WO2006030569A1

WO2006030569A1 - Discharge lamp lighting device

Info

Publication number: WO2006030569A1
Application number: PCT/JP2005/010877
Authority: WO
Inventors: Norikazu Tateishi; Takashi Ohsawa
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2004-09-13
Filing date: 2005-06-14
Publication date: 2006-03-23
Also published as: JP2006080024A

Abstract

An inverter (3) of an H-bridge inverter circuit is provided with a bootstrap circuit for driving high potential side switching transistors (15, 16), a high potential power supply unit (4) for constantly supplying a charging current to capacitors (23, 28) by applying a potential higher than that of a load power on the high potential side outputted from the high potential side switching transistors (15, 16), diodes (20, 25), and resistors (21, 26).

Description

Specification

Discharge lamp lighting device

Technical field

The present invention relates to a discharge lamp lighting device that supplies DC power for a long time at the start of lighting of a discharge lamp.

Background art

[0002] A discharge lamp lighting device is provided with an inverter circuit for applying an AC voltage to a discharge lamp, and an H-bridge inverter circuit is generally used. An H-bridge type inverter circuit is composed of a switching element that outputs a high potential side of an AC voltage and a switching element that outputs a low potential side. The switching element includes, for example, a field effect transistor (hereinafter referred to as FET). Is used. Some H-bridge inverter circuits are equipped with a bootstrap circuit that drives an FET that outputs the high potential side. An H-bridge inverter circuit equipped with a bootstrap circuit forms a bootstrap circuit when the high-potential side FET is OFF and the low-potential side FET connected in series to the high-voltage side FET is ON. The capacitor is charged, and the voltage generated in the capacitor due to this charging is applied to the gate of the high-side FET in the ON state to stabilize the ON state of the FET, and AC power is output to the discharge lamp (for example, (See Patent Document 1).

[0003] In addition, there is a drive circuit using a full bridge circuit in which a bootstrap circuit is connected to the gate of a transistor of the full bridge circuit. This circuit is equipped with an auxiliary capacitor that compensates for the charge stored in the capacitor of the bootstrap circuit when the ONZOFF state of the opposing transistor is switched in the full bridge circuit. The auxiliary capacitor of the bootstrap circuit connected to its own gate is charged. In this circuit configuration, the charging current is not supplied to the auxiliary capacitor unless full bridge circuit power AC power is output (see, for example, Patent Document 2).

[0004] Patent Document 1: Japanese Unexamined Patent Publication No. 2000-166258 (page 4, FIG. 2)

Patent Document 2: Japanese Patent Laid-Open No. 11-69842 (Pages 4, 5 and 1) [0005] The conventional discharge lamp lighting device is configured as described above. Therefore, the ON state of the high potential side switching element is longer than that during steady lighting until the discharge phenomenon is stabilized at the start of lighting of the discharge lamp. In order to maintain this, it is necessary to provide a capacitor with a large capacity, and it is necessary to secure a space for mounting a large-capacitance capacitor, and there is a problem that the cost increases due to the provision of the large-capacity capacitor.

[0006] The present invention has been made to solve the above-described problems, and is a discharge lamp that can output DC power for a long time at the start of lighting of the discharge lamp without using a large-capacity capacitor. The object is to obtain a lighting device.

Disclosure of the invention

[0007] A discharge lamp lighting device according to the present invention includes a bootstrap circuit capacitor as a power supply for securing a gate voltage of a high-potential side switching element constituting an H-bridge inverter circuit, and an H-bridge inverter circuit connected to the capacitor. And a charging means for supplying a charging current to the capacitor at a potential higher than the high potential side.

[0008] With this, it is possible to output DC power for a long time at the start of lighting without providing a large-capacity capacitor.

Brief Description of Drawings

FIG. 1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 1 of the present invention.

FIG. 2A is a circuit diagram showing a part of an H-bridge inverter circuit of the discharge lamp lighting device according to Embodiment 1.

FIG. 2B is an explanatory diagram showing the operating state of the high potential side switching transistor and the current flowing through the capacitor of the bootstrap circuit.

FIG. 3A is an explanatory diagram showing a part of a circuit of a discharge lamp lighting device according to Embodiment 1.

FIG. 3B is an explanatory view showing a part of the circuit of the discharge lamp lighting device according to Embodiment 1.

