JPH0355280Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a dimmer circuit for a discharge lamp that controls the phase of AC power supplied to the discharge lamp.

[Prior art]

FIG. 3 shows a conventional dimming circuit for a discharge lamp, in which 1 is an AC power source, 2 is a discharge lamp, 3 is a glow lamp, and 4 is a ballast. 5 is a phase control element composed of a thyristor, 6 is a phase control element 5
This is a dimming unit that outputs a dimming signal to a user, and is equipped with a triax 7, a trigger element 8 such as SBS, a resistor 9, a capacitor 10, a variable resistor 11, etc., and outputs a predetermined dimming signal by adjusting the variable resistor 11. occurs. Reference numeral 12 denotes a noise prevention circuit, which is composed of a capacitor 13 and an inductance 14. Reference numeral 15 denotes a current control element composed of a resistor.

According to the above configuration, the trigger element 8 and the triax 7 are sequentially turned on in accordance with the adjustment of the variable resistor 11, and the dimming section 6 generates a dimming signal every half cycle of the power supply voltage. The phase control element 5 is controlled on and off by this dimming signal, and the voltage whose phase is controlled by the phase control element 5 is supplied to the discharge lamp 2 via the ballast 4, whereby the discharge lamp 2 is dimmed and lit.
At this time, the current control element 15 serves to lower the re-ignition voltage of the discharge lamp 2 by continuing to supply some current to the discharge lamp even during the off-period of the phase control element 5, thereby increasing the peak point of the re-ignition voltage. This prevents the glow lamp 3 from operating or the discharge lamp 2 from going out due to this. Then, noise occurs when the phase control element 5 fires, and is strongest around the firing angle of 90 degrees.
This causes severe interference in the RF band, but this is suppressed by the noise prevention circuit 12.

[Problem that the invention attempts to solve]

However, in the case of the conventional circuit shown in FIG. 3, the current flowing through the current limiting element 15 in addition to the current flowing through the phase control element 5 flows through the inductance 14, so that the current I flowing through the inductance 14 as shown in FIG. _L became large, so the utilization rate of the inductance 14 was poor, and efficient noise prevention could not be achieved.

[Means for solving problems]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to increase the utilization rate of inductance of a noise prevention circuit and to achieve efficient noise prevention.

The technical means of the present invention to solve this technical problem is to provide a phase control element in series with the discharge lamp that controls the phase of AC power supplied to the discharge lamp using a dimming signal from a dimming unit, and to control the phase of the AC power supplied to the discharge lamp. In a discharge lamp dimmer circuit provided with a noise prevention circuit configured by an inductance connected in series to a control element and a capacitor connected in parallel to the inductance and the phase control element, the phase control element and a noise prevention circuit are provided. The point is that a current limiting element that allows a minute current to flow through the discharge lamp during the off period of the phase control element is connected in parallel to the series circuit with the inductance of the prevention circuit.

〔Example〕

Hereinafter, the present invention will be explained according to the illustrated embodiment. As shown in FIG. 1, a current limiting element 15 is connected in parallel to a series circuit of a phase control element 5 and an inductance 14 of a noise prevention circuit 12. .

Therefore, during the ON period of the phase control element 5, the current I _L flowing through the inductance 14 and the current limiting element 5
The current I _R flowing through the inductance 14 is supplied to the discharge lamp 2 via the ballast 4, and the current I _L flowing through the inductance 14 is reduced by the current I _R flowing through the current limiting element 15, so that the utilization rate of the inductance 14 is increased. , the terminal noise between terminals A and B can be reduced by about 10 dB compared to the conventional circuit (Fig. 3), and when the noise is kept at the same level, the capacitance of the capacitor 13 of the noise prevention circuit 12 can be reduced to 0.1 μF. It was possible to reduce the value to 0.01μF. Note that the current I _L flowing through the inductance 14 becomes zero during the off period of the phase control element 5, as shown in FIG. 3B, and is smaller than in the conventional circuit. Furthermore, since the current flowing through the inductance 14 is reduced, even if the inductance value of the inductance 14 is the same, the wire diameter of the inductance 14 can be reduced to make it compact.

[Effect of idea]

According to the present invention, a current limiting element that allows a small current to flow through the discharge lamp during the off period of the phase control element is connected in parallel to the series circuit of the phase control element and the inductance of the noise prevention circuit, so that the current flowing through the inductance is can be reduced by the amount of current flowing through the current limiting element, thus increasing the inductance utilization and effectively reducing noise.
Furthermore, the capacitance of the capacitor of the noise prevention circuit can be reduced while keeping the noise below a certain level.

Moreover, since the current flowing through the inductance can be reduced, the wire diameter of the inductance can be reduced to make it compact, and the structure can be simplified, manufactured easily, and provided at low cost, which has great practical effects.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
The figure is a current waveform diagram, and FIG. 3 is a circuit diagram showing a conventional example. 2... Discharge lamp, 5... Phase control element, 6... Light control unit, 12... Noise prevention circuit, 13... Capacitor, 14... Inductance, 15... Current limiting element.

Claims (1)

[Scope of utility model registration request] A phase control element for controlling the phase of AC power supplied to the discharge lamp by a dimming signal from a dimming unit is provided in series with the discharge lamp, and an inductance connected in series to the phase control element and an inductance and In a discharge lamp dimmer circuit provided with a noise prevention circuit constituted by a capacitor connected in parallel to the phase control element, the phase control element is connected to the series circuit of the phase control element and the inductance of the noise prevention circuit. A dimmer circuit for a discharge lamp, characterized in that a current limiting element that causes a minute current to flow through the discharge lamp during an off period is connected in parallel.