A temperature compensation circuit for a bandgap reference circuit

Abstract

The present invention discloses a temperature compensation circuit for a bandgap reference circuit in the field of temperature compensation, which includes a bandgap reference circuit and a first-stage compensation circuit, and further includes a second-stage compensation circuit. The input ends of the first-stage compensation circuit and the second-stage compensation circuit are both connected to the reference voltage output end of the bandgap reference circuit, and the output ends respectively output a first-stage compensation current and a second-stage compensation current to the voltage dividing circuit of the bandgap reference circuit. After the compensation current passes through the resistor on the voltage dividing circuit, a compensation voltage is generated to perform temperature compensation on the output voltage of the bandgap reference circuit. The first-stage compensation current has a first-order positive temperature coefficient, and the second-stage compensation current has a second-order positive temperature coefficient. The present invention introduces a second-stage compensation current to perform temperature compensation on the bandgap reference circuit, reducing the proportion originally occupied by the current source. The second-stage compensation current has a change rate close to that of the base-emitter voltage of the triode and has better temperature characteristics, enabling fine temperature compensation.

Description

Technical Field

[0001] The present invention relates to the field of temperature compensation, and specifically to a temperature compensation circuit for a bandgap reference circuit. Background Art

[0002] In recent years, with the rapid development of integrated circuits, reference voltage sources have become increasingly important in analog integrated circuits, analog-to-digital hybrid circuits, and system-on-chip integrated circuits. Among them, the reference voltage source has a particularly profound impact on analog integrated circuits. A reference source that does not change with the external temperature often determines the performance of the entire analog integrated circuit. Therefore, the low temperature drift characteristic in the full temperature range is an important pursuit direction for the reference source.

[0003] The bandgap reference is a classic voltage reference source that is independent of the power supply voltage and the ambient temperature. Its main principle is to generate a quantity that is constant with temperature change. The base-emitter voltage VBE of a bipolar device has a negative temperature coefficient during temperature change, while the base-emitter voltage difference ΔVBE between two bipolar devices with different current densities has a positive temperature coefficient. Through appropriate coefficient weighting, the temperature drift characteristic of VBE is offset within a certain range, so as to obtain an output voltage VREF with approximately zero temperature drift. This is the basic design idea of this type of reference voltage source.

[0004] However, during the design and manufacturing process of integrated circuits, the base-emitter voltage VBE of bipolar devices does not completely show linearity with temperature in the full temperature range. The approximately zero temperature drift output voltage brought by the above circuit structure often presents a parabolic curve. The temperature drift coefficient presented by this curve is affected by the manufacturing process, and sometimes it cannot fully meet the index of "zero" temperature drift amount, resulting in overall parameter out-of-tolerance. How to make up for such problems through design is an important research direction.

[0005] During the design and manufacturing process of the classic bandgap reference, due to the fact that the V BE value of the internal triode device is restricted by process conditions, the performance of the designed bandgap reference is often low. For the conventional segmented temperature compensation technology, its mainstream expression is a piecewise function. Since a compensation current branch is introduced, the chip will increase the layout area and the overall power consumption. And segmented compensation can often only perform relatively rough compensation. Therefore, for circuits with high precision requirements, multi-segment compensation needs to be introduced, which means introducing more current branches, resulting in a large waste of layout and power consumption. In actual process production, the deviation of the process makes it difficult to ensure the matching of multi-segment compensation, which will lead to a reduction in the product yield. Summary of the Invention

[0006] The purpose of the present invention is to provide a temperature compensation circuit for a bandgap reference circuit to solve the problems raised in the above background art.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A temperature compensation circuit for a bandgap reference circuit, including a bandgap reference circuit and a first-stage compensation circuit, further including a second-stage compensation circuit. The input ends of the first-stage compensation circuit and the second-stage compensation circuit are both connected to the reference voltage output end of the bandgap reference circuit, and the output ends respectively output a first-stage compensation current and a second-stage compensation current to the voltage dividing circuit of the bandgap reference circuit. After the compensation current passes through the resistors on the voltage dividing circuit, a compensation voltage is generated to perform temperature compensation on the output voltage of the bandgap reference circuit; the first-stage compensation current has a first-order positive temperature coefficient, and the second-stage compensation current has a second-order positive temperature coefficient.

