High-stability current source circuit

Abstract

The invention discloses a high-stability current source circuit, which comprises a digital-to-analog conversion control part, a driving output part and a feedback loop part, and is characterized in that the digital-to-analog conversion control part comprises a main control chip circuit and a digital-to-analog conversion circuit; the driving output part comprises an operational amplifier driving circuit, a triode output circuit and a bridge type direction switching circuit; the main control chip circuit controls the digital-to-analog conversion circuit and outputs stable control voltage, the output end of the digital-to-analog conversion circuit is connected to the input end of the triode output circuit through the operational amplifier driving circuit, and the output end of the triode output circuit outputs real-time voltage at the two ends of a load through the bridge type direction switching circuit. The input end of the feedback loop part is connected to the bridge type direction switching circuit and is used for acquiring a sampling signal; the output end of the feedback loop part and the output end of the bridge type direction switching circuit are connected to the input end of the main control chip circuit. According to the embodiment of the invention, the stability and reliability of the current source circuit can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of special power supplies, and specifically relates to a high-stability current source circuit, which can meet the needs of high power, large current, high stability and high precision, and can be assembled in special equipment such as an electron microscope. Background Art

[0002] At present, the main current sources in China all have set maximum output current, output accuracy and minimum current resolution indicators. They are all commercial current sources and have no requirements for their output stability and ripple. However, in high-precision equipment, the required current source indicators are very high. They must have high accuracy, high stability, and high resolution. The load regulation rate, temperature drift, ripple, power supply regulation rate and response time are extremely low to meet the needs of places with high output demands. Summary of the invention

[0003] The purpose of the present invention is to provide a high-stability current source circuit, which can adjust the output current by adjusting the output of the digital-to-analog conversion circuit through the main control chip circuit to achieve the highest efficiency of the current source, and at the same time adopts high-precision and low-temperature drift sampling resistors for feedback, and uses high-precision operational amplifiers for driving and reading back, thereby increasing the stability and reliability of the circuit.

[0004] To achieve the above-mentioned purpose, the embodiment of the present invention discloses a high-stability current source circuit, which includes a digital-to-analog conversion control part, a drive output part, and a feedback loop part, wherein the digital-to-analog conversion control part includes a main control chip circuit and a digital-to-analog conversion circuit; the drive output part includes an operational amplifier drive circuit, a triode output circuit, and a bridge direction switching circuit;

[0005] The main control chip circuit controls the digital-to-analog conversion circuit, outputs a stable control voltage, and provides a constant driving signal for the driving output part. The output end of the digital-to-analog conversion circuit is connected to the input end of the triode output circuit through an operational amplifier driving circuit. The output end of the triode output circuit outputs the real-time voltage across the load through the bridge direction switching circuit.

[0006] The input end of the feedback loop part is connected to the bridge direction switching circuit for obtaining a sampling signal; the output end of the feedback loop part and the output end of the bridge direction switching circuit are both connected to the input end of the main control chip circuit for comparing the sampling signal with the real-time voltage signal to control the dynamic compensation drive signal of the digital-to-analog conversion circuit.

[0007] As an optional embodiment, in the present invention, the main control chip circuit is a microprocessor chip, the output end of the microprocessor chip is connected to the input end of the digital-to-analog conversion circuit, and the input end of the microprocessor chip is respectively connected to the output end of the feedback loop part and the output end of the bridge direction switching circuit.

[0008] As an optional embodiment, in the present invention, the digital-to-analog conversion circuit includes a first digital-to-analog converter, a second digital-to-analog converter, a reference voltage circuit, and a first conditioning circuit and a second conditioning circuit. The microprocessor chip has a first output terminal and a second output terminal. The first output terminal of the microprocessor chip is connected to the input terminal of the first digital-to-analog converter, and the second output terminal of the microprocessor chip is connected to the input terminal of the second digital-to-analog converter. The reference voltage terminals of the first digital-to-analog converter and the second digital-to-analog converter are both connected to the output terminal of the reference voltage circuit. The output terminal of the first digital-to-analog converter and the output terminal of the second digital-to-analog converter are respectively connected to the input terminal of the operational amplifier driving circuit through the first conditioning circuit and the second conditioning circuit.

[0009] As an optional embodiment, in the present invention, the reference voltage circuit includes a reference voltage source, a resistor R150, a capacitor C65, an amplifier U21B, a resistor R118, a resistor R128, a capacitor C502, an amplifier U22A, and resistors R105, R125, and R140; wherein the output end of the reference voltage source is connected to the non-inverting input end of the amplifier U21B through the resistor R150, the inverting input end of the amplifier U21B is connected to the output end of the amplifier U21B, and the output end of the amplifier U21B is also connected to the reference voltage end of the first digital-to-analog converter and the second digital-to-analog converter; the resistors R105, R125, and R140 are connected in series. One end of the resistor R105, the resistor R125 and the resistor R140 are connected in series and connected to the output end of the amplifier U22A. The non-inverting input end of the amplifier U22A is grounded. The inverting input end of the amplifier U22A is connected to the output end of the amplifier U22A through a resistor R128. The inverting input end of the amplifier U22A is also connected to the output end of the amplifier U21B through a resistor R118. One end of the capacitor C65 is connected between the resistor R150 and the non-inverting input end of the amplifier U21B, and the other end of the capacitor C65 is grounded. The capacitor C502 is connected across the resistor R128.

