JP7451325B2 - Image projection devices and vehicle lights - Google Patents

Description

The present invention relates to an image projection device and a vehicle lamp, and more particularly to an image projection device and a vehicle lamp that project an image by reflecting light with a digital mirror device including a plurality of minute mirrors.

In recent years, with the development of vehicle driving support technology and automatic driving technology, the necessity of transmitting vehicle operation schedules and information to the outside of the vehicle has been discussed. As a method of presenting information to the outside of a vehicle, a method has been proposed in which an image projection device is mounted on a vehicle lamp and an image is projected onto a road surface or the like (for example, see Patent Document 1). In the image projection device and vehicle lamp described in Patent Document 1, an image is projected by reflecting light using a digital mirror device (DMD) that includes, in particular, a plurality of minute mirrors.

Japanese Patent Application Publication No. 2020-055519

In conventional image projection devices, various electronic components including a digital mirror device are mounted on a circuit board, but the mounting density of the electronic components becomes high, making it difficult to miniaturize the device. Furthermore, there is a problem in that the temperature around the digital mirror device increases due to the heat generated by each electronic component. A digital mirror device is a component that drives a large number of minute mirrors to reflect light emitted from a light source, and therefore has a limited usable temperature range. Furthermore, driving the digital mirror device in a high-temperature environment has the problem of shortening the product life and reducing reliability.

In order to solve the above-mentioned problem, if electronic components are distributed and mounted on multiple circuit boards, and the boards are electrically connected using flexible cables, static electricity will be generated when connecting the flexible cables, causing damage to the circuit boards. There is a possibility of damaging electronic components. Therefore, it is necessary to connect a protection element to the wiring on the circuit board to protect the electronic equipment from static electricity.

FIG. 9 is a schematic diagram showing a wiring pattern and a protection element on a circuit board. A connector section to which a flexible cable is connected is mounted on the circuit board, and the wiring pattern on the circuit board and the wiring of the flexible cable are electrically connected via the connector section. A ground wiring pattern 1 and a signal wiring pattern 2 are formed on the wiring pattern on the circuit board, and an electrostatic protection element 3 is mounted on the signal wiring pattern 2.

In a circuit board having such a wiring pattern, even if static electricity flows from the connector portion when a flexible cable is connected, surge current can be released from the signal wiring pattern 2 to the ground wiring pattern 1. This can prevent damage to electronic components due to static electricity when connecting the flexible cable.

However, since the image projection apparatus has a large number of wiring patterns for driving the digital mirror device, the number of electrostatic protection elements 3 to be mounted also increases. Therefore, it is necessary to reduce the density of the wiring pattern on the circuit board to secure an area for mounting the electrostatic protection element 3, which makes it difficult to miniaturize the circuit board.

The present invention has been devised in view of the above-mentioned conventional problems, and it is possible to protect electronic components from static electricity even when connecting flexible cables, and to reduce the size of the circuit board. The purpose of the present invention is to provide a projection device and a vehicle lamp.

In order to solve the above problems, an image projection apparatus of the present invention is an image projection apparatus that projects an image by reflecting light with a digital mirror device including a plurality of minute mirrors, the digital mirror device being mounted a mirror mounting board formed separately from the mirror mounting board, a power supply mounting board formed separately from the mirror mounting board, and a flexible cable electrically connecting the mirror mounting board and the power supply mounting board; A signal wiring pattern electrically connected to the flexible cable is formed on the power supply mounting board, and an electrostatic protection element is connected to the plurality of signal wiring patterns at once , and the electrostatic protection The element includes a plurality of signal wiring terminals connected to the signal wiring pattern and a ground terminal connected to a ground potential, and the ground terminal is arranged between the signal wiring terminals, and the ground terminal and the ground terminal are arranged between the signal wiring terminals. The signal wiring terminals are arranged in a line in a direction intersecting the extending direction of the signal wiring pattern .

In such an image projection device of the present invention, since the electrostatic protection element is connected to multiple signal wiring patterns at once, the density of the signal wiring patterns is increased and the size of the mirror mounting board and the power supply mounting board is reduced. In addition, the electronic components mounted on the mirror mounting board and the power supply mounting board can be protected from static electricity even when connecting the flexible cable.

Further, in one aspect of the present invention, the electrostatic protection element includes a plurality of diodes corresponding to the number of the signal wiring patterns.

Further, in one aspect of the present invention, the electrostatic protection element includes a Zener diode connected in parallel to the signal wiring pattern.

Further, in one aspect of the present invention, the mirror mounting board and the power supply mounting board include a front surface on which the signal wiring pattern is formed and a back surface on which a ground wiring pattern is formed, and a wire that penetrates from the back surface to the front surface is provided. The ground wiring pattern is extended to the surface by the through hole, and the signal wiring pattern is bent to avoid the through hole .

Further, in one aspect of the present invention, the plurality of signal wiring terminals are arranged symmetrically with respect to the ground terminal.

Further, a vehicle lamp according to the present invention is characterized by comprising the image projection device described in any one of the above, and a light source unit that irradiates light to the image projection device.

According to the present invention, it is possible to provide an image projection device and a vehicle lamp that can protect electronic components from static electricity even when connecting a flexible cable, and can downsize the circuit board.

