JPH042078A - Electric heater driving device - Google Patents

Abstract

PURPOSE:To make power adjustment through periodic turning-on and -off of a relay using a small and cheap relay contact by furnishing No.1, No2 relay at the ends of a heater, and opening and closing one of them in the neighbor hood of zero volt of AC power supply. CONSTITUTION:When a start switch is pushed, No.2 relay 7 is actuated, and if thereafter another relay 6 is to be driven with On signal from a drive signal generating means 9. No.1 relay 6 shall be actuated. Therein the relay 6 is actuat ed in the neighborhood of zero volt of the AC power supply 10 on the basis of signals from a power supply synchronous signal generating means 11, driving phase determining means 14, and contact opening/closing means 15. When a heating stop switch is pushed and the output of the signal generating means 9 is put off, the contact of the relay 6 is opened in synchronization with the zero point of the power supply 10, and then the No.2 relay 7 is deactuated. This enables suppressing arc generation at the contact of the relay, and power adjustment can be done by use of a cheap relay.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a heater drive device used in an electric heater such as an electric cooking heater used in a general household.

Conventional technology In recent years, heater drive devices for electric heaters such as electric shoe heaters are required to have a long life by preventing welding of the contacts, and it is also important to ensure safety in the event that the contacts do weld. It has been demanded.

Conventional heater drive devices for electric heaters of this type, such as electric heating heaters, generally have a configuration as shown in FIG. 13. The configuration will be explained below.

As shown in the figure, relays 2 and 3 are connected to both ends of the heater 1, and upon receiving a signal from the drive signal generating means 4, the relays are turned on by the contact opening/closing means 6.

It was off.

This is due to the following reason. In recent years, the spread of electrical equipment has been remarkable, and the number of so-called all-electric homes, where all of the heat in the home is powered by electricity, is increasing. Furthermore, an earth leakage breaker is generally used as a safety device for commercial power supply circuits. However, if one of the heaters that makes up the heater
If the heater cannot be disconnected due to poor insulation, the earth leakage breaker will trip and cut off the power, making other equipment unusable. In contrast, with the above configuration, even if one of the multiple heaters has poor insulation, the heater with the defective insulation can be disconnected from the power circuit by turning off the relays at both ends of the heater. This is because other heaters can be used for cooking, and of course other equipment can also be used.

Problems to be Solved by the Invention In such conventional heater drive devices for electric heaters, relays with large contacts have to be used as devices become more powerful, resulting in higher costs and shorter operating times. There is a problem in that it is difficult to periodically adjust the power by turning on and off at intervals (about 10 seconds to 1 minute) because there is a limit due to the lifespan of the relay contacts.

Another problem is that when the power of the device increases, especially when 200 volts is used as a power source, the relay contacts are severely worn out and their lifespan is significantly shortened.

Furthermore, when the lifespan of the relay contacts finally expires, many of them tend to weld and become continuously energized, making it impossible to adjust the amount of heating or resulting in a lack of safety.

The present invention solves the above-mentioned problems by periodically turning on the relay using a small and inexpensive relay contact.

A first object of the present invention is to provide a heater drive device for an electric heater that can perform power adjustment by turning off the heater.

A second purpose is to extend the lifespan of relays used in heater drive devices for electric heaters. The third objective is to extend the usable period of the electric heater, and the fourth objective is to increase the safety of the electric 7Xl heater.