[0010] As an optional implementation, in the present invention, the first conditioning circuit includes a capacitor C45, a capacitor C51, an amplifier U24A, and a resistor R103, and the second conditioning circuit includes an amplifier U24B, a capacitor C67, a resistor R104, a resistor R126, and a resistor R141; one end of the capacitor C45 is connected between the output end of the first digital-to-analog converter and the inverting input end of the amplifier U24A, and the other end of the capacitor C45 is connected between the feedback end of the first digital-to-analog converter and the output end of the amplifier U24A, and the output end of the amplifier U24A is also connected to the operation end through the resistor R103. The input end of the operational amplifier driving circuit, the non-inverting input end of the amplifier U24A is grounded, and the capacitor C51 is connected across the two ends of the capacitor C45; one end of the capacitor C67 is connected between the output end of the second digital-to-analog converter and the inverting input end of the amplifier U24B, and the other end of the capacitor C67 is connected between the feedback end of the second digital-to-analog converter and the output end of the amplifier U24B, the output end of the amplifier U24B is also connected to the input end of the operational amplifier driving circuit through a series resistor R104, a resistor R126 and a resistor R141, and the non-inverting input end of the amplifier U24B is grounded.

[0011] As an optional implementation, in the present invention, a signal isolation circuit is further provided between the main control chip circuit and the digital-to-analog conversion circuit.

[0012] As an optional implementation, in the present invention, the operational amplifier driving circuit includes a resistor R106, an amplifier U22B, a capacitor C532, a resistor chip, an amplifier U26, a resistor R154, a capacitor C52, a resistor R138, a resistor R143, a resistor R152, a resistor R153, a resistor R151 and a capacitor C69; the transistor output circuit includes an NMOS tube Q16, and the feedback loop part includes a sampling resistor R1143;

[0013] The output end of the digital-to-analog conversion circuit is connected to the positive input end of the amplifier U22B through the resistor R106, the inverting input end of the amplifier U22B is connected to the output end of the amplifier U22B, the output end of the amplifier U22B is also connected to the inverting input end of the amplifier U26 through the resistor chip, the inverting input end of the amplifier U26 is connected to the output end of the amplifier U26 through the capacitor C52, and the output end of the amplifier U26 is also connected to the NMOS The gate of the NMOS tube Q16, the drain of the NMOS tube Q16 is connected to the bridge direction switching circuit, the source of the NMOS tube Q16 is connected to the non-inverting input terminal of the amplifier U26 through the sampling resistor R1143, and the two ends of the resistor R143 and the resistor R152 after being connected in parallel are respectively connected to the sampling resistor R1143 and the non-inverting input terminal of the amplifier U26; one end of the resistor R154 is grounded, and the other end of the resistor R154 is connected between the gate of the NMOS tube Q16 and the output terminal of the amplifier U26.

[0014] As an optional embodiment, in the present invention, the bridge direction switching circuit includes a polarity switching circuit and a power conversion circuit, the output end of the polarity switching circuit is connected to the control end of the power conversion circuit, the input end of the power conversion circuit is connected to the output end of the operational amplifier driving circuit, the output end of the power conversion circuit forms an output circuit, and the power conversion circuit is also connected to the input end of the feedback loop part.

[0015] As an optional implementation, in the present invention, the polarity switching circuit includes a PWM generator, a resistor R16, a resistor R15, an NMOS tube Q4, an isolation chip U5, a resistor R73, a resistor R72, an NMOS tube Q15, an isolation chip U17, a resistor R53, a resistor R52, an NMOS tube Q12, an isolation chip U13, a resistor R27, a resistor R26, an NMOS tube Q10 and an isolation chip U11; the power conversion circuit includes an NMOS tube U3, an NMOS tube U9, an NMOS tube U2 and an NMOS tube U10;

[0016] The first output terminal of the PWM generator is connected to the gate of the NMOS tube Q4 through the resistor R16, the source of the NMOS tube Q4 is grounded, the drain of the NMOS tube Q4 is connected to the input terminal of the isolation chip U5, and the output terminal of the isolation chip U5 is connected to the gate of the NMOS tube U3;

[0017] The first output end of the PWM generator is connected to the gate of the NMOS tube Q4 through the resistor R16, the source of the NMOS tube Q4 is grounded, the drain of the NMOS tube Q4 is connected to the input end of the isolation chip U5, the output end of the isolation chip U5 is connected to the gate of the NMOS tube U3, one end of the resistor R15 is grounded, and the other end of the resistor R15 is connected between the source of the NMOS tube Q4 and the resistor R16;

[0018] The second output end of the PWM generator is connected to the gate of the NMOS tube Q12 through the resistor R53, the source of the NMOS tube Q12 is grounded, the drain of the NMOS tube Q12 is connected to the input end of the isolation chip U13, the output end of the isolation chip U13 is connected to the gate of the NMOS tube U2, one end of the resistor R52 is grounded, and the other end of the resistor R52 is connected between the source of the NMOS tube Q12 and the resistor R53;

[0019] The third output terminal of the PWM generator is connected to the gate of the NMOS tube Q15 through the resistor R73, the source of the NMOS tube Q15 is grounded, the drain of the NMOS tube Q15 is connected to the input terminal of the isolation chip U17, the output terminal of the isolation chip U17 is connected to the gate of the NMOS tube U9, one end of the resistor R72 is grounded, and the other end of the resistor R72 is connected between the source of the NMOS tube Q15 and the resistor R73;

