JP3372146B2 - Phase control circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase control circuit for performing on / off control of a heat source using an AC power source, lighting equipment, etc. by phase control, and more particularly to a printer,
Facsimile, it relates to a phase control circuit need use a heater circuit and a lamp circuit and the like for use in copying machines or the like.

[0002]

2. Description of the Related Art As a conventional phase control circuit, for example,
There is a phase control circuit disclosed in Japanese Patent Application Laid-Open No. 4-105551, which will be described with reference to FIGS. 6 to 9. In the phase control circuit of FIG. 6, the electric power supplied from the AC power supply 1 to the load 2 is phase-controlled by a bidirectional thyristor (hereinafter referred to as a triac) 3, and a sawtooth wave is used for the phase control of the triac 3. A generation circuit 4, a comparison circuit 5, and a photo coupler 6 are provided.

As shown in FIG. 7, the sawtooth wave generation circuit 4 generates a sawtooth wave P2 in synchronization with the voltage waveform P1 of the AC power supply 1. The generated sawtooth wave P2 is the zero-cross point θ10, θ of the AC voltage waveform P2 of the AC power supply 1.
A sharp rise to the vicinity of 20, θ30, ..., and a gradual fall to the vicinity of the next zero cross point θ20, θ30 ,. The sawtooth wave P2 is input to one input terminal of the comparison circuit 5 via the electric path L1, and the input signal for phase control of the triac 3 is input to the other input terminal of the comparison circuit 5 via the electric path L2. Is entered.

The comparator circuit 5 compares the level of the sawtooth wave with the level of the input signal for phase control, and when the level of the sawtooth wave becomes equal to or lower than the level of the input signal, a low level (hereinafter, L level). Derive the output of. Comparison circuit 5
When the L level output is derived, the photothyristor 8 of the photocoupler 6 is turned on. Photo thyristor 8
When is turned on, a trigger current for igniting the triac 3 flows through the resistor and the photothyristor 8. When the input signal P3 for phase control is input to the electric path 2 of the comparator circuit 5 and the input signal P3 for phase control is input, the sawtooth wave P2 becomes equal to or lower than the level of the input signal P3.
During the period indicated by the diagonal lines from 2 to θ20 and from θ22 to θ30, the triac 3 is ignited and power is supplied to the load 2.

However, in the vicinity of the phase angles θ10 and θ20 (period W1), the output of the comparison circuit 5 is forcibly set to a high level (hereinafter, H level) because it is easily affected by variations in circuit constants and power supply noise. As the phase θ11 to θ20
Phase control is possible within the period. Therefore, in the phase control circuit, when the effective value voltage of the AC power supply 1 is 100V, the effective value voltage supplied to the load 2 is 97 to 98.
There is a problem that it is V, that is, only 97 to 98% of the input voltage can be effectively used.

In order to solve this problem, in the phase control circuit of the above publication, the output from the sawtooth wave generation circuit is set to 2
The waveform is processed by using one comparison circuit and supplied to the latch circuit, and the output of the latch circuit controls the gate drive circuit to ignite the triac (not shown). However, this phase control circuit increases the number of parts,
It has the drawback of increasing the product cost.

Further, the above publication discloses a phase control circuit for controlling a gate circuit of a triac using a logic circuit. This will be described with reference to FIG. 8. In this phase control circuit, the AC power supply 1, the load 2, and the triac 3 form a closed loop, and a gate drive circuit 6 for firing the triac 3 is provided. Is controlled by the power supply synchronizing circuit 9, the counter circuit 20, the clock circuit 21, the monostable circuit 22, and the latch circuit 23, and causes the light emitting diode 7 of the gate drive circuit 6 to emit light through the latch circuit 23 to fire the triac 3. I am letting you.

In this phase control circuit, in synchronization with the voltage waveform of the AC power supply 1 of FIG.
The synchronization signal P4 shown in (2) is derived. This synchronizing signal P4 is a signal indicating that it is in the vicinity of the zero cross points θ30, θ40, ... And is inputted to the counter 20 and the monostable circuit 22. As shown in FIG. 9C, the counter circuit 20 subtracts in synchronization with the clock signal from the time when the synchronization signal P4 is inverted from L level to H level. The period in which the count value of the counter circuit 20 is zero is each period from time t1 to tla and t2 to t2a.

