JP4277643B2 - Indicator light device with multiple LEDs - Google Patents

Description

  The present invention relates to a display lamp device that performs display with a plurality of LEDs and can detect a disconnection of a line that supplies power to the plurality of LEDs (hereinafter referred to as an LED line).

  Conventionally, what is shown in FIG. 6 is known as a circuit configuration of an indicator lamp device with a disconnection detection function used as a vehicular direction indicator. In this circuit, a voltage value obtained by dividing the voltage V of the battery 100 by the Zener diode ZD1, the resistor R6, and the resistor R7 is set as the threshold voltage Vth. When one of the incandescent lamps 101 and 102 arranged at the front and rear positions of the vehicle is disconnected, the value of the current flowing through the shunt resistor R8 becomes small, so the amount of voltage drop at the shunt resistor R8 is small. Become. Therefore, the magnitude of the voltage drop amount at the shunt resistor R8 (that is, the voltage value between the shunt resistor R8 and the incandescent lamps 101 and 102) and the threshold voltage Vth between the state before the disconnection and the state after the disconnection are large. Is switched so that the output level from the comparator 103 is changed so that disconnection of the incandescent lamps 101 and 102 can be detected.

  On the other hand, in recent years, in order to save power in an indicator lamp device such as a direction indicator used in a vehicle, it is considered to display the indicator by light emitted from an LED instead of an incandescent lamp (for example, Patent Document 1). In this case, since one LED has a small amount of light emission, a plurality of LEDs are arranged so as to have a desired brightness.

  FIG. 7 shows a circuit diagram of the indicator lamp device when a plurality of LEDs 110 are arranged. As shown in this figure, LED lines in which n LEDs 110 and resistors 111 are connected in series are connected in parallel for m columns, and power is supplied from a battery 112 to these columns.

  In such a circuit configuration, the voltage of the battery 112 is V, the current flowing from the battery 112 to the indicator lamp device is I, the current flowing through each line arranged in m columns is I1, the resistance value of the resistor R is R, Assuming that the voltage drop amount at each LED 110 is Vf, I1 and I are expressed by the following equations.

(Equation 1)
I1 = (V−n × Vf) / R
(Equation 2)
I = m × I1
Therefore, from these formulas 1 and 2, the current I is expressed as the following formula.

(Equation 3)
I = m / R × (V−n × Vf)
Therefore, the voltage-current characteristic indicating the change in current with respect to the battery voltage V is as shown in FIG. 8, and when the battery voltage is equal to or greater than the voltage drop across the n LEDs, the current flows through each line, and the LED 110 It will emit light.
Japanese Patent Laid-Open No. 2002-76439

  It is considered that the circuit shown in FIG. 6 is applied as a circuit for detecting disconnection in an indicator lamp device using a plurality of LEDs as described above, that is, detecting that several of the m LED lines are disconnected. It is done. That is, the shunt resistor R8 shown in FIG. 6 is inserted between the battery 112 shown in FIG. 7 and the LEDs 110 arranged in the m-th row, and the voltage drop at the shunt resistor R8 (that is, the shunt resistor R8 and the m-th row). Disconnection detection can be performed by comparing the voltage between the LEDs 110 arranged in a row and the threshold voltage Vth with the threshold voltage Vth.

  In such a case, the characteristic of the threshold voltage Vth with respect to the battery voltage V is a straight line L1 as shown in FIG. However, the intersection (point Va) between the straight line L1 and the axis where the threshold voltage Vth is 0 corresponds to the breakdown voltage (zener voltage) Vz of the Zener diode ZD1.

  Further, the characteristic indicating the relationship between the voltage value corresponding to the voltage drop at the shunt resistor R8 in the indicator lamp device and the battery voltage V is a straight line L2 as shown in FIG. 9B. However, the intersection B between the straight line L2 and the axis where the voltage drop at the shunt resistor R8 is 0 corresponds to n × Vf.

  Then, when the disconnection occurs, the slope of the straight line L2 decreases according to the number of disconnected lines because the value of m shown in Equation 3 decreases.

  Therefore, if the breakdown voltage Vz of the Zener diode ZD1 in each LED line is set to a value that coincides with n × Vf in Equation 3, the straight line L1 and the threshold voltage Vth as shown in FIG. The point of intersection with the axis of 0 (point Va) coincides with the point of intersection of the straight line L2 and the axis with a voltage value of 0 at the shunt resistor R8. The slope of the straight line L2 is larger when no disconnection occurs than when the straight line L1 is tilted, and smaller when the disconnection occurs. For this reason, it is possible to determine whether the voltage value corresponding to the voltage drop at the shunt resistor R8 with respect to the battery voltage V is located on the right side or the left side of the straight line L1 is disconnected. It becomes.

