JPH0646103Y2 - Comparison circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a comparator circuit having a reference voltage adjusting function,
In particular, the present invention relates to a comparison circuit that maintains a constant relationship between both the comparison voltage and the reference voltage even when both of them fluctuate.

[Prior Art] Conventionally, for example, an operational amplifier, that is, an operational amplifier is frequently used as a comparator that compares a comparison voltage with a reference voltage and outputs the comparison voltage according to the comparison result. Since the input resistance is very high and the bias current hardly flows, this can be easily set only by the resistance division ratio when setting the reference voltage. Therefore, the two input terminals for inputting the normal reference voltage and the comparison voltage are both connected to the voltage dividing resistor to form a comparison circuit.

[Problems to be Solved by the Invention] However, for example, as shown in FIG.
When the reference voltage input to the comparator consisting of the comparator is not set by a resistor and the reference voltage and the power supply voltage for supplying the reference voltage change, the relationship between the reference voltage and the comparison voltage may differ from that before the change. is there. That is, in FIG. 4, the voltage of the power source + V _B is divided by the voltage dividing resistors 2 and 3, and the reference voltage is set to the non-inverting input terminal of the operational amplifier 1. On the other hand, the comparison voltage input to the inverting input terminal of the operational amplifier 1 is the switching transistor 5, the resistor 6,
And, for example, a load 7 consisting of lamps connected in parallel. Therefore, for example, when the resistance value of the load 7 decreases and a larger current than usual flows in the switching transistor 5,
The collector-emitter voltage rises, the comparison voltage rises,
When this exceeds the reference voltage, the output of the operational amplifier 1 is inverted. In the above configuration, when the power supply voltage fluctuates, there is no problem if both the reference voltage and the comparison voltage are determined by the resistance value. When the voltage is the comparison voltage, the correspondence with the reference voltage determined by the resistance division ratio differs before and after the fluctuation of the power supply voltage. This will be described with reference to FIG. 2. The reference voltage S ₀ increases with a relatively gentle slope with respect to the increase of the power supply voltage as shown by the alternate long and short dash line.
C ₁ and C ₂ (broken line) increase steeply. Where the comparison voltage
C ₁ is the value before the resistance value of the load 7 fluctuates and is the comparison voltage.
C ₂ is a value when the resistance value of the load 7 decreases and the collector current of the switching transistor 5 increases. Reference voltage
In the relationship between the comparison voltage C _1, C ₂ and S _0, the area can not be determined by the reference voltage S ₀ to the comparison voltage C _1, C ₂ relative to the reference voltage S ₀ regardless of the variation in the power supply voltage has occurred . In FIG. 2, the relationship between the reference voltage and the comparison voltage is compared and explained, so that the two are enlarged.

Therefore, an object of the present invention is to adjust the reference voltage so that the comparison between the reference voltage and the reference voltage may be changed even if the comparison voltage and the reference voltage change due to the change of the power supply voltage.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the comparison circuit of the present invention has a reference voltage which is set by resistance division of a changing power supply voltage, and a reference voltage which changes according to the change of the power supply voltage. In a comparison circuit equipped with a comparator that compares a comparison voltage that fluctuates according to the fluctuation of the power supply voltage in a relationship different from fluctuations and outputs according to the comparison result, in parallel with the voltage dividing resistor that sets the reference voltage. Is connected to at least a Zener diode.

In particular, the comparator is an operational amplifier in which the voltage dividing resistor is connected to one input terminal and the comparison voltage is input to the other input terminal, and a series circuit of a Zener diode and a resistor is connected in parallel with the voltage dividing resistor. It is recommended that the comparison circuit be connected to.

A disconnection detection circuit provided in a vehicle lamp blinking device having an oscillation circuit having an operational amplifier, and having a disconnection detection circuit having a second operational amplifier, including a comparator composed of the second operational amplifier, It is preferable to configure a comparison circuit in which a series circuit of a Zener diode and a resistor is connected in parallel with the voltage dividing resistor connected to one input terminal.