[0020] The fourth output terminal of the PWM generator is connected to the gate of the NMOS tube Q10 through the resistor R27, the source of the NMOS tube Q10 is grounded, the drain of the NMOS tube Q10 is connected to the input terminal of the isolation chip U11, the output terminal of the isolation chip U11 is connected to the gate of the NMOS tube U10, one end of the resistor R26 is grounded, and the other end of the resistor R26 is connected between the source of the NMOS tube Q10 and the resistor R27;

[0021] The source of the NMOS tube U3 is connected to the drain of the NMOS tube U9, the source of the NMOS tube U2 is connected to the drain of the NMOS tube U10, the source of the NMOS tube U3 and the drain of the NMOS tube U9 form a first output end of the output circuit, and the source of the NMOS tube U2 and the drain of the NMOS tube U10 form a second output end of the output circuit; the drains of the NMOS tube U3 and the NMOS tube U2 are both connected to the auxiliary power supply;

[0022] The source of the NMOS transistor U9 and the source of the NMOS transistor U10 are both connected to the drain of the NMOS transistor Q16.

[0023] As an optional implementation, in the present invention, the feedback loop part further includes a sampling signal processing circuit, and the sampling signal processing circuit includes a first processing circuit, a second processing circuit and a third processing circuit;

[0024] The first processing circuit includes a resistor R484, a resistor R17, a resistor R6 and an amplifier U6B; the second processing circuit includes a resistor R443, a resistor R29, a resistor R42 and an amplifier U6A; the third processing circuit includes an amplifier U4A and a resistor R464;

[0025] The first output end of the output circuit is connected to the non-inverting input end of the amplifier U6B through a resistor R484, the inverting input end of the amplifier U6B is connected to the output end of the amplifier U6B, the output end of the amplifier U6B is also connected to the first input end of the main control chip circuit through a resistor R17, one end of the resistor R6 is grounded, and the other end of the resistor R6 is connected between the first input end of the main control chip circuit and the resistor R17;

[0026] The second output end of the output circuit is connected to the non-inverting input end of the amplifier U6A through a resistor R443, the inverting input end of the amplifier U6A is connected to the output end of the amplifier U6A, the output end of the amplifier U6A is also connected to the second input end of the main control chip circuit through a resistor R29, one end of the resistor R42 is grounded, and the other end of the resistor R42 is connected between the second input end of the main control chip circuit and the resistor R29;

[0027] The non-inverting input terminal of the amplifier U4A is connected to the source of the NMOS tube Q16 through the sampling resistor R1143, the inverting input terminal of the amplifier U4A is connected to the output terminal of the amplifier U4A, and the output terminal of the amplifier U4A is connected to the third input terminal of the main control chip circuit through the resistor R464.

[0028] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0029] The present invention adjusts the output of the digital-to-analog conversion circuit through the main control chip circuit, and can adjust the output current to achieve the highest efficiency of the current source. At the same time, a high-precision, low-temperature drift sampling resistor is used for feedback, and a high-precision operational amplifier is used for driving and reading back, thereby increasing the stability and reliability of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural block diagram of a high stability current source circuit of the present invention;

[0031] Figure 2 For the present invention Figure 1 The circuit schematic diagram of the digital-to-analog conversion control part;

[0032] Figure 3 For the present invention Figure 1 The circuit schematic diagram of the drive output part;

[0033] Figure 4 For the present invention Figure 1 Circuit schematic of the feedback loop part. DETAILED DESCRIPTION

[0034] Below, in conjunction with the accompanying drawings and specific embodiments, the present invention is further described. It should be noted that, under the premise of no conflict, the various embodiments described below or the various technical features can be arbitrarily combined to form a new embodiment. Except for special instructions, the materials and equipment used in this embodiment can be purchased from the market. Examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0035] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In the description of the present application, "plurality" means two or more, unless otherwise precisely and specifically specified.

[0036] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be connected through an intermediary medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0037] The terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0038] Example

[0039] In order to solve the problem that the existing commercial current sources cannot meet the high precision, high stability, high resolution, load regulation, temperature drift, ripple, power regulation and extremely low response time, high stability and low ripple required by equipment such as electron microscopes, the present invention proposes a high stability current source circuit that can achieve excellent indicators through a unique circuit design and is applied to special equipment.

[0040] Please refer to Figure 1 As shown, a high stability current source circuit may include three major parts: a digital-to-analog conversion control part 10, a drive output part 20 and a feedback loop part 30, wherein the digital-to-analog conversion control part 10 includes a main control chip circuit 11 and a digital-to-analog conversion circuit 13; the drive output part 20 includes an operational amplifier drive circuit, a transistor output circuit and a bridge direction switching circuit.

[0041] Of course, it also includes the necessary power supply part, among which the power supply part mainly includes switching power supply circuit, linear power supply circuit and filtering protection circuit.

[0042] In an embodiment of the present invention, the main control chip circuit can be used to control the digital-to-analog conversion circuit to output a stable control voltage, supply a constant drive signal to the operational amplifier drive circuit, so that the circuit outputs a highly stable and high-precision current, and collect the sampling resistor voltage through the feedback loop part 30, dynamically compensate the drive signal, and keep the output current constant.

