JPS6157737B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a tuning voltage of an electronic tuner using a variable capacitance diode to tune its tuning channel,
and frequency etc. are displayed on the meter, and the TV,
This relates to a meter drive circuit that digitally controls so that the tuning status of multiple bands such as FM and AM can be displayed on a single meter.

When trying to display the tuning point of an electronic tuner using a conventional variable capacitance diode on a meter using its tuning voltage, the VHF
Low Band VHF High Band, UHF Band, and more
When adding FM, AM, etc., the points covered by the tuning points in each band have different tuning voltages, so a meter is required for each band, or a single meter can be used to tune each band. In order to indicate a point, a plurality of changeover switches are required, and the operation is complicated.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a meter drive circuit that can display the tuning point of each band on one meter and adjust the meter with simple operations.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the basic circuit of the present invention. 1 is a variable DC voltage generator, 2 is a differential amplifier using a DC amplifier that receives the DC voltage (hereinafter referred to as Es) output from the DC voltage generator 1, and 3 is the output of the differential amplifier 2. A meter has one end connected to a terminal and the other end connected to a variable resistor described later. 4 is a variable resistor connected to the meter 3.

In Figure 1, the meter drive voltage (hereinafter referred to as Ein) is the voltage for driving meter 3.
is applied to the other input terminal of the differential amplifier 2 to which Es is connected, then the output voltage of the differential amplifier 2 (hereinafter referred to as E ₀ ) is given by the following equation.

Eo=Rb(Ein-Es)/Ra...Equation 1 As shown above, when Ein (=tuning voltage) is the voltage at the point where meter 3 starts to swing, adjust Es so that Ein=Es. No current flows through Eo, and Eo is at ground potential at this time, so it is not affected by the state of the variable resistor 4. As described above, it can be seen that by using a differential amplifier, the point at which the meter 3 starts to swing can be shifted.

Next, input the voltage that will cause the meter 3 to swing to the maximum as Ein, and at this time, the Eo output from the differential amplifier 2 and the current flowing through the meter 3 are as follows. However, the current flowing through the meter is Io, and the variable resistance If the resistance value of the meter 4 is Ro, then Io=Eo/Ro...Formula 2 From the above equation 2, Eo that satisfies equation 1 is output from the differential amplifier 2 by the voltage Ein to make the meter 3 swing to the maximum. At this time, by adjusting the variable resistor 4, the current gain flowing through the meter 3 can be varied, and it can be seen that it can be adjusted to the point where the meter 3 swings to its maximum.Also, at this time, from the above, it will affect the point at which the meter 3 starts swinging. I don't.

From the above, the shift amount is controlled with Es and meter 3
Measure the point at which the meter starts to swing using the variable resistor 4.
It can be seen that the point at which the meter 3 swings to its maximum can be set by controlling the current gain flowing through the meter. Also, first enter the Ein of the point where meter 3 starts swinging, then input the Ein of the point where meter 3 starts swinging, then input the Ein of the point where meter 3 swings maximum, and adjust the point where meter 3 swings maximum. By doing so, adjustments can be made easily without having to do with each other.

Next, based on the basic circuit shown in FIG. 1, an example of FIG. A D-A converter in place of the variable DC voltage generator 1 in FIG. 1, 6 a differential amplifier, 7 a meter, 8 a ladder resistor in place of the variable resistor in FIG. 1, and an electronic switch,
A digital variable resistor 9 whose impedance can be digitally controlled includes a microcomputer for digitally controlling the D-A converter 5 and the digital variable resistor 8;
The converter 5 and the digital variable resistor 8 are varied;
A control circuit each equipped with an UP and DOWN switch for adjusting the meter 7 according to the meter drive voltage Ein, and a meter drive circuit 10 that transmits the data set in the D-A converter 5 and the digital variable resistor 8. This is a non-volatile memory that retains information even when the power is turned off.

In Figure 2, the TV's VHF Low Band,
VHF High Band, UHF Band, FM and AM
When the voltage Ein from the tuning voltage generator 11 is switched to the Band, the control circuit 9 is switched for each Band.
By drawing data from the non-volatile memory 10 and setting the meter 7 to a state where it can be adjusted by Ein for each band, the channel displayed on the meter 7, initially adjusted to the characteristics of each band, Alternatively, by adjusting the frequency to match the frequency, the adjusted data of the D-A converter 5 and the data of the digital variable resistor 8 are stored in the non-volatile memory 10, and the power to the meter drive circuit is then turned off. Since the data is retained even when the data is adjusted, the control circuit 9 always works to output data adjusted for each band, so that the display on the meter 7 and the tuning point of the electronic tuner match for each band. Furthermore, even if the electronic tuner or the like changes, data settings and adjustments are easy.

From the above, the meter drive circuit described above allows you to easily adjust the tuning point and make adjustments when changes are made in each band of the electronic tuner, and it also shows the tuning points of more bands on the meter. In this case, it is only necessary to expand the non-volatile memory, making it extremely simple.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the basic circuit configuration of the present invention, FIG. 2 is a block diagram showing an embodiment of the invention, and FIG. 3 is an embodiment of a meter display. In the figure, 1 is a variable DC voltage generator, 2 is a differential amplifier, 3 is a meter, 4 is a variable resistor, and 5 is a D-A
Converter, 6 is differential amplifier, 7 is meter, 8
9 is a control circuit consisting of a microcomputer and an adjustment switch; 10 is a digital variable resistor;
is a non-volatile memory, 11 is a tuning voltage generator, 1
2 is an electronic tuner.

Claims (1)

[Claims] 1 A D-A converter, a differential amplifier having one end of its input as the output of the D-A converter, a meter having one end connected to the output of the differential amplifier, and a ladder resistor connected to the other end of the meter. and a control circuit consisting of a digital variable resistor which is mainly composed of an electronic switch and whose impedance can be digitally varied, a microcomputer for controlling the D-A converter and the digital variable resistor, The differential amplifier is configured with a non-volatile memory capable of non-volatilely storing the control value of the variable resistor, and is supplied to the electronic tuner at the other input terminal of the differential amplifier, one input terminal of which is connected to the D-A converter. The tuning voltage is input, and the meter displays the TV channel, FM frequency, AM frequency, etc. Even if the tuning voltage point changes for each band, the D-A converter and the digital A meter drive circuit characterized by controlling a variable resistor so that the meter display matches the pointer.