FIG. 1 is a schematic perspective view showing a configuration example of a vehicle lamp 100 according to a first embodiment. FIG. 1 is a schematic plan view showing a configuration example of an image projection device 10 according to a first embodiment. FIG. 1 is a block diagram schematically showing a power supply line of the image projection device 10 according to the first embodiment. FIG. 2 is a schematic diagram showing a structural example of a flexible cable 108 according to the first embodiment. It is a schematic diagram which shows the case where the electrostatic protection element 120 is arrange|positioned for each wiring pattern formed on the mirror mounting board|substrate 101a and the power supply mounting board|substrate 101b. FIG. 3 is a partially enlarged view showing surge countermeasures using the electrostatic protection element 122 of the image projection device 10 according to the first embodiment. 7(a) is a schematic plan view showing the external appearance of the package and terminals, and FIG. 7(b) is an equivalent circuit diagram. FIG. FIG. 8A is a diagram showing the image projection device 10 according to the second embodiment, and FIG. b) is a partially enlarged view of the vicinity of the electrostatic protection element 122 in FIG. 8(a). FIG. 3 is a schematic diagram showing a wiring pattern and a protection element on a circuit board.

(First embodiment)
Embodiments of the present invention will be described in detail below with reference to the drawings. Identical or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. FIG. 1 is a schematic perspective view showing a configuration example of a vehicle lamp 100 according to the present embodiment. As shown in FIG. 1, the vehicle lamp 100 includes an image projection device 10, a light source section 20, a reflector 30, a projection lens 40, and a heat sink 50, and projects an image onto a projection surface 60.

The image projection device 10 controls the reflection direction of light within the plane based on the on information and off information included in the information of the image to be projected, and divides the light emitted from the light source unit 20 into projection light Lon and shielding light Loff. It is a device that reflects light as The projection light Lon is irradiated onto the projection surface 60 via the projection lens 40, and an image is projected by irradiating the area corresponding to the ON information with the light. The shielding light Loff reaches a shielding part (not shown) and is blocked, and is not irradiated to the outside.

The light source section 20 is a device that irradiates light onto the reflector 30 based on power and signals supplied from the outside, and includes, for example, a light emitting diode (LED) or a semiconductor laser (LASER: Light Amplification by Stimulated). Emission of Radiation) can be used. The light emitted from the light source unit 20 may be continuous wave (CW) light, pulsed light, or PWM (pulse width modulation) controlled light.

The reflector 30 is an optical member that reflects the light emitted from the light source section 20 to the image projection device 10. The shape of the reflective surface of the reflector 30 is not limited, and a curved surface such as a paraboloid or an elliptical surface can be used. The light reflected by the reflector 30 may have its optical diameter expanded toward the image projection device 10, or may be parallel light.

The projection lens 40 is an optical member disposed on the optical path of the projection light Lon reflected by the image projection device 10, and magnifies the projection light Lon and irradiates it onto the projection surface 60. Although FIG. 1 shows an example in which one lens is used as the projection lens 40, it may be configured with a plurality of lenses. Further, although FIG. 1 shows an example of a convex lens, a known lens structure such as a concave lens or an aspherical lens can be used.

The heat sink 50 is a member on which the light source section 20 is mounted and arranged to improve heat dissipation. Although the material constituting the heat sink 50 is not limited, for example, copper or aluminum having high thermal conductivity, high thermal conductive resin, etc. can be used. Further, although the structure and shape of the heat sink 50 are not limited, if a plurality of fins are provided upright on the rear surface side, the heat dissipation performance can be further improved.

The projection surface 60 is provided outside the vehicle lamp 100, and is a surface onto which the projection light Lon is irradiated and an image is projected. Examples of the projection plane 60 include a road surface, a wall surface of a structure, the body of another vehicle, and the body of the own vehicle. Although a flat surface is shown as the projection surface 60 in FIG. 1, it is sufficient that an image can be projected and displayed by being irradiated with the projection light Lon, and the projection surface 60 may be a curved surface or a surface having irregularities.

FIG. 2 is a schematic plan view showing a configuration example of the image projection device 10 according to the present embodiment. As shown in FIG. 3, the image projection device 10 includes a mirror mounting board 101a, a power supply mounting board 101b, a digital mirror device 102, a temperature sensor section 103, a mirror control section 104, a flash memory 105, and a mirror control section. power supply section 106, voltage monitoring section 107, flexible cable 108, mirror power supply section 109, control microcomputer 110, voltage adjustment section 111, microcomputer power supply section 112, deserializer 113, and cooling power supply section 114, and connector parts 115 and 116.

The mirror mounting board 101a and the power supply mounting board 101b are circuit boards on which separately formed electronic components are mounted, and a wiring pattern (not shown) is formed on the surface to provide electrical connection between the electronic components mounted on the surface. It is a member that is connected to form a circuit. Although FIG. 2 shows an example in which electronic components are mounted only on the front surface, a wiring pattern may also be formed on the back surface and electronic components may be mounted thereon. The materials constituting the mirror mounting board 101a and the power supply mounting board 101b are not limited, and a known printed wiring board or the like can be used. In order to improve the heat dissipation of the mirror mounting board 101a and the power supply mounting board 101b, a composite board may be used in which an insulating layer and a wiring pattern are formed on a board made of a highly thermally conductive material such as metal or ceramic. Furthermore, the mirror mounting board 101a and the power supply mounting board 101b may be formed using the same material or having the same structure, or may be formed using different materials or having different structures.

