JPS6233719B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Field to which the invention pertains and purpose of the present application A DC discharge lamp used for lighting a DC discharge lamp, such as a xenon short arc discharge lamp, an ultra-high pressure mercury lamp, or a mixed metal vapor discharge lamp. The main purpose of this lighting device is to reduce the size and weight of conventional DC discharge lamp lighting devices. The second purpose is to create a structure in which the transistor included in the inverter section does not stop transmitting even if there is a large inrush current at the initial stage of lighting the DC discharge lamp, so that the failure of the DC discharge lamp not to turn on occurs. An object of the present invention is to provide a lighting device for a DC discharge lamp.

(2) Prior art and its drawbacks (2.1) A lighting device for a conventional DC discharge lamp, such as a xenon short arc discharge lamp, uses a power transformer connected to an AC power source,
Next, a rectifier and a smoothing circuit are connected in sequence, and to this basic circuit, a current stabilizer, a voltage stabilizer, and a power stabilizer are added. It is used with some improvements, such as the addition of a superimposed voltage generation circuit.

These are generally large in size and heavy;
When the above-mentioned DC discharge lamp is used industrially, a large and heavy "ballast" or "lighting device" is always attached as a separate device.
This accessory is very difficult to handle, which is also a cause of hindering the expansion of the uses of DC discharge lamps.

In the present invention, in order to eliminate this conventional drawback, the structure of the lighting device for a DC discharge lamp is fundamentally changed, and an attempt is made to reduce the size and weight of the lighting device.

Fortunately, computer equipment, etc.
An inverter system is used to control DC loads, and it is known that the circuit configuration of this inverter system is extremely compact and lightweight.
The present invention focuses on this fact and attempts to introduce an inverter system as a lighting device for DC discharge lamps, but unfortunately, after conducting various experiments, due to the significant difference in the characteristics of the loads, It was discovered that the circuit configuration used in computer equipment could not be used.

(2.2) Example of a lighting device for a DC discharge lamp for a xenon short arc discharge lamp that uses an inverter system, which is used in computer equipment, etc. As shown in Figure 1, a DC device is connected to the AC power source 0. The positive side of the DC device 1 is connected to the center tap of the transformer _T1 of the inverter section 2, the negative side is connected to the common emitter of the transistors _S1 and _S2 , and the positive side of the DC device 1 is connected to the center tap of the transformer T1 of the inverter section ₂ . One end of both ends is connected to the collector of the transistor _S1 , and the other end is connected to the collector of the transistor _S2 .

A rectifier 3 and a smoothing circuit 4 are connected to the inverter section 2, the positive output of which is connected to the positive side of the discharge lamp 6 via the starter 5, and the negative output of which is connected to the positive side of the discharge lamp 6 via the current detection element 7. Connect to the negative side of the electric light 6.

The superimposed voltage generating circuit 8 takes its input from the inverter section 2, its positive output side is connected to the positive output side of the smoothing circuit 4, and its negative output side is connected to the negative output side of the smoothing circuit 4.

Here, the inverter section 2, rectifier 3, smoothing circuit 4, current detection element 7, and superimposed voltage generation circuit 8 will be collectively referred to as a main circuit.

One end of the input of the error amplifier 9 is connected to the current detection element 7, the other end is connected to the reference power supply 10, and the output side of the error amplifier 9 is connected to a pulse width control circuit 11 and a drive circuit 12 in sequence. It is connected to the bases of the transistors S ₁ and S ₂ of the inverter section 2.

The auxiliary power supply 13 includes an error amplifier 9, a pulse width control circuit 11, a drive circuit 12,
This is for supplying a predetermined power to the reference power source 10.

(2.3) Its basic operation When AC power supply 0 is applied, first, the auxiliary power supply 13 is activated, and a predetermined power is supplied to the error amplifier 9, pulse width control circuit 11, drive circuit 12, and reference power supply 10. Ru.

As a result, the oscillator OSC of the pulse width control circuit 11 oscillates and outputs a rectangular pulse. This rectangular pulse is converted into a triangular wave V _R of a constant shape by a triangular wave generator RAMP. This triangular wave V _R is a comparator
It is compared with the output of the error amplifier 9 by COM, and pulse width modulation is performed.

In pulse width modulation, when the output voltage of the error amplifier is larger than the voltage of the triangular wave V _R , the output of the comparator COM will deviate from the modulation, and the output of the comparator COM will be "LOW level." Conversely, when the output voltage of the error amplifier is smaller than the voltage of the triangular wave V
The output of COM is "HIGH level".

AND gate A ₃ is the comparator mentioned above
The AND signal of the output of COM and the oscillation signal of the oscillator OSC is output, and if the output of the comparator COM is "LOW level", the output stops and the output signal of the comparator COM becomes "HIGH level".
In the case of "Level", it becomes a pulse width signal similar to the oscillation signal of the oscillator OSC.

