JPH08297429A - Ac load applying controlling device - Google Patents

Abstract

PURPOSE: To reduce the input current and higher harmonic current, and also to precisely control the index value. CONSTITUTION: A heater 20 heating a member to be heated and a switch part 30 are connected in series across both lines of an AC power source, and a zero-cross detecting circuit 40 is also connected. A reference voltage VREF is divided by a thermister 61 and a resister R1, and a divided voltage Vr is inputted from a temperature detecting part 60 to a control part 50. The control part 50 detects the temperature of the member to be heated by the level of the divided voltage VT, and controls energizing of the heater 20 by ON-OFF control of the switch part 30 according to detected temperature, controlling ON-OFF of the switch part 30 at each cycle of the voltage waveform of the AC power source 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC load energization control device for efficiently turning on / off energization from an AC power source to a load.

[0002]

2. Description of the Related Art Conventionally, when energizing a load such as a heater from an AC power source such as a commercial power source, on / off control of energization is generally performed in order to maintain a constant index value such as temperature. . In this case, in order to reduce the inrush current when turning on,
It is often done to turn on the AC waveform at zero cross. However, since fine control is difficult with simple ON / OFF control that only turns on at zero cross, fine control with less overshoot from the index value has been performed by controlling the conduction angle of the AC waveform.

[0003]

However, when it is attempted to maintain the index values such as temperature constant by controlling the conduction angle, the waveform of the input current to the load is greatly deviated from the pulsed sine wave. turn into. Therefore, since the power factor decreases, the effective power decreases, but the effective value of the current increases and the apparent power increases, resulting in an increase in the input current. Therefore, it is necessary to use parts with a large current rating for the input parts such as electric wires, fuses, power switches, etc., which leads to an increase in the size of parts and an increase in cost.

Further, a lot of odd-order harmonic currents are included, but as shown in the international standard IEC1000-3-2 defined by IEC (International Electrotechnical Commission), mainly in Europe. Harmonic current regulations are being tightened around the world and need to be reduced. Further, since the rate of change in current when the input to the load is on is large, it has been a cause of noise generation.

An object of the present invention is to solve the above problems and to provide an AC load energization control device capable of reducing the input current and the harmonic current and finely controlling the index value.

[0006]

In order to achieve the above object, the present invention provides an AC load energization control device for controlling on / off of energization from a sine wave AC power supply to a load. Zero cross detection means for detecting zero cross of the voltage waveform, a switch interposed between the sine wave AC power supply and the load, and the switch is periodically turned on and off in a predetermined on and off pattern. Along with this, there is provided a switch control means for switching ON / OFF of the switch in synchronization with the detection of the zero cross (claim 1).

Further, in the AC load energization control device according to the present invention, there is provided index value detection means for detecting an index value relating to the load, and the switch control means has the detection index value reaching a preset value. The switch is operated up to (claim 2).

Further, the switch control means operates the switch in an ON / OFF pattern having a first ON ratio when the detection index value is smaller than a first value smaller than the set value. When the detection index value is larger than the first value and smaller than the set value, the switch is operated in an ON / OFF pattern having a second ON ratio smaller than the first ON ratio. (Claim 3).

The load is a heater for heating a member to be heated, the index value is a temperature of the member to be heated, the first value is a first temperature lower than a preset temperature,
The index value detecting means detects the temperature of the heated member (claim 4).

When the detected temperature is lower than the first temperature, the switch control means operates the switch in an ON / OFF pattern having an ON ratio of 2/3 to detect the detected temperature. Is higher than the first temperature and lower than the set temperature, the switch is operated in an ON / OFF pattern having an ON ratio of 1/2 (claim 5).

[0011]

According to the first aspect of the present invention, the energization from the sine wave AC power source to the load is periodically turned on and off in a predetermined on / off pattern, and the on / off switching of the energization is performed at zero cross. It is performed in synchronization with the detection. by this,
The current waveform supplied to the load is sine wave,
The power supplied to the load is finely controlled.

