Starting circuit of wide-voltage-domain and high-precision analog temperature sensor

Abstract

The invention discloses a starting circuit of a wide-voltage-domain and high-precision analog temperature sensor. The starting circuit comprises a temperature sensor main body structure, a starting module and an external load. The main body structure of the temperature sensor is composed of triodes, generates a voltage in direct proportion to the temperature and provides the voltage to an external load. The starting module is composed of a capacitor, so that the circuit is separated from a zero degeneracy point state, and extra current is not consumed after the circuit is started; the two ends of the external load apply PTAT voltage to the temperature sensor, and the PTAT voltage is converted into PTAT current. The circuit is low in power consumption, current passes through the two ends of the capacitor only in the starting process, the current on the capacitor is zero after normal work, and normal starting work of the circuit can be guaranteed under lower working current.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and particularly relates to a start-up circuit for a wide voltage range and high-precision analog temperature sensor. Background Art

[0002] Analog temperature sensors mainly accurately characterize the change of current with temperature based on the temperature characteristics of PTAT current. With technological progress and the increasing complexity of electronic systems, the requirements for temperature sensors are getting higher and higher. It is necessary to design a temperature sensor circuit with a wider voltage range and lower operating current for signal acquisition to meet the temperature acquisition requirements of users in low-power and wide-voltage-range application scenarios.

[0003] Wide voltage range and high-precision analog temperature sensors mainly use triodes to construct circuits to generate the PTAT current required for temperature measurement. This circuit generally has two degeneracy points. At one degeneracy point, the triode current is zero, and at the other degeneracy point, the triode generates PTAT current. To prevent the circuit from stabilizing in the zero-current state and being unable to work properly after power-on, the temperature sensor requires a start-up circuit to get out of the zero degeneracy point.

[0004] Traditional start-up circuits are as Figure 1 shown. When the temperature sensor is powered on, transistors T1 and T2 conduct, pulling up the bases of transistors Q1, Q2, and Q3, so that a current is generated in the branch where transistors Q3 and Q6 are located. Transistors Q4 and Q5 copy the current of Q6 and, together with transistor T1, cause the self-biased structure composed of transistors Q1 to Q6 to get out of the zero degeneracy point state. Finally, PTAT currents flow through transistors Q1, Q3, and Q7 and flow into the external resistor R1 to achieve the temperature measurement function. However, the disadvantage of this kind of start-up circuit is that when the circuit enters the normal working state, transistors T1 and T2 cannot be turned off and still consume current all the time, making it difficult to reduce power consumption and restricting the performance of the analog temperature sensor. Summary of the Invention

[0005] The purpose of the present invention is to provide a start-up circuit for a wide voltage range and high-precision analog temperature sensor to solve the problems in the background art.

[0006] To solve the above technical problems, the present invention provides a start-up circuit for a wide voltage range and high-precision analog temperature sensor, including:

[0007] A temperature sensor main body structure, composed of triodes, which generates a voltage proportional to temperature and supplies it to an external load;

[0008] A start-up module, composed of capacitors, which makes the circuit get out of the zero degeneracy point state and does not consume extra current after the circuit starts up;

[0009] An external load that applies a PTAT voltage across its two ends and converts it into a PTAT current.

[0010] In one embodiment, the temperature sensor main structure includes NPN transistors with an area proportional relationship;

[0011] The bases of the NPN transistors with an area proportional relationship are connected. The emitter of the NPN transistor with a relatively larger area is connected to the first end of the external load, and the emitter of the NPN transistor with a relatively smaller area is connected to the second end of the external load;

[0012] The NPN transistors with an area proportional relationship are combined with PNP transistors with an area proportional relationship to form a current mirror, constituting a self-biased structure with two degeneracy points, and forming a positive temperature coefficient voltage between the emitters of the NPN transistors.

[0013] In one embodiment, the temperature sensor main structure includes NPN transistors Q1 to Q3 and PNP transistors Q4 to Q7;

[0014] The base of NPN transistor Q1 is connected to the collector of NPN transistor Q1, the base of NPN transistor Q2, and the collector of PNP transistor Q5 simultaneously;

[0015] The emitter of NPN transistor Q1 is connected to the emitter of NPN transistor Q3 and the collector of PNP transistor Q7 simultaneously;

[0016] The base of NPN transistor Q3 is connected to the collector of NPN transistor Q2 and the collector of PNP transistor Q4 simultaneously;

[0017] The emitter of PNP transistor Q4 is connected to the power supply, the emitters of PNP transistors Q5, Q6, and Q7 simultaneously;

[0018] The base of PNP transistor Q6 is connected to the collector of NPN transistor Q3, the bases of PNP transistors Q4, Q5, Q6, and Q7, and the collector of PNP transistor Q6 simultaneously.

