Hybrid switching power amplification circuit of high-power high-precision alternating-current constant-current source

Abstract

The invention discloses a hybrid switch power amplification circuit of a high-power high-precision alternating-current constant-current source, which belongs to the technical field of electronics, comprises a load, a plurality of single-channel inner ring units, an outer ring unit and a control unit, and solves the technical problem that saturation of any one or more mutual inductors is easily caused when the mutual inductors output transient heavy loads in parallel. According to the invention, a hardware feedback mode is directly adopted, the response is rapid, the problem of saturation of a single mutual inductor is timely and effectively solved with relatively low hardware cost, the problem of saturation of any one or more random mutual inductors can be timely and effectively solved, and the reliability of the system is improved. According to the utility model, the structure is simple, the requirement of certain inductive and resistive loads of a connecting wire in actual use can be met, the work is reliable and stable, the phenomenon of output current oscillation is avoided, the transient output waveform is optimized, the requirement of certain bandwidth (50Hz-3.3 kHz) can be met, and the requirement of harmonic components in a large current test can be met.

Description

Technical Field

[0001] The invention belongs to the field of electronic technology and relates to a hybrid switch power amplifier circuit of a high-power and high-precision AC constant current source. Background Art

[0002] AC constant current source is usually used in the current thermal effect test and application of specific products. It is currently widely used in the type test of low-voltage complete switchgear and control equipment in low-voltage electrical appliances. For example, common tests of molded case circuit breakers include delay characteristics and verification, instantaneous characteristics and verification, etc. The rated current range of the frame grade covers 63A-1600A, so higher requirements are placed on the high current, high power, high precision and multi-faceted performance of the AC constant current source.

[0003] The current common large current AC constant current source adopts the SPWM+transformer implementation method, which can combine the high efficiency of the switching power amplifier and the high efficiency current rise of the transformer isolation. However, in specific applications, especially in the case of heavy load transient rise, the starting current waveform does not cross zero, and the DC component brought about causes the transformer to be easily saturated, thus affecting the continuous and stable operation of the overall circuit.

[0004] When the output power of the AC constant current source is low, it only needs the current transformer to have sufficient redundant power capacity to simulate the transient large current rise and fall. The circuit topology only uses the secondary side feedback to meet the actual needs. For example, on a 600VA current transformer, it is feasible to achieve 50A, 10 milliohm load (power is only 25W) transient load, but if you want to achieve 100 milliohm load (power reaches 250W), only the secondary side feedback will cause excessive primary side impact current during the rise process, leading to the problem of overcurrent protection of the power amplifier. In the case of a larger rated current output, the problem phenomenon will be more obvious. For example, with a 250A rated output, the same 10 milliohm load, the power reaches 625W, and the secondary side feedback is still used. Increasing the power capacity of the transformer will make the cost very high. Other solutions include resistor current limiting and increasing the primary leakage inductance, which are disguised attenuation impact currents. The former will reduce efficiency, and the latter will affect the establishment time of transient currents. Moreover, these two cannot fundamentally solve the problem of DC bias magnetism.

[0005] If a reliable output of N times the current of a single channel is achieved through parallel connection, it appears to be a flexible way to expand the current. However, in reality, when dealing with transient large current and high power increases, each channel's transformer will experience random and inconsistent primary current surges and corresponding secondary current drops during the initial increase. If measures are taken to compensate for the surge current only on a single channel, the overall performance will deteriorate when multiple channels are synthesized.

[0006] The practices and shortcomings of existing technologies;

[0007] 1. Single - path transient high - power load - carrying, with only closed - loop feedback on the secondary side, easily triggers the primary - side inrush current and subsequent strengthening similar to positive feedback, ultimately leading to over - current protection of the power amplifier module.

[0008] 2. Only the superposition feedback of the primary and secondary sides of a single - path current transformer. The calibration of the DC component of the current transformer is only mostly achieved, and a small part still remains. After long - term continuous superposition calibration, the ideal performance target cannot be reached, affecting the stability and distortion of the output.

[0009] 3. The superposition of the primary and secondary sides of a single - path mixes the differential amplification of the primary and secondary sides, which is beneficial to further compensating for the remaining tiny DC amount and improving the stability and distortion of a single - path. However, when synthesizing multiple paths, due to the lack of error adjustment of the overall closed - loop negative feedback, the current of the superposition output takes a long time to reach a stable state, and the distortion of the full - scale output is poor.

[0010] 4. If, based on the third prior art, only the secondary - side current feedback after 4 - path synthesis is added, it is beneficial to improving the overall stability and distortion. In the application of a steady - state source with slow rise and fall, it will not trigger a significant inrush current phenomenon. However, the problem is that in the application of the overall transient power, random inrush currents will still occur. And because only the secondary - side current feedback is taken as a whole, when adjusting the input signal of the 4 - path current power amplifier, a positive - compensation component is introduced, making the subsequent reference benchmark for each path no longer a sine wave that is beneficial to individual compensation. Eventually, the single - path compensation fails, and random over - current protection of each power amplifier module will still be triggered.

