JP2001043990A - Discharge lamp device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a semiconductor switching element constituting an inverter circuit from being broken by a surge voltage. SOLUTION: The output terminals of bridge driving circuits 62, 63 are connected to the gate terminals of MOS transistors 61a-61d of an H bridge circuit 61 through resistors 643, 647, 653, 657, and the output terminal of at least one of four driving circuits 621, 622, 631, 632 is connected to wiring which is used as a negative electrode side reference potential through capacitors 645, 648, 655, 658. By such a structure, an integrating circuit composed of the resistors and capacitors serves as a filter, so that the application of a high voltage to the driving circuit part can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp device for lighting a high-pressure discharge lamp, and is particularly suitable for use in a vehicle headlamp.

[0002]

2. Description of the Related Art Conventionally, a high-pressure discharge lamp (hereinafter, referred to as a lamp) is applied to a vehicle headlamp, the voltage of a vehicle-mounted battery is increased by a transformer, and the polarity of the high voltage is determined by an inverter circuit. There have been proposed various lamps for switching the lamp so that the lamp is turned on by alternating current (JP-A-9-180).
888, JP-A-8-321389, etc.).

[0003] An H-bridge circuit composed of a switching element (for example, a MOS transistor) is used in the inverter circuit, and AC lighting is performed by forming a rectangular wave by the H-bridge circuit.

[0004]

A discharge lamp device includes a high voltage pulse generating circuit for applying a high voltage pulse to a lamp at the start of lighting to cause dielectric breakdown between the electrodes of the lamp to start lighting of the discharge lamp. Is provided.

Since this high-voltage pulse generation circuit is a source of magnetic noise, conventionally, this high-voltage pulse generation circuit is housed in a metal case (envelope) separate from other circuits (such as the inverter circuit). I was trying to do it.

However, since the cost is increased if the metal case is separately provided, the present inventors have studied to house the high-voltage pulse generating circuit in the same case as other circuits.

When the high-voltage pulse generating circuit and the other circuits are housed in the same case, there is a problem that the elements of the inverter circuit are destroyed. this is,
This occurs as follows. First, since the high-voltage pulse generation circuit and the inverter circuit are close to each other, there is a distributed capacitance between the high-voltage part and other potential parts, and the leakage magnetic flux generated by the high-voltage pulse generation circuit Is linked to another circuit, and a voltage is induced in a circuit portion where the magnetic flux links. Also, since the wiring wire for applying the high voltage pulse to the lamp is drawn out of the case,
Although the wiring wire is covered with the earth shield, a distributed capacitance is formed between the wiring wire and the earth shield.

When the lamp is broken down after these distributed capacitors are charged by the high-voltage pulse, the electric charges charged in the distributed capacitor are discharged through the lamp, and the discharge current caused by this is discharged as a surge current through the wiring wire. Flows into the circuit inside the case. For this reason, a surge voltage is generated by the current path impedance. In addition, the leakage magnetic flux generated when the high-voltage pulse is generated is linked to another circuit, and a surge voltage is induced in the linked circuit portion.

When the surge voltage exceeds the withstand voltage of the semiconductor switching element used in the H-bridge circuit or the bridge drive circuit included in the inverter circuit,
The semiconductor switching element is destroyed. In particular, since the withstand voltage of the semiconductor switching element varies, when an element having a low withstand voltage is incorporated in the inverter circuit, the element is easily broken.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. In a case where a high-voltage pulse generating circuit and an inverter circuit are housed in the same case (envelope), the surge voltage caused by the high-voltage pulse generating circuit causes An object of the present invention is to prevent a semiconductor switching element included in a circuit from being destroyed.

[0011]

In order to achieve the above object, according to the present invention, the bridge drive circuit (62, 63) includes four semiconductor switching elements (61a to 61d) respectively. Has four drive circuit units (621, 622, 631, 632) for driving
Output terminals (Ho terminal, Lo terminal) of these four drive circuit units are connected to respective gate terminals of the four semiconductor switching elements, and the four terminals are determined based on a potential difference between the output terminals and the negative reference potential of each drive circuit unit. Each of the two semiconductor switching elements is driven, and the output terminal of the bridge driving circuit and the gate terminal of the semiconductor switching element of the H-bridge circuit (61) are connected to the first resistor (643, 647, 6).
53, 657), and at least one of the four drive circuit units has a first capacitor (645, 648, 65) between the output terminal and the wiring serving as the negative reference potential.
5, 658).

With such a configuration, the integration circuit including the first resistor and the first capacitor functions as a filter, thereby preventing a high voltage from being applied to the drive circuit.

According to the second aspect of the present invention, the bridge drive circuit includes two MOS transistors (623-626, 633-636) directly connected to each other so as to correspond to each of the four semiconductor switching elements. The four semiconductor switching elements are driven based on the potential of each connection point of the two MOS transistors connected in series, and the output terminals (Ho terminal, Lo terminal) of the bridge drive circuit are provided. Terminal) and the gate terminals of the semiconductor switch elements (61a to 61d) of the H-bridge circuit are connected via first resistors (643, 647, 653, 657), and the series-connected M of the bridge drive circuit is connected.
At least one of the four sets of OS transistors has a first capacitor (645, 64) between the drain and source of the low-side MOS transistor connected in series.
8, 655, 658).