As shown in FIG. 9C, the counter circuit 2
At time t1 (phase angle θ31) when the count value of 0 becomes zero, as shown in FIG. 9 (4), if the output of the monostable circuit 22 is at H level, the output of the latch circuit 23 is at H level. The light is inverted to the L level to cause the light emitting diode 7 to emit light, and power is supplied to the load 2 via the triac 3. on the other hand,
In the vicinity of the phase angle θ40 (time t2), the counter circuit 2
0 is inverted from H level to L level in synchronization with the rising edge of L level to H level. As shown in FIG. 9 (5), the latch circuit 23 latches this L level and maintains the L level. Therefore, the ignition state is maintained near the phase angle θ40. By controlling the gate drive circuit 6 in this manner, electric power is effectively supplied to the load 2.

[0010]

In the phase control circuit of FIG. 6, a sawtooth wave is generated in the vicinity of the zero-cross point of the AC voltage in order to prevent the gate firing signal from being supplied to the triac 3 due to power source noise or the like. A signal is input from the circuit 4 to the comparison circuit 5 via the electric path L3 to prohibit the signal. The prohibited area W1 needs to be set relatively large in consideration of variations in circuit constants and influence of power supply noise. As a result, when expressed by the phase of the AC power supply with a half cycle of 180 degrees, the range of the phase angle in which the phase can be controlled becomes 145 degrees, which has a drawback that the utilization efficiency of power is very poor.

The above-mentioned publication discloses a phase control circuit that solves the above problems. Although this phase control circuit improves the power utilization efficiency, the circuit configuration becomes complicated and the number of parts is increased. Has the disadvantage of increasing the product cost. In particular, the phase control circuit of FIG. 8 has a drawback that a digital signal generating circuit such as a CPU (central processing unit) is required. These digital signal generating circuits have a drawback that they require a highly stabilized stabilizing power supply circuit because they are weak against pulse noise.

Further, this phase control circuit includes a logic circuit for controlling the gate drive circuit of the triac, and the circuit configuration becomes extremely complicated, and the number of parts also increases, which is extremely expensive. have.
In particular, if there is a demand to incorporate a soft start control circuit at low cost into the phase control circuit of the triac, it is not possible to use a phase control circuit having such an expensive logic circuit, and It is desired to develop a low-cost phase control circuit having the same.

The present invention has been made in view of the above-mentioned problems, and it is possible to perform phase control over substantially the entire range of the phase angle of the AC power source from 0 degree to 180 degrees, the number of circuit components is small, and the cost is low. Another object of the present invention is to provide a phase control circuit that can operate stably without malfunction due to variations in component constants and power supply noise. A further object of the present invention is to provide a phase control circuit having a soft start control circuit.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. The invention according to claim 1 is a transformer that forms a closed loop together with an AC power source and a load.
A gate drive circuit for firing the iac,
The alternating current is connected to the first and second output terminals of the iac.
Zero cross that generates a sync signal near zero volts of the power supply
Synchronization signal circuit, time constant setting capacitor, and time constant
Zener die connected to the discharge path of the setting capacitor
And an output signal of the zero-cross sync signal circuit.
The capacitor for setting the time constant in synchronization with the falling edge of the signal
Is a Zener voltage determined by the Zener diode.
The low level becomes the Zener voltage by discharging to the voltage.
Sawtooth wave generation circuit that generates a sawtooth wave and phase control
The electric potential of the control signal and the electric power of the output from the sawtooth wave generation circuit.
Input to the comparison circuit and output by the comparison circuit.
Phase control timing circuit for controlling the gate drive circuit
And a signal from the phase control timing circuit.
A light emitting diode of a photocoupler forming the gate driving circuit.
Featuring blinking control of the ion, gate drive circuit
The triac turns off when the gate current is supplied by the path.
The gate drive circuit automatically turns on the gate current.
To shut off the supply and allow the triac to fire automatically
The minimum required gate drive signal width is
The gate drive prohibition signal before and after zero crossing is not necessary.
Moreover, the zener in the discharge path of the sawtooth wave generation circuit
Saw by connecting the diodes in series
The L level potential of the wave output waveform is higher than the ground level.
Can be set to an arbitrary potential, and the minimum level of the phase control signal can be set.
Can be higher than the bell and the phase control signal
The gate of the triac by lowering the potential
The output of the drive circuit can be turned on continuously,
The phase control range can be expanded .

