JPH02128204A - temperature control device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a temperature control device that uses a relay to turn on and off power supplied to the heater of various appliances, such as an iron, to keep the temperature of the heater constant. .

Conventional technology A conventional temperature control device of this type is shown in FIG.

1 is the heater, 2! L and 2b are a coil portion and a contact portion that constitute the relay. When the transistor Q is turned on, a voltage is applied to the coil portion 2a of the relay, the contact portion 2b is turned on, power is supplied to the heater 1, and heating is performed.

When the transistor Q is turned off, the voltage applied to the coil portion 2& becomes zero, the contact 2b is turned off, power supply to the heater 1 is stopped, and heating of the heater 1 is stopped.

Process 0 is an integrated circuit that includes a temperature detection circuit such as a microcomputer. It receives a signal from a temperature detection element Rth such as a thermistor, and when the temperature is low, it flows a base current to transistor Q through resistor R4 and turns on transistor Q. let Furthermore, when the temperature is high, the base current is turned off and transistor q is turned off.

Diode D3 rectifies the AC power supply VAQ, resistor R2 drops the voltage, capacitor C2 smoothes the rectified voltage,
The DC supply voltage to the integrated circuit IC is obtained.

The operation of this relay circuit is as follows.

When transistor Q is off, AC power supply VACl capacitor C1, resistor R1 + diode D1 is connected to capacitor C1.
When the transistor Q is turned on, the discharging current 11 of the capacitor C1 flows through the coil portion 2a of the relay, so that the relay coil terminal voltage v0 becomes equal to or higher than the relay voltage V&. When the voltage VIL or more is applied to the coil portion 21L of the relay, the relay is turned on, and once the relay is turned on, it continues to be turned on even if the relay coil terminal voltage VC is lowered. The minimum voltage that maintains this relay on state is called the holding voltage vb, but in the circuit shown in Figure 4, once the relay is turned on, the coil terminal voltage Vc is lowered by the resistor R1 and set to a level slightly higher than the holding voltage Wb. However, the heat generation in the coil section 2& of the relay is suppressed to a small level.

Here, the diode D1 is used to rectify the AC power supply VAC into DC, and the diode D2 is used to protect the transistor Q by absorbing the surge voltage generated between the coil portion 21L when the current flowing through the coil 2a is turned off. It is. The terminal voltage waveform between the coil portion 2a of this relay is
Shown in the figure.

Problems to be Solved by the Invention However, the above configuration has the following problems when maintaining the relay in the on state.

Now, when the relay is in the on state and the terminal voltage To of the coil part 2a of the relay is lower than the moving voltage V, which is slightly higher than the holding voltage Vb, the AC power supply "AC will be interrupted for a short time due to some reason. In this case, the power supply of the integrated circuit IC including the temperature detection circuit is connected to the capacitor C.
2, the AC power supply VA (+) is secured without any problem even if the power is interrupted for a short time. Therefore, the base current that turns on the transistor Q continues to flow through the capacitor C2, the emitter and base of the transistor Q, and the resistor R4, and the transistor Q The on state continues.However, the coil part 2a of the relay
Since the AC power supply VAO has failed, the voltage vc between the two becomes lower than the holding voltage, and the contact portion 2b of the relay is turned off. Next, when the AC power supply vAc is restored, the transistor Q continues to be in the on state, and due to the voltage drop due to the resistor R1, the capacitor C1 is not charged to a voltage higher than the relay voltage va, and the terminal voltage of the coil section 2a of the relay Since VC returns only to about the holding voltage and does not reach the touching voltage V&, the contact portion 2b of the relay remains off. Therefore, the temperature continues to drop, the transistor Q remains on, and there is no opportunity to charge the capacitor C1, and the relay contact 2b remains off forever.

The present invention solves the above-mentioned conventional problems, and aims to provide a temperature control device that operates without any problem even if there is a momentary power outage.

Means for Solving the Problems In order to achieve the above object, the means of the present invention includes a relay,
switching circuit, capacitor, timer circuit,
It consists of a temperature detection circuit, and a timer circuit measures the time that the switching circuit is on, and if it is longer than a specified time, it is determined that a momentary power outage has occurred.

Effects of the present invention With the above-described configuration, when the power supply experiences a momentary power outage, the terminal voltage of the coil section of the relay drops below the holding voltage, the contact section of the relay turns off, and the temperature drops, the switching circuit continues to be on, but the power supply Even when the relay is restored, the terminal voltage at the coil section of the relay does not reach the sensing voltage, so the relay's contact section continues to be off, the temperature continues to drop, and the output from the temperature detection circuit continues to issue a signal that turns on the switching circuit. This abnormally long ON signal output time is measured, and when the specified time is exceeded, a signal is output to turn off the switching circuit, the capacitor is charged to a high voltage, the ON signal is output again, and the switching circuit is turned on. Then, the terminal voltage of the relay's coil section becomes equal to or higher than the sensing voltage, turning on the relay and returning to the normal operating mode.