Means for Solving the Problems In order to achieve the first object, the present invention connects two relays to both ends of a heater, and provides a drive circuit for driving these relays. drive signal generating means for instructing opening/closing of the AC power supply, and power supply synchronization signal generating means for generating a signal synchronized with zero volts of the AC power supply;
contact signal generating means for generating a signal according to the open/closed state of the relay contact; and time difference measuring means for inputting the synchronizing signal from the power synchronization signal generating means and the contact signal from the contact signal generating means and measuring the time difference therebetween. and drive phase determining means for determining the drive phase of the relay based on the measurement signal of the time difference measuring means, and contact opening/closing means for opening and closing the relay contacts in response to the output signal from the drive phase determining means,
The first problem-solving means is that one of the two relays is opened and closed near zero volts of the AC power supply. In addition, in order to achieve the second purpose,
In addition to the problem solving means, the drive circuit is equipped with a timer or counter, and each time a predetermined time elapses or the relay is opened and closed a predetermined number of times, one of the two relays opens and closes at around zero volts of the AC power supply. The second means of solving the problem is to alternate between the relay and the other relay. Furthermore, in order to achieve the third objective, in addition to the first or second problem solving means, the drive circuit inputs the output of the contact opening/closing means and the contact signal from the contact signal generating means, and The system is equipped with a contact welding detection means that detects welding of the relay contacts based on mismatch, and when welding of the contacts is detected, the relay with no contact welding is opened and closed at around zero volts of the AC power supply. This is a means of solving the 3 problems. Furthermore, in order to achieve the fourth objective, in addition to the first or second problem-solving means described above, when contact welding is detected by the contact welding detection means, both relays are turned off. This is considered the fourth means of solving the problem.

According to the first problem solving means described above, the relay that controls the current flowing through the heater is controlled by learning so as to turn on and off at the zero point of the AC power supply, thereby suppressing the occurrence of arc discharge at the contacts. . Seriously, with the second problem solving method,
The relay for power regulation is replaced at predetermined intervals, and the wear and tear on the relay contacts caused by periodic on/off cycles can be shared between the two relays. Furthermore, according to the third problem-solving means, when contact welding occurs in one of the two relays, the remaining one relay can be used to adjust the heating amount and control on/off. Further, according to the fourth problem-solving means, the subsequent 770 heat is prohibited when one of the two relays causes contact welding.

EXAMPLE Hereinafter, an example of the first problem-solving means of the present invention will be described with reference to FIG. Note that components having the same configuration as those of the conventional example are given the same reference numerals, and description thereof will be omitted.

As shown in the figure, a contact 61 of a first relay 6 and a contact 71 of a second relay 7 are connected in series to both ends of the heater 1. The drive circuit 8 drives the two relays 6.7, and this drive circuit 8 includes a drive signal generation means 9 for instructing the opening and closing of the relays 6.7, and a power supply for generating a signal synchronized with zero volts of the AC power supply 10. A synchronization signal generation means 11, a contact signal generation means 12 that generates a signal corresponding to the open/closed state of the relay contact 61, a synchronization signal from the power supply synchronization signal generation means 11 and a contact signal from the contact signal generation means 12 are inputted. A time difference measuring means 13 for measuring the time difference; a driving phase determining means 14 for determining the driving phase of the relay 6.7 based on the measurement signal of the time difference measuring means 13; Relay contact 61.7
1 and a contact opening/closing means 16 for opening and closing the terminal. In addition,
16 is a power supply for the drive circuit 8, 17 and 18 are rectifier nutacs,
19.20 is a photocoupler. In this embodiment, a drive signal generating means 9, a time difference measuring means 13, a drive phase determining means 14, and a contact opening/closing means 16 are connected to a key switch provided on the main body operation section (not shown). A signal is output to turn on the relay 6.7 for an arbitrary period of time within a predetermined period so as to achieve the heating amount set by , and turn it off for the remaining period. In another heating mode, based on the output of the temperature detection means that detects the temperature of the object to be heated, it is turned off when the temperature of the object to be heated is higher than a predetermined temperature, and when it is lower than a predetermined temperature. An on signal is output.

Next, IgJ works will be explained. FIG. 2 is a flowchart showing an outline of the operation, and the outline of the operation will be explained based on this FIG. First, in step 102, the process waits for a start switch (not shown here) provided on the heater body to be pressed. When the start switch is pressed,
In step 103, the second relay 7 is first turned on.

Next, the output of the drive signal generating means 9 is checked, and if it is an ON signal and it is necessary to drive the relay 6, the process proceeds to step 105, and the first relay is synchronized with the zero point of the AC% source 10. The contact 61 of No. 6 is turned on. Then, in step 106, again, the diagram is shown.

Step 7 checks to see if the ifP and W stop keys have been pressed, and if they are not pressed, the process returns to step 104.

