the received signal; (11) ) is a second detection stage that detects the volume adjustment state, and (12) is a second detection stage that detects the power amplification stage (8) according to the output signal of the first detection stage (10) or the second detection stage (11). This is a control stage that controls idling current.

The signal received by the antenna (1) is sent to the RF amplification stage (2)
The signal is amplified by the mixing stage <3), and the signal can be converted by IF times. The IF multiplied signal is amplified at the IF amplification stage (5), and AM detection is performed at the detection stage 6). The low frequency signal obtained at the output end of the detection stage (6) is level-adjusted at the volume adjustment stage (7), and then amplified at the power amplification stage (8) and applied to the speaker (9). (9) emits sound according to the received signal. The operation of the AM radio receiver described above is the same as that of conventionally known receivers.

The first detection stage (10) is for detecting the electric field strength of the received signal. The first detection stage (10) is, for example, I
The electric field strength is detected by the thickness of the operating current that determines the gain of the F amplification stage (5). When the electric field strength of the received signal is small,
Since no gain control is performed, the operating current of the IF amplification stage (5) is small. Also, if the electric field strength of the received signal is large,
Since gain control is performed, the operating current of the IF amplification stage (5) becomes small. The first detection stage (10) generates a signal depending on the magnitude of the operating current. The second detection stage (11) detects the state of volume adjustment. An electronic volume that can obtain a resistance value proportional to the thickness of the control signal is known, but when the electronic volume is used as the volume adjustment stage (7), the resistance value can be adjusted by detecting the control signal. In other words, the volume adjustment state can be detected.

For example, when controlling the volume adjustment stage (7) so that the volume becomes large when the control signal is small and the volume becomes small when the control signal is dog, the second control signal indicates that the control signal is dog. It can be detected by the detection stage (11). In addition, when using a general mechanical volume as the volume adjustment stage (7), the fixed terminal of the mechanical volume is connected to the detection stage (6) via an input capacitor, and the movable terminal of the volume is connected to the power amplification stage. If it is connected to the stage (8) via an output capacitor and a DC current is passed through the volume, a DC voltage corresponding to the position of the movable terminal is generated, and the DC voltage is detected by the second detection stage (11). and an output signal can be generated from the second detection stage (11) when the volume is turned down.

The control stage (12) controls the idling current of the power amplification stage (8) according to the output signal of the first detection stage (10) or the second detection stage (11). When the electric field strength of the received signal is large, no output signal is generated from the first detection stage (10), but when the electric field strength decreases to a predetermined value, an output signal is generated, and the control stage (12) Upon receiving the signal, the idling current of the power amplification stage (8) is reduced. Also,
The volume adjustment stage (7) is controlled, the second detection stage (11) detects that the volume has been reduced, and the second detection stage (11)
When an output signal is generated from the control stage (12), a control signal is generated from the control stage (12) to reduce the idling current of the power amplifier stage (8).

Therefore, by using the circuit shown in FIG. 1, it is possible to reduce the idling current of the power amplifier circuit when the electric field is weak or when the volume is turned down, and unnecessary ti consumption can be reduced.

Figure 2 shows a specific circuit example of the main part of Figure 1.
13) is an input terminal to which an input signal to be amplified is applied, (14) and (15) are first and second bridriver transistors, and (16) is an output signal of the first bridriver transistor (14). (17) is a second driver transistor that operates in accordance with the output signal of the second driver transistor (15); (C) is the output signal of the first driver transistor (16); (20) is a constant current source that supplies a reference current; (21) is a second current inverting circuit that inverts the output signal of the second driver transistor (17); 22) and (23) are first, which flow a current equal to the current flowing through the constant current source (20);
The second and third transistors (2A) consist of fourth and fifth transistors (25) and (26);
A third current inversion circuit that inverts the output current of the transistor (23), (27) a sixth transistor that supplies a current flowing to the fifth transistor (26), and (28) a first
a detection stage, (29) is the second detection stage, and (sum) is the first detection stage;
This is a fourth current inversion circuit whose output control current changes according to the output current of the detection means (28) or the second detection means (29). Note that the fourth transistor (25) is for determining the idling current of the second driver transistor (17), and the sixth transistor (27) is for determining the idling current of the first driver transistor (16). be. In addition, the first and second current inverting circuits (1
8) and (S) constitute the output stage of the power amplification stage, and by setting the inversion ratio to 1:n, the current is amplified by n times.

