JP3153137B2 - Radio receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radio receiver using a DC-DC converter.

[0002]

2. Description of the Related Art Portable A with digital information display function
In the M radio receiver, the voltage of the battery power source is boosted by a DC-DC converter to drive the display device, but the DC-DC converter generates noise. -The DC converter is not working. FIG. 3 shows that during AM radio reception,
FIG. 7 is a circuit diagram of a main part of a conventional technique in which the operation of the DC-DC converter is stopped.

In FIG. 3, in a reception mode of AM radio, a switch 8 is connected to a side, and a DC-
The DC converter 4 is disconnected from the battery power supply 1 so that no power is supplied to the drive circuit 7 of the liquid crystal display device. In the AM radio reception mode, the processing amount of the microcomputer (hereinafter referred to as "microcomputer") 5 is small, so the switch 9 is also connected to the a side to supply the low voltage of the power supply battery 1 to the microcomputer 5 and the memory 6. To protect the memory 6,
The microcomputer 5 is operated in the low-speed mode (for AM reception).

A receiving circuit 2 of a radio receiver and the receiving circuit 2
The tuning circuit DC-DC converter 3 operates by supplying a low voltage from the battery power supply 1. DC-D for tuning circuit
The C converter 3 has low noise but low efficiency and cannot take out a large current.

In modes other than the AM radio reception mode,
Switches 8 and 9 are connected to the b side, and a DC
Operating the DC converter 4 and the microcomputer 5
Is set to the high-speed mode, and the memory 6 is set to the operating state.
As a result, data to be displayed is created by the microcomputer 5, and the drive circuit 7 of the liquid crystal display device is operated to cause the liquid crystal display device to perform a desired display.

At this time, both the microcomputer 5 and the memory 6 operate at high speed, and the digital circuit is also in an operating state.
The current consumption also increases, and the capacity of the tuning circuit DC-DC converter 3 becomes insufficient. Therefore, the digital circuit D
The C-DC converter 4 is operated.
Since the converter 4 generates noise, the microcomputer 5 mutes the reception circuit 2 of the radio receiver so that the noise does not appear in the audio output of the radio receiver.

[0007]

According to the above prior art, in the AM radio reception mode, the switch 8 stops the digital circuit DC-DC converter, and the switch 9 connects the microcomputer and the memory directly to the battery power supply. Connecting.

In modes other than the AM radio reception mode, the switch 8 operates the digital circuit DC-DC converter, and the switch 9 connects the microcomputer and the memory to the digital circuit DC-DC converter. Therefore, a switch 8 for switching the power supply of the DC-DC converter and a switch 9 for switching the power supply of the microcomputer and the memory are required, and there is a problem that the circuit mechanism becomes complicated and expensive.

In addition, the above-mentioned battery power supply and DC for digital circuit
-Since the output voltage of the DC converter is different, the power supply of the microcomputer and the memory is
-When switching to the output of the DC converter, the voltage applied to the microcomputer may change suddenly and cause a malfunction.

For this reason, the DC-DC for the digital circuit is used.
When the converter starts operating and its output voltage matches the voltage of the battery power source, it is necessary to switch the output from the battery power source to the output of the digital circuit DC-DC converter at a certain time. It is necessary to provide a control terminal of a switch for switching between the output of the DC-DC converter for use and the battery power supply, and the circuit configuration of the power supply voltage switching circuit is complicated and expensive.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above problems by providing a low noise first DC used in a tuning circuit.
In a radio receiver provided with a DC converter and a second DC-DC converter used for a digital circuit for processing display information, an output terminal of the first and second DC-DC converters is connected, An output voltage of the first and second DC-DC converters supplied to the circuit is supplied to the first DC-D converter by the second DC-DC converter.
It is characterized in that the C converter is higher.

Therefore, in the mode of receiving only a normal radio broadcast without operating the digital circuit for processing display information, the digital circuit of the tuner operates by the first DC-DC converter, and the receiving circuit operates by the battery power. . In this case, since a digital circuit such as a display circuit for processing a signal other than a normal radio broadcast is designed to be power-saving, a small amount of current is supplied to the digital circuit.
Therefore, the output of the first DC-DC converter whose output voltage is set to be high is supplied to a digital circuit that processes signals other than ordinary radio broadcasting, and the second DC-DC converter stops operating.

When a mode for processing signals other than ordinary radio broadcasting is set by a microcomputer or the like and a digital circuit such as a display circuit is activated, a current supplied to the digital circuit increases, and the first DC-DC converter is turned off. The output is insufficient, and the voltage applied to the digital circuit decreases. When the applied voltage becomes equal to the set output voltage of the second DC-DC converter, the second DC-DC converter starts operating, and thereafter, the second DC-DC converter is connected to the digital circuit.
Voltage is supplied from the converter.

When the mode for receiving only the normal radio broadcast is set again by the microcomputer or the like, the supply current to the digital circuit for processing signals other than the normal radio broadcast is reduced, and the output voltage is set again high. The voltage is supplied from the first DC-DC converter, and the second DC-DC converter
-The DC converter stops operating.

Further, the present invention is characterized in that, in the above configuration, the output terminals of the first and second DC-DC converters are connected via a constant voltage circuit or a constant current circuit.

When the outputs of the first and second DC-DC converters are connected via a constant voltage circuit, the first DC-DC converter
Since the output voltage of the converter is set higher than the output of the second DC-DC converter, even if the load current to the digital circuit that processes signals other than ordinary radio broadcasting decreases, the voltage applied to the load is reduced. An increase in voltage can be prevented.

When the outputs of the first and second DC-DC converters are connected via a constant current circuit, an increase in the output current of the first DC-DC converter whose output voltage is set to a high value is a constant value. And the first DC-D
Even if the efficiency and the supply capacity of the C converter are both low, the output can be stabilized and the power consumption can be reduced.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention, which is implemented in a portable radio receiver.
In FIG. 1, 21 is a battery power source, 22 is a receiving circuit of an AM radio receiver including a tuner, and 23 is the battery power source 21.
Is a low-noise, small-capacity tuning circuit DC-DC converter for supplying a boosted DC voltage to a digital circuit of a tuner provided in the receiving circuit 22 of the AM radio receiver.

Reference numeral 24 designates the battery power source 21 as a power source, and supplies a boosted DC voltage to a digital circuit such as a drive circuit 27 of a liquid crystal display device (LCD), a microcomputer 25 and a memory 26 for processing signals other than ordinary radio broadcasts. A DC-DC converter 28 for driving a digital circuit, a constant voltage circuit 28 is provided in series with a resistor 29, and is provided between both outputs of the DC-DC converter 23 for a tuning circuit and the DC-DC converter 24 for a digital circuit. The above digital circuit driving DC-
This is a smoothing capacitor provided at the output terminal of the DC converter 24.

During the AM reception, the microcomputer 25 and the memory 26
The constant voltage circuit 28 supplies a voltage slightly higher than the output of the digital circuit DC-DC converter 24 from the tuning circuit DC-DC converter 23 via the resistor 29. At this time, the microcomputer 25 operates in the low-speed mode, a small amount of current flows, and the voltage at the point (A) is the DC-D for digital circuit.
The output voltage is slightly higher than the output voltage of the C converter 24. Accordingly, the digital circuit DC-DC converter 24 stops operating, and the memory 26 performs only the memory holding operation by applying a low voltage.

The tuning circuit DC-DC converter 23
When the voltage at the point (A) is higher than the output voltage of the digital circuit DC-DC converter 24, the operation of stopping the voltage supply from the digital circuit DC-DC converter 24 will be described. FIG. 2 shows the DC-D for the digital circuit.
Chopper type step-up DC-D used for C converter 24
It is a circuit diagram of a C converter. In FIG. 2, 11 is P
WM controller, 12 is a comparator, 13 is a reference voltage, 1
4 is a rectifier, 15 is a coil, 16 is an FET, and 17 is a capacitor.
The DC converter 24 is configured. 21 is a battery power supply.

The FET 16 is controlled by the PWM controller 11.
Is turned on, energy is stored in the coil 15 from the battery power supply 21. When the FET is turned off, a back electromotive force is generated in the coil 15, and this back electromotive force is rectified by the rectifier 14 and stored in the capacitor 17. The voltage stored in the capacitor 17 is compared with the reference voltage 13 by the comparator 12.

When the terminal voltage of the capacitor 17 is higher than the reference voltage 13, the PWM controller 11
A control signal for shortening the ON time of T16 is output, the energy stored in the coil 15 is reduced, and the FET is turned off.
The generation of the back electromotive force of the coil 15 at the time of F is reduced, the charge accumulated in the capacitor 17 via the rectifier 14 is reduced, and the output voltage taken out as the terminal voltage of the capacitor 17 is reduced.

When the terminal voltage of the capacitor 17 is lower than the reference voltage 13, the PWM controller 11
A control signal for extending the ON time of the ET 16 is output, the energy stored in the coil 15 is increased, and the FET is turned on.
The counter electromotive force generated in the coil 15 at the time of FF is increased to increase the electric charge accumulated in the capacitor 17 via the rectifier 14, thereby increasing the output voltage extracted as the terminal voltage of the capacitor 17.

As described above, the output voltage can be boosted to a desired voltage according to the reference voltage 13. When the voltage at the output terminal (A) of the digital circuit DC-DC converter 24 becomes higher than the output set voltage due to an external factor or the like, the FET 16 of the digital circuit DC-DC converter 24 becomes
Does not turn on at all, and the DC-DC converter 24 stops operating. Therefore, in FIG.
When the voltage at the point (A) becomes higher than the output set voltage of the digital circuit DC-DC converter 24 by the C-DC converter 23, the digital circuit DC-DC converter 2
4 stops the operation.

On the other hand, when the drive circuit 27 of the liquid crystal display device is operated, both the microcomputer 25 and the memory 26 start operating at high speed, the current flowing out from the point (A) increases, and the tuning DC-DC converter 23 The required current cannot be supplied through the resistor 29, and the voltage at the point (A) drops. (A) The voltage at point is DC-
When the voltage drops to the output set voltage of the DC converter 24, as described in the DC-DC converter 24 shown in FIG.
The digital circuit DC-DC converter 24 starts to operate and stabilizes at the output set voltage.

Therefore, the driving circuit 27, the microcomputer 25, and the memory 26 of the liquid crystal display device have a digital circuit DC-
A predetermined output set voltage is supplied stably from the DC converter 24, and the microcomputer operates at a high speed. The drive circuit 27 for the liquid crystal display device discloses a normal operation, and information from the microcomputer 25 is displayed on the liquid crystal display. It is displayed on a device (not shown).

As described above, the supply of power to the digital circuits such as the microcomputer 25, the memory 26, and the drive circuit 27 for the liquid crystal display device by the load current flowing to the point (A) is performed by the tuning circuit DC-DC converter 23. Alternatively, the switching can be automatically performed so as to be performed by any one of the digital circuit DC-DC converters 24, and the voltage change at the time of the DC-DC converter switching can be smoothly performed.

The embodiment of the present invention shown in FIG. 1 includes a tuning circuit DC-DC converter 23 and a digital circuit DC-D
Although both output terminals of the C converter 24 are connected by a series circuit of the constant voltage circuit 28 and the resistor 29, they may be connected by a series circuit of the constant current circuit and the resistor 29.

When the DC-DC converters 23 and 24 are connected by a series circuit of a constant voltage circuit 28 and a resistor 29, the set voltage of the tuning circuit DC-DC converter 23 is changed to the digital circuit DC-DC converter 24. Is higher than the set voltage, it is possible to prevent an increase in voltage applied to a load composed of a digital circuit such as the drive circuit 27 of the liquid crystal display device, the microcomputer 25, and the memory 26 even if the load current decreases.

The two DC-DC converters 23,
When a constant current circuit and a resistor 29 are connected in series, the output voltage of the tuning circuit DC-DC converter 23 whose output voltage is set to be higher than that of the digital circuit DC-DC converter 24 is increased. Tuning circuit DC-D that can be limited to a constant value, has low efficiency, and has low supply capacity
The output of the C converter 23 can be stabilized and the power consumption can be reduced.

[0032]

According to the present invention having the above-described structure, when the driving circuit of the display device is not operated, a low-noise tuning circuit DC-DC converter with a high output voltage is set to all circuits. When the voltage is supplied and the drive circuit of the display device is operated, the digital circuits other than the tuning circuit digital circuit are automatically supplied with the voltage from the digital circuit DC-DC converter.
-Switching between DC converters is smooth, there is no sudden voltage change at the time of switching, and a malfunction of a digital circuit such as a microcomputer does not easily occur. In addition, both DC-D
The switching between the C converters is automatically performed in response to the switching of the load, so that the circuit configuration is simple and inexpensive.

When both DC-DC converters are connected via a constant voltage circuit, the voltage applied to the digital circuit does not increase even if the load current to the digital circuit decreases, so that a digital circuit such as a microcomputer is used. Can be prevented from malfunctioning.

When the DC-DC converters are connected to each other via a constant current circuit, the output current of the tuning DC-DC converter can be limited to a constant value, and the output of the tuning DC-DC converter can be limited. Stability and reduction in power consumption can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a main part of one embodiment of the present invention.

FIG. 3 is a block diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Battery power supply 22 Receiving circuit 23 Tuning circuit DC-DC converter 24 Digital circuit DC-DC converter 25 Microcomputer 26 Memory 27 Liquid crystal display drive circuit 28 Constant voltage circuit 29 Resistance

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/16 H02M 3/00

Claims (3)

(57) [Claims] 1. A low-noise first DC used in a tuning circuit.
In a radio receiver provided with a DC converter and a second DC-DC converter used for a digital circuit for processing display information, an output terminal of the first and second DC-DC converters is connected, An output voltage of the first and second DC-DC converters supplied to the circuit is supplied from the second DC-DC converter to the first DC-DC converter.
A radio receiver characterized in that the converter is higher. 2. The radio receiver according to claim 1, wherein output terminals of said first and second DC-DC converters are connected via a constant voltage circuit. 3. The radio receiver according to claim 1, wherein the output terminals of said first and second DC-DC converters are connected via a constant current circuit.