Then, when the output of the drive signal generating means 9 changes to OFF and OFF drive becomes necessary, in step 108, the contact 611 of the first relay 6 is synchronized with the zero point of the AC TFI 10! -Turn it off. This ON operation in step 105 and step 1
The off operation of 08 will be explained later. On the other hand, when it is detected in step 106 that the heating stop key is pressed, in the next step 109, the contact 61 of the first relay 6 is turned off in synchronization with the zero point of the AC power supply 1o, and then the second
Turn off relay 7.

Next, the ON operation and OFF operation of the relay 6 will be explained. FIG. 3 is a flow chart of the operation when turning on the first relay 6 in synchronization with the zero point of the AC power source 1o, and FIGS. This is an example of a timing chart showing the relationship between the output of the contact opening/closing means 16 that opens and closes the contact 61, the voltage nm between the inputs c and d of the contact signal generating means 12, and the contact signal e that is the output. This shows what happens when you do this. At step 120 in FIG. 3, wait for the rise of the synchronization signal a from the power supply synchronization signal generation means 11,
When all the rising edges are detected, the signal waits for tl in step 121, and then outputs a signal to turn on the relay 6 in step 122. Here, tl is predetermined in step 1o1 of FIG. 2, and is set to 5m5ec in this embodiment. Next, in steps 123 and 124, the time ton1f from when the on signal is output until the contact 61 actually turns on is measured, and in step 126, tl is corrected. FIG. 4 shows that the timing when the contact 61 is actually turned on is synchronized with the zero point of the AC power supply, and the time base d of the power synchronization signal a and the contact signal e1 is
This is the case when t1 is almost zero and no correction is necessary.

In addition, when measuring the time difference dt between the power synchronization signal a and the contact signal e, these two signals are in phase with each other, so in this embodiment, the time difference between the output of the contact opening/closing signal b2 and the actual turning on of the contact 61 is Time! 1 ton is measured and calculated based on the power supply period TO determined in advance. That is, dt1=To-tl-tonl
−········−(1).

Next, the waiting time correction process will be explained.

FIGS. 6A to 6D are diagrams showing a case where the contact 61 closes too early, and a time difference dt2 occurs between the power synchronization signal a and the contact signal e2. Therefore, t2+dj,2 is determined and this is set as the next waiting time t3. By the way, the next waiting time t2+dt2 is calculated from equation (1) as t2+dt2=t2+To-t2-ton2=TO-t
on2 ・・・・・・・・・・・・・・・(2)
Therefore, the calculation is simplified by setting ts='ro-ton2. Even if the contact 61 closes too late, the waiting time for closing is similarly corrected.

Fig. 6 is a flowchart of the operation when turning off the first relay 6 in synchronization with the zero point of the AC power supply 1o, and Figs. 7(A) to (D) are timing charts showing the opening of the contact 61. FIG. This relay 6
When turning off the AC, the time toffA from the off output of the snort opening/closing means 15 to the output of the contact signal generating means 12 is measured, and the next waiting time is corrected. It is synchronized with the zero point of power supply 1o.

However, in the case of OFF operation, a pulse is generated in the output signal e of the contact signal generating means 12 near the zero point, so the sixth
The judgment at step 134 in the figure is “e signal is 0.6ms+
Is it higher than e c? "I have to. Furthermore, when turning off the relay 6, once the arc discharge starts, it will continue until the voltage becomes almost 0, so in the waiting time correction in step 136, an additional 0.4m84I from the zero point is applied.
I try to turn it off before C or 1m1eC. By repeating the above operation, the second relay 7 is always turned on and off with the heater 1 in the emergency state, and the first relay 6
is turned on and off at the zero point of the AC power source 1o.

Next, an embodiment of the second problem solving means will be described with reference to FIG. Note that the same components as those in the above embodiment are given the same reference numerals, and the explanation thereof will be omitted.

As shown in the figure, when a predetermined time has elapsed, the timer 16 controls the contact opening/closing means 16 based on its output, and the contact opening/closing means 16 controls a relay 6.7 that turns on and off at the zero point of the AC power source 1o. They are replaced at predetermined intervals.

