JP2003248520A - Power control circuit and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control circuit and method of a semiconductor heater which can control rush current to the semiconductor heater on power-on, prevent excessive generation of electric current, and quickly bring heating effect. <P>SOLUTION: In a semiconductor heater power control circuit which electrical resistance increases with rise of temperature, electricity is turned on for a short time within the limit that a breaker, etc., does not activate just after power on, the electricity is turned on again after the voltage is set so that the electric current is applied as much as possible within the limit of the allowable maximum electric current based on the result which detects a value of the electric current in the meantime, and the value of the electric current is measured after that and the voltage is sequentially controlled to be close to a steady value. Besides, the control circuit includes a phase control method electric current/voltage control means, or a semiconductor device such as a triac. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control circuit and method, and more particularly to a semiconductor heater control circuit for controlling an inrush current value when power is turned on and preventing an excessive current generation, and a control method therefor. is there.

[0002]

2. Description of the Related Art A heating system is indispensable as a means for improving the living environment. However, oil stoves and gas stoves have recently been starting to grow due to the need for indoor air ventilation or the problems of air pollution and natural environment pollution. Electric floor heating and panel heater type heating equipment that can efficiently warm the body, are safe, and have little indoor air pollution are drawing attention. Compared to hot water type floor heating, electric floor heating does not require equipment such as boilers and installation places for them, and has features such as short delivery time because the construction is relatively easy. In addition to indoor heating, various hygienic heaters are also used in, for example, snow melting systems, greenhouses for growing plants, heating appliances for pets, and the like. As these heating elements, in recent years, a semiconductor heater, which has a large resistance value when the temperature is raised, has been attracting attention. The semiconductor heater is composed of particulate conductive carbon, which is a resistance heating element, and polymer resin particles dispersed and mixed therein. When the semiconductor heater is in a low temperature state, the resin particles shrink and become conductive carbon. Although the current easily flows, that is, the resistance is low, the resin particles expand when heat is generated by energization, resulting in a large distance between the conductive carbon particles and a narrow current flow path, resulting in a resistance value. It has the property of increasing. FIG. 6 shows the current / voltage characteristics of this semiconductor heater and a conventional nichrome wire heater. The thick line 11 shows the semiconductor heater and the thin line shows the nichrome wire heater 10.
As is clear from this figure, in the nichrome wire heater 10, the current increases proportionally as the voltage rises, whereas in the semiconductor heater heater 11, the current decreases above a certain voltage Vc. This is the semiconductor heater 11,
Unlike the conventional nichrome wire type heating element, it has the property of increasing the electric resistance with heat generation, so that the temperature control is relatively easy and the safety is excellent. FIG. 7 shows an example of the relationship between the current and the passage of time showing this situation. It is understood that a large current flows immediately after the power is turned on because the electric resistance is small, but the current rapidly decreases as the temperature rises. I can do it.

As described above, in the semiconductor heater, since the resistance value increases as the temperature rises, the current decreases as the temperature rises, and as a result, there is self-control in which a constant temperature is maintained. However, in the heater device using the semiconductor heater, a large current flows as an inrush current when the power is turned on in a low temperature state at the start of activation. One of the features of the semiconductor heater is that a rapid heating effect is brought about because the temperature rises rapidly due to the generation of this inrush current.
A power supply facility with a large current capacity that can withstand inrush current is required as a power supply. Usually, not only for general households, commercial power supply is equipped with a breaker for preventing current generation above a certain value to maintain safety, and the inrush current allowable value is also limited. If the breaker limit current value is increased in order to cope with the occurrence of a large inrush current, there is a problem that the power contract amount is accordingly increased and the power supply and demand cost is increased.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problem when using a semiconductor heater as described above, and performs control suitable for the characteristics of the semiconductor heater and An object of the present invention is to provide a semiconductor heater control circuit and method that can prevent an increase in power supply and demand costs without damaging the power supply.

