JP2000286080A - High-pressure discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a miniaturized high-pressure discharge lamp lighting device allowing improvement of conversion efficiency. SOLUTION: This discharge lamp lighting device has a first DC/DC converter 41 for boosting or dropping an output voltage of a rectification circuit 2 and converting it into a DC voltage to output the DC voltage, a second DC/DC converter 50 for converting the output voltage of the rectification circuit 2 into 400 V higher than the output voltage of the first DC/DC converter 41 and outputting it to a high-pressure discharge lamp 25 through an inverter 44 at the time of starting of a high-pressure discharge lamp 25, and for converting a DC voltage into 800 V, and a high-voltage pulse generation circuit for generating a high-voltage pulse and applying the pulse to the high-pressure discharge lamp 25 at the input of the voltage of 800 V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high pressure discharge lamp lighting device provided with an inverter.

[0002]

2. Description of the Related Art FIG. 6 is a circuit diagram of a conventional high pressure discharge lamp lighting device disclosed in, for example, Japanese Patent Application Laid-Open No. 9-55296. In the figure, 1 is a commercial power supply, 2 is a rectifier circuit that full-wave rectifies an AC voltage supplied from the commercial power supply 1, 3 is a boost converter circuit that boosts the output voltage of the rectifier circuit 2, and an input voltage detection resistor 4; An input current detection resistor 5, a step-up coil 6, a power MOS FET 7 for step-up, a diode 8, an electrolytic capacitor 9, a step-up voltage detection resistor 10,
And a boost control circuit 11.

A step-down converter circuit 12 converts the output of the step-up converter circuit 3 into constant power.
-It is composed of an FET 13, a freewheel diode 14, a step-down coil 15, a smoothing capacitor 16, an output current detection resistor 17, and a step-down control circuit 18. 1
An inverter circuit 9 converts the output of the step-down converter circuit 12 into a low-frequency rectangular wave voltage and supplies the voltage to the discharge lamp 25.
Power MOSFET 20 connected in full bridge form
And 23 and a rectangular wave control circuit 26.

[0004] A starting circuit 24 is a choke coil 27.
A charging / discharging capacitor 28 connected to one end of the choke coil 27, a bidirectional switching element 29 connected to an intermediate tap of the choke coil 27, and a connection point between the charging / discharging capacitor 28 and the bidirectional switching element 29. And the connected charging resistor 30. Reference numeral 31 denotes a capacitor for bypassing a high-voltage pulse generated from the starting circuit 24, and reference numeral 32 denotes a control power supply circuit that supplies a control voltage to the control circuits 11, 18, and 26.

Reference numeral 33 denotes a boost voltage switching relay having a normally open relay contact 33a, and reference numeral 34 denotes an adjustment resistor connected in parallel to one of the boost voltage detection resistors 10 via the relay contact 33a. 35 is an input voltage detection circuit, which is a rectifier circuit 2
When the output voltage is 141V (commercial power supply 100V), the relay contact 33a is kept normally open, and the output voltage is 282V.
(Commercial power supply 200 V), the boost voltage switching relay 33
To close the relay contact 33a.

[0006] In the conventional high pressure discharge lamp lighting device configured as described above, when the commercial power supply 1 is applied, the rectifier circuit 2 performs full-wave rectification of the AC voltage, and the input voltage detection circuit 35.
Is 1 when the output voltage 141V of the rectifier circuit 2 is detected.
When it is determined that the commercial power supply 1 of 00V is applied, the off state of the relay contact 33a is maintained, and the output voltage 28 of the rectifier circuit 2 is
When 2V is detected, it is determined that 200 V commercial power supply 1 has been applied, and relay contact 33a is turned on.

The boost converter circuit 3 includes a relay contact 33
To obtain an output voltage of 250 V when a is off,
When the relay contact 33a is on, the commercial power supply 1 is converted into a DC voltage at a high power factor so that an output voltage of 350 V is obtained, and the step-down converter circuit 12 converts the output of the step-up converter circuit 3 into constant power, and The circuit 19 includes a power MOS · F in order to reliably light the high-pressure discharge lamp 25.
ET20 and 23 are turned on, and power MOS / FE
T21 and T22 are turned off to maintain the state, and the DC voltage from the boost converter circuit 3 is applied through the step-down converter circuit 12 and the power MOSFETs 20 and 23.
At this time, the starting circuit 24 superimposes the high-voltage pulse generated in the choke coil 27 on the DC voltage, and
Is applied.

