JPH0212761Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a selective call receiver having a visual display function.

[Technical background of the invention]

In general, a selective call receiver receives a selective call signal emitted from a base station (not shown) via an antenna 1 in a radio circuit 2, demodulates it in a demodulation circuit 3, and converts it into a baseband signal, as shown in FIG. 4, for example. The signal is converted into a time-division multiplexed signal, and this signal is compared with the own individual number code stored in advance in the storage circuit 5 in the code matching circuit 4. When the two match, it is determined that a call to the self has occurred. The drive signal is supplied to a speaker 7 as a sound indicator via an amplifier circuit 6, thereby generating a ringing tone.

By the way, in this type of selective calling receiver,
In recent years, it has been proposed that, in addition to the above-mentioned speaker 7, a visual display such as a light emitting diode is provided as a call display means, and the visual display notifies the occurrence of a call. FIG. 5 shows an example of the configuration of the display circuit, in which a drive signal for generating a sound generated from the code matching circuit 4 is current-amplified by an amplifier circuit 8 and then supplied to a light-emitting diode 9. This allows the light to be emitted at the same frequency as the sound. In addition, numeral 10 in the figure is a current limiting pit. However, since selective call receivers generally use batteries with a power supply voltage of 1.5V, such as manganese dry batteries, as they are, the forward voltage drop will increase.
The light emitting diode 9 cannot be driven with electricity of 1.7V or more. Conventionally, therefore, a booster circuit has been provided to increase the drive voltage, but this booster circuit is extremely undesirable for selective calling receivers because it increases the size of the circuit structure and increases current consumption.

Recently, a method has been considered in which an inductance circuit is provided in parallel with the light emitting diode and the back electromotive force of the inductance circuit is used to drive the light emitting diode. FIG. 6 shows an example of the display circuit, in which an inductance circuit 11 is connected in parallel with the light emitting diode 9.
A transistor circuit 12 is connected between these parallel circuits and the ground terminal.
The switching operation is performed by a drive signal generated from a pulse drive signal generation circuit 13. In such a circuit, when a pulse drive signal AS as shown in FIG. 7 is supplied to the transistor circuit 12, this drive signal turns on (“H”).
transistor circuit 1 during the period when the level is
2 becomes conductive and the power supply current flows to the inductance circuit 11.
BS flows, which causes the inductance circuit 11
An energy E of LI ² /2 is accumulated in . Here, L is an inductance value, and I is a power supply current value.
On the other hand, when the above drive signal turns off (“L level”),
Since the power supply current is turned off, the inductance circuit 1
1 generates a back electromotive force, the potential of CS rises, and the light emitting diode 9 lights up. The lighting time of the light emitting diode 9 at this time (T1 in FIG. 7) is determined by the energy E stored in the inductance circuit 11.
is proportional to. Therefore, the light emitting diode 9 can be driven to light with a simple structure without increasing the power supply voltage.

[Problems with background technology]

However, in such a conventional circuit, sufficient brightness cannot be obtained because the lighting time of the light emitting diode 9 is short as shown by T1 in FIG. must be set to a large value. However, increasing the inductance value L in this manner has the disadvantage that the circuit becomes larger and more expensive. Furthermore, in the conventional circuit described above, a sound drive signal (generally an audible sound) is used as the drive signal AS regardless of the inductance value L, so a steady current flows through the inductance circuit 11 for a certain period of time. As a result, battery current is wasted, resulting in a shortened battery life.

[Purpose of invention]

The present invention is a selective call receiver that increases brightness without increasing the inductance value, provides clear visual display with a simple configuration, and reduces current consumption to extend battery life. The purpose is to provide

[Summary of the idea]

In order to achieve the above object, the present invention sets the drive signal frequency of the inductance circuit higher than the normal drive frequency, thereby speeding up the lighting cycle of the light emitting element and increasing the brightness. This is designed to shorten the time that the current flows.

[Example of idea]

FIG. 1 shows the configuration of a display circuit of a selective call receiver according to an embodiment of the present invention, and the same parts as in FIGS. 5 and 6 are given the same reference numerals and detailed explanations will be omitted.

The code matching circuit 40 includes a pulse drive signal generator for generating a drive signal DS for visual display, in addition to a pulse drive signal generator for generating a drive signal for sound. This pulse drive signal generator for visual display generates a pulse drive signal with a higher frequency (16KHz) than the drive signal for sound (audible sound). The period (H” level) is the energy storage period of the inductance circuit 11, that is, the current value after the current starts flowing through the inductance circuit 11 is the value Vcc/ defined by the power supply voltage Vcc and the DC resistance R of the inductance circuit 11. It is set to be approximately equal to the period T3 until reaching R.