As shown in FIG. 2, a digital mirror device 102, a temperature sensor section 103, a mirror control section 104, a flash memory 105, a power supply section 106 for the mirror control section, and a voltage monitoring section 107 are mounted on the mirror mounting board 101a. ing. Further, on the power supply mounting board 101b, a mirror power supply section 109, a control microcomputer 110, a voltage adjustment section 111, a microcomputer power supply section 112, a deserializer 113, a cooling power supply section 114, and connector sections 115 and 116 are mounted. .

The digital mirror device 102 is an electronic component in which minute mirrors are arranged in a matrix, and the tilt angle can be changed between an on state and an off state. The projection light Lon reflected by the mirror in the on state and the shielding light Loff reflected in the off state are separated, and an image is projected by irradiating the projection light Lon.

The temperature sensor unit 103 is an electronic component that is placed near the digital mirror device 102 and measures the temperature of the digital mirror device. The temperature measured by the temperature sensor section 103 is transmitted to the mirror control section 104 and the control microcomputer 110 as temperature information. The specific configuration of the temperature sensor section 103 is not limited, and a thermistor, thermocouple, digital temperature sensor, etc. can be used.

The mirror control unit 104 is an electronic component that transmits a control signal to the digital mirror device 102 based on on information and off information included in an image, and controls switching between an on state and an off state of the mirror. Further, the mirror control section 104 is connected to a control microcomputer 110 via a flexible cable 108, and its driving is controlled by a control signal from the control microcomputer 110. The mirror control unit 104 and the digital mirror device 102 are arranged close to each other on the mirror mounting board 101a because they need to operate at a high speed (for example, 600 MHz or higher) required for image rendering.

The flash memory 105 is a storage unit for holding information necessary for driving the mirror control unit 104. Information stored in the flash memory 105 includes programs executed by the mirror control unit 104, various setting information, image data, and the like.

The mirror control unit power supply unit 106 is a power supply circuit that is supplied with power from the voltage adjustment unit 111 via the flexible cable 108 and supplies power to the mirror control unit 104 . A relatively large voltage is supplied to the mirror control section power supply section 106 from the voltage adjustment section 111 via the flexible cable 108, but the mirror control section power supply section 106 uses a plurality of DC/DC converters. The voltage is stepped down to a voltage suitable for driving the mirror control unit 104 and power is output. As an example of voltage conversion of the power supply section 106 for the mirror control section, for example, DC 6V is supplied and DC 3.3V, 1.8V, 1.1V, etc. are output.

The voltage monitoring unit 107 is an electronic component that monitors the mirror drive voltage supplied from the mirror power supply unit 109 to the digital mirror device via the flexible cable 108. Further, the voltage monitoring unit 107 is electrically connected to the mirror control unit 104 and the control microcomputer 110, and transmits the measured value of the voltage being monitored. For example, if the voltage on the mirror mounting board 101a supplied from the flexible cable 108 is lower than a predetermined value, the mirror control unit 104 stops the operation of the digital mirror device 102. Thereby, disconnection or poor connection of the flexible cable 108, failure of the mirror power supply section 109, etc. can be detected, and malfunctions of the digital mirror device 102 can be prevented.

The flexible cable 108 is a wiring cable in which a plurality of wirings are collectively protected with flexible resin or the like, and electrically connects the mirror mounting board 101a and the power supply mounting board 101b. The connection method between the flexible cable 108 and the mirror mounting board 101a and the power supply mounting board 101b is not particularly limited, and a method such as insertion into connectors mounted on both boards can be used. Since the flexible cable 108 has flexibility, by bending it, mutual electrical connection can be ensured regardless of the arrangement of both boards.

The mirror power supply section 109 is a power supply circuit that is supplied with power from outside the image projection apparatus 10 via the connector section 115 and supplies power to the digital mirror device 102 via the flexible cable 108 . The mirror power supply section 109 is composed of a plurality of electronic components, and includes a series regulator and a DC/DC converter. Examples of the output of the mirror power supply section 109 include DC 16V, 8.5V, -10V, and the like.

The control microcomputer 110 is an electronic component that controls the driving of the entire image projection apparatus 10 based on control signals and various measured values. The control microcomputer 110 is capable of communicating information with the outside via the connector section 116, and is supplied with image information and control signals from the outside. Furthermore, the measured values of the mirror control section 104, temperature sensor section 103, and voltage monitoring section 107 are transmitted to the control microcomputer 110.

