JPS5878398A - Firing circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a discharge lamp lighting device.

Figure 1 shows the basic circuit of a low-voltage lighting ballast with a dimming function. A detailed explanation of the operation will be omitted since it has already been explained in a previous application, but by opening and closing the changeover switch 22, switching between full light and dimming is performed. That is, during full light, the changeover switch 22 is opened, the gate potential of the N-gate thyristor 17 is set to the ground potential, and the N-gate thyristor i 1 is set to the ground potential.
7' conductive sash, resistors 15a, 15b, 16a,'
J variable low resistor 16b15a11 (16a-1-16b)
With the combined resistance value determined by 1115b, switch circuit 1
The phase at which the repair cycle is cut off, that is, the manner in which the lamp 6 is output is determined.

Actually, during dimming, when the selector switch 22 is closed, a constant is set so that the gate potential of the N-gate thyristor 17 is held higher than the γ node potential, and the N-gate thyristor 17 becomes non-conductive. Tebru. In other words, the combined resistance value on the emitter side of the transistor 10 is i5a〆(16a+
16b) is larger than that of IYJ, the cutoff phase of the switch circuit 1 is advanced, and the output of the lamp 6 is lower than that at full light.

As mentioned above, in the case of dimming, the combined resistance value is 15a/(1
Although it is possible to arbitrarily select the degree of dimming by appropriately selecting 6a+16b), the lamp 6 may go out due to voltage fluctuations of the commercial AC power source 4. Therefore, the degree of dimming is limited by voltage fluctuations of the commercial AC power supply 4.

As mentioned above, the degree of dimming is limited by voltage fluctuations in the power supply.

An object of the present invention is to increase the degree of dimming.

Therefore, the present invention varies the a#r phase of the switch circuit in accordance with voltage fluctuations of the power supply, so that the output of the lamp does not change significantly due to voltage fluctuations, and is used not only during dimming but also during full brightness. This is also due to the power supply voltage compensation circuit being activated.

In the circuit configuration, an N-gate thyristor 27 is connected in place of the switch element 11 that determines the cut-off phase in FIG. A parallel circuit of element 24 and resistor 33 was connected in series to the negative potential of full-wave rectifier 7, and was also connected to the connection point of resistors 13 and 14 from the connection point of diode 32 and capacitor 24 via resistor 25. It is something.

The operation is as follows. In FIG. 1, the cutoff phase of the switch circuit is determined by the emitter potential of the transistor 10, and hardly changes with voltage fluctuations of the commercial AC power supply 4. This is because there is almost no difference in the slope of the voltage rise due to voltage fluctuations of the commercial AC power supply 4 when the power supply voltage is in the range of 90 to 110V, so the switch elements 11 conduct almost in the same phase. be.

However, in FIG. 2, the potential of the capacitor 24 becomes Toff as the emitter potential of the transistor 810 increases.
Emitter potential of transistor 10, that is, capacitor 2
When the voltage difference between 3 and 24 reaches the breakover voltage VBOK of the switch element 11, the switch element 11 becomes conductive.
At the same time, the N-gate thyristor 27 becomes conductive, cutting off the switch circuit 1. Therefore, if the voltage difference VBO between the capacitors 23 and 24 is changed by the voltage fluctuation of the commercial AC power supply 4, the cutoff phase of the switch circuit 1 will be changed.

For example, when the voltage of the commercial AC power supply 4 is high, the rising slope of the power supply voltage becomes steep, and the potential of the capacitor 23 also rises sharply. Incidentally, the potential of the capacitor 24 gradually increases from the potential of (voltage of the capacitor 26 + Vcθ + Vgk) via the resistor 25, but as described above, when the power supply voltage increases, the potential of the capacitor 23 increases. Because of this, the phase that reaches the differential voltage Vbo is earlier, and the phase that reaches the differential voltage Vbo is earlier, as shown by curve A in FIG. 3, at time 1. becomes.

Next, when the voltage of the commercial AC power supply 4 is lowered, the rising slope of the power supply voltage becomes gentler than before, and the rise in the potential of the capacitor 26 also becomes gentler. For this reason, the capacitor 24
The potential of gradually increases and reaches the differential voltage Vbo at phase t,
is 1. slower.

It works in the direction of increasing the output of the lamp 6.

Figure 4 compares the voltage fluctuation characteristics during full light and dimming between Figure 1 (solid line) and the circuit system of Figure 2 (broken line) of the present invention.
Show the situation.

According to the present invention, it is possible to increase the degree of dimming without being affected much by fluctuations in power supply voltage.

FIG. 4 is a comparison diagram of voltage fluctuation characteristics between the circuit system of the present invention and the conventional circuit system.

1 is a switch circuit, 2 is a preheating circuit, 3 is a choke%4 is a commercial AC power supply, 5, 20, 25, 24゜26 is a capacitor, 6 is a lamp, 7 is a full wave rectifier, 8.9 is a thyristor, 10 is Transistor, 11 is a switch element, i2~
14, 15a, 15b.

16a, 19, 21.25.55 are resistors, 17°27
is N-gate thyristor, 1 B', 28~! 12 is a diode, 22 is a changeover switch.

Claims (1)

[Claims] A choke and a lamp are connected in series through a power supply, and a preheating circuit and a switch circuit that opens and closes at a fixed period after the end of discharge of each half cycle of the lamp are connected in parallel with the lamp through a full-wave rectifier. A lighting circuit characterized in that a lamp lighting device is equipped with a compensation circuit that varies the switching phase of a switch circuit according to a power supply voltage.