[0019] In one embodiment, the startup module is composed of a capacitor C1. One end of the capacitor C1 is connected to the power supply, and the other end is connected to a node in the temperature sensor main structure that is initially zero.

[0020] In one embodiment, the first end of the capacitor C1 is connected to the power supply, the emitters of PNP transistors Q4, Q5, Q6, and Q7 simultaneously, and the second end is connected to the collector of NPN transistor Q2, the base of NPN transistor Q3, and the collector of PNP transistor Q4 simultaneously.

[0021] In one embodiment, the external load is composed of a resistor R1. The first end of the resistor R1 is connected to the emitter of the NPN transistor Q1, the emitter of the NPN transistor Q3, and the collector of the PNP transistor Q7 at the same time, and the second end is connected to the emitter of the NPN transistor Q2.

[0022] A start-up circuit for a wide voltage range and high-precision analog temperature sensor provided by the present invention has lower power consumption compared with the traditional start-up method using JFET transistors. There is only current flowing through the capacitor during the start-up process, and the current on the capacitor is zero after normal operation, which can ensure the normal start-up and operation of the circuit at a lower working current. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of a traditional start-up circuit for a wide voltage range and high-precision analog temperature sensor based on JFET transistors.

[0024] Figure 2 is a schematic diagram of a start-up circuit for a wide voltage range and high-precision analog temperature sensor provided by the present invention.

[0025] Figure 3 is a schematic diagram of the current relationship curve of currents I1 and I2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following further details a start-up circuit for a wide voltage range and high-precision analog temperature sensor proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise scales, only for the purpose of facilitating and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0027] The present invention provides a start-up circuit for a wide voltage range and high-precision analog temperature sensor, and its structure is as Figure 2 shown, including a temperature sensor main structure, a start-up module, and an external load. The temperature sensor main structure is composed of a triode, generating a voltage proportional to the temperature and providing it to the external load; the start-up module is composed of a capacitor, enabling the circuit to break away from the zero degeneracy point state and not consuming additional current after the circuit starts up; the two ends of the external load apply a PTAT voltage to the temperature sensor and convert it into a PTAT current.

[0028] The main structure of the temperature sensor includes NPN transistors Q1 to Q3 and PNP transistors Q4 to Q7. The base of NPN transistor Q1 is connected to the collector of NPN transistor Q1, the base of NPN transistor Q2, and the collector of PNP transistor Q5 simultaneously. The emitter of NPN transistor Q1 is connected to the emitter of NPN transistor Q3 and the collector of PNP transistor Q7 simultaneously. The base of NPN transistor Q3 is connected to the collector of NPN transistor Q2 and the collector of PNP transistor Q4 simultaneously. The emitter of PNP transistor Q4 is connected to the power supply, the emitter of PNP transistor Q5, the emitter of PNP transistor Q6, and the emitter of PNP transistor Q7 simultaneously. The base of PNP transistor Q6 is connected to the collector of NPN transistor Q3, the base of PNP transistor Q4, the base of PNP transistor Q5, the collector of PNP transistor Q6, and the base of PNP transistor Q7 simultaneously.

[0029] The starting module is composed of a capacitor C1. The first end of the capacitor C1 is connected to the power supply, the emitter of PNP transistor Q4, the emitter of PNP transistor Q5, the emitter of PNP transistor Q6, and the emitter of PNP transistor Q7 simultaneously. The second end of the capacitor C1 is connected to the collector of NPN transistor Q2, the base of NPN transistor Q3, and the collector of PNP transistor Q4 simultaneously.

[0030] The external load is composed of a resistor R1. The first end of the resistor R1 is connected to the emitter of NPN transistor Q1, the emitter of NPN transistor Q3, and the collector of PNP transistor Q7 simultaneously. The second end of the resistor R1 is connected to the emitter of NPN transistor Q2.

[0031] The specific working principle of the present invention is as follows: The areas of NPN transistors Q1 and Q2 are in proportion and form a current mirror with a negative feedback resistor together with the external resistor R1. The area ratio relationship of PNP transistors Q4, Q5, Q6, and Q7 is 1:x5:x6:x7, which also forms a current mirror, where x is determined according to the specific circuit design. When the circuit is working normally, NPN transistors Q1, Q2, Q3 and PNP transistors Q4, Q5, Q6 form a self - biasing structure. If the current in the branch where NPN transistor Q1 and PNP transistor Q5 are located is defined as I1, and the current in the branch where NPN transistor Q2 and PNP transistor Q4 are located is defined as I2, then the branch currents of NPN transistors Q1 and Q2 are required to satisfy:

[0032] V T ln(I1 / I S1 )+(x5 + x6 + x7)I1R1 / x5 = V T ln(I2 / I S2 )

[0033] Among them, V T is the thermal voltage, I S1 is the saturation current of NPN transistor Q1, I S2is the saturation current of NPN tube Q2. It can be seen that the negative feedback resistor R1 makes a nonlinear relationship between I1 and I2. The limiting requirements of PNP tubes Q4 and Q5 on branch current are:

[0034] I1 / x5=I2

[0035] Figure 3 The current relationship curve of I1 and I2 that meets the above requirements is given. It can be seen that the two degenerate points of the current relationship curve both meet the requirement of I1=I2. Among them, the degenerate point of I1=I2=0 is not expected by the circuit, and the circuit needs to be started to make the temperature sensor out of this state.

