JPS6226791A - Discharge lamp lighting apparatus - 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 equipped with a high voltage pulse generation circuit.

[Background Art] Fig. 5 shows a conventional example of this type of discharge lamp lighting device, in which a frequency converter 2 is connected to a DC power source 1, and a current-limiting choke coil is connected between the output terminals of the frequency converter 2. 3 and
A discharge lamp 6 is connected through the secondary winding of the pulse transformer 5 of the high voltage pulse generation circuit 4, and the output of the DC power supply 1 is converted to AC by the frequency converter 2, and the AC voltage output is used to limit the The discharge lamp 6 is turned on via the diversion choke coil 3 and the secondary winding of the high voltage pulse transformer 5.

The high voltage pulse generation circuit 4 is the high voltage pulse transformer 5
, bidirectional 2-terminal thyristor 7, capacitor 8, resistor 9
It is configured to superimpose a high voltage pulse on the output voltage of the frequency converter 2 and start the discharge lamp 6.

The operation of this high voltage pulse generation circuit 4 will be explained based on the operation waveform diagram shown in FIG.
The capacitor 8 is charged by the output voltage ■1, and the voltage Vc across the capacitor 8 rises.

As shown in FIG. 6(b), when the bidirectional two-terminal thyristor 7 reaches the breakover voltage ■, o, the bidirectional two-terminal thyristor 7 turns on and transfers the charge in the capacitor 8 to the capacitor 8. The primary winding of the high-voltage pulse transformer 5 is discharged in a closed circuit of a bidirectional two-terminal thyristorph. Due to this discharge, a high voltage pulse is generated on the secondary side of the high voltage pulse transformer 5 according to the winding ratio, as shown in Fig. 6(e).
As shown in FIG. 2, the voltage across the discharge lamp 6 is superimposed on the voltage (2) at both ends of the discharge lamp 6, and is applied to the discharge lamp 6. The discharge lamp 6 is started and lit when the peak value of this high voltage pulse exceeds the starting voltage. When the discharge lamp 6 is turned on, the voltage across the capacitor 8 decreases, and the voltage across the time constant circuit consisting of the capacitor 8 and the resistor 9 also decreases, so the voltage across the capacitor 8 after startup decreases.
c does not reach the breakover voltage V9Q of the bidirectional two-terminal thyristorph during the half cycle of the AC output voltage V1 of the frequency converter 2, and the high voltage pulse is no longer applied to the secondary side of the high voltage pulse transformer 5. It will no longer occur.

However, in this conventional circuit, if the difference between the no-load output voltage (1) of the frequency converter 2 and the voltage (2) across the discharge lamp 6 is small, the breakover voltage (I? Due to variations in O or an increase in lamp voltage, the bidirectional two-terminal thyristor 7 operates even when the discharge lamp 6 is lit, causing the high voltage pulse generation circuit 4 to operate, causing unstable lighting of the discharge lamp 6. This may cause flickering.

Therefore, in order to prevent malfunctions such as those mentioned above, especially for discharge lamps such as metal halide lamps, where the lamp voltage increases at the end of life, the lamp voltage increase should be taken into consideration.
Frequency converter 2 is configured so that the difference between voltages V, V2 is large.
The problem is that this requires designing the output voltage (1), which increases restrictions on circuit design and disadvantages in terms of cost, size, etc.

[Object of the Invention] The present invention was made in view of the above-mentioned problems, and its purpose is to reduce the difference between the no-load output voltage of the frequency converter and the lamp voltage of the discharge lamp even if the difference is small. To provide a discharge lamp lighting device in which a high voltage pulse generation circuit does not malfunction.