[0009] Further, the first-stage compensation circuit includes first, second, and third NPN transistors, and resistors Ra, Rb, Rc, Rd, and Re; the base of the first NPN transistor is connected to the reference voltage output end of the bandgap reference circuit, the collector is connected to the power supply terminal, and the emitter is sequentially connected to the resistor Rb and Ra and then grounded; the base of the second NPN transistor is connected to its own collector, the collector is connected to the voltage dividing circuit of the bandgap reference circuit through the resistor Rd, and the emitter is connected to the collector of the third NPN transistor; the base of the third NPN transistor is connected to the common terminal of the resistors Rb and Ra through the resistor Re, and the emitter is grounded through the resistor Rc.

[0010] Further, the second-stage compensation circuit includes fourth to ninth NPN transistors, first to fifth PNP transistors, a first resistor, a second resistor, and a third resistor; the collector of the fourth NPN transistor is connected to the power supply terminal, the base is connected to the reference voltage output end of the bandgap reference circuit, and the emitter is connected to the collector of the fifth NPN transistor through the first resistor; the collector of the fifth NPN transistor is connected to its own base, the base is connected to the base of the sixth NPN transistor, and the emitters of the fifth and sixth NPN transistors are grounded; the collector of the sixth NPN transistor is connected to the emitter of the seventh NPN transistor, and the base of the seventh NPN transistor is connected to its own collector; the emitters of the first and third PNP transistors are connected to the power supply terminal, the bases are connected, the collector of the first PNP transistor is also connected to its own base and the emitter of the second PNP transistor, and the base of the second PNP transistor is connected to the base of the fourth PNP transistor, its own collector, and the collector of the seventh NPN transistor; the collector of the third PNP transistor is connected to the emitter of the fourth PNP transistor, the base of the fifth PNP transistor, and the second end of the third resistor, and the first end of the third resistor is connected to the emitter of the fifth PNP transistor and the power supply terminal; the collector of the fourth PNP transistor is grounded through the second resistor; the emitter of the fifth PNP transistor is connected to the collector and base of the ninth NPN transistor, and the emitters of the eighth and ninth NPN transistors are grounded, the bases are connected, and the collector of the eighth NPN transistor is connected to the voltage dividing circuit of the bandgap reference circuit.

[0011] Further, the ratio of the emitter areas of the first PNP transistor and the third PNP transistor is 2:1.

[0012] Further, the ratio of the emitter areas of the second PNP transistor and the fourth PNP transistor is 2:2.

[0013] Beneficial effects: Through the first-level compensation circuit and the second-level compensation circuit, the present invention introduces a second-level compensation current with a second-order positive temperature coefficient that varies with temperature to complete circuit compensation. When entering the high-temperature part with a higher change curvature, after the introduction of the second-level compensation current, the proportion of the original current source is reduced, and the second-level compensation current has a rate of change close to that of the transistor VBE and has better temperature characteristics, enabling fine temperature compensation. Description of the Drawings

[0014] Figure 1 is the basic structure diagram of a classical Widlar bandgap reference circuit;

[0015] Figure 2 is the temperature characteristic curve of a classical Widlar bandgap reference circuit;

[0016] Figure 3 is the basic structure diagram of a classical Widlar bandgap reference circuit connected to a first-level compensation circuit;

[0017] Figure 4 is the temperature characteristic curve diagram of a classical Widlar bandgap reference circuit after first-level compensation;

[0018] Figure 5 is the basic structure diagram of the classical Widlar bandgap reference circuit in the present invention connected to the first-level and second-level compensation circuits;

[0019] Figure 6 is the temperature characteristic curve diagram of the classical Widlar bandgap reference circuit in the present invention after first-level and second-level compensation;

[0020] Figure 7 is the basic structure diagram of the bandgap reference circuit of Embodiment 1 of the present invention;

[0021] Figure 8 is the temperature characteristic curve diagram of the bandgap reference circuit of Embodiment 1 of the present invention;

[0022] Figure 9 is the basic structure diagram of the bandgap reference circuit of Embodiment 1 of the present invention connected to a first-level compensation circuit;

[0023] Figure 10 is the temperature characteristic curve diagram of the bandgap reference circuit of Embodiment 1 of the present invention after first-level compensation;

[0024] Figure 11The basic structure diagram of the bandgap reference circuit of Embodiment 1 of the present invention connected to the first-stage and second-stage compensation circuits;

[0025] Figure 12 The temperature characteristic curve diagram of the bandgap reference circuit of Embodiment 1 of the present invention after first-stage and second-stage compensation;

[0026] Figure 13 The basic structure diagram of the bandgap reference circuit of Embodiment 2 of the present invention;

[0027] Figure 14 The basic structure diagram of the bandgap reference circuit of Embodiment 2 of the present invention connected to the first-stage and second-stage compensation circuits;

[0028] Figure 15 The basic structure diagram of the bandgap reference circuit of Embodiment 3 of the present invention;

[0029] Figure 16 The basic structure diagram of the bandgap reference circuit of Embodiment 3 of the present invention connected to the first-stage and second-stage compensation circuits. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] As Figure 1 shown, the classic Widlar bandgap reference circuit includes a current source, NPN transistors Q1 to Q4, and resistors R1 to R5. The first end of the current source is connected to the collector of NPN transistor Q4 to supply the power supply terminal VCC; the second end of the current source is connected to the base of NPN transistor Q4 and the collector of NPN transistor Q3. The emitter of NPN transistor Q3 is grounded, and the base is connected to the collector of NPN transistor Q2 and the second end of resistor R2; the emitter of NPN transistor Q4 is connected to the first end of resistor R5, the second end of resistor R5 is connected to the first end of resistor R4, the second end of resistor R4 is connected to the first ends of resistors R1 and R2, the second end of resistor R1 is connected to the collector, base of NPN transistor Q1 and the base of NPN transistor Q2, the emitter of NPN transistor Q2 is grounded through resistor R3, and NPN transistor Q1 is grounded. Resistors R4 and R5 constitute the voltage dividing circuit of the bandgap reference circuit, where R5 is the resistor for generating the compensation voltage with the compensation current.

[0032] When the temperature compensation switch is not turned on, in the ideal state of the basic structure of the classic Widlar bandgap reference, the finally output output voltage value is:

[0033] Vout = V ref + (R4 + R5) × (I1 + I2)

[0034] Assume that all the transistor characteristics are the same, then there is:

[0035]

[0036]

[0037] Combining the two equations, we can get:

[0038] I1R1 = I2R2

[0039] In this way, according to the above logical equation, we can get:

[0040]

[0041] When Q1 and Q2 are devices of the same type, there is

[0042] Then we can get:

[0043]

[0044] The finally output V OUT value equation is:

[0045]

[0046] From the above formula, it can be obtained that in the classical bandgap reference structure, the finally output voltage is the sum of a positive temperature coefficient voltage of a constant term and a negative temperature coefficient voltage V BE where V T is a voltage with a linear positive temperature coefficient, and a proper constant coefficient is needed to compensate the negative temperature coefficient of V BE so as to obtain a zero temperature coefficient voltage for making V OUT theoretically a voltage value independent of temperature.

[0047] According to the characteristics of the transistor, the base-emitter voltage V BE of the transistor, although it is a voltage with a negative temperature coefficient, does not have a linear temperature characteristic.

[0048] For the base-emitter voltage V BE of the transistor, there is:

[0049]

[0050] Among them, the V G0 voltage is a basic constant, and this value is related to the collector current I Cis approximately constant with respect to temperature, then V BE The derivative with respect to temperature T is as follows:

[0051]

[0052] At the same time, the collector current I C The relationship with temperature T is:

[0053]

[0054] When T = T0, the collector current I C The relationship with temperature T can be expressed as:

[0055]

[0056] Dividing the above two equations and performing logarithmic operations, we get:

[0057]

[0058]

[0059] Through the above calculation, the base-emitter voltage V BE The expression related to temperature T can be written as:

[0060]

[0061] After simplification, we get:

[0062] V BE (T) = V0 + η0T + f0 (T)

[0063] It can be seen that during the temperature change, a high-order variable appears, which makes the entire V BE The value of V does not change linearly with temperature. When the temperature rises rapidly, BE The slope decreases faster. Figure 2 As shown, in a general bandgap reference circuit, the characteristic curve of the entire output voltage changing with temperature presents a parabolic form, and the transistor V BE When the rate of change is fast, it will show strong nonlinearity in high temperature environment, and its curvature is closer to a quadratic function in high temperature environment.

[0064] The temperature compensation circuit provided by the prior art generally includes a bandgap reference circuit and a primary compensation circuit. The input end of the primary compensation circuit is connected to the reference voltage output end of the bandgap reference circuit, and the output end outputs a primary compensation current to the voltage divider circuit of the bandgap reference circuit. The main principle is to divide the working range of the entire reference circuit into multiple sections and compensate each temperature section.

[0065] Taking the two-stage compensation most commonly used in the chip design process as an example, its basic principle structure is as follows Figure 3 shown. The first-stage compensation circuit includes the first, second, and third NPN transistors, and resistors Ra, Rb, Rc, Rd, and Re. The base of the first NPN transistor Q5 is connected to the reference voltage output terminal V of the bandgap reference circuit REF , the collector is connected to the power supply terminal VCC, and the emitter is connected to the ground after sequentially connecting resistors Rb and Ra. The base of the second NPN transistor Q6 is connected to its own collector, and the collector is connected to the voltage-dividing circuit of the bandgap reference circuit, that is, between resistors R4 and R5, and the emitter is connected to the collector of the third NPN transistor Q7. The base of the third NPN transistor Q7 is connected to the common terminal of resistors Rb and Ra through resistor Re, and the emitter is grounded through resistor Rc.

[0066] Since the base-emitter voltage V BE value of the triode changes with a negative temperature coefficient as the temperature changes, and the change in the value of the reference voltage relative to the V BE value of the triode is very small. During the actual working process, V NL samples from the reference voltage output terminal V REF to control the triode switch of the compensation branch. The sampling potential V NL value is:

[0067]

[0068] This V NL controls the triode switch, and the V COM port forms an additional current window to compensate the bandgap reference circuit. The introduced current value is:

[0069]

[0070] Using the first-stage compensation circuit to perform temperature compensation on the bandgap reference circuit, the output port V COM in the first-stage compensation circuit is connected Figure 1 between resistors R4 and R5 in the classic bandgap reference circuit in OUT for a certain compensation, and the function expression of V OUT in the form of a piecewise function can be obtained:

[0071]

[0072] If only the first-stage compensation circuit is used to compensate the bandgap reference circuit, by approximately equivalent the above function into a characteristic curve changing with temperature, the characteristic curve of the voltage of the compensated bandgap reference circuit changing with temperature can be obtained as Figure 4 shown.

[0073] From Figure 4It can be seen that the primary compensation current provided by the primary compensation circuit generates a temperature compensation voltage through the voltage division circuit, which can compensate the bandgap reference source within a certain range. By adjusting the ratio of R5 to Rc, a relatively rough first-order temperature compensation can be obtained. However, the temperature curve of the compensated bandgap reference source shows that the ordinary two-stage segmented compensation circuit is closer to introducing a first-order compensation temperature coefficient. Since the linear segmented compensation only affects the overall when the segmented switch is turned on and the compensation amount is small, if a bandgap reference circuit with a lower temperature drift is required, multiple-stage temperature compensation often needs to be introduced, which makes the circuit complex and difficult to perform fine compensation.

[0074] In view of the above defects caused by only compensating the bandgap reference circuit through the primary compensation circuit, the temperature compensation circuit provided in this application further includes a secondary compensation circuit. The input end of the secondary compensation circuit is connected to the reference voltage output end V of the bandgap reference circuit REF and the output end outputs a secondary compensation current to the voltage division circuit of the bandgap reference circuit, and the voltage generated by the voltage division circuit is used to perform temperature compensation on the output voltage of the bandgap reference circuit.

[0075] Through the foregoing analysis, the expression of the triode V BE with temperature is as follows:

[0076] V BE (T) = V0 + η0T + f0T 2

[0077] From Figure 2 the classical bandgap reference temperature curve, when the change rate of the triode V BE changes rapidly, it will show strong nonlinearity in the high-temperature environment state, and its curvature is closer to a quadratic function in the high-temperature environment. In order to obtain a better temperature drift coefficient, it is necessary to convert the compensation coefficient into a second-order coefficient as much as possible to be closer to the temperature characteristics of the triode.

[0078] In some embodiments, as Figure 5 shown, the secondary compensation circuit includes the fourth NPN transistor to the ninth NPN transistor, the first PNP transistor to the fifth PNP transistor, the first resistor R10, the second resistor R11 and the third resistor R12; the collector of the fourth NPN transistor Q8 is connected to the power supply terminal VCC, the base is connected to the reference voltage output terminal of the bandgap reference circuit, and the emitter is connected to the collector of the fifth NPN transistor Q9 through the first resistor R10; the collector of the fifth NPN transistor Q9 is connected to its own base, and the base is connected to the base of the sixth NPN transistor Q10. The emitters of the fifth and sixth NPN transistors Q9 and Q10 are grounded; the collector of the sixth NPN transistor Q10 is connected to the emitter of the seventh NPN transistor Q11, and the base of the seventh NPN transistor Q11 is connected to its own collector;

[0079] The emitters of the first and third PNP transistors Q13 and Q14 are connected to the power supply terminal, and their bases are connected. The collector of the first PNP transistor Q13 is also connected to its own base and the emitter of the second PNP transistor Q12. The base of the second PNP transistor Q12 is connected to the base of the fourth PNP transistor Q15, its own collector, and the collector of the seventh NPN transistor Q11. The collector of the third PNP transistor Q14 is connected to the emitter of the fourth PNP transistor Q15, the base of the fifth PNP transistor Q15, and the second terminal of the third resistor R12. The first terminal of the third resistor R12 is connected to the emitter of the fifth PNP transistor Q16 which is connected to the power supply terminal. The collector of the fourth PNP transistor Q15 is grounded through the second resistor R11. The emitter of the fifth PNP transistor Q16 is connected to the collector and base of the ninth NPN transistor Q17. The emitters of the eighth and ninth NPN transistors Q18 and Q17 are grounded, and their bases are connected. The collector of the eighth NPN transistor Q18 is connected to the common terminal of the resistors R4 and R5 of the bandgap reference circuit.

[0080] It should be noted that the ratio of the emitter areas of the first PNP transistor Q13 and the third PNP transistor Q14 is 2:1; the ratio of the emitter areas of the second PNP transistor Q12 and the fourth PNP transistor Q15 is 2:2. In this way, the sampling current generated from the VREF point can be evenly divided, and a sampling current that changes with the voltage of the VREF port and has a first-order temperature coefficient can be replicated. The purpose is to use this current to generate a current with a second-order temperature coefficient to compensate the circuit. During the circuit setup process, generally, the emitter area is increased by increasing the number of PNP transistors.

[0081] Since the VBE of the triode has a negative temperature coefficient, a PTAT current with a positive temperature coefficient is formed in the branch of the fourth NPN transistor Q8, the first resistor R10, and the fifth NPN transistor Q9. This branch can generate a second-order PTAT current after passing through the current mirror group.

[0082] The current of this branch is mirror-copied through the current mirror group composed of the fifth NPN transistor Q9 and the sixth NPN transistor Q10, and the current mirror group composed of the first PNP transistor Q13, the second PNP transistor Q12, the third PNP transistor Q14, and the fourth PNP transistor Q15. The mirrored PTAT current and the third resistor R12 generate a PTAT voltage. Through the amplification of the fifth PNP transistor Q16, a second-order positive temperature coefficient current I PTAT 2 :

[0083] (β is the amplification factor of the fifth PNP transistor Q16, positive temperature coefficient)

[0084] Second-order positive temperature coefficient current I PTAT 2It is fed back into the bandgap reference circuit through a current mirror and forms a second-order positive temperature coefficient voltage V with resistor R5. PTAT 2 . By changing the resistance value of resistor R 10 , the high-order temperature compensation for the output voltage can be adjusted.

[0085] Since a secondary compensation current with a second-order positive temperature coefficient that varies with temperature is introduced to complete the circuit compensation, when entering the high-temperature part with a higher change curvature, the proportion of the original current source is reduced after the introduction of the secondary compensation current, and the secondary compensation current has a change rate close to that of the base-emitter voltage V of the triode. BE Compared with the original compensation circuit, it has better temperature characteristics, and its expression is:

[0086]

[0087] Therefore, after the bandgap reference circuit is compensated by the first-stage compensation circuit and the second-stage compensation circuit, the expression of the output voltage with respect to temperature can be rewritten as:

[0088]

[0089] As Figure 6 shown, it can be found that compared with the uncompensated bandgap reference circuit and the bandgap reference circuit only compensated by the first-stage compensation circuit, the temperature drift coefficient of the temperature characteristic curve of the bandgap reference circuit compensated by the first-stage and second-stage compensation circuits in this application is lower.

[0090] In this application, the first-stage compensation circuit provides the first-stage compensation current, and the second-stage compensation circuit provides the second-stage compensation current. By changing the originally linear positive temperature coefficient, the slope of the positive temperature coefficient voltage of the bandgap reference circuit with respect to temperature can be made more consistent with the base-emitter voltage V of the triode. BE Thus, the temperature drift property of the bandgap reference can be effectively reduced in a wider temperature range, and a bandgap reference source with higher precision and better performance can be produced under the condition of limited process device performance.

[0091] Example 1, as Figure 7 shown, taking the TL431 bandgap reference circuit as an example, the chip is designed and manufactured using a domestic bipolar process line. In the circuit design process, a classic bandgap reference structure is adopted, and the positive and negative temperature coefficient voltages are balanced, and its V REF value is about 2.5V.

[0092] Based on a domestic bipolar process line, the result of the simulation verification of the entire chip is as Figure 8 shown. Affected by the base-emitter voltage difference V of the bipolar device in the process BEPerformance impact: The maximum temperature drift difference of this bandgap reference circuit reaches 26.77 mV. The temperature coefficient expression in the performance parameters is as follows:

[0093]

[0094] The temperature coefficient of this bandgap reference is 61.17 ppm / °C, and its performance is average.

[0095] As Figure 9 shown, after the temperature compensation of this bandgap reference circuit through a first-stage compensation circuit, the simulation results under the same process are as Figure 10 shown. It can be seen from the simulation results that the results after the first-stage segmented compensation basically conform to the temperature characteristic curve of the conventional segmented temperature compensation. In terms of performance, for the bandgap reference circuit after the first-stage compensation, its maximum temperature drift amount drops to 17.11 mV. Compared with the previous temperature drift amount of 26.77 mV, the performance is improved by nearly 60%. Although it already meets most application scenarios, it is not suitable for some higher-precision fields.

[0096] As Figure 11 shown, in this embodiment, the bandgap reference circuit of this embodiment is compensated by a first-stage compensation circuit and a second-stage compensation circuit, and the entire compensation curve is closer to the performance curve of the original triode. In the actual application process, the input ends of the first-stage compensation circuit and the second-stage compensation circuit are connected to the reference voltage output end V REF of the bandgap reference circuit. When the device is in a high-temperature state, both the first-stage compensation circuit and the second-stage compensation circuit start to work, and respectively generate I PTAT current and I PTAT 2 current. The two currents are connected between the resistors R2 and R3 on the bandgap reference branch to perform temperature compensation on the overall V REF of the bandgap reference circuit.

[0097] After compensating through the temperature compensation circuit provided in this embodiment, the simulation results obtained under the same process are as Figure 12 shown. It can be clearly seen that compared with the ordinary segmented compensation circuit, the temperature compensation circuit of the present invention introduces a new balance point of positive and negative temperature coefficients, and the compensation effect is closer to the physical characteristics of the triode itself, reducing the temperature drift of the reference voltage of the bandgap reference circuit to about 6 mV. Compared with the initial uncompensated bandgap reference circuit, the performance of this method has increased by a full 350%. Compared with the bandgap reference circuit after the first-stage compensation, there is also a performance improvement of nearly 200%.

[0098] Embodiment 2: As Figure 13 shown, taking the LM236 bandgap reference circuit as an example, the final output value of this chip is V+ = 2.5V, but the implementation method is slightly different from that of TL431.

[0099] For the LM236, the reference output potential point is the ADJ port, and the output value is approximately about 1.25V. The ADJ port is equivalent to the port Vref in the above text. The actual size of the output port V+ relative to the reference voltage output terminal VREF of the bandgap reference circuit is determined by the following formula:

[0100]

[0101] Among them, Q 15 、Q 16 's V BE difference is a positive temperature coefficient. From the foregoing, it can be obtained that:

[0102]

[0103] As Figure 4 shown, the temperature compensation circuit of the present application is connected to the LM236 bandgap reference circuit. Similarly, for the LM236, the working principle of the compensation module is the same as that of the TL431. The input end of the compensation is introduced from the reference potential V+ port. In the high-temperature state, the compensation module starts to operate, generating a PTAT current and a PTAT 2 current is converted into a positive temperature coefficient voltage after being converted by a resistor and then compensates for V BE .

[0104] The value of the first-level compensation current generated is:

[0105]

[0106] The value of the second-level compensation current generated is:

[0107]

[0108] The two current compensations form first-level and second-level positive temperature coefficient compensation voltages at the ADJ port with R7 and R8 respectively, so as to better perform temperature compensation on the LM236. The compensated V+ value is:

[0109]

[0110] The compensation value includes a first-order function and a second-order function of temperature, and can be well compensated with V BE (T) = V0 + η0T + f0T 2 .

[0111] Example 3, as Figure 15 shown, the temperature compensation circuit of the present application is used to perform temperature compensation on the NCV1009 type reference chip. The output terminal of the NCV1009 type reference chip is V REF, and the output port is also the reference voltage generation port, and the triode N 12 、N 13 The emitter areas between them are in a ratio of 1:n, forming a voltage difference with a positive temperature coefficient.

[0112] The voltage value of its output port is:

[0113]

[0114] This formula is similar to the principles of TL431 and LM236. Similarly, the temperature compensation structure samples from the VREF port, generates a PTAT current and a PTAT 2 current, and connects it back to the current branch where N16 and N15 are located. It forms a compensation voltage with the resistor to compensate the BE curvilinear temperature characteristic curve of V. The connection method of the compensation structure is as Figure 16 shown.

[0115] After compensation:

[0116]

[0117] Thereby making VREF have a better temperature characteristic curve.

[0118] In the design process of bipolar chips, due to the relatively old existing bipolar process and the poor temperature characteristics of devices, the above embodiments show that the temperature compensation circuit provided by this application can achieve high-precision compensation for bandgap reference circuits, and is widely applicable to bandgap reference circuits on the existing market, which has important significance.

[0119] Although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0120] Therefore, the above are only the preferred embodiments of this application, and are not used to limit the scope of implementation of this application; that is, all equivalent transformations made according to the scope of the claims of this application are within the protection scope of the claims of this application.

Claims

1. A temperature compensation circuit for a bandgap reference circuit, comprising a bandgap reference circuit and a first-stage compensation circuit, characterized in that, It further includes a secondary compensation circuit. The input ends of the primary compensation circuit and the secondary compensation circuit are both connected to the reference voltage output end of the bandgap reference circuit, and the output ends respectively output a primary compensation current and a secondary compensation current to the voltage dividing circuit of the bandgap reference circuit. After the compensation current passes through the resistors on the voltage dividing circuit, a compensation voltage is generated to perform temperature compensation on the output voltage of the bandgap reference circuit. The primary compensation current has a first-order positive temperature coefficient, and the secondary compensation current has a second-order positive temperature coefficient; The secondary compensation circuit includes the fourth to ninth NPN transistors, the first to fifth PNP transistors, the first resistor, the second resistor, and the third resistor. The collector of the fourth NPN transistor is connected to the power supply terminal, the base is connected to the reference voltage output end of the bandgap reference circuit, and the emitter is connected to the collector of the fifth NPN transistor through the first resistor. The collector of the fifth NPN transistor is connected to its own base, the base is connected to the base of the sixth NPN transistor, and the emitters of the fifth and sixth NPN transistors are grounded. The collector of the sixth NPN transistor is connected to the emitter of the seventh NPN transistor, and the base of the seventh NPN transistor is connected to its own collector. The emitters of the first and third PNP transistors are connected to the power supply terminal, the bases are connected, the collector of the first PNP transistor is further connected to its own base and the emitter of the second PNP transistor, and the base of the second PNP transistor is connected to the base of the fourth PNP transistor, its own collector, and the collector of the seventh NPN transistor. The collector of the third PNP transistor is connected to the emitter of the fourth PNP transistor, the base of the fifth PNP transistor, and the second end of the third resistor. The first end of the third resistor is connected to the emitter of the fifth PNP transistor and the power supply terminal. The collector of the fourth PNP transistor is grounded through the second resistor. The emitter of the fifth PNP transistor is connected to the collector and the base of the ninth NPN transistor. The emitters of the eighth and ninth NPN transistors are grounded, the bases are connected, and the collector of the eighth NPN transistor is connected to the voltage dividing circuit of the bandgap reference circuit.

2. The temperature compensation circuit for a bandgap reference circuit according to claim 1, characterized in that, The primary compensation circuit includes the first, second, and third NPN transistors, and the resistors Ra, Rb, Rc, Rd, and Re. The base of the first NPN transistor is connected to the reference voltage output end of the bandgap reference circuit, the collector is connected to the power supply terminal, and the emitter is sequentially connected to the resistors Rb and Ra and then grounded. The base of the second NPN transistor is connected to its own collector, the collector is connected to the voltage dividing circuit of the bandgap reference circuit through the resistor Rd, and the emitter is connected to the collector of the third NPN transistor. The base of the third NPN transistor is connected to the common terminal of the resistors Rb and Ra through the resistor Re, and the emitter is grounded through the resistor Rc.

3. The temperature compensation circuit for a bandgap reference circuit according to claim 1, characterized in that, The ratio of the emitter areas of the first PNP transistor and the third PNP transistor is 2:

1.

4. The temperature compensation circuit for a bandgap reference circuit according to claim 1, characterized in that, The ratio of the emitter areas of the second PNP transistor and the fourth PNP transistor is 2:2.

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