JPS5847442Y2 - temperature control device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a device that controls temperature by controlling the amount of current applied to a load using a thyristor such as an SCR, and particularly relates to a control device that generates little noise.

For example, a conventional temperature control device for an electric blanket is constituted by a circuit as shown in FIG.

In this circuit, 1, 1 is the terminal of the AC power supply, 2 is the 5C
R13 is a main heater, 4 is a variable resistor for temperature adjustment, 5 is a detection signal line wound around the outer periphery of the main heater 3 via a heat-sensitive layer 6 with a negative temperature coefficient of resistance, T is a neon lamp, and 8 is a capacitor. , 9 are choke coils, and the capacitor 8 and choke coil 9 are filters for noise prevention.

As is well known, in this circuit, when the power supply voltage is applied, the resistor 4
A voltage is applied to the neon lamp 7 via the signal line 5, and when this applied voltage exceeds the discharge voltage of the neon lamp 7, a gate current is supplied to 5CR2 to turn on 5CR2.

Therefore, the main heater 3 is energized and generates heat.

When the power supply is in the negative half cycle, 5CR2 is turned off,
The operation is performed in the next positive half cycle.

As the temperature rises, the resistance value of the heat-sensitive layer 6 decreases, which causes a leakage current to flow from the signal line 5 to the main heater 3 through the heat-sensitive layer 6, so that the partial voltage applied to the neon lamp 1 decreases. , Therefore, the phase of the discharge start point of the neon lamp 1 is delayed, and the phase angle at which 5CR2 is turned on is reduced.
The temperature is controlled by reducing the amount of electricity supplied to the main heater 3.

As described above, this type of conventional temperature control device controls the phase at which the SCR is turned on, so the current waveform flowing through the SCR and the load has a strong pulse nature, which may generate a lot of strong noise. There are many.

Although a capacitor 8 and a choke coil 9 are connected to prevent or reduce this, it is not only impossible to completely prevent this, but also causes a large power loss.

The present invention aims to solve the above-mentioned problems of the conventional device, and controls the SCR using a zero voltage control method.

FIG. 2 shows a circuit diagram of one embodiment of the device of the present invention, and FIG. 3 shows a time chart explaining the operation of each part of FIG.

This example is implemented in an electric blanket temperature control device, and the SC
Constructed using R.

In FIG. 2, reference numerals 11 and 11' indicate AC power terminals of the temperature control device, and a power switch, fuse, etc. are connected to the front stage of the AC power terminals.

Main heater 12 and controlled 5CR1 between terminals 11 and 11'
3 are connected in series, and the terminal 11 and the main heater 12 are connected in series.
A series circuit of high resistance 14 and 5CRI 5, which constitutes a control circuit, is connected between the connection point of 5CR13 and 5CR13.

A series circuit of a temperature adjusting variable resistor 16, a signal line 17, a diode 18, and a neon lamp 19 is connected between the power supply terminal 11 and the gate electrode of the 5CR 15.

As shown in FIG. 4, the signal line 17 is wound around the main heater line 12 via a heat-sensitive layer 20 having a negative temperature coefficient of resistance, and is embedded in an electric blanket or the like to be used as a heat generating line.

The heat-sensitive layer 20 is made of an organic material such as polyamide resin or an inorganic material such as glass fiber or a thermistor, and increases the capacitance as the temperature rises, that is, reduces the impedance and prevents leakage between the signal line 17 and the main heating line 12. Increase current.

Further, the diode 18 is made to match the polarity at which the 5CR15 is turned on, so that the neon lamp 19 discharges only when the polarity is set.

A bypass circuit formed by connecting a diode 21 and a capacitor 22 in series, arranged in the same direction as the 5CR 15, is connected between both ends of the resistor 15.

And the diode 21 and capacitor 22 of the bypass circuit
Diode 23 is connected from the connection point to the gate electrode of 5DR13.
Connect.

Therefore, when an AC power supply voltage is applied between the terminals 11 and 11', the temperature of the main heater 12 is low and the impedance of the heat-sensitive layer 20 is high.

) The gate current of the SCR 15 flows through the resistor 16, the signal line 17, the diode 18, and the neon lamp 19.

Of course, the gate current is generated when the AC power source matches the polarity of the diode 18 and when a voltage higher than the discharge starting voltage of the neon lamp 19 is applied.

This is shown in Figures 3a and b.