According to the second aspect of the present invention, the index value relating to the load is detected, and the energization from the sine wave AC power supply to the load is predetermined until the index value reaches a preset value. Further, it is periodically turned on / off in an on / off pattern, and energization is switched on / off in synchronization with the detection of the zero cross. As a result, the current waveform supplied to the load is made sinusoidal, and the average power supplied to the load is finely controlled until the index value reaches the set value.

According to the third aspect of the present invention, the index value related to the load is detected, and when the detected index value is smaller than the first value smaller than the set value, the load from the sine wave AC power supply is detected. Is energized in an on / off pattern having a first on ratio. When the detection index value is larger than the first value and smaller than the set value, the energization of the sine wave AC power supply to the load is an on / off pattern having a second on ratio smaller than the first on ratio. Done. The energization is switched on and off in synchronization with the detection of the zero cross. As a result, the index value quickly reaches the set value, and overshoot after reaching the set value is reduced. Further, the current waveform supplied to the load is made a sine wave, and the average power supplied to the load is finely controlled until the index value reaches the set value.

According to the present invention, the temperature of the member to be heated is detected, and when the detected temperature is lower than the first temperature, which is lower than the set temperature, the load from the sine wave AC power source is applied. Is energized in an on / off pattern having a first on ratio. Also, the detected temperature is higher than the first temperature,
When the temperature is lower than the set temperature, the sine-wave AC power supply is energized to the load in an on / off pattern having a second on ratio smaller than the first on ratio. The energization is switched on and off in synchronization with the detection of the zero cross.
As a result, the temperature of the heated member quickly reaches the set temperature, and overshoot after reaching the set temperature is reduced. Further, the current waveform supplied to the heater is made sinusoidal, and the average power supplied to the heater is controlled finely until the set temperature is reached.

According to the fifth aspect of the invention, when the temperature of the heated member is detected and the detected temperature is lower than the first temperature which is smaller than the set temperature, the load from the sine wave AC power source is applied. Energization is performed in an on / off pattern having an on ratio of 2/3. When the detected temperature is higher than the first temperature and lower than the set temperature, the energization from the sine wave AC power supply to the load is performed in an ON / OFF pattern having an ON ratio of ½. The energization is switched on and off in synchronization with the detection of the zero cross. As a result, the temperature of the heated member quickly reaches the set temperature, and overshoot after reaching the set temperature is reduced. Further, the current waveform supplied to the heater is made sinusoidal, and the average power supplied to the heater is controlled finely until the set temperature is reached.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of an embodiment of a heater control circuit to which the present invention is applied, and FIG. 2 is a timing chart showing a voltage waveform of an AC power supply 10, a zero cross signal and an operating state of a switch section 30. is there.

The heater control circuit is constructed by connecting the heater 20 and the switch unit 30 in series between both lines of the AC power supply 10 and the zero-cross detection circuit 40, and the control unit 50 controls the switch unit 30. Is controlled to control the energization of the AC power supply 10 to the heater 20. The AC power supply 10
Fuse F between the two lines and the heater control circuit
Is connected.

The heater 20 is made of a nickel-chromium alloy or the like, and heats a member to be heated such as a heating roller arranged in a plain paper copying machine adopting a heat roller fixing system or a plate arranged in a hot plate. To do. The temperature detection unit 60 detects the temperature of the member to be heated as an index value, and includes a thermistor 61 and a resistor R1 connected in series between the reference voltage V _REF and the ground, and the reference voltage V _{REF.
The divided} voltage V _{T obtained} by dividing _REF by the thermistor 61 and the resistor R1 is input to the control unit 50. The thermistor 61 is disposed in contact with the heated member,
When the temperature of the member to be heated rises, its resistance value decreases.

The switch section 30 comprises a triac 31 and a triac gate circuit 32 which supplies a gate current to the triac 31. TRIAC 31
The terminals T1 and T2 are connected to the switch terminals 301 and 302, and the gate terminal G is connected to the triac gate circuit 32, which is turned on and off depending on the presence or absence of the gate current supplied from the triac gate circuit 32. Is controlled by a gate control signal from the controller 50. Zero cross detection circuit 40
2 detects a zero cross in the voltage waveform of the AC power supply 10 as shown in FIG. 2 and outputs a short pulse zero cross signal as shown in FIG.