  However, since the voltage drop amount of the LED 110 also varies from LED 110 to LED 110, the voltage value corresponding to the voltage drop at the shunt resistor R8 with respect to the battery voltage V is shifted by the variation. For example, the characteristics of the battery voltage V and the voltage value corresponding to the voltage drop at the shunt resistor R8 when the disconnection occurs in a normal state where no disconnection occurs and when the disconnection occurs in the half of the m columns (for m / 2 columns) FIG. 10 shows the state of change due to the variation in the voltage drop amount of the LED 110.

  In FIG. 10, the characteristic when the voltage drop amount of the LED 110 is an average value is represented as the center value. Since n × Vf varies depending on the amount of voltage drop of the LED 110, when the amount of voltage drop of the LED 110 is small, the characteristic straight line at that time shifts to the left side of the paper from the center value, and the voltage drop of the LED 110 When the amount is large, the straight line of the characteristic at that time is shifted to the right side of the page from the center value. In the figure, the normal maximum value and the disconnection maximum value are characteristic lines when the voltage drop across the LED 110 during light emission is the smallest, and the normal minimum value and the disconnection minimum value are for the LED 110 during light emission. The characteristic straight line when the voltage drop amount is the largest is shown.

  In such a case, even when the disconnection does not occur, the voltage drop at the shunt resistor R8 with respect to the battery voltage V when the battery voltage V is low when the voltage drop amount of the LED 110 is larger than the average. The voltage value of the minute is positioned on the right side of the page with respect to the straight line L1, and it is erroneously determined that a disconnection has occurred.

  Further, even when the disconnection occurs, when the voltage drop amount of the LED 110 is smaller than the average, when the battery voltage V is low, the relationship of the voltage value corresponding to the voltage drop at the shunt resistor R8 with respect to the battery voltage V is a straight line. It is located on the left side of the sheet with respect to L1, and it is erroneously determined that the disconnection has not occurred despite the occurrence of the disconnection.

  For this reason, when the relationship between the voltage value corresponding to the voltage drop at the shunt resistor R8 with respect to the battery voltage V exists in the area indicated by hatching in FIG. 10, the disconnection occurs even though the disconnection does not occur. There is a problem that it is erroneously determined that it is disconnected, or that it is erroneously determined that it is not disconnected despite being disconnected.

  In view of the above points, the present invention may erroneously determine that a disconnection has not occurred but that the disconnection has occurred, or that the disconnection has occurred but the disconnection has not occurred. It aims at providing the indicator lamp apparatus which can prevent.

  In order to achieve the above object, according to the first aspect of the present invention, there are provided a plurality of LED lines provided with the LEDs (110), the plurality of LED lines are arranged in parallel, and power is supplied from the power source (3). LED indicator lamps (4, 5) for receiving LEDs, a flashing switch (6) for controlling on / off of the power supply line connecting the power source and the LED indicator lamp, and an LED indicator lamp When the switch (2) for lighting is turned on, the flashing control circuit unit (7) for controlling on / off of the flashing switch and the current from the power source to the LED indicator lamp are converted into voltage, and the converted voltage Is compared with the threshold voltage (Vth) to detect that at least one of the LED lines in the LED indicator lamp is disconnected, and the voltage of the power source is determined from the predetermined value (Vz). In this case, a disconnection detection result in the disconnection detection circuit unit is cut, and the lighting control circuit unit is provided with a low voltage cut circuit unit (12) for turning on and off the blinking switch. .

  As described above, the low voltage cut circuit unit prevents the disconnection from being detected when the battery voltage is lower than the predetermined voltage. For this reason, it is possible to prevent erroneous determination that a disconnection has not occurred but that the disconnection has occurred, or that a disconnection has not occurred but the disconnection has not occurred. .

For example, as shown in claim 2, the low voltage cut circuit unit is configured to calculate the voltage between the power supply and the converted voltage when the variation in the forward voltage at the LED becomes the largest when the LED emits light. The power supply voltage (Vz) at the intersection of the straight line (La) indicating the relationship and the straight line (Lb) indicating the relationship between the power supply voltage and the threshold voltage is set as a predetermined value.