FIG. 3a shows the waveform of the AC power supply voltage, and FIG. 3 shows the voltage waveform applied between both ends of the neon lamp 19.
It shows that when the AC power reaches its maximum positive value point, the neon lamp discharges and the voltage across it becomes almost zero potential.

This gate current turns on the 5CR15, producing a voltage drop across the resistor 140 as shown in FIG. 3C.

The resistor 14 is selected to have a sufficiently high resistance, thereby reducing the current value when the 5CR15 is on and increasing the voltage drop across the resistor 14.

That is, the current when the 5CR15 is turned on is not used to generate heat as a main heater.

When a voltage drop occurs across the resistor 14, the capacitor 22 is charged through the diode 21 of the bypass circuit.

This charging voltage is approximately equal to the voltage drop across the resistor 14.

When the AC power supply enters a negative half cycle, the gate current is blocked by the diode 18 and the KSCR 15 is also turned off.

Therefore, the voltage drop across the resistor 14 is eliminated, and the capacitor 22
will no longer be charged.

Instead, the capacitor 22 is a diode 23.5CR13,
A discharge occurs in the circuit passing through the resistor 14.

This discharge current supplies the gate current of 5CR13, turning on 5CR13.

The voltage change across capacitor 22 due to charging and discharging is shown in FIG. 3d.

When 5CR13 is turned on, a negative half-cycle voltage is applied to the main heater 12 as shown in FIG. 3e, and it generates heat.

In the next positive cycle, 5CR15 is turned on and the capacitor 22 is charged as described above.

After that, the above operation is repeated, and the main heater generates heat in the negative half cycle.

When the main heater reaches a certain temperature due to heat generation, at t2, the leakage current passing through the heat sensitive layer 20 increases and the voltage applied to the neon lamp 19 becomes lower than the discharge starting voltage.

Therefore, 5CR15 is not turned on and capacitor 22 is not charged, so that no gate current is supplied to 5CR13 and 5CR13 is not turned on.

When the temperature decreases, at t3, the operation as described at the beginning is performed again, and the main heater 12 generates heat.

The above operations are repeated to control the temperature within a certain range.

As described above, the present invention controls the charging current of the capacitor 22 that stores the gate current using the temperature detection part consisting of the signal line 17, and uses the charged charge of the capacitor 22 to control the charging current of the capacitor 22.
The main heater 12
The current flowing through is temperature controlled by turning the negative half cycle on or off.

Therefore, compared to the conventional phase control method that controls the conduction angle of the SCR, there is almost no pulse property, and therefore almost no noise is generated.

Therefore, there is no need for a noise prevention filter as in the past.

In addition, in the present invention, the voltage across the neon lamp 19 (
The gate current of SCR15) and the voltage across resistor 14 are
As shown in the figure, although the waveforms have strong pulse characteristics, their current values are very small and do not cause any problem as noise.

Furthermore, in the present invention, when the switching element operates, a large current flows through the bypass circuit using the diode 21 to charge the capacitor 22, so the resistor 14 connected in series with the switching element must be selected to have a very high resistance. As a result, it is possible to use a switching element with a small capacity, and the thyristor 13 can be operated reliably with a small capacity capacitor 22, which allows the use of a small capacity capacitor and reduces the cost of the temperature control device. can be measured.

Furthermore, in the present invention, the on/off of 5CRI 3 is controlled in the next half cycle after the switching element is on/off controlled, so that control is quickly performed in response to temperature changes, temperature control is performed accurately, and in the case of an electric blanket. can increase safety.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional temperature control device, Fig. 2 is a circuit diagram of an embodiment of a temperature control device according to the present invention, and Fig. 3 is a circuit diagram of a conventional temperature control device.
The time chart of each part in the figure, and FIG. 4 shows a structural diagram of the heating line. In the figure, 12 is the main heater, 13 is the SCR, 14 is the resistor, 1
5 is SCR, 17 is signal line, 19 is neon lamp, 20
is a heat-sensitive layer, and 22 is a capacitor.

Claims (1)

[Scope of utility model registration request] A switching element controlled by resistance changes in the temperature sensing part, a bypass circuit in which a charging circuit is connected in parallel with a high resistance connected in series to the switching element, and a diode and a capacitor connected in series, and a discharge circuit for the capacitor. 1. A temperature control device comprising: a thyristor to which a gate electrode is connected; and a main heater connected in series to the thyristor.