The operation of the above configuration will be explained along the flowchart of FIG. After the initial settings in step 201, a check is made to start heating in step 202, and if heating has started, the timer 16 is cleared in step 203, the timer flag is reset, and then the second relay 7 is turned on in step 204. I'll keep it. Step 206 is timer 1
In the routine that counts up 6, a timer flag is set every predetermined time. Steps 206 to 212
As in the above embodiment, if it is necessary to turn on the first relay 6, the AC is turned on at the zero point of the source 10 in step 207, and if it is necessary to turn it off, the AC power source 1o is turned on in step 210. Turn it off at the zero point and check whether the heating has stopped in step 208. If heating is to be stopped, turn off the first relay 6 at the zero point of the AC power source 1o in step 211, and then turn off the second relay 6 in step 212. Relay 7 is turned off.

In step 213, a timer flag set by the timer 16 at predetermined time intervals is checked to determine whether a predetermined time has elapsed. If the timer flag is set, the relay 7 is also turned off at step 214 and the process proceeds to step 303. Step 303
Steps 314 to 314 are exactly the same as steps 203 to 214 except that the first relay 6 and the second relay 7 are exchanged and controlled, and the second relay 7 is switched to the AC current m1o until the predetermined time elapses again. It is turned on and off at the zero point of , and when a predetermined time has elapsed, the process returns to step 203.

By repeating the above operation, the consumption of the contacts of the first relay 6 and the second relay 7 is reduced by half compared to the case where the heater 1 is turned on and off by only one relay. Note that a counter may be provided in place of the timer 16, and the relay 6.7 may be replaced every time a predetermined number of relays 6.7 are opened or closed.

Next, an embodiment of the third problem-solving means will be described with reference to FIG. 10. Note that the same components as those in the above embodiment are given the same reference numerals, and the explanation thereof will be omitted.

As shown in the figure, the contact welding detection means 17 inputs the output signal of the contact opening/closing means 16 and the contact signal of the contact signal generation means 12, detects welding of the contact from the mismatch between the two, and this contact welding detection means 17 Contact opening/closing means 16 based on the output of
Controls heater 1 using the relay that does not cause contact welding.

The operation of the above configuration will be explained along the flowchart of FIG. 11. Steps 201 to 214
, and steps 303 to 314 are similar to those in the embodiment of the second problem solving means, except that a process for checking the output of the contact welding detection means 17 is added after steps 210 and 310. Regarding the processing in step 216, steps 203 to 210 and 213
At step 214, the second relay 7 is always turned on and the first relay 6 is turned on and off at the zero point of the AC power source 10 to control the amount of power of the heater 1. If the contact 61 is welded despite trying to turn off the relay 6 of No. 1 at the zero point of the AC power supply 10,
Welding is detected by the contact welding detection means 1 and step 2
This is determined in step 16 and the process moves to step 303. Then, temporarily giving up on controlling the entire power amount of the heater 1 by turning the first relay 6 on and off, the first relay 6 is turned on and off.
is always on, and the amount of power of the heater 1 is controlled using the second relay 7. After that, when a predetermined time has elapsed according to the timer 16, the process returns to step 203 through steps 313 and 314, and the first relay 6 is turned on again.
The power amount of the heater 1 is controlled by turning it off.

This was done to test out the fact that as the relay contacts wear out, a slight welding or snag called soft stick occurs temporarily, but this soft stick often returns to normal after a slight trigger. Step 31
6 performs similar processing on the second relay 7.

With the configuration and operation described above, two relays 6.
Even if one of the relays 7 causes contact welding, this is detected and the other normal relay is used to supplement the electric power of the heater 1.

FIG. 12 is a flowchart showing the operation of the embodiment of the fourth problem solving means. When it is found in step 216 that the first relay 6 has caused contact welding, the process moves to step 311 and the second relay 7 is switched on. After turning off the AC power supply 10 at the zero point to prevent arc discharge, an off signal is also sent to the first relay 6, and the process returns to step 202. Step 3
16 has the same processing except that relays 6 and 7 are reversed.