[0011] 5. For the commonly used programmable AC constant - current source on the current market, the core power - amplifier module uses a linear power amplifier, which can achieve relatively good accuracy. However, due to low efficiency, when making high - power output, more transistors need to be paralleled and a larger radiator is required. On the other hand, the common switching power amplifier uses the SPWM + IGBT method. Although it can achieve a relatively high overall efficiency, due to the switching frequency being within 50 kHz, the overall distortion of the signal in the band becomes worse, such as 1%. Summary of the Invention

[0012] The object of the present invention is to provide a hybrid - switch power - amplification circuit for a high - power and high - precision AC constant - current source, which solves the technical problem that any one or more current transformers are prone to saturation when the current transformers are connected in parallel and output transient heavy loads.

[0013] To achieve the above object, the present invention adopts the following technical solutions:

[0014] A hybrid switched power amplification circuit for a high-power and high-precision AC constant current source, comprising a load, several single-channel inner-loop units, an outer-loop unit, and a control unit. The input ends of all single-channel inner-loop units are connected to the output end of the outer-loop unit, and the output ends are all connected to the load. All single-channel inner-loop units are connected to the control unit and are controlled by the control unit;

[0015] The single-channel inner-loop unit includes an overload comparator X5, an inner-loop integration unit X2, a switching power amplifier X3, a switching power amplifier X4, a current boost transformer K1, a current transformer K3, a current transformer K2, a differential output unit X12, a feedback amplifier X8, and a feedback amplifier X7. The input end of the inner-loop integration unit X2 is the input end of the single-channel inner-loop unit; the output end of the inner-loop integration unit X2 is respectively connected to the overload comparator X5, the switching power amplifier X3, and the switching power amplifier X4; the switching power amplifier X3 and the switching power amplifier X4 are both connected to drive the current boost transformer K1, which is used to drive the load; the current transformer K3 and the current transformer K2 are respectively arranged in the primary circuit and the secondary circuit of the current boost transformer K1, and are respectively used to collect the primary current and the secondary current of the current boost transformer K1; the current transformer K3 and the current transformer K2 are respectively connected to the feedback amplifier X8 and the feedback amplifier X7. The output signals of the feedback amplifier X8 and the feedback amplifier X7 are simultaneously connected to the positive and negative input ends of the differential output unit X12. The output signals of the feedback amplifier X8, the feedback amplifier X7, the output signal of the differential output unit X12, and the signal of the output end of the outer-loop unit are all superimposed at the input end of the inner-loop integration unit X2; the output signal of the feedback amplifier X8 constitutes the primary current signal output end of the single-channel inner-loop unit, and the output signal of the feedback amplifier X7 constitutes the secondary current signal output end of the single-channel inner-loop unit; the primary current signal output end and the secondary current signal output end constitute the output end of the single-channel inner-loop unit; the overload comparator X5 is connected to the control unit and is used to report the overload warning signal of each channel to the control unit. The output end of the overload comparator X5 constitutes the power amplifier control enable end of the single-channel inner-loop unit. The enable ends of the switching power amplifier X3 and the switching power amplifier X4 are both connected to the control unit and are controlled by the control unit. The enable ends of the switching power amplifier X3 and the switching power amplifier X4 constitute the enable end of the single-channel inner-loop unit;

[0016] The outer ring unit includes an outer ring integration unit X14, a feedback amplification unit X16, and a feedback amplification unit X25. The signals at the signal output terminals of the primary side currents of all single-channel inner ring units are superimposed at the input terminal of the feedback amplification unit X25. The signals at the signal output terminals of the secondary side currents of all single-channel inner ring units are superimposed at the input terminal of the feedback amplification unit X16. The output signal of the feedback amplification unit X16, the output signal of the feedback amplification unit X25, and the signal of the external AC source are superimposed at the input terminal of the outer ring integration unit X14. The output terminal of the outer ring integration unit X14 is the output terminal of the outer ring unit.

[0017] The control unit includes a delay latch X6. The reported overload warning signals of all single-channel inner ring units are superimposed at the delay latch X6. The delay latch X6 is connected to the enable terminals of all single-channel inner ring units respectively.

[0018] Preferably, the specific circuit of the single-channel inner ring unit is that the input terminal of the inner ring integration unit X2 is the input terminal of the single-channel inner ring unit. The output terminal of the inner ring integration unit X2 is respectively connected to the input terminal of the overload comparator X5, the input terminals of the switching power amplifiers X3 and X4. The output terminal of the switching power amplifier X3 is connected to one end of the primary side of the current boosting transformer K1. The other end of the primary side of the current boosting transformer K1 is connected to the output terminal of the switching power amplifier K2 through the primary side coil of the current transformer K3. One end of the secondary side of the current transformer K3 is connected to the ground wire, and the other end is connected to the input terminal of the feedback amplifier X8. One end of the secondary side of the current boosting transformer is connected to one end of the load, and the other end is connected to the other end of the load through the primary side coil of the current transformer K2. One end of the secondary side of the current transformer K2 is connected to the ground wire, and the other end is connected to the input terminal of the feedback amplifier X7. The output terminals of the feedback amplifier X7 and the feedback amplifier X8 are also respectively connected to the negative input terminal and the positive input terminal of the differential output unit X12. The signals at the output terminal of the feedback amplifier X7, the output terminal of the feedback amplifier X8, the output terminal of the differential output unit X12, and the output terminal of the outer ring unit are superimposed at the input terminal of the inner ring integration unit X2.