[0043] Specifically, the main control chip circuit controls the digital-to-analog conversion circuit to output a stable control voltage, and provides a constant driving signal for the driving output part. The output end of the digital-to-analog conversion circuit is connected to the input end of the triode output circuit through an operational amplifier driving circuit, and the output end of the triode output circuit outputs the real-time voltage across the load through the bridge direction switching circuit.

[0044] The input end of the feedback loop part is connected to the bridge direction switching circuit for obtaining a sampling signal; the output end of the feedback loop part and the output end of the bridge direction switching circuit are both connected to the input end of the main control chip circuit for comparing the sampling signal with the real-time voltage signal to control the dynamic compensation drive signal of the digital-to-analog conversion circuit.

[0045] Please refer to Figure 2 As shown, the main control chip circuit can adopt a microprocessor chip MCU, the output end of the microprocessor chip is connected to the input end of the digital-to-analog conversion circuit, and the input end of the microprocessor chip is respectively connected to the output end of the feedback loop part and the output end of the bridge direction switching circuit.

[0046] In the embodiment of the present invention, the bridge direction switching circuit has two output ends, which are the two ends of the load, plus the output signal of the feedback loop part. Therefore, the main control chip circuit, that is, the microprocessor chip, has three input ends, which are respectively recorded as the first input end, the second input end and the third input end.

[0047] A signal isolation circuit 12 can be provided between the digital-to-analog conversion circuit and the main control chip circuit to ensure signal purity. The signal isolation circuit can be implemented using isolation chips such as optocouplers.

[0048] The main control chip circuit issues control instructions to the entire circuit. After the main control chip circuit issues the instruction, it will pass through the isolation chip to ensure the purity of the signal.

[0049] The digital-to-analog conversion circuit may include a first digital-to-analog converter, a second digital-to-analog converter, a reference voltage circuit, and a first conditioning circuit and a second conditioning circuit. The microprocessor chip has a first output terminal and a second output terminal. The first output terminal of the microprocessor chip is connected to the input terminal of the first digital-to-analog converter, and the second output terminal of the microprocessor chip is connected to the input terminal of the second digital-to-analog converter. The reference voltage terminals of the first digital-to-analog converter and the second digital-to-analog converter are both connected to the output terminal of the reference voltage circuit. The output terminal of the first digital-to-analog converter and the output terminal of the second digital-to-analog converter are respectively connected to the input terminal of the operational amplifier driving circuit through the first conditioning circuit and the second conditioning circuit.

[0050] Specifically, the reference voltage circuit includes a reference voltage source, a resistor R150, a capacitor C65, an amplifier U21B, a resistor R118, a resistor R128, a capacitor C502, an amplifier U22A, and resistors R105, R125, and R140; wherein the output end of the reference voltage source is connected to the non-inverting input end of the amplifier U21B through the resistor R150, the inverting input end of the amplifier U21B is connected to the output end of the amplifier U21B, and the output end of the amplifier U21B is also connected to the reference voltage end of the first digital-to-analog converter and the second digital-to-analog converter; one end of the resistor R105, the resistor R125, and the resistor R140 connected in series is connected to the The input end of the operational amplifier driving circuit, the other end of the resistor R105, the resistor R125 and the resistor R140 connected in series is connected to the output end of the amplifier U22A, the non-inverting input end of the amplifier U22A is grounded, the inverting input end of the amplifier U22A is connected to the output end of the amplifier U22A through the resistor R128, the inverting input end of the amplifier U22A is also connected to the output end of the amplifier U21B through the resistor R118, one end of the capacitor C65 is connected between the resistor R150 and the non-inverting input end of the amplifier U21B, and the other end of the capacitor C65 is grounded; the capacitor C502 is connected across the two ends of the resistor R128.

[0051] The first conditioning circuit and the second conditioning circuit are actually feedback circuits, wherein the first conditioning circuit includes capacitor C45, capacitor C51, amplifier U24A, and resistor R103, and the second conditioning circuit includes amplifier U24B, capacitor C67, resistor R104, resistor R126, and resistor R141; one end of the capacitor C45 is connected between the output end of the first digital-to-analog converter and the inverting input end of the amplifier U24A, and the other end of the capacitor C45 is connected between the feedback end of the first digital-to-analog converter and the output end of the amplifier U24A, and the output end of the amplifier U24A is also connected to The input end of the operational amplifier driving circuit, the non-phase input end of the amplifier U24A is grounded, and the capacitor C51 is connected across the two ends of the capacitor C45; one end of the capacitor C67 is connected between the output end of the second digital-to-analog converter and the inverting input end of the amplifier U24B, and the other end of the capacitor C67 is connected between the feedback end of the second digital-to-analog converter and the output end of the amplifier U24B. The output end of the amplifier U24B is also connected to the input end of the operational amplifier driving circuit through a series-connected resistor R104, a resistor R126 and a resistor R141, and the non-phase input end of the amplifier U24B is grounded.

[0052] When the signal reaches the first digital-to-analog converter (U19) and the second digital-to-analog converter (U28), the first digital-to-analog converter (U19) and the second digital-to-analog converter (U28) will generate a voltage output of a corresponding range according to the reference voltage obtained by the power supply part (the above-mentioned reference voltage source is the output voltage of the power supply part). Here, two DACs are used in a mode of connecting two DACs in series through resistors, with one DAC as the main adjustment chip and the other DAC as the auxiliary adjustment chip, so that the step size of the voltage output can be smaller, thereby improving the accuracy of the circuit, and using multiple parallel outputs at the DAC output end can improve the accuracy of the output analog quantity and reduce the output noise.

