Low-temperature-drift high-precision constant-current circuit and constant-current source system

Abstract

The utility model relates to a low-temperature-drift high-precision constant current circuit and constant current source system, the constant current circuit comprises a digital-to-analog conversion chip, a filter circuit, a push-pull driving circuit and an output control circuit, and the output end of the digital-to-analog conversion chip is connected with the first input end of the filter circuit; the output end of the filter circuit is connected with one end of the push-pull drive circuit; the other end of the push-pull driving circuit is connected with the output control circuit; the other end of the output control circuit is connected with the second input end of the filter circuit; the output control circuit comprises a plurality of field effect transistors and a plurality of sampling resistors; the field effect transistors are connected in parallel, and the sampling resistors are connected in parallel. The constant current source system comprises a thermoelectric cooler control circuit; the thermoelectric cooler control circuit comprises a power supply circuit, a drive circuit chip and a current constant circuit. The output end of the drive circuit chip is connected with one end of the current constant circuit, and the other end is connected with the input end of the power supply circuit. The problem that power supply stability is affected due to element power consumption and element resistance drift along with temperature is solved.

Description

Technical Field

[0001] The present application relates to the technical field of analog circuit design, and in particular to a low-temperature drift and high-precision constant current circuit and a constant current source system. Background Art

[0002] The constant current source circuit is a commonly used circuit design in analog circuits to provide a constant current output.

[0003] The constant current source circuit achieves constant current output through negative feedback, and usually uses components such as voltage amplifiers and current sampling resistors to achieve stable current output.

[0004] However, the components in the conventional constant current source circuit consume power, which reduces energy efficiency and causes component overheating. The resistance value of the component drifts with the change of temperature, thus affecting the power supply stability of the circuit. Utility Model Content

[0005] In view of the above problems, the purpose of this application is to provide a low-temperature drift and high-precision constant current circuit and a constant current source system.

[0006] According to a first aspect of an embodiment of the present application, a low-temperature drift and high-precision constant current circuit is provided, the constant current circuit comprising a digital-to-analog conversion chip, a filtering circuit, a push-pull drive circuit and an output control circuit, the output end of the digital-to-analog conversion chip is connected to the first input end of the filtering circuit; the output end of the filtering circuit is connected to one end of the push-pull drive circuit; the other end of the push-pull drive circuit is connected to the output control circuit; the other end of the output control circuit is connected to the second input end of the filtering circuit; the output control circuit comprises a plurality of field effect transistors and a plurality of sampling resistors; the field effect transistors are connected in parallel; the sampling resistors are connected in parallel.

[0007] Further, the output control circuit includes a field effect tube 2N2, a field effect tube 2N1, a Zener diode, a resistor 2R13, a resistor 2R11, a resistor 2R15, a resistor 2R16, a capacitor 2C35, a sampling resistor 2R59, a sampling resistor 2R60 and a laser module; one end of the Zener diode is grounded, and the other end is connected to the push-pull drive circuit, one end of the resistor 2R11 and one end of the resistor 2R13; the other end of the resistor 2R13 is connected to the gate of the field effect tube 2N2 and one end of the resistor 2R15; the other end of the resistor 2R15 is grounded; the source of the field effect tube 2N2 is connected to the filter circuit, the capacitor 2C35, the sampling resistor 2R 59 and one end of the sampling resistor 2R60; the other ends of the capacitor 2C35, the sampling resistor 2R59 and the sampling resistor 2R60 are grounded; the drain of the field effect tube 2N2 is connected to the laser module; the other end of the resistor 2R11 is connected to the gate of the field effect tube 2N1 and one end of the resistor 2R16; the other end of the resistor 2R16 is grounded; the source of the field effect tube 2N1 is connected to the filter circuit, the capacitor 2C35, the sampling resistor 2R59 and one end of the sampling resistor 2R60; the other ends of the capacitor 2C35, the sampling resistor 2R59 and the sampling resistor 2R60 are grounded; the drain of the field effect tube 2N1 is connected to the laser module.

[0008] Further, the filtering circuit includes: a resistor 2R1, a resistor 2R2, a resistor 2R6, a resistor 2R7, a resistor 2R8, an operational amplifier 2U2B, an operational amplifier 2U3B, a capacitor 2C40, a shutdown pin and a capacitor 2C41; one end of the resistor 2R1 is connected to the VDD end of the digital-to-analog conversion chip, and the other end is connected to the in-phase input end of the operational amplifier 2U2B; the reverse input end of the operational amplifier 2U2B is connected to one end of the resistor 2R2; the other end of the resistor 2R2 is connected to the output end of the operational amplifier 2U2B and the capacitor 2C41. one end of the resistor 2R6; the other end of the resistor 2R6 is connected to one end of the resistor 2R7, one end of the capacitor 2C40 and the in-phase input end of the operational amplifier 2U3B; the other end of the resistor 2R7 and the other end of the capacitor 2C40 are grounded; the reverse input end of the operational amplifier 2U3B is connected to the output control circuit, one end of the resistor 2R8 and the shutdown pin; the other end of the resistor 2R8 is connected to one end of the capacitor 2C41; the other end of the capacitor 2C41 is connected to the output end of the operational amplifier 2U3B and the push-pull drive circuit.

