JPH0697810B2 - AC control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a bidirectional thyristor or an antiparallel connected 2
The present invention relates to an AC control circuit that uses a plurality of reverse blocking thyristors or the like as a phase control element to phase control the power supplied from an AC power supply to a load.

[Conventional technology]

 FIG. 4 shows a conventional general AC control circuit.

In FIG. 4, E is an AC power source, LD is a load such as an incandescent lamp, T ₁ is a phase control element made of, for example, a bidirectional thyristor, and T ₂ is a Triliga element made of, for example, a bidirectional trigger diode. VR ₁ is a variable resistor and C ₁ is a capacitor, which determine the trigger timing of the phase control element T ₁ . R ₁
Is provided for protection when the resistance value of the variable resistor VR ₁ becomes zero, and the maximum load power is determined by the resistance value of the resistor R ₁ .

As is well known, this AC control circuit causes the trigger element T ₂ to operate when the voltage of the capacitor C ₁ charged through the resistor R ₁ and the variable resistor VR ₁ exceeds the breakover voltage V _{B 0} of the trigger element T _2. The phase control element T ₁ is turned on by turning on. This operation is repeated for each half-wave of the voltage of the AC power supply E, and the power supply to the load LD is controlled by changing the resistance value of the variable resistor VR ₁ and changing the trigger timing of the phase control element T _1. You can In this case, for example, the brightness of the incandescent lamp is adjusted.

FIG. 5 is the fourth diagram when the resistance value of the variable resistor VR ₁ is increased.
FIG. 6 is a waveform diagram of each part of the figure, FIG. 6 is a waveform diagram of each part of FIG. 4 when the resistance value of the variable resistor VR ₁ is reduced, and in each figure, (a) shows the load current I _LD and (b) ) Is the voltage V _C of capacitor C _1
1 is shown.

[Problems to be Solved by the Invention]

In the AC control circuit shown in FIG. 4, when the resistance value of the variable resistor VR ₁ is further increased, the voltage of the capacitor C ₁ becomes a breakover voltage of the trigger element T ₂ during a half wave of the voltage of the AC power source E.
The state in which V _{B 0} is not reached and the trigger element T ₂ is not conducting, that is, the phase control element T ₁ is in the all cutoff state. In this state, the residual charge at the end of each period of the voltage of the AC power source E to the capacitor C _1, the voltage V _X remains in the capacitor C _1. This voltage V _X is opposite to the voltage polarity in the next half wave,
Charging after releasing the residual charge of the capacitor C ₁ of the capacitor C ₁ will be begin.

FIG. 7 is a waveform diagram of each part in FIG. 4 when the resistance value of the variable resistor VR ₁ is sufficiently large and the trigger element T ₂ is not conductive, and (a) and (b) are FIG. 5 and FIG. 6, respectively. The waveform of the same part as is shown.

As described above, the charge on the capacitor C ₁ remains, if decreasing the resistance of the variable resistor VR ₁ to start power supply to the load LD, the amount corresponding to extra resistance of the variable resistor VR ₁ residual charge Must be small. Therefore, the variable resistance
When the power supply starts when the power supply to the load LD is started by decreasing the resistance value of VR ₁ and when the power supply is stopped when the power supply to the load LD is stopped by increasing the resistance value of variable resistor VR _1. A hysteresis phenomenon occurs that is different from the resistance value of. As a result, the position of the knob of the variable resistor VR ₁ when power feeding starts and the position of the knob of the variable resistor VR ₁ when power feeding stops are not the same.

FIG. 8 shows the relationship between the resistance value of the variable resistor VR ₁ and the power supplied to the load LD (hysteresis characteristic), FIG. 9 shows the slide type variable resistor 1, and FIG. 10 shows the rotary type variable resistor. The resistor 2 is shown. Reference numerals A to D in FIG. 8 respectively correspond to positions A to D of the knob 1a of the variable resistor 1 of FIG. 9 and positions A to D of the mark 2b of the knob 2a of the variable resistor 2 of FIG. There is.

In the variable resistors 1 and 2 shown in FIGS. 9 and 10, the knob 1
When a, 2a is moved from the position of D to the position of B via the positions of C and A, and then returned from the position of B to the position of D via the positions of A and C, As the resistance value changes, the power supplied to the load LD changes as shown in FIG. Therefore, in order to start the power supply to the load LD, it is necessary to move the knobs 1a and 2a to the position A, and to stop the power supply to the load LD, it is necessary to return the knobs 1a and 2a to the position C. .

As described above, in the conventional AC control circuit, the variable resistor VR ₁
Since there is a hysteresis characteristic between the resistance value of and the electric power supplied to the load LD, there is a problem that the operation of adjusting the electric power cannot be smoothly performed.

An object of the present invention is to provide an AC control circuit capable of smoothly adjusting the supplied power.

[Means for Solving the Problems]

An AC control circuit according to the present invention includes a series circuit of a variable resistor and a first capacitor, in which a phase control element is inserted in a power supply path from an AC power supply to a load, and which is supplied with power from the AC power supply.
Is provided with a trigger element that conducts when the voltage across both ends of the capacitor exceeds a predetermined value to trigger the phase control element, and the series circuit of the resistor and the second capacitor fed from the AC power supply is connected in parallel with the first capacitor. A three-terminal switching element is provided which is connected and conducts when the voltage across the second capacitor exceeds a predetermined value.

In this case, the time constant of the series circuit of the resistor and the second capacitor is set so that the three-terminal switching element conducts at the end of each half wave of the voltage of the AC power supply.