If the current flowing through the constant current source (20) is 11, then the collector currents of the first to third transistors (21) to (23) will also be 1+ (inversion ratio set to 1=1), and the When the collector currents of the Bridriver transistors (14) and (15) are 1. If the base bias is set so that the following occurs, the drive currents of the first and second driver transistors (16) and (17) become zero when there is no signal. In addition, the collector 1 of the third transistor (23)
Style 1. flows into the fourth transistor (25) together with the output current I2 of the fourth current inversion circuit (Chen), and flows into the fifth transistor (25) whose base and emitter are commonly connected to the fourth transistor (25).
Transistor (26) and the fifth transistor (26)
A sum current 11+L of the above-mentioned currents also flows through the sixth transistor (27) which supplies the collector current. Depending on the current 1 + + I z flowing through the fourth transistor (25),
The collector current of the second driver transistor (17) is I
++It, and the first driver transistor (1
The collector current of 6) is also Il+I! becomes. And the first
In accordance with the current Il+It flowing through the second driver transistors (16> and (17)), currents I and +I also flow through the first and second current inverting circuits (su) and (infra). Therefore, First and second driver transistors (16
An idling current of a predetermined value I++Iz continues to flow through the first and second current inverting circuits (17) and (17) even when there is no signal, thereby reducing crossover distortion and switching distortion. can be measured. In addition, to arbitrarily set the inversion ratio of transistors connected in a current inversion relationship, each transistor is set to an arbitrary x different from I++It.
i can be made to flow, and the total idling current can be made the minimum value that can reduce crossover distortion and switching distortion.

When a positive input signal is applied to the input terminal (13), the first
and second Bridriver transistor (14> and (15)
) increases, the first driver transistor (16) is driven, and the current flowing through the first current inversion circuit (tsubo) flows to the load. Furthermore, when a negative input signal is applied to the input terminal (13), the collector currents of the first and second Bridriver transistors (14) and (15) decrease,
The second driver transistor (17) is driven, and the current flowing through the second current inverting circuit (S) flows to the load. Therefore, if the circuit shown in FIG. 2 is used, the load can be driven in push-pull mode.

In a state where strong electric field reception is being performed, the output current of the first detection stage (28) becomes small. In this state, if the volume is not reduced by the volume adjustment stage (7), the output current of the second detection stage (29) will also be small. In that state, the collector current of the diode-connected seventh transistor (31) constituting the fourth current inversion circuit (4) is approximately at the resistance (
32), and the collector current of the eighth transistor <33) constituting the fourth current inversion circuit (reference) also has the same value. Since the collector current of the eighth transistor (33) is supplied to the fourth transistor (25), the collector current of the eighth transistor (33) is supplied to the first and second driver transistors (16) and
7) and the idling current flowing through the first and second current inverting circuits (1 and 2) have a predetermined value that can reduce crossover distortion and switching distortion.

In the state where weak electric field reception is being performed, the output current of the first detection stage (28) becomes a dog, and the seventh transistor (
31) decreases, the collector current of the eighth transistor (33) also decreases, and the current flowing to the fourth transistor (25) decreases. Therefore, the idling current flowing through the first and second driver transistors (16> and (17)) and the first and second current inverting circuits (tsubo> and (su)) becomes extremely small.

When the volume is reduced by the volume adjustment stage (7), the output current of the second detection stage (29) becomes constant. Therefore, as in the case of a weak electric field, the seventh and eighth transistors (31) and (
33) decreases, and the fourth transistor (2
5), first and second driver transistors (16) and (17), first and second T-flow inversion circuits (Tsubo) and (Ai)
The current flowing through the circuit also decreases.

(G) Effects of the Invention As described above, according to the present invention, the current consumption of the power amplification stage is reduced when the electric field is weak or the volume is turned down, so AM radio reception with low current consumption is achieved. We can provide equipment.

In particular, since the first and second detection stages and the control stage are composed of elements such as transistors and resistors, they can be formed on a single integrated circuit board together with the IF amplification stage and the power amplification stage. It is suitable for use in a 1-chip IC type AM radio receiver.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a circuit diagram showing a specific example of the circuit. (5)...IF amplification stage, (7)...Volume adjustment stage,
(8)...Power amplification stage, (10)...First detection stage, (11)...Second detection stage, (12)...Control stage.

Claims (1)

[Claims] (1) first detection means for detecting the electric field strength of the received signal;
A radio receiver comprising a second detection means for detecting a volume adjustment state of the receiver, and a control means for controlling an idling current of a power amplification stage according to an output signal of the first detection means or the second detection means.