[0009] Furthermore, the digital-to-analog conversion chip is MS5541; the push-pull drive circuit includes: a resistor 2R9, a common base transistor 2Q2 and a common base transistor 2Q1; one end of the resistor 2R9 is connected to the filter circuit, and the other end is connected to the base of the common base transistor 2Q1 and the base of the common base transistor 2Q2; the collector of the common base transistor 2Q1 is connected to electricity; the emitter of the common base transistor 2Q1 is connected to the emitter of the common base transistor 2Q2 and the output control circuit; the collector of the common base transistor 2Q2 is grounded.

[0010] According to the second aspect of the embodiment of the present application, a constant current source system is provided, comprising: a microcontroller unit, a thermistor sensor, a copper plate, a semiconductor cooling sheet, a protection circuit, a thermoelectric cooler control circuit and the circuit described in any one of the above items; the microcontroller unit is connected to the protection circuit, the constant current circuit and the thermoelectric cooler control circuit; the microcontroller unit is used to output control signals to the constant current circuit and the thermoelectric cooler control circuit; the thermoelectric cooler control circuit is connected to the semiconductor cooling sheet; the semiconductor cooling sheet is applied with the thermal grease and is attached to one side of the copper plate; the other side of the copper plate is attached to the sampling resistor in the constant current circuit; the sampling resistor is applied with the thermal grease; one end of the thermistor sensor is connected to the copper plate, and the other end is connected to the microcontroller unit, and the thermistor sensor is used to collect the temperature of the copper plate and transmit it to the microcontroller unit.

[0011] Furthermore, the thermoelectric cooler control circuit includes a power supply circuit, a drive circuit chip and a current constant circuit; the output end of the drive circuit chip is connected to one end of the current constant circuit, and the other end of the current constant circuit is connected to the input end of the power supply circuit.

[0012] Furthermore, the constant current circuit includes a first branch and a second branch; the drive circuit chip includes a first drive circuit chip and a second drive circuit chip; the first drive circuit chip and the second drive circuit chip are FD2203; the first drive circuit chip is connected to one end of the first branch; the other end of the first branch is connected to the first input end of the power supply circuit; the second input end of the power supply circuit is connected to one end of the second branch; the other end of the second branch is connected to the second drive circuit chip.

[0013] Further, the first branch includes:

[0014] Resistor 6R6, resistor 6R5, resistor 6R9, ​​diode 6D1, diode 6D2, field effect transistor 6N1, field effect transistor 6N2, power supply, current terminal ISEN1;

[0015] One end of the resistor 6R5 is connected to the HO end of the first drive circuit chip and one end of the resistor 6R6, and the other end is connected to one end of the diode 6D1, the gate of the field effect transistor 6N1, the VS end of the first drive circuit chip, the source of the field effect transistor 6N1, the drain of the field effect transistor 6N2 and the first input end of the power supply circuit; the other end of the resistor 6R6 is connected to the other end of the diode 6D1; the drain of the field effect transistor 6N1 is connected to the power supply;

[0016] One end of the resistor 6R8 is connected to the LO end of the first drive circuit chip and one end of the resistor 6R9, ​​and the other end is connected to one end of the diode 6D2, the gate of the field effect transistor 6N2, the source of the field effect transistor 6N2 and the current end ISEN1; the other end of the resistor 6R9 is connected to the other end of the diode 6D2; the other end of the resistor 6R10.

[0017] Further, the second branch includes:

[0018] Resistor 6R11, resistor 6R12, resistor 6R14, resistor 6R15, diode 6D3, diode 6D4, field effect transistor 6N3, field effect transistor 6N4, power supply and current terminal ISEN1;

[0019] One end of the resistor 6R11 is connected to the HO end of the second drive circuit chip and one end of the resistor 6R12, and the other end is connected to one end of the diode 6D3, the gate of the field effect transistor 6N3, the VS end of the second drive circuit chip, the source of the field effect transistor 6N3, the drain of the field effect transistor 6N4 and the second input end of the power supply circuit; the other end of the resistor 6R12 is connected to the other end of the diode 6D3; the drain of the field effect transistor 6N3 is connected to the power supply;

[0020] One end of the resistor 6R14 is connected to the LO end of the second drive circuit chip and one end of the resistor 6R15, and the other end is connected to one end of the diode 6D4, the gate of the field effect transistor 6N4, the source of the field effect transistor 6N4 and the current end ISEN1; the other end of the resistor 6R15 is connected to the other end of the diode 6D4.

