JPH0256010A - Constant-voltage reference power source circuit - Google Patents

Abstract

PURPOSE:To obtain a zero temperature coefficient by executing a control so that an output voltage becomes lower than a voltage corresponding to a band gap of a P-N junction element by an output of a differential amplifying circuit by which a voltage across a first resistance, etc., become an input voltage. CONSTITUTION:The constant-voltage reference power source circuit is constitut ed of a differential amplifying circuit 16, a constant-current power source C.C, and also, a first resistance R4, a second resistance R5, a third resistance R1 and a fourth resistance R2, and a transistor (Tr) Q1 as a P-N junction element. In this state, a voltage of a junction part of the P-N junction element Q1 becomes a function of a voltage Vg0 corresponding to a temperature T and a band gap of its semiconductor, and also, a voltage difference of base - emitter voltages of two Trs Q2 - Q3 of the differential amplifying circuit 16 is also shown in the same way, and becomes a function of the temperature T. Accord ingly, this output circuit is shown as a potential difference of the base - emitter voltages of the TRs Q2 - Q3 and becomes a function of the temperature and the voltage Vg0, therefore, the resistances R1 - R4 are selected so that an expres sion which is brought to partial differential by the temperature T becomes zero.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a low voltage reference power supply circuit, and more particularly to a low voltage reference power supply circuit having a zero temperature coefficient and capable of suppressing fluctuations in output voltage due to temperature changes.

Prior Art The present applicant proposed a low voltage reference power supply circuit in Japanese Patent Publication No. 55-18928 (the principle circuit diagram thereof is shown in FIG. 5). In the figure, reference numeral 1 denotes a differential amplifier circuit composed of transistors having mutually different current densities, the output of which is amplified by an amplifier 2 and connected to an output terminal T3.

Also, the voltage across the resistor RI2 is equal to the voltage across the differential amplifier circuit 1.
are supplied to the two inputs of .

In the circuit shown in FIG.
ref can have a temperature characteristic having a zero temperature coefficient, and Vref can be kept stable even when the temperature fluctuates.

In addition, in Japanese Patent Application No. 63-20895 (title of the invention "Low Voltage Reference Power Supply Circuit"), the present applicant has disclosed that by providing a level conversion means, the temperature coefficient can be reduced to zero even at a low voltage of 1.2■ or less. We proposed a low voltage reference power supply circuit with

Problems to be Solved by the Invention Although the output voltage Vret of the circuit shown in FIG. 5 is stable against temperature fluctuations and serves as a convenient constant voltage power supply, vref is approximately 1.0 mm, which corresponds to the energy band gap of silicon.
Must be set to 2v. Therefore, the circuit shown in Fig. 5 cannot be used as it is for various devices that operate at low voltages of 1 to 2 V or less, which have been increasing in recent years. Therefore, it is necessary to take measures such as connecting vref to a non-inverting input terminal of an operational amplifier configured as a voltage follower type via a resistor.

However, if the original reference voltage Vrer is not a bandgap voltage, it will not operate stably, so Vref itself cannot be used at a voltage of 1.2 V or less.

In addition, the circuit proposed in Japanese Patent Application No. 63-20895 is 1
．． There is a problem in that in order to obtain a low voltage of 2V or less, a level conversion means must be provided at the output stage.

The present invention has been made in view of the above points, and is based on a voltage corresponding to the energy band gap of silicon (approximately 1
．． An object of the present invention is to provide a low voltage reference power supply circuit that can obtain an output voltage of 2 V) or lower and has a zero temperature coefficient.

Means for Solving the Problems A low voltage reference power supply circuit according to the present invention includes a differential amplifier circuit,
This differential amplification circuit is biased and the voltage across the first resistor is used as the input voltage of the differential amplifier circuit. a first series circuit, a second series circuit including a third resistor and a PN junction element connected in series, and connected in parallel to the first series circuit; Second
A fourth resistor is provided to connect the point between the resistors in the second series circuit and the connection point between the P side of the PN junction element and the third resistor in the second series circuit, and the output of the differential amplifier circuit. The output voltage generated between the output terminals is controlled to be a constant voltage below the voltage corresponding to the bandgap of the semiconductor forming the PN junction element.

