Strobe Device and Driver Monitoring System

Abstract

A strobe device 2 comprises: a battery member (12) having a positive electrode (12a) and a negative electrode (12b), the positive electrode (12a) being connected to a power supply (10) that outputs a DC voltage, the negative electrode (12b) being connected to a virtual ground; a light-emitting body (13) having an anode and a cathode, the cathode being connected to the ground or virtual ground; and a DC conversion circuit 14 that performs one of a charging operation and a discharging operation, the charging operation involving charging the battery member (12) by reducing the DC voltage output from the power supply (10), reversing the polarity of the reduced DC voltage, and outputting the resulting negative DC voltage to the virtual ground, the discharging operation involving causing the light-emitting body (13) to emit light by outputting a current to the positive electrode of the light-emitting body (13) on the basis of the DC voltage output from the positive electrode (12a) of the battery member (12).

Description

[Technical field]

[0001] The present disclosure relates to a strobe device and a driver monitoring system. [Background technology]

[0002] There is a strobe device that emits light when taking a picture with a camera. As such a strobe device, Patent Document 1 discloses one including a boost circuit, a charging circuit, a capacitor as a power storage member, an LED (Light Emitting Diode) as a light emitter, and an LED drive control circuit. The boost circuit boosts the voltage output from the power supply source. The charging circuit charges the capacitor with electrical energy by applying the voltage boosted by the boost circuit between both electrodes of the capacitor. After the capacitor is fully charged, the LED drive control circuit applies the voltage between both electrodes of the capacitor (hereinafter referred to as the "electrode-electrode voltage") to the LED, causing the LED to emit light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-47544 A Summary of the Invention [Problem to be solved by the invention]

[0004] The strobe device disclosed in Patent Document 1 had a problem in that in order to realize the charging operation for charging the capacitor and the discharging operation for illuminating the LED, it was necessary to have a boost circuit and a charging circuit separate from the LED drive control circuit.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a strobe device that can achieve a charging operation for charging a storage element and a discharging operation for illuminating an emitter, using only one DC conversion circuit. [Means for solving the problem]

[0006] The strobe device according to the present disclosure comprises: a storage member having a positive electrode and a negative electrode, the positive electrode of which is connected to a power supply source that outputs a DC voltage, and the negative electrode of which is connected to a virtual ground; an illuminant having an anode and a cathode, the cathode of which is connected to either ground or a virtual ground; and a DC conversion circuit that performs one of two operations: a charging operation in which the storage member is charged by stepping down the DC voltage output from the power supply source and outputting a negative voltage having the polarity of the stepped-down DC voltage inverted to the virtual ground; and a discharging operation in which the illuminant is illuminated by outputting a current to the anode of the illuminant based on the DC voltage output from the positive electrode of the storage member. Effect of the Invention

[0007] According to the present disclosure, a charging operation for charging an electricity storage member and a discharging operation for causing a light-emitting body to emit light can be realized by using only one DC conversion circuit. [Brief description of the drawings]

[0008] [Figure 1] 1 is a configuration diagram showing a driver monitoring system including a strobe device 2 according to a first embodiment. [Diagram 2] 1 is a configuration diagram showing a strobe device 2 according to a first embodiment. [Diagram 3] 2A to 2C are explanatory diagrams showing the charging and discharging operations of the strobe device 2. [Figure 4] 2 is a configuration diagram showing another strobe device 2 according to the first embodiment. FIG. [Diagram 5] 2 is a configuration diagram showing another strobe device 2 according to the first embodiment. FIG. [Figure 6] 2 is a configuration diagram showing another strobe device 2 according to the first embodiment. FIG. [Figure 7] 2 is a configuration diagram showing another strobe device 2 according to the first embodiment. FIG. [Figure 8] 1 is a configuration diagram showing a strobe device 2 according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In order to describe the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0010] Embodiment 1 FIG. 1 is a configuration diagram showing a driver monitoring system including a strobe device 2 according to the first embodiment. The driver monitoring system shown in FIG. 1 includes an imaging device 1, a strobe device 2, and a monitoring device 3. The photographing device 1 is realized by, for example, a CCD (Charge Coupled Device) camera or a CMOS (Complementary Metal Oxide Semiconductor) camera. The image capturing device 1 is installed, for example, on an instrument panel, a windshield, or a ceiling of a vehicle. The image capturing device 1 captures an image of an occupant when an image capturing command is output from the monitoring device 3, and outputs the captured image of the occupant to the monitoring device 3.

[0011] The strobe device 2 emits light when an occupant is photographed by the photographing device 1, based on a control signal from the monitoring device 3. The strobe device 2 emits light to make the occupant appear more clearly in the photographed image.

[0012] The monitoring device 3 controls the operations of the photographing device 1 and the strobe device 2. The monitoring device 3 monitors the driving state of the occupants, etc., based on the captured images output from the imaging device 1. The monitoring device 3 outputs a warning or the like to, for example, a vehicle control device (not shown) based on the monitoring result of the driving state, etc. The warning may indicate, for example, that the driver, who is an occupant, is dozing off while driving. 1 is implemented in a driver monitoring system. However, the strobe device 2 may be any device that emits light when an occupant is photographed by the photographing device 1, and is not limited to being implemented in a driver monitoring system.

[0013] FIG. 2 is a configuration diagram showing the strobe device 2 according to the first embodiment. The strobe device 2 shown in FIG. 2 includes a rectifying element 11 which is a switching element, a power storage member 12, a light emitter 13, a DC conversion circuit 14, and an operation switching circuit 16. In FIG. 2, the output terminal of the power supply source 10 is connected to the strobe device 2 . The power supply 10 supplies a DC voltage V BAT is output to the strobe device 2. The rectifying element 11 is realized by, for example, a reverse current prevention diode. The anode of the rectifier element 11 is connected to the output terminal of the power supply source 10 . The cathode of the rectifier element 11 is connected to the positive electrode 12a of the storage member 12 and the input terminal V of the DC conversion circuit 14. IN are connected to each of the The rectifier 11 converts the DC voltage V BAT to the DC conversion circuit 14, while preventing a reverse current from flowing from the positive electrode 12a of the electricity storage member 12 to the power supply source 10. The strobe device 2 shown in FIG. 2 includes a rectifier element 11 as a switching element. The DC voltage V BAT As long as it is possible to provide the DC conversion circuit 14 with the power while preventing reverse current from the positive electrode 12a of the storage member 12 to the power supply source 10, the rectifier element 11 is not limited to the rectifier element 11, and the strobe device 2 may be provided with, for example, a switch as an opening / closing element.

[0014] The electricity storage member 12 is realized by, for example, an electrolytic capacitor, a multilayer capacitor, or a storage battery. The electricity storage member 12 has a positive electrode 12a and a negative electrode 12b. The positive electrode 12a of the electricity storage member 12 is connected to the cathode of the rectifier element 11 and the input terminal V of the DC conversion circuit 14. IN are connected to each of the The negative electrode 12b of the electricity storage member 12 is connected to the output terminal V OUT , the operation switching circuit 16 and the virtual ground VGND.