  According to a third aspect of the present invention, the disconnection detection circuit unit is provided with a voltage comparator (11) that operates based on the voltage of the power supply and compares the converted voltage with the threshold voltage. When the converted voltage is higher than the threshold voltage, the voltage comparator outputs the power supply voltage as a high level signal. When the voltage comparator outputs the voltage from the voltage comparator When the high level signal is smaller than a predetermined value, the detection result in the disconnection detection circuit unit can be cut, and the lighting control circuit unit can turn on and off the blinking switch.

  Specifically, as shown in claim 4, the low voltage cut circuit section is provided with a Zener diode (13), and the voltage output from the voltage comparator is applied to the Zener diode. When the voltage output from the voltage comparator is higher than the breakdown voltage of the Zener diode, a current flows through the Zener diode, and the disconnection detection result from the disconnection detection circuit unit is transmitted to the blinking control circuit unit. When the voltage output from the voltage comparator is lower than the breakdown voltage of the Zener diode, no current flows through the Zener diode, and the disconnection detection result from the disconnection detection circuit unit is cut. be able to.

  In the invention according to any one of claims 5 to 8, the disconnection detection circuit section includes a current-voltage conversion circuit (9) that converts a current from the power source to the LED indicator lamp into a voltage, and a disconnection that sets a threshold voltage (Vth). A detection threshold circuit unit (10), and a voltage comparator (11) for detecting disconnection by comparing the voltage converted by the current-voltage conversion circuit with the threshold voltage, are used to detect disconnection. If the voltage of the power source is between the first predetermined value and a second predetermined value that is larger than the first predetermined value, the value circuit unit (10) has a threshold value as the power source voltage increases. When the voltage changes with the first slope and the power supply voltage is larger than the second predetermined value, the second slope whose threshold voltage is different from the first slope as the power supply voltage increases. That the threshold voltage is set so that It is a symptom.

  In this way, the threshold voltage can be set so as to avoid a region where erroneous determination is made. For this reason, the same effect as that of the first aspect can be obtained.

For example, as shown in claim 6, the first predetermined value is the amount of voltage drop in the LED indicator light when the LED has the largest variation in forward voltage when the LED emits light. The
Further, as shown in claim 7, the second predetermined value varies with a characteristic line between the voltage of the power supply and the voltage converted by the current-voltage conversion circuit when the LED is caused to emit light, and the second slope. The power supply voltage (C) at the intersection of the threshold voltage characteristic line (Ld) with respect to the power supply voltage to be applied.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
FIG. 1 shows a circuit configuration of a direction indicating device 1 as an indicator lamp device to which an embodiment of the present invention is applied. Based on this figure, the configuration of the direction indicating device 1 will be described.

  For example, when a direction indicator switch 2 disposed on the back of a steering wheel in a vehicle interior is operated by a driver, the direction indicator device 1 is provided with left LED indicator lamps installed on both left and right sides of the vehicle based on power supply from the battery 3. 4 or the right LED indicator lamp 5 is blinked. As shown in FIG. 7 described above, each of the LED indicator lamps 4 and 5 is configured by connecting m LEDs and resistors R in series for m columns in parallel. Although only one LED indicator lamp 4 or 5 is shown in FIG. 1, each LED indicator lamp 4 or 5 actually has three positions, a front position and a rear position. It is provided in three places including, and the indicator lamps at these positions blink at the same time.

  In addition, in this direction indicating device 1, in order to notify the driver when a disconnection is detected in each of the LED indicator lamps 4 and 5, an operation of increasing the blinking cycle of the LED indicator lamps 4 and 5 is performed. To do.

  As shown in FIG. 1, the indicator lamp device 1 includes a blinking relay 6, a blinking control circuit unit 7, a disconnection detection circuit unit 8, and a low voltage cut circuit unit 12.

  The blinking relay 6 corresponds to a blinking switch, and is a known relay that includes a relay contact 6a and a coil 6b that attracts the relay contact 6a by energization. The relay contact 6a controls on / off of the power supply line that connects the left LED indicator lamp 4 or right LED indicator lamp 5 connected by the direction indicating switch 2 and the battery 3 to each other. Therefore, when the coil 6b is energized and the relay contact 6a is attracted, the blinking relay 6 turns on the power supply line at the relay contact 6a, and the left LED indicator 4 or right LED from the battery 3 is turned on. Power is supplied to the indicator lamp 5.