[0019] Preferably, the differential output unit X12 includes a differential amplifier X14, a resistor R14, a resistor R17, a resistor R16, a resistor R15, and a resistor R18. The positive input terminal of the differential amplifier X14 is connected to the output terminal of the feedback amplifier X7 through the resistor R14. The negative input terminal of the differential amplifier X14 is also connected to the output terminal of the feedback amplifier X8 through the resistor R16. A resistor R15 is also connected between the negative input terminal and the output terminal of the differential amplifier X14.

[0020] The inner - loop integration unit X2 includes an integrator X10, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a resistor R6, and a resistor R7. The positive input terminal of the integrator X10 is connected to the ground wire through the resistor R2. The output terminal of the differential amplifier X14 is connected to the positive input terminal of the integrator X10 through the resistor R18. The negative input terminal of the integrator X10 is connected to the output terminal of the outer - loop unit through the resistor R3. The resistor R4 is connected between the negative input terminal and the output terminal of the integrator X10. The resistor R5 and the capacitor C1 are connected in series and then connected between the negative input terminal and the output terminal of the integrator X10. The output terminal of the feedback amplifier X7 is connected to the negative input terminal of the integrator X10 through the resistor R7. The output terminal of the feedback amplifier X8 is connected to the negative input terminal or the positive input terminal of the integrator X10 through the resistor R6.

[0021] Preferably, the feedback amplification unit X16 includes an amplifier X32, a resistor R29, and a resistor R25. The output terminals of the feedback amplifiers X7 in all the inner - loop integration units X2 are respectively connected to the negative input terminal of the amplifier X32 through different resistors. The positive input terminal of the amplifier X32 is connected to the ground wire through the resistor R29. A resistor R25 is connected between the negative input terminal and the output terminal of the amplifier X32.

[0022] The feedback amplification unit X25 includes an amplifier X33, a resistor R31, and a resistor R35. The output terminals of the feedback amplifiers X8 in all the inner - loop integration units X2 are respectively connected to the negative input terminal of the amplifier X33 through different resistors. The positive input terminal of the amplifier X33 is connected to the ground wire through the resistor 35. A resistor R31 is connected between the negative input terminal and the output terminal of the amplifier X33.

[0023] The outer - loop integration unit X14 includes an integrator X31, a resistor R20, a resistor R21, a resistor R22, a resistor R23, a capacitor C2, a resistor R24, and a resistor R37. The positive input terminal of the integrator X31 is connected to the ground wire through the resistor R20, and the negative input terminal is connected to the external AC signal generator through the resistor R21. The resistor R22 is connected between the negative input terminal and the output terminal of the integrator X31. The resistor R23 and the capacitor C2 are connected in series and then in parallel with the resistor R22. The output terminal of the amplifier X32 is connected to the negative input terminal of the integrator X31 through the resistor R24. The output terminal of the amplifier X33 is connected to the negative input terminal or the positive input terminal of the integrator X31 through the resistor R37.

[0024] Preferably, the external AC source is a 50Hz sinusoidal AC signal generator.

[0025] Preferably, the control chips of the switching power amplifiers X3 and X4 are IRS2092.

[0026] The hybrid switch power amplification circuit of a high-power and high-precision AC constant current source according to the present invention solves the technical problem that any one or more current transformers are prone to saturation when the parallel output of the current transformers is transiently overloaded. In the present invention, the primary-secondary superposition feedback method is adopted, which is different from other software methods. It directly uses the hardware feedback method, with rapid response. At the same time, with a relatively low hardware cost, it can timely and effectively solve the problem of saturation of a single current transformer. The present invention has multiple parallel outputs and hybrid primary-secondary superposition feedback. Through the hardware feedback method, it can timely and effectively solve the problem that any one or more random current transformers are saturated. In addition, this topology has a certain tolerance for the consistency of the parasitic parameters of multiple current transformers; each internal module can be debugged separately first and then synthesized; if a single module fails, it can also be checked one by one and then located, thus reducing the overall circuit production and debugging difficulty. Finally, in extreme abnormal situations, such as overcurrent and over-temperature protection of any one power amplifier, the overload protection circuit will turn off all power amplifiers, improving the overall working reliability. The self-oscillating switch power amplifier based on IRS2092 and developed by the present invention uses a switching frequency of 300 kHz. The optimized circuit design can improve the efficiency and in-band signal distortion. By adopting the single-channel output and parallel output methods, it can be compatible with the transient output power requirements and at the same time meet the basic performance of the steady-state output. For example, the distortion is 0.1%, the stability is 0.01%, and the amplitude and phase accuracy are 0.1%. After the feedback loop is optimized, it can meet the needs of a certain inductive and resistive load of the connecting wire in actual use, work reliably and stably, and there will be no phenomenon of output current oscillation. Not only the transient output waveform is optimized, but also the needs of a certain bandwidth (50 Hz - 3.3 kHz) can be met, and the requirements for harmonic components in large current tests can be satisfied. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the schematic topology diagram of the present invention;

[0028] Figure 2 is the circuit diagram in which the output terminal of the amplifier X33 in the outer loop unit of the present invention is connected to the negative input terminal of the integrator X31 through the resistor R37;

[0029] Figure 3 is the circuit diagram in which the output terminal of the amplifier X33 in the outer loop unit of the present invention is connected to the positive input terminal of the integrator X31 through the resistor R37;

[0030] Figure 4 is the circuit diagram topology of the single-channel inner loop unit of the present invention;

[0031] Figure 5 is the circuit diagram in which the output terminal of the feedback amplifier X8 in the single-channel inner loop unit of the present invention is connected to the negative input terminal of the integrator X10 through the resistor R6;

[0032] Figure 6 It is the circuit diagram in which the output terminal of the feedback amplifier X8 in the single-channel inner loop unit of the present invention is connected to the positive input terminal of the integrator X10 through the resistor R6;

[0033] Figure 7 It is the waveform of the primary and secondary feedback superposition when the primary impact current of a single mutual inductor in the single-channel inner loop unit of the present invention is relatively large;

[0034] Figure 8 It is the waveform of the primary and secondary feedback subtraction when the primary impact current of a single mutual inductor in the single-channel inner loop unit of the present invention is relatively large;

[0035] Figure 9 It is the waveform of the primary and secondary feedback addition when the primary impact current of a single mutual inductor in the single-channel inner loop unit of the present invention is relatively small;

[0036] Figure 10 It is the waveform of the primary and secondary feedback subtraction when the primary impact current of a single mutual inductor in the single-channel inner loop unit of the present invention is relatively small;

[0037] Figure 11 It is the single and mixed waveforms of the primary and secondary currents of each channel of 4 mutual inductors in the outer loop unit of this embodiment, and the output waveform of the integrator. Specific embodiments

[0038] Such as Figures 1-11 The hybrid switched power amplifier circuit of a high-power and high-precision AC constant current source as described above, including a load, several single-channel inner loop units, an outer loop unit and a control unit. The input terminals of all single-channel inner loop units are connected to the output terminal of the outer loop unit, and the output terminals are all connected to the load. All single-channel inner loop units are connected to the control unit and are controlled by the control unit;

[0039] The single-channel inner loop unit includes an overload comparator X5, an inner loop integration unit X2, switching power amplifiers X3 and X4, a current boosting transformer K1, current transformers K3 and K2, a differential output unit X12, feedback amplifiers X8 and X7. The input end of the inner loop integration unit X2 is the input end of the single-channel inner loop unit; the output end of the inner loop integration unit X2 is respectively connected to the overload comparator X5, the switching power amplifier X3 and the switching power amplifier X4; both the switching power amplifier X3 and the switching power amplifier X4 are connected to drive the current boosting transformer K1 for driving the current boosting transformer K1, and the current boosting transformer K1 is used to drive the load; the current transformers K3 and K2 are respectively arranged in the primary circuit and the secondary circuit of the current boosting transformer K1 for collecting the primary current and the secondary current of the current boosting transformer K1; the current transformers K3 and K2 are respectively connected to the feedback amplifier X8 and the feedback amplifier X7, and the output signals of the feedback amplifier X8 and the feedback amplifier X7 are simultaneously connected to the positive and negative input ends of the differential output unit X12. The output signals of the feedback amplifier X8, the output signals of the feedback amplifier X7, the output signal of the differential output unit X12 and the signal at the output end of the outer loop unit are all superimposed at the input end of the inner loop integration unit X2; the output signal of the feedback amplifier X8 constitutes the primary current signal output end of the single-channel inner loop unit, and the output signal of the feedback amplifier X7 constitutes the secondary current signal output end of the single-channel inner loop unit; the primary current signal output end and the secondary current signal output end constitute the output end of the single-channel inner loop unit; the overload comparator X5 is connected to the control unit for reporting the overload warning signals of each channel to the control unit. The output end of the overload comparator X5 constitutes the power amplifier control enable end of the single-channel inner loop unit. The enable ends of the switching power amplifier X3 and the switching power amplifier X4 are both connected to the control unit and are controlled by the control unit. The enable ends of the switching power amplifier X3 and the switching power amplifier X4 constitute the enable end of the single-channel inner loop unit;

[0040] The specific circuit of the single-channel inner loop unit: The input end of the inner loop integration unit X2 is the input end of the single-channel inner loop unit. The output end of the inner loop integration unit X2 is respectively connected to the input end of the overload comparator X5, the input end of the switching power amplifier X3, and the input end of the switching power amplifier X4. The output end of the switching power amplifier X3 is connected to one end of the primary side of the current boosting transformer K1. The other end of the primary side of the current boosting transformer K1 is connected to the output end of the switching power amplifier K2 through the primary side coil of the current transformer K3. One end of the secondary side of the current transformer K3 is connected to the ground wire, and the other end is connected to the input end of the feedback amplifier X8. One end of the secondary side of the current boosting transformer is connected to one end of the load, and the other end is connected to the other end of the load through the primary side coil of the current transformer K2. One end of the secondary side of the current transformer K2 is connected to the ground wire, and the other end is connected to the input end of the feedback amplifier X7. The output ends of the feedback amplifier X7 and the feedback amplifier X8 are respectively connected to the negative input end and the positive input end of the differential output unit X12. The signals at the output end of the feedback amplifier X7, the output end of the feedback amplifier X8, the output end of the differential output unit X12, and the output end of the outer loop unit are superimposed at the input end of the inner loop integration unit X2.