FIG. 3C is an explanatory diagram showing a current flowing through the diode and a voltage across the diode.

FIG. 4 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 2 of the present invention.

FIG. 5 is a circuit diagram showing a schematic configuration of a discharge lamp lighting device according to Embodiment 3 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to explain the present invention in more detail, the best mode for carrying out the present invention will be described with reference to the accompanying drawings.

Embodiment 1.

FIG. 1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 1 of the present invention. Power supply 1 is a DC power supply such as a battery, and is connected to supply DC voltage to DCZDC converter (converter circuit) 2 and the like. The DCZDC converter 2 is connected so that its output voltage is supplied to an H-bridge inverter circuit (hereinafter abbreviated as an inverter) 3. The inverter 3 is connected to supply load power to the HID bulb (discharge lamp) 6 through the igniter 5.

The high potential side of power supply 1 is connected to one end of the primary winding of transformer 7 of DCZDC converter 2. The other end of the primary winding of the transformer 7 is connected to the drain of a transistor switch 8 which is a MOS transistor, for example, and the source of the transistor switch 8 is connected to the low potential side of the power source 1. An oscillator equal force pulse signal (not shown) is input to the gate of the transistor switch 8. One end of the secondary winding of the transformer 7 is connected to the anode of the diode 9 and one end of the capacitor 11. One end of the capacitor 10 is connected to the power sword of the diode 9. The other end of the capacitor 10 is connected to the other end of the secondary winding of the transformer 7. The connection point between the secondary winding of the capacitor 10 and the transformer 7 is grounded. The DC / DC converter 2 includes a transformer 7, a transistor switch 8, a diode 9, and a capacitor 10 connected in this way.

Capacitor 11 having one end connected to diode 9 of DCZDC converter 2 has the other end connected to a connection point between the force sword of diode 12 and the anode of diode 13. One end of a capacitor 14 is connected to the anode of the diode 12. The other end of the capacitor 14 is connected to the power sword of the diode 13. The connection point between the diode 12 and the capacitor 14 is connected to the connection point between the capacitor 10 and the diode 9 in the DC / DC converter 2. The capacitor 11, the diodes 12, 13 and the capacitor 14 connected in this way constitute a high potential power supply unit (charging means, booster circuit) 4.

In Fig. 1, the high potential power supply 4 and the DCZDC converter 2 are shown separately. You can configure source 4 as part of DCZDC converter 2! /. At this time, the DCZDC converter 2 is supplied with electric power supplied to the drains of switching transistors 15 and 16, which will be described later, and a capacitor (charger) 20 and 25 and a resistor (charger and current limiter) 21 and 26 through a capacitor ( Power is output to the capacitors 23 and 28 of the bootstrap circuit. The capacitors 23 and 28 function as a power supply for securing the gate voltage of the high-potential side switching element constituting the H-bridge inverter circuit.

[0012] As described above, the inverter 3 forms an H-bridge type inverter circuit. For example, the switching transistors 15 to 18 of N-type MOS transistors are used as switching elements. A bootstrap circuit configured as described later is connected to the gates of the switching transistors 15 and 16 that output the power on the high potential side.

A voltage Vcc is applied from the power source 1 to the anode of the diode 19. The power sword of the diode 19 is connected to one end of the resistors 21 and 22 and the capacitor 23. The other end of resistor 21 is connected to a diode 20 force sword. The anode of the diode 20 is connected to the connection point between the diode 13 and the capacitor 14 of the high potential power supply unit 4. The other end of the resistor 22 is connected to the gate of the switching transistor 15. A connection point between the resistor 22 and the gate of the switching transistor 15 is connected to the collector of the drive transistor 31. A resistor 35 is connected to the base of the drive transistor 31. The drain of the switching transistor 15 is connected to the connection point of the diode 9 and the capacitor 10 that become the power output section of the DC / DC converter 2. The source of the switching transistor 15 is connected to the other end of the capacitor 23 and the drain of the switching transistor 17. Further, this connection point serves as an AC power output section of the inverter 3 and is connected to one end side of the HID valve 6 through the igniter 5.

The source of the switching transistor 17 is grounded. The gate of the switching transistor 17 is connected to one end of the resistor 29 and the collector of the drive transistor 32. The other end of the resistor 29 is connected to the application terminal of the power source 1 voltage Vcc. One end of a resistor 36 is connected to the base of the drive transistor 32.