When image information is transmitted from the outside, the control microcomputer 110 transmits the image information to the mirror control unit 104 via the flexible cable 108, and controls the on-state and off-state of the mirror. The control microcomputer 110 also controls the drive of a cooling unit (not shown) based on temperature information from the temperature sensor unit 103 to control the temperature of the digital mirror device 102 . Here, as the cooling unit, a publicly known cooling fan, liquid cooling device, Peltier element, etc. can be used. Furthermore, the control microcomputer 110 controls the drive of the image projection device 10 based on the measured value of the voltage monitoring unit 107, and for example, if the signal from the voltage monitoring unit 107 is interrupted, the flexible cable 108 may be disconnected or dropped. It is determined that this is the case, and the output from the mirror power supply unit 109 is stopped.

Here, the control microcomputer 110 controls the cooling power supply section 114 and the cooling section by executing a pre-recorded program, and also constitutes a cooling control section in the present invention in order to cool the image projection apparatus 10. . Although an example has been shown in which part of the functions of the control microcomputer 110 functions as a cooling control section, a dedicated electronic component may be mounted on the power supply mounting board 101b to function as a cooling control section.

The voltage adjustment unit 111 is a circuit that includes a series regulator and a DC/DC converter, and is used in combination with the mirror power supply unit 109 to adjust the voltage. As an example of voltage conversion by the voltage adjustment unit 111, for example, DC 12V is supplied and DC 6V, 3.3V, etc. are output.

The microcomputer power supply section 112 is a power supply circuit that is supplied with power from outside the image projection apparatus 10 via the connector section 115 and supplies power to the control microcomputer 110 . The microcomputer power supply section 112 is composed of a series regulator, and output examples include DC 3.3V, 5V, and the like.

The deserializer 113 is an electronic component that receives image information as serial data from the outside via the connector section 116, converts the serial data into parallel data, and transmits the parallel data to the mirror control section 104.

The cooling power supply section 114 is a power supply circuit that is supplied with power from outside the image projection apparatus 10 via the connector section 115 and supplies power to a cooling section (not shown). The cooling power supply unit 114 is composed of a series regulator, and an example of the output is, for example, DC5V.

The connector parts 115 and 116 are electronic components that secure electrical connection with the outside of the image projection apparatus 10 by inserting a cable or the like. In the image projection apparatus 10, power is supplied from the outside via a connector section 115 to a mirror power supply section 109, a microcomputer power supply section 112, and a cooling power supply section 114. Further, control signals and information are transmitted between the mirror control section 104 and the control microcomputer 110 and the outside via the connector section 116.

As shown in FIG. 2, in the image projection device 10 of this embodiment, the mirror mounting board 101a and the power supply mounting board 101b are electrically connected by a flexible cable 108, and power and control signals are transmitted between them. is said to be communicable. However, since the flexible cable 108 has a structure in which the electrical wiring is covered with flexible resin and has low thermal conductivity, heat conduction between the mirror mounting board 101a and the power supply mounting board 101b is suppressed. There is. This prevents the heat generated from the electronic components mounted on the power supply mounting board 101b from being transmitted to the mirror mounting board 101a side, and it is possible to suppress the temperature rise of the digital mirror device 102.

In addition, since the mirror mounting board 101a and the power supply mounting board 101b are formed separately, electronic components with a relatively small amount of heat generation are mounted on the mirror mounting board 101a, and electronic components with a relatively large amount of heat generation are mounted on the power supply mounting board. By mounting it on the digital mirror device 101b, the temperature rise of the digital mirror device 102 can be suppressed without increasing the size of the circuit board, and it is also possible to reduce the size and weight of the digital mirror device 102.

Here, an example of an electronic component that generates a relatively small amount of heat is the mirror control section power supply section 106. As described above, the power supply unit 106 for the mirror control unit is composed of a DC/DC converter, and has a high conversion efficiency, so the amount of heat generated is small. Further, although the DC/DC converter has characteristics such as a large current capacity and good response performance to load (current) fluctuations, the number of components constituting the circuit increases and the mounting area becomes large. However, in the image projection device 10 of this embodiment, by mounting electronic components on the power supply mounting board 101b, it is easy to secure an area on the mirror mounting board 101a in which the power supply section 106 for the mirror control section is arranged. be.

Examples of electronic components that generate a relatively large amount of heat include the mirror power supply section 109, the voltage adjustment section 111, the microcomputer power supply section 112, and the cooling power supply section 114. As described above, the mirror power supply section 109, the voltage adjustment section 111, the microcomputer power supply section 112, and the cooling power supply section 114 include a series regulator, and the conversion efficiency is low, so the amount of heat generated is large. A series regulator has a characteristic that its current capacity is small and its response performance to load (current) fluctuations is lower than that of a DC/DC converter, but since it can be configured with one chip, the mounting area is small. In the image projection apparatus 10 of this embodiment, the temperature rise of the digital mirror device 102 can be suppressed by mounting the series regulator on the power supply mounting board 101b that is different from the mirror mounting board 101a. Furthermore, by mounting a series regulator that can be configured with one chip on the power supply mounting board 101b, it is possible to reduce the mounting density of electronic components on the power supply mounting board 101b, and it is also possible to suppress the temperature rise on the power supply mounting board 101b. can.