When the high pressure discharge lamp 25 starts lighting, the step-down converter circuit 12 controls the output voltage so that the current flowing through the high pressure discharge lamp 25 becomes a predetermined current.
The inverter circuit 19 converts the DC voltage of the step-down converter circuit 12 into a low-frequency rectangular wave voltage of about 100 Hz higher than the frequency of the commercial power supply 1 and supplies it to the high-pressure discharge lamp 25 in order to suppress flicker of the high-pressure discharge lamp 25. I do.

[0009]

In the conventional high pressure discharge lamp lighting device described above, the conversion efficiency of each of the boost converter circuit 3 and the step-down converter circuit 12 is 92%, and the conversion efficiency of the inverter circuit 19 is 99%. However, since these are connected in series, the conversion efficiency of the high pressure discharge lamp lighting device is reduced to 0.92 × 0.92 × 0.99 = 84%, and the conversion efficiency of the step-up converter circuit 3 and the step-down converter is reduced. Since the size of the booster coil 6 and the step-down coil 15 provided in the converter circuit 12 is large, it is difficult to reduce the size of the lighting device.

The sizes of the boosting coil 6 and the step-down coil 15 can be reduced by increasing the switching frequency of the step-up power MOS-FET 7 and step-down power MOS-FET 13.
The switching loss of the FETs 7 and 13 increases, and the conversion efficiency further decreases. In this case, it is possible to reduce the switching loss by increasing the heat radiation fins of the power MOS FETs 7 and 13, but this time the size of the power MOS FETs 7 and 13 becomes large and the lighting device itself is reduced in size. I couldn't do that.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a high-pressure discharge lamp lighting device capable of reducing the size of a lighting device and improving conversion efficiency.

[0012]

According to a first aspect of the present invention, there is provided a high pressure discharge lamp lighting apparatus comprising: a rectifier circuit for full-wave rectifying a commercial power supply; and an output voltage of the rectifier circuit is boosted based on driving of a switching element. Alternatively, a first DC / DC converter for converting the voltage into a direct current by a capacitor provided in advance and outputting the converted direct current, an inverter provided on the output side of the first DC / DC converter, and an input of a start signal form a switching element. When driven, the output voltage of the rectifier circuit is changed to the first DC
A second DC / DC converter that transforms the DC voltage to a second voltage higher than the first voltage while transforming the DC voltage to a first voltage higher than the output voltage of the DC / DC converter and outputs the second voltage to the inverter; A high-pressure pulse generating circuit that generates a high-pressure pulse when applied to the high-pressure discharge lamp, and a discharge lamp voltage detection unit that detects a discharge lamp voltage of the high-pressure discharge lamp,
Target current determining means for determining a target current according to the discharge lamp voltage detected by the discharge lamp voltage detecting means; discharge lamp current detecting means for detecting a discharge lamp current flowing through the high pressure discharge lamp; Outputting the start signal to a second DC / DC converter to apply the first voltage to a high-pressure discharge lamp via an inverter, and to supply the second voltage to a high-voltage pulse generating circuit to discharge a high-voltage pulse to a high voltage. After the high-pressure discharge lamp is started, the rate of increase is calculated from the discharge lamp voltage detected by the discharge lamp voltage detection means and compared with a predetermined value. The switching element of the second DC / DC converter is controlled so that the discharge lamp current detected by the detection means is equal to the target current. When the rate of increase is less than a predetermined value, the discharge lamp current is The to be the same and the target current 1
Control means for controlling a switching element of the DC / DC converter.

In a high pressure discharge lamp lighting device according to a second aspect of the present invention, the control means controls the switching element of the second DC / DC converter at a switching frequency higher than the switching frequency of the switching element of the first DC / DC converter. It is.

In a high pressure discharge lamp lighting device according to a third aspect of the present invention, the high voltage pulse generating circuit is provided with a transformer for transforming the second voltage to a high voltage.

In the high pressure discharge lamp lighting device according to a fourth aspect of the present invention, the control means controls the inverter at a commercial frequency while controlling the second DC / DC converter.

In a high pressure discharge lamp lighting device according to a fifth aspect of the present invention, when the control means is controlling the second DC / DC converter, the output voltage of the first DC / DC converter is the output voltage of the second DC / DC converter. The switching element of the first DC / DC converter is controlled so that the voltage becomes several volts lower than the voltage.

