JPH057947B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a non-contact AC power phase control circuit using a step-down transformer and a photocoupler.

(b) Prior art and problems to be solved by the invention Conventionally, an alternating current control circuit 30 using an SCR, a triax, etc. was directly connected to an alternating current power supply E as shown in FIG. There was a risk of electric shock when controlling power using resistors.

On the other hand, when performing remote control from a low voltage operation circuit, when using a photocoupler non-contact relay 31 as shown in Figure 2, a separate power supply VS is required for operation input, and even if on/off control is possible, the phase Since this cannot be controlled, a separate control circuit is required for phase control.

Further, as shown in FIG. 3, even when a step-down transformer 32 is used in the phase control circuit, it is necessary to separate the pulse generation circuit and the gate circuit of the triac with a separate pulse transformer (PULSE Tr.).

The present invention aims to solve the above-mentioned drawbacks of the prior art, and it is possible to perform phase control on the low voltage circuit side without fear of electric shock, and does not require a separate DC power supply or pulse transformer. The purpose is to provide a simple phase control circuit.

(c) Means for Solving the Problems In order to achieve the above object, the AC power phase control circuit of the present invention consists of a series circuit of a load and a bidirectional three-terminal thyristor, and is supplied with AC power. a load circuit section a, and a time constant circuit section b connected in parallel to the load circuit section or the bidirectional three-terminal thyristor and consisting of a series circuit of a full-wave rectifier circuit, a phototransistor for a photocoupler, a current-limiting resistor, and a capacitor; , a trigger actuating part c that turns on the bidirectional three-terminal thyristor when the voltage across the capacitor exceeds a predetermined value; a trigger actuating part c connected in parallel to the time constant circuit part; A transformer current detection unit d is connected to both ends of the secondary coil of the step-down transformer; , and a transformer current variable section e that can change its own impedance continuously or discretely.

(d) Effect The transformer current variable section e is specifically constructed using, for example, a variable resistor, and when this variable resistor is varied, the impedance on the secondary side and the primary side of the step-down transformer is changed.

Then, the current value of the transformer current detection section d changes, and the amount of light emitted from the light emitting diodes forming the anti-parallel diode connection section changes.

This light emitting diode is optically coupled with a phototransistor to form a photocoupler, and the internal resistance value of this phototransistor also changes in accordance with the change in the amount of light emitted. Therefore, the value of the current flowing through the time constant circuit section b also changes.

The capacitor forming the time constant circuit part b is
Since it is charged via a phototransistor etc.
The internal resistance of the phototransistor changes in accordance with the operation in the transformer current detection section e described above, and therefore the charging speed of the voltage across the capacitor changes.

The trigger operation section c is a section that receives the voltage across the capacitor and triggers the bidirectional three-terminal thyristor when this value exceeds a predetermined value. Therefore, if the charging speed of the voltage across the capacitor is changed by operating the transformer current variable part e, the trigger timing of the bidirectional three-terminal thyristor will change, and as a result, the phase of the AC power will be controlled. Become.

In this way, the present invention is constructed without duplicating expensive parts, control circuits, or power supply circuits, and the manual operation part is isolated from the AC power supply side using only a step-down transformer, and the primary current of the step-down transformer is By changing the internal resistance of the phototransistor, the oscillation period of the relaxation oscillation circuit consisting of a current limiting resistor, a capacitor, and a trigger element is changed, thereby controlling the phase of the bidirectional three-terminal thyristor. In other words, the transformer current variable part e, which is manually operated, is on the secondary side of the step-down transformer, so there is no risk of electric shock, and since the AC power supply (rectified output) is used as the power supply voltage for the photocoupler and relaxation oscillation circuit, , there is no need for a separate DC power supply.

(E) Embodiment The configuration of the basic circuit shown in FIG. 4, which is an embodiment of the present invention, will be explained. A step-down transformer 1 in which a variable resistor 4 and a switch 5 are connected in series to a secondary coil 3.
A circuit in which two light emitting diodes 7, 7' and an adjustment resistor 8 are connected in series with a photocoupler 6, 6' connected in anti-parallel to the primary coil 2 of the photocoupler 6, 6' and a phototransistor 9 of the photocoupler 6, 6' on the DC side. , 9', a series circuit of a full-wave rectifier 10, a current limiting resistor 11, and a capacitor 12 are connected to a power supply 13, and the connection point of the current limiting resistor 11 and capacitor 12 is connected to a trigger element (SBS is used in this circuit). ) 14, the triax 1 is connected in series to the load 15.
A series circuit of a capacitor 17 and a resistor 18 is connected between both terminals T ₁ and T ₂ of the triax 16 to absorb momentary overvoltage. It protects the triax and prevents malfunction.