[0015]

[0016]

[0017]

The invention described in claim 2 is the same as claim 1.
In the invention described in paragraph 1,
A resistor connected in series and the resistor connected in parallel with the resistor
It consists of a diode that rapidly charges the capacitor
When the control signal is turned on, the capacitor is discharged through the resistor.
The sawtooth wave generating circuit in the comparison circuit.
The potential of the phase control signal compared with the potential of the output from
The phase control signal when the phase control signal is off.
The capacitor is charged through the diode and the comparison
And the potential of the output from the sawtooth wave generation circuit
The potential of the phase control signal to be compared is the peak voltage of the sawtooth wave.
And wherein <br/> comprise a slope generating circuit to rapidly change over pressure values gradually changing the phase control signal, input
Soft that gradually increases the phase angle from 0 degrees when the signal is on
Start function and phase control signal in a short time with 0 degree phase angle
Below, that is, above the peak voltage value of the sawtooth wave
Switch operation instantly when the input signal is off.
Possible quick-off can be realized .

The invention described in claim 3 is the same as that of claim 1.
Or in the invention described in 2, the phase control input signal is turned off.
Depending on the signal, the time constant setting of the sawtooth wave generation circuit
The low level of the constant-use capacitor is discharged below the Zener voltage.
Shut off the phase control timing circuit
Characterized by the provision of a triac stop signal circuit for extinguishing the ack , when the phase control input signal is in the off state,
The output of the sawtooth wave generation circuit is forced to the low level via the triac stop signal circuit, and the output of the phase control timing circuit is forcibly turned off at the same time when the input signal changes from on to off. as, it is possible to prevent the malfunction me by the triac power supply noise and the like.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a phase control circuit according to the present invention, in which a load 2 such as a heater circuit or a lamp lighting circuit and a triac 3 are connected in series to an AC power source 1 to form a closed loop, The triac 3 is controlled by the phase control circuit. The phase control circuit includes a gate drive circuit 11 connected to the first output terminal and the gate electrode of the triac 3, a zero-cross synchronizing signal circuit 12 connected between the first and second output terminals of the triac 3, and a zero-cross signal. The sawtooth wave generation circuit 13 generates a sawtooth wave according to the output of the synchronization signal circuit 12, and a phase control timing circuit 14 to which a sawtooth signal and a phase control signal are input. TRIAC stop signal circuit 15 in front of
Is provided.

The gate drive circuit 11 comprises a photocoupler 6 including a photothyristor 8 and a light emitting diode 7, and resistors R13 and R14. One end of the resistor R14 is connected to the first output terminal of the triac 3, the other end is connected to one end of the photothyristor 8, and the other end is connected to the gate electrode. The anode of the light emitting diode 7 is connected to the power supply voltage Vcc, and the cathode thereof is connected to the collector of the transistor T3 at the output stage of the phase control timing circuit 14 via the resistor R13.

The zero-cross synchronizing signal 12 is a photocoupler 17 for AC input composed of a light emitting diode LE and a phototransistor PT, a resistor R7 connected to the collector of the phototransistor PT, and resistors R8 and R9 connected in series. It is composed of a comparator circuit A1. A light emitting diode L is provided between the first and second output terminals of the triac 3.
E is connected, the collector of the phototransistor PT is connected to the power supply terminal via the resistor R7, and the emitter thereof is grounded. The connection point between the collector of the phototransistor PT and the resistor R7 is connected to the first input terminal of the comparison circuit A1, and the connection point between the resistors R8 and R9 is connected to the second input terminal of the comparison circuit A1 and its output The terminal is connected to the sawtooth wave generation circuit 13.

An output terminal of the sawtooth wave generation circuit 13 is connected to the phase control timing generation circuit 14. The phase control timing generation circuit 14 comprises a comparison circuit A2 and a transistor T3 at its output stage. The output terminal of the sawtooth wave generation circuit 13 is connected to the first input terminal of the comparison circuit A2, and the output terminal of the comparison circuit A2 has a transistor T3.
Of the transistor T3 is connected to the gate drive circuit 11, and the emitter of the transistor T3 is grounded.

