JPH067515B2 - Discharge lamp power supply - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp power supply device for pulse-lighting a xenon discharge lamp or the like, and in particular, always supplies a constant power even when the input voltage varies. The present invention relates to a discharge lamp power supply device capable of performing the above.

[Prior Art] FIG. 10 is a circuit diagram of a conventional discharge lamp power supply device for pulse-lighting a xenon discharge lamp. In FIG.
Reference numeral 51 is an AC power supply, 52 is a leakage transformer, 53 is a charge / discharge capacitor, 54 is a supersaturation reactor, 55 is a lamp starting circuit, and L is a xenon discharge lamp.

According to the above circuit configuration, the leakage voltage transformer 52, the capacitor 53, and the supersaturation reactor 54 form the AC voltage of the AC power source 51 into a pulse waveform, which allows the xenon type and the discharge lamp L to generate the pulse of the waveform shown in FIG. A current (discharge current = Il) can be passed.

It is generally known that when a pulse current is passed through the xenon discharge lamp L, a light amount that is 2 to 3 times the normal luminous efficiency can be obtained.

However, in the discharge lamp power supply device having the circuit configuration as described above, since the supersaturated reactor 54 is arranged, the device becomes large and heavy, and moreover, it is expensive and, moreover, has no constant power property. Therefore, such devices are not popular in industry.

FIG. 12 is a circuit diagram of a conventional discharge lamp power supply device using a bidirectional switching element (hereinafter referred to as a triac) instead of the supersaturated reactor. 12, 51 to 53 and L are the same as those in FIG. 10, 56 is a triac, 57 is a comparison pulse generation circuit (PC),
Reference numeral 58 is a current detector for detecting the current of the xenon discharge lamp L, 59 is a pulse transformer, 60 is a discharge lamp starting circuit, and 61 is a bypass resistor. Further, the resistor 62 and the capacitor 63 are an RC snubber circuit for protecting the triac from an overvoltage when the triac is turned off.

According to the above circuit configuration, the current detector 58 of the xenon discharge lamp L detects the discharge current of the xenon discharge lamp L, and the comparison pulse generation circuit 57 is based on the result.
Controls the phase of the trigger pulse sent to the gate of the triac 56, and adjusts the time when the triac 56 becomes conductive. That is, when the discharge current of the xenon discharge lamp L is large, the conduction time of the triac 56 is shortened, and conversely, when the discharge current is small, the trigger pulse to be sent to the triac 56 is extended so that the conduction time of the triac 56 is lengthened. By controlling the phase, constant power is supplied to the xenon discharge lamp L. Further, while the triac 56 is in the non-conducting state, electric power is supplied via the bypass resistor 61 so that the xenon discharge lamp L does not go out. In this way, a pulse current having a waveform similar to the pulse waveform shown in FIG. 11 is supplied to the xenon discharge lamp L. According to the circuit configuration described above, since the supersaturated reactor is not used, it is possible to reduce the size and weight of the device.

[Problems to be solved by the invention]

However, in such a conventional discharge lamp power supply device, since the lamp power supplied to the xenon discharge lamp L is the product of the lamp voltage and the lamp current, if the lamp current is controlled to be a constant current as described above, In the unlikely event that the lamp voltage rises, there is a drawback that the input becomes excessive. For example, in a discharge lamp such as a xenon discharge lamp, the lamp voltage generally rises at the end of its life. Therefore, if the lamp current is controlled so as to be constant as in the conventional discharge lamp power supply device, at the end of the life of the discharge lamp, the lamp power increases and the temperature of the discharge lamp rises. Since the voltage rises, and as a result, the lamp power further increases, the lamp power increases due to the increase in the lamp voltage,
Due to this, the phenomenon that the lamp voltage rises again is repeated, and eventually the xenon discharge lamp L becomes extremely over-input, and an accident such as destruction of the xenon discharge lamp L occurs.

The present invention has been made based on the above circumstances. Even when the lamp voltage rises, over-input is prevented, and even if the input voltage fluctuates, a constant power is constantly supplied to the discharge lamp. It is an object of the present invention to provide a discharge lamp power supply device capable of supplying

[Means for solving problems]

The present invention for achieving the above object is an alternating current, a charging / discharging capacitor connected to the alternating current power supply via a current limiting impedance element, a discharge lamp as a load, the alternating current power supply and the charging / discharging capacitor. Power supply to the discharge lamp via a starting means for starting the discharge lamp, a detection means for detecting an input voltage, and the bidirectionality based on an output signal of the detection means. A phase control circuit for controlling the phase of a trigger pulse applied to the gate of the switching element, and a bypass circuit for supplying electric power to the discharge lamp when the bidirectional switching element is in a non-conducting state. .

