JPS60211799A - Device for firing discharge lamp - 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] 〔Technical field〕 The present invention relates to a discharge lamp lighting device.

[Background technology]

A conventional example is shown in FIGS. 1 and 2. In Figure 1,
C1 is a noise prevention capacitor connected between AC power supply terminals, R
e1 is a full-wave rectifier connected across the capacitor C1, CH, is an input choke connected across the full-wave rectifier Rel in series with the I-range inverter circuit IN, and OT is the output of the inverter circuit IN. LC is a discharge lamp circuit connected to the output side of the oscillation transformer OT, and ■ is a discharge lamp.

The inverter circuit IN has two transistors Q, Q2 that alternately turn on and off, both transistors Q,
, Q2 are connected together and a full-wave rectifier Re
It is connected to the negative terminal of No. 1.

The collector is connected to the collector via the resonant capacitor C2, and the collector winding Nl, which constitutes the primary winding of the oscillation transformer OT,
It is connected via N2. The base winding NB coupled to the oscillation transformer OT is connected to the bases of both transistors Q, , Q2, and the base of each transistor Q, , Q2 is connected to the starting resistor R3 via the base resistor R, , R2. The resistor R3 is connected to the positive terminal of the input choke CH.

Both ends of the heath drive winding N3 coupled to the oscillation transformer OT are connected to a full-wave rectifier Re2, and a 1% capacitor C3 is connected between both ends of the output of the full-wave rectifier Re2. The positive terminal of the smoothing capacitor C3 is connected to the connecting point of R1°R2, R3, and the negative terminal is connected to the emitter connecting point of both transistors Q, Q2.

N4 is the secondary winding of the oscillation transformer OT, N5. N5 is a preheating winding of the discharge lamp.

When the power is turned on, a full-wave rectified power supply voltage is applied between the collectors of transistors Q1 and Q2 through the input choke CH. At the same time, a base current is supplied from the power source to each of the transistors Q, Q2 through the input choke CH, resistors R3, R1, and R2. Due to an imbalance in the circuit, collector current begins to flow through one of the transistors.

Now, if a collector current begins to flow through the transistor Q1 on the collector winding Nl side, a voltage is induced in the base winding NB in the direction that the base current increases, and the collector current increases and reaches saturation. However, when the collector current becomes saturated, the voltage induced in the base winding disappears, the collector current begins to decrease, and the transistor Q1 becomes non-conductive and eventually becomes non-conductive.

On the other hand, the base current of the transistor Q2 on the collector winding N2 side increases from the time when the collector winding N+ (transistor Q according to the law) is saturated because the voltage induced in the Hass winding NB becomes forward biased. The collector current starts to increase, and the collector current also increases.A voltage is induced in the direction of forward bias in the plasma winding NB, and it reaches saturation all at once.When it is saturated, the collector current stops increasing, and the collector current increases. The voltage induced in the capacitor disappears, and the collector current begins to decrease and becomes non-conductive.

These return to the initial state, and thereafter oscillation continues by repeating this process.

Another winding (base drive winding) N3 is provided on the primary side of the oscillation transformer OT, and when the above oscillation continues, a voltage is induced across the winding N3, and each voltage is a full-wave rectified voltage. A current is supplied to the transistors Q, , Q2. Due to such oscillation, on the secondary side of the oscillation transformer OT,
A high high frequency voltage proportional to the turns ratio of the primary and secondary oscillation transformers is generated. Further, a voltage is also induced in the preheating winding N5 to preheat it, thereby lighting the discharge lamp.

The above operation lights up the discharge lamp, but the load becomes heavy at low temperatures, and the transistor Ql.

The current amplification factor hFE of Q2 decreases as shown in FIG.
There is insufficient base current for the transistor, which prevents normal oscillation and makes it difficult to turn on the light.

Therefore, conventionally, at room temperature, transistor Q1. Hose resistors R1, R2, so as to overdrive Q2.
The starting resistance R3 is set to a small value 1 to ensure normal oscillation even at low temperatures, but there is a drawback that there is a loss in base resistance and starting resistance at very high temperatures (and heat generation occurs).

[Purpose of the invention]

An object of the present invention is to provide a discharge lamp lighting device that reliably performs starting and lighting operations at low temperatures without increasing loss due to base resistance and starting resistance.

[Disclosure of the invention]

The discharge lamp lighting device of the present invention includes an inheritor circuit, a discharge lamp circuit connected to the output side of the inverter circuit, a variable impedance element inserted in the discharge lamp circuit, and a predetermined period of time after power is turned on. A timer circuit that outputs an output after the time has elapsed, and an impedance adjustment circuit that increases the impedance of the variable impedance element from a state lower than a predetermined impedance during lighting to the predetermined impedance in response to the output from the timer circuit. It is something that has been learned.

According to this configuration, the following effects occur. In other words, when the power is turned on at a low temperature, the impedance of the variable impedance element is lower than the predetermined impedance during lighting at the beginning of power-on, so the load on the switching elements such as transistors that make up the inverter circuit is reduced. Since the element operates as expected and the oscillation transformer oscillates normally, the discharge lamp can be reliably started and lit even at low temperatures. Then,
The impedance lla adjustment circuit is activated by the output from the timer circuit to increase the impedance of the variable impedance element to the predetermined impedance during lighting, and at this time the temperature of the discharge lamp is rising, so the normal lighting state is maintained. is retained.