The control unit 50 detects the temperature of the heated member based on the level of the divided voltage V _T input from the temperature detection unit 60. In addition, a gate control signal is output to the triac gate circuit 32 according to the detected temperature to control the turn-on and turn-off of the triac 31, thereby controlling the on / off of the switch unit 30 to control the heater 2.
For controlling the energization to 0, the switch unit 30 is controlled to be turned on and off for each cycle of the voltage waveform of the AC power supply 10.

Here, the set temperature of the member to be heated is TP ₀ , the first temperature is TP ₁ , and the second temperature is TP ₂ (however, TP ₀ > TP ₁ > TP
₂ ) and the current temperature of the heated material is TP.

At this time, when TP <TP ₂ , the control unit 50 continuously turns on the switch unit 30 from the time of inputting the zero-cross signal as shown in FIG. Also, TP ₂ ≤ T
When P <TP ₁ , as shown in FIG. 2, the switch unit 30 is made to repeatedly perform the operation of turning on for two cycles and turning off for one cycle, as shown in FIG. Further, when TP ₁ ≦ TP <TP ₀ , as shown in FIG. 2, the switch unit 30 is made to repeat the operation of one cycle on and one cycle off from the time of input of the zero-cross signal.

As a result, the temperature of the member to be heated will be as shown in FIG.
Rapidly rises to reach the second temperature TP ₂ from ambient temperature TP _a, as shown in, slightly to moderately raised from the second temperature TP ₂ reaches the first temperature TP _1, the first It rises more slowly from the temperature TP ₁ and reaches the set temperature TP ₀ . Then, the set temperature TP ₀ is maintained with almost no overshoot.

FIG. 4 is a flow chart showing an example of the operation procedure of the heater control circuit.

First, the current temperature TP of the member to be heated is detected and compared with the set temperature TP ₀ (step S1), and TP <TP ₀
If not (NO in step S1), wait and TP <TP ₀
If so (YES in step S1), wait until the zero-cross signal is detected (NO in step S2), and if detected (YES in step S2), the heater 20 is energized (step S3).

Next, the temperature TP detected in step S1 and the second temperature TP ₂ are compared (step S4). If TP <TP ₂ (YES in step S4), the zero-cross signal is set to 6
The state is maintained as it is until the number of times is counted (NO in step S5), and when the number of times is counted 6 (YES in step S5), the process proceeds to step S6.

On the other hand, if TP <TP _{2 is} not satisfied in step S4 (NO in step S4), the temperature TP detected in step S1 is compared with the first temperature TP ₁ (step S4).
7) If TP ₁ ≤TP (YES in step S4), the state is maintained as it is until the zero-cross signal is counted twice (NO in step S8), and is counted twice (YES in step S8), The energization of the heater 20 is stopped (step S9).

Next, until the zero-cross signal is counted twice (NO in step S10), the state is maintained as it is and counted twice (YE in step S10).
S), and proceed to step S6.

On the other hand, in step S7, if TP ₁ ≤TP (NO in step S7), TP ₂ ≤TP <TP ₁ is satisfied, so that the zero-cross signal is counted four times (NO in step S11), it is kept as it is. If the state is maintained and counting is performed four times (YES in step S11), step S9
Then, the power supply to the heater 20 is stopped.

[0030] Then, in step S6, is compared with the current temperature TP is detected set temperature TP ₀ of the heated member, unless TP <TP ₀ (NO in step S6), and stops energizing the heater 20 Then (step S12), the process returns to step S1. On the other hand, if TP <TP ₀ (step S6)
YES), the heater 20 is energized (step S3),
Hereinafter, the above procedure is repeated.

In this way, 1 of the voltage waveform of the AC power source 10
Since the on / off of the energization of the heater 20 is controlled for each cycle, the current waveform energized to the heater 20 can be a sine wave. Therefore, the inrush current can be reduced,
Since it is possible to prevent the power factor from decreasing, it is possible to reduce the input current and the harmonic current. Also, due to the reduced input current, the fuse F used in the input circuit
In addition, since parts having a low current rating can be used as parts of other wires, power switches, noise filters, etc., the parts can be made smaller and the cost can be reduced. In addition, since the rate of change of the current at the time of turning on is small, the generated noise can be reduced.