[0041] The outer loop unit includes an outer loop integration unit X14, a feedback amplification unit X16, and a feedback amplification unit X25. The signals at the output ends of the primary side current signals of all single-channel inner loop units are superimposed at the input end of the feedback amplification unit X25. The signals at the output ends of the secondary side current signals of all single-channel inner loop units are superimposed at the input end of the feedback amplification unit X16. The output signal of the feedback amplification unit X16, the output signal of the feedback amplification unit X25, and the signal of the external AC source are superimposed at the input end of the outer loop integration unit X14. The output end of the outer loop integration unit X14 is the output end of the outer loop unit; the external AC source is a 50Hz sine AC signal generator.

[0042] The differential output unit X12 includes a differential amplifier X14, a resistor R14, a resistor R17, a resistor R16, a resistor R15, and a resistor R18. The positive input end of the differential amplifier X14 is connected to the output end of the feedback amplifier X7 through the resistor R14. The negative input end of the differential amplifier X14 is also connected to the output end of the feedback amplifier X8 through the resistor R16. A resistor R15 is also connected between the negative input end and the output end of the differential amplifier X14;

[0043] The inner loop integration unit X2 includes an integrator X10, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a resistor R6, and a resistor R7. The positive input terminal of the integrator X10 is connected to the ground wire through the resistor R2. The output terminal of the differential amplifier X14 is connected to the positive input terminal of the integrator X10 through the resistor R18. The negative input terminal of the integrator X10 is connected to the output terminal of the outer loop unit through the resistor R3. The resistor R4 is connected between the negative input terminal and the output terminal of the integrator X10. The resistor R5 and the capacitor C1 are connected in series and then connected between the negative input terminal and the output terminal of the integrator X10. The output terminal of the feedback amplifier X7 is connected to the negative input terminal of the integrator X10 through the resistor R7. The output terminal of the feedback amplifier X8 is connected to the negative input terminal or the positive input terminal of the integrator X10 through the resistor R6.

[0044] The feedback amplification unit X16 includes an amplifier X32, a resistor R29, and a resistor R25. The output terminals of the feedback amplifiers X7 in all the inner loop integration units X2 are respectively connected to the negative input terminal of the amplifier X32 through different resistors. The positive input terminal of the amplifier X32 is connected to the ground wire through the resistor R29. A resistor R25 is connected between the negative input terminal and the output terminal of the amplifier X32;

[0045] The feedback amplification unit X25 includes an amplifier X33, a resistor R31, and a resistor R35. The output terminals of the feedback amplifiers X8 in all the inner loop integration units X2 are respectively connected to the negative input terminal of the amplifier X33 through different resistors. The positive input terminal of the amplifier X33 is connected to the ground wire through the resistor 35. A resistor R31 is connected between the negative input terminal and the output terminal of the amplifier X33;

[0046] The outer loop integration unit X14 includes an integrator X31, a resistor R20, a resistor R21, a resistor R22, a resistor R23, a capacitor C2, a resistor R24, and a resistor R37. The positive input terminal of the integrator X31 is connected to the ground wire through the resistor R20, and the negative input terminal is connected to the external AC signal generator through the resistor R21. The resistor R22 is connected between the negative input terminal and the output terminal of the integrator X31. The resistor R23 and the capacitor C2 are connected in series and then in parallel with the resistor R22. The output terminal of the amplifier X32 is connected to the negative input terminal of the integrator X31 through the resistor R24. The output terminal of the amplifier X33 is connected to the negative input terminal or the positive input terminal of the integrator X31 through the resistor R37.

[0047] In this embodiment, current sampling transformers with different ranges are used. After current-voltage conversion, the currents on the primary side and the secondary side are converted into voltage values of the same level. For example, 10A on the primary side and 250A on the secondary side are both finally converted into 5V voltage. Under normal circumstances, the currents on the primary and secondary sides are completely synchronized within the band. Therefore, after taking certain coefficients of both and superimposing them, it is similar to only taking the secondary side feedback when calculating the overall feedback; the waveform under normal circumstances is Figure 2, Figure 3 , Figure 5 , Figure 6 ; The abnormal situation is Figures 7-11 .