[0053] After the output voltage is divided and integrated by the first conditioning circuit and the second conditioning circuit, a higher voltage output regulation can be achieved, providing the circuit with a high-resolution regulation function, and the use of multi-channel parallel output makes the output signal noise lower, ensuring that the final output current stability is higher.

[0054] Please refer to Figure 3As shown, the operational amplifier driving circuit may include a driving circuit 21 and an error comparison circuit 22, wherein the driving circuit 21 may include a resistor R106, an amplifier U22B, a capacitor C532, and a resistor chip; the error comparison circuit 22 may include an amplifier U26, a resistor R154, a capacitor C52, a resistor R138, a resistor R143, a resistor R152, a resistor R153, a resistor R151, and a capacitor C69; the transistor output circuit includes an NMOS transistor Q16 (the transistor output circuit uses a high-power MOS transistor that can withstand large current operation), and the feedback loop part includes a sampling resistor R1143.

[0055] Specifically, the output end of the digital-to-analog conversion circuit is connected to the positive input end of the amplifier U22B through the resistor R106, the inverting input end of the amplifier U22B is connected to the output end of the amplifier U22B, the output end of the amplifier U22B is also connected to the inverting input end of the amplifier U26 through the resistor chip, the inverting input end of the amplifier U26 is connected to the output end of the amplifier U26 through the capacitor C52, and the output end of the amplifier U26 is also connected to the NMOS The gate of the NMOS tube Q16, the drain of the NMOS tube Q16 is connected to the bridge direction switching circuit, the source of the NMOS tube Q16 is connected to the non-inverting input terminal of the amplifier U26 through the sampling resistor R1143, and the two ends of the resistor R143 and the resistor R152 after being connected in parallel are respectively connected to the sampling resistor R1143 and the non-inverting input terminal of the amplifier U26; one end of the resistor R154 is grounded, and the other end of the resistor R154 is connected between the gate of the NMOS tube Q16 and the output terminal of the amplifier U26.

[0056] The operational amplifier circuit uses a high-precision and high-uniformity resistor chip to form a circuit closed loop, which increases the accuracy of the circuit. The resistor chip U25 may include resistor R25A, resistor R25B, resistor R25C and resistor R25D, wherein the two ends of the resistor R25C and the resistor R25D after being connected in series are respectively connected to the output end of the amplifier R22B and the inverting input end of the amplifier U26, and the two ends of the resistor R25A and the resistor R25B after being connected in parallel are respectively connected to the inverting input end of the amplifier U26 and the sampling resistor R1143.

[0057] The bridge direction switching circuit uses a fast-response MOS tube to make the current direction switching rapid and increase the circuit performance. It may specifically include a polarity switching circuit 24 and a power conversion circuit 23. The output end of the polarity switching circuit is connected to the control end of the power conversion circuit, and the input end of the power conversion circuit is connected to the output end of the operational amplifier drive circuit. The output end of the power conversion circuit forms an output circuit 25, and the power conversion circuit is also connected to the input end of the feedback loop part.

[0058] For details, please refer to Figure 3 As shown, the polarity switching circuit includes a PWM generator, a resistor R16, a resistor R15, an NMOS tube Q4, an isolation chip U5, a resistor R73, a resistor R72, an NMOS tube Q15, an isolation chip U17, a resistor R53, a resistor R52, an NMOS tube Q12, an isolation chip U13, a resistor R27, a resistor R26, an NMOS tube Q10 and an isolation chip U11; the power conversion circuit includes an NMOS tube U3, an NMOS tube U9, an NMOS tube U2 and an NMOS tube U10.

[0059] Among them, the first output end of the PWM generator is connected to the gate of the NMOS tube Q4 through the resistor R16, the source of the NMOS tube Q4 is grounded, the drain of the NMOS tube Q4 is connected to the input end of the isolation chip U5, and the output end of the isolation chip U5 is connected to the gate of the NMOS tube U3.

[0060] The first output end of the PWM generator is connected to the gate of the NMOS tube Q4 through a resistor R16, the source of the NMOS tube Q4 is grounded, the drain of the NMOS tube Q4 is connected to the input end of the isolation chip U5, the output end of the isolation chip U5 is connected to the gate of the NMOS tube U3, one end of the resistor R15 is grounded, and the other end of the resistor R15 is connected between the source of the NMOS tube Q4 and the resistor R16.

[0061] The second output end of the PWM generator is connected to the gate of the NMOS tube Q12 through the resistor R53, the source of the NMOS tube Q12 is grounded, the drain of the NMOS tube Q12 is connected to the input end of the isolation chip U13, the output end of the isolation chip U13 is connected to the gate of the NMOS tube U2, one end of the resistor R52 is grounded, and the other end of the resistor R52 is connected between the source of the NMOS tube Q12 and the resistor R53.

[0062] The third output end of the PWM generator is connected to the gate of the NMOS tube Q15 through the resistor R73, the source of the NMOS tube Q15 is grounded, the drain of the NMOS tube Q15 is connected to the input end of the isolation chip U17, the output end of the isolation chip U17 is connected to the gate of the NMOS tube U9, one end of the resistor R72 is grounded, and the other end of the resistor R72 is connected between the source of the NMOS tube Q15 and the resistor R73.