As for other electronic components, the mirror control unit 104 requires short wiring for high-speed operation similar to the digital mirror device 102, and is mounted on the mirror mounting board 101a in close proximity to the digital mirror device 102. . Further, the temperature sensor unit 103 is mounted on the mirror mounting substrate 101a in close proximity to the digital mirror device 102 in order to measure the temperature of the digital mirror device 102. Furthermore, since the flash memory 105 needs to transmit information such as image information and programs to and from the mirror control unit 104, it is mounted on the mirror mounting board 101a in close proximity to the mirror control unit 104. Further, the voltage monitoring unit 107 is for detecting an abnormality in the voltage supplied to the mirror mounting board 101a, so it is mounted on the mirror mounting board 101a.

The control microcomputer 110 does not need to operate as fast as the digital mirror device 102, communicates information with the outside via the connector section 115, and needs to continue operating even if a problem occurs with the flexible cable 108. It is mounted on the power supply mounting board 101b. The deserializer 113 is mounted on the power supply mounting board 101b in order to convert serial data transmitted via the connector section 116 into parallel data and transmit it to the mirror control section 104.

FIG. 3 is a block diagram schematically showing a power supply line of the image projection device 10 according to this embodiment. Power supplied from the outside via the connector section 115 is transmitted to the mirror power supply section 109, the microcomputer power supply section 112, and the cooling power supply section 114, respectively. Examples of the power supplied from the outside include DC 12V supplied from a vehicle-mounted battery. In the example shown in FIG. 3, the microcomputer power supply unit 112 includes two series regulators, each of which outputs 3.3V for driving the control microcomputer 110 and 5V for driving the interface unit. The interface power supply is a power supply for input/output signals when controlling an external device (LDM: LED Driver Module) that drives the LED of the light source. The cooling power supply section 114 includes one series regulator, and outputs 5V for driving a cooling fan, which is a cooling section.

The mirror power supply section 109 and the voltage adjustment section 111 include a plurality of DC/DC converters and a plurality of series regulators, and adjust the voltage outputted via the flexible cable 108. The voltage regulator 111 boosts 12V supplied from the outside to 20V with the first stage DC/DC converter, steps down the voltage to 6V with the second stage DC/DC converter, and outputs the voltage. Part of the output from the second-stage DC/DC converter is supplied to the mirror control unit power supply unit 106 via the flexible cable 108, and part of the output is supplied to the series regulator of the voltage adjustment unit 111 and the mirror power supply unit 109. Supplied. A series regulator included in the voltage adjustment section 111 converts 6V to 3.3V and supplies it to the mirror power supply section 109. The mirror power supply section 109 generates 16V, 8.5V, and -10V from the supplied 6V and 3.3V, and supplies them to the digital mirror device 102 via the flexible cable 108.

The mirror power supply unit 109 includes three DC/DC converters, converts 6V supplied via the flexible cable 108 into 1.1V, 1.8V, and 3.3V, respectively, and supplies the converted voltage to the mirror control unit 104. supply The 1.8V output is also supplied to the digital mirror device 102.

FIG. 4 is a schematic diagram showing a structural example of the flexible cable 108 according to this embodiment. The flexible cable 108 includes a power supply wiring 108a, a single-end wiring 108b, a differential wiring 108c, a single-end wiring 108d, and a ground wiring 108e. Each wiring is formed to extend in the longitudinal direction of the flexible cable 108, and is formed at equal intervals in the width direction. In the example shown in FIG. 4, the single-end wirings 108b and 108d and the differential wiring 108c are formed with a narrow line width (first line width). Further, the power supply wiring 108a and the ground wiring 108e are formed with a line width (second line width) thicker than that of the first wiring.

The power supply wiring 108a is a wiring formed at one end in the width direction of the flexible cable 108, and electrically connects the second stage DC/DC converter of the voltage adjustment unit 111 and the mirror control unit power supply unit 106. This is the wiring. Since it is necessary to supply a relatively large current from the DC/DC converter of the voltage adjustment unit 111 to the mirror control unit power supply unit 106, the line width of the power supply wiring 108a is different from that of the single-end wiring 108b, 108d and the differential wiring. It is formed thicker than the wiring 108c. Specifically, when the single-end wiring 108b, 108d and the differential wiring 108c are formed with a first line width, the power supply wiring 108a is formed with a second line width that is twice or more the first line width. It is formed. Thereby, for example, even when the allowable current of the single-end wiring 108b, 108d and the differential wiring 108c is 500 mA, the allowable current of the power supply wiring 108a can be set to 1 A or more.

The single-end wirings 108b and 108d are formed with a narrower line width (first line width) than the power supply wiring 108a, and are wirings that transmit electrical signals between the mirror mounting board 101a and the power supply mounting board 101b. . Further, the single-end wirings 108b and 108d are formed to have the first line width up to both ends of the flexible cable 108.

The differential wiring 108c is formed at the center in the width direction of the flexible cable 108 with a narrower line width (first line width) than the power supply wiring 108a, and is formed between the mirror mounting board 101a and the power supply mounting board 101b. Wiring that transmits electrical signals. Further, the differential wiring 108c is designed to have a different characteristic impedance from the single-end wirings 108b and 108d. As an example, the characteristic impedance of the single-end wiring 108b and 108d is 50Ω, and the characteristic impedance of the differential wiring 108c is 100Ω.