[0005]

In order to solve the above-mentioned problems, the invention according to claim 1 is a power control circuit for supplying power to a heating element whose electric resistance increases as temperature rises. Current detecting means for detecting the current value supplied to the device, current controlling means for controlling the current value, temperature detecting means for detecting the temperature of the heating element, and information from the current detecting means and the temperature detecting means. Power control means for controlling the current control means on the basis of the power supply means, the power control means supplies all the electric power from the power supply to the heating element for a predetermined time after the power is turned on, and as a result of the supply, the current When it is determined that the current value detected by the detection means exceeds a predetermined current value, the total current is temporarily cut off via the current control means, and then the phase of the power source is controlled to control the current detection means. The current value of the Luo and controls the voltage to be a predetermined current value. When the power is turned on normally, a large inrush current flows to the load. At this time, when the semiconductor heater is used as the load, the electric resistance increases as the temperature rises, and as a result, the current gradually decreases. However, if a specified current value continues to flow for a predetermined time at the time of entry, the breaker rating will be exceeded and the breaker will fall. 10 to prevent this
When the current value is detected when 0% power supply voltage is applied and it is determined that the breaker rating is exceeded, the power supply is turned off once and then the voltage is gradually increased by phase control.
Make sure the current flows near the breaker rating. Then, as the heater warms up, the resistance value rises, and the current value falls, the voltage is increased by phase control so that the current flows near the rated value of the breaker.
Repeat until the output of. According to the invention, the power control means supplies all the electric power from the power supply to the heating element for a predetermined time after the power is turned on, and the current value detected by the current detection means as a result of the supply is a predetermined current. When it is determined that the value exceeds the value, the total electric power is temporarily cut off via the current control means, and then the phase of the power source is controlled so that the current value from the current detection means becomes a predetermined current value. Since the voltage is controlled, it is possible to effectively utilize the electric power at the time of rush, and to efficiently supply the electric power to the heater without dropping the breaker.

In the invention of claim 2 or 9, the output voltage controlled by the current control means so that the current value from the current detection means becomes a predetermined current value becomes equal to the power supply voltage. It is an effective means of the present invention that the temperature is gradually controlled to rise. When a current flows and the temperature of the semiconductor heater increases, the resistance value of the semiconductor heater increases and the current decreases. However, in order to maintain a constant temperature as the heater, it is necessary to flow a certain constant current. When the resistance value increases and the current decreases, it is necessary to increase the voltage and secure a predetermined current. Therefore, it is effective to control the voltage supplied to the heater gradually as the temperature rises. According to the technical means, the output voltage controlled by the current control means so that the current value from the current detection means becomes a predetermined current value is gradually controlled to increase until it becomes equal to the power supply voltage. Therefore, it is possible to suppress the decrease in the heater temperature and to moderate the change in current.

In the invention according to claim 3 or 10, the power control means controls the current control means at a predetermined time interval to supply or cut off a voltage to the heating element to control the temperature of the heating element. Controlling is also an effective means of the present invention. Here, in order to keep the heater temperature constant, there is a method of controlling the power supplied to the heater by turning it on and off. In this case, the relationship between the ON / OFF time and the temperature is checked in advance, and the O
The temperature is controlled by repeating N / OFF. According to the technical means, the power control means controls the temperature of the heating element by controlling the current control means at a predetermined time interval to supply or cut off voltage to the heating element. An inexpensive heater can be realized without requiring any means. In the invention according to claim 4 or 11, it is also effective that the power control means controls the current control means based on the information from the temperature detection means to supply or cut off a voltage to the heating element. It is a means. The temperature is detected by the temperature detecting means provided in the heater, and the electric power to the heater is turned on / off to be controlled thereby.
According to the technical means, the power control means controls the current control means based on the information from the temperature detection means to supply or cut off the voltage to the heating element, so that accurate temperature control is possible. . In the invention according to claim 5, it is also an effective means of the present invention that the power control means is controlled so as to energize a part of the AC power supply cycle waveform. According to such technical means, by the phase control,
Since a part of the alternating-current power supply cycle waveform is energized, zero-cross control can be performed, and generation of noise due to control can be eliminated.

