JPH04364476A - Voltage confirmation circuit - Google Patents

Abstract

PURPOSE:To confirm the degree of the magnitude of an input voltage with a few number of parts without using special power supply. CONSTITUTION:A junction type FET 10, which is connected so that the voltage across the gate and the source becomes constant, and a light emitting diode 9 are connected in series. The series circuit is connected across two terminals 8 and 11. An input voltage E is applied across two terminals. The magnitude of the input voltage is confirmed based on the lighting and non-lighting of the light emitting diode 9.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage checking circuit suitable for use in checking, for example, whether or not a DC low voltage power supply is generating voltage or whether the wiring of a power supply section of an electric circuit is good or not.

0002

[Prior Art] Conventionally, in order to check whether voltage is being generated from a DC voltage power supply or whether power is being supplied to the target point, a voltage tester, multimeter, oscilloscope, etc. measuring device was used.

However, if a large number of power supplies are used and the status of these power supplies is to be checked at the same time, it is necessary to prepare as many voltage measuring instruments as the required number of channels, which takes up space and energy. This method is not only disadvantageous in terms of cost, but also requires time to confirm since each voltage value must be read and determined.

On the other hand, a circuit using a comparator as shown in FIG. 10 has also been used as a voltage checking circuit for determining whether the output voltage is within a predetermined range.

In FIG. 10, reference numerals 3 and 4 indicate operational amplifiers that constitute the first and second comparators, which in this example are constructed of one-chip IC. and,
1 and 2 are input terminals, these input terminal 1 and input terminal 2
A voltage E to be checked is supplied between the two. The input terminal 1 is grounded, and the input terminal 2 is connected to one input terminal of the first comparator 3 and the other input terminal of the second comparator 4.

Further, resistors R1, R2 and R3 are connected in series between the power supply terminal 5 to which the DC voltage Vcc is supplied and the ground, and the connection point between the resistors R1 and R2 is connected to the comparator 4.
is connected to one input terminal of resistor R2 and resistor R3.
The connection point between the two terminals is connected to the other input terminal of the comparator 3.

The outputs of the comparators 3 and 4 are supplied to the input terminal of an OR gate 6, and a resistor R4 and an LED (light emitting diode) 7 are connected in series between the output terminal of the OR gate 6 and the power supply terminal 5. has been done. Resistor R
When the resistance values of 1 to R3 are represented by R1 to R3, respectively, the voltage E is Vcc・R3/(R1+R2+R3) <E<Vc
When it is within the range of c·(R2+R3)/(R1+R2+R3), the outputs of comparators 3 and 4 both become low level "0". Therefore, since the output of the OR gate 6 also becomes "0", the LED 7 lights up. On the other hand, if voltage E is out of that range, comparator 3
Alternatively, one output of the gate 4 becomes high level "1", and the output of the OR gate 6 also becomes "1", so that the LED 7 is turned off. That is, depending on whether the LED 7 is lit, it can be confirmed whether the voltage E is within a predetermined range.

[0008]

[Problem to be solved by the invention] However, FIG.
The verification circuit in the example still has a large number of parts and requires a power supply to operate the circuit, so if there are many channels of power supply to be verified, a relatively large space is required and the cost of the verification circuit is high. There is an inconvenience.

In view of the above points, it is an object of the present invention to provide a voltage checking circuit that can check the magnitude of input voltage with a small number of parts and without using a dedicated power supply. .

0010

[Means for Solving the Problems] A voltage checking circuit according to the present invention, as shown in FIG. and a light emitting diode (9) are connected in series, and this series circuit is connected to two terminals (8, 11).
A test voltage E is applied between these two terminals.

Furthermore, as shown in FIG.
Junction type FE connected so that the source-to-source voltage is constant
A Zener diode (17) may be further connected in series to the series circuit of the T (15) and the light emitting diode (16).

Furthermore, in the present invention, as shown in FIG. , 11) and apply the voltage E to be tested to these two terminals.

[0013]

[Operation] According to the present invention having the above configuration, for example in the case of the example shown in FIG. Since the diode (9) starts emitting light, the test voltage E can be easily adjusted without using a dedicated power supply.
You can check the approximate range of

[0014] Furthermore, since a junction FET connected so that the voltage between the gate and source is constant becomes a constant current element, even if the voltage E to be tested becomes large, the current flowing through the light emitting diode (9) does not increase beyond a predetermined degree. Therefore, there is no significant influence on the source of the voltage E to be tested.

