JPS6012689A - Heater drive controller - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature detection device using electrical resistance, and more specifically, a heater is also used as a resistance temperature sensor, the heater temperature is measured immediately after the zero cross of the AC power supply, and the following measurement is performed according to the measurement result. The present invention relates to a device that controls on/off of heater drive during a half cycle period.

Generally, a commercial AC power source is used as the power source for driving the heater, so when the heater is also used as a temperature detection sensor,
Blocking diodes must be used to prevent alternating current voltages from being applied directly to the circuits that process the sensor's output voltage. In this case, the forward voltage drop of the blocking diode is very small, approximately O1. However, if the measurement accuracy is to be improved, this slight forward voltage drop of the diode becomes a problem.

The purpose of the present invention is to reduce the number of component parts as much as possible, and to reduce the power loss consumed for temperature measurement as much as possible.
It is an object of the present invention to provide a heater drive control device which has very high temperature measurement accuracy and can therefore accurately control the heater temperature to a set value.

The heater drive control device of the present invention connects a series circuit of a heater and a triac, which also serves as a resistance temperature sensor, to an AC power supply terminal, and provides a DC power supply using the heater example of the AC power supply line as a common line. The emitter of the switching transistor, which is conductive at times, is connected to the non-common side line of the DC power supply, and the collector of the transistor is connected through a resistor in the direction in which current flows through both 2IvA diodes when the transistor switches. Connect the other one of the diodes to the connection point between the heater and the triac, connect a load impedance between the other diode and the common line, and connect the load impedance to the connection point between the load impedance and the diode. The present invention is characterized in that the temperature detection signal is taken out and the above-mentioned l/liasok is controlled on/off based on the magnitude relationship between the temperature detection signal value and the set value.

Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a circuit diagram of an embodiment of the present invention.

A series circuit of heater 1 and triac 2, which also serves as a sensor, is connected to AC power terminals 3A and 3B, and the positive terminal side of DC power circuit 4, which converts this AC power to stabilized DC, is connected to AC power terminal 3A of the heater example. A common line 5 is defined as a common line 5, and a non-common line 6 is defined as a negative electrode side of the DC power supply.

A zero-crossing detection circuit 7 is provided which is operated by a DC power supply and detects the zero-crossing of the AC power supply, and conduction is switched by this zero-crossing detection signal].The emitter of the transistor 8 is connected to the non-common line 6 of the DC power supply, and its I- The cathodes of two diodes 10 and 11 are commonly connected from the collector of the transistor 8 through the resistor 9, and the anode of one diode 10 is connected to the connection point 11 between the heater 1 and the triac 2, and the anode of the other diode 10 is connected to the connection point 11 between the heater 1 and the triac 2. ! A load impedance 12 is connected between the anode of "it" and the common line 5, and a temperature measurement signal em is taken out from the connection point F between the load impedance 12 and the diode 11. On the other hand, between the collector of the transistor 8 and the common line 5 A diode P'l 3 and resistors 14 and 15 are connected in series, and a control set voltage es is taken out from the connection point E. A comparator 16 determines the magnitude relationship of the π constant signal em with respect to the set voltage eS. The output line G of the comparator 16 is connected to the control gate of the triac 2 via a diode 17.

As is clear from this 1/3 configuration, the diode 11, 13 and the resistors 9, 12, 14, 15 form a first bridge circuit for comparing the measured value and the reference value, and the heater 1, the diode 10, . 11 and resistor 12 form a second bridge circuit for transferring the potential of α111 of heater 1 to measurement point F. Note that the value of resistor 12 is sufficiently higher than the resistance value of heater l. Next, the operation will be explained. Figure 2 shows the voltage waveforms of each part in Figure 1, and (1) shows that when the measured temperature is higher than the set temperature,
(■) indicates when the measured temperature is lower than the set temperature. Each waveform (A) to (II) corresponds to each point A-H in FIG.

The AC power waveform is a sine waveform as shown in figure (A),
When the potential at point A becomes the same as the common line, a zero cross signal is output as shown in figure (B). This zero-cross signal causes the transistor 8 to conduct for a moment, and a measuring current is supplied to the first and second bridge circuits. The triac 2 is turned off at any time due to the zero crossing of the AC power supply voltage.

From the connection point E on one side of the first bridge circuit to the reference potential e
s is obtained. This reference potential es can be adjusted by a variable resistor 15.

If the second bridge circuit is set so that the forward voltage drop across the diode 10 due to the heater current 11 is equal to the forward voltage drop across the diode 11 due to the current 12 in the load impedance 12, then F The potential at the point becomes equal to the potential at point F. For example, when jl=10i2, diode 10 using diode-1' with the same characteristics
This can be achieved by configuring one diode 11 with ten parallel connections, or by configuring one large capacity diode 10 and multiple small capacity diodes 11 connected in parallel. I can do it.

The current flowing through the resistor 9 on one side of the first bridge circuit for detecting the measured value is a combination of (i+ + i2), but in the case of i 1 >> i 2, it is due to the 1 degree change in resistance of the heater 1. The change in resistance of the heater 1 becomes almost the same as the change in point F.