  The blinking control circuit unit 7 detects that the direction indicating switch 2 has been operated based on the potential between the blinking relay 6 and the direction indicating switch 2, and based on that, energizes the coil 6b in the blinking relay 6. In addition, the timing of energization is controlled. The blinking control circuit unit 7 is supplied with a disconnection detection signal from the disconnection detection circuit unit 8, and the energization timing to the coil 6 b is determined based on the disconnection detection signal from the disconnection detection circuit unit 8. It comes to adjust. Specifically, the blinking control circuit unit 7 outputs a pulse voltage of the first lighting cycle when the signal indicating that the disconnection is detected from the disconnection detection circuit unit 8, and the disconnection detection circuit When a signal indicating disconnection is transmitted from the unit 8, the pulse voltage of the second lighting cycle, which is shorter than the first lighting cycle, is output with the second pulse width.

  The disconnection detection circuit unit 8 detects disconnection in each of the LED indicator lamps 4 and 5 constituted by a plurality of LED rows. For example, a disconnection is detected when at least one of the m LED lines constituting each LED indicator lamp 4, 5, for example, half (m / 2) of the m columns is disconnected, and the disconnection detection circuit unit 8 A signal indicating disconnection is output from the blinking control circuit unit 7.

  The disconnection detection circuit unit 8 includes a current detection shunt resistor 9, a disconnection detection threshold circuit unit 10, and a voltage comparator 11.

  The current detection shunt resistor 9 corresponds to a current-voltage conversion circuit unit that converts a current flowing through the power supply line into a voltage. The current detection shunt resistor 9 detects the amount of current in the power supply line connected from the battery 3 to the LED indicator lamps 4 and 5 and is connected in series to the power supply line. In other words, since the voltage across the current detection shunt resistor 9 changes according to the amount of current in the power supply line, the amount of current in the power supply line is detected by the voltage value corresponding to the voltage drop in the current detection shunt resistor 9. It has come to be. Specifically, a potential between the current detection shunt resistor 9 and the relay contact 6a of the blinking relay 6 (point S in the figure) is input to the voltage comparator 11, and the magnitude of this potential is small. Disconnection detection is performed based on the above.

  The disconnection detection threshold circuit unit 10 is a circuit for setting a threshold voltage Vth for disconnection detection. The threshold voltage Vth set by the disconnection detection threshold circuit 10 is input to the voltage comparator 11. It has become so. Depending on the magnitude of the threshold voltage Vth, the number of LED lines that the disconnection detection circuit unit 8 detects as disconnection is determined. The circuit configuration of the disconnection detection threshold circuit unit 10 is the same as that of the circuit shown in FIG.

  The voltage comparator 11 compares the voltage value corresponding to the voltage drop at the current detection shunt resistor 9 (the potential at the point S in the figure) and the threshold voltage Vth set by the disconnection detection threshold circuit unit 10. The size is compared, and is composed of a comparator. When the potential at the point S in the figure is larger than the threshold voltage Vth, the voltage comparator 11 outputs a low level signal indicating that the circuit is not disconnected, and the potential at the point S in the figure is greater. When the voltage is lower than the threshold voltage Vth, a high level signal indicating that the wire has been disconnected is output. Specifically, the comparator constituting the voltage comparator 11 is operated by applying a battery voltage. When a low level signal is output, a GND level output is output, and when a high level signal is output, a battery voltage is output. Is output. For this reason, when the potential at the point S becomes smaller than the threshold voltage Vth, the battery voltage is output as a high level signal from the comparator.

  The low voltage cut circuit unit 12 includes a Zener diode 13, a resistor 14, and an NPN bipolar transistor (hereinafter simply referred to as a transistor) 15. Specifically, the output voltage of the voltage comparator 11 is applied to the Zener diode 13, and the voltage between the Zener diode 13 and the resistor 14 is applied as the base voltage of the transistor 15. In addition, the collector of the transistor 15 is connected to the blinking control circuit unit 7, and the blinking control circuit unit 7 can detect whether a current flows through the collector of the transistor 15 and the collector potential is at a low level. ing.

  Next, the operation of the direction indicating device configured as described above will be described.

  When the direction indicator switch 2 is operated by the driver, the direction indicator switch 2 is turned on to the left LED indicator lamp 4 or the right LED indicator lamp 5. Thereby, the potential between the blinking relay 6 and the direction indicating switch 2 in the power supply line is connected to the GND via the LED indicator lamps 4 and 5, and this is transmitted to the blinking control circuit unit 7. Accordingly, the blinking control circuit unit 7 detects that the direction indicating switch 2 has been operated, and starts energizing the coil 6 b of the blinking relay 6 based on the power supply from the battery 3.