The ground wiring 108e is a wiring formed at the other end in the width direction of the flexible cable 108, and is a wiring that connects the ground potentials of the mirror mounting board 101a and the power supply mounting board 101b. Between the mirror mounting board 101a and the power supply mounting board 101b, it is necessary to supply a relatively large current from the DC/DC converter 111 to the power supply section 106 for the mirror control section, so the line width of the ground wiring 108e is It is formed with the same line width as the power supply wiring 108a. Thereby, for example, even when the allowable current of the single-end wires 108b, 108d and the differential wire 108c is 500 mA, the allowable current of the ground wire 108e can be set to 1 A or more.

FIG. 5 is a schematic diagram showing a case where electrostatic protection elements 120 are arranged for each wiring pattern (not shown) formed on the mirror mounting board 101a and the power supply mounting board 101b. As shown in FIG. 5, if the electrostatic protection elements 120 are arranged for each wiring pattern, the number of protection elements mounted on the mirror mounting board 101a and the power supply mounting board 101b increases, making it difficult to downsize. .

FIG. 6 is a partially enlarged view showing surge countermeasures using the electrostatic protection element 122 of the image projection device 10 according to the present embodiment. In the example shown in FIG. 6, illustration of the differential wiring 108c is omitted. Further, in FIG. 6, only the vicinity of the area to which the flexible cable 108 is connected on the mirror mounting board 101a is shown in an enlarged manner. Further, although only the mirror mounting board 101a is shown in an enlarged scale, the power supply mounting board 101b also has a similar structure.
As shown in FIG. 6, in the image projection device 10 of this embodiment, a connector section 117 is mounted on the peripheral edge of the mirror mounting board 101a, and a power wiring pattern 121a formed on the mirror mounting board 101a, A connector portion 117 is electrically connected to the signal wiring patterns 121b and 121d and the ground wiring pattern 121e. Electrostatic protection elements 122 are mounted on the signal wiring patterns 121b and 121d, respectively.
As shown in FIG. 6, by inserting and fixing the flexible cable 108 into the connector part 117, the power wiring 108a, single-end wiring 108b, 108d, and ground wiring 108e are connected to the power wiring pattern 121a through the connector part 117. , signal wiring patterns 121b, 121d, and ground wiring pattern 121e.

The power supply wiring pattern 121a is connected to the power supply wiring 108a of the flexible cable 108, and is connected to the mirror power supply unit 109 and voltage for the mirror control unit power supply unit 106 and the digital mirror device 102 mounted on the mirror mounting board 101a. This is a wiring pattern for supplying power from the adjustment unit 111. The signal wiring patterns 121b and 121d are wiring patterns that are connected to the single-end wirings 108b and 108d and transmit electrical signals between the mirror mounting board 101a and the power supply mounting board 101b. The ground wiring pattern 121e is a wiring pattern that is connected to the ground wiring 108e of the flexible cable 108 and supplied with a ground potential, and supplies the ground potential to electronic components mounted on the mirror mounting board 101a.

The electrostatic protection element 122 is an electronic component that is collectively connected to a plurality of wiring patterns included in the signal wiring patterns 121b and 121d, and protects against surge current when a surge current flows through the signal wiring patterns 121b and 121d. It escapes to the ground potential and protects the electronic components mounted on the mirror mounting board 101a. In FIG. 6, there are four wiring patterns included in the signal wiring patterns 121b and 121d, and an example is shown in which the four wiring patterns are collectively protected by one electrostatic protection element 122. The number of wiring patterns to which the element 122 is connected is not limited.

FIG. 7 is a diagram showing a configuration example of the electrostatic protection element 122 according to the present embodiment, FIG. 7(a) is a schematic plan view showing the package appearance and terminals, and FIG. 7(b) is an equivalent circuit diagram. It is. As shown in FIG. 7A, the electrostatic protection element 122 is provided with a D1+ terminal, a D1- terminal, a GND terminal, a D2+ terminal, and a D2- terminal arranged in a line. Further, the GND terminal is provided between the D1- terminal and the D2+ terminal. The shape and size of the electrostatic protection element 122 are not limited, but for example, it is about 3 to 4 mm wide and 2 to 3 mm long, with D1+ terminal, D1- terminal, GND terminal, D2+ terminal, and D2- terminal arranged at a pitch of 0.5 mm. can be used.

The electrostatic protection element 122 includes a plurality of diodes and Zener diodes as shown in the equivalent circuit shown in FIG. Diodes are also connected in parallel. The cathodes of the series-connected diodes are connected to the cathodes of the Zener diodes, and the anodes thereof are connected to a GND terminal to be at ground potential. Furthermore, the intermediate portions of the two diodes connected in series are connected to the D1+ terminal, the D1- terminal, the D2+ terminal, and the D2- terminal, respectively. Here, the D1+ terminal, D1- terminal, D2+ terminal, and D2- terminal are terminals connected to the signal wiring patterns 121b and 121d, and correspond to the signal wiring terminals in the present invention.

The anode side of the Zener diode is connected to a GND terminal and has a ground potential, and the cathode side is connected to the cathode side of the diodes connected in series. Here, since the GND terminal is connected to the ground potential, it corresponds to the ground terminal in the present invention. Further, it is preferable that the ground wiring pattern to which the GND terminal is connected is formed separately from the ground wiring pattern 121e to which the ground wiring 108e is connected.

