Temperature Sensing Circuit

Abstract

A temperature sensing circuit comprises: a bandgap voltage generating circuit, a current mirror branch, a variable resistor, a comparison circuit, a control circuit and a temperature judgment circuit. The bandgap voltage generating circuit generates a bandgap voltage having a first temperature coefficient. The current mirror branch mirrors a mirror current having a second temperature coefficient from the bandgap voltage generating circuit. The variable resistor comprises a first end electrically coupled to the current mirror branch to receive the mirror current and generate a variable voltage at the first end. The comparison circuit compares the bandgap voltage and the variable voltage to generate a comparison result. The control circuit generates a control signal according to the comparison result to continuously adjust the resistance value of the variable resistor, and outputs a signal value when the signal value of the control signal makes the variable voltage substantially equal to the bandgap voltage. The temperature judgment circuit generates a temperature value according to the signal value.

Description

Technical Field

[0001] The present invention relates to a temperature sensing technology, and in particular to a temperature sensing circuit. Background Art

[0002] In low-voltage system-on-a-chip circuits, the temperature inside the chip can be sensed based on the time variation or the signal delay characteristics that vary with temperature. However, common temperature sensing circuits, whether using a delay line to generate a signal with a time difference for temperature sensing or using the current difference between current mirror branches for temperature sensing, are susceptible to the effects of process offsets of metal oxide semiconductor transistors in the circuit or changes in channel length, resulting in inaccurate temperature sensing.

[0003] Therefore, how to design a new temperature sensing circuit to solve the above-mentioned deficiencies is an urgent problem to be solved in the industry. Summary of the invention

[0004] The invention summary is intended to provide a simplified summary of the present disclosure so that readers can have a basic understanding of the present disclosure. This invention summary is not a complete overview of the present disclosure, and it is not intended to point out the important / critical elements of the embodiments of the present invention or to define the scope of the present invention.

[0005] An object of the present invention is to provide a temperature sensing circuit to improve the problems of the prior art.

[0006] To achieve the above-mentioned purpose, a technical implementation of the content of the present invention relates to a temperature sensing circuit, comprising: a bandgap voltage generating circuit, a current mirror branch, a variable resistor, a comparison circuit, a control circuit and a temperature judgment circuit. The bandgap voltage generating circuit is configured to generate a bandgap voltage having a first temperature coefficient. The current mirror branch is configured to mirror a mirror current having a second temperature coefficient different from the first temperature coefficient from the bandgap voltage generating circuit. The variable resistor includes a first end electrically coupled to the current mirror branch to receive the mirror current and generate a variable voltage at the first end. The comparison circuit is configured to compare the bandgap voltage and the variable voltage to generate a comparison result. The control circuit is configured to generate a control signal according to the comparison result to continuously adjust the resistance value of the variable resistor, and output a signal value when the signal value of the control signal makes the variable voltage substantially equal to the bandgap voltage. The temperature judgment circuit is configured to generate a temperature value according to the signal value.

[0007] When the temperature sensing circuit of the present invention completes sensing, the voltages used for comparison to sense the temperature are equal to each other, thereby eliminating the channel length modulation effect between the transistors used to generate the two voltages, thereby greatly improving the accuracy of temperature sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to make the above and other objects, features, advantages and embodiments of the present invention more clearly understood, the following are the descriptions of the accompanying drawings:

[0009] Figure 1 A circuit diagram of a temperature sensing circuit in one embodiment of the present invention;

[0010] Figure 2 A circuit diagram of a temperature sensing circuit in one embodiment of the present invention;

[0011] Figure 3A A circuit diagram of a temperature sensing circuit in one embodiment of the present invention; and

[0012] Figure 3B FIG. 4 is a circuit diagram of an operational amplifier according to an embodiment of the present invention.

[0013] Explanation of symbols

[0014] 100, 200, 300: temperature sensing circuit 110: bandgap voltage generating circuit

