Temperature sensor based on duty ratio modulation and quantification method thereof

Abstract

The invention discloses a temperature sensor based on duty ratio modulation and a quantification method thereof. The temperature sensor comprises a temperature sensing circuit, a duty ratio modulation circuit and a quantization circuit; the temperature sensing circuit generates positive correlation voltage VPTAT and negative correlation voltage VCTAT and transmits the positive correlation voltage VPTAT and the negative correlation voltage VCTAT to the duty ratio modulation circuit, the duty ratio modulation circuit converts voltage signals into duty ratio signals and transmits the duty ratio signals to the quantization circuit, the quantization circuit quantizes the period and the pulse width of the duty ratio signals, and finally digital codes of quantization results are output. In order to improve the precision of the circuit, a chopping technology, an automatic zero setting technology and a dynamic element matching technology are respectively used in the temperature-sensing front-end circuit; the quantization reading circuit adopts a mode of simultaneously quantizing the period and the pulse width to reduce the influence of the PVT, fine quantization is carried out by latching the states of an original clock and a frequency division clock, the fine quantization of the period and the pulse width multiplexes the same circuit, and the clock with the lowest frequency is coarsely quantized through two counters, so that the quantization precision is effectively improved, and the power consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a temperature sensor based on duty cycle modulation and a quantization method thereof. Background Art

[0002] Temperature is a widely measured environmental parameter in the physical world, mainly due to the fact that almost all physical, chemical, mechanical or biological systems have a certain degree of temperature dependence. Therefore, temperature sensors are widely used in measuring instruments, automotive industry, food and medical fields. Especially since the outbreak of the new crown epidemic, various types of non-contact infrared thermometers can be seen everywhere, becoming an indispensable tool in epidemic prevention and control.

[0003] In addition to traditional temperature measurement needs, temperature sensors are also constantly opening up new application scenarios in emerging markets. For example, in various SoC (system on chip) chips, high-speed interfaces, real-time clocks and other circuits that are highly sensitive to temperature changes require the use of high-speed, high-precision temperature sensors to collect temperature information in real time and dynamically adjust control signals through feedback loops. In addition, as the performance of high-end processors continues to improve, their heat dissipation problems are becoming increasingly prominent. By arranging a large-scale array of temperature sensors inside the processor, the temperature of different processor cores can be tracked in real time, providing data support for multi-core load scheduling and voltage and frequency adjustment.

[0004] Traditional temperature sensors are usually composed of discrete components such as thermistors or thermocouples. Their advantages are wide temperature measurement range, high accuracy, and good process stability. However, as emerging application scenarios have increasing requirements for size, power consumption, and integration, discrete components are gradually unable to meet the needs. Therefore, integrated temperature sensors based on CMOS technology have become a highly competitive choice. Such sensors are usually called CMOS smart temperature sensors.

[0005] In new application scenarios, CMOS smart temperature sensors show significant advantages: first, they can directly output digital signals without the need for additional analog-to-digital converters, thereby reducing system complexity and component count, reducing costs and improving system integration; second, their on-chip temperature sensing devices can more accurately monitor the temperature inside the chip, which helps to optimize complex on-chip control in combination with actual temperature information. At the same time, refined temperature monitoring also lays the foundation for the further development of multi-core scheduling and dynamic control algorithms; finally, by integrating the readout circuit and the temperature sensing node in the same chip, designers can flexibly choose between circuit area, measurement accuracy and power consumption according to specific needs, thereby achieving more innovative architecture design. These characteristics make CMOS smart temperature sensors more competitive and have greater development potential in emerging applications.

[0006] In temperature sensor applications, accurate measurement and signal transmission are critical to performance. As a common signal processing method, time modulation circuit can convert analog signals into time domain signals to reduce the influence of noise during analog transmission. However, traditional time modulation methods have problems such as insufficient accuracy and susceptibility to temperature drift during the quantization process. Therefore, it is of great significance to design a method that can optimize the quantization process and improve anti-interference ability. Summary of the invention

[0007] Technical problem: The present invention aims to provide a temperature sensor based on duty cycle modulation and a quantization method thereof, so as to solve the problem of insufficient accuracy of the time modulation circuit in the quantization process in the prior art and improve the reliability and stability of the temperature sensor signal processing.