[0021] Furthermore, the protection circuit includes a power supply, a capacitor 2C4, a capacitor 2C5, a capacitor 6C19 and a capacitor 6C20; after the capacitor 2C4 and the capacitor 2C5 are connected in parallel, one end is connected to the power supply and the other end is grounded; after the capacitor 6C19 and the capacitor 6C20 are connected in parallel, one end is connected to the power supply and the other end is grounded.

[0022] The technical solution provided by the embodiments of the present application may have the following beneficial effects:

[0023] The present application utilizes the parallel connection of sampling resistors and field effect tubes in the constant current circuit to reduce power consumption, and controls the temperature based on the parallel shunting to reduce power. The present application controls power consumption and controls the temperature with a thermoelectric cooler by designing the parallel connection of the sampling resistors and field effect tubes in the constant current circuit, thereby improving the power supply stability of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 is a structural diagram of a constant current source system according to an exemplary embodiment;

[0026] Figure 2 is a constant current circuit schematic diagram of a low temperature drift and high precision constant current circuit according to an exemplary embodiment;

[0027] Figure 3 The figure is a schematic diagram of a thermoelectric cooler control circuit of a constant current source system according to an exemplary embodiment. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the technical solutions in one or more embodiments of this specification will be clearly and completely described below in conjunction with the drawings in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of them. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this document.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0031] like Figure 1 As shown, the embodiment of the present application provides a low-temperature drift and high-precision constant current circuit and constant current source system, including: a microcontroller unit, a thermistor sensor, a copper plate, a semiconductor cooling sheet, a protection circuit, a constant current circuit and a thermoelectric cooler control circuit.

[0032] The microcontroller unit is connected to the protection circuit, the constant current circuit and the thermoelectric cooler control circuit; the microcontroller unit is used to output control signals to the constant current circuit and the thermoelectric cooler control circuit; the thermoelectric cooler control circuit is connected to the semiconductor cooling sheet; the semiconductor cooling sheet is applied with the thermal grease and then adhered to one side of the copper plate; the other side of the copper plate is adhered to the sampling resistor in the constant current circuit; the sampling resistor is applied with the thermal grease; one end of the thermistor sensor is connected to the copper plate, and the other end is connected to the microcontroller unit, and the thermistor sensor is used to collect the temperature of the copper plate and transmit it to the microcontroller unit.

[0033] Specifically, first install the semiconductor cooling chip (TEC) under a copper plate, apply a layer of thermal conductive silicone grease on the surface of TEC to increase the contact area between TEC and the copper plate and the cooling effect on the sampling resistor on the copper plate. Then apply a layer of thermal conductive silicone grease on the back of the sampling resistor and install it on the copper plate, and fix the sampling resistor and the copper plate with screws. Secondly, install a thermistor sensor (NTC temperature sensor) near the copper plate and the sampling resistor. The NTC temperature sensor will collect the temperature of the sampling resistor heat transferred to the copper plate, and feed back the temperature feedback signal to the microcontroller unit (MCU). The MCU judges the temperature signal. If the temperature is greater than 25℃, the MCU will send a cooling signal to dynamically increase the current of the TEC and reduce the temperature on the copper plate. Due to the good thermal conductivity of the copper plate, the heat of the sampling resistor can be taken away, so that the temperature of the sampling resistor is controlled to 25℃. When the temperature feedback from the NTC temperature sensor reaches 25℃, the output current of the TEC cooling chip will tend to a stable value. After the temperature of the sampling resistor is constant, the resistance value of the sampling resistor will not drift with temperature, so that a low temperature drift and high precision constant current source can be achieved.

[0034] The constant current circuit comprises an output control circuit, wherein the output control circuit comprises a plurality of field effect tubes and a plurality of sampling resistors; the field effect tubes are connected in parallel; and the sampling resistors are connected in parallel.

[0035] In the prior art, since the sampling resistor and the field effect tube are heat generating devices, using them in series will cause the ambient temperature to rise, which will in turn affect the inaccurate resistance of the sampling resistor and the accuracy of the output current of the constant current source. In this application, the field effect tube and the sampling resistor are connected in parallel to improve the energy efficiency of the circuit and reduce the overheating of the single field effect tube. For example, when two elements with the same resistance are connected in series, the current passing through is I, and the power is P=I 2 R, the current after parallel shunting is Power The power is reduced and the problem of component heating is solved to a certain extent.

[0036] Furthermore, the protection circuit comprises:

[0037] Power supply, capacitor 2C4, capacitor 2C5, capacitor 6C19 and capacitor 6C20; the capacitor 2C4 and the capacitor 2C5 are connected in parallel, one end of which is connected to the power supply and the other end is grounded; the capacitor 6C19 and the capacitor 6C20 are connected in parallel, one end of which is connected to the power supply and the other end is grounded. The protection circuit is used to prevent static input.

[0038] like Figure 2 As shown, the constant current circuit comprises:

[0039] Digital-to-analog conversion chip, filter circuit, push-pull drive circuit and output control circuit.

[0040] The output end of the digital-to-analog conversion chip is connected to the first input end of the filter circuit; the output end of the filter circuit is connected to one end of the push-pull drive circuit; the other end of the push-pull drive circuit is connected to the output control circuit; the other end of the output control circuit is connected to the second input end of the filter circuit.

[0041] The digital-to-analog conversion chip is MS5541.

[0042] MS5541 is a single-channel, 16-bit, serial input, voltage output digital-to-analog converter. It uses a single 5V power supply at the VOUT pin, and the output voltage range is 0V to VREF. By adjusting the internal parameters of the digital-to-analog conversion chip, the digital-to-analog conversion chip is set to a reference source with a maximum output of 3.3V. MS5541 has low power consumption, can provide unbuffered voltage output, has a low settling time characteristic, can ensure low output noise and low burrs, improves the stability of the output signal, and provides a stable input signal for a low temperature drift, high-precision constant current source. The stability of the output signal also preliminarily guarantees the stability of the output current of the constant current source.

[0043] The AGND pin of the MS5541 digital-to-analog conversion chip is grounded, the REF pin is connected to one end of the resistor 2R35, and the other end of the resistor 2R35 is connected to DIN, the CS# pin is connected to one end of the resistor 2R36, and the other end of the resistor 2R36 is connected to SCLK, the VDD pin is connected to one end of the capacitor 2C6 and one end of the resistor 2R1 in the filter circuit, and the other end of the capacitor 2C6 is grounded, the DGND pin is grounded, the DIN pin is connected to VREF and one end of the capacitor 2C32, and the other end of the capacitor 2C32 is grounded. The SCLK pin is connected to one end of the resistor 2R37 and one end of the resistor 2R17, and the other end of the resistor 2R37 is connected to CS1, and the other end of the resistor 2R17 is connected to the power supply.

[0044] The filtering circuit comprises:

[0045] Resistor 2R1, resistor 2R2, resistor 2R6, resistor 2R7, resistor 2R8, operational amplifier 2U2B, operational amplifier 2U3B, capacitor 2C40, shutdown pin and capacitor 2C41;

[0046] One end of the resistor 2R1 is connected to the VDD end of the digital-to-analog conversion chip, and the other end is connected to the in-phase input end of the operational amplifier 2U2B; the reverse input end of the operational amplifier 2U2B is connected to one end of the resistor 2R2; the other end of the resistor 2R2 is connected to the output end of the operational amplifier 2U2B and one end of the resistor 2R6;

[0047] The other end of the resistor 2R6 is connected to one end of the resistor 2R7, one end of the capacitor 2C40 and the non-inverting input end of the operational amplifier 2U3B; the other end of the resistor 2R7 and the other end of the capacitor 2C40 are grounded; the reverse input end of the operational amplifier 2U3B is connected to the output control circuit (I_F), one end of the resistor 2R8 and the shutdown pin (Shut); the other end of the resistor 2R8 is connected to one end of the capacitor 2C41; the other end of the capacitor 2C41 is connected to the output end of the operational amplifier 2U3B and the push-pull drive circuit. The first input end of the filter circuit is the non-inverting input end of the operational amplifier 2U2B, and the second input end of the filter circuit is the reverse input end of the operational amplifier 2U3B.

[0048] Since the maximum output voltage of the digital-to-analog conversion chip is 3.3V, the maximum output voltage of the output end of the operational amplifier 2U2B is 3.3V. At the output end of the operational amplifier 2U2B, two resistors are connected in series, the resistor 2R7 is 3KΩ, and the other resistor 2R6 is 15KΩ, to form a voltage divider circuit. When the output voltage of the operational amplifier 2U2B is 3.3V, the voltage across the 3KΩ resistor is 0.55V. A 0.1uF capacitor 2C40 is connected in parallel to filter the voltage signal output by the operational amplifier 2U2B. ​​The operational amplifier 2U3B and the operational amplifier 2U2B are connected to form a negative feedback circuit. When the power is initially turned on, the signal at the reverse input end of the operational amplifier 2U3B is 0V, but there is a voltage signal at the in-phase input end. At this time, the operational amplifier 2U3B outputs a high level.

[0049] The push-pull driving circuit comprises:

[0050] Resistor 2R9, common base transistor 2Q2 and common base transistor 2Q1;

[0051] One end of the resistor 2R9 is connected to the filter circuit, and the other end is connected to the base of the common base transistor 2Q1 and the base of the common base transistor 2Q2; the collector of the common base transistor 2Q1 is connected to electricity; the emitter of the common base transistor 2Q1 is connected to the emitter of the common base transistor 2Q2 and the output control circuit; the collector of the common base transistor 2Q2 is grounded.

[0052] The operational amplifier 2U3B outputs a high level, which is turned on by the push-pull driving circuit 2Q1 and turned off by 2Q2, and the high level is output to the gate of the field effect tube.

[0053] The output control circuit comprises:

[0054] Field effect transistor 2N2, field effect transistor 2N1, Zener diode, resistor 2R13, resistor 2R11, resistor 2R15, resistor 2R16, capacitor 2C35, sampling resistor 2R59, sampling resistor 2R60 and laser module; one end of the Zener diode is grounded, and the other end is connected to the push-pull drive circuit, one end of the resistor 2R11 and one end of the resistor 2R13;

[0055] The other end of the resistor 2R13 is connected to the gate of the field effect tube 2N2 and one end of the resistor 2R15; the other end of the resistor 2R15 is grounded; the source of the field effect tube 2N2 is connected to the filter circuit, the capacitor 2C35, the sampling resistor 2R59 and one end of the sampling resistor 2R60; the other ends of the capacitor 2C35, the sampling resistor 2R59 and the sampling resistor 2R60 are grounded; the drain of the field effect tube 2N2 is connected to the laser module;

[0056] The other end of the resistor 2R11 is connected to the gate of the field effect tube 2N1 and one end of the resistor 2R16; the other end of the resistor 2R16 is grounded; the source of the field effect tube 2N1 is connected to the filter circuit, the capacitor 2C35, the sampling resistor 2R59 and one end of the sampling resistor 2R60; the other ends of the capacitor 2C35, the sampling resistor 2R59 and the sampling resistor 2R60 are grounded; the drain of the field effect tube 2N1 is connected to the laser module.

[0057] A resistor is connected in series with the gate of the field effect tube to limit the gate overshoot current. The drain of the field effect tube is connected to the load end. Since the power supply voltage and current of the load are large, the electric power of the field effect tube itself will be large. Therefore, in the circuit of the present application, two field effect tubes are connected in parallel to divide the electric power, so that the electric power of the field effect tube is reduced and the heat generation is reduced, and the life and working capacity of the field effect tube element are also improved. Because a low temperature drift and high-precision constant current circuit is to be realized, the field effect tube UGS>UDS(OFF), and the field effect tube can only work in the constant current area at this time. Because the power supply end of the load is not powered before power-on and the source of the field effect tube is connected in series with the sampling resistor, UDS(OFF)=0; when the gate has a very small voltage, the field effect tube will work in the constant current area. When the field effect tube is turned on, the voltage of the sampling resistor will be fed back to the inverting input end of the operational amplifier 2U3B. When the voltage of the in-phase input end and the inverting input end of the operational amplifier 2U3B is infinitely close, the output current of the field effect tube tends to be stable.

[0058] like Figure 3 As shown, the thermoelectric cooler control circuit includes:

[0059] A power supply circuit, a drive circuit chip and a constant current circuit; the output end of the drive circuit chip is connected to one end of the constant current circuit, and the other end of the constant current circuit is connected to the input end of the power supply circuit.

[0060] The driving circuit chip comprises:

[0061] The first drive circuit chip and the second drive circuit chip; the first drive circuit chip and the second drive circuit chip are FD2203; the FD2203 chip is a half-bridge gate drive circuit chip with built-in input signal filtering, which can drive N-type power field effect transistors at high speed.

[0062] The chip pin VCC of the first driving circuit chip FD2203 is connected to the power supply and one end of the diode 6D7, the pin Him is connected to EN1A1 and one end of the resistor 6R19, the other end of the resistor 6R19 is connected to the node PWM1, the pin Lim is connected to EN1A1 and one end of the diode 6D8, the other end of the diode 6D8 is connected to EN1A, the pin COM is grounded, the pin VB is connected to the other end of the diode 6D7 and one end of the capacitor 6C21, the pin HO is connected to one end of the resistor 6R6 and one end of the resistor 6R5 in the current constant circuit, the pin VS is connected to the other end of the capacitor 6C21 and the resistor 6R7, the source of the field effect transistor 6N1, the drain of the field effect transistor 6N2 and the first input end of the power supply circuit in the current constant circuit, and the pin LO is connected to one end of the resistor 6R8 and one end of the resistor 6R9 in the current constant circuit.