[0015] 112: Current source circuit 114: Voltage equalization circuit

[0016] 120: Current mirror branch 130: Comparison circuit

[0017] 140: Control circuit 150: Temperature determination circuit

[0018] 310: Averaging Circuit 320: Operational Amplifier

[0019] B1, B2: Base C1, C2: Collector

[0020] CL: control signal CR: comparison result

[0021] D1, D2, D3: Drain Dout: signal value

[0022] E1, E2: emitter F1: first end

[0023] F2: Second terminal G1, G2, G3: Gate

[0024] GND: ground terminal I1, I2: current

[0025] IN1, IN2: Input terminal I PTAT ,I ZTC : Mirror current

[0026] OUT: Output terminal P1, P2, P3: P-type metal oxide

[0027] Q1, Q2: Bipolar junction transistor semiconductor transistor

[0028] RG: resistance RB: balancing resistance

[0029] S1, S2, S3: Source RV: Variable resistor

[0030] T2: Second end T1: First end

[0031] VA: variable voltage TP: temperature value

[0032] VDD: voltage source V CTAT : Bandgap voltage DETAILED DESCRIPTION

[0033] Please refer to Figure 1 . Figure 1 FIG. 1 is a circuit diagram of a temperature sensing circuit 100 according to an embodiment of the present invention. The temperature sensing circuit 100 comprises a bandgap voltage generating circuit 110 , a current mirror branch 120 , a variable resistor RV, a comparison circuit 130 , a control circuit 140 and a temperature determination circuit 150 .

[0034] The bandgap voltage generating circuit 110 is configured to generate a bandgap voltage V having a first temperature coefficient. CTAT In one embodiment, the bandgap voltage generating circuit 110 includes a current source circuit 112 , a resistor RG, a pair of bipolar junction transistors Q1 and Q2 , and a voltage equalizing circuit 114 .

[0035] In one embodiment, the current source circuit 112 includes a first current source branch corresponding to the first current output terminal and a second current source branch corresponding to the second current output terminal, wherein the first current source branch includes a P-type metal oxide semiconductor transistor P1 and the second current source branch includes a P-type metal oxide semiconductor transistor P2.

[0036] A pair of sources S1 and S2 of the P-type metal oxide semiconductor transistors P1 and P2 are electrically coupled to a voltage source VDD. A drain D1 of the P-type metal oxide semiconductor transistor P1 serves as a first current output terminal to output a current I1. A drain D2 of the P-type metal oxide semiconductor transistor P2 serves as a second current output terminal to output a current I2.

[0037] The resistor RG includes a first terminal T1 electrically coupled to the first current output terminal and a second terminal T2 .

[0038] A pair of bases B1 and B2 of the bipolar junction transistors Q1 and Q2 are electrically coupled to each other, and the pair of bases B1 and B2 are also electrically coupled to the ground terminal GND. A pair of collectors C1 and C2 of the bipolar junction transistors Q1 and Q2 are electrically coupled to the ground terminal GND.

[0039] Furthermore, the emitter E1 of the bipolar junction transistor Q1 is electrically coupled to the second end T2 of the resistor RG. Therefore, the emitter E1 of the bipolar junction transistor Q1 and the first current output end, that is, the drain D1 of the P-type metal oxide semiconductor transistor P1, are electrically coupled through the resistor RG. The emitter E2 of the bipolar junction transistor Q2 is electrically coupled to the second current output end, that is, the drain D2 of the P-type metal oxide semiconductor transistor P2.

[0040] The voltage equalization circuit 114 is configured to electrically couple the first current output terminal and the second current output terminal (the drains D1 and D2 of the P-type metal oxide semiconductor transistors P1 and P2) and control the current source circuit 112 to make the voltages of the first current output terminal and the second current output terminal equal.

[0041] More specifically, in one embodiment, the voltage equalization circuit 114 is an operational amplifier and includes Figure 1 The positive input terminal, negative input terminal and output terminal are marked with '+', '-' and 'o' respectively.

[0042] The positive input terminal is electrically coupled to the first current output terminal (the drain D1 of the P-type metal oxide semiconductor transistor P1) and to the emitter E1 of the bipolar junction transistor Q1 through the resistor RG. The negative input terminal is electrically coupled to the second current output terminal (the drain D2 of the P-type metal oxide semiconductor transistor P2) and the emitter E2 of the bipolar junction transistor Q2.

[0043] The output terminal is electrically coupled to a pair of gates G1 and G2 of the P-type metal oxide semiconductor transistors P1 and P2, and is configured to control the P-type metal oxide semiconductor transistors P1 and P2 to achieve the technical effect of making the voltages of the first current output terminal and the second current output terminal equal.

[0044] Through the above structure, the bandgap voltage generating circuit 110 can generate a bandgap voltage V having a first temperature coefficient at the first end T1 of the resistor RG. CTAT In one embodiment, the current I1 and the current I2 output by the current source circuit 112 both have positive temperature coefficients, that is, the current values ​​of the current I1 and the current I2 both increase as the temperature of the environment in which the temperature sensing circuit 100 is located increases. CTAT For , its first temperature coefficient is a negative temperature coefficient. That is, the bandgap voltage V CTAT The voltage value of decreases as the temperature of the environment in which the temperature sensing circuit 100 is located increases.

