JPH077311B2 - Power control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power control device for cycle-controlling load power of a load such as a heater in an electric furnace, and more particularly to a power control device for controlling load power of a plurality of loads. The present invention relates to prevention of fluctuations in power supply voltage.

[Prior Art] FIG. 3 shows a circuit diagram of a power control device having a normal cycle control device. In the figure, (1) detects the temperature of, for example, an electric furnace and the deviation between the detected temperature and the set temperature. A control signal output from a temperature controller or the like according to, (R1) is a resistance that changes the control signal (1) into a voltage, (R2) is an input resistance,
(D) is a diode that limits the input voltage, (2) is an impedance converter, (VR1) is a variable resistor and a resistor (R
Together with 3), it forms a voltage divider circuit for the output voltage of the impedance converter (2).

Then, the circuit consisting of the control signal (1), the resistance (R1), the diode (D), the input resistance (R2), the impedance converter (2), the variable resistance (VR1) and the resistance (R3) detects the set value and the detected value. A control voltage generator that generates a control voltage corresponding to the deviation from the value is configured. The control voltage is output from the variable resistor (VR1).

(3) is an operational amplifier (5), (6) and a variable resistor (VR
2), a triangular wave generating circuit composed of resistors (R4) to (R7) and a capacitor (C), which outputs a triangular wave voltage (21) shown in FIG. The period of the triangular wave voltage (21) is determined by the setting of the variable resistor (VR2), and the center value is determined by the voltage (Vi) input to the terminal (4).

(8) is a comparator, (9) is a transistor, (10)
Is a semiconductor switch including a zero-cross trigger circuit and a bidirectional thyristor switch.

The comparator (8) has a variable resistor (VR
The output level voltage (22) of the impedance converter (2) output via 1) is compared with the triangular wave voltage (21),
The triangular wave voltage (21) is the control voltage and the output level voltage (2
2) It is designed to bring the output voltage (24) to the “low” level when it is higher. The output voltage (24) of the comparator (8) is output to the transistor (9) through the resistor (R9), and the semiconductor switch outputs a control signal corresponding to the output voltage (24) of the comparator (8) from the transistor (9). (Ten)
The semiconductor switch (10) and load such as heater (13)
During a certain control period (T), the load current (25) is energized (ON) from the power supply (12) and then de-energized (OFF) is repeated, and the power of the load (13) is reduced. Have control. This operating state is displayed on the light emitting diode (LED) by the current flowing through the resistor (R8). Note that (1
1) is a power supply for the control signal output from the transistor (9).

[Problems to be Solved by the Invention] The power control device having the cycle control device configured as described above has a load current when the load (13) is energized even when the output voltage is set small. The current value of (25) is
It is the same as when 100% energized. Therefore, as shown in FIG. 5, a plurality of transistors (9) and (9a) and a plurality of semiconductor switches (10) and (10
a) is connected, power is supplied from the same power supply (12) to multiple loads (13) and (13a), and load current is applied at the same timing, all loads (13) and (13a) are energized.
Current flows, and the maximum rated current flows.

For this reason, when the capacity of the power supply (12) is small, a voltage drop occurs when the power is supplied, the voltage is restored when the power is not supplied, and the power supply voltage fluctuates, which adversely affects other devices.

The present invention has been made in order to solve such a problem, and proposes a voltage control device capable of preventing fluctuations in power supply voltage by averaging energization currents when performing cycle control of a plurality of loads. It is intended.

[Means for Solving Problems] A power control device according to the present invention sets a control cycle of a current flowing through each load connected to an AC power supply via two semiconductor switches, and sets the control cycle to the control cycle. A power control device that gives a phase difference to turn on / off the first semiconductor switch and the second semiconductor switch continuously for several cycles, respectively, and further controls the power of each load by the on / off time ratio of each semiconductor switch. Therefore, the phase shift means for giving a phase difference to the control cycle includes a triangular wave generating circuit for generating a triangular wave voltage for determining the control cycle, and a control voltage for generating a control voltage corresponding to the deviation between the set value and the detected value. A generator, a first comparator that compares the triangular wave voltage and the control voltage, and outputs a first comparison signal having a significant period and an insignificant period according to the comparison result, and the control voltage as the reference voltage. for A second comparison in which the inverted voltage and the triangular wave voltage are compared, and the significant period and the insignificant period according to the comparison result are the same as those of the first comparison signal and have a phase difference from the first comparison signal. A second comparator for outputting a signal is provided, and when the first comparison signal and the second comparison signal are significant, the first semiconductor switch and the second semiconductor switch are turned on.

[Operation] In the present invention, the phase shifting means for giving a phase difference to the control cycle, the triangular wave generating circuit for generating the triangular wave voltage for determining the control cycle, and the control voltage corresponding to the deviation between the set value and the detected value. A control voltage generator for generating a voltage, a first comparator that compares the triangular wave voltage and the control voltage, and outputs a first comparison signal having a significant period and an insignificant period according to the comparison result; The voltage obtained by inverting the voltage with respect to the reference voltage is compared with the triangular wave voltage, and the significant period and the insignificant period according to the comparison result are the same as those of the first comparison signal, and are equal to those of the first comparison signal. A second comparator that outputs a second comparison signal having a phase difference, and turns on the first semiconductor switch and the second semiconductor switch when the first comparison signal and the second comparison signal are significant. Within a constant control cycle The energization period of each semiconductor switch is dispersed.

[Embodiment] FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which (1) to (13) are exactly the same as the conventional examples shown in FIG. 3 and FIG. (14) is an operational amplifier,
The operational amplifier (14), the input resistance (R10) and the negative feedback resistance (R11) form an inverting amplifier (15). (1
6) is a comparator, and (R12) and (R13) are resistors.