A voltage Vcc is applied from the power source 1 to the anode of the diode 24. The power sword of the diode 24 is connected to one end of the resistors 26 and 27 and the capacitor 28. The other end of resistor 26 is connected to a diode 25 force sword. The anode of the diode 25 is It is connected to the connection point between the diode 13 and the capacitor 14. The other end of the resistor 27 is connected to the gate of the switching transistor 16. The connection point between the resistor 27 and the gate of the switching transistor 16 is connected to the collector of the drive transistor 33. A resistor 37 is connected to the base of the drive transistor 33. The drain of the switching transistor 16 is connected to the connection point between the diode 9 and the capacitor 10 of the DC / DC converter 2. The source of the switching transistor 16 is connected to the other end of the capacitor 28 and the drain of the switching transistor 18. Further, this connection point becomes an output part of the inverter 3 and is connected to the other end of the HID valve 6 via the igniter 5.

The source of the switching transistor 18 is grounded. The gate of the switching transistor 18 is connected to one end of the resistor 30 and the collector of the drive transistor 34. The other end of resistor 30 is connected to the voltage Vcc application terminal of power supply 1. One end of a resistor 38 is connected to the base of the drive transistor 34.

[0014] The other end of the resistor 35 and the other end of the resistor 38 are connected, and a drive signal a is input to this connection point from a control means (not shown). Further, the other end of the resistor 36 and the other end of the resistor 37 are connected, and a control means equal force drive signal b (not shown) is input to this connection point. The drive transistors 31 to 34 also have, for example, NPN bipolar transistor power, and the emitters are grounded. The inverter 3 of the discharge lamp lighting device according to the first embodiment is configured as described above, and the high-potential side switching transistor 15 is a boot configured by a diode 19, a resistor 22, a capacitor 23, a transistor 31, and a resistor 35. It is driven by a strap circuit. Similarly, the high potential side switching transistor 16 is driven by a bootstrap circuit including a diode 24, a resistor 27, a capacitor 28, a transistor 33, and a resistor 37.

Next, the operation will be described.

For example, the DCZDC converter 2 supplied with the voltage Vcc of the DC voltage 12 [V] from the power source 1 performs the ONZOFF operation based on the pulse signal input to the transistor switch 8 connected to the primary winding of the transformer 7 from the external force. By repeating, the current flowing in the primary side winding is turned ON and OFF, and the induced electromotive force is generated in the secondary side winding of the transformer 7. The current generated in the secondary winding of transformer 7 is rectified in a fixed direction by diode 9 and Smoothed by the capacitor 10. The DCZDC converter 2 outputs DC power boosted to, for example, 85 V from the connection point between the power sword of the diode 9 and the capacitor 10. The DC power output from the DC / DC converter 2 is input to the inverter 3 and supplied to the drains of the transistors 15 and 16.

[0016] The voltage at which the switching transistor 15 is turned ON by the ONZOFF operation of the drive transistor 31 (hereinafter, each switching transistor 15 to 18 is turned ON) is connected to the gate of the high potential side switching transistor 15 of the inverter 3 Either a gate voltage is described as an ON voltage) or a voltage at which the switching transistor 15 is turned off (hereinafter, a gate voltage at which each switching transistor 15 to 18 is turned off is referred to as an OFF voltage). Is done. The ONZOFF state of the drive transistor 31 is set by a drive signal a input to the base of the drive transistor 31 via the resistor 35. An ON voltage or an OFF voltage is applied to the gate of the high potential side switching transistor 16 by the ONZ OFF operation of the drive transistor 33. The ONZOFF state of the drive transistor 33 is set by the drive signal b input to the base of the drive transistor 33 through the resistor 37.

[0017] The gate voltage of the low potential side switching transistor 17 connected in series to the high potential side switching transistor 15 is the same as the voltage Vcc applied through the resistor 29 by the ON / OFF operation of the drive transistor 32. Set to ON voltage or OFF voltage. The ONZOFF state of the drive transistor 32 is set by a drive signal b input to the base of the drive transistor 32 via the resistor 36. The gate voltage of the low-potential side switching transistor 18 connected in series to the high-potential side switching transistor 16 is the voltage Vcc applied via the resistor 30. Set to. The ONZOFF state of the drive transistor 34 is set by a drive signal a input to the base of the drive transistor 34 via the resistor 38.