[0015] The light emitter 13 is realized by, for example, an LED, a Vertical Cavity Surface Emitting Laser (VCSEL), or an infrared LED. The light emitter 13 has an anode and a cathode. The anode of the light emitter 13 is connected to the operation switching circuit 16. The anode of the light emitter 13 is connected to the output terminal V OUT and is connected. The cathode of the light emitter 13 is connected to the ground GND. When the light emitter 13 is realized, for example, by an LED, the anode of the light emitter 13 is the anode of the LED, and the cathode of the light emitter 13 is the cathode of the LED. The strobe device 2 shown in Fig. 2 includes one light emitter 13. However, this is merely an example, and the strobe device 2 may include, for example, a plurality of light emitters 13 connected in series. 2, the cathode of the light emitter 13 is connected to the ground GND. However, this is merely an example, and the cathode of the light emitter 13 may be connected to the virtual ground VGND.

[0016] The direct current conversion circuit 14 is realized by, for example, a step-down DC (Direct Current)-DC converter or a step-down switching regulator. The DC conversion circuit 14 has an input terminal V IN and output terminal VOUT It has. Input terminal V IN is connected to the output terminal of the power supply source 10 via a rectifier element 11. IN is connected to the positive electrode 12a of the electricity storage member 12. Output terminal V OUT is connected to the anode of the light emitter 13 and one end of a first switch 16a, which will be described later, via a shunt resistor 15a. The arrangement of the shunt resistor 15a shown in FIG. 2 is merely an example, and the shunt resistor 15a is not limited to this arrangement as long as it is present in the path of the current flowing through the light emitter 13. OUT is connected to the negative electrode 12b of the electricity storage member 12 and the virtual ground VGND via voltage dividing resistors 15b and 15c, respectively.

[0017] The DC conversion circuit 14 performs either a charging operation or a discharging operation. The charging operation is an operation for charging the electric energy required for the light emitting body 13 to emit light to the electricity storage member 12. Specifically, the ... BAT The polarity of the stepped-down DC voltage VN is inverted to produce a negative voltage −VN, which is then output to the virtual ground VGND, thereby charging the electricity storage member 12. The discharging operation is an operation for causing the light-emitting body 13 to emit light using the electric energy stored in the electricity storage member 12. Specifically, the DC voltage V BAT In the discharge operation, the DC conversion circuit 14 outputs a current to the anode of the light emitter 13 based on the DC voltage V BAT By performing constant current control for +VN, a constant current is supplied to the anode of the light emitter 13.

[0018] The DC conversion circuit 14 includes a high-side switch (hereinafter referred to as "SDH") 14a, a low-side switch (hereinafter referred to as "SDL") 14b, a choke coil 14c, a smoothing capacitor 14d, an error amplifier 14e, and a PWM (Pulse Width Modulation) control unit 14f. One end of the SDH14a is the input terminal V IN and is connected. The other end of the SDH 14a is connected to one end of the choke coil 14c and one end of the SDL 14b. One end of the SDL 14b is connected to the other end of the SDH 14a and one end of the choke coil 14c. The other end of SDL14b is connected to the virtual ground VGND.

[0019] One end of the choke coil 14c is connected to the other end of the SDH 14a and one end of the SDL 14b. The other end of the choke coil 14c is connected to one end of the smoothing capacitor 14d and the output terminal V OUT are connected to each of the The choke coil 14c is charged with electric energy when the SDH 14a is in a closed state and the SDL 14b is in an open state. The choke coil 14c discharges the electric energy stored therein when the SDH 14a is in an open state and the SDL 14b is in a closed state.

[0020] The SDH 14a and the SDL 14b alternately close based on the PWM signal output from the PWM control unit 14f. For example, when the signal level of the PWM signal is high, the SDH 14a closes and the SDL 14b opens. When the signal level of the PWM signal is low, the SDH 14a opens and the SDL 14b closes. The DC voltage V V from the DC converter 14 is determined according to the ratio of the period during which the signal level of the PWM signal is at a high level to the period during which the signal level of the PWM signal is at a low level. BAT The amount of blood pressure reduction is determined.

[0021] One end of the smoothing capacitor 14d is connected to the other end of the choke coil 14c and the output terminal V OUT are connected to each of the The other end of the smoothing capacitor 14d is connected to the virtual ground VGND. The smoothing capacitor 14d suppresses fluctuations in the stepped-down DC voltage VN output from the choke coil 14c.

[0022] The error amplifier 14e is connected to the voltage feedback terminal V FB , and has a current detection terminal V(-) and a current detection terminal V(+). Voltage feedback terminal V FB A divided voltage VD between voltage dividing resistors 15b and 15c is applied to the output terminal 15a as a voltage proportional to the stepped-down DC voltage VN. The voltage at one end of the shunt resistor 15a is applied to the current detection terminal V(-). The voltage at the other end of the shunt resistor 15a is applied to the current detection terminal V(+). For example, when a light emission control signal indicating that a charging operation is to be performed is received from the monitoring device 3 of the driver monitoring system, the error amplifier 14e detects the divided voltage VD and compares the divided voltage VD with the reference voltage V REF The error amplifier 14e detects the difference between the divided voltage VD and the reference voltage V REF Based on the difference between BAT The PWM control unit 14f outputs a PWM signal for controlling the step-down of the voltage. When a light emission control signal indicating that a discharge operation is to be performed is provided from the monitoring device 3, the error amplifier 14e detects the current flowing through the anode of the light emitter 13 from the voltage provided to the current detection terminal V(-) and the voltage provided to the current detection terminal V(+) and the resistance value RS of the shunt resistor 15a. The error amplifier 14e outputs a PWM signal to the PWM control unit 14f to make the current flowing through the anode of the light emitter 13 a constant current. In the error amplifier 14e, the resistance value RS of the shunt resistor 15a is a predetermined value. In the strobe device 2 shown in FIG. 2, the error amplifier 14e detects the divided voltage VD and calculates the ratio of the divided voltage VD to the reference voltage V REF However, this is merely an example. The error amplifier 14e detects the stepped-down DC voltage VN and calculates the difference between the DC voltage VN and the reference voltage V REF The difference between the two may be detected.

[0023] When a light emission control signal indicating that a charging operation is to be performed is received from the monitoring device 3, the PWM control unit 14f controls the opening and closing of the SDH 14a and the SDL 14b based on the PWM signal output from the error amplifier 14e, thereby increasing the DC voltage V BAT Controls the step-down of the When a light emission control signal indicating that a discharge operation is to be performed is received from the monitoring device 3, the PWM control unit 14f controls the opening and closing of the SDH 14a and the SDL 14b based on the PWM signal output from the error amplifier 14e, thereby discharging the output terminal V OUT The current flowing from the cathode to the anode of the light emitter 13 is controlled to be a constant current. 2, the DC conversion circuit 14 includes an error amplifier 14e and a PWM control unit 14f. However, this is merely an example, and the error amplifier 14e and the PWM control unit 14f may each be provided outside the DC conversion circuit 14.