[0045] The current mirror branch 120 is configured to mirror a mirror current I having a second temperature coefficient different from the first temperature coefficient from the bandgap voltage generating circuit 110.PTAT .

[0046] More specifically, in one embodiment, the current mirror branch 120 includes a P-type metal oxide semiconductor transistor P3, wherein a source S3 of the P-type metal oxide semiconductor transistor P3 is electrically coupled to a voltage source VDD, a gate G3 is electrically coupled to gates G1 and G2 of the P-type metal oxide semiconductor transistors P1 and P2, and a drain D3 serves as a third current output terminal.

[0047] Therefore, the current mirror branch 120 and the second current source branch including the P-type metal oxide semiconductor transistor P2 in the current source circuit 112 form a current mirror together to generate a mirror current I according to the current I2. PTAT , is output from the drain D3 of the P-type metal oxide semiconductor transistor P3. Since the current I2 generated by the second current source branch has a positive temperature coefficient, the mirror current I PTAT The second temperature coefficient of is also a positive temperature coefficient.

[0048] The variable resistor RV includes a first terminal F1 electrically coupled to the current mirror branch 120 and a second terminal F2 electrically coupled to the ground terminal GND. The variable resistor RV receives the mirror current I PTAT A variable voltage VA is generated at the first terminal F1.

[0049] The comparison circuit 130 is configured to compare the bandgap voltage V CTAT and a variable voltage VA to generate a comparison result CR.

[0050] In one embodiment, the control circuit 140 is a successive approximation control circuit and is configured to generate a control signal CL according to the comparison result CR to continuously adjust the resistance value of the variable resistor RV. When the signal value Dout of the control signal CL makes the variable voltage VA and the bandgap voltage V CTAT In one embodiment, the control signal CL is a digital control signal, and the signal value Dout is a digital code.

[0051] In one embodiment, the term “substantially equal” means that the variable voltage VA and the bandgap voltage V CTAT There may be a reasonable error between them, and they do not have to be completely equal. More specifically, in the most ideal situation, the resistance value of the variable resistor RV is controlled by the control circuit 140 so that the variable voltage VA is completely equal to the bandgap voltage V CTAT But in practice, the variable voltage VA can be closest to the bandgap voltage V CTAT The degree of adjustment depends on the adjustable accuracy of the variable resistor RV.

[0052] Therefore, when the control circuit 140 continues to adjust the resistance value of the variable resistor RV, it is found that the comparison result CR shows that the variable voltage VA is equal to the bandgap voltage V CTAT When the difference between the variable voltage VA and the bandgap voltage V is the smallest, it is determined that the variable voltage VA is equal to the bandgap voltage V CTAT are substantially equal, and output a corresponding signal value Dout of the control signal CL.

[0053] It should be noted that the variable voltage VA is the voltage of the drain D3 of the P-type metal oxide semiconductor transistor P3, and the bandgap voltage V CTAT That is, the voltage of the drain D1 of the P-type metal oxide semiconductor transistor P1. Therefore, when the variable voltage VA is equal to the bandgap voltage V CTAT When the voltages of the drains D1 and D3 of the P-type metal oxide semiconductor transistors P1 and P3 are substantially equal, the voltages of the drains D1 and D3 of the P-type metal oxide semiconductor transistors P1 and P3 are also substantially equal.

[0054] The temperature determination circuit 150 is configured to generate a temperature value TP according to the signal value Dout. In one embodiment, the temperature determination circuit 150 can calculate the temperature value TP by, for example, but not limited to, looking up a comparison table or relationship between the signal value Dout and the temperature.

[0055] Taking the relationship between the signal value Dout and temperature as an example, since the variable voltage VA is related to the bandgap voltage V CTAT are substantially equal, and the value of the variable voltage VA is I PTAT ×RV, so the variable voltage VA is related to the bandgap voltage V CTAT The relationship can be expressed as:

[0056] I PTAT ×RV=I PTAT ×Dout×Ru=V CTAT (Formula 1)

[0057] Here, Ru is the unit resistance of the variable resistor RV.

[0058] Furthermore, the bandgap voltage V CTAT and the variable voltage VA can be expressed as:

[0059] V CTAT =V0-aT (Formula 2)

[0060] VA = bT (Formula 3)

[0061] Wherein, V0 is an initial voltage, T is temperature, a is a first temperature coefficient, and b is a second temperature coefficient.