[0017]

FIG. 1 is a circuit diagram of a high pressure discharge lamp lighting device according to an embodiment of the present invention. The same or corresponding parts as those in the conventional example described with reference to FIG. In the figure, reference numeral 41 denotes a first DC / DC converter, which is connected between a transformer 41a having one end of a primary winding connected to the positive pole side of the rectifier circuit 2 and a negative pole side of the transformer 41a. , A diode 41c connected to one end of the secondary winding of the transformer 41a, and a smoothing capacitor 41d connected in parallel to the secondary winding of the transformer 41a. The DC voltage is transformed (step-up or step-down) on the basis of the ON time of, and is converted to DC by the smoothing capacitor 41d and output.

Reference numeral 42 denotes a diode inserted on the plus side of the first DC / DC converter 41, and 43 denotes a first DC / D converter.
A capacitor connected between both poles of the C converter 41,
44 is a bridge type inverter. 45 is a rectifier circuit 2
A first voltage detection circuit for detecting a zero-cross waveform of a commercial power supply by detecting an output voltage of the first DC / DC converter 41, a second voltage detection circuit for detecting a DC voltage converted by the first DC / DC converter 41, and a high-voltage discharge circuit 47 A third voltage detection circuit for detecting the voltage supplied to the lamp 25, 48 is a resistor inserted on the minus pole side of the first DC / DC converter 41, and 49 is a fourth voltage for detecting the voltage across the resistor 48. It is a detection circuit.

Reference numeral 50 denotes a second DC / DC converter, one end of a primary winding is connected to the positive pole side of the rectifier circuit 2, and both ends of the secondary winding are connected to a high-voltage pulse generating circuit described later.
The intermediate tap of the secondary winding is connected to the first D
A transformer 50a connected to the positive pole side of the C / DC converter 41, a primary winding of the transformer 50a, and a rectifier circuit 2
Switching element 5 inserted between the negative pole side of
When the high-pressure discharge lamp 25 is started, the voltage between both ends of the secondary winding of the transformer is set to 800 V (second voltage) under the control of a control circuit described later, and one end of the secondary winding and the intermediate tap are connected to each other. Is 400 V (first voltage).

Reference numeral 52 denotes a high-voltage pulse generating circuit,
A diode 52a, a resistor 52b, and a capacitor 52c inserted between both ends of a secondary winding of a transformer 50a of the DC converter 50, a transformer 52d, and a discharge gap inserted between the primary winding of the transformer 52d and the capacitor 52c. 52e, and a secondary winding of a transformer 52d connected in series and a capacitor 52f connected in parallel to the high-pressure discharge lamp 25.

In the transformer 52d, one end of a primary winding is connected to a connection point of a resistor 52b and a capacitor 52c.
The other end is connected to the discharge gap 52e, and one end of the secondary winding is connected to the switching element 44 of the inverter 44.
c, 44d, and the other end of the secondary winding is connected via a high-pressure discharge lamp 25 to the connection point of the switching elements 44a, 44b of the inverter 44.
The secondary winding of d has, for example, five times the number of turns of the primary winding.

The discharge gap 52e is connected to a capacitor 52c.
Turns on when the charging voltage reaches 800V. At this time,
A high voltage of 4 KV, which is five times the terminal voltage of the capacitor 52c, is generated on the secondary side of the transformer 52d. Capacitor 52f
Is for preventing a high voltage generated on the secondary side of the transformer 52d from sneaking into the inverter 44.

Reference numeral 53 denotes a control circuit, which is a switching element of the second DC / DC converter 50 when the high-pressure discharge lamp is started.
Is driven between both ends of the secondary winding of the transformer 50a.
0 V, a voltage of 400 V is generated between one end thereof and the intermediate tap, and a voltage of 400 V is applied to the high-pressure discharge lamp 25 via the diode 51 and the inverter 44 to generate a voltage of 800 V.
The V voltage is supplied to the high-voltage pulse generation circuit 52 to apply a high-voltage pulse to the high-pressure discharge lamp 25. After the high-pressure discharge lamp is started, the discharge lamp voltage change rate is calculated based on the discharge lamp voltage detected by the third voltage detection circuit 47. B (increase rate) is calculated and compared with a predetermined value β. When the change rate B is equal to or more than the predetermined value β, the discharge lamp current A obtained from the detection voltage of the fourth voltage detection circuit 49 is the same as the target current. The 50 switching element 50b of the second DC / DC converter is controlled so that At this time, the first
The switching element 41b of the DC / DC converter 41 is driven to control the output voltage to be several volts lower than the output voltage of the second DC / DC converter. When the discharge lamp voltage change rate B is less than the predetermined value β, the switching element 41b of the first DC / DC converter 41 is controlled so that the discharge lamp current A becomes equal to the target current.