As described above, two MOSs connected in series
When the semiconductor switching element of the H-bridge is driven by using the potential of the connection point of the transistor, a high voltage is prevented from being applied to the MOS transistor of the bridge drive circuit by the integration circuit including the first resistor and the first capacitor. can do. Thereby, the MOS transistor of the bridge drive circuit can be prevented from being destroyed.

For example, the capacitance of the first capacitor and the capacitance of the first capacitor are set so that the time constant determined by the capacitance C of the first capacitor and the resistance value R of the first resistor is 0.2 microsecond or more. Set the resistance value of one resistor.

According to the present invention, the MOS capacitor C of the semiconductor switching element and the resistance value R of the first resistor are provided.
M so that the time constant determined by
It is characterized in that the OS capacitance and the resistance value of the first resistor are set.

If the time constant determined by the MOS capacitance and the resistance is set to 0.2 microseconds or more, the voltage applied to the semiconductor switching element in the H-bridge circuit can be made equal to or less than the withstand voltage of the element. Therefore, the element can be prevented from being destroyed.

According to the fifth aspect of the present invention, the output terminals of the bridge drive circuit (62, 63) and the gate terminals of the semiconductor switch elements (61a to 61d) of the H-bridge circuit (61) are resistors (643, 647). , 653, 657)
And the resistance value of the MOS capacitor and the first resistor is set such that the time constant determined by the MOS capacitor C of the semiconductor switching element and the resistance value R of the first resistor is 0.2 microsecond or more. It is characterized by:

With this configuration, an integrating circuit is formed by the first resistor and the MOS capacitor, and it is possible to prevent a high voltage from being applied to the semiconductor switching element in the H-bridge circuit. This can prevent the semiconductor switching element from being destroyed.

According to the present invention, the terminal (VS terminal) serving as the negative reference voltage is connected to the H bridge circuit (6).
1) In at least one of the two bridge drive circuits (621, 631) connected to the midpoint potential point (X, Y), a terminal serving as the midpoint potential point of the H-bridge circuit and the negative reference potential. Are connected via resistors (644, 654), and the ground potential point is connected between the resistor and the terminal serving as the negative-side reference potential and the second capacitor (649, 654).
659).

With such a configuration, an integrating circuit is formed by the resistor and the second capacitor, and the surge is generated through the wiring connecting the terminal serving as the negative-side reference potential of the drive circuit section and the midpoint potential point of the H-bridge circuit. The current can be suppressed from flowing. Thus, it is possible to prevent a high voltage from being applied to the bridge drive circuit through the midpoint potential point of the H-bridge circuit and the bridge drive circuit from being destroyed.

For example, the resistance value of the resistor and the capacitance of the capacitor are set so that the time constant determined by the resistance value R of the resistor and the capacitance C of the capacitor is 0.01 microsecond or more. Is set.

The reference numerals in the parentheses indicate the correspondence with the specific means described in the embodiment described later.

[0024]

FIG. 1 shows an entire configuration of an embodiment in which a discharge lamp device according to the present invention is applied to a vehicle headlamp.

The discharge lamp device is connected to a vehicle-mounted battery 1 which is a DC power supply. When the lighting switch 3 is turned on, a lamp used as a vehicle headlight (for example,
A power is supplied to a metal halide lamp 2). This discharge lamp device includes a DC-DC converter 4 as a DC power supply circuit, a lighting auxiliary circuit 5, an inverter circuit 6, a high voltage generation circuit 7, and other circuit functional units.

The DC / DC converter 4 is connected to a flyback transformer 41 having a primary winding 41a disposed on the battery 1 side and a secondary winding 41b disposed on the lamp 2 side, and the primary winding 41a. It comprises a MOS transistor 42, a rectifying diode 43 and a smoothing capacitor 44 connected to the secondary winding 41b.
A boosted voltage obtained by boosting B is output. That is, when the MOS transistor 42 is turned on, a primary current flows through the primary winding 41a and energy is stored in the primary winding 41a.
When the OS transistor 42 is turned off, the energy of the primary winding 41a is supplied to the secondary winding 41b. By repeating such an operation, a high voltage is output from the connection point between the diode 43 and the smoothing capacitor 44.

The flyback transformer 41 is configured such that the primary winding 41a and the secondary winding 41b are electrically connected as shown in the drawing.

The lighting auxiliary circuit 5 is composed of a capacitor 51 and a resistor 52, and the capacitor 51 is charged after the lighting switch 3 is turned on, so that the lamp 2 immediately shifts from dielectric breakdown between the electrodes to arc discharge. Let it.

The inverter circuit 6 illuminates the lamp 2 with alternating current, and comprises an H-bridge circuit 61 and bridge drive circuits 62 and 63. H bridge circuit 61
Are composed of MOS transistors 61a to 61d serving as switching elements arranged in an H-bridge shape. The bridge drive circuits 62 and 63 include an H-bridge control circuit 4 described later.
00, the MOS transistor 61
a, 61d and the MOS transistors 61b, 61c are alternately turned on and off. As a result, the direction of the discharge current of the lamp 2 is alternately switched, the polarity of the applied voltage (discharge voltage) of the lamp 2 is inverted, and the lamp 2 is turned on by AC.

