JPS62159209A - Power supply circuit - Google Patents

Abstract

PURPOSE:To attain the application of a Zener diode of small capacity by connecting a transistor between the positive and negative lines of a DC power supply and then the Zener diode to the base of the transistor respectively. CONSTITUTION:The collector (c) and the emitter (e) of a transistor TR5 are connected between the lines at the positive and negative sides 2A and 2B of a DC power supply 2 which supplies the electric power to an electronic circuit 1. While the base (b) of the TR5 is connected to the positive line via a Zener diode 4. Thus the greater part of current flows via the TR5 when the voltage of the power supply 2 has fluctuation and the voltage of the positive side line is set sat a high level. At the same time, a small current flows to the energized diode 4 via the base (b) in response to the amplification factor of the TR5. As a result, a Zener diode of small capacity is available to prevent the rise of the supplied voltage caused by the fluctuation of the power supply voltage.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electronic circuit σ)'tM, a source circuit, and
This invention relates to a power supply circuit suitable for an electronic circuit VC having a relatively large specified voltage and a relatively large current.

[Background of the invention]

In recent years, electronic circuits have come to be used in many fields,
Along with this, it has become safe to obtain DC voltage from a nearby source. Generally, electronic circuits are configured to operate at a predetermined specified voltage, and therefore rely on a source 1 that can stably supply a specified voltage.

However, it is difficult to have such a power source nearby, and in most cases, you have no choice but to use a power source with large voltage fluctuations.

First, if the voltage applied to the electronic circuit is too high, the electronic circuit may be damaged. In order to avoid such a situation, a power supply circuit that obtains a constant voltage using a Zener diode has conventionally been provided. This will be explained with reference to FIG.

Figure 2 is a circuit diagram of a conventional "a [, 1g circuit.
.

2B are a positive side terminal and a negative side terminal of the DC power supply 2, respectively. 3 is a resistor connected by VC between the two positive 1ll111y'J children and 1 and the child circuit 1, and 4 is a Zener diode.

In the above '#ff, source circuit N5, the voltage of the 1-page current W2 fluctuates, and when the voltage at the connection point CCI) between the Zener diode 4 and the positive 911j line rises to exceed the Zener voltage of the Zener diode 40, the Zener diode 4 conducts and current flows, thereby suppressing the voltage at point C (voltage applied to electronic circuit IK) from increasing. Further, the electric current flowing through the Zener diode 4 is suppressed by the resistor 3, so that the Zener diode 4 will not be damaged.

By the way, in the electronic circuit 1, the current is consumed at σ), so the resistance value of the resistor 3 is made as small as possible.
Is it necessary to reduce the voltage drop caused by this?

However, if the resistance value of the resistor 63 is made small, the current will become thick when the Zener diode 4 becomes conductive (and there is a risk that the Zener diode 4 will be destroyed. When the current is large, it is necessary to use a large capacity Zener diode 4, but of course there is a limit to the capacity of the Zener diode.In the end, the conventional computer circuit shown in Fig. 2
There is a drawback that it cannot be used when the current consumption of the electronic circuit 10 is large or when the voltage at point C becomes considerably high due to voltage fluctuations in the DC source 2.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply circuit that eliminates the drawbacks of the prior art described above and can use a Zener diode with a small capacity.

[Summary of the invention]

In order to achieve the above objectives, the unexploded E! A is II! fi
The special feature is that the emitter and collector of the transistor are connected to the positive line and the negative line of the power supply, and a Zener diode is connected between the base of the transistor and the positive or negative line.

[Embodiments of the invention]

The present invention will be explained below based on the illustrated embodiments.

FIG. 1 is a circuit diagram of the wake-up source circuit Q according to the present invention. In the figure, parts that are the same as those shown in FIG. 2 are given the same reference numerals, and explanation thereof will be omitted. 5 is a transistor whose collector C is connected to the positive 11411 line of the power supply, and
Emitter e is also connected to the negative line. 4' is a Zener diode used in this embodiment, and its both ends are connected to the positive line and the transistor 50 pace bK, respectively.
It is connected.

When the voltage of the DC power supply 2 is lower than the voltage (Zena voltage) specified by the Zener diode 4', the Zener diode 4
' and transistor 5 are not conductive, and the voltage is directly applied to the 'electronic circuit IK'. When the voltage at point C exceeds the zener voltage of the zener diode 4' as the voltage at the DC power source 20' fluctuates, the zener diode 4' becomes exclusive, pressing 1 line, zener diode 4', transistor 50 pace b, ) Current flows through the emitter e of the transistor 5 and the negative line.

This '#tK' is directed to the base of transistor 5, transistor 5 becomes conductive, and the positive full line is connected to collector C of transistor 5, emitter e of transistor 5.
1. A ct flow flows through the negative side line. Therefore, the voltage at point C is always maintained at the Zener voltage, and even if the voltage of the DC power supply 20 fluctuates, the electron (envelope l) is maintained.

Here, 1σ galvanic current? The voltage of j$2- is 3, and the resistance is 63σ
The resistance value is R, the Zener voltage is Vn (V□〉■,),
The consumption *light of electronic circuit 1 is expressed as 1, the voltage between the pace and emitter of transistor 50 is Vb, and the pace current and collector current of transistor 5 are Ib and Is, respectively.

Let the current amplification factor of transistor 5 be hFll. Now, if we consider the case where the voltage at point C increases due to fluctuations in the DC power source 2 and the transistor 5 becomes conductive, the excess current flow due to the voltage increase will be as follows. By the way, the collector current Is of transistor 5
is l6=11□・engine.

Therefore, most of the excess current 1' flows as the collector current of the transistor 5, and the pace 'FIL Drt
Ig is extremely small. That is, the current flowing through the Zener diode 4' is extremely small, and therefore the Zener diode 4' can have a capacity of 1 (J), which is as small as σ).

〔Effect of the invention〕

As described above, in the present invention, the collector and emitter of the transistor are connected between the positive and negative lines of the direct current 'tir' and the helix.
Since a zener diode is connected to the pace of the transistor, the electronic circuit can be protected using a zener diode with a small noise level, and it can also be used in an electronic circuit with a large current consumption without any problems. Furthermore, it can also be used in DC areas with large voltage fluctuations.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a power supply circuit according to an embodiment of the present invention, and FIG.
The figure is a circuit diagram of a conventional power supply circuit. 1...Electronic circuit, 2...DC power supply, 3
...Resistor, 4'...Zena diode, 5...Transistor Fig. 1 Fig. 2

Claims (1)

[Claims] In a power supply circuit that connects a DC power source to an electronic circuit that operates at a predetermined voltage via a resistor, a transistor whose collector and emitter are connected to the positive and negative sides of the DC power source, and a base of this transistor and the DC power source are connected. A power supply circuit comprising a Zener diode connected to one side of a power supply.