Furthermore, when a Zener diode (17) is further connected in series with the junction FET (15) and the light emitting diode (16), the voltage to be tested E is
When the sum of the on-voltage of T(15), the on-voltage of the light-emitting diode (16), and the Zener voltage of the Zener diode (17) is exceeded, the light-emitting diode (16) starts emitting light. In this case, by changing the Zener voltage of the Zener diode (17), the light emitting diode (1
6) The light emission starting voltage can be set arbitrarily.

Furthermore, when a plurality of confirmation circuits are provided between terminals 8 and 11, the light emission starting voltage of the light emitting diode of each confirmation circuit is determined by the ON voltage of the FET, the ON voltage of the light emitting diode, and the Zener voltage of the Zener diode. However, by making this light emission start voltage different for each confirmation circuit, the light emission start voltage of the light emitting diode of each confirmation circuit can be made different. Thereby, it can be confirmed whether or not the voltage to be tested E is within a predetermined voltage range.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a voltage confirmation circuit according to the present invention will be described with reference to FIGS. 1 to 9.

FIG. 1 shows a basic unit of an embodiment of the present invention, in which a series circuit of a junction FET 10 and an LED 9 is connected between input terminals 8 and 11 of the voltage to be tested. That is, in the basic unit of this example, the cathode of the LED 9 is connected to one input terminal 8, and the anode of the LED 9 is connected to the N-channel junction FET 10.
The source of this junction FET 10 is connected to the other input terminal 11, and the drain of this junction FET 10 is connected to the other input terminal 11.

In this example, the gate and source of the junction FET 10 are short-circuited and the gate-source voltage VGS
= 0, and is constant. Then, an input voltage E to be checked is applied between the input terminal 8 and the input terminal 11.

Generally, as shown in FIG. 2(A), FET
The horizontal axis is the drain-source voltage VDS, and the drain current I
When D is taken as the vertical axis, as the gate-source voltage VGS changes, the voltage VDS-current ID characteristics change as shown in characteristic curves 12A, 12B, 12C, . . . . That is, by keeping the gate-source voltage VGS constant, the FET operates as a constant current element. In this example,
Constant current characteristics when the gate and source are short-circuited and the gate-source voltage VGS is zero, that is, characteristic curve 12
A constant current characteristic represented by C is used.

Furthermore, as shown in FIG. 2(B), if the voltage V applied to the LED is plotted on the horizontal axis and the current I flowing through it is plotted on the vertical axis, the voltage-current characteristic of the LED is steep like that of a Zener diode. It can be expressed as a characteristic curve with a sharp rise. And from that steep rising voltage, LE
D starts emitting light.

The basic unit of this example includes a junction type FET 10 having the characteristics shown by the curve 12C in FIG.
), the voltage-current characteristics of the basic unit are as shown by the characteristic curve in FIG. 2C. That is, if the input voltage E and current I of the basic unit are plotted on the horizontal and vertical axes of FIG. ,
When the current I starts to flow and the LED 9 starts to light up, and the input voltage E increases further, the current I becomes a constant current due to the constant current of the junction FET 10, and the brightness of the LED 9 becomes a constant brightness according to the constant current. become.

In this case, the change range VR of the input voltage E from when the current I rises until it reaches a constant current is the LED 9
This is the area where the brightness of
The smaller R is, the better the detection sensitivity to the input voltage E is.

As described above, it is possible to confirm whether the input voltage E is higher or lower than the ON voltage of the LED 9, depending on whether the LED 9 lights up or not. According to the configuration of this example, only the LED 9 and the junction FET 10 are used, and the configuration is extremely simple and compact, and has the advantage of not requiring a dedicated power source. Further, since the current flowing through the junction FET 10 is limited, there is an advantage that a large current will not flow even if the input voltage E becomes high.

In this case, the brightness of the LED 9 is the same as that of the junction type FE.
It is determined by the current limited by T10. Therefore, the LED
9 more brightly, the drain current ID value IDS when the gate-source voltage VGS is zero
Use a FET with large S or multiple FETs
should be connected in parallel.

