Reference voltage generation circuit

Abstract

To provide a reference voltage generating circuit capable of adjusting voltage in an easily implementable configuration.SOLUTION: A reference voltage generating circuit 1 is provided with a Zener diode 3 connected between a current source 2 and a ground, and a current generating circuit 5 connected in parallel with the Zener diode 3. The current generating circuit 5 includes: a resistance voltage dividing circuit which has a branching unit for branching current into two paths, and outputs voltage divided by resistance elements R1 through R3; a transistor circuit; and a voltage control circuit. The transistor circuit has two NPN transistors BJT1 and BJT2, collectors of which are connected to the respective two paths, and bases of which are commonly connected, and a series resistance circuit which is connected between an emitter of the transistor BJT1 and the ground and in which resistance elements R4 and R5 are connected in series, where an emitter of the transistor BJT2 is connected to a common connection point of the resistance elements R4 and R5. An operational amplifier 4 controls the transistors BJT1 and BJT2 so that the respective collector potentials thereof are equal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a circuit for generating a reference voltage. [Background technology]

[0002] Various configurations have been proposed for circuits that generate reference voltages, including the following example: A current mirror circuit generates an Iptat (proportional to absolute temperature) current that has a positive temperature characteristic proportional to absolute temperature and depends on the junction voltage of a bipolar transistor, and the voltage generated based on this current is subtracted from the voltage generated by the Zener diode. As a result, the positive temperature dependency of the voltage generated by the Zener diode is corrected, resulting in an output voltage that is independent of temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent No. 20200218302 [Patent Document 2] U.S. Patent No. 10,955,868 [Patent Document 3] US Patent No. 20210124386 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a circuit with the above configuration, errors are likely to occur in the current Iptat. That is, the ratio between the current Iptat generated by the MOS current mirror and the current that is the source of the mirror is likely to vary, resulting in errors in the current Iptat determined by that ratio. Furthermore, in transistors with a small grounded emitter gain, a large through-current from the base occurs, and errors corresponding to this through-current also occur in the current Iptat.

[0005] Furthermore, adjusting the current Iptat would be difficult because it would require a trimming mechanism. For example, in the circuit configuration described above, if the resistor in the circuit that generates the current Iptat were to be trimmed using a MOS switch, the resistor and the MOS switch would be connected in series. Therefore, because current flows through the MOS switch, the current is affected by the resistance of the MOS switch. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a reference voltage generating circuit that can adjust a voltage with an easily implemented configuration. [Means for solving the problem]

[0006] According to claim 1, the reference voltage generating circuit includes a Zener diode connected between a current source and ground, and a current generating circuit connected in parallel to the Zener diode for generating a current having a positive temperature dependency proportional to absolute temperature. The current generating circuit includes a branching section for branching the current into two paths, a resistive voltage dividing circuit for dividing the current into two paths and outputting a voltage divided by a resistive element as a reference voltage, a transistor circuit, and a voltage control circuit.

[0007] The transistor circuit includes two NPN transistors whose collectors are connected to the two paths and whose bases are connected in common, and a series resistor circuit in which multiple resistor elements are connected in series, connected between the emitter of one of the two NPN transistors and ground, with the other emitter connected to the common connection point of the multiple resistor elements. The voltage control circuit controls the collector potentials of the two NPN transistors so that they are equal.

[0008] With this configuration, the current Iptat, which has the above-mentioned positive temperature dependency, is a current that depends on the voltage difference ΔVBE between the bases and emitters of the two NPN transistors, and the collector current that flows through the transistor pair can be controlled with high precision by the resistive voltage divider circuit and voltage control circuit. The current Iptat can be adjusted by changing the resistance ratio of the two paths in the resistive voltage divider circuit. Because the voltage divided by the resistive voltage divider circuit is used as the reference voltage, there is no influence of errors from the current mirror circuit, and the temperature dependency of the reference voltage can be corrected with high precision. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a circuit diagram showing a reference voltage generating circuit in a first embodiment; [Figure 2] FIG. 10 is a circuit diagram showing a reference voltage generating circuit in a second embodiment. [Figure 3] FIG. 10 is a circuit diagram showing a reference voltage generating circuit in a third embodiment. [Figure 4] FIG. 1 shows the configuration of a potential adjustment circuit. [Figure 5] FIG. 10 is a circuit diagram showing a reference voltage generating circuit in the fourth embodiment. [Figure 6] FIG. 10 is a circuit diagram showing a reference voltage generating circuit in a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) As shown in FIG. 1, in the reference voltage generating circuit 1 of this embodiment, a power supply V cc A series circuit of a current source 2 and a Zener diode 3 is connected between the resistor R1 and ground. One end of a resistor R1 is connected to the cathode of the Zener diode 3, and one end of resistors R2 and R3 is connected to the other end of the resistor R1. The common connection point between the resistor R1 and the resistors R2 and R3 corresponds to a branch. The bases of bipolar transistors BJT1 and 2 are connected in common, and the collectors of BJT1 and 2 are connected to the other ends of the resistors R2 and R3, respectively.

