JPS5835612A - Stabilized power supply circuit - Google Patents

Abstract

PURPOSE:To obtain a stabilized power supply for a low power source voltage, by making bases of two transistors of a voltage detecting circuit common and making areas of emitters different from each other and setting a desired voltage between bases and emitters. CONSTITUTION:In a voltage detecting circuit, bases of transistors TRs Q1 and Q2 are connected in common, and bases are grounded through a resistance R3 and form a feedback circuit of a follower circuit through a resistance R4. These TRs Q1 and Q2 are designed to have different emitter areas so that collector currents coincide with each other for a set power source voltage. Current mirrors M1, M2, and M3 are provided for the purpose of comparing collector currents of TRs Q1 and Q2 to lead out the output. These current mirrors are connected through collectors of TRs Q10 and Q71, and the output of the voltage detecting circuit is given to the follower circuit of the next stage from this connection point A, and an output voltage is led out from the follower circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stabilized power supply circuit, and particularly to a stabilized power supply circuit in which the output voltage can be freely and easily set over a wide range.

In battery-driven electronic equipment, the power supply voltage is relatively low, and therefore, a stabilized low-voltage power supply is often desired even in a semiconductor integrated circuit to which such a power supply voltage is applied. However, the range of stabilizing power supply circuits used in the past has been limited because the range in which a stable output voltage can be derived is extremely narrow, and there have been problems in putting them into practical use as power supply circuits for a wide variety of electronic devices. .

The present invention has been made in view of the problems of the conventional circuits described above, and provides a stabilized power supply circuit capable of obtaining an output voltage ranging from a low power supply voltage 9, for example, 1.25V to several volts.

The present invention will be described in detail below using the drawings.

The figure is an electrical circuit diagram showing an embodiment of the present invention, which is configured as a so-called bandgap type stabilized power supply circuit. To summarize the present invention, a voltage detection circuit is provided for the applied power supply voltage, and a feedback circuit is added so that the output of this voltage detection circuit corresponds to the set power supply voltage. The voltage detection circuits mentioned above have their bases connected in common.
It operates so that the collector currents of the transistors Q, Q2 match at a set voltage, and both transistors Q=
,Q! The collector currents are respectively input to the follower circuits via current mirrors, and output voltages are derived from the follower circuits, and this output is fed back to the voltage detection circuit to balance the output voltages to the set voltages.

In the figure, the voltage detection circuit first consists of a first voltage detection circuit made of NPN.
transistor Q, and a second transistor Q.

The commonly connected bases are connected to the ground GND via a resistor R3, and also serve as a feedback circuit for a follower circuit to be described later via a resistor R4. Here, as will be described later, the circuits of the first transistor Q1 and the second transistor Q2 are designed so that their collector currents almost match at the level of the set power supply voltage. The emitter areas of both transistors are designed to have different shapes so that a voltage difference Δv0 between the emitters can be obtained.

For example, let the emitter area of each transistor be Eq, , E
qt, it is designed to be EQl:EQ2=1:10.

A resistor R1 (IOKΩ) is connected between the emitter of the first transistor Q and the ground GND, and the emitter of the second transistor Q2 is connected to the first transistor Q through a resistor R2 (IOKΩ).
Connected to the emitter of transistor Q1. A circuit for comparing the collector currents of both transistors and deriving an output is further added to both transistors Q and Q2. That is, for the collector current of the first transistor Q, the first current mirror M and the second current mirror M2
A third current mirror M is provided for the collector current of the second transistor Q. The first current mirror M1 is a PNP whose bases are commonly connected, and whose base is connected to the collector of the first transistor Q.
The second current mirror M2 consists of a third transistor Q3 and a PNP multi-collector fifth transistor QB, and a second current mirror M2 includes a ninth NPN transistor Q whose bases are connected to each other through a series-connected resistor R5 and a resistor R6, and a tenth transistor Q3.
One collector of the fifth transistor Q5 is connected to the collector of the ninth transistor Q9 and the connection point of the resistors Rs and Re.