[0024] The shunt resistor 15a is a resistor for detecting a current, and the resistance value of the shunt resistor 15a is RS. One end of the shunt resistor 15a is connected to the output terminal V OUT and a current detection terminal V(-) of the error amplifier 14e. The other end of the shunt resistor 15a is connected to a current detection terminal V(+) of the error amplifier 14e, the anode of the light emitter 13, and one end of a first switch 16a.

[0025] The voltage dividing resistor 15b is a resistor for dividing a voltage, and the resistance value of the voltage dividing resistor 15b is RB1. One end of the voltage dividing resistor 15b is connected to the output terminal V OUT and one end of the shunt resistor 15a. The other end of the voltage dividing resistor 15b is connected to the voltage feedback terminal V FB and one end of a voltage dividing resistor 15c. The voltage dividing resistor 15c is a resistor for dividing a voltage, and the resistance value of the voltage dividing resistor 15c is RB2. One end of the voltage dividing resistor 15c is connected to the voltage feedback terminal V FB and the other end of the voltage dividing resistor 15b. The other end of the voltage dividing resistor 15c is connected to the negative electrode 12b of the electricity storage member 12, the virtual ground VGND, and one end of the second switch 16b.

[0026] The operation switching circuit 16 includes a first switch 16a and a second switch 16b. For example, when a switch control signal indicating a charging operation or a switch control signal indicating a discharging operation is given from the monitoring device 3, the operation switching circuit 16 controls the opening and closing of each of the first switch 16a and the second switch 16b in accordance with the switch control signal. When the operation switching circuit 16 causes the DC conversion circuit 14 to perform a charging operation, the operation switching circuit 16 separates the negative electrode 12b of the electricity storage member 12 from the ground GND. When the operation switching circuit 16 causes the DC conversion circuit 14 to perform a discharging operation, the operation switching circuit 16 connects the negative electrode 12b of the electricity storage member 12 to the ground GND.

[0027] One end of the first switch 16a is connected to the output terminal V OUT In addition, one end of the first switch 16a is connected to the anode of the light emitter 13. The other end of the first switch 16a is connected to the ground GND. The first switch 16a is closed, for example, when the switch control signal output from the monitoring device 3 indicates that the DC conversion circuit 14 is to perform a charging operation, and is open, when the switch control signal output from the monitoring device 3 indicates that the DC conversion circuit 14 is to perform a discharging operation.

[0028] One end of the second switch 16b is connected to the negative electrode 12b of the electricity storage member 12, the virtual ground VGND, and the other end of the voltage dividing resistor 15c. The other end of the second switch 16b is connected to the ground GND. The second switch 16b is in an open state, for example, if the switch control signal output from the monitoring device 3 indicates that the DC conversion circuit 14 is to perform a charging operation, and is in a closed state if the switch control signal output from the monitoring device 3 indicates that the DC conversion circuit 14 is to perform a discharging operation.

[0029] Next, the strobe device 2 shown in FIG. 2 will be described. The strobe device 2 alternately performs, for example, a charging operation for charging the storage member 12 with the electrical energy required for the light emitter 13 to emit light, and a discharging operation for causing the light emitter 13 to emit light using the electrical energy stored in the storage member 12. FIG. 3 is an explanatory diagram showing the charging and discharging operations of the strobe device 2. As shown in FIG.

[0030] First, the operation of the flash device 2 when the DC conversion circuit 14 is performing a charging operation will be described. The power supply 10 supplies a DC voltage V BAT is output to the strobe device 2. The rectifier 11 of the strobe device 2 converts the DC voltage V BAT is provided to the DC conversion circuit 14. For example, the monitoring device 3 of the driver monitoring system outputs a light emission control signal indicating that a charging operation is to be performed to the DC conversion circuit 14, and outputs switch control signals indicating that a charging operation is to be performed to each of the first switch 16a and the second switch 16b. When a switch control signal indicating that a charging operation is to be performed is provided from the monitoring device 3, as shown in FIG. 3, the second switch 16b is opened (OFF) and then the first switch 16a is closed (ON).

[0031] When the second switch 16b is in an open state (OFF), the negative electrode 12b of the electricity storage member 12 is disconnected from the ground GND. When the negative electrode 12b of the electricity storage member 12 is disconnected from the ground GND, as described below, when a negative voltage -VN is applied to the negative electrode 12b of the electricity storage member 12, charging of the electricity storage member 12 becomes possible. When the first switch 16a is closed (ON), the anode of the light emitter 13 is connected to the ground GND. When the anode of the light emitter 13 is connected to the ground GND, the output terminal V OUT to DC voltage V dis is output, the light emitter 13 does not emit light.

[0032] The charging operation by the DC conversion circuit 14 will now be described in detail. The output terminal V of the DC conversion circuit 14 OUT The DC voltage V output from dis is divided by voltage dividing resistors 15b and 15c. The divided voltage VD by the voltage dividing resistors 15b and 15c is fed to the voltage feedback terminal V FB The divided voltage VD is expressed by the following equation (1).

[0033] TIFF0007665111000001.tif16166

[0034] When a light emission control signal indicating that a charging operation is to be performed is received from the monitoring device 3, the error amplifier 14e detects the divided voltage VD and compares the divided voltage VD with the reference voltage V REF Detect the difference between. The error amplifier 14e detects the divided voltage VD as the reference voltage V REF The divided voltage VD and the reference voltage V REF Based on the difference between BAT The PWM control unit 14f outputs a PWM signal for controlling the step-down of the voltage.

[0035] When a light emission control signal indicating that a charging operation is to be performed is received from the monitoring device 3, the PWM control unit 14f controls the opening and closing of the SDH 14a and the SDL 14b based on the PWM signal output from the error amplifier 14e, thereby increasing the DC voltage V BAT Controls the step-down of the The SDH 14a and the SDL 14b are alternately brought into the closed state based on a PWM signal output from a PWM control unit 14f.

[0036] When SDH14a is closed and SDL14b is open, the input terminal V IN DC voltage V applied to BAT This causes the choke coil 14c to be charged with electrical energy. After the choke coil 14c is charged with electric energy, when the SDH 14a is open and the SDL 14b is closed, the electric energy charged in the choke coil 14c is discharged as a current. At this time, the other end of the choke coil 14c is connected to the ground GND via the first switch 16a, so the potential of the other end of the choke coil 14c is 0 (V). Therefore, when a current flows from the choke coil 14c, the potential of the virtual ground VGND connected to one end of the choke coil 14c becomes negative. The potential of the virtual ground VGND gradually decreases from 0 (V) to -VN, as shown in Fig. 3. Since the negative electrode 12b of the electricity storage member 12 is connected to the virtual ground VGND, the electricity storage member 12 is charged by the potential of the virtual ground VGND. In Fig. 3, this charging is represented as "negative charging". -VN is determined by the ratio of the period during which the signal level of the PWM signal is at a high level to the period during which the signal level of the PWM signal is at a low level. VN is the voltage at the input terminal V IN DC voltage V applied to BAT It is a lower voltage than For example, if the ratio of high-level periods to low-level periods is 1:1, the stepped-down DC voltage VN is BAT If the ratio of high-level period to low-level period is 3:1, the DC voltage VN after step-down is half the DC voltage V BAT This is three-quarters of the total.