The capacitors 61e and 61f are protection capacitors for protecting the H-bridge circuit 61 from high-voltage pulses generated at the start of lighting.

The high voltage generating circuit 7 includes an H bridge circuit 61
A transformer 71 having a primary winding 71a and a secondary winding 71b, a diode 72, a resistor 74, and a capacitor 7 are provided between the midpoint potential points X and Y and the negative terminal of the battery 1.
5, and a thyristor 76, which is a unidirectional semiconductor element, and starts lighting of the lamp 2. That is, when the lighting switch 3 is turned on, the capacitor 75 starts charging. Thereafter, when the thyristor 76 is turned on, the capacitor 75 starts discharging.
A high voltage is applied to the lamp 2. As a result, lamp 2
Lights due to dielectric breakdown between electrodes.

The MOS transistor 42, the bridge driving circuits 62 and 63, and the thyristor 76 include the control circuit 1
Controlled by 0. This control circuit 10 includes a DC-
A lamp voltage VL between the DC converter 4 and the inverter circuit 6 (that is, a voltage applied to the inverter circuit 6) VL, a lamp current IL flowing from the inverter circuit 6 to the negative electrode side of the battery 1, and the like are input. The lamp current IL is detected as a voltage by the current detection resistor 8.

FIG. 2 shows a block configuration of the control circuit 10. The control circuit 10 sets the MOS transistor 42 to PWM
A PWM control circuit 100 that is turned on and off by a signal;
A sample and hold circuit 200 for sampling and holding the lamp voltage VL;
A lamp power control circuit 300 for controlling the lamp power to a desired value based on L and the lamp current IL, an H-bridge control circuit 400 for controlling the H-bridge circuit 61, and a thyristor 76 turned on to generate a high voltage in the lamp 2 And a high-voltage generation control circuit 500.

In the above configuration, the lighting operation of the discharge lamp device will be described.

When the lighting switch 3 is turned on, power is supplied to each unit shown in FIG. Then, the PWM control circuit 10
0 performs PWM control on the MOS transistor 42. As a result, a voltage obtained by boosting the battery voltage VB by the operation of the flyback transformer 41 is output from the DC-DC converter 4. Also, the H-bridge control circuit 400
MOS transistors 61a-61 in the bridge circuit 61
61d is turned on and off alternately in a diagonal relationship. As a result, the high voltage output from the DC-DC converter 4 is supplied to the capacitor 75 of the high-voltage pulse generation circuit 7 via the H-bridge circuit 61, and the capacitor 75 is charged.

Thereafter, the high voltage generation control circuit 500
A gate drive signal is output to thyristor 76 based on a signal output from bridge control circuit 400 to notify the switching timing of MOS transistors 61a to 61d, and thyristor 76 is turned on. When the thyristor 76 is turned on, the capacitor 75 is discharged, and a high voltage is applied to the lamp 2 through the transformer 71. As a result, the lamp 2 is broken down between the electrodes, and the lighting is started.

Thereafter, the polarity of the discharge voltage to the lamp 2 (direction of the discharge current) is alternately switched by the H-bridge circuit 61, so that the lamp 2 is turned on by AC. Further, the lamp power control circuit 300 controls the lamp power to a desired value based on the lamp current IL and the lamp voltage VL (sampled and held by the sample and hold circuit 200), and stably turns on the lamp 2. Let it.

Note that the sample and hold circuit 200
In synchronization with the switching timing of the bridge circuit 61, the transient voltage generated at the time of the switching is masked, and the ramp voltage VL other than when the transient voltage is generated is sampled and held.

Next, an assembly structure of the discharge lamp device having the above configuration is shown in FIG. 3, and an assembly structure of the discharge lamp device will be described with reference to FIG.

In the discharge lamp device, the bus bar case 20 in which the above-described circuit configuration is arranged is provided by a cover member 21 and a base 22.
And a cover member 21 and a base 22 constituting a case of the discharge lamp device are fixed by screws 23.

On the surface of the bus bar case 20, terminals 24 for electrically connecting the components of the above-described circuit configuration are formed by insert.

In the above circuit configuration, the H bridge circuit 6
1. The control circuit 10, MOS transistor 42, diodes 43 and 72, resistors 8, 52 and 74, which can be formed as semiconductor devices, are hybrid ICs (hereinafter referred to as HI).
(Referred to as C) 101 is formed as an integrated IC.
Then, the other parts (in this circuit configuration, the transformer 4
1, 71, capacitors 44, 75, and thyristor 7
6) is configured separately from the HIC101.

For this reason, the above-mentioned circuit configuration is constituted by electrically connecting the HIC 101 and other parts at the terminal 24. Thus, the circuit function unit shown in FIG. 1 is configured.

The terminal 24 is connected to the output line 2 provided in a grommet fixed to the bus bar case 20.
5 and 26, and to the lamp 2 via the output lines 25 and 26.