In the invention according to claim 6, it is also an effective means of the present invention that the power control means includes a thyristor. According to such a technical means, the power control can be performed by the logic signal by using the thyristor. According to a seventh aspect of the present invention, the power source has means for converting to direct current, and the power control means comprises:
The pulse modulation method of the DC chopper is also an effective means of the present invention. According to this technical means, there is a pulse modulation method of a DC chopper as a method of converting an AC voltage into a DC voltage and controlling the electric power using the DC voltage. By using this method, the temperature can be easily controlled by modulating the pulse width. In the invention according to claim 8, in a power control method for supplying power to a heating element whose electric resistance increases as temperature rises, current detection means for detecting a current value supplied to the heating element, and the current value. Current control means for controlling the temperature of the heating element, temperature detection means for detecting the temperature of the heating element, and power control means for controlling the current control means based on information from the current detection means and the temperature detection means. The power control means supplies all the electric power from the power supply to the heating element for a predetermined time after the power is turned on, and as a result of the supply, the current value detected by the current detection means exceeds a predetermined current value. In such a case, the total power is once cut off via the current control means, and then the phase of the power source is controlled to control the voltage so that the current value from the current detection means becomes a predetermined current value. And wherein the door. According to this invention, the same effect as that of the first aspect can be obtained.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings. However, the constituent elements, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely explanatory examples, not the gist of limiting the scope of the present invention thereto, unless specifically stated. .
1 is a block diagram showing an embodiment of a semiconductor heater control circuit 1 according to the present invention. In the figure, reference numeral 2 is a general household AC power supply, and is connected via a breaker 3 to a load 4 such as a semiconductor heater to be controlled. The control circuit 1 shown in this example includes a current sensor 5 that detects a current supplied to the semiconductor heater 4, a semiconductor element (for example, a thyristor or a triac) 6 that controls a current flowing,
A control unit 7 including a CPU for receiving these signals and generating control signals is provided. Further, in order to precisely control the temperature of the load device 4 such as a semiconductor heater, the load device 4 is provided with a temperature sensor 8 such as a thermocouple as a temperature detecting element, and the output of this sensor is output from the control unit 7. It is supplied to the CPU. Figure 2
Shows an energization waveform diagram when so-called phase control is used as an example of the current control, and in the same figure (a) by the input method of the gate control signal of the semiconductor element (thyristor, triac) 6 of FIG. The current value flowing can be controlled by energizing for a certain period of time by using the zero-cross point of the rising portion of the AC signal waveform as a trigger as in the rising reference method shown in FIG. Moreover, if a gate turn-on / off switch (GTO) thyristor is used, phase control of the falling reference method of FIG. 7B or the central reference method of FIG. 7C, which is excellent in fundamental wave utilization efficiency, becomes possible. In order to simplify the control, the half-wave waveform energization method shown in FIG. 3 may be adopted. The energization timing and energization time of each waveform are determined and controlled by the control unit 7 including the CPU.
Further, in recent years, it has been considered to accumulate and use a solar cell or nighttime electric power in a battery. When such a DC power supply is used, control of the supplied electric power is performed, for example, as shown in FIG. Such a DC chopper method is useful. That is, as an example, as shown in FIGS. 7A and 7B, the total current may be controlled by connecting and disconnecting the DC current. (A) is the time tO of the energizing pulse generated in a constant cycle.
A method of changing the N time (pulse width) to control the total current (PWM; Pulse Width Modulation), or as shown in FIG. 7B, either the pulse on-time or the pulse off-time is set to be constant. A method (PFM; Pulse Frequency Modulation) or the like in which the total current is controlled by changing the repetition period according to the input may be suitable.