[Operation] In the comparator circuit configured as described above, the fluctuating power supply voltage is resistance-divided to set the reference voltage, and the reference voltage is changed according to the change of the power supply voltage in a relationship different from the change of the reference voltage. The comparison voltage to be compared is compared with the reference voltage in the comparator. Therefore, when the power supply voltage is less than the predetermined value, the reference voltage is set by resistance division,
This is compared with the comparison voltage in the comparator, and is output according to the comparison result. On the other hand, when the power supply voltage increases and exceeds a predetermined value and a voltage exceeding the Zener voltage is applied to the Zener diode, the reference voltage rises according to the impedance of the Zener diode. Thus, the comparison with the comparison voltage, which increases as the power supply voltage increases, is performed in an appropriate correspondence relationship. As is clear from FIG. 2, this relationship turns into a steep slope at the point where the reference voltage S (solid line) exceeds the Zener voltage (point Z in FIG. 2), and the power source voltage rises. The comparison voltages C ₁ and C ₂ (broken line) rise in a substantially parallel manner. When a resistor is connected in series with the Zener diode as described in claim 2, the voltage drop by the resistor further secures the followability to the fluctuation of the comparison voltage.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows an embodiment of the comparison circuit of the present invention. The comparator according to claim 1 is composed of an operational amplifier 1, and the non-inverting input terminal divides the voltage of the power source + V _{B by} a voltage dividing resistor 2 and 3.
Is connected to the connection point of. The inverting input terminal side of the operational amplifier 1 is connected to the collector side of a PNP type switching transistor 5 whose emitter is connected to the power source + V _B , and this collector side is grounded via a resistor 6 and a load 7.
The load 7 is configured so that, for example, in a parallel circuit of a plurality of lamps, an impedance drop occurs under a predetermined condition so that the resistance value is reduced due to a lamp disconnection, and this is detected by the operational amplifier 1. The base of the switching transistor 5 is a control circuit (not shown) via an input terminal.
The switch transistor 5 is configured to be turned on / off according to an output signal from the control circuit or the like. Further, the output terminal of the operational amplifier 1 is connected to a display device (not shown) or the like, and is configured to perform display according to the output signal, for example. A reference voltage adjusting circuit 4 including a series circuit of a Zener diode 46 and a resistor 47 is connected in parallel with the voltage dividing resistor 2.

The operation of the embodiment as described above will be described below.
Is normal, when the switching transistor 5 is conducting,
The comparison voltage on the inverting input terminal side becomes less than or equal to the reference voltage set by the voltage dividing resistors 2 and 3 on the non-inverting input terminal side.
Becomes an H (high) level output. On the other hand, when the impedance of the load 7 decreases, the collector current increases when the switching transistor 5 is conducting, so that the collector-emitter voltage increases, the inverting input terminal side exceeds the reference voltage, and the output of the operational amplifier 1 becomes L ( Low) level and the output state of the output pin is inverted.

In the above, when the voltage of the power supply + V _B fluctuates and exceeds a predetermined value (the Zener voltage of the Zener diode 46), a current flows through the Zener diode 46 and the resistor 47, and the voltage drop due to these causes a non-inverting input terminal of the operational amplifier 1. Side reference voltage rises. This rise follows the rise of the collector-emitter voltage of the switching transistor 5 accompanying the above-mentioned fluctuation of the power supply voltage, and the correspondence with the comparison voltage on the inverting input terminal side is maintained.
The relationship between them is the same as the relationship described with reference to FIG.

Next, an embodiment in which one embodiment of the present invention is applied to a vehicle lamp blinking device will be described. In FIG. 3, a vehicle lamp circuit 15 connected to a power source + V _B of a vehicle battery via an ignition switch 11 or the like is grounded to a vehicle body (not shown).

The vehicle lamp circuit 15 has a common right lamp circuit 15R in which a plurality of lamps (four lamps in this embodiment) are connected in parallel and is provided on the right side of the vehicle, and a left side lamp circuit 15L similarly provided on the left side of the vehicle. It is composed of a grounded parallel circuit. The right lamp circuit 15R and the left lamp circuit 15L are connected to the right fixed contact 13R and the left fixed contact 13L of the turn signal switch 13, respectively, and the hazard switch 1
4 is connected to the right fixed contact 14R and the left fixed contact 14L. The right pilot lamp 16R and the left pilot lamp 16L, which are respectively connected in parallel to the right lamp circuit 15R and the left lamp circuit 15L, are arranged around the driver's seat of the vehicle (not shown), and are composed of light emitting diodes. May be

