JPS629998B2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a light control device.

As shown in Figure 1, a conventional light control device includes an AC power source E and a lamp powered by the AC power source E.
A triac TC for phase control is connected to both ends of a series circuit consisting of a power switch SW that starts and stops power supply to the LP and the lamp LP through a noise prevention circuit consisting of a choke coil L and a capacitor _C1 .
is connected. Also, T ₁ of Triack TC
Resistor R ₁ and capacitor between terminals and T ₂ terminals
Zener diode ZD is connected through C ₂ ,
The voltage taken out from both ends of this Zener diode ZD is converted into direct current by a rectifier/smoothing circuit consisting of a diode _D1 and a capacitor _C3 , and then supplied as a power source to the subsequent circuit. A series circuit of resistors R ₂ and R ₃ is connected to the output end of this rectifying/smoothing circuit, that is, both ends of the capacitor C ₃ , and the collector and emitter of the transistor TR ₁ are connected in parallel to the resistor R ₃ . In addition, a capacitor C ₄ for supplying the base current to the base of the transistor TR ₁
and a resistor R ₄ are connected in series, and a diode D ₂ is connected in parallel to the series circuit consisting of the resistor R ₄ and the base-emitter of the transistor TR ₁ .
A series circuit of resistor R ₅ and diode D ₃ is connected in parallel with resistor R ₂ , resistor R ₅ and diode D ₃
Touch plate TP is connected to the connection point of , via a series circuit of resistors R ₆ and R ₇ . On the other hand, resistance
The connection point _of R ₅ and _{R 6} is connected _to a touch control electronic dimmer MOS integrated Circuit S566 (manufactured by Siemens) is connected to input terminal _F3 of F. The output terminal _F4 of this touch dimming control section F is a resistor.
It is connected to the base of the transistor TR ₂ connected in series to the series circuit of R ₈ and R ₉ . This resistance R ₈ ,
The series circuit of _R9 and transistor _TR2 is connected in parallel to capacitor _C3 , and the connection point of resistors _R8 and _R9 is connected to the gate of triac TC. In this case, the touch dimming control section F changes the output pulse of the output terminal _F4 by applying _a negative voltage from the positive side power supply terminal _F1 to the input terminal F3.
The voltage changes as follows depending on the voltage applied to input terminal _F3 . That is, (1) When a pulsed negative potential is applied, (1A) If an output pulse is being generated from the output terminal _F4 , the generation is stopped (dimming on → off).

(1B) If an output pulse is not generated from output terminal _F4 , start generating it (light off → maximum lighting).

(2) When a negative potential is applied for a long period of more than a certain value, a pulse is generated from the output terminal _F4 to advance or delay the trigger phase angle of the LIAC TC during that period, and when the negative potential is removed,
Retains the previous state.

Note that the power supply frequency synchronization terminal _F5 of the touch dimming control unit F is connected to _T2 of the triac TC via a resistor _R10 .
connected to the terminal.

Next, the operation of this light control device will be explained in detail. When the power switch SW is turned on, AC power supply E → Lamp LP → York coil L → Capacitor C ₄ → Resistor R ₄ → Between base and emitter of transistor TR ₁ → Diode D ₁ → Capacitor C ₁ → Resistor
A pulsed bias current flows to the base of transistor TR ₁ through the path R ₁ → power switch SW → AC power supply E, transistor TR ₁ is turned on instantaneously, and the potential at point T drops, so that The potential at point U drops. As a result, the touch dimming control unit F
controls the trigger phase of the triac TC so that the lamp LP lights up at its maximum. In other words, at the phase angle where the lamp LP is at its brightest, the output terminal
An output pulse is generated from _F4 , which turns on transistor _TR2 and causes a trigger current to flow through triac TC, making triac TC conductive. In this case, the trigger current of the triac TC is synchronized with the power supply frequency, and when the _T1 terminal has a higher potential, the light current power supply E → lamp LP → choke coil L → _T1 terminal of the triac TC → the same gate → resistor _R9 → Collector of transistor TR ₂ → Emitter of transistor TR 2 → Diode D ₁
→ Capacitor C ₂ → Resistor R ₁ → Power switch SW → Flows through the path of AC power supply E, and when the T ₂ terminal has a higher potential, the positive side of capacitor C ₃ → T ₁ terminal of triac TC → Same gate → Resistor R ₉ → Collector of transistor TR ₂ → Emitter of the same → Capacitor C ₃
flows through the path on the negative side of .

Also, when the human body M touches the touch plate TP, the AC power supply E → lamp LP → chiyoke coil L
→Resistance R ₅ →Resistance R ₆ →Resistance R ₇ →Touch plate TP
→Human body M → Earth → A weak current flows through the path of AC power supply E, which causes the potential at point U to drop.
Lamp LP blinks or dims.

Note that the resistance values of resistors R ₂ and R ₃ are
The selection is made so that when TR ₁ is off, the potential at point U will not drop more than necessary than the potential at point S.

