JP2002341953A - Band gap reference voltage circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce operating current as quickening rise of reference voltage when power is supplied. SOLUTION: Current to be outputted from a transistor Q16 of a constant current circuit 12 is supplied to a band gap cell circuit 14 as bias current through a current mirror circuit 26 and a constant voltage line 23 from which reference voltage VBG is outputted, folded by the current mirror circuit 26 and becomes bias current of an operational amplifier 15. When the power is supplied, the bias current is supplied to the band gap cell circuit 14 through the current mirror circuit 26 from a point of time before an output transistor Q33 is started to be operated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bandgap reference voltage circuit comprising a bandgap cell circuit and an amplifier circuit.

[0002]

In recent years, with the advancement of electronic control systems for vehicles (for example, automobiles), many electronic control units (hereinafter referred to as ECUs) have been mounted on vehicles. . The ECU is mainly composed of a microcomputer, and has a main power supply for operation and a RAM.
It has a backup power supply for backing up. And as the scale of the system increases,
In addition to the increase in current consumption of the entire ECU when the ignition switch is on, an increase in the operating current (standby current) of the backup power supply and the like when the ignition switch is off is a problem.
This is because an increase in the standby current causes the battery to run down.

The power supply circuit is composed of a band gap reference voltage circuit, an output voltage detection circuit, an error amplifier circuit, a constant current circuit, and the like. It is necessary to reduce the operating current of the circuit.

Therefore, the present inventor has newly developed a bandgap reference voltage circuit shown in FIG. The bandgap reference voltage circuit 1 includes a constant current circuit 2, a constant voltage circuit 3, a bandgap cell circuit 4, an operational amplifier 5, and a current return circuit 6, and an input transistor Q1 of a differential amplifier circuit 7 of the operational amplifier 5. And Q2 and Q3
And Q4 each have a cascade connection circuit form.

According to this configuration, the input impedance of the operational amplifier 5 is increased, so that the bandgap cell under the condition that the input bias current of the differential amplifier circuit 7 is sufficiently smaller than the base currents of the transistors Q5 and Q6. By increasing the resistance values of the resistors R1, R2 and R3 of the circuit 4, the bias current flowing through the transistors Q5 and Q6 can be reduced. As a result, even when the input bias current of the operational amplifier 5 varies due to the manufacturing process, the influence of the variation on the bias state of the bandgap cell circuit 4 is reduced, and the temperature coefficient of the reference voltage VBG is reduced to the design value. As described above, it is possible to reduce the operating current of the bandgap reference voltage circuit 1 while keeping it substantially zero.

However, in the bandgap reference voltage circuit 1, in order to speed up the rise of the reference voltage VBG at the time of power-on, the constant current generated by the constant current circuit 2 is turned back by the current turning circuit 6 and the bias current of the operational amplifier 5 is turned on. The configuration is as follows. For this reason, in the current mirror circuit 8 of the current folding circuit 6, a current twice as much as the constant current flowing out of the constant current circuit 2 is wasted on the power supply line 9, which is an obstacle to further reducing the operating current. Had become.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a bandgap reference voltage circuit capable of reducing the operating current while speeding up the rise of the reference voltage at power-on. .

[0008]

According to the first aspect of the present invention, the current output from the constant current generating circuit is a current mirror connected between the constant current generating circuit and the reference voltage output line. The signal is directly supplied to the band gap cell circuit through the circuit, and is turned back by the current mirror circuit to become a bias current of the amplifier circuit. According to this means,
When the power supply voltage is turned on, the bias current is easily supplied to the bandgap cell circuit more quickly than when the amplifier circuit receives the folded bias current and starts operating, so that the rise of the reference voltage can be accelerated. .

Further, a constant current passing through the current mirror circuit, which has been wasted in the past, is supplied as a part of the bias current to the bandgap cell circuit via the reference voltage output line. , The current supplied to the bandgap cell circuit via the reference voltage output line is reduced, and the operating current (current consumption) of the entire bandgap reference voltage circuit can be reduced.