In FIG. 4, a full-wave rectifier 10, phototransistors 9, 9', current limiting resistor 11, capacitor 12,
The SBS 14 and the triac 16 form a relaxation oscillation circuit. When the voltage across the capacitor 12 exceeds a predetermined value, the triac 16 is triggered and turned on, and at the same time, the charge in the capacitor 12 is discharged.

FIG. 5 shows a circuit according to another embodiment of the present invention, which includes a series circuit of photocouplers 6, 6', light emitting diodes 7, 7' and an adjustment resistor 8 in antiparallel with the primary coil 2,
This is a circuit in which a series circuit of a full-wave rectifier circuit 10, a current limiting resistor 11 for phototransistor protection, and a capacitor 12 are connected in parallel to a triac 16, and a power supply voltage is applied to both series circuits via a load 15. Become. That is, this is a circuit in which the connection of point C to point A in FIG. 4 is changed to point B.

Furthermore, Fig. 6 shows a circuit using a sealed photocoupler in which two light emitting diodes 7 and 7' are connected in reverse parallel, and Fig. 7 shows a circuit in which light emitting diode 7 and diode 19 are connected in parallel in opposite directions. This is the circuit. Further, FIGS. 8A to 8D show several examples of combination circuits of a control operation switch, a variable resistor, and a resistor connected to the secondary coil 3.

Next, the operation of the present invention will be explained based on FIGS. 4 and 5.

If the switch 5 is now in an open state, no current will flow through the secondary coil 3, and an excitation current that is delayed by nearly 90 degrees from the AC power supply 13 will flow through the primary coil 2. However, since an adjustment resistor 8 of an appropriate value is connected to the primary coil 2, the excitation current value is very small, and the collectors of the phototransistors 9, 9',
The internal resistance between the emitters is high.

Therefore, the current in the phototransistors 9, 9' is so small that the capacitor 12 is not charged, or even if it is charged during a half cycle, it is below the breakover voltage of the SBS 14, and the trigger element SBS does not operate. In other words, if switch 5 is open, the relaxation oscillator circuit will not operate and the triac 1
6 will not fire.

On the other hand, when the switch 5 is closed and the variable resistor 4 is adjusted to, for example, 0 ohm, the secondary coil 3 is short-circuited, and the primary impedance of the step-down transformer 1 is drastically reduced, causing the photocouplers 6 and 6' to emit light. A primary current flows through the diodes 7, 7'. Therefore, the light emitting diodes 7 and 7' emit light alternately,
When the phototransistors 9, 9' of the photocouplers 6, 6' receive the light, conduction is established between the collectors and emitters of the phototransistors 9, 9'.

When the phototransistors 9 and 9' conduct, their internal resistance becomes very small, and the power supply voltage is applied to the capacitor 12 through the combined resistance with the current limiting resistor 11. When the charging voltage of the capacitor 12 exceeds the breakover voltage of the trigger element SBS14, the triac 16 is turned on and the charge on the capacitor is discharged through the gate G and the terminal _T1 .

The above action is repeated during a half cycle of the power supply 13, so that the relaxation oscillation circuit enters an oscillating state. Note that the charging and discharging performed every half cycle is determined by the combined resistance of the internal resistance of the phototransistors 9 and 9' and the current limiting resistor 11, but in experiments, the oscillation circuit was used less than 10 times. Furthermore, since the light emitted from the light emitting diodes 7, 7' at this time is approximately in phase with the power supply voltage, the voltage applied to the capacitor 12 is almost close to the power supply voltage, and therefore the triac 16 is in a state close to full firing.

Next, by increasing the resistance value of variable resistor 4,
The secondary short-circuit current is reduced, and therefore the primary current is also reduced, and the current flowing through the light-emitting diodes 7, 7' is also reduced.
Then, the luminous intensity of the light emitting diodes 7, 7' decreases,
The internal resistance between the opposing phototransistors 9, 9' collector and emitter increases, and the combined resistance value with the current limiting resistor 11 increases, and the number of oscillations during a half cycle of the power supply 13 decreases to 0 in the limit. .