The operation switch 12 is composed of the turn signal switch 13 and the hazard switch 14, and the turn signal switch 13 is operated from the neutral position by the driver to operate the right fixed contact 13R.
Alternatively, a movable contact 13M that contacts the left fixed contact 13L is provided, and the movable contact 13M is provided with an automatic return mechanism (not shown) that works in conjunction with a steering wheel (not shown) of the vehicle. The hazard switch 14 has the right fixed contact 14
Right movable contact 14MT that contacts R and left fixed contact 14L respectively
It is provided with an R and a left movable contact 14ML, which are configured to operate simultaneously, and have an open / close switch structure such as a seesaw switch. And the right fixed contact 13
The R, left fixed contact 13L, right movable contact 14MR, and left movable contact 14ML are connected to the drive circuit 20.

The drive circuit 20 is composed of a two-stage transistor including a transistor 21 and a transistor 22, and the transistor 22 constitutes a switching transistor according to claim 3. The transistor 22 is a PNP type transistor, the emitter of which is connected to the power supply + V _B via the ignition switch 11,
The collector is grounded via the resistor 25, the voltage dividing resistor 42, the voltage dividing resistor 43 and the diode 18. Where diode 18
Is provided for the purpose of preventing reverse connection and is not always essential. The resistor 25 is not necessarily provided and may be omitted. The base of transistor 22 is a resistor
It is connected to the collector of the NPN-type transistor 21 via 24, and the base and the emitter are connected by the resistor 27. The emitter of the transistor 21 is grounded via the diode 26, and the base is connected to the oscillation circuit 30 via the resistor 23.

The oscillator circuit 30 is a square wave oscillator circuit using an operational amplifier, that is, an operational amplifier, and a constant voltage Vcc is applied by a Zener diode 16 and a resistor 17.

A capacitor 32 with one end grounded is connected to the inverting input terminal of the operational amplifier 31 to form an integrating circuit with a resistor 36 that feeds back from the output terminal to the inverting input terminal, and a zener diode 16 and a resistor 17 via the resistor 33. Is connected to a constant voltage point. The voltage dividing resistor 34 and the voltage dividing resistor 35 connected in series are connected in parallel to the Zener diode 16,
The connection point of these voltage dividing resistors 34 and 35 is the operational amplifier 31.
Connected to the non-inverting input terminal of the constant voltage Vcc
And is divided by the voltage dividing resistor 35 and input to the non-inverting input terminal. Further, feedback is applied from the output terminal to the non-inverting input terminal by the resistor 37 to form a hysteresis circuit.
The output terminal of the operational amplifier 31 is connected to the base of the transistor 21 via the resistor 23, and the non-inverting input terminal is connected to the lamp burnout detection circuit 40.

Therefore, the voltage dividing resistor 34 is connected to the non-inverting input terminal of the operational amplifier 31.
And the voltage divided by the voltage dividing resistor 35 is applied, and when the output terminal is at the H (high) level, the voltage is applied via the resistor 37, and the first reference voltage (for example,
5V) is formed. At this time, a resistor 33 is connected to the inverting input terminal.
And the voltage of the capacitor 32 charged via the resistor 36 is applied. When the charging voltage of the capacitor 32 exceeds the first reference voltage of the non-inverting input terminal after a lapse of a predetermined time, the output state of the operational amplifier 31 is inverted, the output terminal becomes an L (low) level output, and the non-inverting input terminal The voltage drops and becomes the second reference voltage (for example, 3V). This allows the capacitor
When 32 starts discharging through the resistor 36 and reaches the second reference voltage of the non-inverting input terminal after a predetermined time, the output state is inverted again and the output terminal becomes H level. This H level signal is fed back to the non-inverting input terminal by the resistor 37 and returns to the previous state (first reference voltage). By repeating the above operation, the oscillation output of the pulse signal of the predetermined frequency is obtained from the output terminal of the operational amplifier 31.

