JPH06301430A - Electric power controller - Google Patents

Abstract

PURPOSE:To obtain the electric power controller which generates a relatively smooth control output and is relatively low in cost as for an electric power controller which controls electric power supplied to a load. CONSTITUTION:The electric power controller consists of a power source 4 which generates voltage waveforms each having a front and a rear voltage-0 part, an opening/closing element 6 connected between the power source 4 and load 5, a counting means 8 which counts the order of control units while regarding one voltage waveform as one control unit, a setting means 9 which sets a control output set value, a determining means 10 which decides that a control unit is ON or OFF according to the counted value and set value, and a control means 11 which turns ON the opening/closing element 6 when the determining means 10 decides that the control unit is ON and thus turns ON and OFF the opening/closing element 6 in control units.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power controller for controlling the amount of power supplied from a power source to a load.

[0002]

2. Description of the Related Art Generally, as a power control system, a phase control system and a time proportional control system are known. The phase control method will be described with reference to FIGS. 8 and 9. FIG. 8 shows a circuit of the phase control system. A triac 17 is connected between the power supply 15 and the load 16. The triac 17 is on / off controlled by a phase control circuit 18.

Waveforms in the circuit of FIG. 8 are shown in FIG.
(A) shows the voltage waveform of the power supply 15, (b) shows the trigger pulse supplied to the gate of the triac 17 from the phase control circuit 18, (c) shows the voltage waveform supplied to the load. The trigger pulse of (b) is generated by the phase control circuit 18 at a time point delayed by the phase angle θ from the zero cross point of the power supply voltage. The triac 17 turns on when this trigger pulse is supplied, and continues to be on until the holding current becomes zero. As a result, the load 16
Is supplied with the voltage waveform shown in (c).

The area of the voltage waveform supplied to the load 16 can be changed by changing the phase angle θ of the trigger pulse. Therefore, the amount of electric power supplied to the load 16 can be controlled by controlling the phase angle θ of the trigger pulse generated by the phase control circuit 18. This phase control method has an advantage that smooth control can be performed, but on the other hand, the following (1) to
It has the drawback of (4). (1) The structure of the control circuit is complicated and the cost is high. (2) Noise occurs due to the rising of the current at the time of the trigger. (3) It adversely affects the power supply. (4) Control accuracy is low because the control output and the phase angle are not proportional.

Since the phase control system has the drawbacks described above, the time proportional control system is usually used for the electric power control of the heater. This time proportional control method will be described with reference to FIGS. FIG. 10 shows a circuit of the time proportional control system. A relay contact 20 is connected between the power supply 15 and the heater 19, which is a load. The relay contact 20 is on / off controlled by a control circuit 21.
In this time proportional control method, a certain fixed time is set as a proportional time, and the power supplied to the load is controlled by changing the ON / OFF ratio of the relay contact 20 within the proportional time.

Waveforms in the circuit of FIG. 10 are shown in FIG. (A) shows the ON / OFF state of the relay contact 20 by the control circuit 21, (b) shows the voltage waveform of the power supply 15, and (c) shows the voltage waveform supplied to the load 19. In the example shown in the figure, the control output is 50%, and as shown in (a), the relay contact 20 is turned on for a period of 1/2 of the proportional time, and the remaining 1/2 period of the proportional time continues. The relay contact 20 is turned off. As a result, the power supply 1 shown in (b) is
The voltage waveform of 5 is supplied to the load only during the ON period of the relay contact 20, and the load 19 is supplied with the output voltage having the waveform shown in (c).

This time proportional control system has the advantages that (1) the control circuit is simple and therefore the cost is low, and (2) the DC power source can be controlled, but on the other hand,
It has drawbacks such as (1) control is not smooth, (2) noise is generated when the relay contacts are opened and closed.

[0008]

As described above,
The phase control method and the time proportional control method have advantages and disadvantages, respectively. In addition, in order to control the electric power of the heater, a time proportional control method is usually used in consideration of the advantages and disadvantages of the above control methods. However, when this time proportional control method is applied to the electric power control of the heater, the following problems occur. The problem will be described with reference to FIGS. 12 and 13.

FIG. 12 is a conceptual diagram for explaining heat conduction between the heater and the object to be heated. The heater 19 is configured by accommodating a heater wire 23 in a heater outer wall 22 and filling a space between the heater outer wall 23 and the heater wire 23 with an insulator 24. An object to be heated 25 is placed in contact with or close to the heater 19. Heater wire 2
When electric power is supplied to 3, the temperature of the heater wire 23 rises, and this temperature is transmitted to the object to be heated 25 through the insulator 24 and the heater outer wall 23.

FIG. 13 is a graph showing a state in which the temperature of each portion in FIG. 12 changes with time. The power supplied to the heater 19 is turned on as shown in (a).
When turned off, the temperature of the heater wire 23 is
It goes up and down in synchronization with OFF as shown in (b). This temperature is transmitted to the heater outer wall 22 by the insulator 24. As a result, the temperature of the heater outer wall 22 also changes to the heater wire 24.
As shown in (c), it goes up and down according to the temperature change. If the object to be heated has a sufficiently large heat capacity,
The temperature of the object to be heated 25 becomes substantially constant as shown in (d).

As is clear from FIG. 13, the temperature change of each portion gradually decreases in amplitude as it is transmitted from the heater wire 23 to the outside, and the temperature also decreases at the same time. Here, if the heat capacity of the object to be heated 25 is sufficiently large, the temperature of the object to be heated 25 can be kept substantially constant as shown in (d) even by the time proportional control method. However, when the heat capacity of the object to be heated 25 is small, its temperature fluctuates according to the heater output.

It is also known that the life of the heater 19 is generally determined by the maximum temperature of the heater wire 23 and thermal shock due to the amplitude of the temperature change. Therefore, when the time proportional control system is adopted, the heater wire 23 is
As shown in FIG. 13B, since the amplitude of temperature change is large and the maximum temperature is also high, the life thereof is short. In view of the above points, an object of the present invention is to make a power control device that supplies power to a load low in cost and obtain a smooth control output.

[0013]

The power control method executed by the power control apparatus of the present invention will be described below. The present invention uses, as a power supply, a power supply in which one voltage waveform has a zero voltage portion before and after the waveform, and this voltage waveform is repeatedly output. A typical example of this power supply is shown in FIG.
The power supply shown in FIG. 2A is a commercial AC power supply, and one voltage waveform having a zero cross point 1 before and after the commercial AC power supply is repeatedly output alternately in both positive and negative directions.

The power source shown in (b) is a power source obtained by full-wave rectifying the commercial AC power source in (a), and a voltage waveform having point 2 of voltage 0 before and after that is repeatedly output. The power supply shown in (c) is a DC power supply provided with a period 3 of a voltage of 0 at a predetermined interval to form a rectangular waveform, so that a voltage of 0 is provided before and after the rectangular waveform.
The rectangular waveform having the point 3 is repeatedly output.

In the following description, the power source (a) is used.
However, the present invention can use the power supplies shown in (b) and (c) instead. Furthermore, the power supply is not limited to those shown in (a) to (c), and any power supply can be used as long as it is a power supply that repeatedly outputs a voltage waveform having a voltage 0 portion before and after. However, similarly, the present invention is applicable.

FIG. 3 shows an example of the control system of the power control apparatus of the present invention. In this example, one voltage waveform of 1/2 cycle of the AC power supply having the zero cross points 1 before and after is set as one control unit for performing power control. For convenience of explanation, each control unit is sequentially numbered. Also, the resolution for power control is set. In the illustrated example, the resolution is set to 1/100 in order to control the amount of power in 1% steps.

The reciprocal of this resolution is one control cycle. In the illustrated example, one control cycle is formed by 100 control units of 1 to 100. When the frequency of the power source is 50 Hz, one control cycle is 1 second and one control unit cycle is 10 ms. The power control device of the present invention, when the switching element provided between the power supply and the load is turned on, the voltage 0 before one control unit
The switching element is controlled to be turned on and off so as to be turned on from the time point of (1) to the time point of the rear voltage 0. Then, the power control is performed by controlling the number of one control unit to be turned on within one control cycle in accordance with the control output set value.