[0011] A series circuit of resistors R4 and R5 is connected between the emitter of BJT1 and ground, and their common connection point is connected to the emitter of BJT2. The collectors of BJT1 and BJT2 are connected to the inverting and non-inverting input terminals, respectively, of operational amplifier 4. The output terminal of operational amplifier 4, which corresponds to a voltage control circuit, is connected to the bases of BJT1 and BJT2.

[0012] In the above, the resistor elements R1 to R3 correspond to a resistor voltage divider circuit, and the series circuit of the resistor elements R4 and R5 corresponds to a resistor series circuit. The BJTs 1 and 2 and the resistor series circuit correspond to a transistor circuit. The circuit portion connected in parallel to the Zener diode 3 constitutes a current generating circuit 5.

[0013] Next, the operation of this embodiment will be described. Nodes (1) to (7) are defined as follows. Node(1): Cathode of Zener diode 3 Node (2): Common connection point of resistor element R1 and resistor elements R2 and R3 Nodes (3), (4): Collectors of BJT1 and BJT2 Node (5): Base of BJT1 and 2 Nodes (6), (7): Emitters of BJT1 and BJT2

[0014] The reference voltage generating circuit 1 generates a reference voltage V REF is generated and output from node (2). REF is generated as follows. Let resistor R2=R3, and the area ratio of BJT1 to BJT2 be n:1. Let the voltages at nodes (5) to (7) be V5 to V7. Let the base-emitter voltages of BJT1 and BJT2 be V BE1 , V BE2 Let's say. V BE1 =V5-V6…(1) V BE2 =V5-V7…(2) The potential difference (V6-V7) associated with the resistor element R4 is given by equation (3). V6-V7=ΔV BE1 =VBE2 -V BE1 =(k B T / q)logn …(3) k B is the Boltzmann constant, T is the absolute temperature, and q is the elementary charge.

[0015] The voltage (V6-V7) is directly proportional to the absolute temperature, and as a result, a current I ptat ={k B T / (qR4)}logn flows. Also, the voltages at nodes (3) and (4) become equal due to the action of operational amplifier 4. And, since resistance R2=R3, the current I ptat is playing.

[0016] From the above, the voltage at node (1) is the Zener voltage V z Then, the voltage V2 at node (2) is expressed by the following equation (4). V2=V REF =V Z -2R1I ptat =V Z -2R1{k B T / (qR4)}logn …(4) In equation (4), the current I ptat By adjusting the temperature dependency of the Zener voltage V z It can be seen that a voltage is obtained that cancels out the temperature dependence of

[0017] As described above, according to this embodiment, the reference voltage generating circuit 1 includes the Zener diode 3 connected between the current source 2 and the ground, and the current generating circuit 5 connected in parallel to the Zener diode 3. The current generating circuit 5 has a branching section that branches the current into two paths, and includes a resistive voltage dividing circuit that outputs a voltage divided by resistive elements R1 to R3, a transistor circuit, and a voltage control circuit.

[0018] The transistor circuit has two NPN transistors BJT1 and BJT2, whose collectors are connected to the two paths and whose bases are connected in common, and a series resistor circuit made up of resistors R4 and R5 connected in series between the emitter of transistor BJT1 and ground, with the emitter of transistor BJT2 connected to the common node of resistors R4 and R5. Operational amplifier 4 controls transistors BJT1 and BJT2 so that the collector potentials are equal.