The lamp disconnection detection circuit 40 has an operational amplifier 41 which is the second operational amplifier described in claim 3, and the transistor 22 has a resistor 25.
The connection point of both the series circuit of the voltage dividing resistor 42 and the voltage dividing resistor 43 connected via is connected to the inverting input terminal of the operational amplifier 41, and the connection point of the resistor 25 and the voltage dividing resistor 42 is the operation switch 12
And the voltage dividing resistor 43 is grounded. The voltage dividing resistor 42 is a variable resistor so that it can be finely adjusted. The non-inverting input terminal of the operational amplifier 41 is connected to the connection point of the voltage dividing resistor 44 and the voltage dividing resistor 45 connected in series between the constant voltage point and the diode 18, and the constant voltage Vcc is divided by the voltage dividing resistor 44 and the voltage dividing resistor 45. The divided disconnection detection reference voltage is applied. The reference voltage adjusting circuit 4 including the Zener diode 46 and the resistor 47 is
It is connected in parallel to the voltage dividing resistor 44. This is the first
The function is similar to that of the embodiment shown in the figure, and the disconnection detection reference voltage is adjusted according to the voltage fluctuation of the power supply + V _B.
Then, the output terminal of the operational amplifier 41, through the resistor 48 and the diode 49 whose cathode side is connected to this resistor 48,
It is connected to the non-inverting input terminal of the operational amplifier 31.

Therefore, since the disconnection detection reference voltage is always higher than the voltage at the connection point of the voltage dividing resistors 42 and 43, the operational amplifier is
The output of the output terminal of 41 is at the H level, and therefore does not affect the operation of the operational amplifier 31. However, as will be described later, the potential at the connection point between the voltage dividing resistor 42 and the voltage dividing resistor 43 increases due to the disconnection of any of the plurality of lamps of the vehicle lamp circuit 15, and when the disconnection detection reference voltage is exceeded, the operational amplifier 41 The output terminal becomes L level, the reference voltage of the non-inverting input terminal of the operational amplifier 31 drops, and the third reference voltage (for example, 4V)
Becomes

The starting circuit 50 detects the operating state of the operating switch 12, and when all of the switches are in the open state, the driving circuit 20, the oscillating circuit 30, and the lamp burnout detecting circuit 40 are stopped to reduce power consumption. That is, the NPN transistor 5
The emitter of 1 is connected to the left fixed contact 13L and the left fixed contact 14L, and the base is connected to the connection point of the resistor 17 and the Zener diode 16, that is, the constant voltage point via the resistor 55 and the resistor 19. Similarly, the emitter of the NPN transistor 52 is connected to the right fixed contact 13R and the right fixed contact 14R, and the base is connected to the constant voltage point via the resistor 57 and the resistor 19. The connection point between the resistor 19 and the resistors 55 and 57 is connected to the movable contact side of the operation switch 12. Therefore,
A bias voltage is always applied to the transistors 51 and 52 regardless of the operation of the operation switch 12.

The collectors of these transistors 51 and 52 are connected to the constant voltage point via resistors 56 and 58, respectively, and the NOR circuit 5
Connected to 4 input terminals. The output terminal of the NOR circuit 54 is connected to the base of the NPN transistor 53 via the resistor 59, its emitter is grounded, and its collector is a diode.
Connected to 49 cathodes.

When the ignition switch 11 is turned on, the transistors 51 and 52 are turned on, the input terminals of the NOR circuit 54 are both at the L level, and the output is at the H level. Therefore, the transistor 53 is turned on, the cathode side of the diode 49 is grounded through the transistor 53, and the inverting input terminal of the operational amplifier 31 is maintained at a predetermined potential by at least the resistor 33, so that the operational amplifier 31 does not operate, and thus the drive circuit. 20, the lamp burnout detection circuit 40 also does not work. And operation switch
When any one of the switches 12 is closed, the emitter-base of either the transistor 51 or the transistor 52 is short-circuited, one of the transistors 51 and 52 is cut off and the transistor 53 is cut off, and the oscillation circuit 30, The operation of the drive circuit 20 and the lamp burnout detection circuit 40 is configured to start.

The operation of the vehicle lamp blinking device having the above configuration will be described.

(B) When the ignition switch 11 is operated When the ignition switch 11 is turned on, resistance 17,19,55
And 57, the base current is supplied to each of the transistors 51 and 52 to make them conductive, so that the base current is supplied to the transistor 53 to make the transistor 53 conductive. Therefore, as described above, none of the drive circuit 20, the oscillator circuit 30, and the lamp burnout detection circuit 40 operates.

Therefore, for example, when the starting circuit 50 is not provided, the oscillation circuit 30 operates at the same time when the ignition switch 11 is turned on, and thus the driving circuit 20 operates and the power supply current is the transistor 22, the resistor 24, the transistor 21, and the diode 26. In contrast to the consumption through the diode 18, in the present embodiment, the current consumption of only the operating currents of the transistors 51, 52 and 53 for signals is suppressed to a small current consumption.