The terminal 24 has a terminal (+ terminal) 27a connected to the positive electrode side of the battery 1 and a terminal (-terminal) 27b connected to the negative electrode side (that is, the ground side). 27b is connected to a ground connection portion 27c for grounding the discharge lamp device. The terminals 27 a and 27 b of the terminal 24 are drawn out of the bus bar case 20 through a connector 28 formed in the bus bar case 20, and are connected to the wiring connected to the battery 1 at the connector 28.

The screw 23 is connected to the ground connection 2
At 7c, the bus bar case 20 and the base 22 are screwed and fixed, and the ground connection portion 27c and the base 22 are grounded.

As described above, in the discharge lamp device according to the present embodiment, the same case (the cover member 21 and the base 2) is used.
2) accommodates the high-voltage pulse generating circuit 7 and the inverter circuit 6. The cover 21 and the base 2
Numeral 2 is made of metal in order to protect the circuit function unit housed therein from radiation noise.

FIG. 4 shows details of the inverter circuit 6, and the inverter circuit 6 will be described.

The inverter circuit 6 has the H-bridge circuit 61 constituted by the four MOS transistors 61a to 61d as described above. The inverter circuit 6 includes a bridge drive circuit 62 that outputs control signals for the MOS transistors 61a and 61b, a bridge drive circuit 63 that outputs control signals for the MOS transistors 61c and 61d, capacitors 640, 642, 645, and 648,
649, 652, 655, 658, 659, diodes 641, 646, 651, 656, and resistors 643, 6
44, 647, 653, 654, 657.
Reference numerals 65 and 66 are power supply terminals connected to a common power supply (not shown).

The bridge drive circuit 62 includes a high and low driver circuit (International Rec)
IR2101) manufactured by Tifier Inc. is used. This bridge drive circuit 62 has H
In terminal and Lin terminal, Ho terminal and Lo terminal both constituting output terminals, VS terminal and C
OM terminal, Vcc terminal to which a predetermined power supply is connected, and VB
Terminal.

The bridge drive circuit 62 includes a high-side circuit 621 and a low-side circuit 622 constituting two drive circuit units, and MOS transistors 623 to 626 which are turned on / off by receiving signals from these circuits.
have. The Hin terminal and the Lin terminal are connected to the low-side circuit 622, and the Hin terminal and the Lin terminal are connected to terminals C and E, respectively, which are connected to the control circuit 10 (see FIG. 1). When a control signal from the H-bridge control circuit 400 (see FIG. 2) is input via these terminals C and E, the low-side circuit 622 shapes the waveform of the control signal and serializes the waveform-shaped signal. Connected MOS transistor 62
5 and 626 as drive signals, and transmitted to the high-side circuit 621. The connection point between the MOS transistors 625 and 626 is set as a Lo terminal (output terminal), and this terminal potential is output as a control signal for turning on and off the MOS transistor 61b.

On the other hand, the high side circuit 621 receives a transmission signal from the low side circuit 622 and outputs a drive signal for the MOS transistors 623 and 624 connected in series. The connection point of the MOS transistors 623 and 624 is set to the Ho terminal (output terminal), and this terminal potential is set to M
The control signal is output as a control signal for turning on / off the OS transistor 61a.

The configuration of the bridge drive circuit 63 is exactly the same as that of the bridge circuit 62, but the low-side circuit 632
Terminal and the terminal E, and the Lin terminal and the terminal C are connected to each other.
It is the opposite of 2. Therefore, the low-side circuit 6
22 and the high-side circuit 631 output the same signal, and the high-side circuit 621 and the low-side circuit 632
Output the same signal.

The four drive circuit units shown here (the high side circuits 621 and 631 and the low side circuit 622,
632, and MOS transistors 623-626, 63
3 to 636) use the wiring to which the sources of the low-side MOS transistors 624, 626, 634, and 636 included therein as a negative-side reference potential and determine the potential difference between each output terminal and each negative-side reference potential. Based on the H-bridge circuit 61
Of each of the MOS transistors 61a to 61d. In the bridge drive circuits 62 and 63, V
The S terminal is set to the negative reference potential of the high-side circuits 621 and 631, and the COM terminal is set to the low-side circuits 622 and 632.
32, which is the negative-side reference potential.

When the MOS transistor 61b is turned on, the diode 641, the capacitor 642, and the resistor 64
4. The charging current of the bootstrap capacitor 642 flows through the MOS transistor 61b and the resistor 8, and the bootstrap capacitor 642 is charged. The electric charge charged in the capacitor 642 is used as a power supply for the high-side circuit 621.

The inverter circuit 6 includes a resistor 643,
647, 653, 657 and capacitors 645, 648,
655 and 658 are provided. Resistance 643, 647, 6
53 and 657 are bridge drive circuits 62 and 63, respectively.
Terminal and each MOS transistor 61a
, And the control signals of the high-side circuits 621 and 631 and the low-side circuits 622 and 632 are transmitted through these resistors.
a to 61d.

Each of the capacitors 645, 648, 65
5 and 658 are MOS transistors 6 connected in series.
23 to 626, 633 to 636 are connected between the sources and drains of the low-side MOS transistors 624, 626, 634, 636. These capacitors and the resistors 643, 647, 653, 657 form an integrating circuit. With such a circuit configuration, the capacitors 645, 648, 655, and 658 serve as protection capacitors for absorbing surge.