[Action]

According to the configuration of the present invention, the three-terminal switching element becomes conductive at the end of each half-wave of the voltage of the AC power supply, and the first capacitor is forcibly discharged. As a result, even when the resistance value of the variable resistor is sufficiently large and the trigger element does not conduct during the half wave, the residual charge of the first capacitor can be reduced to zero at the end of the half wave. It is possible to eliminate the hysteresis characteristic between the resistance value of the variable resistor caused by the electric charge and the electric power supplied to the load.

〔Example〕

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

FIG. 1 shows a circuit diagram of an AC control circuit according to an embodiment of the present invention. In this AC control circuit, a series circuit of a resistor R ₂ and a capacitor C ₂ is connected in parallel to a series circuit of a variable resistor VR ₁ and a capacitor C ₁ and, for example, SBS (or a resistor and a capacitor to obtain a necessary potential are used. Bidirectional 3-terminal switching element T ₃
Is connected in parallel to capacitor C ₁ and the voltage of capacitor C ₂ is 3
In addition to the gate of the terminal switching element T ₃ .

In this case, set the time constant of the resistor R ₂ and capacitor C ₂ to the AC power source E
3-terminal switching element T ₃ at the end of each half-wave of the voltage is set so as to conduct.

Other configurations are similar to those of the AC control circuit shown in FIG.

In this AC control circuit, the capacitor C ₂ is charged through the resistor R _{2 for} each half-wave of the AC power supply E, and the three-terminal switching element T ₃ becomes conductive at the end of the half-wave of the voltage of the AC power supply E and the capacitor C ₁ is charged. It will release an electric charge. As a result, even if the variable resistor VR ₁ is made sufficiently large so that the trigger element T ₂ does not conduct at all during the half wave, that is, even when the power supply to the load LD is lost, the charge of the capacitor C ₁ is equal to that of each half wave. It is discharged at the end and there is no residual charge on the capacitor C ₁ . Therefore, the resistance value of variable resistor VR ₁ and load L
The problem of hysteresis characteristics with the power supplied to D will be solved. Therefore, the adjustment operation of the electric power supplied to the load LD by adjusting the variable resistor VR ₁ can be smoothly performed.

The operation in the case where the resistance value of the variable resistor VR ₁ is small and the trigger element T ₂ conducts by the end of the half wave of the voltage of the AC power source E to trigger the phase control element T ₁ is shown in FIG. Also in this case, the three-terminal switching element T ₃ once becomes conductive at the half-wave end of the voltage of the AC power source E.

FIG. 2 shows the relationship between the resistance value of the variable resistor VR ₁ and the electric power to the load LD (non-hysteresis characteristic).

Figure 3 is a waveform diagram in a state in which the resistance value sufficiently large trigger element T ₂ do not conduct the variable resistor VR _1, (a) is a load current I _LD, (b) the voltage V _{C 1} of the capacitor C ₁ Is shown. This figure from the charge of the capacitor C ₁ by a half-wave end of the voltage of the AC power supply E is released, it is clear that the voltage V _{C 1} of the capacitor C ₁ becomes zero.

In the above embodiment, a bidirectional thyristor, so-called triac, is used as the phase control element T ₁ , but two thyristors connected in anti-parallel may be used. Also, as the trigger element T ₂ , various voltage response switching elements other than those described in the embodiments can be used.

〔The invention's effect〕

According to the AC control circuit of the present invention, the second resistor, the second capacitor, and the three-terminal switching element are provided and the first resistor is provided.
Since the electric charge of the capacitor is released at the half-wave end of the voltage of the AC power supply, it is possible to eliminate the hysteresis characteristic between the resistance value of the variable resistor and the power supplied to the load. The adjustment operation of the power supplied to the load can be smoothly performed.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an AC control circuit according to an embodiment of the present invention,
2 is a characteristic diagram showing the relationship between the resistance value of the variable resistor and the power supplied to the load in the circuit of FIG. 1, and FIG. 3 is the characteristic diagram of FIG. 1 when the resistance value of the variable resistor is set sufficiently large. Waveform diagrams of each part of the circuit, FIG. 4 is a circuit diagram of a conventional example of the AC control circuit, FIG. 5 is a waveform diagram of each part of FIG. 4 when the resistance value of the variable resistor is set large, and FIG. 6 is variable. FIG. 8 is a waveform diagram of each part of FIG. 4 when the resistance value of the resistor is set small, and FIG. 7 is a waveform diagram of each part of the circuit of FIG. 4 when the resistance value of the variable resistor is set sufficiently large, FIG. 4 is a characteristic diagram showing the relationship between the resistance value of the variable resistor and the electric power supplied to the load in the circuit of FIG. 4, FIG. 9 is a perspective view of a slide type variable resistor, and FIG. 10 is a rotary type variable resistor. 3 is a perspective view of the external appearance of FIG. E ...... AC power source, LD ...... load, T ₁ ...... phase control element, T ₂
...... Trigger element, T ₃ …… 3-terminal switching element, VR ₁
...... Variable resistance, R ₂ ...... Resistance, C ₁ , C ₂ ...... Capacitor

Claims (1)

[Claims] 1. A phase control element inserted in a power feeding path from an AC power source to a load, a series circuit of a variable resistor and a first capacitor fed from the AC power source, and a voltage across the first capacitor. Is connected when the voltage exceeds a predetermined value to trigger the phase control element, a series circuit of a resistor and a second capacitor fed from the AC power source, and a parallel connection to the first capacitor. And a three-terminal switching element to which the voltage of the second capacitor is applied to the gate, wherein the resistor and the second capacitor are connected in series so that the three-terminal switching element conducts at the end of each half-wave of the voltage of the AC power supply. An AC control circuit that sets the time constant of the circuit.