FIG. 5 is a flow chart showing an example of the semiconductor heater control method according to the present invention. In the procedure shown in this example, when the power is first turned on, the power is supplied at a voltage of 100% for a short time such that the current interrupting means such as a breaker does not operate (step 1). If a large current flows for a short time, there is no danger, but if an excessive current is likely to occur, it may be preferable for safety to set the initial voltage to a predetermined low voltage. In step 1, the current value is detected by the current sensor 5 for a short time, for example, when an initial current is supplied for 0.5 seconds or less, and the value is digitized to C
The current taken in by the PU and compared to the initial energization voltage is compared with the specified value to calculate the voltage when the power is turned on again. That is, since the semiconductor heater is rapidly heated by a large rush current at the initial stage of power-on and a quick heating effect can be obtained, it is more effective to supply a current as large as possible within an allowable range. Therefore, during the initial short-time energization, the rush current value with the maximum allowable range is calculated, and the voltage is set to be that current (steps 2 and 3). Then, re-energization is performed (step 4), and at the same time, the current is detected (step 5). Generally, the set voltage at the time of re-energization is set to a relatively small voltage value, but the temperature of the semiconductor heater rises with re-energization and the electric resistance rapidly increases. Since the rapid heat retention effect decreases, the energizing current value is continuously detected thereafter (step 5), and the voltage value to be applied is calculated while comparing it with the preset specified current value (step 6). As a result of the comparison, if the current is a prescribed value, for example, smaller than the maximum allowable current value, the voltage value is increased (step 8) and the process returns to step 5 and then step 6. If the result of comparison in step 6 is that the current is larger than the specified value, the voltage is dropped and steps 5 and 6 are repeated. Generally, the initial setting voltage when the power is turned on again should be significantly reduced, so normally step 5, step 6, step 8, and step 5 are cyclically repeated, and the electric resistance increases as the temperature rises. Therefore, the applied voltage is sequentially changed to increase, and after the rush current period, the applied voltage value becomes 100% and the steady state is achieved.

In the above description, the control method has been shown focusing on the inrush current limitation at the initial stage of power-on. However, in the normal operation, the CPU controls the preset temperature adjustment and quick heating. It goes without saying that you can do it. Further, the above-mentioned embodiment is an example,
Other various modifications are possible. For example, the heating element to be used is not limited to the semiconductor heater, but can be widely applied to a heater that similarly generates an inrush current.

[0012]

Since the present invention is constructed as described above, the present invention has the following effects. That is, in the invention according to claims 1 and 8, the power control means is
After the power is turned on, all the electric power from the power source is supplied to the heating element for a predetermined time, and when it is determined that the current value detected by the current detection means exceeds the predetermined current value as a result of the supply, the current control means Voltage is controlled so that the current value from the current detection means becomes a predetermined current value by temporarily shutting off all the electric power via the In addition, it is possible to efficiently supply electric power to the heater without dropping the breaker. In the invention according to claims 2 and 9, the output voltage controlled by the current control means so that the current value from the current detection means becomes a predetermined current value gradually increases until it becomes equal to the power supply voltage. Since the temperature is controlled, it is possible to suppress a decrease in the heater temperature and to moderate the change in current. In the inventions according to claims 3 and 10, the power control means controls the temperature of the heating element by controlling the current control means at a predetermined time interval to supply or cut off voltage to the heating element. An inexpensive heater can be realized without the need for temperature detecting means.

According to the present invention, the electric power control means controls the current control means based on the information from the temperature detection means to supply or cut off the voltage to the heating element. Temperature control is possible. Claim 5
In the invention described above, since a part of the AC power supply cycle waveform is energized by the phase control, zero-cross control can be performed and the generation of noise due to the control can be eliminated. In the invention described in claim 6, by using the thyristor, the power can be controlled by the logic signal. In a seventh aspect of the invention, as a method of converting an alternating voltage into a direct current and controlling the electric power using the direct current voltage, there is a pulse modulation method of a DC chopper. By using this method, the temperature can be easily controlled by modulating the pulse width.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a main part of a semiconductor heater control circuit of the present invention.