In this way, the high potential side switching transistor 15 and the low potential side switching transistor 18 are ONZOFF by the drive signal a, and the high potential side switching transistor 16 and the low potential side switching transistor 17 are ONZOFF by the drive signal b. Operation is controlled, high potential side Switching transistor 15 and low potential 佃 jSwitching transistor 18 is driven to be turned on or off at the same time, and high potential side switching transistor 16 and low potential side switching transistor 17 are turned on or off at the same time. Driven by.

Drive signal a and drive signal b indicate ON state or OFF state alternately, and high-potential side switching transistors 15 and 16 are alternately turned ON or OFF, and each source of switching transistors 15 and 16 The high-potential side load current is alternately output from the low-side switching transistors 17 and 18, and the drains of the switching transistors 17 and 18 are alternately connected to the ground. Power The HID valve 6 is supplied with power.

[0019] When starting to turn on the HID bulb 6, DC power is output from the inverter 3, and a pulse voltage with a high potential of about 400 [V] generated by the igniter 5 is applied to the DC power. Prepare to supply to HID valve 6. After the power supply to the igniter 5 is completed, the inverter 3 continues to output DC power until the discharge phenomenon of the HID valve 6 reaches the state of steady lighting, and continues to supply a DC load current to the HID valve 6. While the DC power is continuously output from the inverter 3, the H-bridge inverter circuit is kept in the ON state with the high-potential side switching transistor and the low-potential switching transistor that are paired with each other. Each switching transistor facing the switching transistor is driven to be kept in the OFF state. This drive control is performed by drive signals a and b. After the HID valve 6 is in a steady lighting state, the inverter 3 periodically switches the direction of the load current and outputs AC power.

FIG. 2A is a circuit diagram showing a part of an H-bridge type inverter circuit of the discharge lamp lighting device according to Embodiment 1. The same reference numerals are used for parts that are the same as or equivalent to those shown in FIG. This figure is a circuit diagram in which a part of the bootstrap circuit connected to the high potential side switching transistor 15 shown in FIG. 1 is extracted.

FIG. 2B is an explanatory diagram showing the operating state of the high-potential side switching transistor and the current flowing through the capacitor of the bootstrap circuit. This figure shows, for example, the current Ic flowing in the capacitor 23 in each ONZOFF state of the high potential side switching transistor 15. It is a thing. When the switching transistor 15 is driven to the ON state, the electrostatic capacity existing between the gate Z and the source of the switching transistor 15 is charged, so that the energy accumulated in the capacitor 23 is absorbed and the capacitor 23 Current Ic flows out sharply. The current Ic flowing out of the capacitor 23 flows in the circuit as shown by the solid line arrow X in FIG. 2A, and when the switching transistor 15 is driven to the ON state, it becomes approximately the gate current of the switching transistor 15.

Further, when the switching transistor 15 is turned off, the current Ic becomes a charging current flowing into the capacitor 23. At this time, a current Ic flows through the circuit as shown by a broken arrow Y in FIG. 2A, and a current supplied from the power source 1 through the diode 19 flows into the capacitor 23 and charging is performed. The capacitor 23 thus supplements the power energy released in the ON state of the switching transistor 15.

The output power of the high potential power supply unit 4 is supplied to the capacitor 23 via the resistor 21 and the diode 20 as shown in FIG. 1 and FIG. 2A. The capacitor 23 is applied to the drain of the switching transistor 15 so that the capacitor 23 is charged even when the switching transistor 15 is turned on and the potential at the connection point between the switching transistor 15 and the capacitor 23 becomes high. Or a source potential of the switching transistor 15, that is, a potential higher than the high potential side of the load power is applied. Further, the high potential as described above is always applied to the capacitor 23 from the high-potential power supply unit 4 while the inverter 3 is operating, and a current limited by the resistor 21 flows. By connecting the diode 20 and the resistor 21 constituting the charging means to the bootstrap circuit that drives the switching transistor 15 in this way, the capacitor 23 is continuously charged, and the voltage force S across the capacitor 23 is prevented from becoming small. Thus, the voltage across the capacitor 23 is maintained at a voltage value that can keep the switching transistor 15 ON.