The voltage at the junction of a working PN junction device is expressed by the well-known formula: temperature T and voltage V, which corresponds to the bandgap of the semiconductor (usually silicon) constituting the PN junction device. It is a function of Further, the voltage difference between the base-emitter voltages of two transistors constituting the differential amplifier circuit is also expressed by a well-known formula, and is a function of temperature T.

The output voltage of the low voltage reference power supply circuit is expressed as a voltage difference between the voltage at the junction of the PN junction element and the base-emitter voltage of two transistors constituting the differential amplifier circuit. Therefore, the output voltage expressed in this way is T and g
By selecting the values of the resistors constituting the first and second series circuits so that the partial differentiation of this equation with respect to temperature T becomes zero, the output voltage becomes vg. or less and can be set to have a zero temperature coefficient.

Embodiment FIG. 1 shows a circuit diagram of the principle of the present invention. In Figure 1, A
11) is the differential amplifier circuit 16 shown in FIG. 2 and thereafter, and specifically has the configuration shown in FIG. The first embodiment shown in FIG. 2 will be described below. Resistance R in Figure 2
4 corresponds to the first resistor described in the claims, the resistor Rs similarly corresponds to the second resistor, the resistor R+ corresponds to the third resistor, the resistor R2 corresponds to the fourth resistor, and the transistor Q1 is a PN junction element. handle. Also, C9C is a constant current power supply and the output terminal v
Supply a constant current to the out line.

The current flowing through resistor R2 is 12, and the current flowing through resistor R3? IH
If FE is I3, the base-emitter voltage VBEI of transistor QI is: VBEI-R2Iz+Rs(12+Ia) (1)
The base-emitter voltages of transistors Q2 and Ql are VBE2 and VBE3, respectively, and the resistor R is
When the voltage across both ends of 4 is ΔVBE, ΔV BL-V
BF2-V B[3(2), and the current ■3 is expressed as [1=AVBE/R4(3), and from equations (1) and (3), the current! 2 is VBEl −
-AVBE 12” (4)R
It is expressed as 2+R5.

From equations (3), (4), and (6), it becomes Rs (VBEl ・ΔVBE) + (R3 +R4 +Rs +Rs.Here, if we set R3 + R4+Rs >>R1 +82 so that ■2 〉〉I3, , If the voltage taken out from the output terminal V., t as a reference power supply is vr8r, then ΔVBE + (R3] + R4 Vre (-Rs (I z ” I s ) + (Rs
+R4+R6) I3 (5)-Rslz
+ (Rs +R4+R5+Rs) 13 (6)
).

(Here, 1-Rz +-Rs and the voltage between the base and emitter of transistor Q1 is VB
Assuming EI, ■ VBEO() (9)T.

It is known that it can be expressed as Here, vgo is the voltage (approximately 1.2V) corresponding to the energy bandgap of silicon constituting transistor QI, and king is temperature, T
o is the reference operating temperature, and V BEG is the base-emitter voltage of the transistor QI when T=To.

It is also known that the input voltage of the differential amplifier circuit 16 is ΔVBE. Here, 01 is the current density of the transistor Q3 with respect to the transistor Q2 (or the area ratio of the junction part), nz is the current density of the transistor Q4 with respect to the transistor Qs, k is the Boltzmann constant, and q is the electronic charge.

(9) Substituting equation (10) into equation (8) yields T.

+ (1+ R30kr □)□Poor n 4 Q becomes.

Here, formula (11) is pulverized under temperature, and A VBE-V
BE2- VBE3 T ・Lightning fln n+ ・n2 (10) ni 2 +Ks R sword k + (1+ )-fl n n 1 ・
It becomes n24 q. Setting this as zero and finding v and o, we get
This reduces the resistance R2, Rs, Rs, R3) to (13
) shows that if the temperature coefficient of vref is set to satisfy the equation, the temperature coefficient of vref becomes a gap.

Also, the value of Vref at T = To is R kT from equation (11).

It is expressed as (1+~nnl・n2).Equation (15) shows that when the temperature T is T=To, the voltage vref generated between the output terminals 10 and 11 is greater than 1 or 2■, which corresponds to the band gap of silicon. This indicates a low voltage, and since it has a zero temperature coefficient, the output is stable against temperature changes.