[0037] Here, the DC voltage V output from the power supply source 10 BAT may cause fluctuations. DC voltage VBAT If there is a fluctuation in the input terminal V IN DC voltage V applied to BAT The input terminal V IN DC voltage V applied to BAT As a result, the voltage between the electrodes of the electricity storage member 12, V BAT +VN also produces fluctuations. DC voltage V when fluctuations occur BAT +VN is the minimum value of V MIN When the fluctuation occurs, the DC voltage V BAT +VN is the maximum value of V MAX If so, the DC voltage V BAT The fluctuation range of +VN is the minimum value V MIN ~Maximum value V MAX It is. If the DC conversion circuit 14 cannot control the DC voltage VN, the electric storage member 12 cannot control the DC voltage V BAT +VN maximum value V MAX Higher withstand voltage V WITH It is necessary to adopt an electricity storage member having the above-mentioned structure. In the strobe device 2 shown in FIG. 2, the DC conversion circuit 14 can control the DC voltage VN, so the power storage member 12 is supplied with the DC voltage V BAT +VN maximum value V MAX Smaller withstand voltage V WITH It is possible to employ an electricity storage member having the following structure.

[0038] The reference voltage V when the error amplifier 14e detects the divided voltage VD REF is the input terminal V IN DC voltage V applied to BAT The withstand voltage V of the electricity storage member 12 WITH When the voltage feedback terminal V FB The error amplifier 14e detects the stepped-down DC voltage VN and calculates the DC voltage VN and the reference voltage V REF When detecting the difference with the reference voltage V REF is the input terminal V IN DC voltage V applied to BAT The withstand voltage V of the electricity storage member 12WITH When the voltage DM of the design margin is lower than the OUT is the stepped-down DC voltage VN output from During charging, the voltage VD is equal to the reference voltage V REF If it is higher than the DC voltage V BAT +VN is the withstand voltage V WITH Therefore, the error amplifier 14e reduces the duty ratio of the PWM signal output to the PWM control unit 14f to lower the voltage VN. As a result, the DC voltage V BAT +VN is the voltage (V WITH -DM) will be lower. Voltage VD is the reference voltage V REF If it is less than or equal to the DC voltage V BAT +VN is the withstand voltage V WITH Since the duty ratio of the PWM signal cannot be higher than 1, the error amplifier 14e maintains the duty ratio of the PWM signal.

[0039] For example, DC voltage V BAT The nominal voltage is 12 (V), and the DC voltage V BAT The maximum value of is 16(V), DC voltage V BAT is 8 (V), and the voltage VN is 15 (V). For simplicity of explanation, the forward saturation voltage of the rectifying element 11 is ignored here. DC voltage V BAT When the voltage V T fluctuates to a maximum value, the inter-electrode voltage VT of the electricity storage member 12 is expressed by the following equation (2). VT = DC voltage V BAT Maximum value of + voltage VN =16+15=31(V) (2) DC voltage V BAT When fluctuates to a minimum value, the inter-electrode voltage VT of electricity storage member 12 is as shown in the following equation (3). VT = DC voltage V BAT Minimum value of + voltage VN =8+15=23(V) (3) DC voltage V BATWhen is the nominal voltage, the inter-electrode voltage VT of the electricity storage member 12 is expressed by the following equation (4). VT = DC voltage V BAT Nominal voltage + voltage VN =12+15=27(V) (4)

[0040] DC voltage V BAT When the voltage V V fluctuates, the voltage V V between the electrodes of the storage member 12 is BAT Therefore, if the DC conversion circuit 14 cannot control the DC voltage VN, the electric storage member 12 cannot withstand a withstand voltage V that is equal to or higher than the electrode-to-electrode voltage VT shown in the formula (2). WITH Specifically, the electricity storage member 12 must have a withstand voltage V of 31 (V) or more. WITH When the voltage DM of the design margin is taken into consideration, if the voltage DM of the design margin is, for example, 2 (V), the electricity storage member 12 must have a withstand voltage V WITH It is necessary to adopt a storage member having the above-mentioned structure.

[0041] In the strobe device 2 shown in FIG. 2, the DC conversion circuit 14 can control the DC voltage VN. BAT When the voltage between both electrodes of the electricity storage member 12 fluctuates, for example, the DC voltage V BAT If the DC conversion circuit 14 controls the DC voltage VN so that it is the same as the electrode-to-electrode voltage VT when the nominal voltage is 1 V, the electricity storage member 12 has a withstand voltage V WITH Specifically, the electricity storage member 12 has a withstand voltage V of 27 (V) or more. WITH When the voltage DM of the design margin is taken into consideration, if the voltage DM of the design margin is, for example, 2 (V), the electricity storage member 12 should have a withstand voltage V WITH It is only necessary to employ an electricity storage member having the above structure. This is just one example. According to the strobe device 2 shown in FIG. 5, the DC voltage V BATEven if the charging voltage V applied to the electricity storage member 12 fluctuates to or above the maximum value, IN It is possible to fix the withstand voltage of the capacitor and use a capacitor member with a lower withstand voltage.

[0042] In the strobe device disclosed in Patent Document 1, it is assumed that the voltage output from the power supply source may fluctuate. If the nominal voltage of the voltage output from the power supply source is 12 (V), the maximum value of the voltage when the voltage output from the power supply source fluctuates is 16 (V), and the boosted voltage by the boost circuit is 15 (V), the voltage between both electrodes of the capacitor will be a maximum of 31 (V). For this reason, it is necessary to adopt a capacitor having a withstand voltage of 31 (V) or more as the capacitor used as the electricity storage member. When considering the design margin voltage DM, if the design margin voltage is, for example, 2 (V), it is necessary to adopt a capacitor having a withstand voltage of 33 (V) or more as the capacitor used as the electricity storage member.

[0043] Next, the operation of the strobe device 2 when the DC conversion circuit 14 is performing a discharging operation will be described. For example, the monitoring device 3 of the driver monitoring system outputs a light emission control signal indicating that a discharge operation is to be performed to the DC conversion circuit 14, and outputs switch control signals indicating that a discharge operation is to be performed to each of the first switch 16a and the second switch 16b. When a switch control signal indicating that a discharge operation is to be performed is provided from the monitoring device 3, as shown in FIG. 3, the first switch 16a is opened (OFF) and then the second switch 16b is closed (ON).