The switching element 50b of the second DC / DC converter 50 is controlled at a switching frequency higher than the switching frequency of the switching element 41b of the first DC / DC converter 41 until the lighting of the high-pressure discharge lamp 25 is stabilized. . While the second DC / DC converter 50 is being controlled, the inverter 44 is controlled at a commercial frequency, as will be described in detail when the operation is described.

The operation of the high pressure discharge lamp lighting device of the present embodiment configured as described above will be described with reference to the following drawings. 2 is a flowchart showing the operation from the start of the high pressure discharge lamp lighting device according to the embodiment to the stable lighting of the high pressure discharge lamp, FIG. 3 is an operation waveform diagram of the high pressure discharge lamp lighting device in the embodiment, and FIG. FIG. 5 is a voltage-current characteristic diagram of gas discharge of an electric lamp, and FIG. 5 is an operation waveform diagram of a first DC / DC converter of the high-pressure discharge lamp lighting device according to the embodiment.

When the commercial power supply 1 is turned on to the lighting device,
The control circuit 53 controls on / off of the switching element 50b of the second DC / DC converter 50. When the switching element 50b is on, the DC current from the rectifier circuit 2 flows through the primary winding of the transformer 50a to the switching element 50b, and electric energy is stored in the primary winding. When the switching element 50b is turned off, the electric energy stored in the primary winding is boosted by the secondary winding and stored in the capacitor 43 via the diode 51.
The voltage is stored in the capacitor 52c via the resistor 2a and the resistor 52b.

At this time, the control circuit 53 detects the voltage across the capacitor 43 through the third voltage detection circuit 47,
The on-time of the switching element 50b is controlled so that the voltage between both ends becomes 400 V (S21). When the voltage between both ends of the capacitor 43 becomes 400 V, the voltage applied to the high-voltage pulse generating circuit 52 becomes 800 V. S2
After one operation, the switching element 44 of the inverter 44
a, 44d, and the switching element 44
b, 44c are turned off, and a DC voltage of 400 V is applied to the high-pressure discharge lamp 25 (S22).

On the other hand, when the voltage stored in the capacitor 52c of the high-voltage pulse generating circuit 52 reaches 800 V, the discharge gap 52e is turned on, and a voltage of 800V is applied to the primary winding of the transformer 52d, and the secondary voltage of the transformer 52d is increased. A high voltage (4 KV) five times 800 V is generated in the winding (S2
3).

At this time, the high pressure discharge lamp 25 is
As shown in the area, a voltage having a waveform in which a high voltage pulse (H3) of 4 KV is superimposed on a voltage of 400 V (H4) is applied. The high-voltage pulse of 4 KV causes breakdown of the high-pressure discharge lamp 25 and shifts to glow discharge. The voltage of 400 V overcomes the peak voltage of the glow discharge and shifts to arc discharge (see FIG. 4).

At this time, the control circuit 53 reads the voltage across the resistor 48 via the fourth voltage detection circuit 49 and detects the discharge lamp current A flowing through the high pressure discharge lamp 25 (S24).
It is compared with a predetermined value α (S25). If the discharge lamp current A is less than the predetermined value α, it is determined that the high pressure discharge lamp 25 has not shifted to arc discharge, and the above-described operation is repeated again (S
21 to S24), when the discharge lamp current A is equal to or more than the predetermined value α, it is determined that the high pressure discharge lamp 25 has shifted to arc discharge, and the discharge lamp voltage V1 of the high pressure discharge lamp 25 is determined by the third voltage detection circuit 47. (S26). Then, a target current of the high-pressure discharge lamp 25 is calculated from the read discharge lamp voltage V1 (S27). For example, when the discharge lamp voltage V1 of the high-pressure discharge lamp 25 having a rated power of 150 W is read and the value is 75 V, the target current is 150/75 = 2A.