  At this time, in the voltage comparator 11, the voltage value corresponding to the voltage drop in the current detecting shunt resistor 9 (the potential at the point S in the figure) and the threshold voltage set in the disconnection detection threshold circuit unit 10. The level of Vth is compared, and a signal having a level corresponding to the result is output. That is, as shown in FIG. 7, each LED indicator lamp 4, 5 is configured by connecting LED lines in which n LEDs and resistors R are connected in series for m columns in parallel. When is disconnected, the amount of current in the power supply line is reduced by the amount of disconnection. For this reason, in the case of disconnection, the voltage value corresponding to the voltage drop in the current detecting shunt resistor 9, that is, the potential at the point S in the figure becomes smaller in accordance with the number of LED lines disconnected, and the threshold voltage It becomes smaller than Vth.

  Since the potential at the point S in the figure is larger than the threshold voltage Vth in the state before the number of disconnected LED lines reaches the number at which the disconnection detection circuit unit 8 can detect disconnection, the voltage comparator 11 outputs a low level signal which means that the circuit is not disconnected. In this case, since a voltage lower than the breakdown voltage is applied to the Zener diode 13, the Zener diode 13 does not pass current, and the transistor 15 does not turn on. For this reason, the blinking control circuit unit 7 detects that the potential of the collector of the transistor 15 is at a high level, that is, not at a low level, and assumes that there is no disconnection, and the pulse that becomes the first lighting cycle. A voltage is applied to the coil 6b. Thereby, the LED indicator lamps 4 and 5 on the side where the direction indicating switch 2 is turned on by the driver blinks at the first lighting cycle.

  On the other hand, when the number of broken LED lines reaches the number that can be detected as broken by the break detection circuit unit 8, the potential at the point S in the figure becomes smaller than the threshold voltage Vth, and the voltage comparator 11 breaks. A high level signal indicating that the

  At this time, since the high level signal output from the voltage comparator 11 is the battery voltage, whether or not the transistor 15 is turned on depends on whether or not the battery voltage is equal to or higher than the breakdown voltage of the Zener diode 13.

  That is, when the battery voltage is equal to or higher than the breakdown voltage of the Zener diode 13, a current flows through the Zener diode 13, and thus a current also flows through the resistor 14. For this reason, the transistor 15 is turned on, and a current flows between the collector and the emitter of the transistor 15. As a result, the collector potential of the transistor 15 becomes almost the GND potential and becomes a low level. Accordingly, in this case, the blinking control circuit unit 7 applies a pulse voltage that becomes the second lighting cycle to the coil 6b, assuming that it is disconnected. Thereby, the LED indicator lamps 4 and 5 on the side where the direction indicating switch 2 is turned on by the driver blinks in the second lighting cycle shorter than the first lighting cycle.

  On the other hand, when the battery voltage does not reach the breakdown voltage of the Zener diode 13, the Zener diode 13 does not pass current, and the transistor 15 is not turned on. For this reason, the blinking control circuit unit 7 detects that the potential of the collector of the transistor 15 is at a high level, that is, not at a low level, and assumes that there is no disconnection, and the pulse that becomes the first lighting cycle. A voltage is applied to the coil 6b. Thereby, the LED indicator lamps 4 and 5 on the side where the direction indicating switch 2 is turned on by the driver blinks at the first lighting cycle.

  As described above, the breakdown voltage of the Zener diode 13 is set as a predetermined voltage, and the magnitude of the battery voltage at which disconnection detection is performed is determined according to the breakdown voltage. For this reason, in this embodiment, the breakdown voltage of the Zener diode 13 is determined as follows.

  FIG. 2 shows the relationship between the breakdown voltage of the Zener diode 13, the characteristics of the battery voltage and the threshold voltage Vth, and the characteristics of the battery voltage and the voltage value corresponding to the voltage drop at the current detecting shunt resistor 9. As shown in this figure, the straight line indicating the relationship between the battery voltage and the threshold voltage Vth shifts according to the voltage drop amount of the LED.