The output of the AND gate _A3 enters the input side T of the flip-flop F/F, and is alternately distributed to Q and output. This output Q,
is input to AND gates A ₁ and A ₂ along with the output of AND gate A ₃ , and the dead period adjustment circuit Dead
The logical product of these signals including the pause signal is taken, and the transistors S _{3 and} S 3 of the drive circuit 12 are
transmitted to S ₄ .

The dead period adjustment circuit Dead is provided for the purpose of preventing the simultaneous conduction state of the transistors S ₁ and S ₂ of the inverter section 2, which is caused by the extension of the conduction time (storage time) due to the charges accumulated in the bases of the transistors S 1 and S 2 .

The drive circuit 12 includes transistors S ₃ and S ₄
The conduction/non-conduction signal is transmitted to the transistors S ₁ and S ₂ of the inverter section 2 while maintaining insulation from the AC power source 0 side, and is designed to have low impedance.

Through the above process, the transistors S ₁ and S ₂ of the inverter section 2 become conductive and non-conductive alternately, and a square wave alternating current is generated on the secondary side of the transformer T ₁ and is discharged through the rectifier 3 and the smoothing circuit 4. Electric power is supplied to the electric light 6.

The superimposed voltage generating circuit 8 is provided to shorten the time required for stable lighting of the discharge lamp, and the starter 5 is provided for breakdown of the discharge lamp.

(2.4) Stable lighting state of discharge lamp As shown in an example in FIG. ₁₂ and R ₁₃ to create the inverted input signal Ve of the operational amplifier E.A, and on the other hand, the voltage dividing resistor
A non-inverting input signal V of the operational amplifier E.A is created by R ₁₀ and R ₁₁ . This inverted input signal
_{The error voltage (V-Ve) of Ve and the non-inverting input signal V is multiplied by R 7 /R 8 in the operational} amplifier E.A. Output from A.

This output signal [(V-Ve)R ₇ /R ₈ ]+V
When the discharge lamp current I _L that actually flows increases based on the rated current Is of the discharge lamp, the signal Va from the current detection element 7 increases to the negative side, and therefore the inverted input signal Ve decreases,
This therefore increases. Discharge lamp current I _L
If it decreases, it will decrease, which is the opposite of the above case.

This output signal [(V-Ve)R ₇ /R ₈ ]+V
ultimately becomes the output Vb of the error amplifier 9 and is transmitted to the comparator COM of the pulse width control circuit 11. If Vb is constant, that is, if there is no fluctuation in the discharge lamp current I _L , the pulse width output from the comparator COM will be constant, which means that the discharge lamp is in a stable steady state of lighting. If, Vb
When Vb increases, the pulse width decreases, and when Vb decreases, the pulse width increases.Then, the pulse width control circuit 11, via the drive circuit 12,
The transistors S ₁ and S ₂ of the inverter section 2 are controlled, and ultimately the discharge lamp current I _L is controlled to increase or decrease in order to maintain a stable lighting state of the discharge lamp.

(2.5) Transient state at the beginning of discharge lamp lighting Figure 4 is an explanatory diagram of the waveforms of various parts at the beginning of discharge lamp lighting, where (a) is the waveform of the discharge lamp current I L and rated current Is, and (b) is the waveform of the discharge lamp current I _L and rated current Is. The signal waveforms of Ve and V, (c) the waveforms of Vb and V _R , (d) the output signal waveform of AND gate _A3 , and (e) the waveform of the voltage V _L appearing at both ends of the discharge lamp and the rated voltage Vs, respectively. show. The horizontal axis of the graph is a common time axis.

At the initial stage of lighting the discharge lamp when the starter 5 is operated and the discharge lamp 6 is broken down, the voltage V _L appearing at both ends of the discharge lamp is as shown in (e), and the initial value is the capacitor C ₁ of the smoothing circuit 4.
A superimposed voltage Vh appears and rapidly decreases with rapid discharge of charge. As a result, a large initial rush current flows as shown in (a). This period is defined as _t1 .

This initial rush current is detected as a signal Va from the current detection element 7, and the error amplifier 9
, it is converted into an inverted input signal Ve.
At this time, within time _t1 , as shown in (b), a state of Ve≪V occurs, and in comparing the input signal Vb of the comparator COM of the pulse width control circuit 11 with _VR , (c) As shown, Vb>V _R , and as described above, the output of the comparator COM is "LOW level", and therefore, as shown in (d), the output of the AND gate _A3 is also "LOW". Therefore, the flip-flop F/F is in a stopped state, and the drive circuit 1
The transistors S ₁ and S ₂ of the inverter section 2 controlled through the inverter section 2 are both non-conductive, and at a time t ₂ following the time t ₁ , the discharge lamp current I _L is lower than the rated current Is. I feel depressed.