(B) When the turn signal switch 13 is operated When the vehicle (not shown) is operated, for example, when the turn signal switch 13 for turning right is operated in the right turn direction, that is, the turn signal switch 13 is movable with the ignition switch 11 on. When the contact 13M is connected to the right fixed contact 13R, the emitter-base of the transistor 52 is short-circuited via the right fixed contact 13R, the movable contact 13M and the resistor 57, and the transistor 52 is cut off.
Is cut off. Therefore, the operational amplifier 31 of the oscillator circuit 30
The first reference voltage is applied to the non-inverting input terminal of the oscillation circuit 30 and the oscillation circuit 30 starts the oscillation operation. Thus, a pulse signal is output from the oscillation circuit 30 in a predetermined cycle, and the transistor 21 is turned on / off in response to the pulse signal, so that the transistor 22 is turned on / off repeatedly.

In accordance with the on / off operation repeated for a predetermined period of conduction and interruption in the transistor 22, the power supply current is supplied to the right lamp circuit 15R through the transistor 22, the resistor 25, the movable contact 13M and the right fixed contact 13R, and the right lamp Circuit 1
The four lamps of 5R and the right pilot lamp 16R blink in a predetermined cycle.

When turning left, the movable contact 13 of the turn signal switch 13
M contacts the left fixed contact 13L, and the lamp of the left lamp circuit 15L and the left pilot lamp 16L blink in the same manner as described above.

(C) When the lamp is burnt out When the turn signal switch 13 is operated, in either the right lamp circuit 15R or the left lamp circuit 15L, at least one of the four lamps in any of the four lamp circuits 15L When the two lamps are burnt out, the collector potential of the transistor 22 rises and the resistor 25 and the voltage dividing resistor
The potential at the connection point of 42 rises. As a result, when the transistor 22 is conducting, the inverting input terminal side of the operational amplifier 41 becomes higher than the disconnection detection reference voltage on the non-inverting input terminal side, and the output from the output terminal becomes L level. Therefore, the non-inverting input terminal of the operational amplifier 31 in the oscillation circuit 30 drops to the third reference voltage (for example, 4V), and the third reference voltage and the second reference voltage on the inverting input terminal side (for example, 3V). The capacitor 32 is repeatedly charged and discharged between and, and a pulse signal is output from the output terminal of the operational amplifier 31. That is, the pulse signal whose period is shortened as compared with the output pulse signal at the normal time by charging and discharging the capacitor 32 between the first reference voltage (for example, 5V) and the second reference voltage (for example, 3V) Is output. Therefore, the blinking cycle of the lamp of the right side lamp circuit 15R or the left side lamp circuit 15L in which at least one lamp is broken becomes shorter than that in the normal time (that is, the blinking speed becomes faster).

By the way, the power supply voltage of the vehicle fluctuates, for example 8V to 16V
If it fluctuates in such a large range, the problem described with reference to FIG. 2 will occur. However, in this embodiment, since the reference voltage adjusting circuit 4 is present, when the power source + V _B exceeds the predetermined voltage (the Zener voltage of the Zener diode 46), the voltage generated in the Zener diode 46 and the resistor 47 is generated in the transistor 22. Follows the rise in collector-emitter voltage as the collector current rises. Thus, the input on the inverting input terminal side of the operational amplifier 41 and the disconnection detection reference voltage are always compared with each other in an appropriate correspondence relationship regardless of the fluctuation of the power supply voltage.

(D) When the hazard switch 14 is operated When the hazard switch 14 is operated, the right movable contact 14MR and the left movable contact 14ML are simultaneously connected to the right fixed contact 14R and the left fixed contact 14L, respectively, and when the transistor 22 is conducting, the right lamp circuit 15R. And, all the lamps of the left side lamp circuit 15L are turned on. Then, the drive circuit 20 and the oscillator circuit 30 operate in the same manner as when the turn signal switch 13 is operated. Therefore, the right side ramp circuit 15R and the left side ramp circuit 15L blink in the same cycle according to the output pulse signal of the oscillation circuit 30.