[0062] By reorganizing the above equations 1 to 3, the temperature T can be obtained:

[0063] T = V0 / (Dout × b × Ru + a) (Formula 4)

[0064] In some technologies, the temperature sensing circuit 100 often uses different currents to compare the different responses to temperature changes when performing temperature sensing to achieve the technical effect of sensing. However, this method is easily affected by the channel length modulation of the transistors used to generate these currents, resulting in reduced accuracy.

[0065] When the temperature sensing circuit 100 of the present invention completes the sensing, the voltages used for comparison to sense the temperature are equal to each other, thereby eliminating the channel length modulation effect between the transistors used to generate the two voltages, thereby greatly improving the accuracy of temperature sensing.

[0066] Please refer to Figure 2 . Figure 2 FIG. 2 is a circuit diagram of a temperature sensing circuit 200 according to an embodiment of the present invention.

[0067] The temperature sensing circuit 200 and Figure 1 The temperature sensing circuit 100 shown is similar, and includes: a bandgap voltage generating circuit 110, a current mirror branch 120, a variable resistor RV, a comparison circuit 130, a control circuit 140 and a temperature determination circuit 150. Figure 1 The difference between the illustrated temperature sensing circuit 100 is that the temperature sensing circuit 200 further includes a balancing resistor RB.

[0068] like Figure 2 As shown, the balancing resistor RB is connected in parallel with the bipolar junction transistor Q2 to achieve the purpose of balancing the current. In more detail, the current I2 generated by the first current source branch and the second current source branch of the current source circuit 112 originally has a positive temperature coefficient. The addition of the balancing resistor RB will generate a current with a negative temperature coefficient, and the positive temperature coefficient effect of the current I2 will be offset under the appropriate selection of the resistance value, and the mirror current I2 will be mirrored in the current mirror branch 120. ZTC The mirror current I has a zero temperature coefficient related to temperature zero. ZTC .

[0069] Similar to the operation of the aforementioned temperature sensing circuit 100, the variable resistor RV can receive the mirror current I ZTC A variable voltage VA is generated at the first terminal F1 to be configured by the comparison circuit 130 to compare the bandgap voltage V CTAT The variable voltage VA generates a comparison result CR, and the control circuit 140 generates a control signal CL according to the comparison result CR to continuously adjust the resistance value of the variable resistor RV. When the signal value Dout of the control signal CL makes the variable voltage VA and the bandgap voltage V CTATWhen the signal values ​​Dout are substantially equal, the temperature determination circuit 150 is configured to generate a temperature value TP according to the signal value Dout.

[0070] Please refer to Figure 3A . Figure 3A FIG. 4 is a circuit diagram of a temperature sensing circuit 300 according to an embodiment of the present invention.

[0071] The temperature sensing circuit 300 and Figure 1 The temperature sensing circuit 100 shown is similar, and includes: a bandgap voltage generating circuit 110, a current mirror branch 120, a variable resistor RV, a comparison circuit 130, a control circuit 140 and a temperature determination circuit 150. Figure 1 The difference of the temperature sensing circuit 100 shown is that the temperature sensing circuit 300 further includes a plurality of averaging circuits 310 .

[0072] In one embodiment, the averaging circuit 310 is disposed between the first current source branch and the second current source branch and between the first current source branch and the current mirror branch, and includes a chopper and a dynamic element matching (DEM) circuit to average the corresponding pair of voltage signals respectively to further improve accuracy.

[0073] Please also refer to Figure 3B . Figure 3B FIG. 4 is a circuit diagram of an operational amplifier 320 according to an embodiment of the present invention.

[0074] The operational amplifier 320 can be used to implement the voltage equalization circuit 114 and the comparison circuit 130 in the temperature sensing circuit 300, and includes two input terminals IN1, IN2 and an output terminal OUT. Taking the voltage equalization circuit 114 as an example, the two input terminals IN1, IN2 can be electrically coupled to the drains D1, D2 of the P-type metal oxide semiconductor transistors P1, P2, respectively, and the output terminal OUT can be electrically coupled to the gates G1, G2 of the P-type metal oxide semiconductor transistors P1, P2. The two input terminals IN1, IN2 of the comparison circuit 130 can be electrically coupled to the first terminal F1 of the variable resistor RV and the first terminal T1 of the resistor RG, respectively, and the output terminal OUT can be used to generate a comparison result CR.

[0075] In one embodiment, the operational amplifier 320 may also be provided with an averaging circuit 310 to average the corresponding pair of voltage signals respectively to further improve the accuracy.

[0076] It should be noted that Figure 1 , Figure 2 as well as Figure 3AThe circuit structures of the temperature sensing circuits 100, 200, and 300 shown are merely examples. In other embodiments, the temperature sensing circuits 100, 200, and 300 may be added with other circuit elements without affecting the operation of the above-mentioned circuits. The present invention is not limited thereto.

[0077] Furthermore, in the above-mentioned embodiments, the first temperature coefficient is a negative temperature coefficient, and the second temperature coefficient is a positive temperature coefficient or a zero temperature coefficient. In other embodiments, when the first temperature coefficient and the second temperature coefficient are different, the circuit structure can be appropriately adjusted to make the first temperature coefficient a positive temperature coefficient or a zero temperature coefficient, or to make the second temperature coefficient a negative temperature coefficient. The present invention is not limited to the above-mentioned embodiments.

[0078] Although specific embodiments of the present invention are disclosed in the above implementation modes, they are not intended to limit the present invention. Technicians in the technical field to which the present invention belongs can make various changes and modifications without departing from the principles and concepts of the present invention. Therefore, the scope of protection of the present invention shall be based on that defined in the appended claims.

Claims

1. A temperature sensing circuit, comprising: a bandgap voltage generating circuit configured to generate a bandgap voltage having a first temperature coefficient; a current mirror branch configured to mirror a mirror current having a second temperature coefficient different from the first temperature coefficient from the bandgap voltage generating circuit; A variable resistor, comprising a first end electrically coupled to the current mirror branch, for receiving the mirror current and generating a variable voltage at the first end; a comparison circuit configured to compare the bandgap voltage and the variable voltage to generate a comparison result; a control circuit configured to generate a control signal according to the comparison result to continuously adjust a resistance value of the variable resistor, and output the signal value when a signal value of the control signal makes the variable voltage substantially equal to the bandgap voltage; and a temperature determination circuit configured to generate a temperature value according to the signal value, wherein the bandgap voltage generation circuit further comprises: A current source circuit having a first current output terminal and a second current output terminal; a resistor, comprising a first end and a second end electrically coupled to the first current output end, wherein the first end of the resistor is configured to generate the bandgap voltage; a pair of bipolar junction transistors, a first one of the pair of bipolar junction transistors is electrically coupled to the second end of the resistor, and a second one of the pair of bipolar junction transistors is electrically coupled to the second current output end; and a voltage equalization circuit configured to electrically couple the first current output terminal and the second current output terminal and control the current source circuit to make the first current output terminal and the second current output terminal have the same voltage; The current source circuit includes a first current source branch corresponding to the first current output terminal and a second current source branch corresponding to the second current output terminal, and the current mirror branch is configured to generate the mirror current according to the mirror image of the second current source branch. 2 . The temperature sensing circuit as claimed in claim 1 , wherein the first temperature coefficient of the bandgap voltage is a negative temperature coefficient, and the second temperature coefficient is a positive temperature coefficient. 3 . The temperature sensing circuit as claimed in claim 1 , wherein the first temperature coefficient of the bandgap voltage is a negative temperature coefficient, and the second temperature coefficient is a zero temperature coefficient that makes the mirror current have zero correlation with temperature. 4 . The temperature sensing circuit as claimed in claim 1 , wherein the control signal is a digital control signal, and the signal value is a digital code. The temperature sensing circuit as claimed in claim 1 , wherein the control circuit is an asymptotic control circuit.

6. The temperature sensing circuit as described in claim 1, wherein the first current source branch includes a first metal oxide semiconductor transistor, and the current mirror branch includes a third metal oxide semiconductor transistor, and when the variable voltage is substantially equal to the bandgap voltage, the drain voltages of the first metal oxide semiconductor transistor and the third metal oxide semiconductor transistor are substantially equal.

7. The temperature sensing circuit as described in claim 1, wherein an averaging circuit is included between the first current source branch and the second current source branch, between the first current source branch and the current mirror branch, in the voltage equalization circuit, and in the comparison circuit, and the averaging circuit has a chopper and a dynamic element matching circuit to average the corresponding pair of voltage signals respectively. 8 . The temperature sensing circuit as claimed in claim 1 , wherein the second one of the pair of bipolar junction transistors is connected in parallel with a balancing resistor.

Images