Furthermore, in order to increase the detection sensitivity with respect to the input voltage E, it is desirable to make the variation width VR in FIG. . but,
An FET with a small variation width VR and a large drain current IDSS when the gate-source voltage VGS is zero cannot be easily obtained.

For example, with reference to FIG. 3(A), a general FE
To explain the characteristics of T, the drain current IDSS is
As the values increase from SS1 to IDSS3, as shown by characteristic curves 13A to 13C, the width of change in the rise becomes wider from VR1 to VR3, and the sensitivity tends to deteriorate.

[0028] Improving the sensitivity and reducing the current IDSS
In order to increase the current IDSS, a small F
A plurality of ETs may be connected in parallel. Specifically, the current I
The characteristics of drain-source voltage VDS and drain current ID of one FET with small DSS are shown in Figure 3(B).
If the characteristic curve 14A of the FET is
The overall characteristics when two to four of them are connected in parallel can be represented by characteristic curves 14B to 14D, respectively. As is clear from FIG. 3B, by connecting a plurality of FETs in parallel, the drain current IDSS can be substantially arbitrarily increased while the variation width of the rise is kept small.

By the way, the on-voltage of an LED is generally 1.
It is about 5V to 2V, and in the configuration of FIG. 1, the voltage to be checked depends only on the ON voltage of the LED 9, and the range of the voltage to be tested is limited. Furthermore, the basic unit in the example shown in FIG. 1 above confirms whether the input voltage E is above a certain voltage by lighting an LED, but it is also possible to check whether the input voltage E is within a certain range or not. It is not possible to confirm whether or not.

[0030] In this invention, as shown in the embodiment described later, by connecting a Zener diode to the LED and selecting its Zener voltage, the light emission start voltage of the LED can be arbitrarily set, thereby solving the former problem. I'm trying to solve it.

The latter problem is solved by using a plurality of basic units in which the LEDs have different light emission start voltages.

FIG. 4 shows an embodiment in which both of the above two problems are solved. This example is an example in which two basic units are used as confirmation circuits. In this Figure 4,
The gate of an N-channel junction FET 15 whose gate and source are short-circuited is connected to the input terminal 11, and the FE
The source of T15 is connected to the anode of a green LED 16 that emits green light, the cathode of this green LED 15 is connected to the cathode of a Zener diode 17, and the anode of this Zener diode 17 is connected to the input terminal 8. A first confirmation circuit is formed by a series circuit of the FET 15, the green LED 16, and the Zener diode 17.

Further, in parallel with the first confirmation circuit, between the input terminals 11 and 8, a circuit configured similarly to the first confirmation circuit is provided.
A second confirmation circuit consisting of a series circuit of the junction FET 18, a red LED 19 that emits red light, and a Zener diode 20 is connected. And input terminal 8 and input terminal 11
An input voltage E to be checked is applied between. In this case, the Zener voltage Vz of the Zener diode 17
Zener voltage Vz2 of Zener diode 20 than 1
The Zener voltage is selected so that .

The operation of the example shown in FIG. 4 will be explained with reference to FIG. As the input voltage E increases, the input voltage E becomes the voltage E1.
When the input voltage E reaches the voltage E2, the green LED 16 lights up, and the red LED 19 lights up when the input voltage E reaches the voltage E2.
starts to emit light.

The voltage E1 is approximately equal to the sum of the on-voltage of the FET 15, the on-voltage of the green LED 16, and the Zener voltage Vz1 of the Zener diode 17, and the voltage E2 is
The on voltage of ET18 and the on voltage of red LED19,
It is approximately equal to the sum of the Zener voltage Vz2 of the Zener diode 20.

In this way, according to the example of FIG.
When ED16 and 19 are off, the input voltage E
is smaller than the voltage E1, and when only the green LED 16 is lit, the input voltage E is between the voltages E1 and E2, and when the two LEDs 16 and 19 are lit, the input voltage E is greater than the voltage E2. This can be confirmed.

Various modifications can be made to the embodiment of FIG. 4. For example, in the modification shown in FIG. 6A, the cathode of the red LED 19 is connected to the anode of the green LED 16 in the example shown in FIG. 4, and the Zener diode 20 is removed. In this example, the FET 15, the light emitting diode 16, and the Zener diode 21 form a first verification circuit, and the FET 18, the light emitting diodes 19 and 16, and the Zener diode 21 form a second verification circuit. A circuit is formed.