The relationship between the control unit and power control will be described with reference to FIG. (A) of a figure shows the voltage waveform of a power supply. In this example, 100 control units of 1 to 100 are set as one control cycle,
The resolution is 1/100. (B) of the figure shows a control unit turned on by the switching element when the control output set value is 50%. This (b) also shows the voltage waveform supplied to the load.

In this voltage waveform (b), every other control unit 1, 3, 5 ... Is turned on, and the remaining control units 2, 3.
4, 6 ... are turned off. As a result, 50 control units out of 100 control units are supplied to the load within one control cycle, so that the amount of power supplied to the load is 5
It is controlled to 0%. And according to this control method, 1
Since 50 1 control units are evenly arranged and supplied to the load within 1 control cycle as short as a second, smooth control can be obtained.

Therefore, when this electric power control method is used for heating the above-mentioned heater, the cycle and amplitude of the temperature change of the heater wire become small, and the maximum temperature of the heater wire can be lowered, so that the heater The life of the wire can be extended. In the voltage waveform of (b) described above, the control units 1, 3, 5, ... That are turned on are all of positive polarity. When the power supply circuit includes a transformer and the like, the same number of positive and negative polarity control units are output so that the power supply is not adversely affected.

In consideration of this point, the power control apparatus of the present invention may output the same number of positive and negative control units. FIG. 6C shows an example in which the same number of positive polarity and negative polarity control units are output when the control power amount is 50%. In the voltage waveform of (c), two adjacent control units of positive and negative polarities are set as one set, and this set is turned on every other set.

In FIG. 3C, the control units 1 and 2 are turned on, the following control units 3 and 4 are turned off, and the control units 5 and 6 are turned on. After that, by repeating this, 1
In the control cycle, 50 control units out of 100 control units are supplied with power, and the amount of power supplied to the load is controlled to 50%. Further, the smoothness of the control is slightly inferior to the example shown in (b), but still, much smoother control can be obtained as compared with the conventional time proportional control system.

Next, an example in which the control output set value is set to 5% is shown in (d). This (d) voltage waveform turns on one control unit 1, 21, 41, 61, 81 for every 20 control units. Therefore, since 5 control units out of 100 control units are supplied within one control cycle, the amount of power supplied to the load is controlled to 5%. Also in the voltage waveform of FIG. 7D, only the positive control unit is supplied to the load. On the other hand, FIG. 6E shows an example in which the control output set value is set to 5% and the control units of positive polarity and negative polarity are output in substantially the same number.

When the control output set value is 5%, the number of control units turned on in one control cycle is an odd number. For this reason, the number of positive and negative polarities cannot be made completely the same within one control cycle. The voltage waveform shown in FIG. 6E has a single control unit 8 for one pair of control units 1 and 2, 41 and 42 adjacent to each other.
Add 1. The electric energy by this independent control unit 81 is
Since the amount of electric power by the two control units 1 and 2, 41 and 42 is 1/2, in order to make the control outputs even in time, the off period following the single control unit 8 is normally set. It is good to set it to 1/2 of the off period.

Even if an attempt is made to output the same number of positive polarity control units and negative polarity control units, if the control output set value is odd, the number of one control unit in one control cycle will be odd. Therefore, the positive and negative numbers are not equal within one control cycle. In such a case, when it is desired to perform control with exactly the same number of positive and negative numbers, the positive and negative numbers can be made completely equal by combining the control period with a large number of positive numbers and the control period with a large number of negative numbers.

Further, when the control output set value is set to 5%, the number of control units turned on in one control cycle decreases, so that one adjacent control unit is set as shown in FIG. There is no need to do it. Therefore, as shown in FIG. 6F, one positive and one negative control unit may be output at appropriate intervals. In this way, smooth control equivalent to that shown in (d) can be obtained.

The case where the control output set values are 50% and 5% has been described above. Even when the control output set value is any other value, the control unit to be turned on can be set according to the procedure described above. Also,
The order of turning the voltage waveforms on and off is not limited to that shown in FIG. 4, and various changes are possible.