[0019] With this configuration, the current Iptat, which has the above-mentioned positive temperature dependency, is a current that depends on the voltage difference ΔVBE between the base emitters of the two NPN transistors BJT1 and BJT2, and the collector current that flows through the pair of transistors BJT1 and BJT2 can be controlled with high precision by the resistor voltage divider circuit and operational amplifier 4. The current Iptat can be adjusted by changing the resistance ratio of the two paths in the resistor voltage divider circuit. The voltage divided by the resistor voltage divider circuit is then fed to the reference voltage V REF Therefore, there is no influence of errors due to the current mirror circuit, and the reference voltage V REF The temperature dependency of the temperature can be accurately corrected.

[0020] (Second embodiment) In the following, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted, and the different parts will be described. As shown in FIG. 2, in the reference voltage generating circuit 11 of the second embodiment, A and R B The series circuit is connected in parallel to the Zener diode 3. The upper end of the resistor R1 is connected to the resistor R A and R B In the above, the resistor element R A and R B A current generating circuit 6 is configured by adding a configuration equivalent to the current generating circuit 5 of the first embodiment to this series circuit.

[0021] Next, the operation of the second embodiment will be described. ptat The resistance element RA and R B If the common connection point is node (2'), the voltage V2' at node (2') is expressed by the following equation (5). V2'=V2+2R1I ptat =V2+2R1{k B T / (qR4)}logn …(5)

[0022] Resistance element R A The current flowing through the resistor element R is I. B If the current flowing through is I', then I=I'+2I ptat …(6) and the resistive element R A Terminal voltage R A From equation (7) showing I, the current I' is expressed as equation (8). R A I=V Z -R B I'...(7) R A (I'+2I ptat )=V Z -R B I' I'=(V z -2R A I ptat ) / (R A +R B ) …(8) (V2'=R B I'), the voltage V2' is given by equation (9). V2'=R B (V Z -2R A I ptat ) / (R A +R B ) …(9)

[0023] From equations (5) and (9), the output voltage V of the reference voltage generating circuit 11 is REF When this is calculated, we obtain equation (10). V2=V REF =R B V Z / (R A +R B ) -2(RA R B +R1R A +R1R B )I ptat / (R A +R B ) …(10)

[0024] As described above, according to the second embodiment, in equation (10), the current I ptat By adjusting the temperature dependency of the Zener voltage V Z The temperature dependence of the reference voltage V REF can be obtained.

[0025] (Third embodiment) In the reference voltage generating circuit 21 of the third embodiment shown in FIG. 3, the resistor elements R2 and R3 enclosed in boxes have a variable resistance value as shown in FIG. 4. The upper ends of the resistor elements R2 and R3 are terminal A, and the lower ends are terminal B. Nodes (3') and (4') connected to the input terminals of the operational amplifier 4 are terminal C. For example, four resistor elements R are connected in series, and four switches SW1 to SW4 are connected between the common connection point of the resistor elements, terminal B, and terminal C. These switches SW1 to SW4 are, for example, MOSFETs. In the above, the resistor elements R and switches SW1 to SW4 correspond to a potential adjustment circuit, and the circuit portion connected in parallel with the Zener diode 3 constitutes the current generating circuit 7.

[0026] Next, the operation of the third embodiment will be described. The base-emitter voltages of the transistors BJT1 and BJT2 are V BE1 ,V BE2 Then, these are expressed as follows: V BE1 =V5-V6…(11) V BE2 =V5-V7…(12)

[0027] From these, the potential difference (V6-V7), which is the terminal voltage of the resistor element R4, is expressed as equation (13). The collector currents of the transistors BJT1 and BJT2 are respectively I C1 ,IC2 Let's say. V6-V7=ΔV BE =V BE2 -V BE1 =k B T / q{logn+log(I C2 / I C1 )} …(13) Collector current I C1 is expressed as equation (14). I C1 =k B T / (qR4){logn+log(I C2 / I C1 )} …(14)

[0028] The voltages at nodes (3') and (4') are equalized by the action of operational amplifier 4, so the potential difference between node (2) and node (3') and the potential difference between node (2) and node (4') are also equalized. Therefore, by changing the weighting of resistor elements R2 and R3, the resistance values ​​between node (2) and node (3') and between node (2) and node (4') can be adjusted to R2' and R3', respectively, and the collector current I flowing through transistor BJT2 can be adjusted. C2 is expressed as equation (15). I C2 =(R2' / R3')I C1 …(15)

