JPS6013483B2 - power control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power control device that controls power supply to a load by phase control.

Conventionally, a constant voltage power source has generally been used as a power source for an exposure light source of a copying machine, for example, but such a constant voltage power source can be obtained by controlling the phase of an alternating current power source.

For example, the one shown in Figure 1 has been proposed as this type of counterfeit. 1 is an AC power supply, and this power supply 1 is equipped with a phase control device 2.
For example, a light bulb as load 3 is connected via a triac.

Further, a full-wave rectifier 4 is connected to the power source 1, and a series circuit of a resistor 5 and a constant voltage element 6 is connected between the output terminals of the rectifier 4. The phase control device 7 of the phase control device 2 is electrically connected to both ends of the constant voltage element.
For example, an oscillator circuit is connected. This conduction phase control device 7 has a time constant circuit of a transistor 8 and a capacitor 9 and a series circuit of a resistor 10 and a resistor 11 connected to both ends of the constant voltage element 6, and a PUT 12 connected to both ends of the capacitor 9. pulse transformer 1
It is formed by connecting a series circuit with 3. Furthermore, PUT1 2
The gate of the PUT 12 is connected to the connection point of the resistor 10 and the resistor 11, and the anode of the PUT 12 is connected to the positive output terminal of the rectifier 4 via the resistor 14. Therefore, this conduction phase control device 7 conducts the PUT 12 when the voltage across the capacitor 9 reaches a predetermined value with respect to the gate voltage of the PUT 12 determined by the resistor 10 and the resistor 11, and outputs a pulse from the pulse transformer 13. It outputs and supplies a trigger signal to the triac which is the phase control device 2. Next, 15 is a detection device for detecting a feedback signal from the load 3.

This detection device 15 consists of a transformer 16 connected in parallel to the load 3, a rectifier 17 provided on the output side of this transformer 16, a smoothing circuit 18 and a time constant circuit 19 provided between the output terminals of this rectifier 17. It is what it is. The output of the time constant circuit 19 is input to a comparator 26 via a resistor 25. This comparator 26 has an error amplifier connected to a starting control power supply 29 including a pair of transistors 27, 28, the resistor 25 is connected to the base of one transistor 27 of this amplifier, and the other A slider of a potentiometer 30 is connected to the base of the transistor 28. And the resistor 25
The feedback signal of the detection device 15 input via the potentiometer 30 is compared with the reference signal input from the potentiometer 30, and the difference between these two signals is calculated by
is inputted from the collector of the transistor 8 to the base of the transistor 8 of the conduction phase control device 7 via the resistor 35. Therefore, the conduction phase control device 7 controls the base voltage of the transistor 8 by the signal from the comparator 26,
By controlling the charging of the charger 9, the output phase of the pulse is changed, the conduction phase of the phase control device 2 is controlled, and the power supplied to the load 3 is controlled. In such a device, the comparison device 26 is deactivated or activated by opening and closing the starting control power source 29, and the load 3 is controlled depending on whether or not a control signal is input to the transistor 8 of the conduction phase control device 7. It controls the operation. However, in such a device, when the starting control power supply 29 is turned on, the resistors 31 and 35 are first turned on.
via which the transistor 8 of the conduction phase control device 7 is biased.

Since the base voltage supplied to the transistor 8 at this time is higher than the control signal in the steady state, the capacitor 9
The charging time is short, and the PUT 12 is made conductive at an early phase, and a pulse is output to make the phase control device 2 conductive. Therefore, a large amount of power is supplied to the load 3, but the load 3
A feedback signal is fed back from the transistor 8, and the difference between the feedback signal and the reference signal is input to the base of the transistor 8. Therefore, the control signal input to the transistor 8 is as shown by the dotted line in FIG. This is something that deteriorates early.
For this reason, the light output of the light bulb, which is the load 3, rises slowly to a predetermined level as shown by the dotted line in FIG. This is because the bulb has a constant time constant for the rise of light output. In order to eliminate this drawback, it is sufficient to prevent the feedback signal from the load 3 from being input to the comparator 26.

To this end, it is conceivable to increase the capacitance of the capacitor 24 of the time constant circuit 19 of the detection device 15 to reduce the influence of the feedback signal from the load 3 on the comparison device 26. However, increasing the capacitance of the capacitor 24 of the detection device 15 has the disadvantage that the response characteristics in a steady state deteriorate. That is, since the response of the feedback signal from the load 3 becomes slow, there is a drawback that the power of the load 3 cannot be controlled with high accuracy. In addition, only the capacitance of the capacitor 24.
When , the constants of the circuit change significantly, but it becomes extremely difficult to design the constants of other components in order to correct this to an appropriate constant. As described above, the conventional device is not suitable for a load such as a light bulb, where there is a time delay before a predetermined output is obtained, and a quick rise of the load output is required.

The present invention has been made to eliminate the drawbacks of the conventional devices described above, and it is an object of the present invention to provide a power control device that can improve load rise characteristics without impairing response characteristics.

Another object of the present invention is to provide a power control device that can improve the load rise characteristics without changing circuit constants and without any influence in a steady state.

The present invention is characterized in that a control device is provided that substantially cuts off the feedback signal from the load for a certain period of time when the load is started, and the feedback signal is not input to the comparison device.

Embodiments of the present invention will be described below with reference to FIG.

Components that are the same as those in FIG. 1 are given the same reference numerals, and their explanation will be omitted. 50 is a control device. This control device 50 controls the load 3
It operates for a certain period of time at the time of starting, and substantially cuts off the feedback signal from the load 3. In this embodiment, a time constant circuit consisting of a resistor 51 and a capacitor 52 connected across the starting control power supply 29, and a series circuit consisting of a resistor 53 and a first transistor 54 connected in parallel to this time constant circuit. , a constant voltage element 55 connected between the connection point of the resistor 51 and capacitor 52 of the time constant circuit and the base of the first transistor 54, and a constant voltage element 55 connected between the output terminal of the detection device 15 and the base connected to the A second transistor 56 is connected to the outside of the first transistor 54. Next, 60 is a soft start circuit, which is particularly effective for overcurrent protection of the phase control device 2, as will be described later.

In this embodiment, a diode 61, a constant voltage element 62, and a capacitor 63 are connected between the output terminals of the comparator 26, and a connection point between the constant voltage element 62 and the capacitor 63 is connected through a parallel circuit of a resistor 64 and a diode 65. This is connected to the positive terminal of the starting control power source 29. In addition,
The charging time constant of the capacitor 63 of the soft start circuit 60 is selected to be smaller than the charging time constant of the capacitor 52 of the control device 50. Next, the effect will be explained.

When the start control power supply 29 is turned on when the load 3 is started, the comparator 26 starts and supplies a control signal to the transistor 8 of the conduction phase control device 7. At this time, the conduction phase control device 7 The pulse is output as described above.By turning on the starting control power supply 29 to the control device 5, charging of the capacitor 52 is started via the resistor 51.Then, the voltage across the capacitor 52 becomes While the voltage is low, the constant voltage element 55 cannot conduct, and the first transistor 54 is non-conductive.Therefore, the second transistor 56 is conductive, and the feedback signal from the load 3 is detected by the detection device 15. Therefore, since the feedback signal is not input to the comparator 2-6, the control signal supplied from the comparator 26 to the conduction & phase control device 7 is as shown in FIG. As shown by the solid line, the value continues to be large without dropping early.Then, since the conduction phase control device 7 outputs pulses at an early phase, the phase control device 2 conducts at an early phase, and the load 3 Since a large amount of power is supplied to the load 3, the optical output of the load 3 rises earlier as shown by the solid line in FIG. 3. After the optical output of the load 3 reaches a predetermined level, 52 is charged to a predetermined value or higher, and the constant voltage element 5
5, the first transistor 54 is suitable. Therefore, since the second transistor 56 becomes non-conductive, the control device 50' does not operate thereafter, and the feedback signal is not bypassed. After this, the feedback signal is compared with the reference signal, and the conduction phase control device 7 is controlled according to the difference between these two signals, and the conduction phase of the phase control device 2 is controlled to control the power supplied to the load 3. Control. Therefore, the load 3 can be supplied with a constant voltage that does not change even when the voltage of the AC power supply 1 fluctuates. Note that when the stop start control power source 29 of the load 3 is turned off, the capacitor 52 of the control device 50 discharges its charge through the resistor 51, so that it can prepare for the next start. Furthermore, it is easy to understand that the operating time of the control device 50 can be arbitrarily selected depending on the time constant of the time constant circuit. Next, since the load 3 is a light bulb, a large rush current may flow at the time of starting, and therefore the capacity of the phase control device 2 needs to be increased. In contrast, in this embodiment, a soft start circuit 60 is provided to reduce the rush current.
That is, when the starting control power supply 29 is turned on, a large control signal is supplied to the transistor 8 of the conduction phase control device 7, but this control signal is regulated by the sum of the potential of the capacitor 63 and the voltage of the constant voltage element 62. It increases as the capacitor 63 is charged, increasing the control signal of the transistor 8 of the conduction phase control device 7. Therefore, the phase control device 2 can gradually advance the conduction phase and reduce the rush current. Then, when the potential of the capacitor 63 reaches a predetermined value or more, the soft start circuit 60' becomes irrelevant to the phase control operation. Note that since the charging time constant of the capacitor 63 of the soft start circuit 60 is smaller than the charging time constant of the capacitor 52 of the control device 50, the feedback signal is quickly cut off even after the soft start circuit 60 is no longer related to the control system. Therefore, the control signal supplied to the transistor 8 of the conduction phase control device 7 is larger than that in the steady state, and a large amount of power can be supplied to the load 3. FIGS. 5 and 6 show other embodiments, each showing only the main parts.