On the mirror mounting board 101a and the power supply mounting board 101b, the D1+ terminal, D1- terminal, D2+ terminal, and D2- terminal are connected to the wiring patterns included in the signal wiring patterns 121b and 121d, respectively, and the mirror mounting board 101a, which will be described later, is connected to the wiring patterns included in the signal wiring patterns 121b and 121d. A GND terminal is connected to the upper GND1 terminal and GND2 terminal. Thereby, when the image projection device 10 is used, signals are transmitted to the electronic components via the flexible cable 108, the connector section 117, and the signal wiring patterns 121b and 121d. When a surge voltage exceeding the breakdown voltage of the Zener diode is applied to the connector part 117 side, the signal wiring patterns 121b and 121d are connected to the D1+ terminal, D1- terminal, D2+ terminal, D2- terminal, diode, Zener diode, and GND. A surge current flows through the terminal to ground potential.

As a result, the mirror mounting board 101a and the power supply mounting board 101b are formed separately, and the flexible cable 108 is used to connect them, and the temperature rise of the digital mirror device 102 is suppressed while the flexible cable 108 is connected. It is possible to protect electronic components from static electricity and the like, and it is also possible to downsize the circuit board. Since the electrostatic protection element 122 is connected to a plurality of wiring patterns at once, the density of the signal wiring patterns 121b and 121d can be increased to further reduce the size of the mirror mounting board 101a and the power supply mounting board 101b. .

Further, the electrostatic protection element 122 includes a plurality of diodes corresponding to the number of signal wiring patterns 121b and 121d, and the diodes are connected in parallel for each wiring pattern. As a result, deterioration of signal waveforms can be suppressed better than electrostatic countermeasures using capacitors, and it can also be used in electronic equipment that operates at high speed, such as the image projection device 10.

Further, the electrostatic protection element 122 includes a Zener diode connected in parallel to the signal wiring patterns 121b and 121d, and the Zener diode is connected in parallel to a plurality of diodes. As a result, it is possible to take measures against static electricity with a single Zener diode for a plurality of wiring patterns in the signal wiring patterns 121b and 121d, downsize the electrostatic protection element 122, reduce the mounting area, and connect it to the mirror mounting board 101a. The power supply mounting board 101b can be further downsized.

In addition, by placing the GND terminal between the D1+ terminal, D1- terminal, D2+ terminal, and D2- terminal included in the electrostatic protection element 122, the terminal arrangement becomes bilaterally symmetrical and is mounted on the signal wiring patterns 121b and 121d. This can prevent incorrect connections when connecting.

As described above, in the image projection device 10 of this embodiment, the electrostatic protection element 122 is connected to the plurality of signal wiring patterns 121b, 121d at once, so the density of the signal wiring patterns 121b, 121d is reduced. It is possible to reduce the size of the mirror mounting board 101a and the power supply mounting board 101b by increasing the height, and to protect the electronic components mounted on the mirror mounting board 101a and the power supply mounting board 101b even when connecting the flexible cable 108. .

(Second embodiment)
Next, a second embodiment of the present invention will be described using FIG. 8. Description of contents that overlap with those of the first embodiment will be omitted. FIG. 8 is a diagram showing the image projection device 10 according to the present embodiment, and FIG. 8(a) is a partially enlarged photograph showing a state where the mirror mounting board 101a and the power supply mounting board 101b are connected with the flexible cable 108, FIG. 8(b) is a partially enlarged view of the area around the electrostatic protection element 122 in FIG. 8(a).

In the example shown in FIG. 8A, the flexible cable 108 includes 39 single-end wiring patterns 108b and 108d, and the mirror mounting board 101a and the power supply mounting board 101b each include 30 signal wiring patterns 121b. , 121d are formed. The electrostatic protection element 122 shown in FIG. 7 is used as the electrostatic protection element 122, and in order to mount the electrostatic protection element 122 on every four wiring patterns, the electrostatic protection element 122 is mounted on the mirror mounting board 101a and the power supply mounting board 101b. Each has 10 pieces installed.

In this embodiment, as shown in FIG. 8B, signal wiring patterns 121b1, 121b2, 121b3, and 121b4 and ground wiring patterns GND1 and GND2 are formed on the mirror mounting board 101a. The ground wiring patterns GND1 and GND2 are formed between the signal wiring patterns 121b2 and 121b3, have a larger line width than the signal wiring pattern 121b, and are formed in a substantially circular shape at the end. The D1+ terminal, D1- terminal, GND terminal, D2+ terminal, and D2- terminal of the electrostatic protection element 122 are connected to signal wiring patterns 121b1, 121b2, ground wiring patterns GND1, GND2, and signal wiring patterns 121b3, 121b4, respectively. .

Since the D1+ terminal, D1- terminal, GND terminal, D2+ terminal, and D2- terminal of the electrostatic protection element 122 are arranged at the same pitch, the signal wiring patterns 121b1, 121b2, 121b3, and 121b4 are similar to the ground wiring patterns GND1, It is formed as a bent pattern so as to avoid a circular shape at the end of GND2.

