JPH01241608A - Power source circuit - Google Patents

Abstract

PURPOSE:To output a voltage, which corresponds to a supplying power source voltage, by driving first and second transistors with a fifth transistor, which goes to be active with the reference voltage of a reference voltage generating part when the supplying power source voltage goes over the reference voltage, and driving ninth-eleventh transistors with the driven first transistor. CONSTITUTION:When the supplying power source voltage, which is impressed to a power source supplying terminal 1, goes over the reference voltage, the fifth transistor Q5, to which the reference voltage is impressed by a reference voltage generating part 4, is made active. The first and second transistors Q1 and Q2 are driven by the fifth transistor Q5, which is made active, and the ninth-eleventh transistors Q9, Q10 and Q11 are successively driven by the fifth transistor Q5. Thus, an output voltage rises when the supplying power source voltage is low such as the reference voltage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention generates and supplies constant voltage power from an unstable power supply, and even when the voltage of the power supply falls below a predetermined value, the voltage of the power supply remains constant. The present invention relates to a power supply circuit that stably lowers the voltage of a constant voltage power supply according to the voltage drop.

[Conventional technology]

FIG. 3 is a circuit diagram showing this type of conventional power supply circuit, and FIG. 4 is a characteristic diagram showing the operation of the conventional example shown in FIG.

PNP) transistor Q21. Q22 constitutes a constant current circuit, is supplied with a power supply voltage Vcc via a power supply terminal l, and supplies current to each of the NPN transistors Q231Q24. A resistor R21 connects the emitters of the NPN transistors Q 23 and 924 to ground via the reference terminal 3. The reference voltage generator 4 applies a reference voltage Vr to the base of the NPN transistor Q23 when the supply voltage Vcc becomes equal to or higher than the reference voltage Vref.
Apply ef. The base of the transistor Q'2S is N
The collector is connected to the collector of a PN transistor Q22, the collector is connected to the power supply terminal l via a resistor R22, and the collector of an NPN transistor Q26 whose emitter is diode-connected is connected, respectively. NPN) The emitter of transistor Q26 is a diode-connected NPN transistor Q.
2? In the collector of the NPN) transistor Q2? The emitter of is a diode-connected NPN transistor Q28
are connected to their respective collectors. A resistor R24 connects the emitter of the transistor Q28 to the reference terminal 3. The NPN transistor Q29 has a base connected to the emitter of the NPN transistor Q28, a collector connected to the power supply terminal 1 via the resistor R23, and an emitter connected to the reference terminal 3. PNP) transistor Q3o is
The base is connected to the collector of the transistor Q 29 (NPN), the emitter is connected to the power supply terminal 1, and the collector is connected to the stabilized voltage output terminal 2. Resistor R2S is PNP
) The collector of the NPN transistor Q3o is connected to the base of the NPN transistor Q24, and the resistor R26 connects the base of the NPN transistor Q24 to the reference terminal. A load resistance RL is connected between the stabilized voltage output terminal 2 and the reference terminal 3.
is connected.

Next, the operation of this conventional example will be explained with reference to FIG.

When the unstable supply power supply voltage Vcc becomes larger than the reference voltage V ref and satisfies equation (1), the output voltage Vo rises.

V CC” V IIE 2g + V III 2B
+ V at 27 + V 11126 + Vct
25+ I CQ2SX R2244Vnt+ Vct
25+ I (jQ2sx R22= Va...
・(1) Rif! L/, Vai:2g, Vat2B,
VBt27 and Vat26 are the base-emitter voltages of the transistors Q29 + Q28 * Q27 + Q26, respectively, and V IIE = Vat2g = Va
g28='Lag27=Vat26, Vct2s is the collector-emitter saturation voltage of transistor Q2S, I
CQ2S is the collector current of transistor Q2S.

As the supply power supply voltage Vcc increases beyond the voltage Va, the output voltage Vo also increases in proportion. and supply voltage V
When cc exceeds the voltage shown by equation (2), the output voltage V
o stably becomes the voltage Vsr shown by equation (3).