Further, the electric power supplied to the heater 20 can be finely controlled, and the temperature can be finely controlled. Therefore, the power consumption can be minimized and the overshoot with respect to the set temperature TP ₀ can be reduced.

FIG. 5 is a circuit diagram showing another configuration example of the switch section 30 and the control section 50 in FIG. The switch unit 30 includes a solid state relay (SSR) 3 including a photo triac coupler 34, a triac 37, and the like.
3 and a transistor Q1. SSR3
In the triac 37 of No. 3, the terminals T1 and T2 are connected to the switch terminals 301 and 302, and the gate terminal G is the resistor R3.
It is connected to the switch terminal 301 via.

In the photo triac 36 of the photo triac coupler 34, the terminal T1 is connected to the gate terminal G of the triac 37, and the terminal T2 is connected to the switch terminal 302 via the resistor R2. The light emitting diode 35 of the phototriac coupler 34 has an anode connected to the power supply voltage V _CC and a cathode connected to the collector of the transistor Q1.

The base of the transistor Q1 is the CPU 52.
The emitter is connected to the ground line at the output terminal P1 of the.

The control unit 50 includes an A / D converter 51 and a CP.
It is composed of U52. The A / D converter 51 has an input terminal connected to the connection point of the thermistor 61 and the resistor R1 and an output terminal connected to the CPU 52, and outputs the analog divided voltage V _T input from the temperature detection unit 60 by the required number of bits, For example, in FIG. 5, it is converted into a digital value of 4 bits, that is, 16 steps, and output to the CPU 52.

The CPU 52 detects the temperature of the heated member based on the digital value input from the A / D converter 51. Also, a gate control signal is output from the output terminal P1 according to the detected temperature.

When a high-level gate control signal is output from the output terminal P1 of the CPU 52, the transistor Q1 is turned on, the light emitting diode 35 emits light, the phototriac 36 is turned on, and the resistor R2, the phototriac 36, the resistor A current flows through R3, which turns on the triac 37 and energizes the heater 20.

Then, as in the case of FIG.
3 is controlled by controlling ON / OFF of the switch unit 30 for each cycle of the voltage waveform of FIG.
The member to be heated is heated as shown in FIG. by this,
Also in the case of FIG. 5, the same effect as that of FIG. 1 can be obtained.

It should be noted that, instead of the SSR 33, for example, a mechanical relay including a contact portion of a normally open contact and a coil portion may be used. In this case, the same effect can be obtained by connecting the coil portion instead of the light emitting diode 35 and connecting the contact portion instead of the triac 37.

FIG. 6 is a circuit diagram showing another configuration example of the control unit 50 in FIG. 1, only the control unit 50 and the temperature detection unit 60 are shown, and other components are omitted. In FIG. 6, the control unit 50 includes comparators C1, C2, C3 and a CPU.
It is composed of 53.

The comparators C1, C2 and C3 are inverted inputs.
The force terminal is not inverted at the connection point between the thermistor 61 and the resistor R1.
Each input terminal has a reference voltage V₁, V₂, V₃(However, V₁
<V ₂<V₃) Generating reference voltage generators 54, 55, 5
6, the output terminal is the input terminal P1 of the CPU 53, respectively.
1, P12, P13.

Then, the comparators C1, C2, C3
Outputs a high-level signal from the output terminal when the input voltage level to the inverting input terminal is less than the input voltage level to the non-inverting input terminal, and the input voltage level to the inverting input terminal is When the input voltage level is exceeded, a low level signal is output from the output terminal.

That is, the comparators C1, C2, C3
Outputs a high level signal, a high level signal, and a high level signal, respectively, when V _T <V ₁ . Also, V ₁ ≦ V _T
When <V ₂ , it outputs a low level signal, a high level signal, and a high level signal, respectively. In addition, V ₂ ≦ V _T <V ₃
At the time of, a low level signal, a low level signal, and a high level signal are output, respectively. When V ₃ ≦ V _T, a low level signal, a low level signal, and a low level signal are output, respectively.