2 (a), (b), (c) are phase control waveform diagrams shown as an example of a current / voltage control method in the present invention.

FIG. 3 is a half-wave rectification type phase control waveform diagram showing an example of a current / voltage control method in the present invention.

4A and 4B are diagrams showing a current / voltage control example of a DC chopper / pulse system corresponding to a DC power supply as an example of a current / voltage control method in the present invention.

FIG. 5 is a flowchart showing an example of a semiconductor heater control method according to the present invention.

FIG. 6 is a diagram showing an example of the relationship between current and voltage of a semiconductor heater.

FIG. 7 is a diagram showing a relationship between current and voltage of a semiconductor heater.

[Explanation of symbols]

1 Semiconductor heater control circuit 2 AC power supply 3 breakers 4 panel heater (semiconductor heater) 5 Current sensor 6 Semiconductor elements (thyristors, triacs, etc.) 7 control unit 8 Temperature sensor

Claims (11)

[Claims] 1. A power control circuit for supplying electric power to a heating element whose electric resistance increases as the temperature rises. Current detecting means for detecting a current value supplied to the heating element, and controlling the current value. Current control means, temperature detection means for detecting the temperature of the heating element, and power control means for controlling the current control means based on information from the current detection means and the temperature detection means; When the control means determines that the current value detected by the current detection means exceeds the predetermined current value as a result of supplying all the electric power from the power supply to the heating element for a predetermined time after the power is turned on, The voltage is controlled so that the current value from the current detection unit becomes a predetermined current value by once shutting off all the electric power via the current control unit and then controlling the phase of the power supply. Power control circuit. 2. The output voltage controlled by the current control unit so that the current value from the current detection unit becomes a predetermined current value is gradually increased and controlled until it becomes equal to the power supply voltage. The power control circuit according to claim 1, wherein the power control circuit is a power control circuit. 3. The power control means controls the temperature of the heating element by controlling the current control means at a predetermined time interval to supply or cut off a voltage to the heating element. The power control circuit according to item 1 or 2. 4. The electric power control means controls the current control means based on information from a temperature detection means to supply or cut off a voltage to the heating element. Power control circuit. 5. The power control circuit according to claim 1, wherein the power control means is controlled so as to energize a part of an AC power cycle waveform. 6. The power control circuit according to claim 1, wherein the power control means includes a thyristor. 7. The power source includes means for converting to direct current, and the power control means is a DC chopper pulse modulation system.
The power control circuit according to claim 1. 8. A power control method for supplying electric power to a heating element whose electric resistance increases as the temperature rises, the current detecting means detecting a current value supplied to the heating element, and controlling the current value. Current control means, temperature detection means for detecting the temperature of the heating element, and power control means for controlling the current control means based on information from the current detection means and the temperature detection means; When the control means determines that the current value detected by the current detection means exceeds the predetermined current value as a result of supplying all the electric power from the power supply to the heating element for a predetermined time after the power is turned on, The voltage is controlled so that the current value from the current detection unit becomes a predetermined current value by once shutting off all the electric power via the current control unit and then controlling the phase of the power supply. Power control method for. 9. The output voltage controlled by the current control unit so that the current value from the current detection unit becomes a predetermined current value is gradually controlled to increase until it becomes equal to the power supply voltage. The power control method according to claim 8, which is characterized in that: 10. The power control method according to claim 8, wherein the power control means controls the current control means at a predetermined time interval to supply or cut off a voltage to the heating element. . 11. The electric power control means controls the current control means based on information from the temperature detection means to supply or cut off a voltage to the heating element. Power control method.