JP2582171Y2 - Pilot lamp lighting circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pilot lamp lighting circuit for a constant voltage circuit having stability with respect to load fluctuation.

[0002]

2. Description of the Related Art There is a constant voltage circuit using a transistor Q and a Zener diode Tz as shown in FIG. In this constant voltage circuit, when a light emitting diode is used as a pilot lamp indicating the operation state, conventionally, a light emitting diode shown in FIG.
As shown in the figure, the light emitting diode D _{1 is connected} to the input side of the constant voltage circuit.
Of connecting the anode, or ground the cathode, or to connect the anode of the light emitting diode D ₂ to the output side of the constant voltage circuit may take the ways to ground the cathode.

[0003]

An invention to be Solved] However, when using the light-emitting diodes D _1, when the light emitting diode D ₁ is lit, the other power consumed by the load on the output side of the constant voltage circuit and the constant voltage circuit , power for lighting the light emitting diode D ₁ also required, power consumption is increased.

Further, when using a light-emitting diode D ₂ of the output side, not only similar power consumption and light-emitting diodes D ₁ is increased, the power amount corresponding to the constant voltage circuit that is consumed by the light emitting diodes D _2, the load The maximum supply power that can be supplied to the vehicle decreases.

The present invention has been made in view of the above problems, and has as its object to provide a pilot lamp lighting circuit that does not increase power consumption as a constant voltage circuit.

[0006]

In order to achieve the above object, the present invention has first and second electrodes and a control electrode, and a current flowing from the first electrode to the second electrode is supplied to the control electrode. A transistor having a first electrode connected to a power supply and a second electrode connected to a load;
A Zener diode connected between the control electrode and a reference potential point, and a resistor connected between the first electrode and the control electrode, comprising, in series with the resistor,
A pilot lamp connected between the first electrode and the control electrode.

[0007]

In the present invention, a current flows through the resistor between the first electrode and the control electrode in order to obtain the Zener voltage of the Zener diode connected between the control voltage of the transistor and the reference potential. At this time, since this current also flows through the pilot lamp, the pilot lamp is turned on.

[0008]

FIG. 1 shows a first electrode of a transistor Q;
For example a collector terminal C, a control electrode, eg, between the base electrode B, pilot lamp, for example a light emitting diode D ₃ and resistor R _B are connected in series. The base terminal B is connected to the cathode of the Zener diode Tz. The anode of the Zener diode Tz is connected to the reference potential point. The collector terminal C is
A second electrode, for example, an emitter terminal E,
Connected to load.

In order to generate a Zener voltage in the Zener diode Tz, although current flows _{I RB} to the resistance _{R B,} the current _{I RB} are generally 10 several mA from a few mA. This current value is sufficient current to turn on the light emitting diode D _3. Therefore, the light emitting diode D
₃ are connected in series with resistor R _B.

[0010] In the constant voltage circuit provided with no light-emitting diodes _{D 3} shown in FIG. 3, if indeed they formed a circuit, the DC input voltage _{(V IN)} 24V, so that the output voltage _{(V out)} the DC 15V Next, the constant of each component is selected. For example, a 2SC type transistor is used for the transistor Q, and a 16V type transistor is used for the Zener diode Tz. Here, for example, to generate a Zener voltage of 16V, the 'current _{I RB} flowing in' resistor _{R B} 2m
In the case of A, the value of the resistor R _B ′ is about 3.9 KΩ. When a DC voltage of 15 V is supplied, 10 mA
Input current is 12
mA.

In the case of this embodiment, the light emitting diode D
In order to light _3, by the value of the resistor _{R B} only and _{3.3k, I RB} maintains 2 mA, input current 12
Maintain mA. Other configurations need not be changed at all from FIG.

[0012] only slightly change the value of such resistor R _B, be newly provided a light emitting diode D _3, can be illuminated it. Further, the voltage and current input to the constant voltage circuit is lower than the rated value, the Zener diode Tz even when it is impossible to generate a Zener voltage, a current flows from the light-emitting diode D ₃ to the base of the transistor. Therefore, although the luminance is lower than in the normal state, the light emitting diode is turned on, so that it is instantaneous that it is not a failure of the constant voltage circuit but a decrease in the input voltage and current. Further, the negative terminal connected to the emitter terminal E
When the load voltage fluctuates, the base voltage of transistor Q
I tried to fluctuate, but the base B has a Zener diode
Since Tz is connected, its voltage does not fluctuate,
The current flowing through the knurled diode Tz fluctuates. This
As a result, the current flowing to the base of the transistor Q fluctuates,
The voltage between the collector C and the emitter E of the transistor Q changes.
And keep the load voltage constant. At this time,
Diode _{D 3,} the current flowing through the resistor _{R B} is almost constant,
For the Zener diode Tz and the base of the transistor Q
Only the proportion of the flowing current changes. Therefore, the load
The light amount of the light emitting diode Tz changes even if
Absent.

[0013]

As described above, according to the present invention, the pilot lamp can be provided without increasing power consumption by lighting the light emitting diode. Sa
In addition, when the input voltage and current are
The current flowing through the light emitting diode is almost
It is constant and lights up with the same brightness. On the other hand, input voltage,
Even if the flow drops below the rated value, the pilot
Although the brightness of the lamp is reduced, it lights up, so that
Is not obtained, the failure of the constant voltage circuit or the fluctuation of the load
And immediately detect a drop in input voltage and current
You. Also, if the specified output voltage cannot be obtained, the pilot
If the lamp does not light, the input voltage and current are not supplied.
Or that the Zener diode is open immediately
I understand. Also, the pilot lamp is on,
If the specified output voltage cannot be obtained, transistor failure
Or that the Zener diode is short-circuited
You. Therefore, if a predetermined output voltage cannot be obtained,
Iodine conditions, i.e. normal brightness or normal
To see if it is too dark or not lit.
Can be identified .

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of a pilot lamp lighting circuit according to the present invention.

FIG. 2 is a circuit diagram of a conventional pilot lamp lighting circuit.

FIG. 3 is a circuit diagram of a conventional constant voltage circuit.

[Explanation of symbols]

D ₃ light-emitting diode (pilot lamp) Tz Zener diode R _B resistance Q transistor C collector terminal (first electrode) B-based terminal (control electrode) E emitter terminal (second electrode)

Claims (1)

(57) [Scope of request for utility model registration] A first electrode, a second electrode, and a control electrode;
The current flowing from the first electrode to the second electrode is supplied to the control electrode.
The first electrode is connected to a power supply.
A transistor having a second electrode connected to a load, and a zener connected between the control electrode and a reference potential point.
A diode and a resistor connected between the first electrode and the control electrode
And a resistor connected in series with the resistor.
Having a pilot lamp connected between the
And a pilot lamp lighting circuit.