JPS581014Y2 - tv jiyeonji yuzouki - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a preheating circuit for a television receiver, particularly a cathode ray tube, and supplies an optimum preheating current to a cathode ray tube heater using a simple circuit configuration.

Generally, when preheating a cathode ray tube, the lifespan of the cathode ray tube heater is taken into consideration (that is, if the preheating current is too small, it will take a long time for the image to appear, rendering preheating meaningless.

On the other hand, if the preheating current is too large, the life of the cathode ray tube will be shortened.

), supplying a current of 60-70% of the rated current.

For this purpose, conventionally, a resistor was inserted into the circuit on the primary or secondary side of the heater transformer, and the voltage drop caused by this resistor was used to supply a current smaller than the rated current.

However, since the above-mentioned means utilizes the voltage drop across the resistor, there is a drawback that heat loss is high and a heating element is present during preheating.

The present invention attempts to eliminate the above-mentioned conventional drawbacks.

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

In Fig. 1, 1 is a heater transformer, and -order coil 1
Connect one end of a to the AC power input terminal, and connect the secondary coil 1b.
One end of the heater 3 is connected to one end of the secondary coil 1.
The other ends of a and lb are connected to each other.

2 is a diode whose cathode is connected to the common terminal of the primary and secondary sides of the heater transformer 1, and whose anode is connected to the heater transformer 3.
It is connected to the AC power input terminal along with the other end.

4 is a switch inserted in parallel with diode 2.

Next, its operation will be explained.

In FIG. 1, switch 4 is open during preheating.

Here, the equivalent circuit when the polarity of the AC power source is positive is as shown in FIG. 2a.

At this point, almost the entire voltage of the AC power source is applied to the primary coil 1a of the heater transformer 1, so that the heater current becomes approximately 10 mA.

On the other hand, when the polarity of the AC power supply is negative, the circuit in Figure 1 becomes as shown in Figure 2. At this time, the diode 2 is turned on, so the common terminal on the primary and secondary sides of the heater transformer 1 is connected. A short circuit is established between the heater 3 and the heater 3, and a current corresponding to the AC power supply voltage flows through the heater 3 from the secondary coil 16.

This current waveform is shown in FIG. Note that FIG. 3a shows an AC power supply voltage waveform.

As a result, according to this embodiment, the current required for preheating (
60 to 70 times the rated current) can be sufficiently supplied to the heater 3.

The preheat circuit is released.

During normal operation of the so-called heater circuit, the switch 4 shown in Figure 1 is closed, so the operating circuit becomes as shown in Figure 2 regardless of the polarity of the AC power supply, and the required voltage is always applied to the secondary side through the heater transformer 1. The AC heater current is taken out to the coil 1b and supplied to the heater 3.

In addition, there was a conventional method for supplying preheating current by inserting a parallel circuit of a diode and switch 4 in series with the heater, but with this method, only 50% of the rated current could be supplied to the heater during preheating. Rated current of 60
The capacity is insufficient for a preheating current that requires ~70%.

As explained above, according to the present invention, by inserting a parallel circuit of a diode and a switch between the common terminal where one end of the primary coil and one end of the secondary coil of the heater transformer are connected to each other and one end of the heater, During preheating, a current of 60 to 70% of the rated current can be efficiently supplied to the heater.

It is extremely effective in practice.

[Brief explanation of drawings]

Fig. 1 is a main part wiring diagram of a television receiver according to an embodiment of the present invention, Fig. 2 a and b are circuit diagrams for explaining its operation, and Fig. 3 a and b are AC power supply voltage and preheating current. FIG. 1... Heater transformer, 2... Diode, 3... Heater, 4... Switch.

Claims (1)

[Scope of utility model registration request] One end of the primary coil of the heater transformer is connected to one end of an AC power input terminal, one end of the secondary coil is connected to one end of a cathode ray tube heater, and the other ends of the secondary coil and the secondary coil are connected to each other to form a common terminal. , one end of a diode is connected to the common terminal, the other end of the diode is connected to the other end of the AC power input terminal along with the other end of the cathode ray tube heater, and a switch is connected in parallel to the diode. Machine.