Therefore, the bootstrap circuit including the capacitor 23 compensates for the current Ic flowing out of the capacitor 23 even after the energy is absorbed by the capacitance between the gate Z source of the switching transistor 15 and the gate of the switching transistor 15. The leakage current and the current consumption of the bootstrap circuit that drives the switching transistor 15 can continue to flow, and the gate voltage of the switching transistor 15 is secured. By supplying high potential power from the high potential power supply unit 4 to the capacitor 23 in this way, the ON time of the switching transistor 15 can be kept long without depending on the capacitance of the capacitor 23, and the drive signal a Thus, the ON state of the switching transistor 15 can be maintained until the ON state force is switched to the OFF state.

Here, the power of the switching transistor 15, the bootstrap circuit connected to the switching transistor 15, the capacitor 23, the diode 20, and the resistor 21 of the circuit are described. The high-potential side switching transistor 16 paired with the switching transistor 15 operates in the same manner, and the bootstrap circuit connected to the switching transistor 16 and the capacitor 28 corresponding to the capacitor 23 operate in the same manner as described above. To do. The diode 24 in the bootstrap circuit that drives the switching transistor 16 corresponds to the diode 19, the resistor 27 corresponds to the resistor 22, the diode 25 corresponds to the diode 20, and the resistor 26 corresponds to the resistor 21. Here, description of the operation of the switching transistor 16, the bootstrap circuit connected thereto, and the capacitor 28 of the circuit is omitted.

In addition, the potential applied from the resistor 21 to the capacitor 23 is charged to the capacitor 23 so that the potential is high as described above. The current flowing from the resistor 21 to the capacitor 23 is the leakage current of the gate of the switching transistor 15. And the current consumed by the bootstrap circuit are equal to or greater than the combined current, the current limited by the resistor 21 is very small. The same applies to the current flowing from the resistor 26 to the capacitor 28. In this way, by suppressing the charging current constantly flowing to the capacitors 23 and 28, the load on the high potential power supply unit 4 and the DCZDC converter 2 is reduced.

[0023] When the discharge lamp is steadily lit, it is only necessary to maintain the ON state of the switching transistors 15 to 18 at 1.25 [m Sec.]. The strap circuit can operate sufficiently, but at the start of lighting, it is necessary to keep the ON state of the switching transistors 15 to 18 longer than that during steady lighting until the discharge phenomenon is stabilized. ] Must remain on for a short time. In order to keep the ON state of the high potential side switching transistors 15 and 16 for a long time, it is necessary to stabilize the gate voltage of the switching transistors 15 and 16 for a long time. In order to prevent the voltage across the capacitors 23 and 28 from becoming small, the capacitor 23 is always connected via the diode 20 and the resistor 21 and the capacitor 28 is connected to the diode 28 while the inverter 3 is operating as described above. Charging is performed through 25 and resistor 26. This operation eliminates the need to increase the capacities of capacitors 23 and 28 in order to keep the high-side switching transistors 15 and 16 on for a long time at the start of lighting. Small and large capacitors 23 and 28 can be used in the bootstrap circuit.

3A and 3B are explanatory diagrams showing a part of the circuit of the discharge lamp lighting device according to Embodiment 1. FIG. The same parts as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. 3A shows a diode 9 and a capacitor 10 connected to the secondary winding of the transformer 7 of the DC / DC converter, and FIG. 3B shows a diode 9 connected to the secondary winding of the transformer 7. , Capacitor 10, capacitor 11, diodes 12, 13 and capacitor 14 constituting the high-potential power supply unit 4.

FIG. 3C is an explanatory diagram showing the current flowing through the diode and the voltage across the diode. This figure shows the change with time of the current ID flowing through the diode 9 and the voltage VD across the diode 9 in the circuit shown in FIG. 3A.

The induced electromotive force generated in the secondary winding of the transformer 7 of the DCZDC converter 2 is rectified by the diode 9, and a current ID as shown in FIG. 3C flows. When this current ID flows, a voltage VD as shown in FIG. When the forward current ID flows through the diode 9, a voltage drop occurs at both ends of the diode 9, and the voltage VD shown in FIG. 3C is generated. When the induced electromotive force generated in the secondary winding of the transformer 7 regenerates energy through the diode 9, that is, when the induced electromotive force is generated so that a reverse current flows through the diode 9, A current ID with a value lower than 0 [A] shown in Fig. 3C flows. This reverse current flows when the direction in which the induced electromotive force is generated changes. As shown in Fig. 3C, the reverse current ID is cut off in diode 9 and converges to 0 [A]. A surge voltage represented as an undershoot portion of a rectangular wave is applied to the VD waveform.