Further, the midpoint potential points X and Y of the H bridge circuit 61 (that is, the connection point between the MOS transistor 61a and the MOS transistor 61b and the connection point between the MOS transistor 61c and the MOS transistor 61d) and each bridge drive circuit 62 , 63 between the VS terminal and the resistor 64
4, 654. The VS terminal and the COM terminal of each of the bridge drive circuits 62 and 63 are connected via capacitors 649 and 659. Thereby, the resistors 644 and 654 and the capacitors 649 and 6
At 59, an integrating circuit is formed. With such a circuit configuration, the capacitors 649 and 659 serve as protection capacitors for absorbing surge.

The inverter circuit 6 configured as described above
Is an H-bridge control circuit 4 sent via terminals C and E
00 based on the control signal from the high-side circuit 62
1, 631 and the low-side circuits 622, 632 output control signals, and the MOS transistors 61a to 61d
Are turned on and off alternately in a diagonal relationship.

Next, the influence of the surge current generated at the time of the high voltage pulse for starting the lighting of the lamp 2 in the inverter circuit 6 configured as described above will be described.

When the lighting switch 3 is turned on, each circuit operates and the capacitor 75 starts charging. Thereafter, when the thyristor 76 is turned on, the capacitor 75
Discharge occurs through the primary winding 71a. At this time, a high voltage pulse is generated at both ends of the secondary winding 71b, and this high voltage pulse is applied to the lamp 2. Thereby, the lamp 2
Breakdown (spark discharge) occurs between the electrodes, and the lamp 2 is turned on.

Before this lighting, since the high voltage pulse generating circuit and the inverter circuit are in close proximity, a distributed capacitance is formed between the high voltage portion and the other potential portions. A distributed capacitance is also formed between the electric wiring L1 and the earth shield covering the electric wiring L1. Then, the charges charged in these distributed capacitors are discharged through the lamp 2 due to the dielectric breakdown of the lamp 2 due to the high voltage pulse.

The discharge current of this distributed capacity is supplied as a surge current to the H-bridge circuit 6 via the lamp 2 and the electric wiring L2.
Flow into 1. This surge current has a damped oscillation waveform of several tens of MHz, and the peak current value is a current of several tens to 200 A depending on the breakdown voltage of the lamp 2 and the distribution capacity. This surge current flows through a path passing through any part of the circuit function part to the ground. At this time, since a path through which the surge current flows to the ground has some impedance, a surge voltage is generated in the surge current path due to a voltage drop due to the impedance. Since the surge current generated in this way is a high-frequency current, it is difficult to specify a surge current path. In practice, the surge current is shunted and flows everywhere. For example, the electric wiring L2
→ Each MOS transistor 61a of the H bridge circuit 61
A current flows through a path in the order of 61d → bridge drive circuit 62.

The capacitor 61 is connected to the H-bridge circuit.
By providing e and 61f, most of the surge current returns to the high voltage pulse generation circuit 7 and the distributed capacitance,
Although the generation of surge voltage is suppressed, all surge voltages cannot be suppressed. That is, when the surge current returns through the capacitors 61e and 61f, a surge voltage is generated at both ends of the capacitors 61e and 61f by charging and discharging by the surge current. For example, when a high voltage pulse is generated to turn on the lamp 2, a voltage of about 400 V is applied to the lamp 2. At this time, the H-bridge circuit 61 turns on the MOS transistors 61a and 61d.
Since the MOS transistors 61b and 61c are controlled to be turned off, a surge current occurs when a voltage of 400 V is applied to both ends of the capacitor 61e. Therefore, the surge voltage generated at both ends of the capacitor 61e is a voltage that oscillates positively and negatively with respect to 400V. Then, this surge voltage is applied to the H-bridge midpoint potential point X, and a surge current flows into the Ho terminal or Lo terminal of each of the bridge drive circuits 62 and 63 via the MOS transistors 61a to 61d, or a surge current flows into the VS terminal. Flows into it.

When a high voltage pulse is generated, the transformer 71
When the leakage flux is linked to another circuit, a surge voltage is induced in the linked circuit. For example, the gate drive circuit of the MOS transistor 61b is M
Gate-source of OS transistor 61b, resistance 8, M
Source-drain of OS transistor 626, resistor 64
A loop circuit is formed through the loop 7, and a surge voltage is induced in the loop in which the leakage magnetic flux is linked.
The induced voltage is, for example, the MOS transistor 61
A surge voltage is applied between the gate and the source of b.

On the other hand, in the present embodiment, each gate terminal of the MOS transistors 61a-61b of the H-bridge circuit 61 and each output terminal of the bridge drive circuits 62, 63 for driving the MOS transistors 61a-61d are connected to the resistor 6
43, 647, 653, and 657, the MOS transistors 61a to 61
It is possible to suppress a surge current flowing into the Ho terminal and the Lo terminal of the bridge drive circuits 62 and 63 via the line d. A resistor 64 is connected between the midpoint potential points X and Y of the H bridge circuit 61 and the VS terminals of the bridge drive circuits 62 and 63.
4 and 654, surge current flowing into the VS terminals of the bridge drive circuits 62 and 63 can be suppressed.