In order to execute the power control described above,
According to the present invention, one voltage waveform has a zero voltage portion before and after the waveform, and the voltage waveform is repeatedly output.
A switching element connected between the power source and the load, a counting means for counting the order of voltage waveforms sequentially supplied by the power source, a setting means for setting a power value to be supplied to the load,
A deciding means for deciding on or off based on the count value of the counter and the set value of the setting means, and when the deciding means decides to turn on, the switching element is turned on to generate one voltage waveform as a voltage. A power control device is configured by a control unit that energizes during the period from 0 to 0 and turns off the switching element when it is determined to be off.

[0029]

According to the power control device of the present invention, since power control can be performed for each control unit within one control cycle in accordance with the control output set value, a smooth control output can be obtained. A power control device that does not generate noise due to opening and closing of a power supply can be obtained at low cost.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, the power source shown in FIG.
A commercial AC power supply as shown in is used. This power supply
One voltage waveform having a zero cross point 1 before and after that is repeatedly output alternately in both positive and negative directions. In this embodiment,
The frequency of this power supply is 50 Hz, and the resolution is 1/100, 1
The control cycle is 100 control units.

FIG. 1 shows a circuit of the power control device. Power supply 4
The semiconductor switch 6 is connected between the load 5 and the load 5. A triac is used as the semiconductor switch 6. The load 5 is a heater. Zero point detection means 7 connected to the power supply 4
Outputs a signal to the counter 8 each time the zero cross point 1 of the voltage waveform of FIG.

The counter 8 counts the signal output from the zero point detecting means 7, and the count value is counted by the control means 1.
Output to 1. This counter 8 is reset when its count value exceeds the reciprocal of the resolution, that is, 100, and is reset to 0.
Becomes the value of. The control means 11 includes setting means 9 for setting the amount of electric power supplied to the load 5 and turning on / off the semiconductor switch 6.
A table 10 for determining the off state is connected.

The control means 11 reads the control output set value set in the setting means 9 and the count value of the counter 8,
From these values, the semiconductor switch 6 is selected from the table 10 using these values.
Read on / off of. Then, when the read result is ON, the semiconductor switch 6 outputs a trigger pulse as shown in FIG. 5B. When it is off, no trigger pulse is output.

When the trigger pulse is supplied, the semiconductor switch 6 is turned on and starts supplying power to the load 5. Since the triac of the semiconductor switch 6 keeps the energized state until the energized current becomes equal to or less than the holding current, the semiconductor switch 6 has the 1-state as shown in FIG.
It is turned on / off for each control unit. Table 1
An example of 0 is shown in FIG. In the table 10, the vertical axis represents the control output set value of 0% to 100%, and the horizontal axis represents the count value of the counter from 0 to 99. Then, ON or OFF is written at the intersection of the control output set value and the count value. For example, if the setting value of the setting means 9 is 33%, the semiconductor switch 6 is turned on when the count value of the counter 8 is 0, 3, 6, ... 96, and is turned off at other count values. .

Next, the operation of the circuit of FIG. 1 will be described with reference to the flowchart of FIG. In the following description, it is assumed that 50% is set as the control output set value. The operation shown in the flowchart of FIG. 7 is performed by interruption each time the zero-crossing point 1 of the voltage waveform of the power supply 4 of FIG. In step S1,
The count value of the counter 8 is incremented by 1 in response to the signal from the zero point detecting means 7.

In step S2, it is determined whether the counter 8 has overflowed. If it has not overflowed, the process proceeds to step S4. If it has overflowed, the process proceeds to step S3, the counter 8 is reset and the count value becomes zero. In this embodiment, the counter 8 is reset to 0 when 100 is counted. In step S4, the control output set value is read from the setting means 9.

In step S5, the table 10 is read, and the control means 11 reads ON / OFF of the semiconductor switch 6 from the control output set value and the count value. When the count value of the counter 8 is 0, 1, 4, 5 ... From the row of the set value 50% in the table of FIG. 6, ON is read,
Off is read at 2, 3, 6, 7 ... In step S6, the result read from the table 10 is output to the semiconductor switch 6. When ON is read from the table 10, the trigger pulse shown in FIG. 5B is output to the semiconductor switch 6. When OFF is read, the trigger pulse is not output.

When the trigger pulse is output to the semiconductor switch 6, the semiconductor switch 6 is turned on and power supply to the load is started. Since the triac of the semiconductor switch 6 continues the energized state until the energized current becomes equal to or less than the holding current, the energization of the semiconductor switch 6 is performed for each control unit as shown in FIG. 5C. It will be. Further, when the trigger pulse is not supplied, the semiconductor switch 6 is not energized.