According to the second aspect of the present invention, a part of the bias current required in the bandgap cell circuit under the bias condition in which the first and second reference voltages are equal to each other is partially a current mirror. The voltage is supplied through the circuit, and the remainder is supplied from the output line of the constant voltage circuit via the output transistor of the amplifier circuit. That is, a part of the required bias current is easily supplied to the bandgap cell circuit before the output transistor of the amplifier circuit starts operating, and the rise of the reference voltage can be accelerated as described above.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an electrical configuration of a bandgap reference voltage circuit manufactured by a bipolar process as a monolithic IC. This IC is used, for example, in an electronic control unit (ECU) mounted on an automobile, and is not shown in FIG.
A digital circuit such as a PU and a memory, various analog circuits, a power supply circuit, and the like are integrated into one chip.

The bandgap reference voltage circuit 11 comprises a constant current circuit 12, a constant voltage circuit 13, a bandgap cell circuit 14, an operational amplifier 15, and a current return circuit 16. The power supply voltage Vcc is supplied from terminals 17 and 18 of the IC.
(For example, the battery voltage VB) and input the terminal 1 of the IC.
For example, a bandgap reference voltage VBG (hereinafter, simply referred to as a reference voltage VBG) of 1.22 V is output from the switches 9 and 18. The reference voltage VBG has a very small temperature fluctuation and is supplied not only to the outside of the IC but also to a power supply circuit and an analog circuit inside the IC.

A constant current circuit 12 (corresponding to a constant current generating circuit)
Is connected between a power supply line 20 inside the IC connected to the terminal 17 and a power supply line 21 inside the IC connected to the terminal 18, and includes transistors Q11 to Q16 and resistors R11 to R11.
R13 and a self-bias type constant current circuit. That is, a constant current determined based on the base-emitter voltage VBE and the resistance value of the resistor R12 flows through the resistor R12 connected between the base and the emitter of the transistor Q11.
It is supplied to the transistor Q11 as a collector current of the NP-type transistor Q14. The transistor Q1
4 and PNP transistors Q15 and Q16 form a current mirror circuit in which each emitter is connected to the power supply line 20 and each base is connected in common. The transistors Q15 and Q16 have the above constant current. It is flowing.

The constant voltage circuit 13 has a circuit configuration in which seven diodes D11 to D17 are connected in series between the power supply lines 20 and 21 via the emitter and the collector of the transistor Q15. The base of an NPN transistor Q17 for output is connected to the anode of the diode D11. The collector and the emitter of the transistor Q17 are connected to the power supply line 20 and the constant voltage line 22, respectively. Here, the forward voltage of the diodes D11 to D17 is VF, and the saturation voltage of the transistor Q15 is VCE (s
at), the power supply voltage Vcc is (7 · VF + VCE (sat)
), The constant voltage operation is started, and the voltage of the constant voltage line 22 becomes a constant voltage of 6 · VF. Operational amplifier 1
5 operates with this constant voltage as the power supply voltage, so that it is less affected by fluctuations in the power supply voltage Vcc, and stable operation is possible.

The bandgap cell circuit 14 includes a resistor R1
NPN transistor Q1 diode-connected to
8 and a resistor R
15 and a series circuit of a collector and an emitter of an NPN transistor Q19 and a resistor R16 are connected between a constant voltage line 23 (corresponding to a reference voltage output line) and a power supply line 21. The bases of the transistors Q18 and Q19 are connected to each other, and the base potential and the collector potential of the transistor Q19 become the first reference voltage and the second reference voltage, respectively, in the present invention. The constant voltage line 23 is connected to the terminal 19 via the resistor R17.

The operational amplifier 15 (corresponding to an amplifier circuit) includes a differential amplifier circuit 24 as an input stage and an output circuit 2 as an output stage.
And 5. The input transistors of the differential amplifier circuit 24 are composed of cascade-connected PNP transistors Q20, Q21 and Q22, Q23. The bases of the transistors Q18, Q19 and the collector of the transistor Q19 are connected to a resistor R18 and a resistor R18, respectively. The transistor Q2 via R19
0 and connected to the base of Q22.

The collectors of the transistors Q21 and Q23 are respectively connected to the power supply line 21 via the transistor Q24 and the resistor R20, and the transistor Q25 and the resistor R21, and the emitters are connected in common and driven at a constant current. It is connected to constant voltage line 22 via Q26 and resistor R22. The collector of the transistor Q20 is connected to the power supply line 21, and the common connection point between the emitter and the base of the transistor Q21 is connected to the constant voltage line 22 via a transistor Q27 driven by a constant current and a resistor R23. . Similarly, the collector of the transistor Q22 is connected to the power supply line 21, and the common connection point between its emitter and the base of the transistor Q23 is connected to the constant voltage line 22 via a transistor Q28 driven by a constant current and a resistor R24. I have.