Therefore, in the example of FIG. 6(A),
The voltage E1 is the ON voltage of the FET 15 and the green LED 16.
The voltage E2 is approximately equal to the sum of the on voltage of the FET 18, the on voltage of the red LED 19, and the Zener voltage Vz3 of the Zener diode 21, and the voltage E2 is equal to the sum of the on voltage of the FET 18, the on voltage of the red LED 19, and the Zener voltage Vz3 of the
6 and the Zener voltage Vz3 of the Zener diode 21.

In addition, in the modification shown in FIG. 6B, the cathode of the red LED 19 is connected to the anode of the green LED 16 via the Zener diode 22 in the example shown in FIG. It is designed to be connected to the input terminal 8. In this example, the FET 15, the light emitting diode 16,
A first confirmation circuit is formed by the Zener diode 23, and the FET 18 and the light emitting diodes 19 and 1
6 and Zener diodes 22 and 23 form a second verification circuit.

Therefore, in the example of FIG. 6(B),
The voltage E1 is the ON voltage of the FET 15 and the green LED 16.
The voltage E2 is approximately equal to the sum of the on voltage of the FET 18, the on voltage of the red LED 19, the Zener voltage Vz5 of the Zener diode 22, and the on voltage of the green LED 16. , Zener voltage V of Zener diode 23
Almost equal to the sum with z4.

Next, regarding the second embodiment of the present invention, FIG.
This will be explained with reference to FIG. In this example, the present invention is applied to a simple tester for checking in which of four voltage ranges the power supply voltage of a circuit exists.

FIG. 7 shows a voltage confirmation circuit of the simple tester of this example. In FIG. 7, three confirmation circuits configured similarly to the above-described confirmation circuit are connected in parallel between input terminal 11 and input terminal 8. In other words, an N-channel junction FET 24 whose gate and source are short-circuited.
A. A first confirmation circuit is formed by connecting an LED 25A and a Zener diode 26A in series, and a second confirmation circuit is formed by connecting a junction FET 24B, an LED 25B, and a Zener diode 26B in series in parallel with the first confirmation circuit. The circuits are connected and the junction type F is connected in parallel with these checking circuits.
ET24C, LED25C and Zener diode 26
A third confirmation circuit formed by connecting C in series is connected. Then, an input voltage E as a power supply voltage is applied between the input terminal 8 and the input terminal 11.

In this example, the power supply voltage is, for example, +5V.
An example of a simple tester used to check whether the voltage is +12V, +12V, or higher will be explained below.

For example, the ON voltage of FETs 24A to 24C is 0.5V, and the ON voltage of LEDs 25A to 25C is 1.8V.
When the Zener voltages of the Zener diodes 26A, 26B, and 26C are respectively Vza, Vzb, and Vzc, and the margin is set to 0.5V, the Zener voltage in this example is determined as follows.

Vza=5-(0.5+1.8)-0.5=2
．． 2[V] Vzb=12-(0.5+1.8)
-0.5=9.2 [V] Vzc=13-(0.
5+1.8)-0.5=10.2[V] If each Zener voltage is set in this way, as shown in FIG. 8, when the input voltage E reaches E3, which is near 4.5V, the current I increases, LED25A lights up, and the input voltage E becomes 11.5V.
When reaching E4, which is near , the current I increases and the LED
When LED 25B lights up and the input voltage E reaches E5, which is around 12.5V, the current I increases further and LED 25C
lights up.

Therefore, according to the simple tester of FIG.
Depending on the lighting state of the LEDs 25A to 25C, the input voltage E changes from 0V to +5V, +5V to +11.5V, +11.
It is possible to easily confirm in which of the four categories, 5V to +12.5V, and +12.5V or more, the voltage exists.

Next, a third embodiment of the present invention is shown in FIG. 9(A).
This will be explained with reference to and (B). This example is a voltage confirmation circuit that simultaneously confirms multiple types of power outputs.