Further, in the present embodiment, the MOS transistor 62 forming the output section of the bridge drive circuits 62 and 63
Capacitors 645, 648, 655, and 658 are connected between the drain and the source of each of 4, 626, 634, and 636. Thereby, the MOS transistors 61a to 61d
When a surge current flows through the wiring connecting the gate terminal of the MOS transistor and the drive circuit for driving the MOS transistor, the resistor 64
3, 647, 653, 657 and capacitors 645, 64
The integrating circuits of 8, 655 and 658 function as low-pass filters, absorb high-frequency currents, and can suppress surge voltages generated at both ends of each of these capacitors.

That is, the MOS transistors 61a-61
Each of the resistors 643, 64 so that the surge voltage generated between the gate and the source of d falls within the withstand voltage (30 V) of the element.
7, 653, 657 and capacitors 645, 6
48, 655, and 658 are set. This set value is determined by the size of the distributed capacitance, the voltage (breakdown voltage) generated at the time of dielectric breakdown of the lamp 2, the wiring pattern of the circuit function unit, the mounting structure, and the like. According to experiments, the resistance value R of each of the resistors 643, 647, 653, 657 and the capacitors 645, 648, 655, 658.
By setting the time constant (C × R) of the capacitor C to 0.2 microsecond or more, the surge voltage could be suppressed to the withstand voltage of the element or less.

Similarly, each bridge drive circuit 62,
A capacitor 64 between the VS terminal 63 and the COM terminal 63
9, 659 are connected. As a result, the midpoint potential points X and Y of the H bridge circuit 61 and each bridge drive circuit 62,
When a surge current flows through the wiring connecting the VS terminal 63 and the VS terminal 63, the resistors 644 and 654 and the capacitors 649 and 65
9 acts as a low-pass filter, absorbs high-frequency current, and can attenuate the surge voltage generated across these capacitors.

That is, the resistance values of the resistors 644 and 654 and the capacitor 64 are set so that the surge voltage generated between the VS terminal and the COM terminal falls within the breakdown voltage between them.
9, 659 are set. This set value is also determined by the magnitude of the distributed capacitance, the voltage (breakdown voltage) generated at the time of dielectric breakdown of the lamp 2, the wiring pattern of the circuit function unit, the mounting structure, and the like. According to the experiment, the resistance value R of each resistor 644, 654 and the capacitor 64
For a capacity C of 9, 659, the time constant (C × R) is set to 0.
When the time was set to 01 microseconds or more, the surge voltage could be suppressed to the withstand voltage between the VS terminal and the COM terminal or less.

Further, in this embodiment, the resistance 64
3, 647, 653, 657 and M of the H-bridge circuit 61
A low-pass filter including an integration circuit is configured by the capacitance (MOS capacitance) between the gate and the source of each of the OS transistors 61a to 61d. For this reason, in this integration circuit, the surge voltage may be set to be equal to or less than the withstand voltage of the MOS transistors 61a to 61d in the same manner as described above.
According to experiments, the resistors 643, 647, 653, 657 and the MOS transistors 61a to 61
By setting the time constant of the capacitance between the gate and the source of d to 0.2 microseconds or more, the surge voltage could be suppressed to the withstand voltage of the element or less.

It should be noted that the resistors 643, 6
47, 653, 657 and capacitors 645, 648, 6
In the case where neither 55 nor 658 is provided, the weak portion, that is, the semiconductor device (623 to 6
26, 633-636, 61a-61d) were destroyed. This destruction occurs because the surge current flows through the wiring connecting the gate terminal of the MOS transistor of the H-bridge circuit 61 and the drive circuit that drives the MOS transistor, and the surge voltage generated thereby exceeds the withstand voltage of the element.

That is, since the resistor 643 or the like or the capacitor 645 or the like is not provided, when a surge current flows, the gate and the source of the MOS transistors 61a to 61d (the MOS transistors 624, 626, 634,
A large potential difference exceeding the withstand voltage of the element is generated between the drain and the source 636.

In a semiconductor device having a MOS structure, the withstand voltage of a gate portion is determined by the thickness of a gate oxide film.
The thickness of the gate oxide film is usually several hundred to 1,000 °. The withstand voltage of the gate oxide film is proportional to the film thickness, and the theoretical value at a thickness of 1000 ° is about 80V. However, in practice, the withstand voltage varies due to a defect of the oxide film or the like, so that a weak portion is generated, and such a weak portion is broken.

Since the semiconductor maker rejects an element having a withstand voltage less than a predetermined withstand voltage in the inspection, when the gate oxide film thickness is 1000 殆 ど, most of the elements have a withstand voltage of about 80 V. Some have low withstand voltage,
Such an element is destroyed. (Other Embodiments) In the above embodiment, the capacitors 645, 648,
Not all 655 and 658 are necessary. For example,
If control is performed so that a high-voltage pulse is always generated when the MOS transistors 61a and 61d are on and the MOS transistors 61b and 61c are off, the path of the surge current is limited.
55 is sufficient.