[0044] When the first switch 16a is opened (OFF), the anode of the light emitter 13 is disconnected from the ground GND. When the anode of the light emitter 13 is disconnected from the ground GND, the output terminal V OUT The voltage output from the output terminal is applied to the anode of the light emitter 13. As a result, the light emitter 13 is enabled to emit light. When the second switch 16b is in a closed state (ON), the negative electrode 12b of the electricity storage member 12 and the virtual ground VGND are each connected to the ground GND. When the negative electrode 12b of the electricity storage member 12 and the virtual ground VGND are each connected to the ground GND, the potential of the virtual ground VGND and the potential of the negative electrode 12b of the electricity storage member 12 are each raised from -VN to 0 (V). As a result, the potential of the positive electrode 12a of the electricity storage member 12 is raised to V BAT From V BAT +VN. This causes the input terminal V IN V BAT +VN is applied.

[0045] The output terminal V of the DC conversion circuit 14 OUT The DC voltage V output from dis is applied to shunt resistor 15a. At this time, the voltage at one end of the shunt resistor 15a is applied to the current detection terminal V(-) of the error amplifier 14e. The voltage at the other end of the shunt resistor 15a is applied to a current detection terminal V(+) of the error amplifier 14e. When a light emission control signal indicating that a discharge operation is to be performed is given from the monitoring device 3, the error amplifier 14e detects the current I flowing through the anode of the light-emitting body 13 from the voltage given to the current detection terminal V(-), the voltage given to the current detection terminal V(+), and the resistance value RS of the shunt resistor 15a. The error amplifier 14e outputs a PWM signal to the PWM control unit 14f to make the current I flowing through the anode of the light emitter 13 a constant current.

[0046] When a light emission control signal indicating that a discharge operation is to be performed is received from the monitoring device 3, the PWM control unit 14f controls the opening and closing of the SDH 14a and the SDL 14b based on the PWM signal output from the error amplifier 14e, thereby discharging the output terminal V OUT A constant current control is performed so that the current I flowing from the cathode to the anode of the light emitter 13 is kept constant. The output terminal V of the DC conversion circuit 14 OUT When a constant current is supplied to the anode of the light emitter 13 from the cathode, the light emitter 13 emits light.

[0047] In the above-described first embodiment, the strobe device 2 is configured to include the power supply source 10 having a positive electrode 12a and a negative electrode 12b, the positive electrode 12a being connected to the power supply source 10 that outputs a DC voltage, and the negative electrode 12b being connected to the virtual ground, the light emitter 13 having an anode and a cathode, the cathode of which is connected to either the ground or the virtual ground, and the DC conversion circuit 14 that performs one of the following operations: a charging operation for charging the power storage member 12 by stepping down the DC voltage output from the power supply source 10 and outputting a negative voltage obtained by inverting the polarity of the stepped-down DC voltage to the virtual ground, and a discharging operation for causing the light emitter 13 to emit light by outputting a current to the anode of the light emitter 13 based on the DC voltage output from the positive electrode 12a of the power storage member 12. Thus, the strobe device 2 can realize the charging operation for charging the power storage member 12 and the discharging operation for causing the light emitter 13 to emit light with only one DC conversion circuit 14.

[0048] In the first embodiment, the strobe device 2 is configured so that the DC conversion circuit 14 detects a voltage proportional to the stepped-down DC voltage, and steps down the DC voltage output from the power supply source 10 based on the difference between the detected voltage and the reference voltage. Therefore, even if the voltage output from the power supply source 10 fluctuates to be higher than the nominal voltage, the strobe device 2 can use an electricity storage member having a withstand voltage lower than the withstand voltage required when the voltage output from the power supply source 10 is higher than the nominal voltage.

[0049] In the strobe device 2 shown in Fig. 2, the power supply source 10 is connected to the DC conversion circuit 14 via the rectifier element 11. However, this is merely an example, and in addition to the power supply source 10 being connected to the DC conversion circuit 14 via the rectifier element 11, a path 11a may be provided that directly connects the power supply source 10 to the DC conversion circuit 14, as shown in Fig. 4. Fig. 4 is a configuration diagram showing another strobe device 2 according to embodiment 1. In Fig. 4, the same reference numerals as in Fig. 2 denote the same or corresponding parts, and detailed description thereof will be omitted. By providing the path 11a, the positive electrode 12a of the electricity storage member 12 and the input terminal V of the DC conversion circuit 14 may be disconnected due to factors such as deterioration of the electricity storage member 12 over time. IN Even if the voltage output to the DC converter 14 drops, the strobe device 2 can emit light from the light emitter 13. Specifically, IN When the voltage output to the power supply source 10 drops, the DC conversion circuit 14 converts the DC voltage V BAT and the DC voltage output from the positive electrode 12a of the electricity storage member 12 to generate an output voltage having a potential required for the light emission of the light-emitting body 13. Then, the DC conversion circuit 14 supplies a current to the anode of the light-emitting body 13 based on the output voltage, thereby causing the light-emitting body 13 to emit light.

[0050] In the strobe device 2 shown in FIG. OUT The divided voltage VD by the voltage dividing resistor 15b, one end of which is connected to the voltage dividing resistor 15c, is fed to the voltage feedback terminal V FB However, this is only one example. As shown in Figure 5, IN The voltage applied to the error amplifier 14e is divided by the voltage dividing resistors 15b' and 15c, and the divided voltage VD' is fed to the voltage feedback terminal V FB One end of the voltage dividing resistor 15b′ may be connected to the input terminal V IN and the other end of the voltage dividing resistor 15b' is connected to one end of the voltage dividing resistor 15c. Fig. 5 is a configuration diagram showing another strobe device 2 according to embodiment 1. In Fig. 5, the same reference numerals as in Fig. 2 denote the same or corresponding parts, and detailed description thereof will be omitted.

[0051] In this case, the error amplifier 14e is connected to the voltage feedback terminal V FB The voltage VD' given to the reference voltage V REF Compare with. The voltage VD' is the input terminal V IN This is the divided voltage VPS applied between the VPS pin and the virtual ground VGND. In this case, V disis the input terminal V IN and the virtual ground VGND, and corresponds to the electrode-to-electrode voltage VT of the electricity storage member 12 in equation (2) and thereafter. Since the PWM control unit 14f performs constant voltage control on the voltage VPS, the voltage VPS is expressed by the following equation (5). VPS = VT = Step-down setting voltage VN (5) For example, when the step-down setting voltage VN is 27 (V), the charging voltage is also 27 (V), and the voltage V BAT is charged to 16 (V), the voltage on the negative electrode 12b side of the electricity storage member 12 changes to 27-16=11 (V). At this time, since the inter-electrode voltage VT is fixed, the withstand voltage V WITH is 27(V) + the design margin DM. Voltage VD' is the reference voltage V REF If the voltage VN is higher than the voltage (V WITH -DM) will be lower. Voltage VD' is the reference voltage V REF If it is attenuated below this value, the error amplifier 14e increases the duty ratio of the PWM signal to increase the step-down setting voltage VN.