Vcc= VCE30+ V ref
R2S/R26)=■-・・・・・・(2) However, Vct3o is the collector-emitter saturation voltage of transistor Q30 Vo =Vref X (1+R2S/R26) =V
3T...(3) In the case of this power supply circuit being a basic bandgap reference circuit as a reference voltage circuit, the reference voltage Vref is approximately Vref=2XV, and the error amplifier transistors Q23 and 924 The base potentials are the same. Therefore, the base potential VB25 of the transistor Q25 in the drive circuit is 2XV! It is necessary that 1t<VB25, and if the base potential becomes 2XVBt≧Q2S, the transistor Q24 of the error amplifier circuit will be saturated.
Taking into account load current, resistance, transistor VBE variations, and temperature characteristics, 2 X Vnt<V!
To always satisfy the relationship of 125, transistors Q26 + Q27 are used as level shifters in the output stage drive circuit.
r It is necessary to connect Q211 with a diode. Since VBE of the transistor has a negative temperature coefficient, when the temperature decreases, the output voltage Vo will not rise unless the supply voltage Vcc satisfies equation (4).

VCC≧((4VBE+VCE2S+ I CQ2SX
R22)=V,,...(4) When the load current further increases, the collector current ICQ7S of transistor Q2S also increases, and each transistor Q29
・Q2El・Q2? - Since the Vat of Q26 and Q2S also increases, it can be seen that the output voltage Vo will not rise unless formula (5) is satisfied.

Vcc≧((4Vnt+Vct25+ ICQ2SXR
22) xR2H) = V, S+5 (ΔV-n+ΔI IF',) IX R2
H)=Vc
---Axis (5) [Problem to be solved by the invention] In the conventional power supply circuit described above, when the voltage of the supply power supply voltage Vcc is low, the output voltage Vo is not outputted, and conditions such as temperature drop overlap. The characteristics further deteriorate, and even if the supply power supply voltage Vcc decreases considerably, the supply power supply voltage Vc
The disadvantage is that it cannot satisfy the desire to output a voltage according to c.

[Means to solve the problem]

The power supply circuit of the present invention includes first and second resistors each having one end connected to a power supply terminal; a first transistor of a first conductivity type, the ivy of which is connected to the other end of the first resistor, the emitter of which is connected to the other end of the second resistor, and the base and collector of which are connected to the base of the first transistor; connected first
a second transistor of a conductivity type; third and fourth resistors each having one end connected to a power supply terminal; and a third transistor of a first conductivity type having an emitter connected to the other end of the third resistor. with a transistor.

The emitter is connected to the other end of the fourth resistor, and the base is connected to the other end of the fourth resistor.
The first transistor connected to the base and collector of the transistor
a fourth transistor of a second conductivity type, the collector of which is connected to the collector of the second transistor;
a sixth transistor of a second conductivity type connected to the collector of the fifth transistor; a fifth resistor whose other end is connected to the reference terminal at the emitter of the sixth transistor; and when a voltage higher than the reference voltage is applied to the power supply terminal, the reference voltage is applied to the base of the fifth transistor. a seventh transistor of a second conductivity type, the collector of which is connected to the collector of the fourth transistor;

a sixth resistor with m connected to the emitter of the seventh transistor and the other end connected to the reference terminal;

a collector connected to the collector of the first transistor;
an eighth transistor of a second conductivity type whose base is connected to the base and collector of the seventh transistor; and a seventh transistor whose one end is connected to the emitter of the eighth transistor and the other end is connected to the reference terminal. a ninth transistor of a second conductivity type whose base is connected to the collector of the eighth transistor; and an eighth transistor whose one end is connected to the power supply terminal and the other end is connected to the collector of the ninth transistor.
a tenth transistor of a second conductivity type, the base of which is connected to the emitter of the ninth transistor, the emitter of which is connected to the reference terminal, one end of which is connected to the power supply terminal, and the other end of which is connected to the power supply terminal of the tenth transistor; and ninth resistors respectively connected to the collectors.

a tenth resistor having one end connected to the base of the tenth transistor and the other end connected to the reference terminal;
an eleventh transistor of a first conductivity type, whose emitter is connected to the collector of the transistor No. 0, the emitter is connected to the power supply terminal, and the collector is connected to the stabilized voltage output terminal; one end is connected to the collector of the transistor No. 0; Eleventh transistors each having the other end connected to the base of the sixth transistor.
and a twelfth resistor, one end of which is connected to the other end of the eleventh resistor, and the other end of which is connected to the reference terminal.