[Action]

With the above-described structure, the present invention detects the input voltage supplied to the discharge lamp, and when the input voltage fluctuates, adjusts the phase of the trigger pulse applied to the gate of the bidirectional switching element, thereby releasing the discharge pulse. Even if the input voltage fluctuates, constant electric power can be supplied to the electric lamp. Moreover, since the input voltage is detected and a constant electric power is supplied to the electric lamp, the end of the discharge lamp life is reached. Thus, when the discharge lamp voltage rises, the discharge lamp power can be reduced.

〔Example〕

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 6. FIG. 1 is a circuit diagram of a discharge lamp power supply device according to a first embodiment of the present invention. In FIG. 1, 1 is an AC power supply, 2 is a reactor, 3 is a charge / discharge capacitor, 4 is a pulse transformer for starting a discharge lamp, 5 is a lamp starting circuit (PG), 6 is a triac, and 7 is a bypass. A resistor, 8a is a resistor for the RC snubber circuit, 8b is a capacitor for the RC snubber circuit, 9 is a comparison pulse generation circuit (PC), 10 is an input voltage detection circuit (VD), 11
Is an input switch, 12 is a delay relay (TD), 12a
Is a contact of the delay relay 12 and L is a discharge lamp.

Next, the operation of the circuit configured as described above will be described. First, when the input switch 11 is turned on, a pulse voltage is generated by the pulse transformer 4 and the starting circuit 5.
However, since the triac 6 is still in a non-conducting state, no current flows through the discharge lamp L, and a charging current flows through the charge / discharge capacitor 3 during a half cycle until the discharge lamp L is lit. Next, when the triac 6 is turned on by the trigger current from the comparison pulse generation circuit 9, the combined current of the current flowing from the AC current 1 through the reactor 2 and the discharge current of the charging / discharging capacitor 3 produces a discharge lamp L. Flow to. The discharge current of the charging / discharging capacitor 3 causes a peak value of the luminous flux. Eventually, when the voltage of the AC power supply 1 is inverted and the triac 6 becomes non-conductive, the triac 6 is discharged by the trigger current from the comparison pulse generating circuit 9 in the next half cycle until it becomes conductive again. Since the lamp L has already started,
A bypass current flows through the discharge lamp L via a bypass resistor 7 connected in parallel with the triac 6. This is to prevent the discharge lamp L from cooling and increasing the re-ignition voltage, and then extinguishing. After a certain period of time, the discharge of the discharge lamp L becomes stable, and the pulse transformer 4
Since the pulse voltage due to is unnecessary, the delay relay 12 operates, its contact 12a is opened, and the generation of the pulse voltage is stopped. After the generation of the pulse voltage is stopped, a trigger current is sent to the triac 6 every half cycle to bring it into a conducting state, whereby a discharge current similar to the waveform shown in FIG. 11 can be obtained.

By the way, as for the phase angle Φ of the trigger current given to the triac 6, when Φ is large, the power supplied to the discharge lamp L is small, and conversely, when Φ is small, the discharge lamp L is small.
The power supplied to Now, assume that the phase angle of the trigger current when the input voltage is normal (V ₂₀₀ ) is, for example, Φ ₁ , as shown in FIG. When the input voltage rises as indicated by the solid line (V ₂₂₀ ) in FIG. 2 for some reason, the input voltage detection circuit 10 detects this and sends a signal to the comparison pulse generation circuit 9. Upon receiving this signal, the comparison pulse generation circuit 9 sends to the triac 6 a trigger pulse having a trigger phase angle of Φ ₂ larger than Φ ₁ under normal conditions. This can prevent an increase in the power consumption of the discharge lamp L due to an increase in the input voltage. On the contrary, when the input voltage drops as indicated by the dotted line (V ₁₈₀ ) in FIG. 2 for some reason, the input voltage detection circuit 10 detects this and sends a signal to the comparison pulse generation circuit 9. Upon receiving this signal, the comparison pulse generation circuit 9 sends to the triac 6 a trigger pulse having a trigger phase angle of Φ ₃ which is smaller than Φ ₁ under normal conditions. As a result, it is possible to prevent the input voltage from dropping and the power consumption of the discharge lamp L to drop.

As described above, according to the embodiment having the above configuration,
Like the conventional device shown in the figure, it detects the discharge current of the discharge lamp and controls the phase angle of the trigger pulse applied to the triac so that the discharge current becomes a constant value. In contrast to supplying the discharge lamp, the input voltage to the discharge lamp is detected and the phase angle of the trigger pulse applied to the TRIAC is controlled, which supplies constant power to the discharge lamp. You can suppress the rise of.

