JPS5914977B2 - temperature control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zero-20 volt temperature control system for inductive loads using heat sensitive thyristors.

FIG. 1 is a circuit diagram showing an example of a temperature control device using a conventional heat-sensitive thyristor. In the figure, 1 is an AC power supply, 2 is a resistive load such as a heater, and 3 is a three-terminal bidirectional thyristor (hereinafter referred to as a TRIAT) connected in series to this load 2 to control the AC 25-current power supplied to the load 2. ). 11 is a first auxiliary thyristor for triggering the triax 3 via the gate resistor 4; 10 is a capacitor for triggering the triax 3; 8 is a resistor for charging the capacitor 10; 5 is a resistor for charging the capacitor 10; The first auxiliary thyristor 11, the capacitor 10, the resistor 8, and the rectifier diode 5 constitute a first series body, which is connected in parallel to the AC power supply 1. .

6 is a second auxiliary thyristor connected in antiparallel to the 35 rectifier diode 5; T is a rectifier diode for preventing gate reverse voltage connected between the gate and cathode of the thyristor 6; 9 is the gate of the thyristor 6; This is a trigger resistance.

Further, 16 is a heat-sensitive thyristor for detecting the temperature around the load 2, 19 is a constant voltage diode for clipping the forward voltage of the heat-sensitive thyristor 16 to a constant value, 1
7 is a capacitor for passing a current whose phase is ahead of the power supply voltage; 18 is a resistor for charging the capacitor 17; the voltage regulator diode 19, the capacitor 17, and the resistor 18 constitute a second series body. , the second series body is connected in parallel with the AC power supply 1. 12,1
3 are resistors connected in series between the anode and cathode of the heat-sensitive thyristor 16, and both of these resistors 1
The connection point 2 and 13 is connected to the gate of the first auxiliary thyristor 11.

Further, 14 is a variable resistor connected between the anode and gate of the heat-sensitive thyristor 16 to set the switch temperature, and 15 is a capacitor connected in parallel with the variable resistor 14 for noise prevention. 20 is a noise prevention capacitor connected between the anode and cathode of the voltage regulator diode 19.

Next, the operation will be explained.

First, when the load 2 is a pure resistance load such as a heater, when the ambient temperature of the heat-sensitive thyristor 16 is lower than a set value, the heat-sensitive thyristor 16 is turned off. Here, since a voltage is applied to the anode of the first auxiliary thyristor 11 along the path of power supply 1 → load 2 → T1 terminal of triax 3 → gate terminal, the power supply voltage is applied with almost the same phase. On the other hand, at the gate of the first auxiliary thyristor 11,
A voltage is applied along the path of power supply 1 → capacitor 17 → resistor 18 → resistor 12 → gate of first auxiliary thyristor 11. Therefore, the current phase advances due to the capacitor 17,
A gate current flows through the gate of the thyristor 11 before a positive voltage is applied to the anode of the thyristor 11, and the thyristor 11 is triggered as soon as its anode becomes positive. In this way, the first auxiliary thyristor 11 is turned on at the zero phase of the power supply voltage, and at the same time the power supply 1 → load 2
The gate current of the triac 3 flows through the path of → T1 terminal of the triac 3 → gate terminal → resistor 4 → thyristor 11. Therefore, tryack 3 is turned on.
Supply power to load 2. At this time, since most of the power supply voltage is applied to the load 2, the capacitor 10 is charged via the rectifier diode 5 and the resistor 8 as shown. Next, when the power supply 1 enters a negative cycle, the gate current flows to the second auxiliary thyristor 6 via the resistor 9.
When this thyristor 6 is turned on, the electric charge of the b capacitor 10 is transferred from the resistor 8 to the thyristor 6 to the load 2 to the triax 3.
T, terminal → gate terminal → resistor 4 in a closed loop to discharge.

Therefore, the triac 3 is turned on and power is supplied to the load 2. Since power is subsequently supplied to the load 2 in the same manner, the temperature of the heater, etc. of the load 2 increases.

As a result, the heat-sensitive thyristor 16 thermally coupled to the load 2 has a gate impedance and an applied voltage, that is, the resistance 14.
The switch temperature determined by the voltage of the constant voltage diode 19 is reached, and the heat-sensitive thyristor 16 is turned on. Then, the gate current that has been supplied to the first auxiliary thyristor 11 is bypassed from the anode to the cathode of the heat-sensitive thyristor 16, and the thyristor 11 is turned off.
Therefore, the triax 3 is also turned off, and power is no longer supplied to the load 2. Furthermore, the capacitor 10 is not charged, and even if the power supply 1 enters a negative cycle, the triac 3 remains off, and the load 2 is naturally cooled. In this way, the heat-sensitive thyristor 16 detects the ambient temperature and turns on and off, so that the temperature of the load is controlled to be constant.

As mentioned above, the conventional circuit operates without problems when the load 2 is a resistive load such as a lamp or heater, but when the load 2 is an inductive load such as a motor or relay, the heat-sensitive thyristor 16 changes from the OFF state to the ON state. Even when this occurs, current continues to flow through the load 2 during the positive half cycle of the power supply 1.

Therefore, in that positive half cycle, load 2, capacitor 10
Energy is charged in the power supply 1, which sometimes causes a problem in which the triax 3 is erroneously triggered during the negative half cycle of the power supply 1. This invention was made in order to eliminate the drawbacks of the conventional temperature control device using a heat-sensitive thyristor as described above, and includes a first rectifier diode in series with a capacitor for slave triggering of a triac, and a first rectifier diode in parallel with a capacitor for triggering a triact. It is an object of the present invention to provide a temperature control device that can perform temperature control without malfunctioning even in the case of an inductive load by connecting a second rectifier diode in the same manner as in the case of a resistive load.

An embodiment of the present invention will be described below with reference to the drawings. Second
For the sake of illustration, 1 to 20 are the same as those in FIG. 1, so a detailed explanation will be omitted. A first rectifier diode 21 is connected in series with the gate current limiting resistor 4 of the triac 3, and the cathode of the first rectifier diode 21 is connected to the anode of the first auxiliary thyristor 11.

22 and 23 are second capacitors connected in parallel with the capacitor 10.
The anode side of the diode 22 is connected to the anode side of the thyristor 11.

In such a configuration, when the heat-sensitive thyristor 16 is turned on, the thyristor 11 is turned off, but the load 2
is inductive, so during the positive half cycle of the supply voltage,
Current continues to flow in the path of power source 1 → load 2 → triax 3, and the load 2 is charged with the polarity shown. Therefore, if the first diode 21 is not present, the energy stored in the inductive load 2 is transferred from the diode 5 to the resistor 8.
→Capacitor 10 →Resistor 4 flows through the path, and the capacitor 10 is charged. Then, when the power supply voltage is in a negative half cycle, the second auxiliary thyristor 6 is triggered and turned on, so that the charge stored in the capacitor 10 is transferred from the resistor 8 to the thyristor 6 to the load 2 to the triax 3.
1 terminal→gate terminal→resistor 4 in a closed loop, the triax 3 is triggered, and power is supplied to the load 2. However, in this embodiment circuit, since the first rectifier diode 21 is provided, the above-mentioned Capacitor 10 like
The charging current can be cut off.

However, if only the first rectifier diode 21 is inserted, the capacitor 1
0 may be charged to the opposite polarity as shown, and just before the positive cycle, capacitor 17, resistor 18, and resistor 12 are charged.
For example, the thyristor 11 may be turned on, which may also trigger the triator 3. Therefore, the second
The rectifier diode 11 and resistor 23 bypass the reverse charging current to the capacitor 10. Therefore, when the heat-sensitive thyristor 16 is turned on, the capacitor 10 is not charged, and normal temperature control is possible without the above-mentioned malfunction.

The device of this embodiment has the following effects.

(a) Temperature control of resistive and inductive loads becomes possible by simply adding a simple circuit (circuit component).

(b) Since the terminals of the thermal thyristor are not floating above the AC power line, it operates stably with fewer malfunctions due to external noise.

(c) Since it is a zero-volt switch circuit, it does not generate radio noise.

Therefore, no noise filter is required. Incidentally, in the above embodiment, the case where an n-gate heat-sensitive thyristor is used has been described, but the present invention can also be applied to a case where a p-gate heat-sensitive thyristor is used.

However, in that case, it goes without saying that the switch temperature setting variable resistor 14 and the malfunction prevention capacitor 15 are connected between the gate and the cathode. Further, in the above embodiment, only one heat-sensitive thyristor is connected, but a plurality of heat-sensitive thyristors may be connected in parallel or in series depending on the capacity of the object to be controlled, the type of control, etc. As described above, according to the present invention, the first rectifier diode is connected in series with the capacitor for dependent triggering of the triact to prevent excess charging from the load when the heat-sensitive thyristor is on, and the above-mentioned By connecting a second rectifier diode in parallel with the capacitor to bypass the charging current to the capacitor during the negative half-cycle of the power supply, the resistor This has the effect of accurately controlling the temperature of the load and the inductive load.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a conventional temperature control device, Figure 2 is a circuit diagram showing an example of a conventional temperature control device.
The figure is a circuit diagram showing a temperature control device according to an embodiment of the present invention. 1...AC power supply, 2...Load, 3...
...3-terminal bidirectional thyristor, 6...2nd
auxiliary thyristor, 10... second capacitor, 11... first auxiliary thyristor, 16...
...Thermal thyristor, 17...First capacitor, 21...First rectifier diode, 22.
...Second rectifier diode.

Claims (1)

[Claims] 1. An AC power supply, a load whose one end is connected to the positive power terminal of the AC power supply, and a power supply connected between the other end of the load and the negative power terminal of the AC power supply to control on/off the power supplied to the load. a bidirectional thyristor whose cathode is connected to the negative power supply terminal and which detects the temperature around the load and turns on when the temperature is above a predetermined temperature and off when it is below a predetermined temperature; a first auxiliary thyristor that turns on when the heat-sensitive thyristor is off during a positive half cycle of the AC power supply and supplies a gate current to the bidirectional thyristor to turn it on; a first capacitor inserted between the power supply terminals and supplying a current with a phase leading from the current power source to the gate terminal of the first auxiliary thyristor;
a second capacitor connected to the anode of the auxiliary thyristor and charged during the positive half cycle of the power supply when the first auxiliary thyristor is on; Connected to the above positive power supply terminal and connected to the above first
a second auxiliary thyristor that, when the auxiliary thyristor is on and the AC power supply reverses to a negative half cycle, discharges the charge of the second capacitor and supplies a gate current to the bidirectional thyristor to turn it on; a thyristor, a cathode connected to a connection point between the second capacitor and the first auxiliary thyristor, and an anode connected to the gate terminal of the bidirectional thyristor, the heat sensitive thyristor is on and the alternating current is applied during a negative half cycle period; a first rectifier diode for preventing charging of the second capacitor by the load;
The cathode is connected in parallel to the capacitor such that the positive electrode is at the positive power terminal end of the second capacitor and the anode is the negative power terminal end of the capacitor, and the power supply is connected to the second capacitor during a negative half cycle period. and a second rectifier diode for bypassing the charging current.