In the example of FIG. 9(A), a junction type FE whose gate and source are short-circuited to the input terminal 11 is connected.
Connect the drains of T27 and 28, and connect one FET27
The source of the FET 28 is connected to the input terminal 8 through the two green LEDs 30 and 31, and the source of the other FET 28 is connected to the red LED.
It is connected to the source of one of the FETs 27 via D29. Since a low voltage Zener diode does not have good characteristics, the green LED 31 on the input terminal 8 side is used in place of the Zener diode. Applying the input voltage E between the input terminals 8 and 11 is the same as in the above example.

Furthermore, in the example of FIG. 9(B), the FET
The cathode of the green LED 30 connected to the source of the LED 27 is connected to the input terminal 8 via Zener diodes 32 and 33, each having a Zener voltage of about 5.1V. The other configurations are the same as the example in FIG. 9(A).

Assuming that the FET on-voltage is 0.5V and the LED on-voltage is 1.8V, according to the example circuit of FIG. 9(A), when the input voltage E becomes about 4.1V, the green LED3
0 and 31 are lit, and when the input voltage E reaches approximately 5.9V, the red LED 29 is lit. Similarly, according to the circuit shown in FIG. 9B, the green LED 30 lights up when the input voltage E reaches about 11.5V, and the red LED 29 lights up when the input voltage E reaches about 14.3V.

For example, one circuit of FIG. 9(A) and one circuit of FIG. 9(B)
) By using two circuits with different polarities of the input terminals, the status of three types of power supply voltages, +5V, +12V, and -12V, can be checked with a simple circuit configuration and without using a dedicated power supply. be able to. Such a voltage checking circuit can be effectively used as a checker when testing the state of a power supply device after a vibration test, a knock test, an insulation/voltage test, or aging.

[0052] In the above embodiment, the FET, L
The connection order of ED and Zener diode is arbitrary.
A switching diode or a normal diode or the like can also be used instead of the Zener diode.

Furthermore, although an N-channel FET is used as the junction FET in the above embodiment, it is clear that a P-channel junction FET can be used as well.

[0054]

As described above, according to the present invention, it is possible to check the magnitude of input voltage with a small number of parts and without using a dedicated power supply.

Furthermore, when a Zener diode is connected in series with the FET and the light emitting diode, the range of input voltage to be checked can be arbitrarily set by selecting the Zener voltage.

Furthermore, when a plurality of confirmation circuits are connected between the terminals to which input voltage is applied, the light emission starting voltage of the light emitting diode of each of these confirmation circuits is made different to ensure that the input voltage is within a predetermined range. You can easily check whether or not.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a basic unit of an embodiment of the present invention.

FIG. 2 is a diagram for explaining characteristics of the basic unit in FIG. 1;

FIG. 3 is a characteristic diagram for explaining an improved example of the present invention.

FIG. 4 is a circuit diagram showing an embodiment of a voltage confirmation circuit according to the present invention.

FIG. 5 is a diagram showing characteristics of the example of FIG. 4;

FIG. 6 is a circuit diagram of a modification of the example of FIG. 4;

FIG. 7 is a circuit diagram of another embodiment of the invention.

FIG. 8 is a diagram showing characteristics of the example of FIG. 7;

FIG. 9 is a circuit diagram of another embodiment of the invention.

FIG. 10 is a circuit diagram of a conventional example.

[Explanation of symbols]

9 LED 10 Junction type FET 15 Junction type FET 16 Green LED 17 Zener diode 18 Junction type LED 19 Red LED 20 Zener diode

Claims (4)

[Claims] Claim 1: A junction FET connected so that the gate-source voltage is constant and a light emitting diode are connected in series, and one end and the other end of the series circuit of the junction FET and the light emitting diode are connected in series. A voltage confirmation circuit that applies a voltage to be tested and confirms the voltage to be tested using the light emitting diode. 2. A Zener diode is connected in series with the junction FET and the light emitting diode, and a voltage to be tested is applied across the series circuit.
Voltage confirmation circuit described. 3. A plurality of confirmation circuits each formed by connecting a junction FET and a light emitting diode in series, which are connected so that the gate-source voltage is constant, are connected between two terminals, respectively. and applying a voltage to be tested between these two terminals, lighting up the light emitting diodes of the plurality of confirmation circuits.
A voltage confirmation circuit configured to confirm the voltage to be tested depending on the non-lighting state. 4. The plurality of confirmation circuits are connected to the junction type FE.
4. The voltage checking circuit according to claim 3, further comprising a Zener diode connected in series with the T and the light emitting diode.