[0048] Taking Figure 5 the circuit connection method shown as an example, the key test points for the superposition feedback of the primary and secondary sides of a single mutual inductor respectively include: the connection node of resistor R14 and amplifier X7 is test point ISEC_N, the connection node of resistor R16 and amplifier X8 is test point IPRI_N, the output terminal of differential amplifier X14 is test point ISEC_N - IPRI_N, the output terminal of integrator X10 is test point I_INT, the connection node of resistor R6 and amplifier X8 is test point IPRI_P, and the connection node of resistor R7 and amplifier X7 is ISEC_P.

[0049] When the impact on the primary side of the mutual inductor is large, as Figure 7 and Figure 8 shown, the waveform of the primary side current bulges outward, and the waveform of the secondary side current caves inward, which exactly shows that when the impact current on the primary side becomes larger at this time, the energy on the secondary side cannot be effectively transferred. At this time, after taking the superposition of the two, the overall situation is still bulging outward. After comparing this waveform with the reference sine wave, the waveform output by the integrator at this time generally presents an inward concave envelope, which effectively compensates the original DC component. The subtraction of the two can more prominently show the position of waveform compensation; when the impact current is small, such as Figure 9 and Figure 10 , the sum of the primary and secondary sides is almost the same as the sine wave as a whole. After passing through the integrator and outputting, the remaining tiny DC component still cannot be distinguished. At this time, by using the waveform after subtracting the two for compensation, the compensation of the remaining tiny DC component of the mutual inductor can be accelerated.

[0050] The above compensation process can be effectively realized, which is inseparable from the following basic conditions:

[0051] A The primary side current sampling mutual inductor has a strong ability to withstand saturation, and on the basis of continuous testing of 10 ARMS, the peak value is not less than 50 A.

[0052] B The peak current output ability of the switching power amplifier module is not less than 50 A under the condition of A.

[0053] C The self-pole of the output LC low-pass filter of the switching power amplifier module needs to be zero-compensated inside the voltage power amplifier to prevent internal resonance caused by large-range changes in the equivalent load of the voltage output.

[0054] In this embodiment, multiple mutual inductors are connected in parallel and output, and how to achieve the compensation for the impact current of any one or more primary sides in the hybrid primary-secondary superposition feedback.

[0055] After adding the outer loop, the hybrid primary and secondary current signals used in the feedback loop are superimposed. When the inrush current is small, the compensation mechanism is similar to the waveform description taking Figure 5 as an example. As long as the waveform output by the outer loop integrator is close to a sine wave, independent compensation for each channel can be completed; however, when a large primary current inrush occurs, especially randomly and inconsistently, the unique self-recovery characteristic of the outer loop feedback will appear at this time. Taking the 4-channel synthesis as an example Figure 3 and Figure 11 shown, the set key test points respectively include the secondary current signals of all single-channel inner loop units input to the input terminal of amplifier X32. Multiple test points are set as ISEC_P_1 to ISEC_P_N, the output terminal of X32 is the test point ISEC_P_SUM, the output terminal of X31 is the test point I_INT_OUT, and a test point is set as IPRI_N_SUM for the input of X33 to the positive input terminal of X31. The primary current signals of all single-channel inner loop units are input to the input terminal of amplifier X33, and multiple test points are set as IPRI_N_1 to IPRI_N_N.

[0056] If different degrees of primary inrush currents occur in all 3 primary sides (channels 2, 3, 4, IPRI_N_2, IPRI_N_3, IPRI_N_4), and the primary inrush current phenomenon is not obvious in 1 primary side (channel 1, IPRI_N_1), it will lead to channel 4 (IPRI_N_4) with the most severe saturation phenomenon. At this time, the secondary side is close to the short-circuit state, and then a short-time current reflux (ISEC_P_4) will be formed. The saturation phenomena of the other two channels (channels 2 and 3, IPRI_N_2, IPRI_N_3) are slightly weaker, and the secondary output current capacity is significantly reduced (ISEC_P_2, ISEC_P_3). Due to the effect of the large closed loop, the current output of the current transformer in the non-saturated channel (channel 1, IPRI_N_1) will be more at this time (ISEC_P_1). Generally speaking, however, the superimposed results of the severely saturated primary and secondary waveforms and the superimposed results of the non-saturated primary and secondary waveforms will form an obvious counteract (IPRI_N_SUM, ISEC_P_SUM). The superimposed primary and secondary waveforms with weaker saturation are close to a sine wave itself (i.e., I_INT_OUT), and the power finally output to the load is significantly reduced. All current transformers with saturation phenomena will be effectively compensated during this stage.

[0057] Different from the overload protection mechanism of a single current transformer, when a fault phenomenon occurs in any one channel, the overload circuit will promptly turn off all power amplifier outputs to avoid subsequent overall abnormal situations (such as 3 channels outputting 4 times the rated current).

[0058] Both of the above two circuit topologies follow the processing idea of "comparing the sum of the primary and secondary side currents with a sine wave for large inrush currents and subtracting the in-phase primary and secondary side currents for small inrush currents", and can meet the requirements of overall closed-loop negative feedback during normal output.

[0059] The control unit includes a delay latch X6. The reported overload warning signals of all single-channel inner loop units are superimposed at the delay latch X6, and the delay latch X6 is connected to the enable terminals of all single-channel inner loop units respectively. The delay latch X6 is a prior art, so it will not be described in detail.

[0060] The control chips of the switching power amplifier X3 and the switching power amplifier X4 are IRS2092. The amplifiers or integrators used in this embodiment are all conventional models.

[0061] The hybrid switching power amplification circuit of a high-power and high-precision AC constant current source according to the present invention solves the technical problem that any one or more current transformers are prone to saturation when the current transformers are connected in parallel and output transient heavy loads. In the present invention, the primary-secondary superposition feedback method is adopted, which is different from other software methods. It directly uses the hardware feedback method, with rapid response. At the same time, with a relatively low hardware cost, it can timely and effectively solve the problem of saturation of a single current transformer. The present invention has multiple parallel outputs and hybrid primary-secondary superposition feedback. Through the hardware feedback method, it can timely and effectively solve the problem that any one or more random current transformers are saturated. In addition, this topology has a certain tolerance for the consistency of the parasitic parameters of multiple current transformers; each internal module can be debugged separately first and then synthesized; if a single module fails, it can also be checked one by one and then located, thereby reducing the production and debugging difficulty of the overall circuit. Finally, in extreme abnormal situations, such as overcurrent or over-temperature protection of any one of the power amplifiers, the overload protection circuit will turn off all power amplifiers, improving the reliability of the overall operation. The self-oscillating switching power amplifier based on IRS2092 and developed by the present invention uses a switching frequency of 300 kHz. The optimized circuit design can improve the efficiency and in-band signal distortion. By using the single-channel output and parallel output methods, it can be compatible with the transient output power requirements and meet the basic performance of the steady-state output at the same time, such as distortion of 0.1%, stability of 0.01%, amplitude and phase accuracy of 0.1%. After the feedback loop is optimized, it can meet the needs of a certain inductive and resistive load of the connecting wire in actual use, work reliably and stably, and will not show the phenomenon of output current oscillation. Not only the transient output waveform is optimized, but also the needs of a certain bandwidth (50 Hz - 3.3 kHz) can be met, and the requirements of harmonic components in large current tests can be satisfied.

Claims

1. A hybrid switched power amplification circuit for a high-power and high-precision AC constant current source, characterized in that: It includes a load, several single-channel inner-loop units, an outer-loop unit, and a control unit. The input ends of all single-channel inner-loop units are connected to the output end of the outer-loop unit, and the output ends are all connected to the load. All single-channel inner-loop units are connected to the control unit and are controlled by the control unit; The single-channel inner-loop unit includes an overload comparator X5, an inner-loop integration unit X2, a switching power amplifier X3, a switching power amplifier X4, a current-increasing transformer K1, a current transformer K3, a current transformer K2, a differential output unit X12, a feedback amplifier X8, and a feedback amplifier X7. The input end of the inner-loop integration unit X2 is the input end of the single-channel inner-loop unit; the output end of the inner-loop integration unit X2 is respectively connected to the overload comparator X5, the switching power amplifier X3, and the switching power amplifier X4; the switching power amplifier X3 and the switching power amplifier X4 are both connected to drive the current-increasing transformer K1, which is used to drive the load; the current transformer K3 and the current transformer K2 are respectively arranged in the primary side circuit and the secondary side circuit of the current-increasing transformer K1, and are respectively used to collect the primary side current and the secondary side current of the current-increasing transformer K1; the current transformer K3 and the current transformer K2 are respectively connected to the feedback amplifier X8 and the feedback amplifier X7. The output signals of the feedback amplifier X8 and the feedback amplifier X7 are simultaneously connected to the positive and negative input ends of the differential output unit X12. The output signals of the feedback amplifier X8, the feedback amplifier X7, the output signal of the differential output unit X12, and the signal of the output end of the outer-loop unit are all superimposed at the input end of the inner-loop integration unit X2; the output signal of the feedback amplifier X8 constitutes the primary side current signal output end of the single-channel inner-loop unit, and the output signal of the feedback amplifier X7 constitutes the secondary side current signal output end of the single-channel inner-loop unit; the primary side current signal output end and the secondary side current signal output end constitute the output end of the single-channel inner-loop unit; the overload comparator X5 is connected to the control unit and is used to report the overload warning signal of each channel to the control unit. The output end of the overload comparator X5 constitutes the power amplifier control enable end of the single-channel inner-loop unit. The enable ends of the switching power amplifier X3 and the switching power amplifier X4 are both connected to the control unit and are controlled by the control unit. The enable ends of the switching power amplifier X3 and the switching power amplifier X4 constitute the enable end of the single-channel inner-loop unit; The outer-loop unit includes an outer-loop integration unit X14, a feedback amplification unit X16, and a feedback amplification unit X25. The signals of the primary side current signal output ends of all single-channel inner-loop units are superimposed at the input end of the feedback amplification unit X25, and the signals of the secondary side current signal output ends of all single-channel inner-loop units are superimposed at the input end of the feedback amplification unit X16. The output signal of the feedback amplification unit X16, the output signal of the feedback amplification unit X25, and the signal of the external AC source are all superimposed at the input end of the outer-loop integration unit X14. The output end of the outer-loop integration unit X14 is the output end of the outer-loop unit; The control unit includes a delay latch X6, and the reported overload warning signals of all single-channel inner-loop units are superimposed at the delay latch X6. The delay latch X6 is connected to the enable terminals of all single-channel inner-loop units respectively.