Due to the drop in current at time _t2 , when I _L ≦Is, exactly at the above-mentioned time _t1
Contrary to the case of I _L ≧Is in (b),
Ve>V, (c) Vb<V _R , and as described above, the output of the AND gate _A3 becomes a pulse width signal similar to the oscillation signal of the oscillator OSC (d). Therefore, through the pulse width control circuit 11 and the drive circuit 12, the transistors S ₁ and S ₂ of the inverter 2 are alternately rendered conductive.
Charge is stored in the capacitor C ₁ of the smoothing circuit 4, but due to the time delay caused by the inductance L ₁ of the smoothing circuit 4 and the capacitor C ₁ , the discharge lamp current I _L and the voltage V _L across the discharge lamp are During this period, the DC discharge lamp is likely to turn off without quickly recovering.

In other words, when the main circuit includes an inverter section and a superimposed voltage generation circuit, the non-conducting state of the transistors in the inverter section due to the initial large inrush current, and the relationship between this and the time delay of the smoothing circuit, cause the DC discharge lamp to This has the disadvantage of causing accidents such as non-lighting.

(3) Structure of the present invention and its effects FIG. A transistor S7 for grounding between the resistors _R10 and _R11 , a capacitor _{C2 and} a resistor _R18 for time-controlling the base voltage of the transistor _S7 , and a discharging transistor connected to both ends of the capacitor _C2 . S ₆ , and a receiving section 15 including a Zener diode ZD ₂ that controls the base voltage of this transistor S ₆ , and detects a voltage signal V _L applied to both ends of the discharge lamp taken out from the positive output of the smoothing circuit 4 of the main circuit. Then, the discharging transistor _S6 is brought into conduction according to the magnitude relationship between the partial voltage Vg by the resistors _R14 and _R15 and the predetermined Zener voltage of the Zener diode _ZD2 . ₂ and the resistor _R18 , the grounding of the transistor _S7 can be canceled with a time delay due to a time constant determined by the resistor R18.

Note that +E indicates that the auxiliary power source 13 is used as a driving power source.

That is, by designing the Zener voltage and the time constant determined by C ₂ and R ₁₈ to predetermined values, the non-inverting input signal V can be set to 0 during a certain time period tx. That is, to explain using FIG. 5, in the input signal of the operational amplifier E.A, in a certain time period tx as shown in (b), V
<Ve, and for the reason explained in detail above, the transistors S ₁ and S ₂ of the inverter section 2 operate, that is, they can be prevented from being inoperable.

Here, the fixed time period tx is as follows:
It is sufficient to make it approximately equal to the time period t ₁ during which the initial inrush current flows.

Therefore, the transistor of inverter 2
Since the inoperable state of S ₁ and S ₂ can be resolved in a timely manner, (e)
As shown in (a), it is possible to prevent the voltage applied to both ends of the discharge lamp and the discharge lamp current from dropping significantly below the rated value, and the occurrence of non-lighting accidents can be reliably prevented. In order to significantly reduce the size and weight of a lighting device for a discharge lamp, a lighting device with good performance can be provided even if an inverter method is used.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an embodiment of a lighting device using an inverter method for a DC discharge lamp lighting device, Fig. 2 is an explanatory diagram of the error amplifier 9, Fig. 3 is an explanatory diagram of the control section, and Fig. 4 1 is an explanatory diagram of waveforms of each part in the apparatus of FIG. 1, and FIG. 5 is an explanatory diagram of waveforms of each part of the apparatus of the present invention. In the figure, 1 is a DC device, 2 is an inverter section, 3 is a rectifier, 4 is a smoothing circuit, 5 is a starter, 6
is a DC discharge lamp, 7 is a current detection element, 8 is a superimposed voltage generation circuit, 9 is an error amplifier, 10 is a reference power supply, 1
1 is a pulse width control circuit, 12 is a drive circuit, 13 is an auxiliary power supply, and 14 is a control section.

Claims (1)

[Claims] 1. A main circuit in which an inverter section, a rectifier, a smoothing circuit, and a current detection element are connected in this order, and a superimposed voltage generation circuit is connected to the output side of the smoothing circuit; and a main circuit connected to the inverter section. a drive circuit, a pulse width control circuit, and an error amplifier, one of the inputs of the error amplifier is connected to a reference power supply, the other is connected to the current detection element, and one of the inputs of the error amplifier is connected to the reference power supply. a control unit is connected between the error amplifiers, and the control unit includes a transistor for grounding one of the inputs of the error amplifier, and a capacitor and a resistor connected to the drive side of the transistor to determine its opening/closing time. A lighting device for a DC discharge lamp, comprising: a constant circuit; and a receiving section that detects a voltage applied to both ends of the discharge lamp and short-circuits a capacitor of the time constant circuit when the voltage is higher than a reference voltage.