A TEC driving circuit for use in a single photon detector

Abstract

The application discloses a TEC driving circuit used in a single photon detector and relates to the field of TEC control.The driving circuit comprises an operational amplifier U1, an operational amplifier U2, an operational amplifier U3, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C1 and a capacitor C2, the inverting terminal of the operational amplifier U1 is connected with one end of the resistor R5 and the resistor R6, and the output terminal is connected with the other end of the resistor R6.The application can provide a high-quality signal source for a lower circuit by linearly outputting a voltage signal when the resistance value of a thermistor changes due to temperature change, so as to improve the control precision of the TEC.The application realizes hierarchical compensation by constructing P, I and D independent parallel channels, prevents mutual coupling and oscillation, and realizes safe, bidirectional and linear driving of a TEC load in a linear working area with an absolute value of the control voltage being higher than 0.6V.

Description

Technical Field

[0001] This invention relates to the field of TEC control, and in particular to a TEC drive circuit for use in a single-photon detector. Background Technology

[0002] In fields such as lasers, optical modules, biomedical devices, and detection, thermoelectric coolers (TECs) are widely used due to their small size, fast response, and bidirectional temperature control. The temperature control accuracy of the TEC drive circuit largely depends on the quality of the front-end temperature signal acquisition and the linearity and stability of the back-end power drive circuit.

[0003] Currently, common TEC drive circuits have the following shortcomings:

[0004] Firstly, there is the nonlinearity issue in temperature signal acquisition. Existing solutions often use negative temperature coefficient (NTC) thermistors as temperature sensors, acquiring the temperature signal by voltage division through a fixed resistor connected in series with the NTC. However, the resistance of the NTC thermistor decreases drastically with increasing temperature, resulting in a nonlinear change. This voltage division causes the current flowing through the NTC and the voltage drop across the fixed resistor to change synchronously, leading to inconsistent output voltage variations with temperature. Specifically, the signal variation is large in the low-temperature region and small in the high-temperature region. This inherent nonlinear signal directly enters the control loop, severely limiting the error calculation accuracy of the PID circuit and reducing the control accuracy of the TEC.

[0005] Secondly, traditional PID compensation networks suffer from strong coupling and oscillation risks. To reduce the number of components and lower costs, existing PID controllers are typically constructed using a single operational amplifier, integrating the proportional (P), integral (I), and derivative (D) control actions into a single feedback network. Each control parameter is set through the same set of resistors and capacitors, resulting in high coupling between them. If a parameter needs adjustment during debugging, it often simultaneously affects the zero and pole positions of the other two channels, making it difficult to independently control the phase characteristics. This easily leads to self-excited oscillations, significantly increasing the difficulty of circuit debugging and system instability.

[0006] Thirdly, the nonlinear dead zone and through-current risk of the TEC drive circuit: When driving the TEC bidirectionally linearly, a complementary push-pull output stage is usually used. Near the zero-crossing of the control signal, i.e., during the transition from a small positive voltage to a negative voltage, if not handled properly, the upper and lower power transistors of the push-pull stage may momentarily conduct simultaneously due to a small offset voltage, forming a low-impedance path from the power supply to ground, resulting in excessive through-current and damaging the device. At the same time, the inherent emitter junction conduction threshold of the power transistor will generate a dead zone of current output when the control voltage crosses zero, which disrupts the linearity of the drive current and makes it difficult to achieve safe, smooth, and linear bidirectional current switching. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a TEC driving circuit for use in a single-photon detector. The driving circuit includes operational amplifiers U1, U2, and U3; resistors R5, R6, R7, R8, and R9; and capacitors C1 and C2. The inverting input of operational amplifier U1 is connected to one end of resistors R5 and R6; its output is connected to the other end of resistor R6. The inverting input of operational amplifier U2 is connected to one end of capacitor C1 and resistor R7; its output is connected to the other end of capacitor C1. The inverting input of operational amplifier U3 is connected to one end of resistors R8 and R9; its output is connected to the other end of resistor R9. The other end of resistor R8 is connected to one end of capacitor C2, and the other end of capacitor C2 is connected to the other end of resistors R5 and R7. The non-inverting inputs of operational amplifiers U1, U2, and U3 are grounded.

[0008] Furthermore, the driving circuit also includes operational amplifier U4, resistors R10, R11, R12, and R13. The inverting input of operational amplifier U4 is connected to one end of resistors R10, R11, R12, and R13; the output input is connected to the other end of resistor R13; the non-inverting input is grounded; the other end of resistor R10 is connected to the output of operational amplifier U1; the other end of resistor R11 is connected to the output of operational amplifier U2; and the other end of resistor R12 is connected to the output of operational amplifier U3.