With the configuration and operation described above, two relays 6.
When one of the relays 6 and 7 starts to weld, this is detected and both relays 6 and 7 are immediately turned off to stop heating.

Effects of the Invention As is clear from the above embodiments, according to the present invention, one of the two relays is opened and closed at around zero volts of AC electricity, so a small and inexpensive relay contact can be used. It is possible to adjust the power by periodically turning on and off the relay, and it is useful for improving cooking performance when used in heating cookers. Each time this is done, the relay that opens and closes near the zero port of the AC power supply is replaced, so it is possible to extend the life of the relay. Furthermore, if contact welding is detected and the normal relay F
Since this is done at power consumption i5, it is possible to extend the usable period of the electric heater to the maximum extent possible.Furthermore, since contact welding is detected and both relays are turned off immediately, This has the effect of increasing the safety of the electric heater.

[Brief Description of the Drawings] Fig. 1 is a block diagram of a heater drive device of an electric heater according to an embodiment of the present invention, Fig. 2 is an operation flowchart of the heater drive device, and Fig. 3 is a block diagram of the heater drive device of an electric heater according to an embodiment of the present invention. Flowchart for turning on the relay in synchronization with the zero point of the AC power supply,
Figures 4 (A) to (D) and Figures 6 (A) to (D) are timing charts of the same heater drive device, respectively, and Figure 6 shows the relays that are synchronized with the zero point of the AC power supply of the heater drive device. Flowchart for turning off the
) are the timing charts of the same heater drive device, respectively.
Fig. 8 is a block diagram of a heater drive device of an electric heater according to another embodiment of the present invention, Fig. 9 is an operation flowchart of the same heater drive device, and Fig. 10 is a block diagram of a heater drive device of an electric heater according to another embodiment of the present invention. 11 is an operation flowchart of the heater drive device, FIG. 12 is an operation flowchart of the heater drive device for an electric 7!0 heater according to another embodiment of the present invention, and FIG. 13 is a flowchart of the operation of the heater drive device. FIG. 1 is a block diagram of a heater drive device for a conventional electric heater. 1... Heater, 6... First relay,
7... Group second relay, 8... Drive circuit, 9
... Drive signal generation means, 1o ... AC power supply, 11 ... Power supply synchronization signal generation means, 12.
... Contact signal generation means, 13 ... Time difference measuring means, 14 ... Drive phase determining means, 16.
...Contact opening/closing means. Name of agent: Patent attorney Shigetaka Awano and 1 other person 2nd
Figure Figure Figure 1111 Figure 12 Figure 13

Claims (4)

[Claims] (1) A first relay and a second relay are connected to both ends of the heater, and a drive circuit is provided to drive these relays, and this drive circuit includes a drive signal generating means for instructing opening/closing of the relay; power supply synchronization signal generation means for generating a signal synchronized with zero volts of the AC power supply; contact signal generation means for generating a signal according to the open/closed state of the relay contact; a synchronization signal from the power supply synchronization signal generation means and the contact signal. a time difference measuring means that inputs the contact signal from the generating means and measures the time difference; a drive phase determining means that determines the drive phase of the relay based on the measurement signal of the time difference measuring means; and an output from the drive phase determining means. A heater drive device for an electric heater, comprising contact opening/closing means for opening/closing a relay contact upon receiving a signal, and opening/closing one of the two relays at around zero volts of an AC power supply. (2) The drive circuit is equipped with a timer or counter,
2. The relay according to claim 1, wherein one of the two relays is switched between the relay that opens and closes near zero volts of the AC power source and the other relay every time a predetermined time elapses or every time the relay is opened and closed a predetermined number of times. Heater drive device for electric heaters. (3) The drive circuit is equipped with a contact welding detection means that inputs the output of the contact opening/closing means and the contact signal from the contact signal generation means, and detects welding of the relay contacts based on a mismatch between the two, and when welding of the contacts is detected. 3. The heater drive device for an electric heater according to claim 1, wherein the relay that does not cause contact welding is opened and closed at around zero volts of the AC power source. (4) The heater drive device for an electric heater according to claim 1 or 2, wherein when the contact welding detection means detects welding of the contacts, both of the two relays are turned off.