JPS5814088B2 - Hiyojisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device that is effective for use in a broadcast receiver that has a built-in electronic tuning tuner that uses a variable capacitance diode as a tuning element and sweeps the voltage applied to the variable capacitance diode. .

As the display device of the receiver, a meter display consisting of a voltmeter or the like may be considered, but such a meter display device has problems in terms of response speed and design, and has the disadvantage of being significantly inferior in reliability against external vibrations. There is, and it is not preferable.

The present invention proposes a display device devised to eliminate these drawbacks.

That is, the present invention divides the reception frequency band into a plurality of ranges, provides a light emitting element corresponding to each broadcast frequency, and displays the received broadcast frequency by lighting the light emitting element. a reference voltage predetermined in advance and a sweep voltage applied to a tuning varicap diode of a tuner for tuning, and when the two voltages substantially match, the light emitting element lights up. This paper proposes a device.

The present invention will be described in detail below according to embodiments shown in the drawings.

Figures 1 and 2 show the tuning display section of a radio receiver and a television receiver, respectively, and as can be seen, the receiving frequency bands (AM, FM, VHF,
UHF) is divided into a plurality of parts, and one light emitting element A, B, . . . , F is arranged in each divided range.

The divided ranges are A'' and B, respectively, as shown in Figure 3.
″, ..., r.

As shown in the characteristic diagram of the electronically tuned tuner in Fig. 3, in this device, the divided ranges are equally spaced, the center frequencies of each range are set as A', B', ..., F', and these center frequencies are given. Let the DC voltages be a, b..., f.

Incidentally, in the apparatus of the present invention, these DC voltages are set in advance as reference values according to each center frequency.

The voltages a, b, . . . , f are also divided into ranges a′b′, .

FIG. 4 is a circuit diagram implementing the present invention, Tr,,T
r2 is a transistor constituting a differential amplification type comparator 1, the base of one transistor Tr1 is supplied with the predetermined reference voltage (for example, a) via a resistor 2, and the base of the other transistor Tr2 is supplied with the predetermined reference voltage (for example, a). A sweep voltage is applied through the resistor 3. Although FIG. 4 only shows the circuit corresponding to one of the six divided ranges, A'', a', In reality, five circuits almost identical to this are further arranged in parallel.

It should be understood that although the reference voltage input to each circuit is given a voltage of a different set value, the sweep voltage is commonly applied to each circuit.

It is preferable that the pace resistors 2 and 3 have a resistance of 100 kΩ or more in order to eliminate the influence of the reference voltage and sweep voltage on the supply source circuit.

In FIG. 4, DIlD2+D3+D4 is the output of the comparator 1, that is, the first output appearing at the collector K1 of the transistor Tr1 and the collector K2 of the transistor Tr2.
This diode is inserted to adjust the direction of the voltage so that the transistor Tr3 in the next stage is always forward-biased regardless of the magnitude relationship with the second output appearing in the second output.

The switching transistor Tr3 is a switching transistor that is turned on when the voltage level is higher than the voltage level L shown in FIG. 5, and turned off when the voltage level is lower than the voltage level L shown in FIG.

At the same time, this transistor T,3 also performs the function of converting the output of the comparator 1 floating from ground into a voltage relative to the ground voltage.

Then, the diode DltD2+D3tD4 and the transistor Tr3 determine whether the sweep voltage is within a predetermined range that includes a point that matches the reference voltage of each divided range, that is, whether the sweep voltage and the reference voltage of each divided range substantially match. It constitutes a detection circuit for detection.

Tr4 and Tr5 are transistors forming a Schmitt circuit 4 that operates as a switching circuit for controlling light-emitting element blinking, and a light-emitting element (light-emitting diode) 5 is connected to the collector of one of the transistors Tr5 as a load.

VCC indicates DC bias power supply voltage. Next, the operation of the display circuit shown in FIG. 4 will be explained.

First, a predetermined reference voltage is applied to the base of the transistor Tr1 constituting the comparator 1, and a sweep voltage for channel selection (which increases or decreases linearly with time) is applied to the base of the other transistor Tr2. Since a direct current voltage (DC voltage) is given, the output voltage appearing at the collectors of the transistors Tr, Tr2 is also set depending on the magnitude of these two voltages.

Now, considering the case where the reference voltage is larger than the sweep voltage,
The potential of the collector K2 of the transistor Tr2 becomes higher than the potential of the collector K1 of the transistor Trl, and K2→
A forward bias is applied between the emitter and base of the switching transistor Tr3 through the loop of diode D3 → emitter E of transistor Tr3 → base B8 → diode D2 → K1, and transistor Tr3 is turned on.
As a result, its collector potential increases.

As a result, one transistor Tr4 constituting the Schmitt circuit 4 becomes conductive, and the other transistor Tr5 becomes non-conductive.

Therefore, the light emitting diode 5 does not light up.

However, when the sweep voltage gradually increases and reaches a point near the reference voltage, that is, point V1 in FIG. The voltage between the emitter and the base of the transistor Tr3 also decreases, and a sufficient bias is no longer applied to operate the transistor Tr3, so the transistor Tr3 becomes non-conductive.