[0025] This surge voltage is generated when, for example, a voltage of 400 [V] is generated. The secondary side winding of the wire may reach about 800 [V]. To prevent diode 9 from being damaged by surge voltage, diode 9 must have a high withstand voltage rating.

In the discharge lamp lighting device according to Embodiment 1, as shown in FIG. 3B, the capacitor 11 is connected to the connection point between the secondary winding of the transformer 7 and the anode of the diode 9, and a reverse current is passed through the diode 9. In this way, the energy generated in the secondary winding of the transformer 7, that is, the surge voltage is absorbed by the capacitor 11 via the diode 12. The energy stored in the capacitor 11 is used for the operation of the high potential power supply unit 4. By allowing the capacitor 11 to absorb the surge voltage, a diode element having a low withstand voltage rating can be used as the diode 9 and the cost can be reduced.

[0026] The high-potential power supply unit 4 shown in FIG. 1 inputs and boosts the output voltage of the DCZDC converter 2. The high-potential power supply unit 4 also receives the power of the power sword force of the diode 9 and outputs a potential obtained by adding the potential generated by the energy accumulated in the capacitor 14 to the potential of the power sword of the diode 9. Thus, the output potential of the high potential power supply unit 4 becomes higher than the potential of the power sword of the diode 9, that is, the potential applied to the high potential side switching transistors 15 and 16 of the H bridge type inverter 3. The energy of the surge voltage accumulated in the capacitor 11 is such that after a current flows from the diode 9 to the diode 12, a current flows from the diode 12 to the diode 13, and the voltage across the capacitor 14 becomes the force sword potential of the diode 9, that is, DCZDC. The inverter 3 can be efficiently operated by the high-potential power supply unit 4 that is used when added to the output voltage of the converter 2 and is simply configured.

As described above, according to the first embodiment, the capacitors 23 and 28 of the bootstrap circuit that drives the high-potential side switching transistors 15 and 16 are constantly charged with the high-potential power supply unit 4 and the diodes 20 and 20. 25, resistors 21 and 26 are provided, so that the high-side switching transistors 15 and 16 are kept on for a long time even when the small-capacitance capacitors 23 and 28 adapted for steady lighting are used in the bootstrap circuit. Therefore, DC load power can be supplied for a long time from the inverter 3 when the discharge lamp starts lighting. In addition, since the inverter 3 can be configured without using a large-capacitance capacitor, the inverter 3 can be reduced in size and cost can be reduced. [0028] Embodiment 2.

FIG. 4 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 2 of the present invention. The same reference numerals are used for parts that are the same as or equivalent to those shown in FIG. 1, and descriptions thereof are omitted. The discharge lamp lighting device according to the second embodiment is provided with a DCZDC converter (charging means, booster circuit) 40 instead of the four high-potential power supply units shown in FIG. 1, and other configurations are the same as those of the first embodiment. The discharge lamp lighting device described above is the same. Here, the description of the parts configured in the same manner as the discharge lamp lighting device of Embodiment 1 is omitted. The discharge lamp lighting device shown in FIG. 4 includes a DCZDC converter 40 that can obtain an output potential higher than the output potential of the DCZDC converter 2, and supplies the output power of the DCZDC converter 40 to the anodes of the diodes 20 and 25. It is configured. The DCZDC converter 40 illustrated in FIG. 4 is used to input the output voltage Vcc of the power source 1. The DCZDC converter 40 can be any type as long as it outputs a higher potential than the DCZDC converter 2. The power supply for supplying power to the DCZDC converter 40 is not limited to the power supply 1 shown in the figure, and the input voltage is not limited to the voltage Vcc.

Next, the operation will be described.