After the calculation of the target current, the discharge lamp voltage V2 (not shown) of the high-pressure discharge lamp 25 is read again through the third voltage detection circuit 47, and the discharge lamp voltage V1 and the voltage V1 read in S26 are read. Elapsed time T from reading
From this, the discharge lamp voltage change rate B = (V2-
V1) / T is calculated (S28) and compared with a predetermined value β (S29). If the discharge lamp voltage change rate B is less than the predetermined value β, it is determined that the lighting state of the high pressure discharge lamp 25 is stable, and the operation of S33 is started.
In the above case, the lighting state of the high-pressure discharge lamp 25 is determined to be a transient state and unstable, and the operation of S30 is started.

At this time, since the discharge lamp voltage change rate B is large when the high pressure discharge lamp 25 shifts to arc discharge (see the area M2 in FIG. 3), the inverter 44 is switched to the commercial power supply 1
Operate in synchronization with the frequency. In this case, the control circuit 53
Detects the zero-cross waveform of the commercial power supply 1 via the first voltage detection circuit 45, and turns on the set of the switching elements 44a and 44d and the set of the switching elements 44b and 44c of the inverter 44 alternately in synchronization with the zero-cross. / Off (S30). At this time, the inverter 44 is connected to the second DC
The DC voltage from the / DC converter 50 is converted into an AC voltage synchronized with the frequency of the commercial power supply 1 and supplied to the high-pressure discharge lamp 25 (see H4 in the M2 region in FIG. 3).

On the other hand, the control circuit 53 determines that the discharge lamp current A obtained based on the detection of the fourth voltage detection
7 so that the second DC / D
The switching element 50b of the C converter 50 is controlled (S31), and the switching element 41b of the first DC / DC converter 41 is driven to obtain a DC voltage several volts lower than the output voltage of the second DC / DC converter 50. (S32). The first DC / DC converter 41 has poor response and may not respond to the change in the discharge lamp voltage in the M2 region where the change in the discharge lamp voltage is large.
The operation of the / DC converter 50 is continued. 1st DC
After the control of the / DC converter 41 is performed, S26 is performed again.
, The discharge lamp voltage change rate B of the high-pressure discharge lamp 25
Are repeatedly executed until S is less than the predetermined value β, that is, until shifting from the M2 area to the M3 area.

By repeating this operation, the high pressure discharge lamp 25
When the discharge lamp voltage change rate B becomes less than the predetermined value β (M3 region), the control circuit 53 determines the set of the switching elements 44a and 44d and the switching elements 44b and 4 of the inverter 44.
The set 4c is alternately turned on / off at a low frequency of 120 Hz (S33), and the operation of the second DC / DC converter 50 is stopped (S34). Next, the discharge lamp current A of the high-pressure discharge lamp 25 obtained based on the detection of the fourth voltage detection circuit 49.
Is equal to the target current calculated in S27.
The switching element 41b of the DC / DC converter 41 is controlled (S35). When the discharge lamp current A of the high-pressure discharge lamp 25 is lower than the target current, the ON time of the switching element 41b is lengthened to increase the output voltage of the first DC / DC converter 41, and the discharge lamp current A of the high-pressure discharge lamp 25 reaches the target. When the current is higher than the current, the on-time of the switching element 41b is shortened to lower the output voltage. After that,
The operation starts again in S26, and the above operation is repeatedly executed until the commercial power supply 1 is turned off (S26 to S29,
S33 to S35).

At this time, the control circuit 25 controls the first DC / DC
Control is performed so that converter 41 can step up and down at a high power factor. For example, the ON time of the switching element 41b is set to 20 so that the discharge lamp current A of the high pressure discharge lamp 25 becomes the target current.
When set to μs, the ON time is limited by the instantaneous value of the full-wave rectified voltage (see H5 in FIG. 5) detected by the first voltage detection circuit 45, and is set to 20 × K × sin
θ (K is a proportional constant), the switching element 41
The current flowing through b has a waveform as shown by H6 in FIG.
For this reason, the current flowing into the first DC / DC converter 41 is synchronized with the commercial power supply 1 as indicated by H7 in FIG.
The current becomes in and the power factor becomes high.