The path through which the surge current flows depends on the component arrangement, the wiring pattern, and the like. Therefore, it is possible to reduce the number of capacitors to one by devising the component arrangement and the wiring pattern.

Further, in the above embodiment, the resistance 643,
Capacitors 645, 64 together with 647, 653, 657
8, 655 and 658, but the H-bridge circuit 6
In terms of preventing the destruction of the first MOS transistors 61a to 61d, the resistors 643, 647, 653, 657
It may be only.

In the above embodiment, the resistors 644 and 654 and the capacitors 649 and 659 are provided to protect the bridge drive circuits 62 and 63 from withstand voltage.
If the control state of the H-bridge circuit 61 at the time of starting is determined in advance, only one of the bridge drive circuits 62 and 63 may be protected, and the resistance and the capacitor may be one.
One by one.

That is, when the lamp 2 is started, the MOS transistors 61a and 61d are turned on, and the MOS transistor 6 is turned on.
When controlling to turn off 1b and 61c, the midpoint potential point Y of the H-bridge drive circuit 61 is almost at the ground potential, so that even if a surge voltage occurs, it is not a problematic level. Therefore, in this case, only the resistor 644 and the capacitor 649 are used, and the resistor 654 and the capacitor 65 are used.
9 may be eliminated.

Conversely, MOS transistors 61a and 61d
Is turned off and the MOS transistors 61b and 61c are turned on, only the resistor 654 and the capacitor 659 are provided.

If the control state of the H-bridge circuit 61 at the time of generation of a high-voltage pulse for starting the lamp 2 is not determined, any of the bridge drive circuits 62,
It is preferable to provide all the resistors 644 and 654 and the capacitors 649 and 659 so as to protect the 63 as well.

The bridge drive circuits 62 and 63 include high and low driver circuits (Internet
ionic Rectifier, IR2101)
, But is not limited to this.
Any other bridge driving circuit can be used.
For example, MOS transistors 623-626, 633-
Instead of two 636s connected in series, one of them may be a resistor or a coil.

The switch elements (61a to 61d) of the H-bridge circuit 61 can also be applied to IGBT elements.

The high-voltage pulse generating circuit 7 is shown in FIGS.
The circuit is not limited to the circuit shown in FIG. 1, but may be any circuit that can generate a high-voltage pulse for starting.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a discharge lamp device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a control circuit 10 in FIG. 1;

FIG. 3 is a diagram showing an assembly configuration of the discharge lamp device shown in FIG.

4 is a diagram showing details of an inverter circuit 6 in the discharge lamp device of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... In-vehicle battery, 2 ... Lamp, 4 ... DC-DC converter, 6 ... Inverter circuit, 7 ... Starting circuit, 61 ... H bridge circuit, 400 ... H bridge control circuit, 500 ... High voltage generation control circuit, 643, 644 , 647, 653,
654, 657... Resistance, 645, 648, 649, 65
5, 658, 659 ... capacitors.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 41/24 H05B 41/24 K (72) Inventor Masamichi Ishikawa 1-1-1 Showa-cho, Kariya-shi, Aichi Stock Shares Inside Company Denso (72) Inventor Satoru Oda 500 Kitawaki, Shimizu City, Shizuoka Prefecture Inside Koito Manufacturing Shizuoka Plant (72) Inventor Yukinobu Hiraka 500 Kitawaki Shimizu City, Shizuoka Prefecture Koito Manufacturing Shizuoka Plant F Term (reference) 3K072 AA13 AC01 BA03 BA05 BB01 BB10 DD08 EB07 FA08 GA03 GB18 GC04 HB03 3K083 AA20 AA26 AA92 BA04 BA25 BA26 BA33 BC15 BC34 BC47 BD04 BD16 BD22 CA33 EA09 5H007 AA06 BB03 CA02 CA03 CB09 CC13 CC03

Claims (9)