Embodiment FIG. 1 is a block diagram showing an embodiment of the temperature control circuit of the present invention. In FIG. 1, 1 is a heater, and 2 is a relay, which is composed of a coil portion 2a and a contact portion 2b.When the contact portion 2b is turned on, a power source 8 is connected to the heater 1.
When the temperature of the heater 1 increases and the contact portion 2b turns off, the power supply 8 to the heater 1 is cut off and the temperature of the heater 1 decreases.

Reference numeral 3 denotes a switching circuit, which applies voltage to the coil portion 2a through the DC power supply 1Q when turned on, and cuts off when turned off.

4 is a capacitor, and when the switching circuit 3 is off, it is charged to a voltage higher than the relay voltage Vh (Fig. 3), and when the switching circuit 3 is on, the capacitor 4 is discharged, and the terminal of the coil part 2 is connected to the capacitor. When the voltage is equal to or higher than the emotional voltage V, the contact portion 2b is turned on. When the relay 2 is turned on, the terminal voltage of the coil portion 2a of the relay is lowered by the resistor 9 and maintained at a level slightly higher than the holding voltage. 7 is a temperature sensing element;
The temperature of heater 1 is detected. The output of the temperature sensing element 7 is
The temperature detection circuit e outputs a signal to turn on the switching circuit 3 when the temperature of the heater 1 is low, and a signal to turn off the switching circuit 3 when the temperature of the heater 1 is high.

The timer circuit 5 measures the time during which the temperature detection circuit 6 outputs a signal for turning on the switching circuit 3, and turns off the switching circuit 3 when the specified time is exceeded.

Furthermore, the timer circuit 6 measures the time during which the switching circuit 3 is turned off, and when the specified time elapses, the output from the timer circuit 5 is stopped, so that the switching circuit 3 is controlled only by the signal from the temperature detection circuit 6. It is configured.

FIG. 2 shows a specific circuit of an embodiment of the present invention.

``AC is a power source, and when the contact part 2b is turned on, current is passed through the heater 1 and the heater 1 is heated.

In addition, the power supply VmuC is rectified by a diode D3, smoothed by a capacitor C2, and the voltage is dropped by a resistor R2. .

The temperature detection element 7 is a thermistor Rth, etc., and the heater 1
, and inputs it to the temperature detection circuit 6. The timer circuit 6 measures the time during which the output of the temperature detection circuit e outputs a signal that turns on the transistor Q1. Other components are the same as the conventional series.

The operation of the circuit shown in FIG. 2 will be explained using FIG. 3.

After turning on the power, relay 2 is turned on at time To. relay 2
Since transistor Q1 is off until it is turned on,
Capacitor C1 is charged to a high voltage, but at time T
At o, the temperature detection circuit 6 determines that the temperature of the heater 1 is low,
When a signal is output to turn on the transistor Q1, the transistor Q1 is turned on, and the discharge current of the capacitor C1 flows to the coil portion 2a of the relay, and the terminal voltage VC of the coil portion 21L is obtained to be equal to or higher than the impression voltage Va, and the contact portion 2b is turned on. Then, the temperature of the heater 1 increases as shown in FIG. 3B. Then, the power supply VAC loses power at time T1 and returns at T2.
If a momentary power outage occurs, as mentioned above, at time T
1, the contact part 2b is turned off, and even if the power is restored at τ2, the coil terminal voltage does not reach the touching voltage V&, and the contact part 2b is turned off.
continues off.

Therefore, the temperature continues to fall, and therefore the temperature detection circuit 6
The signal that turns on the switching circuit 3 continues to be output.

The timer circuit 6 measures this relay-on time, and outputs a signal to turn off the switching circuit 3 when the specified time t1 is reached. The timer circuit 5 measures this off time and outputs a signal to turn on the switching circuit 3 after a certain period of time t2. During this off time t2, capacitor C1
Power supply V,. , is charged through the resistor R1 and the diode D1, and when the switching circuit 3 is turned on again, the terminal voltage vO of the coil section 2& is obtained to be equal to or higher than the touching voltage V, and the relay 2
can be turned on to return to normal temperature control mode.

Effects of the Invention As described above, according to the present invention, it is possible to provide a temperature control device that suppresses heat generation in the coil portion of a relay and does not cause any problems even in the case of instantaneous power outages.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a temperature control circuit according to an embodiment of the present invention, FIG. 2 is a specific circuit diagram showing an embodiment of the present invention, and FIGS. A coil terminal voltage waveform diagram and a temperature characteristic diagram for explaining the operation, and FIGS. 4 and 6 are a conventional temperature control circuit diagram and a coil terminal voltage waveform diagram of a relay. 2... Relay, 3... Switching circuit sC1... Capacitor, 5... Timer circuit, 6... Temperature detection circuit. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (1)

[Claims] There is a relay that turns on and off the power supply to the heater, a switching circuit that turns on and off the voltage applied to the coil of the relay, and a relay that charges when the switching circuit is off and discharges when the switching circuit is on. A capacitor that applies a discharge voltage to the coil portion, and a switching circuit that turns off when the switching circuit is turned on for a first specified time,
This temperature control device includes a timer circuit that turns on the switching circuit when the off time has elapsed for a second specified time, and a temperature detection circuit that turns on the switching circuit when the temperature is low and turns off the switching circuit when the temperature is high.