In the mirror mounting board 101a and the power supply mounting board 101b, through holes are formed in the circular parts at the ends of the ground wiring patterns GND1 and GND2, and the ground wiring patterns GND1 and GND2 formed on the back side and the front side are connected to each other. electrically connected. In this way, by extending the ground wiring patterns GND1 and GND2 from the back side to the front side using the through holes, the ground potential can be supplied to the plurality of electrostatic protection elements 122.

When mounting one electrostatic protection element 3 on one signal wiring pattern 2 as shown in FIG. 9, if the width from the grounding wiring pattern 1 to the electrostatic protection element 3 is 2 mm, 39 Using the ground wiring pattern 1 and the electrostatic protection element 3, a width of 78 mm is required.

However, in the image projection device 10 of this embodiment, as shown in FIGS. 8(a) and 8(b), a ground wiring pattern is formed using through holes for four signal wiring patterns 121b1, 121b2, 121b3, and 121b4. GND1 and GND2 are provided, and one electrostatic protection element 122 is used as a countermeasure against electrostatic discharge. At this time, the width necessary to protect the four signal wiring patterns 121b is 3 to 4 mm, which is the same as the width of the electrostatic protection element 122. Therefore, the width required to mount 10 electrostatic protection elements 122 is 30 to 40 mm, and the density of the signal wiring patterns 121b and 121d is increased to reduce the size of the mirror mounting board 101a and the power supply mounting board 101b. can be achieved.

In addition, in the example shown in FIG. 8(b), since the ground wiring patterns GND1 and GND2 are provided in two places, upper and lower, even if the electrostatic protection element 122 is installed in the upper and lower parts by mistake, the ground potential can be ensured. can be supplied to the GND terminal to protect the signal wiring pattern 121b.

In the image projection device 10 of this embodiment as well, in order to connect the electrostatic protection element 122 to the plurality of signal wiring patterns 121b and 121d all at once, the density of the signal wiring patterns 121b and 121d is increased and the mirror mounting board 101a and It is possible to downsize the power supply mounting board 101b and protect the electronic components mounted on the mirror mounting board 101a and the power supply mounting board 101b even when connecting the flexible cable 108. In addition, by extending the ground wiring patterns GND1 and GND2 from the back side to the front side using through holes, the mounting area of the electrostatic protection element 122 can be reduced, and the mirror mounting board 101a and the power supply mounting board 101b can be further downsized. can be achieved.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. are also included within the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100... Vehicle lamp 10... Image projection device 20... Light source part 30... Reflector 40... Projection lens 50... Heat sink 60... Projection surface 101a... Mirror mounting board 101b... Power supply mounting board 102... Digital mirror device 103... Temperature sensor part 104... Mirror control unit 105...Flash memory 106...Mirror control unit power supply unit 107...Voltage monitoring unit 108...Flexible cable 108a...Power supply wiring 108b, 108d...Single-end wiring 108c...Differential wiring 108e...Ground wiring 109...Mirror power supply unit 110... Control microcomputer 111... Voltage adjustment section 112... Power supply section for microcomputer 113... Deserializer 114... Cooling power supply section 115, 116, 117... Connector section 120... Electrostatic protection element 121a... Power supply wiring pattern 121b, 121d... Signal wiring pattern 121e, GND1, GND2...Ground wiring pattern 122...Electrostatic protection element

Claims (6)

An image projection device that projects an image by reflecting light with a digital mirror device equipped with a plurality of minute mirrors,
a mirror mounting board on which the digital mirror device is mounted;
a power supply mounting board formed separately from the mirror mounting board;
comprising a flexible cable that electrically connects the mirror mounting board and the power supply mounting board,
A signal wiring pattern electrically connected to the flexible cable is formed on the mirror mounting board and the power supply mounting board,
comprising an electrostatic protection element connected to a plurality of the signal wiring patterns at once ,
The electrostatic protection element includes a plurality of signal wiring terminals connected to the signal wiring pattern and a ground terminal connected to a ground potential,
the ground terminal is arranged between the signal wiring terminals,
The image projection device is characterized in that the ground terminal and the signal wiring terminal are arranged in a line in a direction intersecting an extending direction of the signal wiring pattern . The image projection device according to claim 1 ,
The mirror mounting board and the power supply mounting board include a front surface on which the signal wiring pattern is formed and a back surface on which a ground wiring pattern is formed,
The ground wiring pattern is extended to the front surface by a through hole penetrating from the back surface to the front surface,
The image projection device is characterized in that the signal wiring pattern is bent to avoid the through hole . The image projection device according to claim 1 or 2,
The image projection device is characterized in that the plurality of signal wiring terminals are arranged symmetrically with respect to the ground terminal. The image projection device according to any one of claims 1 to 3 ,
The image projection device is characterized in that the electrostatic protection element includes a plurality of diodes corresponding to the number of the signal wiring patterns. The image projection device according to any one of claims 1 to 4 ,
The image projection device is characterized in that the electrostatic protection element includes a Zener diode connected in parallel to the signal wiring pattern. An image projection device according to any one of claims 1 to 5,
A vehicular lamp comprising a light source unit that irradiates light to the image projection device.