[0008] Technical solution: To achieve the above purpose, the present invention adopts a temperature sensor technical solution based on duty cycle modulation:

[0009] The temperature sensor comprises a temperature sensing circuit, a duty cycle modulation circuit and a quantization circuit; the temperature sensing circuit generates a positive correlation voltage V PTAT and negatively correlated voltage V CTAT The duty cycle modulation circuit converts the voltage signal into a duty cycle signal and transmits it to the quantization circuit. The quantization circuit quantizes the period and pulse width of the duty cycle signal respectively and finally outputs the digital code of the quantization result.

[0010] The temperature sensing circuit generates voltages that are positively correlated and negatively correlated with temperature through a bandgap reference, and is connected to the comparator input end of the duty cycle modulation circuit through a switch.

[0011] The duty cycle modulation circuit includes a main comparator and a self-driven clock generation circuit. The main comparator is used to generate a pulse width modulation PWM signal that varies with temperature. The PWM signal is used to generate an adaptive clock and in turn control the working timing of the comparator.

[0012] The quantization circuit includes fine quantization, coarse quantization and control logic; fine quantization is performed by latching the start and end states of the frequency-divided clock, and one frequency divider is used to replace two counters, thereby reducing power consumption; fine quantization also latches the reference clock at the same time, thereby improving the quantization accuracy of one bit, and the frequency-divided clock can also be used as the chopping clock of the operational amplifier; the main structure of coarse quantization is two counters, and the lowest frequency clock is used to quantize the period and pulse width respectively; the control logic circuit first uses the PWM signal to generate a state machine, and then quantizes the period and pulse width respectively in different states and clears the state.

[0013] A quantization method for a temperature sensor based on duty cycle modulation of the present invention is: converting the sensor analog signal of the temperature sensing circuit into a duty cycle signal PWM through the time modulation circuit of the duty cycle modulation circuit, and quantizing the period and pulse width signals respectively through the quantization circuit to reduce the influence of the quantization result on the power supply voltage and the process angle. Considering that there is an inherent minimum resolution error in the quantization process, starting the quantization twice at the same time will reduce the influence of the inherent error and further improve the accuracy of the quantization result.

[0014] The temperature sensing circuit is responsible for converting the temperature signal into a voltage quantity, and adopts the principle of bandgap reference; ΔV BE The PTAT voltage is positively correlated with temperature. At a fixed temperature, its magnitude is independent of the bias current and the saturation current of the transistor, and only depends on the current density ratio of the two transistors. When the circuit can generate a PTAT voltage ΔV at the same time BE The CTAT voltage V is negatively correlated with the temperature BE When the two are combined in proportion, a reference voltage that is approximately independent of temperature is obtained, and a current that is positively correlated with temperature is also generated. In order to improve the accuracy, the operational amplifier in the temperature sensing circuit is a chopper operational amplifier, and the current mirror and transistor BJT are connected using dynamic component matching.

[0015] The duty cycle modulation circuit is responsible for converting the voltage signal into a duty cycle signal. The generated duty cycle signal generates a dynamic element matching DEM switching signal and a period reset RST signal through a self-driven clock generation circuit on the one hand, and provides a signal to be quantized for the quantization circuit on the other hand. The circuit has two alternating working phases Φ 1 and Φ 2 The voltage-duty cycle converter composed of a comparator converts the temperature-related voltage signal into a temperature-related high and low level duration signal; at the beginning of each working phase, the voltage V on the charging capacitor C C will be reset to 0, and then the charging current I C The charging capacitor C is charged.

[0016] The quantization circuit generates a state machine by dividing the PWM signal by two, and completes a complete quantization process, i.e., a temperature measurement process, every two PWM cycles; in the first PWM cycle, coarse and fine quantization of the PWM period and pulse width is performed, and in the second PWM cycle, the quantization data is latched and the quantization circuit is self-reset; the clock obtained by dividing the initial clock is not only used for coarse and fine quantization, but also serves as the chopping clock of the operational amplifier in the temperature sensing circuit; the frequency divider and counter in the quantization circuit are both 7-bit, 1 frequency divider is used for fine quantization, 2 counters are used for coarse quantization, and the latching of the initial clock state is equivalent to quantizing the period and pulse width of the PWM signal by 15, and a D flip-flop with a zeroing terminal and an enabling terminal is used in the quantization circuit to complete the function of quantization only for a period of time.

[0017] The temperature sensor has a reference clock frequency of 25MHz. When the global zeroing signal REST is at a low level, all D flip-flops do not work, the quantization circuit stops working, and because the frequency divider no longer works, the chopping clock is no longer generated, but the temperature sensing circuit and the duty cycle modulation circuit are still working; when the global zeroing signal REST is at a high level, the system works normally and outputs a quantization result every two PWM cycles.

[0018] Beneficial effects: The present invention designs a temperature sensor based on duty cycle modulation and its quantization method based on a double quantization model. Compared with the traditional method, the present invention adopts a method of simultaneously quantizing period and pulse width to reduce the influence of PVT, and performs fine quantization by latching the states of the original clock and the divided clock. The fine quantization of period and pulse width reuses the same circuit, and the lowest frequency clock is coarsely quantized through two counters, which improves quantization accuracy, reduces system power consumption, and maintains high measurement consistency and reliability under various temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the overall block diagram of the temperature sensor of the present invention;

[0020] Figure 2 A circuit diagram of a temperature sensing circuit used in the present invention;

[0021] Figure 3 A block diagram of a duty cycle modulation circuit used in the present invention;

[0022] Figure 4 The block diagram of the quantization circuit of the present invention is shown below;

[0023] Figure 5 The present invention is a D flip-flop circuit diagram with zero reset and enable terminals;

[0024] Figure 6 It is a timing diagram of the quantization circuit of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] The present invention is based on BJT temperature sensing and duty cycle modulation, and specifically designs a temperature sensor based on duty cycle modulation and a quantization method thereof. Based on the bandgap reference principle, the temperature sensing front-end circuit generates a voltage that is positively correlated (PTAT) and negatively correlated (CTAT) with the temperature. The voltage is converted into a periodic duty cycle signal by a duty cycle modulator composed of a comparator. In the present invention, in order to improve the circuit accuracy, the temperature sensing front-end circuit uses chopping technology, automatic zeroing technology and dynamic component matching technology respectively; the quantization reading circuit uses a method of simultaneously quantizing the period and pulse width to reduce the influence of the process angle, power supply voltage and stability (PVT), and fine quantization is performed by latching the state of the original clock and the divided clock. The fine quantization of the period and pulse width reuses the same circuit, and the lowest frequency clock is coarsely quantized by two counters, which effectively improves the quantization accuracy and reduces power consumption.

[0027] The temperature sensor comprises a temperature sensing circuit, a duty cycle modulation circuit and a quantization circuit; the temperature sensing circuit generates a positive correlation voltage V PTAT and negatively correlated voltage V CTAT The temperature sensing circuit generates a voltage that is positively and negatively correlated with the temperature through a bandgap reference, and is connected to the comparator input of the duty cycle modulation circuit through a switch. The duty cycle modulation circuit includes a main comparator and a self-driven clock generation circuit. The main comparator is used to generate a PWM signal that changes with temperature. The PWM signal is used to generate an adaptive clock and in turn control the working timing of the comparator. The quantization circuit includes fine quantization, coarse quantization and control logic; fine quantization is performed by latching the start and end states of the frequency-divided clock, and one frequency divider is used to replace two counters, thereby reducing power consumption; fine quantization also latches the reference clock at the same time, thereby improving the quantization accuracy of one bit, and the frequency-divided clock can also be used as the chopping clock of the operational amplifier; the main structure of coarse quantization is two counters, and the lowest frequency clock is used to quantize the period and pulse width respectively; the control logic circuit first uses the PWM signal to generate a state machine, and then quantizes the period and pulse width respectively in different states and clears the state.

[0028] like Figure 1 The figure shows the overall block diagram of the temperature sensor, which includes the temperature sensing circuit, duty cycle modulation circuit and quantization circuit. The frequency divider can be regarded as a part of the quantization circuit. The temperature sensing circuit is used to generate V PTAT and V CTATThe duty cycle modulation circuit can generate a duty cycle signal that is linearly related to the temperature, and the quantization circuit is used to quantize the period and duty cycle signals respectively, and output the digital code of the quantization result, and the output result is handed over to the subsequent system for data processing. The present invention only needs two input signals, one is the global zeroing signal, and the other is the reference clock signal.

[0029] like Figure 3 The figure shows the block diagram of the duty cycle modulation circuit, including the main circuit and the self-driven clock generation circuit. For the self-driven clock generation circuit; the inverter generates Φ 1 and Φ 2 , the D flip-flop and the NOR gate generate the dynamic element matching (DEM) switching signal, and the XOR gate and the delay line generate the capacitor cycle reset signal RST. For the main part of the duty cycle modulation circuit, in the working phase Φ 1 The first switch SW 1 and the third switch SW 3 The second switch SW is turned on. 2 and the fourth switch SW 4 Shutdown, voltage V negatively correlated with temperature CTAT and the voltage V on the charging capacitor C are connected to nodes A and B respectively. When V C <V CTAT When V C Gradually rises, when V C >V CTAT When the comparator output turns to low level, the circuit enters the working phase Φ 2 In the working phase Φ 2 The first switch SW 1 and the third switch SW 3 Turn off, the second switch SW 2 and the fourth switch SW 4 Turn-on, voltage V positively correlated with temperature PTAT Connected to node B, the capacitor voltage V C connected to node A, so when V C <V PTAT When the voltage V on the charging capacitor is C The rise makes V C >V PTAT When the comparator output turns high again, the circuit re-enters the working phase Φ 1 , and enters a new duty cycle modulation cycle.

[0030] like Figure 4The block diagram of the quantization circuit of the present invention is shown. Because the clock frequency requirement is not so high, a phase-locked loop / delay phase-locked loop (PLL / DLL) is not used for fine quantization. Instead, an external input clock is directly used to perform fine quantization by latching the divided-frequency clock state. This method of multiplexing the divided-frequency clock can reduce power consumption. First, the chopping clock no longer needs a separate frequency divider design. Secondly, the fine quantization of the period and pulse width can share a frequency divider, which can theoretically halve the power consumption. In addition, the scheme can increase the quantization accuracy by one bit by latching the state of CK (reference clock). The scheme needs to quantize the period and pulse width signals at the same time, so delay matching is particularly important. Designing a delay circuit with adjustable delay can solve this problem. Coarse quantization requires counting within the periodic pulse time, so it is necessary to design a low-power D flip-flop with zeroing and enable terminals, such as Figure 5 shown.

[0031] A quantization method for a temperature sensor based on duty cycle modulation of the present invention converts the sensor analog signal of a temperature sensing circuit into a duty cycle signal PWM through a time modulation circuit of a duty cycle modulation circuit, and quantizes the period and pulse width signals respectively through a quantization circuit to reduce the influence of the power supply voltage and the process angle on the quantization result. Considering that there is an inherent minimum resolution error in the quantization process, starting the quantization twice at the same time will reduce the influence of the inherent error and further improve the accuracy of the quantization result.

[0032] The temperature sensing circuit is responsible for converting the temperature signal into a voltage quantity, and adopts the principle of a bandgap reference; the voltage PTAT is positively correlated with the temperature. At a fixed temperature, its size is independent of the bias current and the saturation current of the transistor, and only depends on the current density ratio of the two transistors. When the circuit can simultaneously generate the PTAT voltage and the CTAT voltage negatively correlated with the temperature, the two are combined in proportion to obtain a reference voltage that is approximately independent of the temperature, and a current that is positively correlated with the temperature is also generated; in order to improve the accuracy, the operational amplifier in the temperature sensing circuit is a chopper operational amplifier, and the current mirror and the transistor BJT are connected using dynamic element matching.

[0033] The duty cycle modulation circuit is responsible for converting the voltage signal into a duty cycle signal. The generated duty cycle signal, on the one hand, generates a dynamic element matching DEM switching signal and a period reset RST signal through a self-driven clock generation circuit, and on the other hand, provides a signal to be quantized for the quantization circuit; the circuit has two alternating working phases, and a voltage-duty cycle converter composed of a comparator converts a temperature-related voltage signal into a temperature-related high and low level duration signal; at the beginning of each working phase, the voltage on the charging capacitor C will be reset to 0, and then the charging capacitor C will be charged by the charging current.

[0034] The quantization circuit generates a state machine by dividing the PWM signal by two, and completes a complete quantization process, i.e., a temperature measurement process, every two PWM cycles; in the first PWM cycle, coarse and fine quantization of the PWM period and pulse width is performed, and in the second PWM cycle, the quantization data is latched and the quantization circuit is self-reset; the clock obtained by dividing the initial clock is not only used for coarse and fine quantization, but also serves as the chopping clock of the operational amplifier in the temperature sensing circuit; the frequency divider and counter in the quantization circuit are both 7-bit, 1 frequency divider is used for fine quantization, 2 counters are used for coarse quantization, and the latching of the initial clock state is equivalent to quantizing the period and pulse width of the PWM signal by 15, and a D flip-flop with a zeroing terminal and an enabling terminal is used in the quantization circuit to complete the function of quantization only for a period of time.

[0035] The temperature sensor has a reference clock frequency of 25MHz. When the global zeroing signal REST is at a low level, all D flip-flops do not work, the quantization circuit stops working, and because the frequency divider no longer works, the chopping clock is no longer generated, but the temperature sensing circuit and the duty cycle modulation circuit are still working; when the global zeroing signal REST is at a high level, the system works normally and outputs a quantization result every two PWM cycles.

[0036] Figure 6 This is the timing diagram of the quantization circuit. The entire system timing can be divided into 5 stages. The system's working timing is:

[0037] 1) When the system is just powered on, the global signal REST resets the entire system and sets the initial state of all DFF flip-flops to 0;

[0038] 2) When REST is at a high level, the system is quantized normally. The PWM signal is quantized once every two cycles. Delay matching is performed so that the cycle quantization (T) and pulse width quantization (H) start at the same time. State 1 performs pulse width quantization, and pulse width quantization ends when the falling edge of the H signal arrives.

[0039] 3) State 1 and state 2 perform cycle quantization, and cycle quantization ends when the falling edge of T arrives;

[0040] 4) The second cycle of PWM is divided into state 3 and state 4, and the quantization result can be output during state 3;

[0041] 5) State 4 is set to zero (DN) and waits for the start of the next quantization;

[0042] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A temperature sensor based on duty cycle modulation, characterized in that: The temperature sensor comprises a temperature sensing circuit, a duty cycle modulation circuit and a quantization circuit; the temperature sensing circuit generates a positive correlation voltage V PTAT and negatively correlated voltage V CTAT The duty cycle modulation circuit converts the voltage signal into a duty cycle signal and transmits it to the quantization circuit. The quantization circuit quantizes the period and pulse width of the duty cycle signal respectively and finally outputs the digital code of the quantization result.

2. A temperature sensor based on duty cycle modulation according to claim 1, characterized in that: The temperature sensing circuit generates voltages that are positively correlated and negatively correlated with temperature through a bandgap reference, and is connected to the comparator input end of the duty cycle modulation circuit through a switch.

3. A temperature sensor based on duty cycle modulation according to claim 1, characterized in that: The duty cycle modulation circuit includes a main comparator and a self-driven clock generation circuit. The main comparator is used to generate a pulse width modulation PWM signal that varies with temperature. The PWM signal is used to generate an adaptive clock and in turn control the working timing of the comparator.