With such a configuration, when a call occurs to its own receiver, the code matching circuit 40 generates a sound drive signal (BS in FIG. 7) and generates a sound from the speaker 7. At the same time, a drive signal for visual display (DS in FIG. 2) is generated and supplied to the transistor circuit 12. Then, the above drive signal
During the ON period (“H” level) of DS, the transistor conducts and current from the power supply (output voltage Vcc) flows through the inductance circuit 11 as shown in FIG. 2 ES.
As a result, electromagnetic energy (E=LI ² /2) is accumulated in the inductance circuit 11. In this state, when the drive signal DS turns off ("L" level), the current supplied to the inductance circuit 11 is instantly cut off at the moment it becomes "L" level. A back electromotive force is generated by the inductance, and as a result, the potential of FS becomes as shown in FIG. 2, and the light emitting diode 9 lights up. Similarly, the light emitting diode 9 is
The inductance circuit 11 is synchronized with the drive signal DS.
Lighting is performed every time a back electromotive force is generated. By the way, as described above, the frequency of the drive signal DS for visual display is set higher than the frequency of the drive signal AS for sound. Therefore, even if the brightness each time the light emitting diode 9 is turned on is the same as in the conventional case, the brightness increases because the number of times the light emitting diode 9 is turned on per certain period of time increases. Therefore, the occurrence of a call can be notified more clearly.

In addition, by setting the frequency of the drive signal DS high, unnecessary current supply after the current value flowing through the inductance circuit 11 reaches the steady value (Vcc/R) is reduced, which reduces power consumption during the calling operation. It is possible to extend the life of the battery by reducing the energy consumption. Moreover, in this case, in this embodiment, the drive signal DS
Since the frequency is set so that the on period is approximately equal to the energy storage period T3 of the inductance circuit 11, it is possible to reduce wasteful current consumption to approximately zero after the current value flowing through the inductance circuit 11 reaches a steady value. As a result, the light emitting diode 9 can be driven with the least current consumption. The shaded area in FIG. 2 ES indicates the amount of power consumed by the circuit of this embodiment. By the way,
The shaded part A in Fig. 7 BS is the drive signal AS for sound.
This is the amount of power consumed by a conventional circuit that drives lighting in synchronization with .

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the drive signal is
Although the pulse signal has a duty ratio of 50%, a signal having a duty ratio other than 50% may be used.
For example, paying attention to the fact that the period indicated by T2 in FIG. 2 is the non-lighting period of the light emitting diode 9, the frequency and duty ratio of the drive signal GS are changed as shown in FIG. 9 lighting operation period
It is also possible to set only T1 to be off ("L" level) and all other periods to be on ("H" level). When the inductance circuit 11 is driven using such a drive signal GS, the light emitting diode 9
The period when the is not lit is the energy storage period of the inductance circuit, and the drive signal is
During the ON period of GS, the current value flowing through the inductance circuit 11 is at the steady value (Vcc/
The period until R) is set to T3, and as a result, unnecessary current supply is not performed, as shown in Fig. 3.
As shown in the shaded area C of HS, the number of lighting drives of the light emitting diode 9 per unit time can be further increased while eliminating unnecessary power consumption. Further, in the above embodiment, a case where both a sound display and a visual display are used has been described, but the present invention may also be applied to a receiver having only a visual display function. Furthermore, the frequency of the drive signal may be set so that the on period is T3 or less, and other factors such as the frequency and duty ratio of the drive signal, the configuration of the inductance circuit and the configuration of its drive circuit, and the type of light emitting element, etc. Various modifications can be made without departing from the essential principles of the present invention.

[Effect of idea]

As described in detail above, the present invention has been developed by setting the drive signal frequency of the inductance circuit higher than the drive frequency of the speaker, thereby increasing brightness without increasing the inductance value. According to the present invention, it is possible to provide a selective call receiver that can provide a clear visual display and can reduce current consumption and extend battery life.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of a display circuit of a selective call receiver in one embodiment of the present invention, Fig. 2 is a signal waveform diagram used to explain the operation of the same circuit, and Fig. 3 is another embodiment of the present invention. 4th signal waveform diagram for explaining
7 to 7 are for explaining conventional selective call receivers, FIG. 4 is a circuit block diagram showing the configuration of a general selective call receiver, and FIG. 5 is a selective call receiver with a visual display function. FIG. 6 is a circuit diagram showing the structure of the display circuit of the receiver, FIG. 6 is a circuit diagram showing the structure of the light emitting diode drive circuit, and FIG. 7 is a signal waveform diagram used to explain the operation of the circuit. 9... Light emitting diode, 11... Inductance circuit, 12... Transistor circuit, 13... Pulse drive signal generation circuit, 40... Code matching circuit,
DS, GS...Drive signal for visual display, ES, HS...
...Current flowing in the inductance circuit, FS, IS...
...The anode side potential of the light emitting diode.

Claims (1)

[Claims for Utility Model Registration] (1) A light-emitting element having an operating voltage higher than a power supply voltage and a speaker, the light-emitting element being energized and driven by a back electromotive force of an inductance circuit to emit light;
As a result, in a selective calling receiver that performs a call using a visual display and generates a sound by energizing the speaker, the frequency of the drive signal of the inductance circuit is compared with the frequency of the drive signal of the speaker. A selective call receiver characterized by a high setting. (2) The on period of the inductance drive signal is the period until the current value flowing through the inductance circuit reaches a steady value defined by the power supply voltage value and the DC resistance of the inductance circuit, or a value close to this steady state. A selective calling receiver according to claim (1) of the utility model registration claim, which has a frequency set as follows. (3) The duty ratio of the drive signal for the inductance circuit is set so that the off period is approximately equal to the period during which the back electromotive force of the inductance circuit is greater than the operating voltage of the light emitting element. Selective calling receiver described in scope (1) or (2).