The discharge lamp lighting device according to the second embodiment operates in the same manner as described in the first embodiment except that the potential output from the DCZDC converter 40 is applied to the capacitors 23 and 28. The description is omitted. The potential output from the DCZDC converter 40 is the same as that output from the high potential power supply unit 4 shown in FIG. 1, and the switching transistor 15 shown in FIG. The potential applied to the drain of the switching transistor 15 or the source potential of the switching transistor 15, i.e., the high potential of the load power, so that the charging current flows through the capacitor 23 even when the potential at the connection point to 23 is high. A higher potential is applied than the side. Similarly, the capacitor 28 connected to the switching transistor 16 has a potential higher than the potential applied to the drain of the switching transistor 16 so that the charging current flows even when the switching transistor 16 is turned on. Applied by DC / DC converter 40. The capacitor 23 shown in FIG. 4 is connected via a diode 20 and a resistor 21. The capacitor 28 is applied with a high potential from the DCZDC converter 40 via the diode 25 and the resistor 26. The operational effects of the diodes 20 and 25 and the resistors 21 and 26 shown in FIG. 4 are the same as those described in the first embodiment with reference to FIG.

As described above, according to the second embodiment, the DCZDC converter 40, the diode 20, and the capacitor 20, 23 of the bootstrap circuit that drives the high potential side switching transistors 15, 16 are always charged. 25 and resistors 21 and 26 enable the switching transistors 15 and 16 to be kept on for a long time even when the small-capacitance capacitors 23 and 28 adapted for steady lighting are used in the bootstrap circuit. In addition, DC load power can be supplied for a long time from the inverter 3 when the discharge lamp starts to light.

In addition, since the inverter 3 can be configured without using a large-capacitance capacitor, the inverter 3 can be reduced in size and the cost can be reduced.

[0031] Embodiment 3.

FIG. 5 is a circuit diagram showing a schematic configuration of a discharge lamp lighting device according to Embodiment 3 of the present invention. The same reference numerals are used for parts that are the same as or equivalent to those shown in FIGS. FIG. 5 is a circuit diagram of a part of the discharge lamp lighting device according to the third embodiment, and shows a part of an H-bridge type inverter circuit using IC46. The DC / DC converter 2a shown in FIG. 5 corresponds to the DC / DC converter 2 in FIG. 1, and boosts the voltage input from the power source 1. The DCZDC converter 40a shown in FIG. 5 corresponds to the DCZDC converter 40 shown in FIG. 4. For example, the power of the power source 1 is input and a voltage higher than the output voltage of the DCZDC converter 2a is output. The control power supply unit la that inputs power from the power supply 1 controls and supplies power to the bootstrap circuit, and outputs, for example, power of DC voltage 12 [V].

[0032] IC 46 is an integrated circuit (hereinafter referred to as IC) in which a bootstrap circuit that drives a switching transistor of an H-bridge inverter circuit is integrated. For example, the resistors 22, 29, switching transistors 31, and 31 shown in FIG. The circuit elements corresponding to 32 and resistors 35 and 36 are connected and configured as in the circuit of FIG. The IC 46 includes a terminal for connecting the diode 41 and the capacitor 44 as illustrated in FIG. 5, for example. By connecting both ends of 41 and one end of the capacitor 44, a bootstrap circuit for driving the high potential side switching transistor as described in the first embodiment is configured. Further, the IC 46 includes terminals for inputting the drive signal a and the drive signal b described above. The output terminal of the IC 46 is connected to the gates of the high potential side switching transistor 15a and the low potential side switching transistor 17a.

[0033] The anode of the diode 41 connected to the terminal of the IC 46 is connected to the control power supply unit la, the force sword of the diode 41 is connected to the terminal of the IC 46, and one end of the capacitor 44 is connected. In addition, one end of a resistor (charging means, current limiting means) 43 and a force sword of a Zener diode (voltage limiting element) 45 are connected to this connection point. The other end of the resistor 43 is connected to a power sword of a diode (charging means) 42, and the anode of the diode 42 is connected to a DCZDC converter 40a. The Zener diode 52 has a Zener voltage with a rating of, for example, 12 [V] to 20 [V]. The diode 42 corresponds to the diode 20 or the like, and the resistor 43 corresponds to the resistor 21 or the like.

[0034] The switching transistor 15a shown in FIG. 5 corresponds to the switching transistor 15 shown in FIG. 1 and the like, and the switching transistor 17a in FIG. 5 corresponds to the switching transistor 17 in FIG. . The high-potential side switching transistor 15a and the low-potential side switching transistor 17a are connected in series, and the connection point between the source of the switching transistor 15a and the drain of the switching transistor 17a is the output section of the H-bridge inverter circuit. The other end of the capacitor 44 and the anode of the Zener diode 45 are connected to this connection point. The output power of the DCZDC converter 2a is supplied to the drain of the switching transistor 15a, and the source of the switching transistor 17a is grounded. Further, the discharge lamp lighting device according to Embodiment 3 includes a high-potential side switching transistor and a low-potential side transistor, both of which are not shown in the figure, together with the high-potential side switching transistor 15a and the low-potential side switching transistor 17a constituting the H-bridge inverter circuit. In addition, a bootstrap circuit with an IC (not shown) that drives these switching transistors and a diode, a capacitor, a resistor, and the like constituting the bootstrap circuit are configured in the same manner as described above. Yes. Here, the description of these similarly configured parts is omitted. Next, the operation will be described.