The base and the emitter of the transistor Q29 are connected between the collector and the base of the transistor Q25, and the collector of the transistor Q29 is connected to the constant voltage line 22 via the resistor R25. The transistor Q29 supplies a base current to the transistors Q24 and Q25, and sets the collector potential of the transistor Q25 to 2 · VBE similarly to the collector potential of the transistor Q24.
It is provided for fixing to.

The output circuit 25 has a circuit configuration in which a transistor Q32 driven by a constant current, a diode D18 and transistors Q30 and Q31 connected in Darlington are connected in series between a constant voltage line 22 and a power supply line 21. ing. The base of the transistor Q30 is
24 (Q21) connected to the transistor Q
The emitter of 30 is connected to the power supply line 21 via the resistor R26. Further, NP is provided between the constant voltage lines 22 and 23.
The collector and the emitter of the N-type output transistor Q33 are connected, and the base of the transistor Q33 is connected to the cathode of the diode D18 and the transistor Q30 (Q
31) is connected to a common connection point with the collector. Note that this common connection point and the transistor Q24 (Q2
Between the collector of 1), a capacitor C for phase compensation
11 are connected.

The current folding circuit 16 includes an NPN-type transistor Q34 connected between the transistor Q16 of the constant current circuit 12 and the constant voltage line 23;
34, a transistor Q35 forming a current mirror circuit 26, and a PNP transistor Q connected between the constant voltage line 22 and the collector of the transistor Q35.
36. The transistor Q2 described above
The bases of Q6, Q27, Q28, Q32 and Q36 are commonly connected, and the constant current flowing through the transistor Q16 is turned back by the current mirror circuit 26 and flows through the transistors Q36 and Q32. A substantially constant current, which is reduced in accordance with the resistance values of the resistors R22, R23, and R24 with respect to the constant current, flows through the transistors Q26, Q27, and Q28, respectively.

Next, the operation of the bandgap reference voltage circuit 11 will be described with reference to FIGS.
First, in a normal operation in which a sufficient power supply voltage Vcc (for example, 3.5 V or more) is applied between the terminals 17 and 18, the operational amplifier 15 connects the base potentials of the transistors Q18 and Q19 in the bandgap cell circuit 14 to the base potential of the transistor Q19. A collector potential is input, and the voltage of the constant voltage line 23 (reference voltage VBG) is controlled so that both potentials match.
At this time, the current mirror circuit 26 and the operational amplifier 15
, A bias current is supplied to the band gap cell circuit 14 through the constant voltage line 23. Hereinafter, this bias current will be described.

If the resistance value of the resistor R12 is represented by the same R12 as the sign, and the base-emitter voltage of the transistor Q11 is represented by VBE (Q11), the following equation (1) is applied to the transistor Q14 constituting the constant current circuit 12. A constant current with a current value of Ia flows. Then, a current equal to Ia flows from the transistor Q16 into the transistor Q34 on the input side of the current mirror circuit 26. Ia = VBE (Q11) / R12 (1)

This current is turned back by the current mirror circuit 26, and a current equal to Ia is supplied from the transistor Q36 to the transistor Q3 on the output side of the current mirror circuit 26.
Flow into 5. These transistors Q34 and Q35
Is supplied to the bandgap cell circuit 14 through the constant voltage line 23.

When a current of Ia flows through transistor Q36, transistors Q26, Q27, Q28, Q3
2, a predetermined bias current according to Ia flows, and the operational amplifier 15 operates. The operational amplifier 15 supplies a current obtained by subtracting the above (2 · Ia) from the bias current necessary for the bandgap cell circuit 14 through the output transistor Q33.

FIG. 2 is a simulation result (temperature 27 ° C.) showing the current consumption of the bandgap reference voltage circuits 1 and 11 with respect to the power supply voltage Vcc. In FIG. 2, the horizontal axis and the vertical axis indicate the power supply voltage Vcc [V] and the current consumption [μA], respectively. The plots indicated by △ indicate the bandgap reference voltage circuit 11 of the present embodiment, and the marks indicated by ○ The plot shows the bandgap reference voltage circuit 1 having a conventional configuration. In a steady state where a power supply voltage Vcc of about 3.5 V or more is applied, the bandgap reference voltage circuit 11
Has a current consumption reduced by 7 μA as compared with the bandgap reference voltage circuit 1 having the conventional configuration. This is because, in the present embodiment, Ia is set to 3.5 μA,
This is because the (2 · Ia) current passing through the current mirror circuit 26 is effectively used as a part of the bias current of the bandgap cell circuit 14.