In this case, even if one of the right side lamp circuit 15R and the left side lamp circuit 15L is broken, the potential at the connection point between the resistor 25 and the voltage dividing resistor 42 does not become high, so the output terminal of the operational amplifier 41 becomes L level. Therefore, the lamp blinking period of the right side lamp circuit 15R and the left side lamp circuit 15L does not change. In this embodiment, the blinking cycle is shortened only when three or less lamps remain.
In other words, the right lamp circuit 15R and the left lamp circuit 15L
When the above lamp is used as a turn signal lamp, the blinking cycle is shortened when at least one lamp is broken, but when it is used as a hazard lamp, the blinking cycle changes unless five or more lamps are broken. do not do.

[Effects of the Invention] Since the present invention is configured as described above, the following effects are achieved.

That is, even if the reference voltage and the comparison voltage input to the comparator fluctuate due to the voltage fluctuation of the power supply, the zener diode connected in parallel to the voltage dividing resistor that sets the reference voltage allows the reference voltage and the comparison voltage to be compared. Correspondence with and is maintained in an appropriate state, and a stable comparison function can be secured.

Further, in the case of the structure according to the second aspect, the reference voltage can be surely made to follow a large variation of the comparison voltage due to the voltage drop due to the resistance.

Further, when applied to a vehicle lamp blinking device, it is possible to secure a lamp disconnection detection function capable of coping with a large variation in power supply voltage that may occur in a vehicle.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a comparison circuit of the present invention, FIG. 2 is a characteristic diagram showing variations of a reference voltage and a comparison voltage with respect to variations of a power supply voltage in the comparison circuit of the present invention, and FIG. FIG. 4 is a circuit diagram in which an embodiment of the present invention is applied to a vehicle lamp blinking device, and FIG. 4 is a load operating state detection circuit diagram when a conventional comparison circuit is used. 1 ... Operational amplifier (comparator), 2, 3 ... Dividing resistance, 4 ... Reference voltage adjusting circuit, 46 ... Zener diode, 47 ... Resistance, 7 ... Load, 12 ... Operation switch, 15 ... … Vehicle lamp circuit, 20 …… Drive circuit, 30 …… Oscillation circuit, 40 …… Lamp burnout detection circuit, 50 …… Starting circuit

Claims (3)

[Scope of utility model registration request] 1. A reference voltage in which a fluctuating power supply voltage is set by resistance division, and a comparison voltage which fluctuates according to the fluctuation of the power supply voltage in a relationship different from the fluctuation of the reference voltage according to the fluctuation of the power supply voltage. In a comparison circuit including a comparator for comparing the above and outputting according to the comparison result, at least a Zener diode is connected in parallel to the voltage dividing resistor for setting the reference voltage. 2. The comparator is an operational amplifier in which the voltage dividing resistor is connected to one input terminal and the comparison voltage is input to the other input terminal, and a series circuit of a Zener diode and a resistor is used for dividing the voltage. The comparison circuit according to claim 1, wherein the comparison circuit is connected in parallel with the resistor. 3. A vehicle lamp circuit including a plurality of lamps connected to a power supply whose output voltage fluctuates via an operation switch, and a drive circuit having a switching transistor interposed between the operation switch and the power supply. A lamp burnout detection circuit connected to the drive circuit and outputting a signal according to a change in collector-emitter voltage of the switching transistor; and a lamp burnout detection circuit connected to the lamp burnout detection circuit and connected to the drive circuit. An oscillator circuit that changes the frequency of an output pulse signal according to the output of the circuit, the capacitor connected to the power source by the oscillator circuit, and one input terminal connected to the power source side of the capacitor and the other input An operational amplifier in which a terminal is connected to the power source via a voltage dividing resistor and an output terminal is connected to the two input terminals via feedback resistors respectively. And an output terminal of the operational amplifier connected to the drive circuit, the lamp disconnection detection circuit connects one input terminal to the power supply via a voltage dividing resistor, and the operation of the switching transistor. A second input terminal is connected to a connection point between two series voltage dividing resistors, one end of which is connected to the switch side and the other end of which is grounded, and an output terminal is connected to the other input terminal of the operational amplifier. In the vehicle lamp blinking device, comprising: the operational amplifier, the voltage dividing resistor adjacent to the switching transistor and the connection point of the switching transistor are connected to the operation switch, a comparator including the second operational amplifier is provided. In addition, a series circuit of a Zener diode and a resistor is connected in parallel with the voltage dividing resistor connected to one input terminal of the second operational amplifier. Comparator circuit, characterized in that.