As a result, the collector of the transistor Tr3 falls to the ground potential, so the transistor Tr4 constituting the Schmitt circuit 4 becomes non-conductive, the transistor Tr5 becomes conductive, and the light emitting diode 5 lights up.

The range in which the light emitting diode lights up in this way is determined to be the range from V to v3, which includes the point V2 where the sweep voltage and the reference voltage match, as shown in FIG.

When the sweep voltage exceeds V3, the difference between the sweep voltage and the reference voltage becomes large, and accordingly the switching transistor T
Since the bias voltage of r3 increases, the light emitting diode 5 is turned off again.

That is, when the output terminal K1 of the comparator 1 has a higher voltage than K2, a sufficiently large forward voltage is applied to the switching transistor Tr3 through the path K1 → diode D1 → emitter E of the transistor Tr3 → base B8 → diode D4 → K2. This is because a bias is applied, and in response to the ON of the transistor Tr3, the transistor Tr4 is turned on, and the transistor Tr5 is turned off, so that no current flows to the light emitting element 5.

In addition, in FIG. 5, the potential between the emitter and the base of transistor Tr3 is not negative at the point where the sweep voltage is V2 or less, but this is due to the diode inserted between comparator 1 and transistor Tr3 as mentioned earlier. DI+D2+D3+
This is due to the action of D4.

FIG. 6 shows an embodiment in which the comparator 1 in FIG. 5 is omitted and a transistor Tr6 is connected in place of the Schmitt circuit 40.

In this embodiment, the reference voltage and the sweep voltage are directly applied to the diodes D1, D2, D3+D4, so the supply sources of both voltages must have low impedance. When the switching transistor Tr3 is turned on, it becomes conductive and the collector potential drops to the ground potential, so no current flows through the light emitting diode 5. .

In this embodiment, the switching operation becomes slower and the detection sensitivity is lowered, but there is no problem in practical use.

In the above explanation, as shown in FIG. 7A, the sweep voltages are a',
When the voltage range is within one of the voltage ranges b',...f', only the light emitting element provided corresponding to that voltage range lights up, but by appropriately setting the circuit constants, the seventh As shown in the figure, if adjacent voltage ranges of a'', b'', ..., f'' are set to overlap, when the sweep voltage reaches the overlapping voltage range, two adjacent light emitting diodes lights up.

That is, as the sweep voltage gradually increases, the light emitting element changes from A→
The lights are lit in the order of A, B→B→B, C→C→...E, F→F《.

In this way, it is possible to make judgments in a frequency range that is about twice as large as the number of light emitting elements, so the number of light emitting diodes and their associated circuits can be reduced.

Since the display device of the present invention is an electronic display using light emitting elements, there is no risk of being affected by external vibrations unlike the conventional display device using a meter.

Furthermore, in the present invention, a reference voltage is set in advance for each broadcast channel, and when the sweep voltage for tuning reaches this reference voltage or its vicinity, the light emitting diode for tuning indication is turned on. This has the effect that synchronized display can be performed very suitably.

Furthermore, the reliability is very high, and the present invention is extremely useful.

Furthermore, in the display device of the present invention, two adjacent light emitting elements are turned on when the sweep voltage reaches an overlapping voltage range, so that it is possible to discriminate a frequency range that is approximately twice as many as the number of light emitting elements. In other words, the resolution of the received frequency display can be approximately doubled.

Therefore, the number of light emitting elements and circuits attached thereto can be reduced, and the space for installing them can also be reduced.

[Brief explanation of the drawing]

The drawings all relate to the display device of the present invention, and FIGS. 1 and 2 are schematic front views of the display device in use. FIG. 3 is an explanatory diagram. FIG. 4 is a partial circuit diagram of the display device, and FIG. 5 is an explanatory diagram of its operation. FIG. 6 is a circuit diagram of another embodiment. FIG. 7 is a diagram for explaining a second display device of the present invention. 1... Comparator, 4... Schmitt circuit, 5... Light emitting element.

Claims (1)

[Claims] 1. A display device for a broadcast receiver, which divides the received frequency band into a plurality of ranges, provides a light emitting element corresponding to each divided range, and displays the received broadcast frequency by lighting the light emitting element. in which the reference voltage ranges defined for each divided range of the receiving frequency band are set so that they partially overlap in adjacent ranges,
A sweep voltage applied to a tuning varicap diode of a tuner for tuning is compared with the reference voltage range, and whether the sweep voltage is within a predetermined reference voltage range of the reference voltage ranges of each divided range. A comparison detection means for detecting whether the sweep voltage is within the predetermined reference voltage range is provided for each divided range of the receiving frequency band, and when the comparison detection means detects that the sweep voltage is within the predetermined reference voltage range, the predetermined reference voltage is determined. A display device characterized in that light emitting elements in a divided range corresponding to a voltage range are turned on, and when the sweep voltage is within the overlapping range, adjacent light emitting elements related to the range are turned on.