[0063] The fourth output end of the PWM generator is connected to the gate of the NMOS tube Q10 through a resistor R27, the source of the NMOS tube Q10 is grounded, the drain of the NMOS tube Q10 is connected to the input end of the isolation chip U11, the output end of the isolation chip U11 is connected to the gate of the NMOS tube U10, one end of the resistor R26 is grounded, and the other end of the resistor R26 is connected between the source of the NMOS tube Q10 and the resistor R27.

[0064] The source of the NMOS tube U3 is connected to the drain of the NMOS tube U9, the source of the NMOS tube U2 is connected to the drain of the NMOS tube U10, the first output end of the output circuit is formed between the source of the NMOS tube U3 and the drain of the NMOS tube U9, and the second output end of the output circuit is formed between the source of the NMOS tube U2 and the drain of the NMOS tube U10; the drains of the NMOS tube U3 and the NMOS tube U2 are both connected to the auxiliary power supply.

[0065] The source of the NMOS transistor U9 and the source of the NMOS transistor U10 are both connected to the drain of the NMOS transistor Q16.

[0066] The full-bridge structure is used to generate 2 groups of 4-channel PWM waveforms through a PWM generator (such as DSP, etc.), which are isolated by optocouplers and drive 4 MOS tubes U2, U3, U9, and U10 to change the direction of the flow through the load, thereby changing the output polarity. When a high-level signal is given to U3 and U10, and a low-level signal is given to U2 and U9, the current flows from OUT1 to OUT2. Conversely, when a high-level signal is given to U2 and U9, and a low-level signal is given to U3 and U10, the current flows from OUT2 to OUT1, and the direction is changed. This method has a simple structure for changing the polarity of the current, and the switching speed is extremely fast. The sampling signal will not change with the output polarity, which simplifies the structure of the sampling circuit.

[0067] The feedback loop part may include, in addition to the above-mentioned sampling resistor circuit 31 (ie, the sampling resistor R1143), a sampling signal processing circuit 32, wherein the sampling signal processing circuit includes a first processing circuit, a second processing circuit and a third processing circuit.

[0068] The current sampling signal is obtained through the sampling resistor R1143. The sampling signal can be obtained by Figure 4 The sampling signal processing circuit in the circuit is fed back to the MCU for processing or display on the host computer. At the same time, the two output voltages can also be sampled and fed into the MCU to obtain the real-time voltage across the load. The real-time impedance change of the load can also be calculated through the obtained values, thereby inferring the temperature of the load.

[0069] For details, please refer to Figure 4 As shown, the first processing circuit includes resistor R484, resistor R17, resistor R6 and amplifier U6B; the second processing circuit includes resistor R443, resistor R29, resistor R42 and amplifier U6A; the third processing circuit includes amplifier U4A and resistor R464.

[0070] The first output end of the output circuit is connected to the non-inverting input end of the amplifier U6B through a resistor R484, the inverting input end of the amplifier U6B is connected to the output end of the amplifier U6B, and the output end of the amplifier U6B is also connected to the first input end of the main control chip circuit through a resistor R17, one end of the resistor R6 is grounded, and the other end of the resistor R6 is connected between the first input end of the main control chip circuit and the resistor R17.

[0071] The second output end of the output circuit is connected to the non-inverting input end of the amplifier U6A through a resistor R443, the inverting input end of the amplifier U6A is connected to the output end of the amplifier U6A, and the output end of the amplifier U6A is also connected to the second input end of the main control chip circuit through a resistor R29, one end of the resistor R42 is grounded, and the other end of the resistor R42 is connected between the second input end of the main control chip circuit and the resistor R29.

[0072] The non-inverting input terminal of the amplifier U4A is connected to the source of the NMOS tube Q16 through the sampling resistor R1143, the inverting input terminal of the amplifier U4A is connected to the output terminal of the amplifier U4A, and the output terminal of the amplifier U4A is connected to the third input terminal of the main control chip circuit through the resistor R464.

[0073] The sampling resistor circuit uses high-precision, low-temperature drift, high-power, and low-resistance sampling resistors, making the feedback loop control of the circuit more accurate and reliable. At the same time, the load impedance can be calculated by sampling the output voltage and sending it to the MCU.

[0074] Finally, it should be noted that the above-mentioned implementation modes are only optional embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention are within the scope of protection required by the present invention.

Claims

1. A high stability current source circuit, characterized in that: It includes a digital-to-analog conversion control part, a drive output part and a feedback loop part, wherein the digital-to-analog conversion control part includes a main control chip circuit and a digital-to-analog conversion circuit; the drive output part includes an operational amplifier drive circuit, a triode output circuit and a bridge direction switching circuit; The main control chip circuit controls the digital-to-analog conversion circuit, outputs a stable control voltage, and provides a constant driving signal for the driving output part. The output end of the digital-to-analog conversion circuit is connected to the input end of the triode output circuit through an operational amplifier driving circuit. The output end of the triode output circuit outputs the real-time voltage across the load through the bridge direction switching circuit. The input end of the feedback loop part is connected to the bridge direction switching circuit for obtaining a sampling signal; the output end of the feedback loop part and the output end of the bridge direction switching circuit are both connected to the input end of the main control chip circuit for comparing the sampling signal with the real-time voltage signal to control the dynamic compensation drive signal of the digital-to-analog conversion circuit.