[0063] The chip pin VCC of the second driving circuit chip FD2203 is connected to the power supply and one end of the diode 6D10, the pin Him is connected to EN1A1 and one end of the resistor 6R22, the other end of the resistor 6R22 is connected to the node PWM1, the pin Lim is connected to EN1A1 and one end of the diode 6D11, the other end of the diode 6D11 is connected to EN1B, the pin COM is grounded, the pin VB is connected to the other end of the diode 6D10 and one end of the capacitor 6C24, the pin HO is connected to one end of the resistor 6R11 and one end of the resistor 6R12 in the current constant circuit, the pin VS is connected to the other end of the capacitor 6C24 and the resistor 6R13, the source of the field effect transistor 6N3, the drain of the field effect transistor 6N4 and the second input end of the power supply circuit in the current constant circuit, and the pin LO is connected to one end of the resistor 6R14 and one end of the resistor 6R15 in the current constant circuit.

[0064] The current constant circuit comprises:

[0065] A first branch and a second branch; the first drive circuit chip is connected to one end of the first branch; the other end of the first branch is connected to the first input end of the power supply circuit; the second input end of the power supply circuit is connected to one end of the second branch; the other end of the second branch is connected to the second drive circuit chip.

[0066] The first branch comprises:

[0067] Resistor 6R6, resistor 6R5, resistor 6R9, ​​diode 6D1, diode 6D2, field effect transistor 6N1, field effect transistor 6N2, power supply, current terminal ISEN1;

[0068] One end of the resistor 6R5 is connected to the HO end of the first drive circuit chip and one end of the resistor 6R6, and the other end is connected to one end of the diode 6D1, the gate of the field effect transistor 6N1, the VS end of the first drive circuit chip, the source of the field effect transistor 6N1, the drain of the field effect transistor 6N2 and the first input end of the power supply circuit; the other end of the resistor 6R6 is connected to the other end of the diode 6D1; the drain of the field effect transistor 6N1 is connected to the power supply;

[0069] One end of the resistor 6R8 is connected to the LO end of the first drive circuit chip and one end of the resistor 6R9, ​​and the other end is connected to one end of the diode 6D2, the gate of the field effect transistor 6N2, the source of the field effect transistor 6N2 and the current end ISEN1; the other end of the resistor 6R9 is connected to the other end of the diode 6D2; the other end of the resistor 6R10.

[0070] The second branch comprises:

[0071] Resistor 6R11, resistor 6R12, resistor 6R14, resistor 6R15, diode 6D3, diode 6D4, field effect transistor 6N3, field effect transistor 6N4, power supply and current terminal ISEN1;

[0072] One end of the resistor 6R11 is connected to the HO end of the second drive circuit chip and one end of the resistor 6R12, and the other end is connected to one end of the diode 6D3, the gate of the field effect transistor 6N3, the VS end of the second drive circuit chip, the source of the field effect transistor 6N3, the drain of the field effect transistor 6N4 and the second input end of the power supply circuit; the other end of the resistor 6R12 is connected to the other end of the diode 6D3; the drain of the field effect transistor 6N3 is connected to the power supply;

[0073] One end of the resistor 6R14 is connected to the LO end of the second drive circuit chip and one end of the resistor 6R15, and the other end is connected to one end of the diode 6D4, the gate of the field effect transistor 6N4, the source of the field effect transistor 6N4 and the current end ISEN1; the other end of the resistor 6R15 is connected to the other end of the diode 6D4.

[0074] In the embodiment of the present application, when the temperature of the sampling resistor is too high, the microcontroller unit (MCU) sends a cooling enable signal, and the FD2203 driver chip is turned on at this time, and two voltage signals are output. The two voltage signals drive the field effect tube 6N1 and the field effect tube 6N2 respectively. Since the two voltage signals input to the field effect tube are different, the field effect tube 6N1 and the field effect tube 6N2 are in opposite states, that is, 6N1 is turned on and 6N2 is turned off; 6N1 is turned off and 6N2 is turned on. When 6N1 is turned on and 6N2 is turned off, the TEC is powered and 6L1 is charged; when 6N1 is turned off and 6N2 is turned on, due to the charging of the inductor 6L1, the current flows from the source of the field effect tube 6N2 to the drain, and the TEC is powered. Due to the switching characteristics of the field effect tube 6N1 and the field effect tube 6N2, the power supply current of the TEC is kept constant, so as to realize the temperature control of the sampling resistor.