A first embodiment of this invention will be described based on FIGS. 3 and 4. In the figure, +-0 is a variable impedance element constructed by connecting two choke coils Ll+'-2 in series, and a relay switch ry is connected in parallel to one choke coil L1. The above constitutes the impedance adjustment circuit IR. COM is a com terminal, NC is a normally closed contact, NO is a sealed contact, and the normally closed contact No is connected to the first contact a of the mote changeover switch Sw. The mode changeover switch Sw is connected in parallel to the variable impedance element LO.

Further, A is a timer circuit using a smoothing capacitor C3 as a power source, and includes a resistor R4 for determining the time limit 1, a content C4, a timer Ic, a transistor Q3 whose base is connected to the output terminal of the timer circuit, and this transistor Q3. It is equipped with a relay coil RY connected to the collector. Since the other IR configurations are the same as those of the conventional example (FIG. 1), the same parts are given the same reference numerals and the explanation will be omitted.

Next, the operation will be explained.

(1) When the power is turned on with the mote selector switch 3w connected to the first contact a, immediately after this, the state shown in Fig. 5 (A)
As shown in the figure, there is no output from the timer IC, and the transistor Q3 is off. Therefore, the race isotiri ry is in contact with the sealed contact NG, so the impedance of the variable impedance element Lo is the impedance of only one choke coil L2, and the light is turned on. The impedance is lower than the predetermined impedance inside. Therefore, reliable starting lighting is performed even at low temperatures. In other words, in order to improve the starting characteristics at low temperatures, base resistors R1 and R2 and starting resistor I3 are
There is no need to reduce the loss of base resistance at room temperature, and circuit design becomes easier.

After the time limit T has elapsed, there is an output from the timer IC and the transistor Q3 is turned on, so the relay coil RY is energized and the relay switch ry is switched to the normally closed contact NO side. That is, the discharge lamp circuit LC includes two choke coils Ll.
, I-2 are inserted, and the dimming lighting mode 1- is entered.

(II) When the mode changeover switch SW is connected to the second contact, both chokes: 1, L, and L2 are short-circuited, resulting in a light-load full lighting mode.

In this case, as shown in FIG. 5(B), the full lighting mode is maintained regardless of the presence or absence of the output from the timer IC. When the mode selector switch 3w is switched to the first contact a side from this state, both choke coils Ll.

Both L2 and L2 are inserted into the discharge lamp circuit LC to enter the dimming lighting mode.

As described above, in this embodiment, the dimming impedance is also used as the load reduction impedance which improves the starting performance, so the circuit is simplified accordingly.

The second embodiment will be explained based on FIGS. 5 to 7.

Variable impedance element Lo inserted in discharge lamp circuit LC
A saturable reactor is used. On the other hand, the timer circuit A includes a duty control circuit Du and a mode changeover switch Sw table that acts on the duty control circuit Du, in addition to resistors R4 and R5, content C4+O5, and a timer IC for determining the time limit ''. Hi, duty control 311 circuit 1) Transistor Q3 at the output terminal of IJ
Connect the hairs and flat? ? The positive terminal C of the capacitor C3 and the collector terminal d of the transistor Q3 are connected to both terminals 1 and dl of the control line of the saturable reactor +-o, respectively.

(I) When the mode selector switch SW is turned on, the duty control circuit Du operates for a time limit of 1 after the power is turned on.
During this period, a rectangular wave is output as shown in FIG. 6(C). When the average current value i1 flows through the saturable reactor L, the inductance of the saturable reactor Lo becomes L4 from the characteristics shown in FIG. This is the inductance L during a given lighting
Since the inductance is lower than that of Type 3, the load is lighter and reliable starting and lighting is performed even at low temperatures.

When the time limit T elapses, the output of the duty control circuit Du disappears as shown in Fig. 6 (B), and the saturable reactor +
Since no current flows through -o, the inductance of the saturable reactors I and 0 becomes the maximum L3, resulting in a dimming lighting mode.

(II) When the mode selector switch Sw is turned off, the duty control circuit 1) u outputs a constant current value jp as shown in Figure 6 (A), so the inductance of the saturable reactor LO is L5. It becomes a very small thing, and it becomes a virtually all-on mode.

This second embodiment also provides the same effects as the first embodiment.

〔Effect of the invention〕

According to the present invention, there is an effect that starting lighting operation can be performed reliably at low temperatures without increasing loss due to base resistance or starting resistance.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of the conventional example, Fig. 2 is a temperature-current amplification factor correlation graph, Fig. 3 is a circuit diagram of the first embodiment of the present invention, Fig. 4 is its time chart, and Fig. 5 is a circuit diagram of the second embodiment, FIG. 6 is an output waveform diagram of the duty control circuit, and FIG. 7 is a current-inductance correlation graph of the saturable reactor. I N...Inverter circuit, 0'F...Oscillation transformer, LC...Discharge lamp circuit, Lo...Choke coil (saturable reactor, variable impedance element), Δ...
Timer circuit, IR...Impedance adjustment circuit Figure 1 Figure 2

Claims (1)

[Scope of Claims] ill An inverter circuit, a discharge lamp circuit connected to the output side of the inverter circuit, a variable impedance element inserted in the fit circuit, and a predetermined period of time after power is turned on. A discharge lamp lighting device comprising: a timer circuit that outputs a later output; and an impedance adjustment circuit that increases the impedance of the variable impedance element from a state lower than a predetermined impedance during lighting to the predetermined impedance in response to the output from the timer circuit. Device. (2) The discharge lamp lighting device according to claim (1), wherein the impedance adjustment circuit is a relay circuit that switches the lower part of the variable impedance element between a short circuit state and an open state. (3) The variable impedance element is a saturable IJ actor, and the impedance adjustment circuit wall is a duty control circuit for outputting the timer circuit to the control line of the saturable reactor (ii). Discharge lamp lighting device.