[0029] Since the voltage at node (1) is the Zener voltage VZ, the voltage V2 at node (2), that is, the output voltage V of the reference voltage generating circuit 21, REF , is calculated as equation (16). V2=V REF =V Z -R1(I C1 +I C2 ) =V Z -k B TR1 / (qR4)(1+R2' / R3') ×{logn+log(R2' / R3')} …(16)

[0030] According to the third embodiment configured as above, in equation (16), the current I ptatBy adjusting the resistance ratio (R1 / R4), the temperature dependence of the Zener voltage V Z In addition, by adjusting the resistance ratio (R2' / R3') by changing the weighting of the resistor elements R2 and R3, the current I ptat The influence of variations in the

[0031] (Fourth and fifth embodiments) 5 is configured such that a diode-connected NPN transistor BJT3 is connected between the current source 2 and the resistor element R1 in the reference voltage generating circuit 1 of the first embodiment. The circuit portion connected in parallel to the Zener diode 3 constitutes a current generating circuit 8.

[0032] 6, the base of a transistor BJT3 is connected to the node (2) in the reference voltage generating circuit 1 of the first embodiment. A current source 42 similar to the current source 2 is connected to the collector of the transistor BJT3, and a voltage V REF The circuit portion connected in parallel to the Zener diode 3 constitutes a current generating circuit 9.

[0033] Next, the operation of the fourth and fifth embodiments will be described. BE3 The output voltage V of the reference voltage generating circuits 31 and 41 is REF is the Zener voltage V in the first embodiment Z , (V Z -V BE3 ) can be replaced with V REF =(V Z -V BE3 )-2R1{k B T / (qR4)}logn …(17) In equation (17), the current I ptat By adjusting the resistance ratio, the temperature dependence of Z -V BE3 ) can be canceled out. Also, in equation (17), the voltage V REF The stress dependence of is expressed by equation (18).

[0034]

number

[0035] In equation (18), the voltage V between the cathode and anode of Zener diode 2 Z The voltage V of the nonlinear element is BE3 If we select a material with similar stress dependence, V REF The stress dependence of the

[0036] (Other embodiments) The switch circuit is not limited to MOSFETs. The number of resistor elements and switch circuits that make up the potential adjustment circuit may be changed as appropriate according to individual designs. The configuration in which the resistance value can be changed in the third embodiment may be applied to the fourth and fifth embodiments. Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0037] In addition to the inventions described in the claims, this case also includes the following inventions: [1] a Zener diode (3) connected between the current source (2) and ground; a current generating circuit (5-9) that generates a current having a positive temperature dependency proportional to absolute temperature and is connected in parallel to the Zener diode; The current generating circuit includes: a resistive voltage divider circuit (R1 to R3) that has a branching section that branches a current into two paths and outputs a reference voltage divided by a resistive element; a transistor circuit including two NPN transistors (BJT1, BJT2) whose collectors are connected to the two paths respectively and whose bases are commonly connected, and a series resistor circuit (R4, R5) in which a plurality of resistor elements are connected in series, which is connected between the emitter of one of the two NPN transistors and ground, and whose other emitter is connected to the common connection point of the plurality of resistor elements; and a voltage control circuit (4) that controls the collector potentials of the two NPN transistors so that they are equal to each other. [2] The reference voltage generating circuit according to [1], wherein the voltage control circuit is composed of an operational amplifier having two input terminals connected to the collectors of the transistor circuits and an output terminal connected to the bases. [3] the resistive voltage divider circuit includes a series resistor circuit (RA, RB) in which a plurality of resistor elements are connected in series and which is connected in parallel to the Zener diode; The reference voltage generating circuit according to [1] or [2], wherein the branching section branches a current into two paths from a common connection point of any of the resistance elements that make up the series resistance circuit. [4] A reference voltage generating circuit according to any one of claims [1] to [3], comprising a semiconductor element (BJT3) having a PN junction in a path between the current source and a terminal that outputs the generated reference voltage. [5] The reference voltage generating circuit according to [4], wherein the semiconductor element is connected between the current source and a resistive voltage divider circuit that constitutes the current generating circuit. [6] the semiconductor element is an NPN transistor having a base connected to a branch point in the branch section and an emitter serving as a terminal for outputting the reference voltage, The reference voltage generating circuit according to [4], further comprising a current source (42) connected to the collector of the NPN transistor. [7] The reference voltage generating circuit according to any one of [1] to [6], wherein the resistive voltage dividing circuit includes a potential adjusting circuit that adjusts the collector potential of each of the transistor circuits. [8] The potential adjustment circuit includes a series resistance circuit in which a plurality of resistance elements (R) are connected in series; The reference voltage generating circuit according to [7], comprising a plurality of switch circuits (SW1 to SW4) having one end connected in common and the other end connected to individual terminals of the series resistor circuit. [Explanation of symbols]

