JPS6110397Y2 - - Google Patents

Description

[Detailed description of the invention] Conventionally, an automatic degaussing circuit as shown in FIG. A device in which a fixed resistor Rs is connected to the connection point of the control element 2) and a degaussing coil Rd is connected in series with the control element 2 is known. In other words, the sudden resistance change temperature of the control element 2 is set lower than that of the heating element 1, and after the control element 2 once controls the current flowing to the degaussing coil Rd, the heating element 1 controls the control element 2. The idea was to heat it up further and make the control current smaller. 3 is a power supply, and 4 is a power switch. However, in this conventional device, the temperature at which the resistance of the control element 2 suddenly changes is set lower than that of the heating element 1, so if the resistance of the control element 2 exceeds the sudden resistance change point and becomes high, Most of the power supply voltage is applied across itself and the fixed resistor Rs, so this fixed resistor Rs
The control element 2 requires a high-power element, and the control element 2 requires an element with high withstand voltage, which naturally has the drawbacks that the outer diameter of the element becomes large, and the element is of high quality and expensive.

The present invention has been developed in view of the above-mentioned drawbacks of the conventional technology, and is characterized in that the temperature at which the resistance suddenly changes of the positive temperature coefficient thermistor connected in series with the degaussing coil is higher than that of the other. . In other words, the automatic degaussing circuit of the present invention has a first
A fixed resistor Rs is connected in parallel to the series circuit of the positive characteristic thermistor _R1 and the degaussing coil Rd, a second positive characteristic thermistor _R2 is connected in series to this parallel circuit, and the first and second Positive characteristic thermistor
While R ₁ and R ₂ are thermally coupled to each other, the first
The sudden resistance change temperature of the second positive temperature coefficient thermistor _R1 is set higher than that of the second positive coefficient thermistor _R2 , as shown in the third diagram. In FIG. 2, 3 is a power source, and 4 is a power switch.

Next, the specific operation of the present invention will be explained.

First, when the power switch 4 is turned on, a large amount of current flows through the degaussing coil Rd because the resistance values of both positive temperature coefficient thermistors R ₁ and R ₂ are low. After a certain period of time, the second positive temperature coefficient thermistor R ₂ reaches its resistance sudden change temperature and causes its resistance value to rapidly increase. This increases the voltage across the terminals, reduces the voltage applied to the parallel circuit of the fixed resistor Rs, the first positive temperature coefficient thermistor _R1 , and the demagnetizing coil Rd, and limits the current flowing through the demagnetizing coil Rd. After another certain period of time has elapsed, the first positive temperature coefficient thermistor _R1 reaches its resistance sudden change temperature, rapidly increases its resistance value, controls the current flowing through the demagnetizing coil Rd, and completes demagnetization. In this case, although the second positive temperature coefficient thermistor R ₂ is thermally coupled to the first positive coefficient thermistor R ₁ , unlike the conventional type, the effect of heating the control element with the heating element is insufficient, so Rd Although the current flowing through the magnet is slightly higher than that of the conventional type as long as elements of the same size are used, the result is still within a sufficient value to satisfy the demagnetizing effect and is of no practical use.

As described above, in the present invention, the resistance sudden change temperature of the second PTC thermistor is set lower than that of the first PTC thermistor, so if the second PTC thermistor becomes high in resistance first, Only a small voltage is applied to the first positive temperature coefficient thermistor and the fixed resistor, and they do not require expensive high-voltage and high-power elements, making them inexpensive. In addition, in this invention,
Since a high-voltage thermistor is not particularly required as the first positive temperature coefficient thermistor, it becomes possible to use one with a smaller initial resistance, and the demagnetizing effect is also excellent. In other words, the demagnetization effect requires that the difference between the initial current value and the stable current value be as large as possible. Furthermore, since the present invention does not require high-quality elements as in the prior art, it has the effect of improving the yield during manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a conventional automatic degaussing circuit, FIG. 2 is a diagram of an automatic degaussing circuit of the present invention, and FIG. 3 is a resistance temperature characteristic diagram of a positive temperature coefficient thermistor used in the present invention.

Claims (1)

[Scope of utility model registration request] A fixed resistor is connected in parallel to the series circuit of the first positive temperature coefficient thermistor and the degaussing coil, a second positive coefficient thermistor is connected in series to this parallel circuit, and the first and second positive coefficient thermistors are connected in parallel. An automatic degaussing circuit characterized in that the first positive temperature coefficient thermistor is thermally coupled to each other and the resistance sudden change temperature of the first positive coefficient thermistor is higher than that of the second positive coefficient thermistor.