4. A temperature sensor based on duty cycle modulation according to claim 1, characterized in that: The quantization circuit includes fine quantization, coarse quantization and control logic; Fine quantization is performed by latching the start and end states of the divided clock, using one divider instead of two counters to reduce power consumption; fine quantization also latches the reference clock at the same time, improving the quantization accuracy by one bit, and the divided clock can also be used as the chopping clock of the op amp; the main structure of coarse quantization is two counters, which use the lowest frequency clock to quantize the period and pulse width respectively; the control logic circuit first uses the PWM signal to generate a state machine, and then quantizes the period and pulse width and clears the state in different states.

5. A quantization method for a temperature sensor based on duty cycle modulation as claimed in claim 1, characterized in that: This method converts the sensor analog signal of the temperature sensing circuit into a duty cycle signal PWM through the time modulation circuit of the duty cycle modulation circuit, and quantizes the period and pulse width signals respectively through the quantization circuit to reduce the influence of the quantization result on the power supply voltage and the process angle. Considering that there is an inherent minimum resolution error in the quantization process, starting the two quantizations at the same time will reduce the influence of the inherent error and further improve the accuracy of the quantization result.

6. The quantization method of a temperature sensor based on duty cycle modulation according to claim 5, characterized in that: The temperature sensing circuit is responsible for converting the temperature signal into a voltage quantity, and adopts the principle of bandgap reference; ΔV BE The PTAT voltage is positively correlated with temperature. At a fixed temperature, its magnitude is independent of the bias current and the saturation current of the transistor, and only depends on the current density ratio of the two transistors. When the circuit can generate a PTAT voltage ΔV at the same time BE The CTAT voltage V is negatively correlated with the temperature BE When the two are combined in proportion, a reference voltage that is approximately independent of temperature is obtained, and a current that is positively correlated with temperature is also generated. In order to improve the accuracy, the operational amplifier in the temperature sensing circuit is a chopper operational amplifier, and the current mirror and transistor BJT are connected using dynamic component matching.

7. The quantization method of a temperature sensor based on duty cycle modulation according to claim 5, characterized in that: The duty cycle modulation circuit is responsible for converting the voltage signal into a duty cycle signal. The generated duty cycle signal generates a dynamic element matching DEM switching signal and a period reset RST signal through a self-driven clock generation circuit on the one hand, and provides a signal to be quantized for the quantization circuit on the other hand. The circuit has two alternating working phases Φ1 and Φ2. The voltage-duty cycle converter composed of a comparator converts the temperature-related voltage signal into a high-low level duration signal related to the temperature. At the beginning of each working phase, the voltage V on the charging capacitor C C will be reset to 0, and then the charging current I C The charging capacitor C is charged.

8. The quantization method of a temperature sensor based on duty cycle modulation according to claim 5, characterized in that: The quantization circuit generates a state machine by dividing the PWM signal by two, and completes a complete quantization process, i.e., a temperature measurement process, every two PWM cycles; in the first PWM cycle, coarse and fine quantization of the PWM period and pulse width is performed, and in the second PWM cycle, the quantization data is latched and the quantization circuit is self-reset; the clock obtained by dividing the initial clock is not only used for coarse and fine quantization, but also serves as the chopping clock of the operational amplifier in the temperature sensing circuit; the frequency divider and counter in the quantization circuit are both 7-bit, 1 frequency divider is used for fine quantization, 2 counters are used for coarse quantization, and the latching of the initial clock state is equivalent to quantizing the period and pulse width of the PWM signal by 15, and a D flip-flop with a zeroing terminal and an enabling terminal is used in the quantization circuit to complete the function of quantization only for a period of time.

9. The quantization method of a temperature sensor based on duty cycle modulation according to claim 5, characterized in that: The temperature sensor has a reference clock frequency of 25MHz. When the global reset signal REST is at a low level, all D flip-flops do not work, the quantization circuit stops working, and because the frequency divider no longer works, the chopping clock is no longer generated, but the temperature sensing circuit and the duty cycle modulation circuit are still working; When the global reset signal REST is at a high level, the system works normally and outputs a quantization result every two PWM cycles.

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