[0052] In the strobe device 2 shown in Fig. 2, the cathode of the light emitter 13 is connected to the ground GND. However, this is merely an example, and the cathode of the light emitter 13 may be connected to the virtual ground VGND via a shunt resistor 15a as shown in Fig. 6. Fig. 6 is a configuration diagram showing another strobe device 2 according to embodiment 1. In Fig. 6, the same reference numerals as in Fig. 2 denote the same or corresponding parts, and detailed description thereof will be omitted. The strobe device 2 shown in FIG. 6 includes a switch 15e and a switch 15f. One end of the switch 15e is connected to one end of the shunt resistor 15a and the other end of the switch 15f. The other end of the switch 15e is connected to the voltage feedback terminal V FB, and is connected to the other end of the voltage dividing resistor 15b and one end of the voltage dividing resistor 15c. One end of the switch 15 f is connected to the cathode of the light emitter 13 . The other end of the switch 15f is connected to one end of the shunt resistor 15a and one end of the switch 15e. In the strobe device 2 shown in Fig. 6, the switch 15f is connected between the cathode of the light emitter 13 and one end of the shunt resistor 15a. The switch 15f only needs to be present in the path of the current flowing through the light emitter 13. For example, OUT and the anode of the light emitter 13, or between the other end of the shunt resistor 15a and the virtual ground VGND.

[0053] 6, one end of the shunt resistor 15a is connected to the cathode of the light emitter 13 via a switch 15f, and one end of the shunt resistor 15a is connected to one end of a switch 15e. The other end of the shunt resistor 15a is connected to the negative electrode 12b of the electricity storage member 12, the virtual ground VGND, one end of the second switch 16b, and the other end of the voltage dividing resistor 15c. When a switch control signal indicating that a charging operation is to be performed is provided from the monitoring device 3, the switch 15e is opened (OFF), and the switch 15f is opened (OFF). In this case, similar to the strobe device 2 shown in FIG. 2, the divided voltage VD by the voltage dividing resistors 15b and 15c is fed to the voltage feedback terminal V FB is applied to

[0054] When a switch control signal indicating that a discharge operation is to be performed is provided from the monitoring device 3, the switch 15e is closed (ON) and the switch 15f is closed (ON). In this case, the voltage at one end of the shunt resistor 15a is fed to the voltage feedback terminal V FBWhen performing a discharge operation, the second switch 16b is closed (ON), and therefore the voltage at the other end of the shunt resistor 15a is 0 (V). Therefore, if the voltage at one end of the shunt resistor 15a is known, the error amplifier 14e can detect the current I flowing through the light emitter 13 from the voltage at one end of the shunt resistor 15a and the resistance value RS of the shunt resistor 15a. The resistance value RB1 of the voltage-dividing resistor 15b and the resistance value RB2 of the voltage-dividing resistor 15c are each much larger than the resistance value RS of the shunt resistor 15a. Therefore, the error amplifier 14e is hardly affected by the voltage-dividing resistors 15b and 15c, and can detect the voltage at one end of the shunt resistor 15a to detect the current I flowing through the light-emitting body 13.

[0055] In the strobe device 2 shown in Fig. 6, the cathode of the light emitter 13 is connected to the virtual ground VGND via a shunt resistor 15a. However, this is merely an example, and the cathode of the light emitter 13 may be connected to the ground GND via a shunt resistor 15a as shown in Fig. 7. Fig. 7 is a configuration diagram showing another strobe device 2 according to embodiment 1. In Fig. 7, the same reference numerals as in Fig. 2 and Fig. 6 indicate the same or corresponding parts, and detailed description thereof will be omitted.

[0056] Embodiment 2 In the second embodiment, a strobe device in which the light emitter 13 emits light with an inverted output will be described. Fig. 8 is a configuration diagram showing a strobe device 2 according to embodiment 2. In Fig. 8, the same reference numerals as in Fig. 2 denote the same or corresponding parts, and detailed description thereof will be omitted. The strobe device 2 shown in FIG. 8 includes a rectifier element 11, a power storage member 12, a light emitter 13, a DC conversion circuit 14, and an operation switching circuit 17.

[0057] In the strobe device 2 shown in FIG. 8, the anode of the light emitter 13 is connected to the ground GND, and the cathode of the light emitter 13 is connected to the virtual ground VGND via a shunt resistor 15a and a switch 17a, which will be described later. The DC conversion circuit 14 converts the input voltage V IN The DC voltage V BAT Reduce the voltage. The DC conversion circuit 14 has an output terminal V OUT Then, a negative voltage −VN obtained by inverting the polarity of the stepped-down DC voltage is output to the negative electrode 12b of the electricity storage member 12, the virtual ground VGND, and the operation switching circuit 17, respectively.

[0058] The operation switching circuit 17 includes a switch 17a. The operation switching circuit 17 controls the opening and closing of the switch 17a, for example, when a switch control signal indicating that the storage member 12 is to be charged or a switch control signal indicating that the light-emitting body 13 is to be illuminated is given from the monitoring device 3 of the driver monitoring system. When the electricity storage member 12 is charged, the operation switching circuit 17 separates the cathode of the light emitting body 13 from the virtual ground VGND. When the light emitter 13 is caused to emit light, the operation switching circuit 17 connects the cathode of the light emitter 13 to the virtual ground VGND via the shunt resistor 15a.

[0059] One end of the switch 17a is electrically connected to the cathode of the light emitter 13. That is, one end of the switch 17a is connected to the cathode of the light emitter 13 via the shunt resistor 15a. The other end of the switch 17a is connected to the negative electrode 12b of the electricity storage member 12, the virtual ground VGND, and the other end of the voltage dividing resistor 15c. The switch 17a is in an open state (OFF) if the switch control signal output from the monitoring device 3 indicates that the storage member 12 is to be charged, and is in a closed state (ON) if the switch control signal output from the monitoring device 3 indicates that the light-emitting body 13 is to be illuminated.

[0060] First, the operation of the flash device 2 when the DC conversion circuit 14 is performing a charging operation will be described. The power supply 10 supplies a DC voltage V BAT is output to the strobe device 2. The rectifier 11 of the strobe device 2 converts the DC voltage V BAT is provided to the DC conversion circuit 14. For example, the monitoring device 3 of the driver monitoring system outputs a light emission control signal indicating that a charging operation is to be performed to the DC conversion circuit 14, and outputs a switch control signal indicating that a charging operation is to be performed to the switch 17a. When a switch control signal indicating that a charging operation is to be performed is provided from the monitoring device 3, the switch 17a is opened (OFF).

[0061] When the switch 17a is in the open state (OFF), the cathode of the light-emitting body 13 is disconnected from the virtual ground VGND. When the cathode of the light-emitting body 13 is disconnected from the virtual ground VGND, a negative voltage is not applied to the cathode of the light-emitting body 13, and therefore the light-emitting body 13 does not emit light. Furthermore, when the cathode of the light-emitting body 13 is disconnected from the virtual ground VGND and a negative voltage −VN is applied to the negative electrode 12b of the electricity storage member 12, charging of the electricity storage member 12 becomes possible.