The phase control signal input terminal to which the phase control input signal is input is connected to one end of the resistor R1, the other end is connected to the base of the transistor T1, and its collector is connected to the power supply terminal via the resistor R3. , Its emitter is grounded. Transistor T1 collector and resistor R
The connection point with 3 is connected to the second input terminal of the comparison circuit A2. A capacitor C3 is connected between the collector and emitter of the transistor T1.

Further, the triac stop circuit 15 is connected to the first input terminal of the comparison circuit A2, and the triac stop circuit 15 is connected to the transistor T2 and the connection point between its collector and the resistor R3 to the resistor R4. The other end is connected to the base of the transistor T2,
A resistor R5 is connected between the two bases and the emitter.
The collector of the transistor T2 is connected to the first input terminal of the comparison circuit A2.

In the present embodiment, the phase control input signal is input from the input terminal and is input as the phase control signal to the second input terminal of the comparison circuit A2 constituting the phase control timing generation circuit 14. The path to which the phase control signal is supplied is
The capacitor C3 is provided, and the capacitor C3 is
When the phase control input signal is off, it is rapidly charged through the resistor R3, and when the phase control input signal is on, the transistor T1
Be discharged through. A resistor may be connected to the emitter of the transistor T1 in order to obtain a sufficient time constant when discharging the capacitor C3. Further, it is obvious that the phase control circuit can be formed even when the capacitor C3 is not connected between the second input terminal of the comparison circuit A2 and the ground. The operation of the phase control circuit shown in FIG. 1 will be described below.

Next, another embodiment according to the phase control circuit of the present invention will be described with reference to FIG. In the figure,
1 is different from that of the embodiment of FIG.
Although the part input via 6 is different, the other parts have the same circuit configuration. The same parts as those in FIG. 1 are designated by the same reference numerals.

In FIG. 2, a load 2 such as a heater circuit and a lamp lighting circuit and a triac 3 are connected in series to an AC power source 1 to form a closed loop, and the triac 3 is controlled by a phase control circuit. . The phase control circuit
A gate drive circuit 11 connected to the first output terminal of the triac 3 and the gate electrode, and a zero-cross sync signal circuit 1 connected between the first and second output terminals of the triac 3.
2, a sawtooth wave generation circuit 13 that generates a sawtooth wave according to the output of the zero-cross synchronizing signal circuit 12, a phase control timing circuit 14 to which the sawtooth wave and a phase control signal are input, and a slope generation circuit 16. , In addition,
A triac stop signal circuit 15 is provided in the preceding stage of the phase control timing circuit 14. Further, the slope generation circuit 16 receives the phase control input signal via the phase control input terminal and operates according to the input signal, and the phase control signal is supplied to the phase control timing circuit 14 via the slope generation circuit 16. It is input to the second input terminal of the composing circuit A2.

FIG. 5 shows another embodiment of the phase control circuit of the present invention, which is implemented by a sawtooth wave generation circuit 13, a phase control timing circuit 14, and a slope generation circuit 16 as concrete circuits. An example is shown. The sawtooth wave generation circuit 13 includes a Zener diode D2 and a resistor R.
10 and a series circuit of a capacitor C2, one end of the zener diode D2 is connected to the output terminal of the comparison circuit A1 of the zero-cross synchronization signal circuit 12, and the other end is connected to the connection point of the resistor R10 and the capacitor C2. Has been done.

The phase control timing circuit 14 includes resistors R11 and R12 connected in series between the comparison circuit A2 and the power supply terminal.
And a transistor T3, and a zener diode D2 which is an output terminal of the sawtooth wave generation circuit 13,
The connection point between the resistor R10 and the capacitor C2 is the comparison circuit A.
2 is connected to the first input terminal of the comparator 2, and the output terminal of the comparison circuit A2 is the base of the transistor T3 and the resistors R11 and R12.
It is connected to the connection point with.

The slope generation circuit 16 includes a diode D1
And resistor R6 in parallel circuit, time constant setting capacitor C
1 and a transistor T1 of the phase control input circuit
The collector of is connected to the capacitor C1 through the parallel circuit of the diode D1 and the resistor R6, and the second circuit of the comparison circuit A2 is connected.
Is connected to the input terminal of. The other end of the capacitor C1 is grounded. Note that the specific circuits of the sawtooth wave generation circuit 13, the phase control timing circuit 14, and the slope generation circuit 16 shown in FIG. 5 are applied to FIGS. 1 and 2, but of course they are shown in FIG. It is not limited to a specific circuit.