The operation of the power control device configured as described above will be described based on the waveform diagram shown in FIG.

The comparator (8) outputs the triangular wave voltage (21) output from the triangular wave generation circuit (3) and the output level voltage () output from the impedance converter (2) which receives the control signal (1) via the variable resistor (VR1). 22) and compare the triangular wave voltage (2
Output voltage (24) consisting of pulse wave that becomes “low” level when 1) is higher than output level voltage (22) and “high” level when triangular wave voltage (21) is lower than output level voltage (22). Output to the transistor (9). The output voltage (24) causes the transistor (9) to switch the semiconductor switch (1
0) is turned on for a predetermined number of cycles within a constant control period (T), the load current (25) is supplied to the load (13), and then turned off. This operation is repeated every control cycle (T) to control the power of the load (13).

On the other hand, the inverting amplifier (15) has a reference voltage (Vi) that determines the central value of the output voltage (22) of the impedance converter (2) from the variable resistor (VR1) and the triangular wave generation circuit (3) from the variable resistance (VR1). ) Is input, and the inverting amplifier (15) converts the output level voltage (22) into a symmetrical potential with respect to the reference voltage (Vi) and outputs the second output level voltage (22a) to the comparator (16). The comparator (16) compares the second output level voltage (22a) with the triangular wave voltage (21), and the triangular wave voltage (21) outputs the second output level voltage (22a).
“High” level when higher, triangular wave voltage (21) is second
The second output voltage (24a), which becomes a "low" level when the voltage is lower than the output level voltage (22a) of the above, is output to the transistor (9a). The transistor (9a) has a second output voltage (24a)
Sends a control signal to the semiconductor switch (13a) to control the semiconductor switch (13a), and energizes the load (13a) with a load current (25a) for a predetermined period within a constant control period (T) to load the load (13a). ) Control the power of.

In this embodiment, the output voltage (24) and the second output voltage (24a) are significant at the "high" level and insignificant at the "low" level.

As described above, the control cycle of the load current (25a) flowing through the load (13a) is equal to that of the inverting amplifier (15) and the comparator (1).
Since the control period and phase of the load current (25) flowing through the load (13) are shifted by 1/2 of one wavelength of the triangular wave voltage (21) by 6), both loads (13) and (13a) are energized at the same time. Can be prevented.

In the above embodiment, the case where the number of loads is two has been described, but even if the number of loads is three or more, the control cycle of the load current flowing through each load is shifted by 2π / n radian in accordance with the number n of loads. As a result, the load current can be dispersed.

Further, in the above embodiment, the case where the loads (13) and (13a) are driven by the single-phase power supply (12) has been described, but the same can be applied to the case where a plurality of loads are driven by the three-phase power supply.

Further, although the above-mentioned embodiment has explained the case where the loads (13) and (13a) are controlled by the same control signal, the energization time is controlled in the same manner as in the above-mentioned embodiment even if the control signal is different for each load. can do.

EFFECTS OF THE INVENTION As described above, according to the present invention, the phase shift means for giving a phase difference to the control cycle includes a triangular wave generating circuit for generating a triangular wave voltage for determining the control cycle, and a set value and a detected value. A control voltage generator that generates a control voltage corresponding to the deviation is compared with a triangular wave voltage and the control voltage, and a first comparison signal having a significant period and an insignificant period according to the comparison result is output. The comparator 1 is compared with the voltage obtained by inverting the control voltage with respect to the reference voltage and the triangular wave voltage, and the significant period and the insignificant period corresponding to the comparison result are the same as those of the first comparison signal, and A second comparator for outputting a second comparison signal having a phase difference with the first comparison signal, and the first semiconductor switch and the second comparator when the first comparison signal and the second comparison signal are significant. Because the semiconductor switch of is turned on, The load current can be dispersed and the fluctuation of the power supply voltage can be prevented.

Further, since a load current is not supplied to each load at the same time, there is an effect that even a power source having a small capacity can control a large total load.

Further, the power control device having the above effect can be configured with a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram of the above embodiment, FIG. 3 is a circuit diagram of a power control device having a cycle control device, and FIG. 4 is shown in FIG. FIG. 5 is a waveform diagram of the power control device shown, and FIG. 5 is a circuit diagram showing a conventional example. (1) ... control signal, (2) ... impedance converter, (3) ... triangular wave generating circuit, (8), (16) ... comparator, (9), (9a) ... transistor, (1
0), (10a) ... Semiconductor switch, (13), (13a) ...
… Load, (14)… operational amplifier, (15)… inverting amplifier. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A control cycle of a current flowing through each load connected to an AC power supply via two semiconductor switches is set,
A phase difference is given to the control cycle to turn on / off the first semiconductor switch and the second semiconductor switch for several cycles in succession, and the power of each load is controlled by the on / off time ratio of each semiconductor switch. In the electric power control device, the phase shift means for giving a phase difference to the control cycle corresponds to the deviation between the set value and the detected value, and the triangular wave generation circuit for generating the triangular wave voltage for determining the control cycle. A control voltage generator that generates a control voltage is compared with the triangular wave voltage and the control voltage, and a first comparison signal having a significant period and an insignificant period according to the comparison result is output. A comparator, a voltage obtained by inverting the control voltage with respect to a reference voltage, and the triangular wave voltage are compared, and a significant period and an insignificant period according to the comparison result are the same as those of the first comparison signal, and The first A second comparator for outputting a second comparison signal having a phase difference with the comparison signal, and the first semiconductor switch and the second comparator when the first comparison signal and the second comparison signal are significant. A power control device characterized by turning on a semiconductor switch.