[0062] The charging operation by the DC conversion circuit 14 will now be described in detail. The output terminal V of the DC conversion circuit 14 OUT The DC voltage V output from dis is divided by voltage dividing resistors 15b and 15c. The divided voltage VD by the voltage dividing resistors 15b and 15c is fed to the voltage feedback terminal V FB The divided voltage VD is expressed as in equation (1).

[0063] When a light emission control signal indicating that a charging operation is to be performed is received from the monitoring device 3, the error amplifier 14e detects the divided voltage VD and compares the divided voltage VD with the reference voltage V REF Detect the difference between. The error amplifier 14e detects the divided voltage VD as the reference voltage V REF The divided voltage VD and the reference voltage V REF Based on the difference between BATThe PWM control unit 14f outputs a PWM signal for controlling the step-down of the voltage. In the strobe device 2 shown in FIG. 8, the error amplifier 14e detects the divided voltage VD and calculates the ratio of the divided voltage VD to the reference voltage V REF However, this is merely an example. The error amplifier 14e detects the stepped-down DC voltage VN and calculates the difference between the DC voltage VN and the reference voltage V REF The difference between the two may be detected.

[0064] When a light emission control signal indicating that a charging operation is to be performed is received from the monitoring device 3, the PWM control unit 14f controls the opening and closing of the SDH 14a and the SDL 14b based on the PWM signal output from the error amplifier 14e, thereby increasing the DC voltage V BAT Controls the step-down of the The SDH 14a and the SDL 14b are alternately brought into the closed state based on a PWM signal output from a PWM control unit 14f.

[0065] When SDH14a is closed and SDL14b is open, the input terminal V IN DC voltage V applied to BAT This causes the choke coil 14c to be charged with electrical energy. After the choke coil 14c is charged with electrical energy, when the SDH 14a is open and the SDL 14b is closed, the electrical energy charged in the choke coil 14c is discharged as a current. At this time, the other end of the choke coil 14c is connected to the ground GND, so the potential of the other end of the choke coil 14c is 0 (V). Therefore, when a current flows from the choke coil 14c, the potential of the virtual ground VGND connected to one end of the choke coil 14c becomes negative. The potential of the virtual ground VGND gradually decreases from 0 (V) to −VN. Since the negative electrode 12b of the electricity storage member 12 is connected to the virtual ground VGND, the electricity storage member 12 is charged by the potential of the virtual ground VGND.

[0066] Here, the DC voltage V output from the power supply source 10 BAT may cause fluctuations. DC voltage V BAT If there is a fluctuation in the input terminal V IN DC voltage V applied to BAT The input terminal V IN DC voltage V applied to BAT As a result, the voltage between the electrodes of the electricity storage member 12, V BAT +VN also produces fluctuations. DC voltage V when fluctuations occur BAT +VN is the minimum value of V MIN When the fluctuation occurs, the DC voltage V BAT +VN is the maximum value of V MAX If so, the DC voltage V BAT The fluctuation range of +VN is the minimum value V MIN ~Maximum value V MAX It is. If the DC conversion circuit 14 cannot control the DC voltage VN, the electric storage member 12 cannot control the DC voltage V BAT +VN maximum value V MAX Higher withstand voltage V WITH It is necessary to adopt an electricity storage member having the above-mentioned structure. In the strobe device 2 shown in FIG. 8, the DC conversion circuit 14 can control the DC voltage VN, so that the power storage member 12 is supplied with the DC voltage V BAT +VN maximum value V MAX Smaller withstand voltage V WITH It is possible to employ an electricity storage member having the following structure.

[0067] The reference voltage V when the error amplifier 14e detects the divided voltage VD REF is the input terminal V IN DC voltage V applied to BAT The withstand voltage V of the electricity storage member 12 WITH When the voltage feedback terminal V FB The error amplifier 14e detects the stepped-down DC voltage VN and calculates the DC voltage VN and the reference voltage V REF When detecting the difference with the reference voltage VREF is the input terminal V IN DC voltage V applied to BAT The withstand voltage V of the electricity storage member 12 WITH When the voltage DM of the design margin is lower than the OUT is the stepped-down DC voltage VN output from During charging, the voltage VD is equal to the reference voltage V REF If it is higher than the DC voltage V BAT +VN is the withstand voltage V WITH Therefore, the error amplifier 14e reduces the duty ratio of the PWM signal output to the PWM control unit 14f to lower the voltage VN. As a result, the DC voltage V BAT +VN is the voltage (V WITH -DM) will be lower. Voltage VD is the reference voltage V REF If it is less than or equal to the DC voltage V BAT +VN is the withstand voltage V WITH Since the duty ratio of the PWM signal cannot be higher than 1, the error amplifier 14e maintains the duty ratio of the PWM signal.

[0068] Next, the operation of the strobe device 2 when the DC conversion circuit 14 is performing a discharging operation will be described. For example, the monitoring device 3 of the driver monitoring system outputs a light emission control signal indicating that a discharging operation is to be performed to the DC conversion circuit 14, and outputs a switch control signal indicating that a discharging operation is to be performed to the switch 17a. When a switch control signal indicating that a discharging operation is to be performed is given from the monitoring device 3, the switch 17a is brought into a closed state (ON).

[0069] When the switch 17a is in a closed state (ON), the cathode of the light emitter 13 is connected to the virtual ground VGND via the shunt resistor 15a. The cathode of the light-emitting body 13 is connected to the virtual ground VGND via the shunt resistor 15a, whereby the negative electrode 12b of the electricity storage member 12 is electrically connected to the cathode of the light-emitting body 13. The negative electrode 12b of the electricity storage member 12 is electrically connected to the cathode of the light-emitting body 13, whereby a negative voltage -VN is applied to the cathode of the light-emitting body 13, enabling the light-emitting body 13 to emit light.

[0070] At this time, the voltage at one end of the shunt resistor 15a is applied to the current detection terminal V(-) of the error amplifier 14e. The voltage at the other end of the shunt resistor 15a is applied to a current detection terminal V(+) of the error amplifier 14e. When a light emission control signal indicating that a discharge operation is to be performed is given from the monitoring device 3, the error amplifier 14e detects the current I flowing through the light-emitting body 13 from the voltage given to the current detection terminal V(-) and the voltage given to the current detection terminal V(+) and the resistance value RS of the shunt resistor 15a. The error amplifier 14e outputs a PWM signal to the PWM control unit 14f for making the current I flowing through the light emitter 13 a constant current.

[0071] When a light emission control signal indicating that a discharge operation is to be performed is received from the monitoring device 3, the PWM control unit 14f controls the opening and closing of the SDH 14a and the SDL 14b based on the PWM signal output from the error amplifier 14e, thereby discharging the output terminal V OUT The current I flowing from the light emitting element 13 is controlled to be a constant current. The output terminal V of the DC conversion circuit 14 OUT A constant current is supplied to the light emitter 13 from the power supply 11, causing the light emitter 13 to emit light.