In the output shown in FIG. 5 (c), 50 control units are supplied to the load for every 100 control units in one control cycle, so that 50% power control is performed. . Even when the control output set value is set to another value, the same operation as described above is performed. For example, when the control output set value is set to 25%, the control means 11
ON / OFF is read out from 25% of the table 10 of FIG. 6 corresponding to the count value.

According to this embodiment, one control cycle is composed of 100 control units at a power supply frequency of 50 Hz, so that power control with a fine precision of 1/100 resolution is possible within one control cycle of a short period of 1 second. It will be possible. Further, since one control unit can be arranged substantially evenly within the period of 1 second, smooth control is performed. Therefore, especially when the load is a heater, the temperature change of the object to be heated can be reduced. At the same time, since the amplitude of the temperature change of the heater wire can be reduced and the maximum temperature can be lowered, the life of the heater wire can be extended.

Since the semiconductor switch 6 is turned on and off at the time when the voltage is 0,
No noise is generated at the time of switching,
The adverse effect on the power supply can also be reduced. further,
Since the power control output is determined by the number of one control unit turned on, the control output set value and the power control output can be perfectly matched, and the control accuracy is high. Since the control circuit can be composed of a microcomputer, a power control device with a simple circuit and low cost can be obtained.

Although one embodiment of the present invention has been described above, the device for carrying out the present invention is not limited to the circuit shown in FIG. The present invention can be variously modified within the scope described in the claims. For example, in the example described above, a table is used as the determining means for determining the on / off order of the semiconductor switches. An appropriate calculation formula is prepared in place of this table, and each time the voltage 0 of the power supply is detected, calculation is performed according to the control output set value and the count value to determine whether the semiconductor switch is on or off. Is also good.

Further, instead of detecting the voltage 0 point of the power source and advancing the count value of the counter, it is also possible to control ON / OFF of the semiconductor switch by advancing the count value using a timer. In this case, the count value of the timer and the voltage 0 point of the power supply are not synchronized. For this reason, SSR with 0 cross function as a semiconductor switch
(Solid state relay) for voltage waveform 1
Turn on / off for each control unit.

[0044]

According to the present invention, it is possible to obtain a power control device which can obtain a smooth control output at low cost and which does not generate noise due to opening and closing of a power supply.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit of an embodiment of the present invention.

FIG. 2 is a graph showing a power supply used in the present invention.

FIG. 3 is a graph illustrating power control of the present invention.

FIG. 4 is a graph showing a relationship between a control unit and power control according to the present invention.

5 is a graph showing a waveform of each part of FIG.

FIG. 6 is a table used in the circuit of FIG.

7 is a flowchart illustrating the operation of the circuit of FIG.

FIG. 8 is a circuit diagram of a conventional phase control method.

9 is a graph showing a waveform of each part of FIG.

FIG. 10 is a circuit diagram of a conventional time proportional control system.

11 is a graph showing the waveform of each part of FIG.

FIG. 12 is a conceptual diagram illustrating heat conduction between a heater and an object to be heated.

FIG. 13 is a graph showing a temperature change in each part of FIG.

[Explanation of symbols]

 4 ... Power source 5 ... Load 6 ... Semiconductor switch 7 ... Zero point detection means 8 ... Counter 9 ... Setting means 10 ... Table 11 ... Control means 19 ... Heater 22 ... Heater outer wall 23 ... Heater wire 24 ... Insulator 25 ... Heated object

Claims (1)

[Claims] 1. A voltage waveform has a zero voltage portion before and after the waveform, and a power source for repeatedly outputting this voltage waveform, a switching element connected between this power source and a load, and said power source. Counting means for counting the order of sequentially supplied voltage waveforms, setting means for setting a power value to be supplied to a load, deciding means for deciding ON or OFF according to the count value of the counter and the setting value of the setting means, and When it is determined to be on by the determining means, the switching element is turned on so that one voltage waveform is energized in the period from voltage 0 to voltage 0, and when it is determined to be off, the switching element is turned off. A power control device comprising a control means.