[Disclosure of the Invention] The present invention connects a frequency converter to a DC power supply, connects a series circuit of a resistor and a capacitor between the discharge lamp and the output terminal of the frequency converter, and the voltage across the capacitor reaches a predetermined value. Then, in a discharge lamp lighting device in which a series circuit with a high-voltage pulse generation circuit that generates a pulse to start the discharge lamp is connected to at least the output terminal of the frequency converter, the voltage across the capacitor increases at the time of starting the discharge lamp. The present invention is characterized by comprising means for increasing the output frequency of the frequency converter so that the polarity of the output voltage of the frequency converter is reversed before reaching a predetermined value.

This will be explained below using examples.

Figure 1 shows the circuit configuration of this embodiment. In this embodiment, a so-called full-bridge inverter circuit consisting of transistors Q, ~transistors Q4, and diodes D1~D is used. , Q, and transistors Q 2 and Q 3 alternately repeat on/off operations to produce a rectangular wave output voltage ■1 as shown in FIG. 6(a).
Output. The transistors Q1 to Q4 are controlled using a control circuit 10 consisting of a switching regulator IC (for example, iR3MO2 manufactured by Sharp Corporation), and the output signal of the control circuit 10 is inverted by an inverter 11.12, and the inverted signal is used to control the transistor 13. .14 are operated alternately, transformer 15.15', resistor 16 to 23
, and drives transistors Q1 to Q4 via a transistor base drive circuit 28 made up of diodes 24 to 27. Transistors Q, , Q, and transistor Q2. The switching frequency of Q is outside the control circuit 10 (the dimensions are resistor 29.30 and capacitor 31
It is determined by the time constant determined by . The frequency switching circuit 32 switches the time constant that determines the switching frequency of the control circuit 10 by turning on and off a transistor 33 connected in parallel to the resistor 30, and this switching is performed when the lamp current flows when the discharge lamp 6 is turned on. This is done when a current is detected.

When all DC power sources 1 are connected and the device is started, the capacitor 8 of the high voltage pulse generation circuit 4 is charged by the AC output voltage V1 of the frequency converter 2 according to a time constant determined by the capacitor 8 and the resistor, and the voltage across the When Vc reaches the breakover voltage V130 of the bidirectional two-terminal thyristor, the thyristor 7 is turned on, discharging the charge in the capacitor 8 as in the circuit of FIG. A high voltage pulse is generated and superimposed on the output voltage V of the frequency converter 2. The discharge lamp 6 is started and lit by the superposition of this high voltage pulse. At this time, the secondary winding of the high voltage pulse transformer 5, the discharge lamp 6, and the capacitor 3
The high voltage pulse transformer 5 constitutes a closed circuit such that the high voltage pulse generated in the secondary winding of the high voltage pulse transformer 5 is not applied to the output end of the frequency converter 2.

Now, when the discharge lamp 6 is turned on, a lamp current flows through the discharge lamp 6 and charges the capacitor 37 via the lamp current detection resistor 34 and the diode 36.

The voltage V c z 7 across the capacitor 37 rises, and the voltage of the reference voltage source 38 and the voltage V e 37 are compared by the comparator 3 . Here, when the voltage V C ) 7 exceeds the reference voltage, an output is generated from the comparator 39 and turns on the transistor 33 . This ON causes the resistor 30 to be short-circuited, thereby reducing the resistance value of the time constant of the control circuit 10.

The control circuit 10 has a built-in oscillator and a flip-flop circuit, and frequency-divided pulse signals are outputted to the pair of output terminals as shown in FIGS. 2(a) and (b), and the frequency of the pulse signals is It is determined by a time constant formed by the attached resistor 29, 30 and capacitor 31, and when the time constant is large, the frequency is low, and conversely, when the time constant is small, the frequency is high.

FIGS. 2(c) and 2(d) show pulse signals to the bases of transistors 13,14.