Here, the reference voltages V ₁ , V ₂ and V ₃ are TP = T
It is set such that V _T = V ₃ when the _{V T = V 2, TP =} TP 0 when _{V T = V 1, TP =} TP 1 when P _2.

The CPU 53 outputs a gate control signal from the output terminal P1 to control ON / OFF of the heater 20 (not shown). The input terminals P11, P12 and P13 have a high level signal, a high level signal and a high level signal, respectively. When the level signal is input, that is, when TP <TP ₂ , the high-level gate control signal is continuously output from the output terminal P1 from the time of inputting the zero-cross signal to switch the switch as shown in FIG. The part 30 is turned on.

When a low level signal, a high level signal, and a high level signal are input to the input terminals P11, P12, and P13, respectively, that is, when TP ₂ ≤TP <TP ₁ , 2 from the time of inputting the zero-cross signal. Cycle high level,
By repeatedly outputting the low-level gate control signal for one cycle, the switch section 30 is made to repeatedly perform the operation of two cycles on and one cycle off, as shown in FIG.

When a low level signal, a low level signal, and a high level signal are input to the input terminals P11, P12, and P13, that is, when TP ₁ ≤TP <TP ₀ , 1 is input from the time of inputting the zero-cross signal. Cycle high level,
By repeatedly outputting the low-level gate control signal for one cycle, the switch unit 30 is made to repeatedly perform one cycle on and one cycle off operations as shown in FIG.

When a low level signal, a low level signal, and a low level signal are input from the input terminals P11, P12, and P13, respectively, that is, when TP ₀ ≤TP, the heater 20 is deenergized.

As a result, the member to be heated is heated as shown in FIG. 3 as in the case of FIG. 1, and the same effect as in FIG. 1 can be obtained in the case of FIG.

An amplifier such as an operational amplifier may be provided between the control unit 50 and the temperature detection unit 60 to amplify the divided voltage V _T. By this, the comparator C
1, C2, since the variation width of the input voltage to C3 can be increased, because it can increase the level difference between the reference voltage V _1, V _2, V _3, reference voltages V _1, V _2, V ₃ settings easily You can do it.

In the above embodiment, the switch section 30 is controlled to be turned on and off for each cycle of the voltage waveform of the AC power supply 10, but the switch section 30 is detected for each zero-cross detection, that is, for each half cycle of the voltage waveform. The same effect can be obtained by controlling the on / off of.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the heater for heating the member to be heated has been described, but the present invention is not limited to this, and when the AC power source is energized to another general load. By applying it, the same effect can be obtained.

[0054]

As described above, according to the invention of claim 1, the energization from the sine wave AC power source to the load is periodically turned on and off in a predetermined on / off pattern, and the energization is performed. Since the ON / OFF switching is performed in synchronization with the zero-cross detection, the current waveform supplied to the load can be a sine wave. Therefore, the inrush current can be reduced and the power factor can be prevented from lowering. Further, the harmonic current can be reduced. In addition, since the rate of change of the current at the time of turning on is small, the generated noise can be reduced. In addition, the power supplied to the load can be finely controlled.

According to the second aspect of the present invention, the index value relating to the load is detected and the switch is operated until the detected index value reaches a preset value. Can be a sine wave. Therefore, the inrush current can be reduced and the power factor can be prevented from lowering.
Further, the harmonic current can be reduced. In addition, since the rate of change of the current at the time of turning on is small, the generated noise can be reduced. Also, the average power supplied to the load can be finely controlled until the index value reaches the set value.

According to the invention of claim 3, when the detection index value is smaller than the first value smaller than the set value,
When the switch is operated in the ON / OFF pattern having the first ON ratio and the detection index value is larger than the first value and smaller than the set value, the switch is set to the second ON ratio smaller than the first ON ratio. The index value can be quickly reached to the set value and the overshoot after the set value is reached can be reduced because the operation is performed in the ON / OFF pattern having ". Moreover, the current waveform supplied to the load can be a sine wave. Therefore, the inrush current can be reduced and the power factor can be prevented from lowering. Further, the harmonic current can be reduced. In addition, since the rate of change of the current at the time of turning on is small, the generated noise can be reduced. Also, the average power supplied to the load can be finely controlled until the index value reaches the set value.