[Effect]

Therefore, when the power supply voltage applied to the power supply terminal becomes equal to or higher than the reference voltage, the fifth transistor to which the reference voltage is applied by the reference voltage generation section becomes active.
The activated fifth transistor causes the first. The second transistor is driven, and the 9th transistor is driven by the first transistor. Since the tenth and eleventh transistors are sequentially driven, the output voltage rises even when the supply voltage is as low as the reference voltage.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the power supply circuit of the present invention, and FIG. 2 is a characteristic diagram showing the operation of the embodiment of FIG.

One end of the resistor R1*R2+R3*R4+R8+R9 is connected to the power supply terminal l. The emitters of PNP transistors Q+ and Q2 are connected to resistors R1 and R1, respectively.
Connected to the other end of R2, PNP) transistor Q
The base of transistor Q2 (PNP) is connected to the base and collector of transistor Q2. PNP) transistor Q3. Q4
The emitters of each are connected to the other ends of the resistors R3+R4, and the base of the PNP transistor Q4 is PNP)
It is connected to the base and collector of transistor Q3.

The collectors of NPN) transistors Qs and Q6 are connected to the collectors of PNP) transistors Q2 and Q3, respectively. The resistor R5 connects the emitter of the NPN transistor (1, Q6) to the ground via the reference terminal.
When the voltage exceeds f, the reference voltage Vref is applied to the base of the NPN transistor Q5. NPN transistor Q7
The collector is the collector of PNP transistor Q4,
The emitters are each connected to the reference terminal 3 via a resistor R6. NPN) transistor QB has a collector of P
NP The collector of transistor Q1 has an NPN base.
) The base and collector of transistor Q7 and the emitter are respectively connected to reference terminal 3 via resistor R7. The NPN transistor Q9 has its base connected to the collector of the NPII transistor Q8, and its collector connected to the other end of the resistor R8.
The emitter is connected to the reference terminal 3 via a resistor R1°.

The NPN transistor Qto has a base connected to the emitter of the NPN transistor Q9, and a collector connected to the other end of the resistor R9.
The emitters are each connected to a reference terminal 3. P.N.
The emitter of the P transistor Qtt is connected to the power supply terminal l, the base is connected to the collector of the NPN transistor Q+o,
A collector is connected to the stabilized voltage output terminal 2, respectively. A resistor R11 connects the collector of the PNP transistor Qu and the base of the NPN transistor Q6. A resistor R12 (NPN) connects the base of the transistor Q6 and the reference terminal 3. Load resistance RL is stabilized voltage output terminal 2
and the reference terminal 3.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIG. 2.

Supply power supply voltage Vcc is equal to reference voltage Vref (= 2 Va
When t) is reached, a reference voltage is applied to the base of the NPN) transistor Q5, and the NPN) transistor Q5 becomes active, causing current to flow through the PNP) transistor Q2, and therefore current also flows through the PNP) transistor QI.

A bias current is supplied to the base of the NPN) transistor Q9 from the PNP) transistor Q1, and the bias current is supplied to the base of the NPN) transistor Q9.
Io+Q11 also becomes active and the output voltage vO rises. As the supply voltage Vcc increases to the voltage Va, V(l), the output voltage Vo also increases in proportion to the voltage.When the supply voltage Vcc exceeds the voltage VjN, the voltage is increased by the resistors RRI, R, 2, as in the conventional example. Since the divided voltage is fed back to the base of the NPN transistor Q, the output voltage is V.

maintains a stable output voltage Vs7 shown by equation (6).