Now, as mentioned above, the time constant resistor 30 is the transistor 33
When short-circuited at , the oscillation frequency of the control circuit 14 increases. Here, the half cycle time L0 of the oscillation frequency of the control circuit 14 determined by the two resistors and the capacitor 31 is determined by the capacitor 8 after the polarity of the output voltage V1 of the frequency converter 2 is reversed.
The time constants of the two resistors and the capacitor 31 are set so that the voltage Vc at both ends of the voltage Vc reaches the breakover voltage ■BO of the bidirectional two-terminal thyristor. The frequency f<1/2t0, and after lighting, the frequency>1/2t.

Therefore, the output voltage ■1 of the frequency converter 2 is as shown in Fig. 3(a).
When it becomes high as shown in , the voltage Vc across the capacitor 8
The breakover voltage VBO of the bidirectional two-terminal thyristor 7 is no longer reached within a half cycle of the output voltage Vc.

A power supply 40 in FIG. 1 constitutes a power supply for the control system of transistors Q1 to Q.

Figure 4 shows the circuit configuration of four parts of the high-voltage pulse generation circuit of this embodiment. In this embodiment, the high-voltage pulse generation circuit 4 is different from that of embodiment 1, and the other circuits are the same as those of the embodiment. 1, similar circuit configurations are omitted in the figure.

Capacitor 8 is set by the time constant circuit of resistor 9 and capacitor 8.
is charged, and when the voltage Vc across it reaches the breakover voltage of the voltage responsive trigger element 41, the trigger element 41
is turned on, making the triac 42 conductive. Due to this conduction, the electric charge of the capacitor 43 connected in parallel to the discharge lamp 6 is discharged through an open circuit of the capacitor 43, the primary winding of the pulse transformer 5, the capacitor 44, and the triac 42, and at this time, the pulse transformer 5 A high voltage pulse is generated on the secondary side of the coil according to the winding ratio. After the discharge lamp 6 is turned on, the same operation as in the first embodiment is performed.

The frequency converter 1 on each of the actual flow sides may be not only a full-bridge type, but also a half-bridge type, a push-pull type, or any other type of inverter circuit that can vary the frequency.

[Effects of the Invention] The present invention provides a discharge lamp lighting device configured as described above, in which the polarity of the output voltage of the frequency converter is reversed before the voltage across the capacitor reaches a predetermined value at the time of starting the discharge lamp. Since the above-mentioned frequency conversion device is equipped with a means for increasing the output frequency, the lighting period of the discharge lamp is shorter than the high voltage pulse generation period of the high voltage pulse generation circuit, so the lighting polarity can be changed before the high voltage pulse is generated. can be changed,
This eliminates malfunctions such as high voltage pulses occurring during lighting, and eliminates the difference between the no-load secondary voltage and the lamp voltage, especially when the lamp voltage increases, such as at the end of a metal halide lamp's life. This has the effect that there is no need to make the load secondary voltage particularly high.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of the first embodiment of the present invention, FIGS. 2 and 3 are waveform diagrams for explaining the operation of the above, and FIG. 4 is a circuit diagram of the second embodiment of the present invention.
5 is a circuit diagram of a conventional example, and FIG. 6 is a waveform diagram for explaining the operation of the same as above, 1 is a DC power supply, 2 is a frequency converter, 4 is a high voltage pulse generation circuit, and 6 is a high voltage pulse generation circuit. A discharge lamp, 8 a capacitor, 9 a resistor, and 32 a frequency switching circuit. Agent Patent Attorney Ishi 1) Chief 7 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) Connect a frequency converter to a DC power source, connect a discharge lamp,
A series circuit of a resistor and a capacitor is connected between the output terminals of the frequency converter, and at least a series circuit with a high voltage pulse generation circuit that generates a pulse to start the discharge lamp when the voltage across the capacitor reaches a predetermined value is connected. In a discharge lamp lighting device connected between the output terminals of the frequency converter, the frequency is adjusted so that the polarity of the output voltage of the frequency converter is reversed before the voltage across the capacitor reaches a predetermined value at the time of starting the discharge lamp. A discharge lamp lighting device characterized by comprising means for increasing the output frequency of the conversion device.