That is, in the conventional discharge lamp power supply device shown in FIG. 12, in order for the electric power supplied to the discharge lamp to be constant power, it is premised that the lamp voltage is constant. Therefore, the conventional device has a drawback that the lamp power also increases in proportion to the lamp voltage, as shown by the straight line (a) in FIG. 3, when the lamp voltage increases. On the other hand, in the discharge lamp power supply device of the present embodiment, when the lamp voltage on the discharge lamp side increases, the lamp current decreases, and when the lamp voltage decreases,
The lamp current increases, it is basically reactor control,
Moreover, it is an open loop feedback circuit that follows only the fluctuation of the input voltage. Therefore, when the input voltage is used as a parameter, the relationship between the lamp voltage and the lamp power is as shown by the curves (b), (c), and (d) in FIG. It can be seen that

Next, the above will be described using mathematical expressions. In the conventional discharge lamp power supply device shown in FIG. 12, the lamp voltage Vl is constant, and since it is a closed loop feedback circuit, the lamp current Il is also constant. Therefore, the lamp electric journey W
When the power factor is cos θl, l becomes Wl = Vl × Il cos θl. Therefore, when the lamp voltage Vl changes by ΔVl,
In proportion to this, the lamp power Wl also changes by the ratio of ΔVl and becomes a straight line as shown in FIG.

On the other hand, in the device of this embodiment, the reactor is basically lit on the lamp side. Therefore, if the circuit shown in FIG. 1 is simplified, it can be considered to be equivalent to the circuit shown by the solid line in FIG. it can. Therefore, the curves of the lamp voltage and the lamp current of the device of this embodiment are substantially quadratic curves as shown in FIG.
When the lamp is in a short circuit state, a short circuit current Is flows, and when the lamp is in an open state, a no-load voltage V ₁ equal to the input voltage is generated between the terminals of the lamp. Also, the rating is V
Stability in terms of e and Ie. This is easily obtained by experiment. Therefore, the lamp current is Il = −αVl ² + Is (α: constant), and the lamp power is Wl = Il · Vl as described above.
Since it is cos θ, the lamp power is Wl = (− αVl ³ + IsVl) cos θ, and the relationship between the lamp voltage Vl and the lamp power Wl is 3
It becomes the next curve. That is, the relationship between the lamp voltage Vl and the lamp power Wl is approximate to the cubic curve shown by the solid line in FIG. Here, in the circuit of the device of this embodiment, since the charging / discharging capacitor is actually inserted in parallel with the lamp,
Given the state of charging and discharging the capacitor C ₀ is connected to the circuit shown in FIG, at low lamp voltages, the resonance voltage V ₂ of the reactor 2 ₀ and charging and discharging capacitor C _0,
Since the discharge current of the charging / discharging capacitor C ₀ and the base current from the input side flow more than the rated current, the lamp power increases, and conversely, the higher lamp voltage decreases. Therefore, the cubic curve showing the relationship between the lamp voltage and the lamp power is, to be exact, the maximum current at a low lamp voltage as shown by the chain line in FIG.

As a result of the experiment, when the charging / discharging capacitor C ₀ is not provided, the value of the lamp voltage at which the lamp power reaches the maximum value is 5 of the no-load voltage
It will be about 5%. In contrast, when there is a charging and discharging capacitor C ₀ is at about 15% of the resonance voltage of the reactor 2 ₀ and charging and discharging the capacitor C ₀ is the maximum power. Therefore, if the device of the present embodiment is used for a xenon discharge lamp or the like having a low lamp rated voltage and a high starting voltage, the maximum power is obtained at a low lamp voltage and the lamp voltage becomes high even if the no-load voltage is high. As a result, the lamp power decreases, so that even if the lamp voltage rises at the end of the life of the lamp, overpower does not occur. Further, since the open loop feedback circuit that detects the fluctuation of the input voltage and maintains the constant power characteristic is provided, the stable constant power performance can be maintained without being affected by the instability of the discharge of the lamp.

As described above, the device of this embodiment is different from the closed loop feedback system in which the discharge current of the discharge lamp is detected and the constant power is detected, and the open loop feedback system in which the input voltage to the discharge lamp is detected and the constant power is detected. Therefore, unlike the closed loop feedback method, no malfunction occurs due to the instability of the lamp discharge, and in addition to the open loop feedback method, the resonance voltage between the charge / discharge capacitor and the reactor allows the lamp to operate at low lamp voltage. Since the lamp power is maximized, it is possible to prevent overpower even if the lamp voltage rises at the end of the life of the lamp. Further, since the apparatus of this embodiment can illuminate the lamp with the effective pulse current by the phase control of the bidirectional switching element, it has a great industrial effect as a power source for photolithography and copying. .