Figures 3 and 4 show circuit diagrams of the second and third embodiments of the present invention, respectively, and the same components as those in Box 2 in these circuits are given the same reference numerals. The explanation will be omitted.

The circuit shown in Fig. 2 can provide a stable low voltage output against temperature fluctuations, which is the main purpose of the present invention, but the circuits shown in Figs. Necessary circuits are provided around the circuit shown in Figure 2 in order to prevent fluctuations in the output voltage caused by plays the role of constant current power supply C9C in FIG.

In Figure 3, when the power is turned on to Vio, the constant current circuit 1
5, a substantially constant current is supplied to the transistor Q8, and the transistor Q9 is turned on, thereby operating the low voltage reference power supply circuit 16, and accordingly, the PNP transistor Q1 is turned on. From this state, when the output voltage voUt changes, for example, in an increasing direction due to a load change or the like, the PNP transistor Q+o is turned on more strongly and the emitter current increases, so that the current supplied to the base of the transistor Q8 decreases. As a result, the output voltage ■oIIt supplied from the collector of the transistor Q9 is lowered. On the other hand, the output voltage V. When ut changes in the decreasing direction, contrary to the above, ■. It operates to raise the output voltage■. Try to keep ut constant.

In the circuit shown in FIG. 4, when power is applied to Vio and transistor QI2 is turned on, current flows through current mirror circuit 17, and transistors QI3. When QI3 is turned on, current is supplied from the PNP transistor Q+s to the low voltage reference power supply circuit 16, and circuit operation is started. When the low voltage reference power supply circuit 16 operates to turn on the transistor QI6, the transistor Qn is also turned on, thereby turning off the transistor QI2. Therefore, all the collector current of the transistor QI7 constituting the current mirror circuit 17 is supplied to the collector of the transistor 021. Since this transistor Q21 has the function of keeping its collector current constant, the current mirror circuit 17
The collector current of the transistor Q+g constituting the transistor Q+g also remains constant. Output voltage V. , when t fluctuates, the current of Q10 is controlled by the level of the emitter voltage of Q16 to keep the output voltage constant (if the output increases, the emitter voltage of Q+s increases and Q).4. The current is lowered to reduce the base current of Q+s, and the output voltage is lowered and controlled to be constant).

The circuit of FIG. 4 has higher stability of the corefter current of 021 than the circuit of FIG. 3, so the circuit of FIG. 4 has higher stability than the characteristics of the circuit of FIG.

Effects of the Invention As described above, according to the present invention, a stable low voltage having a zero temperature coefficient below the voltage corresponding to the energy band gap of silicon can be extracted with a relatively simple circuit configuration, and battery-powered electricity can be It can meet the growing demand for low-voltage reference power supplies as the number of products increases, and it also has advantages in terms of reliability and slow flow because it can be easily integrated into circuits. have

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the principle of the present invention, FIG. 2 is a circuit diagram of a first embodiment of the present invention, FIG. 3 is a circuit diagram of a second embodiment of the present invention, and FIG. 4 is a circuit diagram of a second embodiment of the present invention. The circuit diagram of the third embodiment and FIG. 5 are the principle circuit diagrams of the conventional circuits. 15... constant current circuit, 16... constant voltage reference power supply circuit, 17... current mirror circuit, C0C... low current circuit, R+ ~ Rs, Rn, R12=resistance, Q
I-Qs *Q8~QI8. ON...transistor.

Claims (1)

[Scope of Claims] A differential amplifier circuit, a circuit connected in series with the first resistor that biases the differential amplifier circuit and uses a voltage across a first resistor as an input voltage of the differential amplifier circuit. A first series circuit having a second resistor and connected between output terminals, and a third resistor and a PN junction element connected in series, and connected in parallel with the first series circuit. a second series circuit; a point between the first and second resistors in the first series circuit;
a fourth resistor provided to connect the P side of the PN junction element in the second series circuit and the connection point of the third resistor, and A low voltage reference power supply circuit that controls an output voltage generated between output terminals to be a constant voltage that is lower than a voltage corresponding to a bandgap of a semiconductor forming the PN junction element.