The operation of the phase control circuit shown in FIGS. 1, 2 and 5 will be described below with reference to FIGS. 3 and 4. The embodiment of FIG. 2 will be mainly described with reference to the specific circuit of FIG. 5 as necessary. Prior to explaining the operation, FIG.
The waveform diagram will be described with reference to FIG. FIG. 3A shows an AC voltage waveform of the AC power supply 1. FIG. 3B shows the photocoupler 1 which is the input stage of the zero-cross synchronizing signal circuit 12.
7 shows the output waveform of No. 7. FIG. 3 (3) shows the output waveform of the sawtooth wave generation circuit 13. FIG. 3 (4) shows the output waveform of the comparison circuit A2 of the phase control timing circuit 14. FIG. 4A shows the input waveform of the phase control input signal. FIG. 4B shows the operation waveform of the slope generation circuit 16.

In the phase control circuit of FIG. 2, the phase control input signal is inputted from the phase control input terminal, and the phase control signal constitutes the phase control timing circuit 14 of the comparison circuit A.
2 is input to the second input terminal. When the phase control input signal is input through the transistor T1, the comparison circuit A2
An L-level phase control signal that is the inversion of the H-level signal is input to the second input terminal of the. In the embodiment of FIG. 2, the slope generation circuit 16 is provided, and the phase control timing circuit 14 receives a second signal from the phase control input signal.
A phase control signal that becomes L level by gradually lowering the potential with respect to the H level signal is input to the input terminal of.

First, the zero-cross synchronizing signal circuit 12 is a photo coupler 17 for AC input, and is a light emitting diode LE.
When the AC voltage passes near zero volt, the light emission is stopped because the voltage is not applied between the terminals of the light emitting diode LE. At this time, the phototransistor PT of the photocoupler 17 also similarly receives the photocurrent (collector current). ) Is stopped, a synchronization signal is output near the AC voltage of zero volt, as shown in FIG. Further, when the triac 3 is conductive, the potential between the first and second output terminals thereof becomes substantially zero, so that the light emitting diode LE is turned off and the collector potential of the phototransistor PT is maintained at the H level.

Comparison circuit A of the zero-cross synchronizing signal circuit 12
At 1, the synchronizing signal is amplified and the inverted signal is transmitted to the sawtooth wave generating circuit 13. Before and after the zero-cross point, the output of the comparison circuit A1 is at L level, and the output of the sawtooth wave generation circuit 13 is also at L level. After passing through the vicinity of the zero cross point, the output of the comparison circuit A1 is in an open state, and its voltage increases until the next zero cross point. When the output of the photocoupler 17 becomes H level in the vicinity of the next zero cross point, the output of the comparison circuit A1 becomes L level, and therefore the comparison circuit A1 is discharged. By repeating this operation, a sawtooth waveform rising to the right as shown in FIG. 3C is formed.

Next, the phase control operation will be described. The phase control input signal is input to the phase control input terminal, and the voltage level of the phase control signal and the voltage due to the sawtooth wave from the sawtooth wave generation circuit 13 are compared by the comparison circuit A2 of the phase control timing circuit 14 to perform the phase control operation. .

As is apparent from FIGS. 3 (3) and 3 (4),
When the potential of the phase control signal is larger than the peak voltage of the sawtooth wave, the output of the comparison circuit A2 becomes L level, the transistor T3 of the phase control timing circuit 14 is turned off, and the light emitting diode of the photocoupler 6 of the gate drive circuit 11 is turned on. 8 is in the off state. Therefore, triac 3
Since no gate current is supplied to the triac 3, the triac 3 remains off. This control state is when the phase angle is 0 degree.