However, in such a conventional light control device, the electric charge of the capacitor C ₃ used for smoothing is discharged through the impedance of the peripheral circuit of the capacitor C ₃ when the power switch SW is turned off, so the discharge time constant is large and the touch adjustment is difficult. The voltage Vc ₃ across the capacitor C ₃ that is applied as a power supply voltage to the light control unit F drops slowly, causing the following problem. That is, as shown in Fig. 3, when the power switch SW is turned off, the voltage Vc ₃ across the capacitor C ₃ increases to the guaranteed operation lower limit voltage of the touch dimming control unit F (in order to ensure stable operation of the touch dimming control unit F). (The lower limit of the power supply voltage required for this purpose) begins to fall from a normal voltage higher than V _D.

Power switch is turned off immediately after turning off the power switch SW.
When the SW is turned on again, the voltage Vc ₃ across the capacitor C ₃ suddenly returns to the normal voltage value before dropping to zero. At this moment, U
Since the signal also enters the point, the touch dimming control unit F
The lamp operates at a power supply voltage lower than the guaranteed operation lower limit voltage V _D , and the operation at this time is unstable, causing the lamp to flicker. In addition, in FIG. 3, V _U is the operation guaranteed upper limit voltage of the touch dimming control section F.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a light control device that can prevent a lamp from flickering when the power switch is turned off and then immediately turned back on.

An embodiment of this invention is shown in FIG. In other words, this light control device has a resistor _R11 connected between the anode and cathode of the thyristor SR at both ends of the capacitor _C3 .
Connect the parallel circuit with the series circuit of capacitor C ₅ and connect the trigger element TG between the connection point of resistor R ₁₁ and capacitor C ₅ and the gate of thyristor SR, and connect the output of photocoupler PC in parallel with capacitor C ₅ . Connect the collector and emitter of the transistor PC ₁ , and connect the capacitor C ₆ and the input diode of the photocoupler PC in parallel with the Zener diode ZD.
A series circuit of PC ₂ and resistor R ₁₂ is connected, and the other configuration is the same as the conventional example.

The operation of this light control device that is different from the conventional example will be explained. When the power switch SW is turned on, the lamp LP lights up at its maximum as described above, but at this time, the potential rises with a time constant determined by the resistor _R11 and the capacitor _C5 using the capacitor _C3 as the power source. In this case, the time constant until the potential of the capacitor _C5 reaches the operating voltage of the trigger element TG is longer than the period of each one cycle of the power supply, and each
At the beginning of the cycle (for example, about 22 m ^sec at 50 Hz,
If the frequency is 60Hz, the time constant is approximately 18m ^sec ), so that the thyristor SR conducts. However,
Before the potential of capacitor C ₅ reaches the operating voltage of trigger element TG, that is, the voltage generated in triact TC every cycle causes a current to flow through the series circuit of capacitor C ₆ , input diode PC ₂ of photocoupler PC, and resistor R ₁₂ . current, input diode
PC ₂ emits light. This light emission from the input diode PC ₂ turns on the output transistor PC ₁ instantaneously, and the charge in the capacitor C ₅ is rapidly discharged. After discharging, the capacitor C ₅ starts charging again from zero, and is charged every cycle. This operation is repeated until the thyristor SR remains off when the power switch SW is turned on.

However, when the power switch SW is turned off, no voltage is generated across the triac TC even though there is charge remaining in the capacitor _C3 , so the input diode _PC2 does not emit light and the potential of the capacitor _C5 decreases. increases and reaches the operating voltage of the trigger element TG, causing the thyristor SR to conduct and rapidly discharging the charge in the capacitor _C3 .

In this way, in response to turning off the power switch SW, the charge in the capacitor C ₃ used for smoothing is rapidly discharged, and the voltage Vc ₃ across the capacitor C ₃ quickly drops to zero.
As soon as the SW is turned off, the touch dimming control section F
Even if the operation of the touch switch completely stops and the power switch SW is turned off and then turned on again, the touch dimming control unit F may operate unstablely at a voltage lower than the guaranteed operation lower limit voltage V _D. without a capacitor
A regular voltage is quickly generated across _C3 , and a pulse signal with a regular and stable phase is obtained from the output terminal _F4 of the touch dimming controller F, thereby preventing flickering of the lamp LP.

As described above, in the light control device of the present invention, the charge in the smoothing capacitor is rapidly discharged in response to turning off the power switch, and the operation of the light control unit is immediately completely stopped. When you turn it off and then turn it back on immediately,
It does not cause unstable operation and has the effect of preventing lamp flickering.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional light control device, FIG. 2 is a circuit diagram of a light control device according to an embodiment of the present invention, and FIG. 3 is a waveform diagram for explaining the drawbacks of the conventional example. E...AC power supply, LP...lamp, TC...triax, SW...power switch, _D1 ...diode, _C3 ...
Capacitor, F...Touch dimming control unit, SR...Thyristor, TG...Trigger element, _R11 ...Resistor, _C5 ...Capacitor, PC...Photocoupler.

Claims (1)

[Claims] 1. A phase control thyristor connected in a loop to a series circuit of an AC power supply and a lamp, a power switch interposed in the loop circuit of the AC power supply, lamp and phase control thyristor, and a power switch of the phase control thyristor. a diode and a capacitor that rectify and smooth the voltage taken out from both ends; a dimming control unit that uses the voltage across the capacitor as a power source to control the conduction phase of the phase control thyristor to blink and dim the lamp; and a discharge circuit that instantaneously short-circuits both ends of the capacitor in response to turning off the power switch.