The discharge lamp lighting device according to the third embodiment operates in the same manner as that described in the first embodiment and the like except that it is provided with the corner diode 45 shown in FIG. Description of operations similar to those described in Embodiment 1 will be omitted, and operations that characterize the discharge lamp lighting device according to Embodiment 3 will be described.

The discharge lamp lighting device shown in Fig. 5 is driven by an IC46 in which switching transistors on the high potential side and low potential side of the H-bridge inverter circuit are stacked. Generally, the withstand voltage of an IC or the gate withstand voltage of a MOS transistor used for a switching transistor is about 20 [V], and if a voltage higher than that is applied, it may be destroyed. A high potential similar to the potential output from the high potential power supply unit 4 described in the first embodiment is always applied to the capacitor 44 from the DC / DC comparator 40a via the diode 42 and the resistor 43, and the capacitor 44 is charged. If the current continues to flow, the voltage across capacitor 44 may exceed the withstand voltage of IC46. If the voltage across the capacitor 44 exceeds 20 [V], for example, and this voltage is applied to the IC 46, etc., each element constituting the H-bridge inverter circuit will be destroyed. In order to prevent such destruction, a Zener diode 45 is connected in parallel with the capacitor 44, and the voltage across the capacitor 44 is changed from 12 [V] to 20 [V] as described above using the Zener effect. Limit the voltage so that it is not greater than any other voltage. If the Zener voltage is lower than 12 [V] and the Zener diode 45 is provided, almost all of the current supplied from the control power supply unit la flows to the Zener diode 45, and each circuit cannot operate. . Therefore, a Zener diode 45 whose rating of the Zener voltage is higher than the output voltage of the control power supply unit la and is equal to or lower than the withstand voltage of the IC 46 or the like is used.

As described above, according to the third embodiment, the Zener diode that limits the voltage across the capacitor 44 of the bootstrap circuit so as not to exceed the withstand voltage of each element constituting the H-bridge inverter circuit 45 Therefore, it is possible to construct a circuit using an IC or the like having a relatively low withstand voltage.

In addition, the cost of the H-bridge inverter circuit can be reduced by using an IC or the like. Industrial applicability

As described above, the discharge lamp lighting device according to the present invention is suitable for outputting DC power for a long time at the start of lighting of the discharge lamp without using a large capacity capacitor.

Claims

The scope of the claims

[1] A discharge lamp lighting comprising: a converter circuit that generates electric power to be supplied to the discharge lamp; and an H-bridge inverter circuit that outputs load power to the discharge lamp using the electric power output from the converter circuit In the device

A capacitor of a bootstrap circuit as a power supply for securing a gate voltage of a high-potential side switching element constituting the H-bridge inverter circuit;

A discharge lamp lighting device comprising: charging means for supplying a charging current to the capacitor at a potential higher than a high potential side of the H-bridge inverter circuit.

[2] The charging means includes current limiting means for limiting the charging current to a magnitude that maintains the voltage across the capacitor of the bootstrap circuit when the switching element is driven to the ON state. The discharge lamp lighting device according to 1.

3. The discharge lamp lighting device according to claim 1, wherein the charging means is a booster circuit that boosts the output voltage of the converter circuit.

[4] The charging means includes a capacitor that absorbs a surge voltage generated when the converter circuit generates electric power to be supplied to the discharge lamp and uses the absorbed energy for the charging current. The discharge lamp lighting device according to 1.

5. The discharge lamp lighting device according to claim 1, wherein the charging means is a booster circuit that boosts the voltage of the power supply of the converter circuit.

[6] The discharge lamp lighting according to claim 1, wherein the bootstrap circuit includes a voltage limiting element that limits a voltage across the capacitor of the bootstrap circuit to a withstand voltage of each element constituting the circuit or less. apparatus.