The measured value em obtained in this way and the reference value e mentioned above
A comparator 16 compares s. The measured temperature is better
When gl', 'fj, degree is higher than 1-rigger pulse is not applied to the triac as shown in (1), and the triac remains off for the next half cycle. Conversely, if the measured temperature is lower than the reference temperature, a trigger pulse is applied to the triac after the zero-crossing period, and the triac is turned off for the next half cycle.

When triac 2 is on and non-common line A
During the positive half cycle IIa where the point is higher than the commo line, an alternating current voltage appears at point D as shown in figure (D), but the diode 11 blocks this alternating voltage, and the opposite negative half During cycle lb, diode 10 blocks the alternating voltage.

As a result, a high AC voltage is not applied to the measurement value input terminal F point of the comparator 16 even when the heater I is energized during non-measurement periods. Also, during the positive half cycle, as shown in Figure (C), an AC voltage also appears at the 0 point, but the diode 13 blocks this AC voltage, so a high voltage is applied to the reference value input terminal of the comparator 16 at the E point. No alternating current voltage is applied. Note that since the transistor 8 is selected to have a high collector voltage, it can withstand a positive half cycle.

FIG. 3 shows an embodiment of a display device according to the present invention that constantly displays the temperature of the measured value eIn measured at each zero cross. The circuit 21 consisting of the operational amplifier A1 is an impedance conversion circuit. The circuit 22 consisting of the operational amplifier A2 is an adder whose output em2 connects the inputs em+ and E
When it is ltl, F, then it becomes. A circuit 23 consisting of an operational amplifier A3 converts a DC voltage E- to a positive reference voltage E,
This is a circuit that obtains the following. A zero-crossing signal is applied to the gate electrode of FET24, and this transistor 24 becomes conductive at each zero-crossing. The sample and hold circuit 25 holds the output em2 of the adder and updates its value at every zero cross. The Δ/D converter 26 is a sample ball 1-circuit 2
5 is digitally converted using EREF as a reference voltage. The display device 27 visually displays the value.

In the above equation regarding the adder 22, since the voltage em is a negative value, the value in parentheses in the above equation is a subtraction process, and the resistor R is set so that the output voltage is Ov when the heater temperature is 0°C.
3, and the resistor R1 can be selected so as to obtain an output voltage proportional to the temperature. In this way 0°
When C, the output becomes 0■, a positive voltage em7 proportional to the temperature rise is obtained, and this can be displayed.

According to the present invention, there are the following effects.

■Since it serves as both a resistance temperature sensor and a heater, a total of two lead wires are required for the sensor and the heater, making it especially effective when the heater temperature is to be controlled, such as in hair irons, electric blankets, etc. big.

■Since the current for temperature detection flowing to the heater is extremely short at the time of zero crossing, it is easy to flow a large pulsed current to it, and even when the heater resistance value is small, a large detection voltage can be generated. iM, no amplifier circuit is required,
This also simplifies the detection circuit configuration.

■Since the AC voltage applied to the heater during non-temperature measurement is blocked by the diode, no trouble occurs to the control circuit such as the comparator.

■Two guides 10 forming the second bridge circuit
．． 11 is canceled out and the measurement signal detection point F
A voltage equal to that of the heater terminal I (point) appears, improving the temperature measurement density.

■Load impedance 1 forming the second bridge circuit
If the value of 2 is selected to be sufficiently large for the heater resistance, the voltage change due to the change in heater resistance during temperature measurement becomes almost the same as the voltage change at the measurement signal detection point F, improving the temperature measurement sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is an operation explanatory diagram showing voltage waveforms at each part thereof, and FIG. 3 is a circuit diagram showing an embodiment of a display device related to the present invention. 1-Heater that also serves as a sensor 2-1-Liasoku 38, 3B-AC power supply terminal 4-DC power supply circuit 7-Zero cross detection circuit 8-Switching transistor 9-Resistor 10.11-Diode 16-Comparator Patent applicant Hide Sugimori Husband agent Patent attorney Nishi 1) Arata

Claims (1)

[Claims] A series circuit of a heater and a triac, which also serves as a +11 resistance temperature sensor, is connected to an AC power terminal, and the heater side of the AC power line is used as a common line to connect a DC power source.''
- Connect the emitter of the switching transistor that conducts at the zero cross of the distribution AC power supply to the non-common line of the DC power supply, and determine the direction in which current flows from the collector of the transistor through a resistor to both of the two diodes when the transistor switches. and connect the other of one of the diodes to the connection point of the heater and the triac, and connect a load impedance between the other diode of the IW and the common line, A heater drive control device characterized in that it is configured to take out a temperature detection signal from the connection point between the load impedance and the diode, and control the above-mentioned first reactor on and off based on the magnitude relationship between the temperature detection signal value and the set value. ) A variable voltage dividing circuit is provided between the collector of the switching transistor and the common line through a diode, and a reference voltage for temperature detection is applied from the voltage dividing point of the variable voltage dividing circuit, as set forth in claim 1. heater drive control device.