Vo =Vref X (1+RR'/R12) =V
s 7・------(6) Therefore, even if the supply power voltage Vcc gradually decreases and becomes less than the voltage V3N, the output voltage ■
0 does not become 0, and the supply power supply voltage Vcc becomes the voltage V ref
The voltage Vo continues to be output until the voltage Vo is reached.

〔Effect of the invention〕

As explained above, the present invention drives the first and second transistors by the fifth transistor that becomes active with the reference voltage of the reference voltage generating section when the supply voltage becomes equal to or higher than the reference voltage, and the driven first transistor The ninth transistor
．． 10th. By driving the 11th transistor, there is an effect that the output voltage is output even when the supply voltage is low like the reference voltage, and unlike the conventional example, a level shift circuit is not used, so It also has the effect of not deteriorating the voltage reduction characteristics due to changes.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the power supply circuit of the present invention, Fig. 2 is a characteristic diagram showing the operation of the embodiment of Fig. 7jS1, Fig. 3 is a circuit diagram showing a conventional example, and Fig. 4 is a circuit diagram showing the operation of the embodiment of Fig. 7jS1. FIG. 4 is a characteristic diagram showing the operation of the conventional example shown in FIG. 3; 1...Power supply voltage supply terminal, 2...Stabilized voltage output terminal, 3...Reference terminal, 4...Reference voltage generation section, Ql, Q2 ．． ~． QR'...Transistor, R
,, R2, ~, RI2...Resistance. Patent applicant: NEC IG Microcomputer System Co., Ltd. Agent: Susumu Uchihara, patent attorney Figure 1, page 2

Claims (1)

[Claims] 1. First and second resistors each having one end connected to a power supply terminal, and a first transistor of a first conductivity type having an emitter connected to the other end of the first resistor. and a first transistor whose emitter is connected to the other end of the second resistor and whose base and collector are connected to the base of the first transistor.
a second transistor of a conductivity type; third and fourth resistors each having one end connected to a power supply terminal; and a third transistor of a first conductivity type having an emitter connected to the other end of the third resistor. a transistor whose emitter is connected to the other end of the fourth resistor and whose base is connected to the other end of the third resistor.
The first transistor connected to the base and collector of the transistor
a fourth transistor of a second conductivity type, the collector of which is connected to the collector of the second transistor; and a fifth transistor of a second conductivity type, the collector of which is connected to the collector of the third transistor. a sixth transistor;
A fifth resistor has one end connected to the emitters of the fifth and sixth transistors and the other end connected to the reference terminal, and when a voltage higher than the reference voltage is applied to the power supply terminal, the base of the fifth transistor a seventh transistor of a second conductivity type whose collector is connected to the collector of the fourth transistor; one end of which is connected to the emitter of the seventh transistor and the other end of which is connected to the reference voltage; a sixth resistor respectively connected to the terminals; and an eighth transistor of a second conductivity type, the collector of which is connected to the collector of the first transistor, and the base of which is connected to the base and collector of the seventh transistor. , a seventh resistor whose one end is connected to the emitter of the eighth transistor and the other end to the reference terminal, and a ninth transistor of a second conductivity type whose base is connected to the collector of the eighth transistor. , one end of which is connected to the power supply terminal, and the other end of which is connected to the collector of the ninth transistor.
a tenth transistor of a second conductivity type, the base of which is connected to the emitter of the ninth transistor, the emitter of which is connected to the reference terminal, one end of which is connected to the power supply terminal, and the other end of which is connected to the power supply terminal of the tenth transistor; a ninth resistor connected to the collectors, a tenth resistor whose one end is connected to the base of the tenth transistor, and whose other end is connected to the reference terminal;
an eleventh transistor of a first conductivity type whose emitter is connected to the power supply terminal and whose collector is connected to the stabilized voltage output terminal; one end is connected to the collector of the eleventh transistor, and the other end is connected to the collector of the transistor No. 0; is the 6th
A power supply circuit comprising: an eleventh resistor connected to the bases of the transistors; and a twelfth resistor, one end of which is connected to the other end of the eleventh resistor, and the other end of which is connected to a reference terminal.