JPS623665B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an AC power control circuit used in a light control device and the like, and it is an object of the present invention to provide a circuit having means for compensating for fluctuations in power supply voltage.

BACKGROUND ART Conventionally, AC power control circuits that perform phase control using bidirectional three-terminal thyristors (hereinafter simply referred to as thyristors) are known. The simplest configuration of this circuit is shown in FIG. 1, and the brightness of the lamp 1-2 can be controlled by adjusting a variable resistor (hereinafter referred to as VR) 1-1. Here, a circuit configuration in which VR2-1 is inserted as shown in FIG. 2 may be used. In short, the time constant only needs to be changed by adjusting VR1-1 and VR1-1. In Figures 1 and 2, 2-2
is a lamp, 1-3 and 2-3 are thyristors, 1
-4 and 2-4 are bidirectional trigger elements (hereinafter simply referred to as trigger elements), 1-5 and 2-5, 2
-8 is resistance, 1-6, 1-7 and 2-6, 2-
7 is a capacitor.

If there is something equivalent to VR as a means of changing the above time constant, VR1-1 in Figures 1 and 2,
2-1 replacement is possible.

The present inventor previously proposed the use of a combination of an insulated gate field effect transistor (hereinafter referred to as MOSFET) and a capacitor as a means for this purpose (see Utility Model Application No. 53-107366 (see Japanese Utility Model Publication No. 61-3269) and earlier applications). ).

In other words, the capacitor 3-2 connected to the gate of MOSFET 3-1 in Fig. 3A is
This is to maintain a gate bias voltage of -1, and the electrical resistance between the drain D and source S of the MOSFET 3-1 changes depending on the voltage of the capacitor 3-2. This can be equivalently considered as VR, as shown in Figure 3B. The resistance between the drain and source of this MOSFET varies depending on the voltage polarity, so the polarity of the voltage applied between the drain and source must be constant depending on whether it is an N-channel type or a P-channel type.

FIG. 4 shows an embodiment of the circuit of this prior application using an N-channel MOSFET. In the figure, 4-
1 is the thyristor, 4-2 is the above thyristor 4-1
This is a trigger element that triggers. Also, 4-3~
4-6 is a rectifier diode that determines the direction of current flowing to MOSFET 4-7, 4-8 is MOSFET 4-
Charge storage capacitor connected to the gate of 7, 4
4-10 is an input resistor whose one end is connected to the gate of MOSFET 4-7 via the neon discharge tube 4-9; -11 and 4-13
is a smoothing capacitor, 4-12 and 4-14 are rectifier diodes that create positive and negative voltages, 4-15 is a neutral switch that selects the above positive and negative voltages, 4-16
is a lamp, 4-17 and 4-16 are resistors for the phase circuit, and 4-19 and 4-20 are capacitors for the phase circuit.

Now, when switch 4-15 is neutral, MOSFET
4-7 is the capacitor 4-8 connected to its gate.
thyristor 4-1 has a resistance determined by the voltage stored in Conducting at a determined ignition phase, the load lamp 4-16 is energized. Next, when the switch 4-15 is turned to the 0 side, the neon discharge tube 4-9 is discharged, the capacitor 4-8 is charged to + due to the time constant with the resistor 4-10, and the MOSFET 4-7 becomes more conductive ( (lower resistance). As a result, the ignition phase of the thyristor 4-1 is delayed, and the power supplied to the lamp 4-16 is reduced. On the other hand, if switch 4-15 is set to the negative side, the voltage across capacitor 4-8 decreases and the MOSFET
4-7 is in the cut-off direction (resistance becomes higher), the firing phase of thyristor 4-1 becomes earlier,
The power supplied to lamp 4-16 increases.

Further, when the switch 4-15 is set to neutral, that state is maintained. That is, when the neon discharge tube 4-9 stops discharging (the switch 4-15 is in the neutral state), the voltage (charge) of the capacitor 4-8 is as follows.
High insulation of neon discharge tube 4-9 and MOSFET
The power supplied to the lamp 4-16 is maintained for a long time because of the high insulation property of the gate of the lamp 4-7.

In the embodiment shown in FIG. 4, the charge storage capacitor 4-
8 is placed between the gate and source of MOSFET4-7, which is connected to the MOSFET as shown in Figure 5.
Capacitor 5-2 between the gate and drain of 5-1
You may also include The advantage of this case is that negative feedback is applied to the gate from the drain side, so that the operation is smoother than in the embodiment shown in FIG. However, while the circuit shown in Figure 5 provides smoother changes,
There is a disadvantage that it takes time for MOSFET5-1 to cut off and become fully conductive, and the resistance when fully conductive (maximum power supplied to the load) is higher than in the case shown in Figure 4. The configuration shown in FIG. 5 has the disadvantage that the maximum power supplied to the load is small. In order to improve both of these drawbacks, capacitors 6-2, 6-
3 on both the source and drain sides of MOSFET 6-1 will solve the above drawback.

In the circuits so far, we have explained that the MOSFET's withstand voltage (between drain and source) is sufficiently high, but the withstand voltage is required to be 50V or more (when used at 100V AC), and a small-signal MOSFET must meet this requirement. There are few. In this case, the configuration is as shown in FIG. In other words, MOSFET7-
The cathode of a Zener diode 7-2 is connected to the base of a compensating transistor 7-4 whose emitter is connected to the drain of MOSFET 7-1.
connected to the source. 7-3 is a resistor connected between the base and collector of the transistor 7-4. The Zener voltage of the Zener diode 7-2 is smaller than the withstand voltage of the MOSFET 7-1. As a result, the drain voltage of MOSFET 7-1 does not rise above the Zener voltage of Zener diode 7-2, and is shared by transistor 7-4.

In the circuit shown in Fig. 4, a full-wave rectifier circuit is constructed by diodes 4-3 to 4-6, but for simplification, diodes 8-1 and 8-2 are used as shown in Fig. 8.
Although the configuration of a half-wave rectifier circuit according to the method described above has degraded characteristics (the maximum load supply power becomes smaller and the positive and negative firing phases become asymmetric), it can be effective depending on the method of use.

Next, the dimming (power control is explained as dimming) characteristics of the circuit shown in FIG. 4 will be explained with reference to FIGS. 9A, 9B, and 9C. Now, when the firing phase of thyristor 4-1 is delayed, the voltage across the thyristor 4-1 and the capacitors 4-11 and 4-1 at this time.
The voltages of No. 3 are shown in a, a, b, and c of Fig. 9. Here, when the switch 4-15 is turned to one side, the firing phase of the thyristor 4-1 becomes earlier (the lamp 4-16 becomes brighter) as explained earlier, and as shown in FIG.
As shown in Figure 9b, the voltage across capacitors 4-13 remains almost the same from 180° to approximately 90°, but as it exceeds 90°, it gradually decreases as shown in Figure 9a.
It becomes as shown in c of B and C. At this time, when the voltage of the capacitor 4-13 becomes lower than the discharge voltage of the neon discharge tube 4-9, the discharge of the capacitor 4-8 will stop, and the firing phase of the thyristor 4-1 will no longer be accelerated, so the switch 4-15 will be turned on. Even if you keep pushing it to one side, it will not light up beyond a certain point and will act as a limiter.

On the other hand, when the switch 4-15 is turned to the + side, the firing phase of the thyristor 4-1 is delayed, and the sequence changes from c to b to a in A, B, and C of FIG. 9. However, capacitor 4
The voltage at -11 remains high even when the ignition phase becomes 180°, and charging of the capacitor 4-8 continues even if the thyristor 4-1 becomes non-conductive (the dimming illuminance is zero). As a result, capacitors 4-8 may become overcharged, potentially causing damage to the components.
Furthermore, when the switch 4-15 is next turned to one side to increase the dimming illuminance, there is a delay before the thyristor 4-1 starts conducting, resulting in poor operability.

A circuit configuration for solving the above problem will now be described. Since what is required here is a positive voltage, only that part will be shown and explained in FIG. 10. In addition, Fig. 11 A, B, and C show the voltage across the thyristor 10-1 and the collector voltage of the capacitor 10-2 (corresponding to capacitor 4-11 in Fig. 4) and the switching transistor 10-3 at this time. is shown. 1st
In Figure 0, 10-4 is a rectifier diode (corresponding to rectifier diode 4-12 in Figure 4), 10-5 is a resistor,
10-6 is a terminal for taking out the collector voltage of the transistor 10-3 to a switch section (not shown). Now, when the thyristor 10-1 is non-conductive, the transistor 10-3 is conductive, and the capacitor 10-2
As shown in Fig. 11, the voltage of thyristor 10-
It changes almost the same as the voltage of 1. Next, when the thyristor 10-1 becomes conductive, the transistor 10-3
becomes non-conductive, and the voltage of the capacitor 10-2 maintains the voltage at that time. On the other hand, transistor 10
-3 collector voltage is thyristor 10-1
The voltage of the capacitor 10-2 is taken out while the capacitor 10-2 is not conducting. By using the collector voltage of this transistor 10-3, if the firing phase of the thyristor 10-1 is delayed, the voltage at the terminal 10-6 decreases, and finally becomes lower than the discharge voltage of the neon discharge tube 4-9 shown in Fig. 4. Therefore, capacitor 4-8 shown in Fig. 4
charging will stop and there will be a limiter effect.

The object of the present invention is to provide a circuit that compensates for variations in phase angle power supply voltage at low power (small phase angle).

An embodiment of the present invention is shown in FIG. 12, and is configured by incorporating a trigger element 12-1 into a phase circuit, and this trigger element 12-1 is connected to a phase angle power supply voltage at low power (small phase angle). This serves to compensate for fluctuations in In addition, trigger element 1
A protective resistor 12-2 is inserted and connected in series with 2-1. The specific function of the trigger element 12-1 will be explained with reference to FIG. 13. 13th
Figure a shows the voltage waveform at point A in Figure 12,
The voltage waveform at point A is generated by trigger element 12-1 as shown in the figure.
The voltage becomes constant due to the breakover voltage. Next, FIG. 13b shows a voltage waveform when the power supply voltage at point A fluctuates at low power, for example. In FIG. 13b, if A is the normal power supply voltage, the waveform will be when B rises and C falls. As shown in the figure, the phase angles A', B', and C' change with fluctuations in the power supply voltage, and serve to keep the power, or illuminance, constant. This can prevent flickering of the lamp during dimming, for example. The above is the function of the trigger element 12-1, but the constant of the protection resistor 12-2 described above must be such that it can supply a current that does not destroy the trigger element 12-1. Further, the breakover voltage of the trigger element 12-1 is preferably two to three times that of the trigger element 12-3 for ignition (corresponding to the trigger element 4-1 in FIG. 4).

Next, resistors 12-6, 12-5 connected in parallel with capacitors 12-4, 12-5 (corresponding to capacitors 4-11, 4-13 in FIG. 4) constituting the rectifier circuit in FIG. 7 will be explained. The resistors 12-6 and 12-7 are both for discharging the capacitors 12-4 and 12-5 connected in parallel. If the resistors 12-6 and 12-7 were not present, even when the power supply voltage was OFF, the charge voltage remaining in the capacitors 12-4 and 12-5 when the power supply voltage was ON would cause the switch 12-8 (see Figure 4) to be activated. Neon discharge tube 12-9 (corresponding to neon discharge tube 4-9 in Figure 4) is discharged by operating the switch (corresponding to switch 4-15), and the phase angle may change even though the power supply voltage is OFF. It was hot. Resistor 12-6,1 was inserted to eliminate this drawback.
It is 2-7.

In addition, 12-10 in FIG. 12 is a protection diode for the transistor 12-11 (corresponding to the transistor 10-3 in FIG. 10) when the polarity is reversed;
2-12 and 12-13 are protective resistors for diodes 12-14 and 12-15 (corresponding to diodes 4-12 and 4-14 in FIG. 4) constituting the rectifier circuit. Furthermore, FIG. 12 also shows an embodiment in which the limiter circuit described above is incorporated into the circuit of FIG. 4. It should be noted that even if the rectifier circuit incorporated in the phase circuit is omitted, there will be no fatal problem in terms of operation, but in that case, it is preferable to add a circuit that compensates for the withstand voltage of the MOSFET as explained in FIG.

The above is an explanation including the embodiments of the present invention, and the explanation so far has shown an example applied to VR2-1 in Fig. 2, but this can also be applied to VR1-1 in Fig. 1. What can be done is clear from the above explanation. Further, although the above embodiments have been described using MOSFETs, a junction gate field effect transistor may be used instead of MOSFETs if charge leakage is allowed to some extent.

The present invention is configured as described above, and has the feature that an unprecedented power control device such as a light control device can be obtained with a simple circuit configuration, and that the power control device can be controlled by a switch. In addition, it is possible to compensate for fluctuations in the power supply voltage of the phase angle at low power (small phase angle), and has features such as being able to prevent flickering of the lamp during dimming, etc.
It is possible to provide a new operating means that has not existed before.

[Brief explanation of the drawing]

Figures 1 and 2 are electrical circuit diagrams showing a conventional light control device, respectively, and Figures 3A and 3B are electrical circuit diagrams of the main parts constituting the circuit proposed earlier by the inventor. An equivalent circuit diagram, FIG. 4 is an electrical circuit diagram showing one embodiment of the AC power control circuit according to the earlier application, and FIGS. 5 and 6 show other connection examples of charge storage capacitors in the circuit of the earlier application. Fig. 7 is an electrical circuit diagram of the main part that compensates for the withstand voltage of the MOSFET, Fig. 8 is an electrical circuit diagram of the main part showing another example of the same rectifier circuit, 9th
Figures A, B, and C are voltage waveform diagrams of various parts in Figure 4, Figure 10 is an electrical circuit diagram of the main part of the limiter circuit in the circuit of the prior application, and Figure 11 A, B, and C are the voltage waveform diagrams of each part in Figure 4.
Figure 12 is an electrical circuit diagram showing an embodiment of the circuit of the present invention; Figures 13a and b are voltage waveform diagrams at point A of the circuit in Figure 12, and It is a voltage waveform diagram of the same point A in electric power. 4-1, 10-1... Bidirectional 3-terminal thyristor, 4-2, 12-3... First bidirectional trigger element, 4-3 to 4-6, 8-1, 8-2... ...Another rectifier circuit (diode), 4-7, 5-1, 6-
1, 7-1...Field effect transistor (MOSFET), 4-8, 5-2, 6-2, 6-3
...Charge storage capacitor, 4-8, 12-1,
12-9...Neon discharge tube, 4-11, 4-1
3, 12-4, 12-5, 4-12, 4-14,
12-14, 12-15, 12-6, 12-7...
... Rectifier circuit (smoothing capacitor, rectifier diode, resistor), 4-15, 12-8 ... Switch section, 4-16 ... Load (lamp), 12-1 ...
a second bidirectional trigger element;

Claims (1)

[Claims] 1. A bidirectional three-terminal thyristor that controls the firing phase of a load such as a lamp, and a first bidirectional trigger element that fires the bidirectional three-terminal thyristor.
A series circuit of a resistor connected to the output terminal of the bidirectional three-terminal thyristor and a second bidirectional trigger element, and another resistor connected to the connection point of this resistor and this second bidirectional trigger element. and a capacitor; an insulated gate field effect transistor whose drain and source are connected to the output terminal of a full-wave rectifier circuit incorporated in the phase control circuit;
A charge storage capacitor connected between the gate and drain of the insulated gate field effect transistor, a neon discharge tube having a switch portion on one side connected to the gate of the insulated gate field effect transistor, and this switch. and a half-wave rectifier circuit which is connected to a half-wave rectifier circuit and which is composed of a diode and a capacitor for generating positive and negative voltages, and whose input is the output end of the bidirectional three-terminal thyristor. control circuit.