As described above, according to the present embodiment, since the high voltage for the high-pressure discharge lamp 25 to go over the glow discharge region is output from the second DC / DC converter 50, the first DC / DC converter 41 Can be used as the capacitor 41d, which has a lower withstand voltage than the conventional one, and the lighting device can be downsized.

The M2 region where the change of the discharge lamp voltage is large (FIG. 3)
2), the driving of the second DC / DC converter 50 is continued, so that the high-pressure discharge lamp 25 can be prevented from going out only by driving the first DC / DC converter 41 having poor response. In the M3 region where the discharge lamp voltage H1 of the high-pressure discharge lamp 25 is stable and the discharge lamp voltage change rate B is small, only the first DC / DC converter 41 is driven, so that the conversion of the first DC / DC converter 41 is performed. The efficiency is 90%, and the conversion efficiency of the inverter is 89% when the conversion efficiency is 99%, which is the same as the conventional one.

Further, the switching element 50b of the second DC / DC converter 50 is controlled at a switching frequency higher than the switching frequency of the switching element 41b of the first DC / DC converter 41 for several tens of seconds during which the discharge lamp voltage of the high-pressure discharge lamp 25 is stabilized. The second
Although the conversion efficiency of the DC / DC converter 50 is slightly deteriorated, the second DC / DC converter 50 can be reduced in size without any problem.

When the high pressure discharge lamp is started, the second DC / DC
Since a high voltage of 800 V from the converter 50 is applied to the transformer 52d of the high-voltage pulse generating circuit 52, the number of turns of the secondary winding of the transformer 52d can be reduced,
Therefore, there is an effect that the transformer 52d can be made smaller.

Further, while the second DC / DC converter 50 is being driven, the inverter 44 is operated in synchronization with the commercial frequency, so that although the high-pressure discharge lamp 25 slightly flickers, the discharge lamp current is increased. As indicated by H4 in the M2 region of FIG. 3, there is an effect that the current becomes a sine wave current and the power factor becomes high.

Further, the second DC / DC converter 5
0 is being driven, the first DC / DC converter 4
1 is controlled to be several volts lower than the output voltage of the second DC / DC converter 50.
When the lighting state of the high-pressure discharge lamp 25 enters the stable region (M3 region in FIG. 3), switching from the second DC / DC converter 50 to the first DC / DC converter 41 can be performed smoothly with a small voltage step, and therefore. This has the effect of reducing flash and flicker.

[0042]

According to the first aspect of the present invention, when the high pressure discharge lamp is started, the first voltage higher than the output voltage of the first DC / DC converter and the second voltage higher than the first voltage are applied to the second DC / DC converter.
Since the output is made from the DC converter, the capacitor of the first DC / DC converter can be a small capacitor having a lower withstand voltage as compared with the conventional one, and the lighting device can be downsized. When the rate of increase obtained from the discharge lamp voltage is equal to or greater than a predetermined value, the second DC / DC converter is continuously driven.
The high-pressure discharge lamp can be prevented from being extinguished only by driving the C / DC converter, and when the rate of rise becomes less than a predetermined value, the first DC is controlled so that the discharge lamp current becomes the same as the target current.
Since the voltage is directly supplied to the inverter by controlling the / DC converter, a step-down converter is not required as in the related art, and therefore, there is an effect that the conversion efficiency is improved as compared with the conventional lighting device.

According to the invention of claim 2 of the present application, the second DC
The switching element of the DC / DC converter is the first DC / DC
Since the control is performed at a switching frequency higher than the switching frequency of the switching element of the converter, the second DC / DC converter can be downsized without any problem, although the conversion efficiency of the second DC / DC converter is slightly deteriorated.

According to the invention of claim 3 of the present application, when the high-pressure discharge lamp is started, the second high voltage is applied from the second DC / DC converter to the transformer of the high-voltage pulse generating circuit. The number of turns of the windings can be reduced, which has the effect of reducing the size of the transformer.

According to the invention of claim 4 of the present application, the second DC
While the / DC converter is driven, the inverter is operated in synchronization with the commercial frequency. Therefore, although the high-pressure discharge lamp slightly flickers, the discharge lamp current becomes a sine wave current and the power factor becomes high. effective.