[Claims] An H-bridge circuit (61) in which four semiconductor switching elements (61a to 61d) having a MOS structure are arranged in an H-bridge shape, and a bridge drive circuit (41) for driving the four semiconductor switching elements (61). 6
2, 63), and a high-voltage pulse generating means (7) for applying a high-voltage pulse to the discharge lamp (2) and starting to turn on the discharge lamp. ) And the high-voltage pulse generating means are housed in the same case, wherein the bridge drive circuit includes four drive circuit units for driving each of the four semiconductor switching elements. Have
Output terminals (Ho terminal, Lo terminal) of these four drive circuit units are connected to respective gate terminals of the four semiconductor switching elements, and based on a potential difference between the output terminals and a negative reference potential of each drive circuit unit. Each of the four semiconductor switching elements is driven, and an output terminal of the bridge drive circuit and a gate terminal of the semiconductor switch elements (61a to 61d) of the H bridge circuit have first resistors (643, 647, 653, 657), and at least one of the four drive circuit units has a first capacitor (645, 648, 655, 658) between the output terminal and the wiring serving as the negative reference potential. A discharge lamp device characterized by being connected via a). 2. An H-bridge circuit (61) in which four semiconductor switching elements (61a to 61d) having a MOS structure are arranged in an H-bridge shape, and an output terminal connected to a gate terminal of the semiconductor switching element (61). An inverter circuit (6) including a bridge drive circuit (62, 63) having a Ho terminal and a Lo terminal) for driving the semiconductor switching element; and applying a high voltage pulse to the discharge lamp (2). A high-voltage pulse generating means (7) for starting lighting of the discharge lamp device, wherein the inverter circuit (6) and the high-voltage pulse generating means are housed in the same case; The circuit has two directly connected circuits corresponding to each of the four semiconductor switching elements.
MOS transistors (623-626, 633-6
36), and drives the four semiconductor switching elements based on the potential of each connection point of the two MOS transistors connected in series. The output of the bridge drive circuit A terminal and a gate terminal of the semiconductor switch element (61a to 61d) of the H-bridge circuit are connected via a first resistor (643, 647, 653, 657). At least one of the four sets is a low-side MOS transistor (624, 62) connected in series.
6, 634, 636) between the drain and the source.
A discharge lamp device characterized by being connected via capacitors (645, 648, 655, 658). 3. The method according to claim 1, wherein the capacitance of the first capacitor and the capacitance of the first capacitor are different.
The capacitance of the first capacitor and the first capacitor are controlled so that a time constant determined by the resistance value R of the resistor is 0.2 microsecond or more.
The discharge lamp device according to claim 1, wherein a resistance value of the resistor is set. 4. The M switch so that a time constant determined by a MOS capacitance C of the semiconductor switching element having a MOS structure and a resistance value R of the first resistor is 0.2 microsecond or more.
The discharge lamp device according to any one of claims 1 to 3, wherein an OS capacity and a resistance value of the first resistor are set. 5. An H-bridge circuit (61) in which four semiconductor switching elements (61a to 61d) having a MOS structure are arranged in an H-bridge shape, and an output terminal connected to a gate terminal of the semiconductor switching element (61). An inverter circuit (6) including a bridge drive circuit (62, 63) having a Ho terminal and a Lo terminal) for driving the semiconductor switching element; and applying a high voltage pulse to the discharge lamp (2). And a case accommodating both the inverter circuit (6) and the high-voltage pulse generating means. The output terminal of the bridge drive circuit and the H-bridge circuit The gate terminals of the semiconductor switch elements (61a to 61d) are connected via first resistors (643, 647, 653, 657), MO of the semiconductor switching element having a concrete
A discharge lamp, wherein the MOS capacitor and the resistance value of the first resistor are set so that a time constant determined by the S capacitance C and the resistance value R of the first resistor is 0.2 microsecond or more. apparatus. 6. Two of the four drive circuit units are connected to a terminal (VS terminal) serving as a negative-side reference potential at a midpoint potential point (X, Y) of the H-bridge circuit. One of the four driving circuit sections is connected to a terminal (COM terminal) serving as a negative-side reference potential, and the four driving circuit sections are based on a potential difference between the output terminal and the negative-side reference potential of each driving circuit section. At least one of the two bridge drive circuits in which a terminal serving as the negative reference voltage is connected to a midpoint potential point of the H-bridge circuit. , The midpoint potential point of the H-bridge circuit and the terminal serving as the negative reference potential are connected to a second resistor (6
44, 654), and between the resistor and the terminal serving as the negative-side reference potential and the ground potential point are connected via a second capacitor (649, 659). The discharge lamp device according to any one of claims 1 to 5, wherein 7. The resistance value of the second resistor and the second capacitor so that a time constant determined by the resistance value R of the second resistor and the capacitance C of the second capacitor is 0.01 microsecond or more. The discharge lamp device according to claim 6, wherein a capacity of the discharge lamp is set. 8. An H-bridge circuit (61) in which four semiconductor switching elements (61a to 61d) having a MOS structure are arranged in an H-bridge shape, and a bridge drive circuit (41) for driving the four semiconductor switching elements (61). 6
2, 63), and a high-voltage pulse generating means (7) for applying a high-voltage pulse to the discharge lamp (2) and starting to turn on the discharge lamp. ) And the high voltage pulse generating means are housed in the same case, wherein the bridge drive circuit comprises four drive circuit units (4) for driving each of the four semiconductor switching elements. 62
1, 622, 631, 632), and the output terminals (Ho terminal, Lo terminal) of these four drive circuit units are connected to the respective gate terminals of the four semiconductor switching elements, and the four drive circuits are driven. Two of the circuit units are connected to the midpoint potential point (X, Y) of the H-bridge circuit at the terminal (VS terminal) serving as the negative reference potential, and the other two terminals are used as the negative reference potential. (COM terminal) is connected to a ground potential point, and drives each of the four semiconductor switching elements based on a potential difference between the output terminal and the negative reference potential of each drive circuit unit. In at least one of the two bridge drive circuits, the terminal serving as the negative-side reference voltage is connected to the midpoint potential point of the H-bridge circuit. And the terminal which becomes the resistor (64
4, 654), and between the resistor and the terminal serving as the negative-side reference potential and the ground potential point are connected via capacitors (649, 659). Discharge lamp device. 9. The resistance value of the resistor and the capacitance of the capacitor are set such that a time constant determined by the resistance value R of the resistor and the capacitance C of the capacitor is 0.01 microsecond or more. The discharge lamp device according to claim 8, wherein: