A heating control circuit for a thermostat reference voltage source

Abstract

The application discloses a heating control circuit of a constant temperature reference voltage source, comprising a bias current generating circuit, a reference voltage generating circuit, a temperature sensor circuit, a heating unit control circuit and a heating circuit. The temperature sensor circuit uses the negative temperature characteristic of a triode Vbe to collect the chip temperature in real time and output a temperature sensing voltage, and the reference voltage generating circuit generates a low temperature coefficient reference voltage; the heating unit control circuit adopts a double same-phase amplifier to cooperate with a subtracter to form an analog operation closed loop structure, and outputs a continuous control voltage which monotonously changes with temperature; and the heating circuit continuously adjusts the heating power based on the characteristics of different working intervals of NMOS tubes. The application discloses a heating control circuit of a constant temperature reference voltage source, which discards the traditional switch heating control mode, eliminates the reference voltage jitter caused by the large current switching, effectively suppresses the temperature fluctuation caused by the temperature collection lag, controls the working temperature fluctuation of the reference chip within ±0.5 DEG C, and greatly reduces the reference voltage temperature drift to below 0.1ppm / DEG C.

Description

Technical Field

[0001] This invention belongs to the field of analog integrated circuits and precision reference source temperature control technology, specifically relating to a heating control circuit for a constant temperature reference voltage source. Background Technology

[0002] The reference voltage source is the core reference unit of various precision measuring equipment, industrial control systems, and data acquisition systems. The temperature stability of its output voltage directly determines the measurement accuracy and operational reliability of the entire system. Conventional bandgap reference voltage sources optimize the temperature coefficient through high-order temperature compensation and piecewise curvature compensation techniques, achieving a typical temperature drift of 2ppm / ℃. However, due to semiconductor process deviations, the temperature drift of batch chips is distributed in the range of 0.5~4ppm / ℃, and conventional compensation methods are no longer sufficient to further reduce the temperature drift.

[0003] The constant-temperature reference voltage source actively heats and maintains the reference chip at a constant high temperature range, which can significantly suppress the impact of ambient temperature fluctuations on the output voltage. The theoretical temperature drift can be controlled within 0.1ppm / ℃, making it the core implementation solution for ultra-high precision reference sources.

[0004] Existing constant temperature reference sources generally employ comparators or open-loop amplifiers to form a switching heating control architecture. This relies on a fixed threshold to turn the heating circuit on and off, achieving a rough constant temperature through average heating power. This traditional structure has inherent drawbacks: First, switching heating is a discrete control method, and the temperature sensor's signal acquisition has a lag, resulting in large fluctuations in the actual operating temperature of the chip, typically exceeding ±1℃. Second, frequent high-current switching of the heating unit introduces power supply disturbances and high-frequency noise, causing jitter in the reference output voltage and degrading the accuracy of the reference signal. Third, the low closed-loop coupling between the temperature sensing loop, the reference circuit, and the heating control loop makes it impossible to adaptively adjust the heating power according to real-time temperature changes, making it difficult to meet the requirements of ultra-high precision metrology scenarios in terms of temperature control accuracy and stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing on / off heating control technologies, such as large temperature fluctuations, easy output voltage jitter, lag in temperature response, and low temperature control accuracy. It provides a heating control circuit for a constant temperature reference voltage source, which replaces traditional on / off control with continuous analog calculation closed-loop control, realizes continuous adaptive adjustment of heating power, significantly improves the constant temperature accuracy of the reference chip, and reduces the temperature drift of the reference voltage.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A heating control circuit for a constant-temperature reference voltage source includes a reference voltage generation circuit, a temperature sensor circuit, a heating unit control circuit, and a heating circuit, characterized in that it further includes: (1) Bias current generating circuit, used to generate a stable reference bias current and provide bias current for the reference voltage generating circuit and temperature sensor circuit; The temperature sensor circuit is connected to the bias current generating circuit and is used to collect the real-time operating temperature of the reference voltage source and output a temperature sensing voltage signal that is negatively correlated with temperature. The reference voltage generating circuit is connected to the bias current generating circuit and is used to output a stable reference voltage signal after temperature compensation. (2) The two input terminals of the heating unit control circuit are respectively connected to the temperature sensor circuit and the reference voltage generation circuit. The temperature sensing voltage and the reference voltage are processed by analog calculation, and the continuously adjustable negative feedback control voltage is output to the heating circuit. The heating power of the heating power supply is continuously adjusted according to the amplitude of the control voltage, and the reference voltage source is subjected to closed-loop constant temperature heating to achieve stable control of the working voltage of the reference voltage source.

[0007] Based on the above technical solution, the following further technical solutions are proposed: The bias current generating circuit consists of NPN transistor Q1, NPN transistor Q2, PNP transistor Q3, PNP transistor Q4 and resistor R1. The bases of PNP transistors Q3 and Q4 are shorted, and their emitters are connected to the first power supply VDD. The collectors of PNP transistors Q3 and Q4 are connected to the collectors of NPN transistors Q1 and Q2, respectively. The base of NPN transistor Q2 is connected to the collector of transistor Q3. The bases of PNP transistors Q3 and Q4 are connected to the collector of Q4. Transistor Q1 serves as a temperature sensor, with its emitter grounded and its base output temperature sensing voltage Vsensor connected to the emitter of transistor Q2. The emitter of transistor Q2 is also connected to one end of resistor R1, and the other end of resistor R1 is grounded. The NPN transistor Q1 is multiplexed as the core temperature sensing device, using the temperature characteristics of the base-emitter voltage to generate the original bias current. PNP transistors Q3 and Q4 form a current mirror structure, replicating the original bias current and providing stable bias current for each functional circuit.

[0008] The reference voltage generating circuit consists of a PNP transistor Q5, a reverse-biased Zener diode D1, and a forward-biased diode D2. The emitter of the PNP transistor Q5 is connected to the first power supply VDD, the base is connected to the base of the transistor Q4, and the collector outputs a reference voltage Vref which is connected to the positive terminal of the reverse-biased Zener diode D1. The negative terminal of the reverse-biased Zener diode D1 is connected to the positive terminal of the forward-biased diode D2, and the negative terminal of the forward-biased diode D2 is grounded. The reverse-biased Zener diode D1 is a high-voltage Zener diode with a breakdown voltage greater than 6V and a positive temperature coefficient. The forward-biased diode D2 has a negative temperature coefficient. The reverse-biased Zener diode D1 and the forward-biased diode D2 are connected in series to achieve first-order temperature compensation of the reference voltage through complementary temperature coefficients.

[0009] The heating unit control circuit includes a first non-inverting amplifier A1, a second non-inverting amplifier A2, a subtractor A3, and resistors R2-R9 connected thereto. The positive input terminal of the first non-inverting amplifier A1 is connected to the base of the NPN transistor Q1, and the negative input terminal is connected to the power supply ground via resistor R2. The negative input terminal and the output terminal of the first non-inverting amplifier A1 are connected via resistor R3. The positive input terminal of the second non-inverting amplifier A2 is connected to the collector of the PNP transistor Q5 of the reference voltage generation circuit, and a resistor R4 is connected between the negative input terminal and the power supply ground. A resistor R5 is also connected between the negative input terminal and the output terminal of the second non-inverting amplifier A2. The positive input terminal of subtractor A3 is connected to one end of resistors R6 and R8, and the negative input terminal is connected to one end of resistor R7. The other ends of resistors R6 and R8 are connected to the output terminal of the first non-inverting amplifier A1 and the power supply ground, respectively. The other end of resistor R7 is connected to the output terminal of the second non-inverting amplifier A2. A resistor R9 is connected between the negative input terminal and the output terminal of subtractor A3. The output terminal of subtractor A3 outputs a control voltage Vctrl to the heating circuit. The first non-inverting amplifier receives the temperature-sensing voltage signal and amplifies it proportionally, outputting a first amplified voltage; the second non-inverting amplifier receives the reference voltage signal and amplifies it proportionally, outputting a second amplified voltage; the subtractor circuit performs a difference operation on the second amplified voltage and the first amplified voltage, outputting a control voltage that monotonically decreases as the temperature rises, forming a negative feedback constant temperature control logic.

[0010] The heating circuit consists of an NMOS transistor M1 and a heating resistor R10; One end of the heating resistor R10 is connected to the heating power supply V. HEAT The other end is connected to the drain of NMOS transistor M1, the gate of NMOS transistor M1 is connected to the output of subtractor A3, and the source is grounded.

[0011] This invention employs a dual-power independent power supply mode, including a first power supply VDD and a second power supply VDD. HEAT The first power supply VDD powers the precision analog circuits of the bias current generation circuit, the reference voltage generation circuit, the temperature sensor circuit, and the heating unit control circuit; the second power supply VDD... HEAT It provides independent power to the heating circuit, achieving power isolation between the high-power heating circuit and the precision signal circuit.

[0012] Compared with the prior art, the present invention has the following advantages: 1. This invention abandons the traditional on-off discrete heating control and adopts analog calculation closed-loop continuous control, which eliminates the problem of reference voltage output jitter by eliminating the large current switching action. 2. By calculating the real-time difference between the temperature signal and the reference signal, a rapid response to temperature changes is achieved, mitigating the impact of sensor acquisition lag and controlling chip temperature fluctuations within ±0.5℃, which is superior to the traditional fluctuation index of over ±1℃. 3. Relying on the multi-range adaptive adjustment of the variable resistance region, saturation region, and subthreshold region of the NMOS transistor, the heating power is continuously matched with the ambient temperature and the heat dissipation status of the chip, the steady-state heating power and heat dissipation power are dynamically balanced, and the reference voltage temperature drift can be stably controlled within 0.1ppm / ℃. 4. The dual-power isolated power supply architecture isolates high-power heating noise, has strong anti-interference capabilities, and can be adapted to a wide temperature range of 0℃~80℃, meeting the stringent application scenarios such as precision measurement, high-precision industrial control, and instrumentation. Attached Figure Description

[0013] Appendix Figure 1 A schematic diagram of the control structure of an on / off constant temperature reference source using a comparator or open-loop amplifier in the existing technology; Appendix Figure 2 This is a schematic diagram illustrating the working principle of existing on / off heating control technology. Appendix Figure 3 This is a block diagram of the overall structure of the constant temperature reference source for the improved continuous heating control of this invention. Appendix Figure 4 This is a detailed circuit diagram of the constant temperature reference voltage source heating control circuit of the present invention; Appendix Figure 5 This is the characteristic curve of the reference voltage of this invention as a function of temperature; Appendix Figure 6 The curve of the output control voltage of the heating unit control circuit of the present invention as a function of temperature is shown. Appendix Figure 7 This is the curve showing the on-resistance of the NMOS transistor as a function of the control voltage in this invention; Appendix Figure 8 This is a curve showing the change in heating power of the heating circuit of the present invention as a function of chip temperature. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0015] like Figure 3 , Figure 4As shown, the heating control circuit of the constant temperature reference voltage source provided by the present invention includes a bias current generation circuit, a reference voltage generation circuit, a temperature sensor circuit, a heating unit control circuit, and a heating circuit. The whole circuit adopts dual power supply. The first power supply VDD supplies power to the precision analog module, and the second power supply VDD... HEAT The heating module is powered independently.

[0016] The bias current generation circuit consists of NPN transistors Q1 and Q2, PNP transistors Q3 and Q4, and resistor R1. Q1 is multiplexed as a temperature sensor; the base-emitter voltage of the silicon-based transistor has a stable negative temperature coefficient of approximately -2mV / ℃, reflecting the chip's core temperature in real time. Q3 and Q4 form a current mirror, replicating the temperature-adaptive bias current generated by Q1, providing a stable operating bias for subsequent reference circuits and operational amplifiers.

[0017] The temperature sensor circuit is implemented using Q1, with the base outputting a temperature sensing voltage Vsensor. Vsensor decreases monotonically as the temperature rises and increases monotonically as the temperature falls, exhibiting good linear temperature response characteristics.

[0018] The reference voltage generation circuit consists of a PNP transistor Q5, a high-voltage reverse-biased Zener diode D1, and a forward-biased diode D2. D1 is a high-voltage Zener diode with a breakdown voltage greater than 6V, operating in avalanche breakdown mode and possessing a positive temperature coefficient; D2 is a silicon forward-biased diode with a negative temperature coefficient. The two are connected in series to achieve complementary temperature coefficients, outputting a highly stable first-order temperature-compensated reference voltage VREF, effectively suppressing reference voltage drift caused by process and temperature variations.

[0019] The heating unit control circuit consists of two non-inverting amplifiers and one subtractor. The first amplifier A1, along with resistors R2 and R3, forms the first non-inverting amplifier, which proportionally amplifies the temperature-sensor voltage Vsensor to obtain the first amplified voltage V1. The second amplifier A2, along with resistors R4 and R5, forms the second non-inverting amplifier, which proportionally amplifies the reference voltage V1. REF The voltage is proportionally amplified to obtain the second amplified voltage V2. Amplifier (subtractor) A3, resistors R6, R7, R8, and R9 constitute the subtractor circuit. The operational logic is V... CTRL =V2-V1.

[0020] The overall closed-loop negative feedback logic is as follows: chip temperature rises → Vsensor decreases → V1 decreases → V CTRL The temperature rises at a decreasing rate, and the overall temperature decreases monotonically → the gate control voltage of the NMOS transistor decreases → the on-resistance increases → the heating power decreases; as the chip temperature decreases, the control logic reverses, ultimately achieving dynamic temperature stability. This architecture completely avoids the problem of positive feedback thermal runaway, and the closed-loop control logic is stable and reliable.

[0021] The heating circuit consists of an NMOS transistor M1 and a heating resistor R10 on the upper metal layer. M1 features a large aspect ratio, low threshold voltage, and excellent conduction characteristics. This invention strictly adheres to the operating mechanism of the MOS transistor to achieve power regulation. Under low-temperature conditions, the ambient heat dissipation power is large, the VCTRL voltage is high, M1 satisfies VGS>Vth and VDS is small, it operates in the variable resistance region, the on-resistance is extremely small, the heating power is maximized, and the chip temperature is rapidly increased. As the temperature gradually increases, VCTRL continues to decrease, M1 gradually enters the saturation region, the drain-source equivalent on-resistance increases sharply, and the heating power decreases continuously and smoothly. When the chip temperature reaches the set constant temperature point, VCTRL drops to near the threshold voltage, M1 enters the subthreshold region or cutoff region, the heating power approaches zero, and the heat dissipation loss is compensated by the weak heating power to maintain a constant temperature.

[0022] The chip uses a 9mm×9mm ceramic LCCC package, and the operating constant temperature point is set at 110℃. Within the ambient temperature range of 0℃ to 80℃, the total heat dissipation power of the chip covers 210mW to 770mW. The heating circuit of this invention can achieve continuous stepless adjustment from 0 to the maximum heating power, and can accurately match the heat dissipation power changes across the entire temperature range.

[0023] Under conditions where the temperature sensor has a slight acquisition lag, the continuous power regulation mode of this invention can achieve gradual convergence of heating power, without switching oscillation and power jump. Finally, the heating power is precisely balanced with the total heat dissipation power of natural convection, thermal radiation and solid heat conduction. The steady-state temperature fluctuation can be stably controlled within ±0.5℃, and the reference voltage temperature drift is less than 0.1ppm / ℃. Example 2

[0024] A heating control circuit for a constant temperature reference voltage source, the structure of which is as follows: Figure 4 As shown, the circuit includes a bias current generation circuit, a reference voltage generation circuit, a temperature sensor circuit, a heating unit control circuit, and a heating circuit. The circuits use VDD and VDD respectively. HEAT Power supply: VDD supplies power to the reference voltage generation circuit, temperature sensor circuit, and heating unit control circuit. HEAT The heating circuit is powered; the reference voltage generation circuit consists of a forward-biased diode and a reverse-biased Zener diode to generate a first-order compensated reference voltage; the temperature sensor circuit uses a transistor as a temperature sensor, and the relationship between its base-to-emitter voltage and temperature is given; the heating unit control circuit consists of two in-phase amplifiers and a subtractor, and the output voltage is used to control the magnitude of the heating circuit's on-state current; the heating unit consists of an NMOS transistor and a resistor R composed of high-layer metal. The NMOS transistor uses a large aspect ratio, has low on-resistance, and is in the saturation region after stable operation.

[0025] The bias current generating circuit includes: NPN transistors Q1 and Q2, PNP transistors Q3 and Q4, and resistors. R 1; The reference voltage generation circuit includes: PNP transistor Q5, reverse-biased Zener diode D1, and forward-biased diode D2; The temperature sensor circuit includes: NPN transistor Q1; The heating unit control circuit includes: amplifiers A1, A2, and A3, and resistors. R 2. R 3. R 4. R 5. R 6. R 7. R 8. R 9. Resistance R 2. R 3 and amplifier A1 form a non-inverting amplifier, resistor R 4. R 5 and amplifier A2 form a non-inverting amplifier, resistor R 6. R 7. R 8. R 9 and amplifier A3 form a subtractor circuit; The heating unit includes: an NMOS transistor M1 and a resistor. R 10 .

[0026] The base-emitter voltage of transistor Q1 has a temperature coefficient:

[0027] in T For temperature, V T Thermoelectric voltage, Eg This represents the band gap energy of silicon. q The amount of electron charge. m As a process-related parameter, it can be approximated as a linear function with a slope of -2mV / ℃ within the operating temperature range. This characteristic allows transistor Q1 to be used as a simple temperature sensor. The base-to-collector voltage of Q1 is expressed as... V Sensor. The bias current generation circuit utilizes voltage. V The sensor generates a bias current, and the bias current of the reference voltage generation circuit and the amplifier is obtained by replicating this current through a current mirror.

[0028] D2 is a forward-biased diode, and the temperature coefficient of a forward-biased diode is also expressed by the formula. The temperature coefficient of a reverse-biased Zener diode undergoing avalanche breakdown is... V D2Conversely, the reference voltage is achieved by connecting a reverse-biased Zener diode and a forward-biased diode in series:

[0029] V REF The voltage versus temperature curve within the operating temperature range is as follows: Figure 5 As shown, the specific temperature coefficient depends on the device matching degree of the relevant process.

[0030] In the heating unit control circuit, a resistor R 2. R The non-inverting amplifier composed of amplifier A1 and amplifier 3 will convert the temperature sensor voltage. V The sensor was magnified to obtain V 1:

[0031] Voltage V Similarly:

[0032] Voltage V 1. V 2. Output via subtractor circuit V CTRL :

[0033] V CTRL It decreases with increasing temperature, such as Figure 6 As shown. The power of the heating unit is expressed as:

[0034] Heat dissipation is mainly achieved through natural convection, radiation, and PCB surface mount heat dissipation.

[0035] Natural convection cooling P conv Based on heat transfer coefficient h conv ,area A Temperature difference Δ T Decide:

[0036] Thermal radiation heat dissipation P rad The surface emissivity ε, the Stefan-Boltzmann constant σ, and the device temperature T S Ambient temperature T E Decide:

[0037] Solid thermal conductivity heat dissipation P cond The thermal conductivity λ and area of ​​the material A Temperature difference Δ T Heat conduction path L Decide:

[0038] The heat dissipation power increases with temperature. Assuming the chip uses a ceramic LCCC package with a package area of ​​9mm×9mm and is mounted on a PCB, the chip is heated to 110℃ and the ambient temperature of the chip is 0℃~80℃. The calculated heat dissipation power is approximately 210mW~770mW.

[0039] For a fixed heating resistance R 10 For example, 2kΩ, the on-resistance and operating region of MOSFET M1 vary with... V CTRL Changes such as Figure 7 As shown. The heating power changes with temperature as follows. Figure 8 As shown, at low temperatures V CTRL The voltage is much greater than the threshold voltage. At this time, M1 is biased in the transistor region, and the on-resistance of M1 is compared to... R 10 Negligible, as the internal temperature of the chip gradually rises to a stable operating range, V CTRL As the temperature decreases, M1 is biased into the saturation region, and its on-resistance increases rapidly. Further temperature increases will bias M1 into the subthreshold or cutoff region, where the heating power is negligible. Considering the temperature acquisition lag of the temperature sensor circuit, when the external heat dissipation power is constant, the heating circuit power will equalize with the current heat dissipation power after a gradual weakening fluctuation. Figure 8 It can be seen that, with changes in external temperature, the stable operating temperature range of the circuit is limited to within ±2℃ (depending on the sensitivity of the temperature sensor), and extremely low temperature drift can be achieved across the entire temperature range.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heating control circuit for a constant temperature reference voltage source, comprising a reference voltage generation circuit, a temperature sensor circuit, a heating unit control circuit, and a heating circuit, characterized in that... Also includes: (1) Bias current generating circuit, used to generate a stable reference bias current and provide bias current for the reference voltage generating circuit and temperature sensor circuit; The temperature sensor circuit is connected to the bias current generating circuit and is used to collect the real-time operating temperature of the reference voltage source and output a temperature sensing voltage signal that is negatively correlated with temperature. The reference voltage generating circuit is connected to the bias current generating circuit and is used to output a stable reference voltage signal after temperature compensation. (2) The two input terminals of the heating unit control circuit are respectively connected to the temperature sensor circuit and the reference voltage generation circuit. The temperature sensing voltage and the reference voltage are processed by analog calculation, and the continuously adjustable negative feedback control voltage is output to the heating circuit. The heating power of the heating power supply is continuously adjusted according to the amplitude of the control voltage, and the reference voltage source is subjected to closed-loop constant temperature heating to achieve stable control of the working voltage of the reference voltage source.

2. The heating control circuit of a constant temperature reference voltage source according to claim 1, characterized in that, The bias current generating circuit consists of NPN transistor Q1, NPN transistor Q2, PNP transistor Q3, PNP transistor Q4 and resistor R1. The bases of PNP transistors Q3 and Q4 are shorted, and their emitters are connected to the first power supply VDD. The collectors of PNP transistors Q3 and Q4 are connected to the collectors of NPN transistors Q1 and Q2, respectively. The base of NPN transistor Q2 is connected to the collector of transistor Q3. The bases of PNP transistors Q3 and Q4 are connected to the collector of Q4. Transistor Q1 serves as a temperature sensor, with its emitter grounded and its base output temperature sensing voltage Vsensor connected to the emitter of transistor Q2. The emitter of transistor Q2 is also connected to one end of resistor R1, and the other end of resistor R1 is grounded. The NPN transistor Q1 is multiplexed as the core temperature sensing device, using the temperature characteristics of the base-emitter voltage to generate the original bias current. PNP transistors Q3 and Q4 form a current mirror structure, replicating the original bias current and providing stable bias current for each functional circuit.

3. The heating control circuit of a constant temperature reference voltage source according to claim 2, characterized in that, The reference voltage generating circuit consists of a PNP transistor Q5, a reverse-biased Zener diode D1, and a forward-biased diode D2. The emitter of the PNP transistor Q5 is connected to the first power supply VDD, the base is connected to the base of the transistor Q4, and the collector outputs a reference voltage Vref which is connected to the positive terminal of the reverse-biased Zener diode D1. The negative terminal of the reverse-biased Zener diode D1 is connected to the positive terminal of the forward-biased diode D2, and the negative terminal of the forward-biased diode D2 is grounded. The reverse-biased Zener diode D1 is a high-voltage Zener diode with a breakdown voltage greater than 6V and a positive temperature coefficient. The forward-biased diode D2 has a negative temperature coefficient. The reverse-biased Zener diode D1 and the forward-biased diode D2 are connected in series to achieve first-order temperature compensation of the reference voltage through complementary temperature coefficients.

4. The heating control circuit of a constant temperature reference voltage source according to claim 3, characterized in that, The heating unit control circuit includes a first non-inverting amplifier A1, a second non-inverting amplifier A2, a subtractor A3, and resistors R2-R9 connected thereto. The positive input terminal of the first non-inverting amplifier A1 is connected to the base of the NPN transistor Q1, and the negative input terminal is connected to the power supply ground via resistor R2. The negative input terminal and the output terminal of the first non-inverting amplifier A1 are connected via resistor R3. The positive input terminal of the second non-inverting amplifier A2 is connected to the collector of the PNP transistor Q5 of the reference voltage generation circuit, and a resistor R4 is connected between the negative input terminal and the power supply ground. A resistor R5 is also connected between the negative input terminal and the output terminal of the second non-inverting amplifier A2. The positive input terminal of subtractor A3 is connected to one end of resistors R6 and R8, and the negative input terminal is connected to one end of resistor R7. The other ends of resistors R6 and R8 are connected to the output terminal of the first non-inverting amplifier A1 and the power supply ground, respectively. The other end of resistor R7 is connected to the output terminal of the second non-inverting amplifier A2. A resistor R9 is connected between the negative input terminal and the output terminal of subtractor A3. The output terminal of subtractor A3 outputs a control voltage Vctrl to the heating circuit. The first non-inverting amplifier receives the temperature-sensing voltage signal and amplifies it proportionally, outputting a first amplified voltage; the second non-inverting amplifier receives the reference voltage signal and amplifies it proportionally, outputting a second amplified voltage; the subtractor circuit performs a difference operation on the second amplified voltage and the first amplified voltage, outputting a control voltage that monotonically decreases as the temperature rises, forming a negative feedback constant temperature control logic.

5. The heating control circuit of a constant temperature reference voltage source according to claim 1 or 4, characterized in that, The heating circuit consists of an NMOS transistor M1 and a heating resistor R10; One end of the heating resistor R10 is connected to the heating power supply V. HEAT The other end is connected to the drain of NMOS transistor M1, the gate of NMOS transistor M1 is connected to the output of subtractor A3, and the source is grounded.

6. The heating control circuit of a constant temperature reference voltage source according to claim 5, characterized in that, A heating control circuit for a constant temperature reference voltage source employs a dual-power independent power supply mode, including a first power supply VDD and a second power supply VDD. HEAT ; The first power supply VDD supplies power to the precision analog circuits of the bias current generation circuit, the reference voltage generation circuit, the temperature sensor circuit, and the heating unit control circuit; the second power supply VDD HEAT It provides independent power to the heating circuit, achieving power isolation between the high-power heating circuit and the precision signal circuit.

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