In this steady state, the transistor Q1
8 and Q19 are driven at different current densities, and the difference voltage between the base-emitter voltages of the transistors Q18 and Q19 is applied to the resistor R16. If the emitter areas of the transistors Q18 and Q19 are equal, the resistance R
If the resistance values of R14, R15, and R16 are represented by the same symbols as R14, R15, and R16, respectively, and the base-emitter voltage of the transistor Q18 is represented by VBE (Q18), it is generated on the constant voltage line 23 (terminal 19). The reference voltage VBG is given by the following equation (2). VBG = VBE (Q18) + (R15 / R16) .VT.ln (R15 / R14) (2) where VT = kT / q

That is, the reference voltage VBG is a weighted addition of the first term having a negative temperature coefficient and the second term having a positive temperature coefficient, and the resistance value R14, R15 and R16 are determined. Also, in order to correct the deviation of the reference voltage VBG due to the variation in characteristics and obtain a more accurate reference voltage VBG, laser trimming is performed on the resistor R15 made of, for example, chromium / silicon in the wafer inspection process, and the reference voltage VBG is adjusted. Adjustment to a design value (for example, 1.22 V) is performed.

Next, the rise characteristics of the reference voltage VBG when the power supply voltage Vcc is applied will be described. Band gap cell circuit 14 through current mirror circuit 26
The power supply voltage Vcc1 at which the bias current can be supplied is calculated as in the following equation (3). Vcc1 = VBG + VBE (Q34) + VCE (Q16) (3)

The power supply voltage Vcc2 at which the operational amplifier 15 starts operating is calculated to be about 3 V as shown in the following equation (4). Vcc2 = VBE (Q18) + VBE (Q20) + VBE (Q21) + VCE (Q26) + VBE (Q17) + VCE (Q15) (4)

Output transistor Q33 of operational amplifier 15
The power supply voltage Vcc3 at which the circuit becomes operable is calculated as in the following equation (5). Vcc3 = VBG + VBE (Q33) + VF (D18) + VCE (Q32) + VBE (Q17) + VCE (Q15) (5)

FIG. 3 is a simulation result showing the relationship between the applied power supply voltage Vcc and the output reference voltage VBG. (A) shows the bandgap reference voltage circuit 11 of the present embodiment, and (b) shows the bandgap reference voltage circuit 1 of a conventional configuration. 3 (a) and 3 (b), the horizontal axis and the vertical axis indicate the power supply voltage Vcc [V] and the reference voltage VBG [V], respectively. IC temperature is 120 ° C, 27 ° C, -40
The case of ° C is shown.

Comparing FIGS. 3A and 3B, the power supply voltage Vcc required to obtain a constant reference voltage VBG at all temperatures is equal to the power supply voltage Vcc of the bandgap reference voltage circuits 11 and 1. There is no difference between them, and it is almost 3.5V. However, when the battery is connected between the terminals 17 and 18 and the power supply voltage Vcc rises from 0 V,
The rise of the reference voltage VBG is faster in the bandgap reference voltage circuit 11 of the present embodiment. This is considered as follows.

That is, in the case of the bandgap reference voltage circuit 1 having the conventional configuration, the bias current is supplied to the bandgap cell circuit 14 only when the power supply voltage Vcc rises to the voltage Vcc3. On the other hand, in the case of the bandgap reference voltage circuit 11 of the present embodiment,
As is clear from the above equations (3) and (5), when the power supply voltage Vcc rises, the bias current is supplied from the current mirror circuit 26 to the bandgap cell circuit 14 when the power supply voltage Vcc1 first rises. , After which the output transistor Q33 rises to the voltage Vcc3.
Turns on, and a bias current is supplied from the operational amplifier 15 to the bandgap cell circuit 14. That is,
The bandgap reference voltage circuit 11 uses the power supply voltage Vcc
Is lower, the bias current is supplied to the bandgap cell circuit 14, so that the rise of the reference voltage VBG is faster.