2. The high stability current source circuit according to claim 1, characterized in that: The main control chip circuit is a microprocessor chip, the output end of the microprocessor chip is connected to the input end of the digital-to-analog conversion circuit, and the input end of the microprocessor chip is respectively connected to the output end of the feedback loop part and the output end of the bridge direction switching circuit.

3. The high stability current source circuit according to claim 2, characterized in that: The digital-to-analog conversion circuit includes a first digital-to-analog converter, a second digital-to-analog converter, a reference voltage circuit, and a first conditioning circuit and a second conditioning circuit. The microprocessor chip has a first output terminal and a second output terminal. The first output terminal of the microprocessor chip is connected to the input terminal of the first digital-to-analog converter, and the second output terminal of the microprocessor chip is connected to the input terminal of the second digital-to-analog converter. The reference voltage terminals of the first digital-to-analog converter and the second digital-to-analog converter are both connected to the output terminal of the reference voltage circuit. The output terminal of the first digital-to-analog converter and the output terminal of the second digital-to-analog converter are respectively connected to the input terminal of the operational amplifier driving circuit through the first conditioning circuit and the second conditioning circuit.

4. The high stability current source circuit according to claim 3, characterized in that: The reference voltage circuit includes a reference voltage source, a resistor R150, a capacitor C65, an amplifier U21B, a resistor R118, a resistor R128, a capacitor C502, an amplifier U22A, and resistors R105, R125, and R140; wherein the output end of the reference voltage source is connected to the non-inverting input end of the amplifier U21B through the resistor R150, the inverting input end of the amplifier U21B is connected to the output end of the amplifier U21B, and the output end of the amplifier U21B is also connected to the reference voltage end of the first digital-to-analog converter and the second digital-to-analog converter; one end of the resistor R105, the resistor R125, and the resistor R140 connected in series is connected to the The input end of the operational amplifier driving circuit, the other end of the resistor R105, the resistor R125 and the resistor R140 connected in series is connected to the output end of the amplifier U22A, the non-inverting input end of the amplifier U22A is grounded, the inverting input end of the amplifier U22A is connected to the output end of the amplifier U22A through the resistor R128, the inverting input end of the amplifier U22A is also connected to the output end of the amplifier U21B through the resistor R118, one end of the capacitor C65 is connected between the resistor R150 and the non-inverting input end of the amplifier U21B, and the other end of the capacitor C65 is grounded; the capacitor C502 is connected across the two ends of the resistor R128.

5. The high stability current source circuit according to claim 3, characterized in that: The first conditioning circuit includes a capacitor C45, a capacitor C51, an amplifier U24A, and a resistor R103, and the second conditioning circuit includes an amplifier U24B, a capacitor C67, a resistor R104, a resistor R126, and a resistor R141; one end of the capacitor C45 is connected between the output end of the first digital-to-analog converter and the inverting input end of the amplifier U24A, and the other end of the capacitor C45 is connected between the feedback end of the first digital-to-analog converter and the output end of the amplifier U24A, and the output end of the amplifier U24A is also connected to the output end of the operational amplifier driving circuit through the resistor R103. The positive input terminal of the amplifier U24A is grounded, and the capacitor C51 is connected across the two ends of the capacitor C45; one end of the capacitor C67 is connected between the output terminal of the second digital-to-analog converter and the inverting input terminal of the amplifier U24B, and the other end of the capacitor C67 is connected between the feedback terminal of the second digital-to-analog converter and the output terminal of the amplifier U24B. The output terminal of the amplifier U24B is also connected to the input terminal of the operational amplifier drive circuit through a series resistor R104, a resistor R126 and a resistor R141, and the positive input terminal of the amplifier U24B is grounded.

6. The high stability current source circuit according to any one of claims 2 to 5, characterized in that: A signal isolation circuit is also provided between the main control chip circuit and the digital-to-analog conversion circuit.

7. The high stability current source circuit according to claim 1, characterized in that: The operational amplifier driving circuit includes a resistor R106, an amplifier U22B, a capacitor C532, a resistor chip, an amplifier U26, a resistor R154, a capacitor C52, a resistor R138, a resistor R143, a resistor R152, a resistor R153, a resistor R151 and a capacitor C69; the transistor output circuit includes an NMOS transistor Q16, and the feedback loop part includes a sampling resistor R1143; The output end of the digital-to-analog conversion circuit is connected to the positive input end of the amplifier U22B through the resistor R106, the inverting input end of the amplifier U22B is connected to the output end of the amplifier U22B, the output end of the amplifier U22B is also connected to the inverting input end of the amplifier U26 through the resistor chip, the inverting input end of the amplifier U26 is connected to the output end of the amplifier U26 through the capacitor C52, and the output end of the amplifier U26 is also connected to the NMOS The gate of the NMOS tube Q16, the drain of the NMOS tube Q16 is connected to the bridge direction switching circuit, the source of the NMOS tube Q16 is connected to the non-inverting input terminal of the amplifier U26 through the sampling resistor R1143, and the two ends of the resistor R143 and the resistor R152 after being connected in parallel are respectively connected to the sampling resistor R1143 and the non-inverting input terminal of the amplifier U26; one end of the resistor R154 is grounded, and the other end of the resistor R154 is connected between the gate of the NMOS tube Q16 and the output terminal of the amplifier U26.