[0009] Furthermore, the driving circuit also includes diodes D1 and D2, resistors R14, R15, and R16, transistors Q1 and Q2. The base of transistor Q1 is connected to one end of resistor R14, one end of resistor R15, one end of resistor R16, and the base of transistor Q2; the collector is connected to a positive power supply; the emitter is connected to the emitter of transistor Q2; the collector of transistor Q2 is connected to a negative power supply; the other end of resistor R15 is connected to the output terminal of operational amplifier U4; the other end of resistor R14 is connected to the anode of diode D2; the cathode of diode D2 is connected to a negative power supply; the other end of resistor R16 is connected to the cathode of diode D1; and the anode of diode D1 is connected to a positive power supply.

[0010] Furthermore, the driving circuit also includes operational amplifier U5, operational amplifier U6, voltage regulator chip U7, resistors R1, R2, R3, R4, R17, R18, and thermistor RT. The inverting input of operational amplifier U6 is connected to one end of resistors R1 and R2; the non-inverting input is connected to one end of resistors R3 and R4; the output is connected to the other end of resistors R1, R5, R7, and capacitor C2. Resistor R2 is used to input the set temperature signal. The inverting input of operational amplifier U5 is connected to one end of resistor R18 and thermistor RT; the non-inverting input is connected to one end of resistor R17 and the cathode of voltage regulator chip U7; the output is connected to the other end of thermistor RT and resistor R3; the anode of voltage regulator chip U7 is grounded; the adjustment terminal is left floating; and the other end of resistor R17 is connected to the positive power supply.

[0011] Furthermore, resistors R5, R6, R7, R8, and R9 are adjustable resistors, and capacitors C1 and C2 are adjustable capacitors.

[0012] Furthermore, resistors R14, R15, and R16 are adjustable resistors.

[0013] Furthermore, the resistor R18 is an adjustable resistor.

[0014] The beneficial effects of this invention compared to the prior art are:

[0015] This invention enables the linear output voltage signal to provide a high-quality signal source for the downstream circuit when the resistance of the thermistor changes due to temperature variations, thereby improving the control accuracy of the TEC. By constructing independent parallel channels for P, I, and D to achieve hierarchical compensation, mutual coupling and oscillation are prevented. Within the linear operating range where the absolute value of the control voltage is higher than 0.6V, safe, bidirectional, and linear drive of the TEC load is achieved. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0018] To make the objectives and advantages of the present invention clearer, the present invention will be specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or more specific embodiments of the present invention and does not strictly limit the scope of protection specifically claimed by the present invention.

[0019] The present invention discloses that the purpose of the present invention is to provide a TEC driving circuit for a single-photon detector. The driving circuit includes operational amplifiers U1, U2, and U3, resistors R5, R6, R7, R8, and R9, and capacitors C1 and C2. The inverting input of operational amplifier U1 is connected to one end of resistors R5 and R6, and its output is connected to the other end of resistor R6. The inverting input of operational amplifier U2 is connected to one end of capacitor C1 and resistor R7, and its output is connected to the other end of capacitor C1. The inverting input of operational amplifier U3 is connected to one end of resistors R8 and R9, and its output is connected to the other end of resistor R9. The other end of resistor R8 is connected to one end of capacitor C2, and the other end of capacitor C2 is connected to the other end of resistors R5 and R7. The non-inverting inputs of operational amplifiers U1, U2, and U3 are grounded.

[0020] Specifically, the driving circuit also includes operational amplifier U4, resistors R10, R11, R12, and R13. The inverting input of operational amplifier U4 is connected to one end of resistors R10, R11, R12, and R13; the output input is connected to the other end of resistor R13; the non-inverting input is grounded; the other end of resistor R10 is connected to the output of operational amplifier U1; the other end of resistor R11 is connected to the output of operational amplifier U2; and the other end of resistor R12 is connected to the output of operational amplifier U3.

[0021] Specifically, the driving circuit further includes diodes D1 and D2, resistors R14, R15, and R16, transistors Q1 and Q2. The base of transistor Q1 is connected to one end of resistor R14, one end of resistor R15, one end of resistor R16, and the base of transistor Q2; the collector is connected to a positive power supply; the emitter is connected to the emitter of transistor Q2; the collector of transistor Q2 is connected to a negative power supply; the other end of resistor R15 is connected to the output terminal of operational amplifier U4; the other end of resistor R14 is connected to the anode of diode D2; the cathode of diode D2 is connected to a negative power supply; the other end of resistor R16 is connected to the cathode of diode D1; and the anode of diode D1 is connected to a positive power supply.

[0022] Specifically, the driving circuit also includes operational amplifier U5, operational amplifier U6, voltage regulator chip U7, resistors R1, R2, R3, R4, R17, R18, and thermistor RT. The inverting input of operational amplifier U6 is connected to one end of resistors R1 and R2; the non-inverting input is connected to one end of resistors R3 and R4; the output is connected to the other end of resistors R1, R5, R7, and capacitor C2. Resistor R2 is used to input the set temperature signal. The inverting input of operational amplifier U5 is connected to one end of resistor R18 and thermistor RT; the non-inverting input is connected to one end of resistor R17 and the cathode of voltage regulator chip U7; the output is connected to the other end of thermistor RT and resistor R3; the anode of voltage regulator chip U7 is grounded; the adjustment terminal is left floating; and the other end of resistor R17 is connected to the positive power supply.

[0023] Specifically, resistors R5, R6, R7, R8, and R9 are adjustable resistors, and capacitors C1 and C2 are adjustable capacitors.

[0024] Specifically, resistors R14, R15, and R16 are adjustable resistors.

[0025] Specifically, the resistor R18 is an adjustable resistor.

[0026] The P-signal output channel is composed of operational amplifier U1, resistors R5 and R6. Resistor R5 is the P-channel input resistor, and resistor R6 is the feedback resistor. Operational amplifier U1 outputs an instantaneous control signal proportional to the current error. Adjusting the parameters of resistors R5 and R6 sets the gain ratio of the instantaneous control signal. The signal output by operational amplifier U1 is the P-channel compensation signal. The I-signal output channel is composed of operational amplifier U2, resistor R7, and capacitor C1. Resistor R7 is the I-channel integration input resistor, and capacitor C1 is the integration capacitor. Operational amplifier U2 integrates the error signal and outputs it. Adjusting the parameters of resistors R7 and capacitor C1 sets the integration speed. The signal output by operational amplifier U2 is the I-channel compensation signal. The D-signal output channel is composed of operational amplifier U3, capacitor C2, resistors R8 and R9. Capacitor C2 is the D-channel input coupling capacitor, used to... The error signal variation is coupled to the inverting input of op-amp U3. Resistor R8 is the current-limiting resistor for the inverting input of op-amp U3, and resistor R9 is the feedback resistor. Adjusting the parameter of resistor R9 sets the differential gain coefficient, adjusting the parameter of capacitor C2 sets the sensitivity to error changes, and adjusting the parameter of resistor R8 sets the peak value. The signal output by op-amp U3 is the D-channel compensation signal. Based on op-amp U1, op-amp U2, and op-amp U3, three independent parallel channels of P, I, and D are constructed to achieve hierarchical compensation, prevent mutual coupling and oscillation. Resistors R10, R11, and R12 are the input resistors of the three compensation signals of P, I, and D, respectively. Resistors R10, R11, and R12 are equal-value resistors, and resistor R13 is the feedback resistor. Op-amp U4 adds the three signals of P, I, and D with equal weights and outputs them inverted.

[0027] Resistors R16 and R14 limit the upper limit of the base current of transistors Q1 and Q2. Diode D1 blocks the current from flowing from the base of transistors Q1 and Q2 to VCC during the negative half-cycle current, and diode D2 blocks the current from flowing from VEE to the base of transistors Q1 and Q2 during the positive half-cycle current. Resistor R15 prevents DC overload at the output of operational amplifier U4, ensuring that operational amplifier U4 controls the bases of transistors Q1 and Q2 only through voltage-controlled amp. When the signal at the output of operational amplifier U4 changes from positive to negative voltage, the emitter current of transistors Q1 and Q2 flows from the positive to the reverse direction, thereby driving the TEC to perform bidirectional current switching. The higher the output signal voltage of op-amp U4, the greater the current flowing out or into the emitter terminals of transistors Q1 and Q2. When the output signal of op-amp U4 ranges from 0V to ±0.6V, no current flows out or into the emitter terminals of transistors Q1 and Q2. During this period, transistors Q1 and Q2 are in the off state to prevent short circuits. By adjusting the resistance values ​​of resistors R16 and R14, the upper limit of the current flowing out or into the emitter terminals of transistors Q1 and Q2 is limited to set the maximum drive current of the TEC. In this way, safe, bidirectional, and linear drive of the TEC load is achieved within the linear operating region where the absolute value of the control voltage is higher than 0.6V.

[0028] Resistor R17 is the bias resistor for the voltage regulator chip U7, ensuring that the voltage regulation at the cathode of U7 is fed back to the non-inverting input of operational amplifier U5. The output and inverting inputs of operational amplifier U5 are connected to the thermistor RT, and a constant current loop is established through resistor R18. When the temperature changes and the resistance of the thermistor RT changes, the current through resistor R18 remains constant, and the output voltage of operational amplifier U5 changes accordingly. Adjusting the parameter of resistor R18 sets the voltage amplitude of the linear output of operational amplifier U5 when the resistance of the thermistor RT changes. The output signal of operational amplifier U5 is the actual temperature signal. The op-amp U5 linearly outputs a voltage signal based on the change in the resistance of the thermistor RT, providing a high-quality signal source for the next stage circuit to improve the control accuracy of the TEC. Resistor R2 is the input resistor, used to input the set temperature signal, which is input from an external power supply. Resistor R1 is the feedback resistor of op-amp U6. The output signal of op-amp U5 is fed back to the non-inverting input of op-amp U6 after being divided by resistors R3 and R4. Op-amp U6 differentially outputs the set temperature signal and the actual temperature signal and feeds them back to the channel inputs of P, I, and D.

[0029] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A TEC driving circuit for use in a single-photon detector, characterized in that, The driving circuit includes operational amplifiers U1, U2, and U3, resistors R5, R6, R7, R8, and R9, and capacitors C1 and C2. The inverting input of operational amplifier U1 is connected to one end of resistors R5 and R6, and its output is connected to the other end of resistor R6. The inverting input of operational amplifier U2 is connected to one end of capacitor C1 and resistor R7, and its output is connected to the other end of capacitor C1. The inverting input of operational amplifier U3 is connected to one end of resistors R8 and R9, and its output is connected to the other end of resistor R9. The other end of resistor R8 is connected to one end of capacitor C2, and the other end of capacitor C2 is connected to the other end of resistors R5 and R7. The non-inverting inputs of operational amplifiers U1, U2, and U3 are grounded.

2. The TEC driving circuit for a single-photon detector according to claim 1, characterized in that, The driving circuit also includes operational amplifier U4, resistors R10, R11, R12, and R13. The inverting input of operational amplifier U4 is connected to one end of resistors R10, R11, R12, and R13; the output input is connected to the other end of resistor R13; the non-inverting input is grounded; the other end of resistor R10 is connected to the output of operational amplifier U1; the other end of resistor R11 is connected to the output of operational amplifier U2; and the other end of resistor R12 is connected to the output of operational amplifier U3.

3. The TEC driving circuit for a single-photon detector according to claim 2, characterized in that, The driving circuit also includes diodes D1 and D2, resistors R14, R15, and R16, transistors Q1 and Q2. The base of transistor Q1 is connected to one end of resistor R14, one end of resistor R15, one end of resistor R16, and the base of transistor Q2; the collector is connected to a positive power supply; the emitter is connected to the emitter of transistor Q2; the collector of transistor Q2 is connected to a negative power supply; the other end of resistor R15 is connected to the output terminal of operational amplifier U4; the other end of resistor R14 is connected to the anode of diode D2; the cathode of diode D2 is connected to a negative power supply; the other end of resistor R16 is connected to the cathode of diode D1; and the anode of diode D1 is connected to a positive power supply.

4. The TEC driving circuit for a single-photon detector according to claim 1, characterized in that, The driving circuit also includes operational amplifiers U5 and U6, a voltage regulator chip U7, resistors R1, R2, R3, R4, R17, R18, and a thermistor RT. The inverting input of operational amplifier U6 is connected to one end of resistors R1 and R2; the non-inverting input is connected to one end of resistors R3 and R4; the output is connected to the other end of resistors R1, R5, R7, and capacitor C2. Resistor R2 is used to input the set temperature signal. The inverting input of operational amplifier U5 is connected to one end of resistor R18 and the thermistor RT; the non-inverting input is connected to one end of resistor R17 and the cathode of the voltage regulator chip U7; the output is connected to the thermistor RT and the other end of resistor R3; the anode of the voltage regulator chip U7 is grounded; the adjustment terminal is left floating; and the other end of resistor R17 is connected to the positive power supply.

5. The TEC driving circuit for a single-photon detector according to claim 1, characterized in that, Resistors R5, R6, R7, R8, and R9 are adjustable resistors, and capacitors C1 and C2 are adjustable capacitors.

6. The TEC drive circuit for a single-photon detector according to claim 3, characterized in that, The resistors R14, R15, and R16 are adjustable resistors.

7. The TEC drive circuit for a single-photon detector according to claim 4, characterized in that, The resistor R18 is an adjustable resistor.

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