According to the invention of claim 5 of the present application, the second DC
When the DC / DC converter is operating, the first DC / D
Since the output voltage of the C converter is controlled to be several volts lower than the output voltage of the second DC / DC converter, when the lighting state of the high-pressure discharge lamp enters a stable region, the second DC / DC converter switches the first DC / DC converter to the first DC / DC converter. Switching to / DC converter can be performed smoothly with few voltage steps.
Therefore, there is an effect that flash and flicker are reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a high pressure discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation from the start of the high-pressure discharge lamp lighting device according to the embodiment to the stable lighting of the high-pressure discharge lamp.

FIG. 3 is an operation waveform diagram of the high pressure discharge lamp lighting device in the embodiment.

FIG. 4 is a voltage-current characteristic diagram of gas discharge of a high-pressure discharge lamp.

FIG. 5 is a first view of the high pressure discharge lamp lighting device according to the embodiment.
3 is an operation waveform diagram of the DC / DC converter of FIG.

FIG. 6 is a circuit diagram of a conventional high pressure discharge lamp lighting device.

[Explanation of symbols]

41 first DC / DC converter, 44 inverter,
45 first voltage detection circuit, 46 second voltage detection circuit, 47 third voltage detection circuit, 49 fourth voltage detection circuit, 50 second DC / DC converter, 52 high-voltage pulse generation circuit, 53 control circuit.

Continued on the front page F-term (reference) 3K072 AA11 AC01 BA03 BA05 BB01 BB10 DD08 EB05 EB07 GA03 GB18 GC04 HA06 HB03 3K083 AA76 AA92 BA04 BA25 BA26 BC19 BC34 BC42 BC47 BD03 BD04 BD13 BD16 BD22 BE02 CA32 5H007 AA02 AA04 CB03 DA05 DA06 DC02 DC05 GA01 5H730 AA14 AA16 AA18 AS01 AS11 BB43 BB82 BB85 CC01 DD04 EE07 EE65 FD01 FD11 FF09 FG01 FG16 FG22

Claims (5)

[Claims] A rectifier circuit for full-wave rectification of a commercial power supply, a step-up or a step-down of an output voltage of the rectifier circuit based on driving of a switching element, and converting the output voltage into a direct current by a capacitor provided in advance and outputting the converted DC. A first DC / DC converter, an inverter provided on the output side of the first DC / DC converter, and an output voltage of the rectifier circuit when the switching element is driven by the input of a start signal from an output voltage of the first DC / DC converter. A second DC / DC converter for converting the DC voltage to a second voltage higher than the first voltage while generating a high voltage and outputting the same to the inverter; and generating a high-voltage pulse when the second voltage is input. A high-pressure pulse generating circuit applied to the high-pressure discharge lamp, a discharge lamp voltage detection means for detecting a discharge lamp voltage of the high-pressure discharge lamp, and a discharge lamp voltage detection means. Target current determining means for determining a target current according to the detected discharge lamp voltage, discharge lamp current detection means for detecting a discharge lamp current flowing through the high pressure discharge lamp, and a second DC / DC converter when starting the high pressure discharge lamp Output the start signal to apply the first voltage to the high-pressure discharge lamp via the inverter, and supply the second voltage to the high-pressure pulse generation circuit to apply the high-voltage pulse to the high-pressure discharge lamp, After the discharge lamp is started, a rise rate is calculated from the discharge lamp voltage detected by the discharge lamp voltage detection means and compared with a predetermined value. When the rise rate is equal to or more than the predetermined value, the discharge lamp current detection means detects the rise rate. The switching element of the second DC / DC converter is controlled so that the discharge lamp current becomes the same as the target current. When the increase rate is less than a predetermined value, the discharge lamp current becomes the same as the target current. As the first 1DC
And a control means for controlling a switching element of the DC / DC converter. 2. The high pressure discharge lamp lighting according to claim 1, wherein the control means controls the switching element of the second DC / DC converter at a switching frequency higher than the switching frequency of the switching element of the first DC / DC converter. apparatus. 3. The high pressure discharge lamp lighting device according to claim 1, wherein a transformer for transforming the second voltage to a high voltage is provided in the high voltage pulse generating circuit. 4. The high pressure discharge lamp lighting device according to claim 1, wherein the control means controls the inverter at a commercial frequency while controlling the second DC / DC converter. 5. The control means for controlling the first DC / DC converter so that the output voltage of the first DC / DC converter is several volts lower than the output voltage of the second DC / DC converter when controlling the second DC / DC converter. The switching element of the converter is controlled.
The high pressure discharge lamp lighting device according to any one of the above.