The third current mirror M is a PNP fourth transistor Q4
and a PNP multi-collector seventh transistor Q7, both PNP transistors Q, . . . Q70 are connected in common and to the collector of the second transistor Q2. One collector of the seventh transistor Q7 is connected to the other collector of the fifth transistor 4Qs, and the other collector of the seventh transistor Q7 is connected to the collector of the tenth transistor Q, , + of the second current mirror M2. ing. At the connection point A, a tenth transistor Q is provided for phase compensation as described later.

A small capacitor C is connected between the base of the .

The first current mirror M1 and the second current mirror M
2 and the third current mirror M are transistors Q, respectively.
8° and the collector of the transistor Q,
From this connection point A, the output of the voltage detection circuit is given to the next stage hollow ant.

The follower circuit is the 11th. 12th゜1st
The first stage consists of 3 transistors Q1t + Q1□, Q, 3, and the 14th stage consists of PNP. 15th. 16th
Transistor Q14 + Qt5 + Qt. The second stage consisting of is connected. The first stage follower circuit and the second stage follower circuit are respectively connected to the 12th stage follower circuit. The 13th transistor Q, 2°Q,s and the 15th . 16th transistor Q151 Qt
The output point A of the voltage detection circuit is connected to the base of the eleventh transistor Qtt. The emitter of the eleventh transistor Q u is connected to the collector of the twelfth transistor Q1□, and is also connected to the base of the fourteenth transistor Q +4 of the second stage Polor circuit. The base and collector of the thirteenth transistor Qrs are connected to a point B where the respective collectors of the fifth transistor Q and the seventh transistor Q are commonly connected. Output voltage E of the stabilized power supply circuit. ut is the 14th) transistor Q of the second stage follower circuit
The output voltage E is derived from the connection point between the emitter of Q +4 and the collector of the fifteenth transistor Q +5. ut is also fed back to the bases of the first transistor Q1 and the second transistor Q via a resistor R4.

A resistor R (27Kfl) is a resistor inserted between the base and collector of the 16th transistor Qte and the ground GND.

Next, the operation of the circuit having the above configuration will be explained.

First, if we find a condition where the collector currents of the first transistor Q1 and the second transistor Q2 match each other as a voltage detection circuit, as will be understood from the following explanation, both transistors Q1.
This is when the base voltage of Qt is approximately 1.25V.

That is, since the emitter areas of the first transistor Q and the second transistor Q2 are designed to be EQt:E'h=1:10, in this state, the base-emitter voltage vB of the first transistor Q is , second transistor Q,
1VBE of is vBE=KT/q@LnIC/Eng. From the equation, it becomes ΔVBo-KT/9·1nlO. Above ΔBg
The value of is approximately 60m when operated in an atmosphere of approximately 20℃.
It becomes V.

That is, 60mV is applied across the resistor R2, which is designed to be 2Ω.
When a current flows such that a voltage of Q1 is applied, the values of the collector currents of the first transistor Q1 and the second transistor Q2 match. In this state, the current from the second transistor Q2 flows into the resistor R1 in addition to the current from the first transistor Q, so that twice as much current flows through the resistor R1. Also, the resistance R
Since the value of 1 is designed to be R,=5R2 for the resistor R2, a voltage of 600 mV is generated at the resistor R1. On the other hand, since a collector current of 30 μA flows through the first transistor Q1, the base-emitter voltage vBE of the first transistor Q1 is in an atmosphere of 20° C. under the condition of β = 100 for a transistor constituting a normal integrated circuit. By applying , it becomes about 650 mV. First transistor Qs + second transistor Q leading to such an operating state
The base potential of 2 is about 1.25V.