After passing near the zero cross point,
When the output of the comparator circuit A1 is in an open state, the potential of the sawtooth up to the next zero cross point rises, reaches the potential of the phase control signal, or becomes a voltage lower than the peak voltage of the sawtooth, the potential of the sawtooth becomes To descend. When the peak voltage of the sawtooth wave becomes higher than the potential of the phase control signal, the output of the comparison circuit A2 is opened, the triac T3 of the phase control timing circuit 14 is turned on, and the light emitting diode 7 of the photocoupler 6 of the gate drive circuit 11 is turned on.
Lights up and gate current is supplied to the triac 3.
The triac 3 is ignited and turned on. When the triac 3 is turned on, the zero cross synchronization circuit 1
Since no voltage is applied between the terminals of the light emitting diode LE of No. 7, no current flows through the light emitting diode LE of the photocoupler 17, and the phototransistor PT of the photocoupler 17 is also turned off. The output of the comparison circuit A1 also becomes L level, the potential of the output voltage of the sawtooth wave generation circuit 13 also becomes L level, and the output of the comparison circuit A2 of the phase control timing circuit 14 also becomes L level. The transistor T3 at the output stage of the comparison circuit A2 is turned off, and the light emitting diode 7 of the gate drive circuit 11 is turned off. However, once the triac 3 is ignited, the triac 3 remains in the on state for a half cycle of the alternating current and becomes the off state at the zero cross point.

By repeating the operation described above, the voltage level of the phase control signal input to the first and second input terminals of the comparison circuit A2 of the phase control timing circuit 14 and the output voltage of the sawtooth wave generation circuit 13 The triac 3 is ignited at a phase angle determined by the electric potential of the electric power of the electric power of the electric power and the electric power is supplied to the load 2 by the phase control operation. Also, FIG.
As is apparent from (3), when the voltage level of the phase control signal is lower than a predetermined threshold value, for example, the Zener voltage Vz, the light emitting diode LE of the photocoupler 17 is in the off state, and the phase control is immediately performed at the zero cross point. The output of the comparison circuit A2 of the timing circuit 14 becomes H level, the transistor T3 is turned on, the light emitting diode 7 of the gate drive circuit 11 is turned on, the triac T3 is ignited, and the on state is maintained. By controlling the triac 3 in this manner, the effective power efficiency can be made approximately 100%.

As is apparent from the above, the characteristic of the operation of the phase control circuit in this embodiment is that the light emitting diode 7 of the gate drive circuit 11 is automatically turned off when the triac 3 is ignited and turned on. Is. Of course, as explained above, once the TRIAC 3 is fired,
It remains on until the next zero-cross point and can be turned on immediately at turn-off. The effect is that there is no need to provide a signal for prohibiting the gate drive circuit 11, the number of parts can be reduced, and the phase controllable range can be set large.
Furthermore, it can be achieved with a simple circuit configuration.

Further, by providing a zener diode D2 between the output of the comparison circuit A1 of the zero-cross synchronizing signal circuit 12 and the sawtooth wave generating circuit 12, the zener diode D2 is discharged to a voltage determined by the zener diode D2. That is, as is apparent from FIG. 3C, the L-level potential of the sawtooth wave obtained from the sawtooth wave generation circuit 12 can be used as the zener voltage (Vz). By lowering the potential of the phase control signal below the Zener voltage (Vz), the light emitting diode 7 of the gate drive circuit 11 can be turned on, and the triac 3 can be fired again even if the triac 3 is turned off at the zero cross point. it can.

With this circuit configuration, the voltage level of the phase control signal can be set lower than the L level of the sawtooth potential, and the phase angle of 180 degrees of the AC power supply 1 is set to the ON state. Therefore, the light emitting diode of the gate drive circuit can be continuously lit. That is,
This means that the voltage level of the phase control signal can be set wider than the range of the peak voltage of the sawtooth wave from the zener voltage Vz, which means that the phase control can be realized in the range of the phase angle of 0 degrees to 180 degrees, and the power usage efficiency is improved. Can be set to approximately 100%.

Further, in the phase control circuit of the embodiment shown in FIGS. 2 and 5, the slope generation circuit 16 is provided in the phase control input signal stage.
Bei Eteori, on-off of the input signal, has a function of gradually changing the phase control signal. That is, the soft start function can be given to the phase control circuit by gradually increasing the phase angle from 0 degree when the input signal is on. When the input signal is off, the capacitor C1 is rapidly charged through the diode D1 arranged in parallel with the resistor R6, so that the phase control signal can have a phase angle of 0 degrees or less in a short time.
That is, by setting the peak voltage value of the sawtooth wave or more , it is possible to instantaneously perform the switching operation when the input signal is off. So-called quick-off can be realized.

Further, the triac stop circuit 15 is provided with the triac stop signal circuit 1 when the input signal is in the off state.
The output of the sawtooth wave generation circuit 13 can be forcibly turned off via the circuit 5. Therefore, there is an advantage that a malfunction due to an external noise mixed in the power supply line or the like can be prevented.
Although the output signal of the sawtooth wave generation circuit is forcibly set to the low level in this embodiment, the output of the comparison circuit A2 of the phase control timing circuit 14 is forcibly set to the low level. Good.

Further, in this embodiment, the zero-cross synchronizing signal circuit is constructed by using a photocoupler for AC input. However, although the number of parts increases, a rectifier circuit such as a bridge diode and a series type photocoupler are used. Obviously, it may be configured as follows.

[0046]

As described above, according to the present invention,
The phase control circuit can be configured by a relatively simple circuit without using a logic circuit such as a digital signal generation circuit and a CPU, and the number of parts can be reduced, so that a low-cost phase control circuit can be provided. There is.
Further, according to the present invention, the phase angle of the AC power source is changed from 0 degree to 1 degree.
It is possible to control almost the entire area of 80 degrees, and there is an advantage that the utilization efficiency of the electric power supplied to the load can be set to approximately 100%.

Further, according to the present invention, since the slope generation circuit is provided at the input stage of the phase control signal, the soft start control function can be provided at the time of starting the phase control circuit. There is an advantage that a small number of phase control circuits can be provided, and according to the phase control circuit of the present invention, the slope generation circuit can be achieved by an extremely simple circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a phase control circuit according to the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the phase control circuit according to the present invention.

FIG. 3 is a waveform diagram for explaining the operation of the embodiment.

FIG. 4 is a waveform diagram for explaining the operation of the embodiment.

FIG. 5 is a circuit diagram showing another embodiment of the phase control circuit according to the present invention.

FIG. 6 is a circuit diagram showing another example of a conventional phase control circuit.

FIG. 7 is a waveform diagram for explaining the operation of the phase control circuit of FIG.

FIG. 8 is a circuit diagram showing another example of a conventional phase control circuit.

9 is a waveform diagram for explaining the operation of the phase control circuit of FIG.

[Explanation of symbols]

1 AC power supply 2 load 3 triacs 6 Photo coupler 7 Light emitting diode 8 Photothyristors 11 Gate drive circuit 12 Zero-cross sync signal circuit 13 sawtooth wave generation circuit 14 Phase control timing generator 15 TRIAC stop signal circuit 16 Slope generation circuit 17 Photocoupler A1, A2 comparison circuit D1 diode D2 Zener diode LE light emitting diode PT phototransistor

Claims (3)

(57) [Claims] 1. A closed loop is constructed with an AC power source and a load.
Gate drive circuit for firing the triac
And connected to the first and second output terminals of the triac,
A generator for generating a synchronization signal near the zero volt of the AC power supply.
Rocross sync signal circuit, time constant setting capacitor, and time constant setting capacitor
And a Zener diode connected to the discharge path of
For the fall of the output signal of the zero-cross sync signal circuit
Synchronize the time constant setting capacitor with the Zener
Discharge to the Zener voltage determined by the ion
The sawtooth wave with a low level as the Zener voltage.
The sawtooth wave generation circuit that is generated, the potential of the phase control signal and the output from the sawtooth wave generation circuit.
Input the force potential to the comparison circuit and output the comparison circuit.
Phase control timing for controlling the gate drive circuit by
And a signal from the phase control timing circuit.
The light emitting diode of the photocoupler that forms the dynamic circuit.
Phase control circuit, wherein the blinking controller child. 2. A capacitor and a capacitor connected in series
And a capacitor connected in parallel with the resistor.
It consists of a diode that rapidly charges the
Sometimes the capacitor is discharged through the resistor
Of the output from the sawtooth wave generation circuit in the comparison circuit
Gradually change the potential of the phase control signal compared to the potential.
And when the input signal is off,
Charge through the ion
Phase compared to the potential of the output from the sawtooth generator
Rapid control signal potential over the peak voltage value of sawtooth wave
It is characterized by having a slope generation circuit that changes
The phase control circuit according to claim 1 . 3. According to the off signal of the phase control input signal,
Capacitor for setting the time constant of the sawtooth wave generating circuit
The low level of is discharged below the Zener voltage and the phase control
Turn off the timing circuit to extinguish the triac
Characterized in that a triac stop signal circuit that
The phase control circuit according to claim 1 .