As described above, according to the present embodiment, the current output from the constant current circuit 12 is applied to the band through the current mirror circuit 26 connected between the constant current circuit 12 and the constant voltage line 23. The bias current is supplied to the gap cell circuit 14 and turned back by the current mirror circuit 26 to become a bias current of the operational amplifier 15. Therefore, when the power supply voltage is turned on, the bias current is supplied to the bandgap cell circuit 14 earlier than when the operational amplifier 15 starts to operate by receiving the supply of the folded bias current, so that the rise of the reference voltage VBG is accelerated. be able to.

The constant current passing through the current mirror circuit 26, which was conventionally discarded, is changed to a constant voltage line 23.
Is supplied to the bandgap cell circuit 14 as a part of the bias current through the operational amplifier 15.
From the band gap cell circuit 14 via the constant voltage line 23
, The operating current (current consumption) of the entire bandgap reference voltage circuit 11 can be reduced. Therefore, if this bandgap reference voltage circuit 11 is applied to, for example, a backup power supply circuit of a RAM, a power supply circuit with a small standby current can be configured.

The present invention is not limited to the embodiment described above and shown in the drawings. For example, the present invention can be modified or expanded as follows. Band gap cell circuit 1
4 is not limited to the one shown in FIG. For example, a first series circuit composed of a first transistor and a diode-connected first transistor, and a second and a third resistor diode-connected between a constant voltage line 22 and a power supply line 21. A second series circuit composed of a second transistor is connected in parallel, a collector of the first transistor is connected to a resistor R18, and a common connection point of the second resistor and the third resistor is connected to a resistor R19. May be connected.

As for the input transistors of the operational amplifier 15, cascaded transistors Q20 to Q23
Alternatively, a MOS transistor may be used. A bias current canceling circuit for transistors Q20 and Q22 may be provided between resistor R18 and transistor Q20 and between resistor R19 and transistor Q22, respectively. As a result, even if the characteristics vary in the manufacturing process, the influence of the variations in the input bias current of the differential amplifier circuit 24 on the bias state of the bandgap cell circuit 14 is reduced, and the reference voltage VBG substantially matches the design value. Obtainable.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram of a bandgap reference voltage circuit showing one embodiment of the present invention.

FIG. 2 shows a power supply voltage Vcc obtained by simulation.
Graph showing the relationship between the power consumption of the bandgap reference voltage circuit

FIG. 3 shows a power supply voltage Vcc obtained by simulation.
Showing the relationship between the reference voltage and the reference voltage VBG

FIG. 4 is an electrical configuration diagram of a bandgap reference voltage circuit developed by the present inventors.

[Explanation of symbols]

11 is a band gap reference voltage circuit, 12 is a constant current circuit (constant current generation circuit), 13 is a constant voltage circuit, 14 is a band gap cell circuit, 15 is an operational amplifier (amplifier circuit), 2
3 is a constant voltage line (reference voltage output line), 26 is a current mirror circuit, Q18 and Q19 are transistors, and Q33 is an output transistor.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H420 NA23 NB02 NB16 NC02 NC03 NC12 NC23 NC34 NE04 5J066 AA01 AA47 AA58 CA36 CA65 FA10 HA08 HA19 HA25 HA29 KA06 KA11 KA12 MA21 SA07 TA02 5J092 AA01 AA58 CA36 CA65 FA10 HA08 HA19 HA06 KA09 KA11 KA12 MA11 MA21 SA07 TA02

Claims (2)

[Claims] 1. At least two transistors,
Under the bias condition in which the first and second reference voltages output according to the operation states of these two transistors are equal to each other, the two transistors are driven at different current densities and the band is shifted from the reference voltage output line. A bandgap cell circuit for outputting a gap reference voltage; a differential amplifier for receiving and inputting the first reference voltage and the second reference voltage; and outputting the output voltage via the reference voltage output line to the bandgap. An amplifier circuit that feeds back to the cell circuit; a constant current generating circuit; a constant current generating circuit, which is connected between the constant current generating circuit and the reference voltage output line, folds a current output from the constant current generating circuit, A bandgap reference voltage circuit, comprising: a current mirror circuit for setting a bias current. 2. The circuit according to claim 1, further comprising a constant voltage circuit, wherein the amplifier circuit includes an output transistor connected between an output line of the constant voltage circuit and the reference voltage output line. The described bandgap reference voltage circuit.