FIG. 5 shows a control device 50' including a relay 57, in which the excitation coil L of the relay 57 is connected in series with the first transistor 54, and the contact S is provided between the output terminals of the detection device 15. It is. FIG. 6 similarly includes a relay 57, but a contact S is provided at the input end of the detection device 15, that is, between the transformer 16 and the rectifier 17. The other configurations and operations are the same as those of the embodiment shown in the fourth figure, so their explanation will be omitted. The present invention is not limited to the above embodiments.

For example, the present invention may be applied not only to a device in which the load voltage is constant but also to a device in which the load current is constant. Further, the phase control device may also be a thyristor connected in antiparallel, for example, instead of a triac. Furthermore, the conduction phase control device, the detection device, and the comparator device may be modified, and the control device may also be of a type that substantially cuts off the feedback signal for a certain period of time when the load is started. In addition to cutting off the feedback signal at the cross point as in the above embodiment, the control device may substantially prevent the feedback signal from being input to the comparison device by passing the feedback signal through a high impedance element only at the time of starting. It is something. As detailed above, the present invention includes a control device that operates for a certain period of time at the time of starting a load to substantially cut off the feedback signal from the load.
It is possible to prevent the feedback signal from being input to the comparison device that controls the conduction phase control device for the predetermined period of time, and therefore, a large amount of power that is not feedback-controlled can be supplied to the load, so that the rise of the load output can be made faster. Moreover, since the control device operates only when the load starts,
Since there is no effect in steady state, the response characteristics of the feedback control will not be deteriorated or the circuit constants will not be changed.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional example, FIGS. 2 and 3 are diagrams explaining the operation, FIG. 4 is a circuit diagram showing an embodiment of the present invention, and FIGS. 5 and 6 are diagrams showing the present invention. FIG. 2 is a circuit diagram showing a main part of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Phase control device, 3... Load, 7... Continuity phase control device,
15...Detection device, 26...Comparison device, 50, 50', 50...Control device. Sue! Figure O 2 Figure O 3 Figure O 4 Figure 2. Ta Hakozai 3

Claims (1)

[Claims] 1. An AC power source, a load supplied with power from this power source, a phase control device interposed between the power source and the load, and a conduction phase control device that controls the conduction phase of this phase control device. , a detection device that detects a feedback signal from the load, a comparison device that inputs the feedback signal of the detection device and compares it with a reference signal, and controls the conduction phase control device according to the difference between the two signals, and the load A power control device comprising: a control device that operates for a predetermined period of time at the time of startup to substantially cut off the feedback signal. 2. The power control device according to claim 1, wherein the control device includes a transistor. 3. The power control device according to claim 1, wherein the control device includes a relay. 4. The power control device according to any one of claims 1 to 3, wherein the control device has a time constant circuit, and the operating time is determined by the time constant of the time constant circuit. .