[0038] In the drawing, 1 denotes a reference voltage circuit, 2 denotes a current source, 3 denotes a Zener diode, 4 denotes an operational amplifier, 5 denotes a current generating circuit, R1 to R5 denote resistive elements, and BJT1 and 2 denote NPN transistors.

Claims

1. a Zener diode (3) connected between the current source (2) and ground; a current generating circuit (5-9) that generates a current having a positive temperature dependency proportional to absolute temperature and is connected in parallel to the Zener diode; The current generating circuit includes: A resistor voltage divider circuit (R) has a branching section that branches the current into two paths and outputs a reference voltage divided by a resistor element. １ ~R ３ )and, Two NPN transistors (BJT1, BJT2) have collectors connected to the two paths, respectively, and bases connected in common. A series resistor circuit (R ４ , R ５ a transistor circuit having the other emitter connected to a common connection point of the plurality of resistor elements; and a voltage control circuit (4) for controlling the collector potentials of the two NPN transistors so that they are equal to each other.

2. 2. The reference voltage generating circuit according to claim 1, wherein the voltage control circuit is comprised of an operational amplifier having two input terminals connected to the collectors of the transistor circuits and an output terminal connected to the bases.

3. The resistor voltage divider circuit is a series resistor circuit (R Ａ , R Ｂ ) 3. The reference voltage generating circuit according to claim 1, wherein the branching section branches a current into two paths from a common connection point of any one of the resistor elements that make up the series resistor circuit.

4. 3. The reference voltage generating circuit according to claim 1, wherein the resistive voltage dividing circuit includes a potential adjusting circuit that adjusts the collector potential of each of the transistor circuits.

5. The potential adjustment circuit includes a series resistance circuit in which a plurality of resistance elements (R) are connected in series; 5. The reference voltage generating circuit according to claim 4, further comprising a plurality of switch circuits (SW1 to SW4) each having one end connected to a common terminal and the other end connected to each of the terminals of the series resistor circuit.

6. 3. The reference voltage generating circuit according to claim 1, further comprising a semiconductor element (BJT3) having a PN junction in a path between the current source and a terminal for outputting the generated reference voltage.

7. 7. The reference voltage generating circuit according to claim 6, wherein the semiconductor element is connected between the current source and a resistive voltage dividing circuit that constitutes the current generating circuit.

8. the semiconductor element is an NPN transistor having a base connected to a branch point in the branch section and an emitter serving as a terminal for outputting the reference voltage, 7. The reference voltage generating circuit of claim 6, further comprising a current source (42) connected to the collector of said NPN transistor.

9. 8. The reference voltage generating circuit according to claim 7, wherein the resistive voltage dividing circuit includes a potential adjusting circuit that adjusts the collector potential of each of the transistor circuits.

10. The potential adjustment circuit includes a series resistance circuit in which a plurality of resistance elements (R) are connected in series; 10. The reference voltage generating circuit according to claim 9, further comprising a plurality of switch circuits (SW1 to SW4) each having one end connected to a common terminal and the other end connected to each of the terminals of the series resistor circuit.

11. 9. The reference voltage generating circuit according to claim 8, wherein the resistive voltage dividing circuit includes a potential adjusting circuit that adjusts the collector potential of each of the transistor circuits.

12. The potential adjustment circuit includes a series resistance circuit in which a plurality of resistance elements (R) are connected in series; 12. The reference voltage generating circuit according to claim 11, further comprising a plurality of switch circuits (SW1 to SW4) each having one end connected to a common terminal and the other end connected to each of the terminals of the series resistor circuit.

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