FIG. 7 is a circuit diagram of a discharge lamp power supply device according to a second embodiment of the present invention. The second embodiment is different from the first embodiment in that the bypass resistor 7 includes a reactor 2 and a triac 6
It is connected to both ends in parallel. The operation and effect of the second embodiment are similar to those of the first embodiment.

FIG. 8 is a circuit diagram of a discharge lamp power supply device according to a third embodiment of the present invention. The third embodiment differs from the first embodiment in that a step-up transformer T is arranged on the primary side. Third
According to this embodiment, it is possible to reliably control the lighting of a discharge lamp having particularly bad startability or a discharge lamp having a relatively high rated voltage. Other functions and effects are similar to those of the first embodiment.

FIG. 9 is a circuit diagram of a discharge lamp power supply device according to a fourth embodiment of the present invention. The fourth embodiment differs from the first embodiment in that a leakage transformer Tl is used instead of the booster transformer and choke on the primary side. The operation / effect of the fourth embodiment is similar to that of the third embodiment.

In the above embodiment, the case where the resistor is used in the bypass circuit has been described, but the present invention is not limited to this, and it may be an impedance or a reactor.

〔The invention's effect〕

As described above, according to the present invention, the input voltage is detected, and the bidirectional switching element is controlled according to the variation, so that even if the input voltage varies, the output voltage is always constant with respect to the discharge lamp. In addition to being able to supply the electric power of the above, it is possible to supply the discharge lamp power supply device in which the discharge lamp does not become an excessive input even when the discharge lamp voltage rises.

[Brief description of drawings]

1 is a circuit diagram of a discharge lamp power supply device according to a first embodiment of the present invention, FIG. 2 is a diagram showing an input voltage waveform of a discharge lamp,
3 is a diagram showing the relationship between the lamp voltage (Vl) and the lamp power (Wl), FIG. 4 is a simplified circuit diagram of the circuit of FIG. 1, and FIG. 5 is a lamp voltage (Vl) and a lamp current. (Il)
FIG. 6 is a diagram showing the relationship between the lamp voltage (Vl) and the lamp power (Wl), FIG. 7 is a circuit diagram showing the second embodiment, and FIG. 8 is a third diagram. Circuit diagram showing an embodiment,
FIG. 9 is a circuit diagram showing a fourth embodiment, FIG. 10 and FIG.
FIG. 11 is a circuit diagram of a conventional discharge lamp power supply device, and FIG. 11 is a diagram showing a discharge current waveform of a discharge lamp in the conventional discharge lamp power supply device shown in FIG. DESCRIPTION OF SYMBOLS 1 ... AC power supply, 2 ... Reactor, 3 ... Charging / discharging capacitor, 4 ... Pulse transformer, 5 ... Starting circuit, 6 ... Triac, 7 ... Bypass resistor, 8a ... Resistor, 8b ... Capacitor, 9 ... Comparison pulse generating circuit, 10 ... Input voltage detection circuit, 11 ... Input switch, 12 ... Delay relay, L ... Discharge lamp.

Claims (3)

[Claims] 1. An AC power supply, and a charge / discharge capacitor connected to the AC power supply via a current limiting impedance element,
A discharge lamp that is a load, a bidirectional switching element that supplies the AC power supply and the power of the charging / discharging capacitor to the discharge lamp via a starting means that starts the discharge lamp, and a detection means that detects an input voltage. And a phase control circuit for controlling the phase of the trigger pulse applied to the gate of the bidirectional switching element based on the output signal of the detection means,
A discharge lamp power supply device, comprising: a bypass circuit that supplies power to the discharge lamp when the bidirectional switching element is in a non-conductive state. 2. The starting means comprises a starting pulse transformer, a starting circuit, and a delay relay that cuts off the supply of power to the starting circuit after a lapse of a certain time from the start of energization of the discharge lamp. The discharge lamp power supply device according to claim 1, wherein 3. The bypass circuit, which is composed of a resistor and is configured to pass a current smaller than a main current flowing through the discharge lamp to the discharge lamp when the bidirectional switching element is non-conductive, The discharge lamp power supply device according to claim 1 or 2, wherein the discharge lamp power supply device is connected in parallel to the directional switching element.