8. The high stability current source circuit according to claim 7, characterized in that: The bridge direction switching circuit includes a polarity switching circuit and a power conversion circuit. The output end of the polarity switching circuit is connected to the control end of the power conversion circuit. The input end of the power conversion circuit is connected to the output end of the operational amplifier driving circuit. The output end of the power conversion circuit forms an output circuit. The power conversion circuit is also connected to the input end of the feedback loop part.

9. The high stability current source circuit according to claim 8, characterized in that: The polarity switching circuit includes a PWM generator, a resistor R16, a resistor R15, an NMOS tube Q4, an isolation chip U5, a resistor R73, a resistor R72, an NMOS tube Q15, an isolation chip U17, a resistor R53, a resistor R52, an NMOS tube Q12, an isolation chip U13, a resistor R27, a resistor R26, an NMOS tube Q10 and an isolation chip U11; the power conversion circuit includes an NMOS tube U3, an NMOS tube U9, an NMOS tube U2 and an NMOS tube U10; The first output terminal of the PWM generator is connected to the gate of the NMOS tube Q4 through the resistor R16, the source of the NMOS tube Q4 is grounded, the drain of the NMOS tube Q4 is connected to the input terminal of the isolation chip U5, and the output terminal of the isolation chip U5 is connected to the gate of the NMOS tube U3; The first output end of the PWM generator is connected to the gate of the NMOS tube Q4 through the resistor R16, the source of the NMOS tube Q4 is grounded, the drain of the NMOS tube Q4 is connected to the input end of the isolation chip U5, the output end of the isolation chip U5 is connected to the gate of the NMOS tube U3, one end of the resistor R15 is grounded, and the other end of the resistor R15 is connected between the source of the NMOS tube Q4 and the resistor R16; The second output end of the PWM generator is connected to the gate of the NMOS tube Q12 through the resistor R53, the source of the NMOS tube Q12 is grounded, the drain of the NMOS tube Q12 is connected to the input end of the isolation chip U13, the output end of the isolation chip U13 is connected to the gate of the NMOS tube U2, one end of the resistor R52 is grounded, and the other end of the resistor R52 is connected between the source of the NMOS tube Q12 and the resistor R53; The third output terminal of the PWM generator is connected to the gate of the NMOS tube Q15 through the resistor R73, the source of the NMOS tube Q15 is grounded, the drain of the NMOS tube Q15 is connected to the input terminal of the isolation chip U17, the output terminal of the isolation chip U17 is connected to the gate of the NMOS tube U9, one end of the resistor R72 is grounded, and the other end of the resistor R72 is connected between the source of the NMOS tube Q15 and the resistor R73; The fourth output terminal of the PWM generator is connected to the gate of the NMOS tube Q10 through the resistor R27, the source of the NMOS tube Q10 is grounded, the drain of the NMOS tube Q10 is connected to the input terminal of the isolation chip U11, the output terminal of the isolation chip U11 is connected to the gate of the NMOS tube U10, one end of the resistor R26 is grounded, and the other end of the resistor R26 is connected between the source of the NMOS tube Q10 and the resistor R27; The source of the NMOS tube U3 is connected to the drain of the NMOS tube U9, the source of the NMOS tube U2 is connected to the drain of the NMOS tube U10, the source of the NMOS tube U3 and the drain of the NMOS tube U9 form a first output end of the output circuit, and the source of the NMOS tube U2 and the drain of the NMOS tube U10 form a second output end of the output circuit; the drains of the NMOS tube U3 and the NMOS tube U2 are both connected to the auxiliary power supply; The source of the NMOS transistor U9 and the source of the NMOS transistor U10 are both connected to the drain of the NMOS transistor Q16.

10. The high stability current source circuit according to claim 8, characterized in that: The feedback loop part also includes a sampling signal processing circuit, and the sampling signal processing circuit includes a first processing circuit, a second processing circuit and a third processing circuit; The first processing circuit includes a resistor R484, a resistor R17, a resistor R6 and an amplifier U6B; the second processing circuit includes a resistor R443, a resistor R29, a resistor R42 and an amplifier U6A; the third processing circuit includes an amplifier U4A and a resistor R464; The first output end of the output circuit is connected to the non-inverting input end of the amplifier U6B through a resistor R484, the inverting input end of the amplifier U6B is connected to the output end of the amplifier U6B, the output end of the amplifier U6B is also connected to the first input end of the main control chip circuit through a resistor R17, one end of the resistor R6 is grounded, and the other end of the resistor R6 is connected between the first input end of the main control chip circuit and the resistor R17; The second output end of the output circuit is connected to the non-inverting input end of the amplifier U6A through a resistor R443, the inverting input end of the amplifier U6A is connected to the output end of the amplifier U6A, the output end of the amplifier U6A is also connected to the second input end of the main control chip circuit through a resistor R29, one end of the resistor R42 is grounded, and the other end of the resistor R42 is connected between the second input end of the main control chip circuit and the resistor R29; The non-inverting input terminal of the amplifier U4A is connected to the source of the NMOS tube Q16 through the sampling resistor R1143, the inverting input terminal of the amplifier U4A is connected to the output terminal of the amplifier U4A, and the output terminal of the amplifier U4A is connected to the third input terminal of the main control chip circuit through the resistor R464.

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