2. The hybrid switched power amplifier circuit of a high-power and high-precision AC constant current source according to claim 1, characterized in that: The specific circuit of the single-channel inner-loop unit is that the input end of the inner-loop integration unit X2 is the input end of the single-channel inner-loop unit. The output end of the inner-loop integration unit X2 is respectively connected to the input end of the overload comparator X5, the input end of the switching power amplifier X3, and the input end of the switching power amplifier X4. The output end of the switching power amplifier X3 is connected to one end of the primary side of the current step-up transformer K1. The other end of the primary side of the current step-up transformer K1 is connected to the output end of the switching power amplifier K2 through the primary side coil of the current transformer K3. One end of the secondary side of the current transformer K3 is connected to the ground wire, and the other end is connected to the input end of the feedback amplifier X8. One end of the secondary side of the current step-up transformer is connected to one end of the load, and the other end is connected to the other end of the load through the primary side coil of the current transformer K2. One end of the secondary side of the current transformer K2 is connected to the ground wire, and the other end is connected to the input end of the feedback amplifier X7. The output ends of the feedback amplifier X7 and the feedback amplifier X8 are also respectively connected to the negative input end and the positive input end of the differential output unit X12. The signals at the output end of the feedback amplifier X7, the output end of the feedback amplifier X8, the output end of the differential output unit X12, and the output end of the outer-loop unit are superimposed at the input end of the inner-loop integration unit X2.

3. The hybrid switch power amplification circuit of a high-power and high-precision AC constant current source according to claim 2, characterized in that: The differential output unit X12 includes a differential amplifier X14, a resistor R14, a resistor R17, a resistor R16, a resistor R15, and a resistor R18. The positive input end of the differential amplifier X14 is connected to the output end of the feedback amplifier X7 through the resistor R14. The negative input end of the differential amplifier X14 is also connected to the output end of the feedback amplifier X8 through the resistor R16. A resistor R15 is also connected between the negative input end and the output end of the differential amplifier X14. The inner-loop integration unit X2 includes an integrator X10, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a resistor R6, and a resistor R7. The positive input end of the integrator X10 is connected to the ground wire through the resistor R2. The output end of the differential amplifier X14 is connected to the positive input end of the integrator X10 through the resistor R18. The negative input end of the integrator X10 is connected to the output end of the outer-loop unit through the resistor R3. A resistor R4 is connected between the negative input end and the output end of the integrator X10. The resistor R5 and the capacitor C1 are connected in series and then connected between the negative input end and the output end of the integrator X10. The output end of the feedback amplifier X7 is connected to the negative input end of the integrator X10 through the resistor R7. The output end of the feedback amplifier X8 is connected to the negative input end or the positive input end of the integrator X10 through the resistor R6.

4. The hybrid switch power amplification circuit of a high-power and high-precision AC constant current source according to claim 3, characterized in that: The feedback amplification unit X16 includes an amplifier X32, a resistor R29, and a resistor R25. The output terminals of the feedback amplifiers X7 in all the inner-loop integration units X2 are respectively connected to the negative input terminal of the amplifier X32 through different resistors. The positive input terminal of the amplifier X32 is connected to the ground wire through the resistor R29, and a resistor R25 is connected between the negative input terminal and the output terminal of the amplifier X32; The feedback amplification unit X25 includes an amplifier X33, a resistor R31, and a resistor R35. The output terminals of the feedback amplifiers X8 in all the inner-loop integration units X2 are respectively connected to the negative input terminal of the amplifier X33 through different resistors. The positive input terminal of the amplifier X33 is connected to the ground wire through the resistor 35, and a resistor R31 is connected between the negative input terminal and the output terminal of the amplifier X33; The outer-loop integration unit X14 includes an integrator X31, a resistor R20, a resistor R21, a resistor R22, a resistor R23, a capacitor C2, a resistor R24, and a resistor R37. The positive input terminal of the integrator X31 is connected to the ground wire through the resistor R20, the negative input terminal is connected to the external AC signal generator through the resistor R21. A resistor R22 is connected between the negative input terminal and the output terminal of the integrator X31. The resistor R23 and the capacitor C2 are connected in series and then in parallel with the resistor R22. The output terminal of the amplifier X32 is connected to the negative input terminal of the integrator X31 through the resistor R24. The output terminal of the amplifier X33 is connected to the negative input terminal or the positive input terminal of the integrator X31 through the resistor R37.

5. The hybrid switched power amplifier circuit of a high-power and high-precision AC constant current source as claimed in claim 1, wherein: The external AC source is a 50Hz sinusoidal AC signal generator.

6. The hybrid switch power amplification circuit of a high-power and high-precision AC constant current source as described in claim 1, wherein: The control chips of the switching power amplifiers X3 and X4 are IRS2092.

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