  Therefore, a straight line indicating the relationship between the battery voltage at the normal minimum value and the voltage value corresponding to the voltage drop at the current detecting shunt resistor 9 is La, and the relationship between the battery voltage and the threshold voltage Vth for detecting disconnection is shown. If the straight line is Lb, an erroneous determination occurs when the battery voltage becomes smaller than the voltage value Vz at these intersections. Therefore, in this embodiment, the breakdown voltage of the Zener diode 13 is set to be equal to or higher than the voltage value Vz. However, in the direction indicating device 1, since the minimum value of the battery voltage, that is, the minimum value of the operating voltage range that is supposed to be able to realize the disconnection detection function is standardized, it becomes smaller than the minimum value of the operating voltage range. The breakdown voltage of the Zener diode 13 is set to

  Thus, in the present embodiment, when the battery voltage is smaller than the breakdown voltage of the Zener diode 13, disconnection detection is not performed. The breakdown voltage of the Zener diode 13 is set to be equal to or higher than the voltage value Vz. For this reason, it is possible to prevent erroneous determination that a disconnection has not occurred but that the disconnection has occurred, or that a disconnection has not occurred but the disconnection has not occurred. .

(Second Embodiment)
A second embodiment of the present invention will be described. FIG. 3 shows a circuit configuration of the direction indicating device in the present embodiment. As shown in this figure, the direction indicator in the present embodiment has a circuit configuration substantially similar to that of the first embodiment, and has no low voltage cut circuit unit compared to the first embodiment. The difference is that the configuration of the disconnection detection threshold circuit is changed. Hereinafter, the direction indicating device according to the present embodiment will be described, but only differences from the first embodiment will be described.

  The disconnection detection threshold circuit 10 provided in the direction indicating device shown in FIG. 3 has a circuit configuration as shown in FIG. Specifically, the disconnection detection threshold circuit unit 10 includes a first resistor R1, a first Zener diode ZD1, a second resistor R2, and a second Zener diode ZD2 between the battery 3 and the GND terminal. Are connected in series, and the third and fourth resistors R3 and R4 connected in series are connected in parallel to the first resistor R1 and the first Zener diode ZD1.

  A characteristic diagram showing the relationship between the battery voltage and the threshold voltage Vth in such a configuration and a figure comparing the characteristic with the erroneously determined region shown in FIG. 10 are shown in FIGS. The relationship between the battery voltage and the threshold voltage Vth will be described with reference to these drawings.

  First, when the battery voltage is lower than the first predetermined value, that is, the breakdown voltage of the second Zener diode ZD2, no current flows through the second Zener diode ZD2.

  When the battery voltage is equal to or higher than the breakdown voltage of the second Zener diode ZD2 and lower than the total value of the breakdown voltages of the first Zener diode ZD1 and the second Zener diode ZD2, the third and fourth A current flows through the resistors R3 and R4, and further through the path X through the second resistor R2 and the second Zener diode ZD2.

  Therefore, the threshold voltage Vth is set to a value obtained by dividing the value obtained by subtracting the breakdown voltage of the second Zener diode ZD2 from the battery voltage by the second to fourth resistors R2 to R4. Then, since the current flowing through the third resistor R3 changes according to the magnitude of the battery voltage, as shown in FIG. 5A, when the battery voltage becomes larger, the threshold is the first slope. The value voltage Vth increases.

  At this time, if the straight line of the battery voltage-threshold voltage Vth having the first slope is Lc, a point B that is the intersection of the straight line Lc and the axis where the threshold voltage Vth is 0 is the second Zener diode. Since this is the breakdown voltage of ZD2, the breakdown voltage of the second Zener diode ZD2 is set so as to be a value to be set as the point B. Specifically, in the present embodiment, the point B is the characteristic line of the normal minimum value shown in FIG. 5B and the axis where the voltage value corresponding to the voltage drop at the current detecting shunt resistor 9 becomes zero. Is the battery voltage at the intersection of the characteristic line of the minimum value at normal time and the straight line Ld described later, which is larger than the point A corresponding to the voltage drop amount at each LED indicator lamp 4 and 5 at the time of light emission. It is set to be smaller than the point C.

  Next, when the battery voltage is higher than the second predetermined value, that is, the total value of the breakdown voltages of the first Zener diode ZD1 and the second Zener diode ZD2, in addition to the path X, the first resistor A current flows through R1 and the first Zener diode ZZD1, and further through a path Y through the second resistor R2 and the second Zener diode ZD2. For this reason, the amount of current flowing through the second resistor R2 increases, and the voltage value corresponding to the voltage drop at the second resistor R2 increases, so that the voltage between the fourth resistor R4 and the second resistor R2 is increased. The potential at the point increases, and the voltage across the third and fourth resistors R3 and R4 decreases.