[0075] Through the DC / DC synchronous rectification circuit, the switching characteristics of the field effect tube are used to control the TEC heating or cooling function; by increasing the power supply current of the TEC cooling plate, the cooling efficiency of the TEC cooling plate will also be improved; by increasing the power supply current of the TEC heating plate, the heating efficiency of the TEC heating plate will also be improved, thereby achieving constant temperature control of the temperature of the sampling resistor.

[0076] The power supply circuit includes:

[0077] Inductor 6L1, inductor 6L2, sampling resistor 6R25, capacitor 6C25, capacitor 6C11, capacitor 6C12, capacitor 6C13, capacitor 6C14, capacitor 6C10, capacitor 6C7, polarized capacitor 6C5, polarized capacitor 6C6, polarized capacitor 6C8, polarized capacitor 6C9 and ISEN1. The first input terminal of the power supply circuit is inductor 6L1, and the first input terminal of the power supply circuit is inductor 6L2.

[0078] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A low temperature drift and high precision constant current circuit, characterized in that: The constant current circuit includes a digital-to-analog conversion chip, a filter circuit, a push-pull drive circuit and an output control circuit, wherein the output end of the digital-to-analog conversion chip is connected to the first input end of the filter circuit; the output end of the filter circuit is connected to one end of the push-pull drive circuit; the other end of the push-pull drive circuit is connected to the output control circuit; the other end of the output control circuit is connected to the second input end of the filter circuit; The output control circuit includes a plurality of field effect tubes and a plurality of sampling resistors; the field effect tubes are connected in parallel; and the sampling resistors are connected in parallel.

2. The circuit according to claim 1, characterized in that The output control circuit includes a field effect transistor 2N2, a field effect transistor 2N1, a Zener diode, a resistor 2R13, a resistor 2R11, a resistor 2R15, a resistor 2R16, a capacitor 2C35, a sampling resistor 2R59, a sampling resistor 2R60 and a laser module; one end of the Zener diode is grounded, and the other end is connected to the push-pull drive circuit, one end of the resistor 2R11 and one end of the resistor 2R13; The other end of the resistor 2R13 is connected to the gate of the field effect tube 2N2 and one end of the resistor 2R15; the other end of the resistor 2R15 is grounded; the source of the field effect tube 2N2 is connected to the filter circuit, the capacitor 2C35, the sampling resistor 2R59 and one end of the sampling resistor 2R60; the other ends of the capacitor 2C35, the sampling resistor 2R59 and the sampling resistor 2R60 are grounded; the drain of the field effect tube 2N2 is connected to the laser module; The other end of the resistor 2R11 is connected to the gate of the field effect tube 2N1 and one end of the resistor 2R16; the other end of the resistor 2R16 is grounded; the source of the field effect tube 2N1 is connected to the filter circuit, the capacitor 2C35, the sampling resistor 2R59 and one end of the sampling resistor 2R60; the other ends of the capacitor 2C35, the sampling resistor 2R59 and the sampling resistor 2R60 are grounded; the drain of the field effect tube 2N1 is connected to the laser module.

3. The circuit according to claim 2, characterized in that The filtering circuit comprises: Resistor 2R1, resistor 2R2, resistor 2R6, resistor 2R7, resistor 2R8, operational amplifier 2U2B, operational amplifier 2U3B, capacitor 2C40, shutdown pin and capacitor 2C41; One end of the resistor 2R1 is connected to the VDD end of the digital-to-analog conversion chip, and the other end is connected to the in-phase input end of the operational amplifier 2U2B; the reverse input end of the operational amplifier 2U2B is connected to one end of the resistor 2R2; the other end of the resistor 2R2 is connected to the output end of the operational amplifier 2U2B and one end of the resistor 2R6; The other end of the resistor 2R6 is connected to one end of the resistor 2R7, one end of the capacitor 2C40 and the common-mode input end of the operational amplifier 2U3B; the other end of the resistor 2R7 and the other end of the capacitor 2C40 are grounded; the reverse input end of the operational amplifier 2U3B is connected to the output control circuit, one end of the resistor 2R8 and the shutdown pin; the other end of the resistor 2R8 is connected to one end of the capacitor 2C41; the other end of the capacitor 2C41 is connected to the output end of the operational amplifier 2U3B and the push-pull drive circuit.