When the resistance value of the variable resistor 4 is increased, the primary current of the step-down transformer 1 gradually lags behind and eventually reaches nearly 90 degrees. Therefore, by changing the variable resistor 4, the charging time and the discharging timing can be delayed. In addition, AC power supply 13
The polarity is reversed every half cycle, but the first discharge in a half cycle becomes the turn-on current of the triax 16 and is phase controlled, making it possible to continuously control the phase of the load power over a wide range. , when the secondary coil is short-circuited, phase control close to full ignition is possible. Note that the above-mentioned relaxation oscillation is performed in synchronization with every half cycle of the power supply voltage.

In the circuit of FIG. 5, when the triac 16 is ignited by the first discharge of the above-mentioned action, there is almost no voltage to the control circuit (only the voltage drop across the triac 16), so only the first pulse signal (discharge) per half cycle. However, when the triac is ignited, it conducts until the voltage reaches 0 volts, that is, until the polarity of the voltage is reversed, so the phase of the power can be controlled in the same way as the circuit shown in FIG. 4, and its operation and effect remain the same.

FIG. 6 shows a circuit using a photocoupler 6 in which two light emitting diodes 7 and 7' are connected in antiparallel and sealed opposite to one phototransistor 9.
Similarly to the circuit using two photocouplers shown in FIGS. 4 and 5, similar effects can be obtained by alternately emitting light using alternating current.

FIG. 7 shows a circuit in which a photocoupler light emitting diode 7 and a diode 19 are connected in antiparallel.
In this circuit, the light emitting diode 7 emits light only in one direction of the AC power supply, so the phototransistor 9 conducts only half a wave, and the capacitor 12 is charged only in one direction, so the half of the circuit is Becomes control.

FIG. 8 illustrates an example of a circuit connected to the secondary coil 3 of the step-down transformer 1.

A is a circuit in which a switch 5' is further connected in parallel to the operating circuits of FIGS. 4 and 5, and it is convenient because the maximum power can be obtained from any phase control position. B is a circuit in which the variable resistor 4 is a fixed resistor 4' and a short circuit switch 5' is connected in parallel, making it possible to discretely switch between the maximum power and the intermediate power. Note that C is a circuit in which an on/off switch 5 is added to the circuit of B. Also, D
is a circuit that can discretely switch and control the phase control angle in four stages, and each of the circuits A to D described above can be used depending on the purpose.

(F) Effects of the Invention In the present invention, a step-down transformer is used to isolate the power supply and the operating circuit, and since the operating circuit has a low voltage, there is no risk of electric shock. The power supply voltage is applied in series with the primary coil of the transformer, and the relaxation oscillation circuit also uses the power supply voltage, so no separate power supply is required.

Furthermore, since the current of the light emitting diode is small, the step-down transformer can be designed to be compact accordingly, and the entire circuit can be integrated into a compact device.Also, if the operating switch and resistors are wired apart from the secondary coil, It has the advantage that remote control is possible, and by appropriately combining operating switches and resistors, it is possible to freely perform from continuous wide-range phase control to discrete phase control in several stages.

Further, since the present invention has no moving parts other than an operating switch and a variable resistor, it is highly reliable, and is extremely effective.

[Brief explanation of the drawing]

Figures 1, 2 and 3 are circuit diagrams of conventional examples;
Figures 4 and 5 are circuit diagrams of embodiments of the present invention, Figures 6 and 7 are examples of applied circuits of the photocoupler portion of the present invention, and Figure 8 is an example of a combination circuit of an operating switch and resistors. be. 1...Step-down transformer, 2...Primary coil, 3...
...Secondary coil, 4...Variable resistor, 6,6'...Photocoupler, 7,7'...Light emitting diode, 9,
9'...Phototransistor, 10...Full wave rectifier,
12...Capacitor, 14...Trigger element
SBS, 16...triack.

Claims (1)

[Scope of Claims] 1. A load circuit section consisting of a series circuit of a load 15 and a bidirectional three-terminal thyristor 16 and supplied with an AC power supply 13; a time constant circuit section connected in parallel and consisting of a series circuit of a full-wave rectifier circuit 10, phototransistors 9, 9' for photocoupler, current limiting resistor 11, and capacitor 12; In this case, a trigger actuation section 14 that turns on the bidirectional three-terminal thyristor 16, and an adjustment resistor 8 connected in parallel to the time constant circuit section.
, a transformer current detection unit consisting of a series circuit of a primary coil 2 of a step-down transformer, and a diode anti-parallel connection unit 7 including a light emitting diode optically coupled to the phototransistor 9, 9' for the photocoupler; 1. A phase control circuit for alternating current power, comprising transformer current variable parts 4 and 5 connected to both ends of a secondary coil 3 of a step-down transformer 1 and capable of changing impedance continuously or discretely.