  Therefore, the current flowing through the third resistor R3 is smaller when the current flows through the path X and the path Y than when the current flows through the path X only. For this reason, the threshold voltage Vth determined by the voltage across the third resistor R3 increases with a second slope having a slope smaller than the first slope when the battery voltage increases. That is, the characteristic indicating the relationship between the battery voltage and the threshold voltage Vth changes from the first slope to the second slope at a point where the battery voltage becomes the second predetermined value.

  At this time, if the straight line of the battery voltage-threshold voltage Vth having the second slope is Ld, the value of the battery voltage at the intersection of the straight line Lc and the straight line Ld is the point D of the second Zener diode ZD2. This is the breakdown voltage. Therefore, the breakdown voltage of the first Zener diode ZD1 is set so as to be a value to be set as the point D. Specifically, in this embodiment, the point D is from the point C indicating the battery voltage at the intersection of the characteristic line of the normal minimum value shown in FIG. 5B and the straight line Ld indicating the disconnection detection threshold. And is set to be smaller than the minimum value of the operating voltage range (minimum value of the battery voltage at which the disconnection detection function must be realized in the direction indicating device 1).

  As described above, according to the present embodiment, the threshold voltage Vth can be set so as to avoid the erroneous determination region indicated by hatching in FIG. The point B is set to a value smaller than the point C. For this reason, the same effect as in the first embodiment can be obtained, and further, when the battery voltage has a magnitude located between the point B and the point D, the amount of voltage drop at the disconnection detection shunt resistor 9 is obtained. Even when the relationship between the voltage value and the battery voltage is located on the right side of the drawing with respect to the straight line Lc, it is possible to detect disconnection.

(Other embodiments)
In the above embodiment, the breakdown voltage of the Zener diode 13 is set to the voltage value Vz. At this time, the voltage value Vz includes the straight line La indicating the relationship between the battery voltage at the normal minimum value and the voltage value corresponding to the voltage drop at the current detection shunt resistor 9, and the threshold voltage for battery voltage and disconnection detection. The battery voltage is at the intersection of the straight line Lb indicating the relationship of Vth.

  However, the voltage value Vz may be the battery voltage at the intersection of the straight line Lb and the straight line indicating the relationship between the battery voltage and the threshold voltage Vth at the maximum value at the time of disconnection. Further, such a battery voltage, a straight line La indicating the relationship between the battery voltage at the normal minimum value and the voltage value corresponding to the voltage drop at the current detecting shunt resistor 9, and the threshold value for detecting the battery voltage and disconnection. Of the battery voltages at the intersection of the straight lines Lb indicating the relationship of the voltage Vth, the larger voltage may be used as the voltage value Vz.

It is a figure which shows the circuit structure of the direction indicator in 1st Embodiment of this invention. It is the figure which showed the circuit structure of the disconnection detection threshold value circuit part in FIG. It is the figure which showed the relationship between a battery voltage and threshold voltage Vth. It is the figure which showed the circuit structure of the disconnection detection threshold value circuit part with which the direction indicator was equipped. (A) is a characteristic diagram showing the relationship between the battery voltage and the threshold voltage Vth, and (b) is a diagram compared with a region where the characteristic of (a) is erroneously determined. It is a figure which shows the circuit structure of the indicator lamp device with a disconnection detection function conventionally used as a direction indicator for vehicles. The circuit diagram of the indicator lamp apparatus when several LED is arranged is shown. FIG. 6 is a voltage-current characteristic diagram showing a change in current with respect to battery voltage V. (A) is a figure which shows the characteristic of the threshold voltage Vth with respect to the battery voltage V, (b) is a figure which shows the characteristic of the voltage value for the voltage drop by shunt resistance, and the battery voltage V, (c) is It is the figure which combined and showed the straight lines L1 and L2 shown to (a) and (b). It is the figure showing a mode that the characteristic of the battery voltage and the voltage value for the voltage drop by shunt resistance at the time of the normal time when disconnection did not occur and when the disconnection occurred changes due to the variation in the voltage drop amount of the LED.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Direction indication apparatus, 2 ... Direction indication switch, 3 ... Battery, 4, 5 ... LED indicator light, 6 ... Flashing relay, 7 ... Flashing control circuit part, 8 ... Disconnection detection circuit part, 9 ... Disconnection detection shunt Resistor, 10: Disconnection detection threshold circuit unit, 11: Voltage comparator, 12 ... Low voltage cut circuit unit, 13 ... Zener diode, 14 ... Resistor, 15 ... Transistor.