According to the invention of claim 4, when the detected temperature is lower than the first temperature which is smaller than the set temperature,
When the switch is operated in the ON / OFF pattern having the first ON ratio and the detected temperature is higher than the first temperature and lower than the set temperature, the switch is set to the second ON ratio smaller than the first ON ratio. Since the ON / OFF pattern is used, the temperature of the member to be heated can quickly reach the set temperature, and overshoot after reaching the set temperature can be reduced. Further, the waveform of the current supplied to the heater can be a sine wave. Therefore, the inrush current can be reduced and the power factor can be prevented from lowering. Further, the harmonic current can be reduced. In addition, since the rate of change of the current at the time of turning on is small, the generated noise can be reduced. Further, the average electric power supplied to the heater can be finely controlled until the temperature of the heated member reaches the set temperature.

According to the invention of claim 5, when the detected temperature is lower than the first temperature which is smaller than the set temperature,
When the switch is operated in an on / off pattern having an on ratio of 2/3 and the detected temperature is higher than the first temperature and lower than the set temperature, the switch has an on / off pattern having an on ratio of 1/2. Since the temperature of the member to be heated can reach the set temperature quickly, the overshoot after reaching the set temperature can be reduced. Further, the waveform of the current supplied to the heater can be a sine wave. Therefore, the inrush current can be reduced and the power factor can be prevented from lowering. Further, the harmonic current can be reduced. In addition, since the rate of change of the current at the time of turning on is small, the generated noise can be reduced. Further, the average electric power supplied to the heater can be finely controlled until the temperature of the heated member reaches the set temperature.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a heater control circuit to which the present invention is applied.

FIG. 2 is a timing chart showing the voltage waveform of the AC power supply 10, the zero-cross signal, and the operating state of the switch unit 30.

FIG. 3 is a diagram showing a temperature rise of a member to be heated.

FIG. 4 is a flowchart showing an example of an operation procedure of a heater control circuit.

5 is a circuit diagram of another configuration example of the switch section 30 and the control section 50 in FIG.

6 is a circuit diagram of another configuration example of the control unit 50 in FIG.

[Explanation of symbols]

 10 AC power supply 20 Heater (load) 30 Switch section 31 Triac 32 Triac gate circuit 33 Solid state relay (SSR) 40 Zero cross detection circuit 50 Control section (switch control means) 60 Temperature detection section (index value detection means) 61 Thermistor

Claims (5)

[Claims] 1. An AC load energization control device for controlling ON / OFF of energization from a sine wave AC power supply to a load, and zero cross detection means for detecting a zero cross of a voltage waveform of the sine wave AC power supply, and the sine wave AC. The switch interposed between the power source and the load and the switch are periodically turned on and off in a predetermined on / off pattern, and the on / off switching of the switch is synchronized with the detection of the zero cross. An alternating-current load electrification control device, comprising: 2. The AC load energization control device according to claim 1, further comprising an index value detecting means for detecting an index value related to the load, wherein the switch control means has the detection index value reaching a preset value. An AC load electrification control device characterized in that the above switches are operated up to. 3. The switch control means operates the switch in an ON / OFF pattern having a first ON ratio when the detection index value is smaller than a first value smaller than the set value. When the detection index value is larger than the first value and smaller than the set value, the switch is operated in an ON / OFF pattern having a second ON ratio smaller than the first ON ratio. The AC load energization control device according to claim 2, wherein 4. The load is a heater for heating a heated member, the index value is the temperature of the heated member, and
4. The AC load energization control device according to claim 3, wherein the value of is a first temperature lower than a preset temperature, and the index value detecting means detects the temperature of the heated member. 5. When the detected temperature is lower than the first temperature, the switch control means sets the switch to 2 /
When the switch is operated in an on / off pattern having an on ratio of 3, the detected temperature is higher than the first temperature,
If the temperature is lower than the set temperature, set the switch to 1 /
The AC load electrification control device according to claim 4, wherein the switch is operated in an ON / OFF pattern having an ON ratio of 2.