[0072] In the above-described second embodiment, the strobe device 2 is configured to include a power supply source 10 having a positive electrode 12a and a negative electrode 12b, the positive electrode 12a being connected to the power supply source 10 that outputs a DC voltage, and the negative electrode 12b being connected to a virtual ground, a light emitter 13 having an anode and a cathode and connected to a ground and an anode, and a DC conversion circuit 14 that performs one of the following operations: a charging operation for charging the power storage member 12 by stepping down the DC voltage output from the power supply source 10 and outputting a negative voltage obtained by inverting the polarity of the stepped-down DC voltage to the virtual ground, and a discharging operation for causing the light emitter 13 to emit light by outputting a current to the cathode of the light emitter 13 based on the negative voltage obtained by inverting the polarity of the DC voltage output from the positive electrode 12a of the power storage member 12. Thus, the strobe device 2 can realize a charging operation for charging the power storage member 12 and a discharging operation for causing the light emitter 13 to emit light with only one DC conversion circuit 14.

[0073] In the second embodiment, the strobe device 2 is configured so that the DC conversion circuit 14 detects a voltage proportional to the stepped-down DC voltage, and steps down the DC voltage output from the power supply source 10 based on the difference between the detected voltage and the reference voltage. Therefore, even if the voltage output from the power supply source 10 fluctuates to be higher than the nominal voltage, the strobe device 2 can use an electricity storage member having a withstand voltage lower than the withstand voltage required when the voltage output from the power supply source 10 is higher than the nominal voltage.

[0074] In addition, the present disclosure allows free combination of the respective embodiments, modification of any of the components of each embodiment, or omission of any of the components of each embodiment. [Industrial Applicability]

[0075] The present disclosure is suitable for strobe devices and driver monitoring systems. [Explanation of symbols]

[0076] 1 photographing device, 2 strobe device, 3 monitoring device, 10 power supply source, 11 rectifying element (switching element), 11a path, 12 power storage member, 12a anode, 12b negative electrode, 13 light emitting body, 14 DC conversion circuit, 14a SDH, 14b SDL, 14c choke coil, 14d smoothing capacitor, 14e error amplifier, 14f PWM control unit, 15a shunt resistor, 15b, 15b' voltage dividing resistor, 15c voltage dividing resistor, 15e, 15f switch, 16 operation switching circuit, 16a first switch, 16b second switch, 17 operation switching circuit, 17a switch.

Claims

1. an electricity storage member having a positive electrode and a negative electrode, the positive electrode being connected to a power supply source that outputs a DC voltage, and the negative electrode being connected to a virtual ground; a light emitter having an anode and a cathode, the cathode being connected to either a ground or the virtual ground; a DC conversion circuit that performs one of a charging operation for charging the electricity storage member by stepping down a DC voltage output from the power supply source and outputting a negative voltage obtained by inverting the polarity of the stepped-down DC voltage to the virtual ground, and a discharging operation for causing the light-emitting body to emit light by outputting a current to the anode of the light-emitting body based on the DC voltage output from the positive electrode of the electricity storage member; A strobe device equipped with

2. The DC conversion circuit includes:

2. The strobe device according to claim 1, further comprising: a step-down DC voltage detecting means for detecting a voltage proportional to the stepped-down DC voltage; and a step-down of the DC voltage output from the power supply source based on a difference between the detected voltage and a reference voltage.

3. 2. The strobe device according to claim 1, further comprising an operation switching circuit which disconnects the negative electrode of the storage member from the ground when the DC conversion circuit is caused to perform the charging operation, and connects the negative electrode of the storage member to the ground when the DC conversion circuit is caused to perform the discharging operation.

4. The DC conversion circuit includes: the input terminal is connected to the power supply source and the positive electrode of the storage member, and the output terminal is connected to the anode of the light emitter, the negative electrode of the storage member, and the virtual ground, a charging operation is performed by the operation switching circuit when the negative electrode of the electricity storage member is disconnected from the ground, in which the DC voltage output from the power supply source to the input terminal is stepped down, and a negative voltage having a polarity that is inverted from the stepped-down DC voltage is output from the output terminal to the virtual ground; The strobe device according to claim 3, characterized in that when the negative electrode of the storage member is connected to the ground, the operation switching circuit performs constant current control on the DC voltage output from the positive electrode of the storage member to the input terminal, thereby performing a discharge operation in which a constant current is output from the output terminal to the anode of the light-emitting body.

5. The operation switching circuit includes: a first switch having one end connected to the output end of the DC conversion circuit and the other end connected to the ground, the first switch being in a closed state when the DC conversion circuit is caused to perform the charging operation and being in an open state when the DC conversion circuit is caused to perform the discharging operation; 5. The strobe device according to claim 4, further comprising a second switch having one end connected to the negative electrode of the storage member and the virtual ground and the other end connected to the ground, the second switch being open when the DC conversion circuit is caused to perform the charging operation and being closed when the DC conversion circuit is caused to perform the discharging operation.

6. 5. The strobe device according to claim 4, further comprising an opening / closing element connected between the positive terminal of the storage member and the input terminal of the DC conversion circuit and the power supply source, for preventing reverse current from the positive terminal of the storage member to the power supply source.

7. 2. The strobe device according to claim 1, wherein when said DC conversion circuit is performing said discharging operation, the current output from said DC conversion circuit to the anode of said light emitter is a constant current.

8. an electricity storage member having a positive electrode and a negative electrode, the positive electrode being connected to a power supply source that outputs a DC voltage, and the negative electrode being connected to a virtual ground; a light emitter having an anode and a cathode, the anode being connected to a ground; a DC conversion circuit that performs one of a charging operation for charging the storage member by stepping down a DC voltage output from the power supply source and outputting a negative voltage obtained by inverting the polarity of the stepped-down DC voltage to the virtual ground, and a discharging operation for causing the light-emitting body to emit light by outputting a current to the cathode of the light-emitting body based on the negative voltage obtained by inverting the polarity of the DC voltage output from the positive electrode of the storage member; A strobe device equipped with

9. The DC conversion circuit includes:

9. The strobe device according to claim 8, further comprising: detecting either the stepped-down DC voltage or a voltage proportional to the stepped-down DC voltage; and stepping down the DC voltage output from the power supply source based on a difference between the detected voltage and a reference voltage.

10. 10. The strobe device according to claim 9, further comprising an operation switching circuit which disconnects the cathode of the light-emitting element from the virtual ground when the DC conversion circuit is caused to perform the charging operation, and connects the cathode of the light-emitting element to the virtual ground when the DC conversion circuit is caused to perform the discharging operation.

11. The operation switching circuit includes: The strobe device according to claim 10, further comprising a switch having one end connected to the cathode of the light-emitting body and the other end connected to the virtual ground, the switch being closed when the DC conversion circuit is caused to perform the charging operation, and being closed when the DC conversion circuit is caused to perform the discharging operation.

12. A driver monitoring system for monitoring the state of a vehicle occupant, The driver monitoring system includes: An imaging device for imaging the occupant; a strobe device that emits light when the passenger is photographed by the photographing device, The driver monitoring system, wherein the strobe device is the strobe device according to any one of claims 1 to 11.

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