[0036] When the temperature sensor is powered on, capacitor C1 transfers the power supply voltage to the base of NPN tube Q3, causing it to be pulled up instantly and NPN tube Q3 to turn on. The current in the branch where NPN tube Q3 and PNP tube Q6 are located causes a voltage to be generated between the base and emitter of PNP tube Q6, pulling down the bases of PNP tubes Q4, Q5, Q6, and Q7. Similarly, the current in the branch where NPN tube Q1 and PNP tube Q5 are located causes a voltage to be generated between the base and emitter of NPN tube Q1, pulling up the bases of NPN tubes Q1 and Q2. The self-biased structure composed of NPN tubes Q1, Q2, Q3 and PNP tubes Q4, Q5, and Q6 breaks away from the zero degeneracy point and ultimately outputs a stable current. The voltage ΔV applied across the external resistor R1 BE It is the PTAT voltage, which is converted into the PTAT current by the resistor and used to calculate the measured temperature. After the circuit is stable, the capacitor C1 has a stable DC voltage drop across its two ends, and no static current flows through it.

[0037] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A startup circuit for a wide voltage range, high-precision analog temperature sensor, characterized in that: include: The main structure of the temperature sensor is composed of a triode, which generates a voltage proportional to the temperature and provides it to the external load; A startup module, composed of a capacitor, which allows the circuit to leave the zero degeneracy point state and does not consume additional current after the circuit is started; The external load has the PTAT voltage applied by the temperature sensor across its terminals and converts it into a PTAT current.

2. The startup circuit of the wide voltage range, high-precision analog temperature sensor according to claim 1, characterized in that: The main structure of the temperature sensor includes NPN tubes with proportional areas; The base electrodes of the NPN tubes with proportional areas are connected, the emitter electrode of the NPN tube with a relatively large area is connected to the first end of the external load, and the emitter electrode of the NPN tube with a relatively small area is connected to the second end of the external load; The NPN tubes with proportional areas are combined with the PNP tubes with proportional areas to form a current mirror, forming a self-biased structure with two degenerate points and forming a positive temperature coefficient voltage between the emitters of the NPN tubes.

3. The startup circuit of the wide voltage range, high-precision analog temperature sensor according to claim 1, characterized in that: The main structure of the temperature sensor includes NPN tubes Q1-Q3 and PNP tubes Q4-Q7; The base of the NPN tube Q1 is connected to the collector of the NPN tube Q1, the base of the NPN tube Q2, and the collector of the PNP tube Q5 at the same time; The emitter of NPN tube Q1 is connected to the emitter of NPN tube Q3 and the collector of PNP tube Q7 at the same time; The base of NPN tube Q3 is connected to the collector of NPN tube Q2 and the collector of PNP tube Q4 at the same time; The emitter of PNP tube Q4 is connected to the power supply, the emitter of PNP tube Q5, the emitter of PNP tube Q6, and the emitter of PNP tube Q7 at the same time; The base of the PNP tube Q6 is simultaneously connected to the collector of the NPN tube Q3, the base of the PNP tube Q4, the base of the PNP tube Q5, the collector of the PNP tube Q6, and the base of the PNP tube Q7.

4. The startup circuit of the wide voltage range, high-precision analog temperature sensor according to claim 1, characterized in that: The startup module is composed of a capacitor C1, one end of the capacitor C1 is connected to a power source, and the other end is connected to a node in the main structure of the temperature sensor whose initial state is zero.

5. The startup circuit of the wide voltage range, high-precision analog temperature sensor according to claim 4, characterized in that: The first end of the capacitor C1 is simultaneously connected to the power supply, the emitter of the PNP tube Q4, the emitter of the PNP tube Q5, the emitter of the PNP tube Q6, and the emitter of the PNP tube Q7, and the second end is simultaneously connected to the collector of the NPN tube Q2, the base of the NPN tube Q3, and the collector of the PNP tube Q4.

6. The startup circuit of the wide voltage range, high-precision analog temperature sensor according to claim 3, characterized in that: The external load is composed of a resistor R1 , a first end of which is simultaneously connected to the emitter of the NPN tube Q1 , the emitter of the NPN tube Q3 , and the collector of the PNP tube Q7 , and a second end of which is connected to the emitter of the NPN tube Q2 .

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