4. The circuit according to claim 2, characterized in that The digital-to-analog conversion chip is MS5541; The push-pull driving circuit comprises: Resistor 2R9, common base transistor 2Q2 and common base transistor 2Q1; One end of the resistor 2R9 is connected to the filter circuit, and the other end is connected to the base of the common base transistor 2Q1 and the base of the common base transistor 2Q2; the collector of the common base transistor 2Q1 is connected to electricity; the emitter of the common base transistor 2Q1 is connected to the emitter of the common base transistor 2Q2 and the output control circuit; the collector of the common base transistor 2Q2 is grounded.

5. A constant current source system, characterized in that: include: A microcontroller unit, a thermistor sensor, a copper plate, a semiconductor cooling sheet, a protection circuit, a thermoelectric cooler control circuit, and a constant current circuit as claimed in any one of claims 1 to 4; The microcontroller unit is connected to the protection circuit, the constant current circuit and the thermoelectric cooler control circuit; the microcontroller unit is used to output control signals to the constant current circuit and the thermoelectric cooler control circuit; the thermoelectric cooler control circuit is connected to the semiconductor cooling sheet; the semiconductor cooling sheet is applied with thermal grease and is attached to one side of the copper plate; the other side of the copper plate is attached to the sampling resistor in the constant current circuit; the sampling resistor is applied with the thermal grease; one end of the thermistor sensor is connected to the copper plate, and the other end is connected to the microcontroller unit, and the thermistor sensor is used to collect the temperature of the copper plate and transmit it to the microcontroller unit.

6. The system according to claim 5, characterized in that The thermoelectric cooler control circuit includes a power supply circuit, a drive circuit chip and a current constant circuit; the output end of the drive circuit chip is connected to one end of the current constant circuit, and the other end of the current constant circuit is connected to the input end of the power supply circuit.

7. The system according to claim 6, characterized in that The constant current circuit comprises a first branch and a second branch; The driving circuit chip includes a first driving circuit chip and a second driving circuit chip; the first driving circuit chip and the second driving circuit chip are FD2203; The first drive circuit chip is connected to one end of the first branch; the other end of the first branch is connected to the first input end of the power supply circuit; the second input end of the power supply circuit is connected to one end of the second branch; the other end of the second branch is connected to the second drive circuit chip.

8. The system according to claim 7, characterized in that The first branch comprises: Resistor 6R6, resistor 6R5, resistor 6R9, ​​diode 6D1, diode 6D2, field effect transistor 6N1, field effect transistor 6N2, power supply, current terminal ISEN1; One end of the resistor 6R5 is connected to the HO end of the first drive circuit chip and one end of the resistor 6R6, and the other end is connected to one end of the diode 6D1, the gate of the field effect transistor 6N1, the VS end of the first drive circuit chip, the source of the field effect transistor 6N1, the drain of the field effect transistor 6N2 and the first input end of the power supply circuit; the other end of the resistor 6R6 is connected to the other end of the diode 6D1; the drain of the field effect transistor 6N1 is connected to the power supply; One end of the resistor 6R8 is connected to the LO end of the first drive circuit chip and one end of the resistor 6R9, ​​and the other end is connected to one end of the diode 6D2, the gate of the field effect transistor 6N2, the source of the field effect transistor 6N2 and the current end ISEN1; the other end of the resistor 6R9 is connected to the other end of the diode 6D2; the other end of the resistor 6R10.

9. The system according to claim 8, characterized in that The second branch comprises: Resistor 6R11, resistor 6R12, resistor 6R14, resistor 6R15, diode 6D3, diode 6D4, field effect transistor 6N3, field effect transistor 6N4, power supply and current terminal ISEN1; One end of the resistor 6R11 is connected to the HO end of the second drive circuit chip and one end of the resistor 6R12, and the other end is connected to one end of the diode 6D3, the gate of the field effect transistor 6N3, the VS end of the second drive circuit chip, the source of the field effect transistor 6N3, the drain of the field effect transistor 6N4 and the second input end of the power supply circuit; the other end of the resistor 6R12 is connected to the other end of the diode 6D3; the drain of the field effect transistor 6N3 is connected to the power supply; One end of the resistor 6R14 is connected to the LO end of the second drive circuit chip and one end of the resistor 6R15, and the other end is connected to one end of the diode 6D4, the gate of the field effect transistor 6N4, the source of the field effect transistor 6N4 and the current end ISEN1; the other end of the resistor 6R15 is connected to the other end of the diode 6D4.

10. The system according to claim 5, characterized in that The protection circuit includes a power supply, a capacitor 2C4, a capacitor 2C5, a capacitor 6C19 and a capacitor 6C20; after the capacitor 2C4 and the capacitor 2C5 are connected in parallel, one end is connected to the power supply and the other end is grounded; after the capacitor 6C19 and the capacitor 6C20 are connected in parallel, one end is connected to the power supply and the other end is grounded.

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