Claims (8)

An LED indicator (4, 5) having a plurality of LED lines provided with LEDs (110), the plurality of LED lines being arranged in parallel, and receiving the power supply from the power source (3) to emit the LEDs. When,
A blinking switch (6) for controlling on / off of a power supply line connecting between the power source and the LED indicator;
When a switch (2) for turning on the LED indicator is turned on, a blinking control circuit unit (7) for controlling on / off of the blinking switch;
The current from the power source to the LED indicator lamp is converted into a voltage, and the converted voltage is compared with a threshold voltage (Vth), whereby at least one of the LED lines in the LED indicator lamp is disconnected. Disconnection detection circuit section (8) for detecting
When the voltage of the power source is smaller than a predetermined value (Vz), a low voltage cut circuit that cuts off the disconnection detection result in the disconnection detection circuit unit and turns on and off the blinking switch in the lighting control circuit unit An indicator lamp device comprising a portion (12). The low voltage cut circuit unit is a straight line (La) indicating a relationship between the voltage of the power source and the converted voltage when the forward voltage variation in the LED becomes the largest when the LED emits light. The voltage (Vz) of the power supply at the intersection of the voltage of the power supply and a straight line (Lb) indicating the relationship between the threshold voltage is set as the predetermined value. Indicator light device. The disconnection detection circuit unit includes a voltage comparator (11) that operates based on the voltage of the power source and compares the converted voltage with the threshold voltage.
The voltage comparator is configured to output the voltage of the power source as a high level signal when the converted voltage is smaller than the threshold voltage.
The low voltage cut circuit unit cuts the detection result in the disconnection detection circuit unit when the high level signal output from the voltage comparator is smaller than the predetermined value, and the lighting control circuit unit The indicator lamp device according to claim 1 or 2, wherein the blinking switch is turned on and off. The low voltage cut circuit unit is provided with a Zener diode (13), and the voltage output from the voltage comparator is applied to the Zener diode.
When the voltage output from the voltage comparator is higher than the breakdown voltage of the Zener diode, a current flows through the Zener diode, and a disconnection detection result from the disconnection detection circuit unit is transmitted to the blinking control circuit unit. When the voltage output from the voltage comparator is lower than the breakdown voltage of the Zener diode, no current flows through the Zener diode, and the disconnection detection result from the disconnection detection circuit unit is cut. The indicator lamp device according to claim 3, wherein the indicator lamp device is configured as described above. An LED indicator (4, 5) having a plurality of LED lines provided with LEDs (110), the plurality of LED lines being arranged in parallel, and receiving the power supply from the power source (3) to emit the LEDs. When,
A blinking switch (6) for controlling on / off of a power supply line connecting between the power source and the LED indicator;
When a switch (2) for turning on the LED indicator is turned on, a blinking control circuit unit (7) for controlling on / off of the blinking switch;
A display lamp device comprising a disconnection detection circuit section (8) for detecting that at least one of the LED lines in the LED indicator lamp is disconnected,
The disconnection detection circuit unit is
A current-voltage conversion circuit (9) for converting a current from the power source to the LED indicator lamp into a voltage;
Disconnection detection threshold circuit (10) for setting a threshold voltage (Vth);
A voltage comparator (11) that detects the disconnection by comparing the voltage converted by the current-voltage conversion circuit and the threshold voltage;
If the voltage of the power source is between a first predetermined value and a second predetermined value larger than the first predetermined value, the disconnection detection threshold circuit unit (10) increases the voltage of the power source. When the threshold voltage changes with a first slope and the power supply voltage is larger than the second predetermined value, the threshold voltage is increased as the power supply voltage increases. The indicator lamp device is characterized in that the threshold voltage is set such that the threshold voltage changes with a second inclination different from the first inclination. 6. The first predetermined value is a voltage drop amount in the LED indicator light when a forward voltage variation in the LED becomes maximum when the LED emits light. The indicator light apparatus as described in. The second predetermined value corresponds to a characteristic straight line between the voltage of the power supply and the voltage converted by the current-voltage conversion circuit when the LED emits light, and the voltage of the power supply that changes with the second slope. The indicator lamp device according to claim 5 or 6, wherein the indicator lamp device is a voltage (C) of the power source at an intersection with the characteristic line (Ld) of the threshold voltage. The indicator lamp device according to claim 5, wherein the second inclination is smaller than the first inclination.

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