Now, since a feedback circuit including a resistor R8 and a resistor R1 is connected to the bases of both transistors Q, , Q, the output voltage '&E. ut, then both transistors Q1
．． Feedback works so that the collector current of Q2- is balanced, and a stable power supply voltage is output as Eout. As is clear from the above equation, if the resistance R4 is designed to be zero, the four-force voltage will be E. ut=1.25V, and the output voltage E by selecting the value of resistor R4. ut can be varied over a wide range.

Now, in the follower circuit, the eleventh transistor Q +t
The emitter current of the fifth transistor Q and the seventh transistor Q? Since it is pulled from the current mirror M4 through the fourth current mirror M4, it becomes equal to the sum of the collector currents of the ninth transistor Q and the tenth transistor Q1 of the second current mirror M2.

Therefore, the output of the voltage detection circuit is
With respect to the current mirror error caused by the influence of the base currents of the transistors Qo and Q1° of the second current mirror M2, it is possible to cancel the error of the current mirror.

In the circuit of the embodiment, the collector of the ninth transistor Q0 is directly connected to the midpoint of the resistors R6 and R6, but it is also possible to insert a diode between them to improve the potential balance.

The circuit of the above embodiment has excellent starting characteristics.

That is, if it does not start when the power is turned on, the pace of the 14th transistor Q+4 from which the output is derived is the 12th transistor Q1□, the i13 transistor Qts
It is not lowered down by the current mirror M4 consisting of. Therefore, the emitter of the fourteenth transistor Q1m rises to a sufficiently high potential, and collector current begins to flow into the first transistor Q and the second transistor Q2, so there is no possibility that it will not start up.

Further, in the circuit of the embodiment, there is no need to perform special phase compensation. That is, transistor Q1. Compared to Q2, the first stage has a large emitter resistance, and the second stage consists of a current mirror, so
Since the gain stage includes only the tenth transistor Qto, it is relatively stable. In consideration of stability when a capacitive element is connected to the output terminal, resistors R6 and R are set as shown in the example.
, connect. In other words, in the case of a current mirror, the impedance on the pace side is low due to the diode characteristics on the pace side, and the first
0 transistor Q,. Even if a capacitor is inserted between the collector e-pace of increase.

As described above, according to the present invention, a stabilized power supply can be obtained for a relatively low power supply voltage, and a stabilized power supply circuit that is very practical for battery-driven electronic equipment can be obtained. Furthermore, the circuit can be started up reliably, does not require complicated phase compensation, and can operate with high reliability.

[Brief explanation of the drawing]

The figure is an electrical circuit diagram showing an embodiment according to the present invention. Q1~Q*a: ) U/distance, R0~Rf: Resistance. C: Capacity agent Patent attorney Aihiko Fukushi

Claims (1)

[Claims] fl+ A first transistor/transistor Q+ and a second transistor Q2 whose emitter areas are different from each other and whose paces are commonly connected, and a first transistor Q whose emitter area is small.
a resistor R1 connected between the emitter of the first transistor and the ground; a resistor R2 connected between the emitters of both transistors; and a current mirror for changing the direction of the collector current of the first transistor Q twice. , a current mirror for changing the direction of the collector current of the second transistor Q2, a follower circuit that connects the collectors of both current mirrors and is supplied with a voltage derived from the connection point, and an output of the follower circuit. Above 1. Second transistor Q8.
A stabilized power supply circuit comprising a circuit that feeds back to the base of Q2, and obtains the output of the follower circuit as an output voltage. (2) The follower circuit is composed of two stages: a first follower circuit consisting of an NPN transistor and a second follower circuit consisting of a PNP transistor, and the load of the first follower circuit is the first follower circuit consisting of a PNP transistor.
The stabilized power supply circuit according to claim 1, wherein the stabilized power supply circuit is generated from the collector current of the second transistor Ql +Q2° via a current mirror. (3) One of the current mirrors that changes the direction of the collector current of the first transistor Q1 or the second transistor Q2 has a resistor connected in series to its base, and a capacitor connected between the pace and collector of the current mirror transistor. A stabilized power supply circuit according to claim (1), characterized in that: