JPS587711Y2 - Channel display circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a channel display circuit for a television receiver or the like, and particularly to a channel display circuit using a neon tube.

Conventionally, this type of channel display circuit has been provided with a circuit for preventing neon tubes of unnecessary channels from lighting up, as shown in FIG. 1, for example.

That is, in Fig. 1, ■R1, vR2...VR,
is a variable resistor for setting the tuning voltage of each channel, SW work, S
W2...SWo is the channel selection switch for each channel, N1. N2...No is a neon tube for channel display, and Ql is a transistor for extinguishing the neon tube.
R1 and R2 are voltage dividing resistors.

Note that the above channel selection switch SW1. SW2...SW
o is shown here as a mechanical on/off switch configuration for convenience to simplify the operation explanation, but normally the channel selection switches SW1. SW2...The main part of SWo is configured as an electrical switching circuit using an integrated circuit.

When the tuning switch SW1 is in the on state, the tuning voltage preset by the variable resistor VR1 is supplied to the tuner, the channel corresponding to this tuning voltage is in the receiving state, and at this time the neon tube N1 is in the on state. It turns on and lights up, indicating this receiving channel.

In this state, if another tuning switch, for example SW2, is turned on, the tuning switch SW1 is returned to the OFF state, and a positive tuning pulse (this includes the AFT (defeat pulse is used) is applied, which causes transistor Q
1 is temporarily turned on and its collector potential is lowered, so that the neon tube N1 is extinguished.

On the other hand, at this time, the tuning voltage set by the variable resistor vR2 is supplied to the tuner, and at the same time the transistor Q1 is turned off, the neon tube N2 is turned on.

In this way, the channel selection switch SW1. SW2...SW
Each time o is turned on, the neon tube extinguishing transistor Q1 is temporarily turned on, and the neon tubes N i , N 2 , N, which had been lit until then are once extinguished, and then Newly selected neon tube N1. N2...
. . No is lit, and the tuning voltage set in advance by the tuning voltage setting variable resistors VR1, VR2, . . . VR is supplied to the tuner, and the desired channel is received.

By the way, in the conventional channel display circuit as mentioned above,
Neon tube for channel display N1. N2...N,
In order to drive the lighting, the power supply voltage 1B1 is designed to be higher than the discharge starting voltage of the neon tube, for example, about 110V. A high voltage higher than the discharge starting voltage of the neon tube is applied to the collector of the transistor Q1.

A transistor with an EO of 110 V or higher is required.

Note that the power supply voltage 1B2 is designed to be as low as about 30V.

In addition, in the above circuit, it is often designed in advance so that a specific channel selection switch, for example, SWl, is preferentially turned on immediately after the power switch is turned on, but in this case, the rise of the power supply voltage terminal B1 is If it is faster than the power supply voltage terminal B2, there is a drawback that the neon tubes N, N2, . . .

The present invention was devised in view of the drawbacks of the conventional circuit, and provides a channel display circuit that does not require the use of a transistor with a very high withstand voltage as a neon lamp extinguishing transistor, and that does not malfunction immediately after the power is turned on. be.

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

FIG. 2 shows one embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

In particular, instead of the voltage dividing resistor R2 shown in FIG. 1, a constant voltage diode D1 such as a Zener diode is inserted in series with the collector-emitter current path of the neon lamp extinguishing transistor Q1. A capacitor C1 is inserted in parallel.

In this case, the channel selection switch SW1. SW2...S
When one of Wn, for example, switch SW2, is turned on, a tuning pulse is applied to the base of the neon tube arc-extinguishing transistor Q, and the transistor Q1 and constant voltage diode D1 are constantly turned on until then. Each neon tube Nl, including the neon tube that was lit.

N2...No are extinguished all at once, and then the transistor Q1 is cut off and at the same time the neon tube N2 is turned on and lit.

At this time, the tuning voltage set by the variable resistor vR2 is supplied to the tuner.

In this way, when the neon lamp extinguishing transistor Q1 transitions from the on state to the off state, the discharge starting voltage of the neon lamp is applied to the cathode of the constant voltage diode D1, but in this case, the collector of the neon lamp extinguishing transistor Q1 A voltage obtained by subtracting the voltage drop of the diode D1 from this discharge starting voltage is applied between the emitters, and therefore the transistor Q1 has a voltage of (1).

A relatively small EO can be used.

For example, even if 110V is used as the power supply voltage element B1, the Zener voltage is 60V as the constant voltage diode D1.
If a Zener diode with a voltage of V is used, the transistor Q1 will have a voltage of V.

It is also possible to use a transistor with an EO of 50V or less.

Also, immediately after turning on the power switch, even if the power supply voltage terminal B
Even if 1 rises earlier than 10B2, the capacitor C1 is charged via the resistor R□ and the diode D1, so the neon tubes N, N2...Nn have some The power supply voltage B is applied with a delay, so that the neon tubes N□, N2, . . . , Nn are not erroneously turned on.

According to the channel display circuit of the present invention, when channel display is performed using neon tubes, the current path is set in series with the collector-emitter current path of the neon tube extinguishing transistor that reliably extinguishes unnecessary neon tubes. By simply inserting a voltage diode and a capacitor in parallel on the same current path, not only can incorrect channel display be prevented immediately after the power is turned on, but it is also extremely inexpensive as there is no need to use high voltage transistors and capacitors. Can be configured.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional channel display circuit;
The figure is a circuit configuration diagram of one embodiment of the present invention. SW1~SWn・・・Tuition selection switch, ■R1~V
Ro: variable resistor for tuning voltage setting, N1 to N,
...Neon tube for channel display, Ql...
... Neon tube arc extinguishing transistor, Dl ... Constant voltage diode, C1 ... Condenser.

Claims (1)

[Scope of utility model registration request] In a channel display circuit using a neon tube, a constant voltage diode is inserted in series with the collector-emitter current path of a neon tube arc-extinguishing transistor, and a capacitor is inserted in parallel with the collector-emitter current path. .