Inverter drive circuit based on double closed-loop error compensation and high-voltage generator

Abstract

The invention provides an inverter drive circuit based on double closed-loop error compensation and a high-voltage generator, and the inverter drive circuit comprises a first operational amplifier circuit which is connected with a voltage doubling rectifying circuit to form a voltage feedback loop so as to obtain a kV feedback signal, and is used for carrying out the operation of a reference voltage signal and the kV feedback signal, and then outputting a first error compensation signal. The second operational amplifier circuit is connected with the resonant converter through the resonant current sampling circuit to form a resonant current feedback loop so as to obtain a resonant current feedback signal, and is used for calculating the first error compensation signal and the resonant current feedback signal and then outputting a second error compensation signal; the drive control circuit is used for outputting a PFM modulation signal to the drive circuit according to the second error compensation signal. The drive circuit is used for carrying out signal processing on the PFM modulation signal and outputting a PFM drive signal to the resonant converter. Accurate error compensation is carried out on LCC topology driving through a voltage and current double-closed-loop feedback loop, and the effect of improving the transient response and efficiency of the X-ray power supply system is achieved.

Description

Technical Field

[0001] The present invention relates to the field of high-voltage generators for DR devices, and particularly to an inverter drive circuit and a high-voltage generator based on double closed-loop error compensation. Background Art

[0002] The high-voltage generator is one of the core components of a DR (Digital Radiography) device. Its main function is to convert the power supply voltage and current into the X-ray tube voltage and tube current, so as to supply the DC high voltage to the cathode and anode of the X-ray tube. Therefore, the performance of the high-voltage generator is directly related to the safety of the DR device and the overall life of the product. See Figure 1 , the high-voltage generator mainly consists of a power supply circuit, a high-voltage generation circuit, a filament circuit, a control circuit, an application device circuit, and a box body for encapsulating the above circuits. Among them, the power supply circuit mainly plays the role of isolating the mains power from other circuits of the high-voltage generator and supplying power to other circuits. The high-voltage generation circuit mainly boosts the AC low voltage (220V / 380V) to the DC high voltage (150kV) to supply power to the X-ray tube. The filament circuit mainly steps down the low voltage (220V / 380V) to the ultra-low voltage (12V) to supply power to the filament, so as to heat the filament to generate free electrons. The control circuit is mainly used to control the output voltage, output filament current, and loading time of the high-voltage generator, and at the same time communicate with other components in the X-ray equipment imaging chain to ensure the accuracy of exposure. In addition to supplying power to the X-ray tube, the high-voltage generator also has a circuit for supplying power to other devices, such as a flat panel detector, a collimator, etc.

[0003] In the current CBCT (Cone beam CT) high-voltage generators, most of the inverter circuits of X-ray machines adopt the hard-switching full-bridge PWM drive method. Although this method can make the X-ray load output 1.2KW to meet the usage requirements, in the on and off processes of the switching devices in the hard-switching method, the current rise and voltage drop or voltage rise and current drop occur simultaneously, which leads to the overlap of the voltage and current waveforms, thus generating switching losses. This loss increases rapidly with the increase of the switching frequency, seriously affecting the efficiency and life of the switch. In addition, the hard-switching method generally only adopts a kV voltage closed-loop feedback loop, which cannot achieve precise error compensation control and good system stability. In addition, at present, most of the inverter drive circuits of high-voltage generators adopt discrete components to establish a VCO module. Although its structure is simple and the cost is low, its power consumption is large, the frequency stability is poor, and it is greatly affected by the component parameters. Precise component selection and debugging are required, which increases the complexity and cost of the design.

[0004] Therefore, an inverter drive circuit that can improve the stability and transient response efficiency of the X-ray power supply system and a high-voltage generator that reduces the switching losses in the inverter circuit are needed. Summary of the Invention

[0005] The inverter drive circuit and high-voltage generator based on double closed-loop error compensation provided by the present invention are mainly used to solve problems such as large switching losses in existing high-voltage generators, low efficiency and poor stability of their inverter drive circuits, so as to achieve the effects of improving the stability of the X-ray power supply system, transient response efficiency, and reducing the switching losses in the inverter circuit.

[0006] The present invention achieves the above object through the following technical solutions:

[0007] The inverter drive circuit based on double closed-loop error compensation is used to provide a drive signal for the resonant converter in the DR high-voltage generator, and includes a first operational amplifier circuit, a second operational amplifier circuit, a drive control circuit, a drive circuit, and a resonant current sampling circuit. The input end of the first operational amplifier circuit inputs a reference voltage signal and forms a kV voltage feedback loop by connecting with the voltage doubling and rectifying circuit of the high-voltage generator to obtain a kV feedback signal. The first operational amplifier circuit is used to operate the reference voltage signal and the kV feedback signal and then output a first error compensation signal to the input end of the second operational amplifier circuit. The input end of the second operational amplifier circuit is connected to the output end of the resonant converter through the resonant current sampling circuit to form a resonant current feedback loop to obtain a resonant current feedback signal. The second operational amplifier circuit is used to operate the first error compensation signal and the resonant current feedback signal and then output a second error compensation signal to the drive control circuit. The drive control circuit is used to output a PFM modulation signal to the drive circuit according to the second error compensation signal. The drive circuit is used to process the PFM modulation signal and output a PFM drive signal to the resonant converter.

[0008] A further solution is that the first operational amplifier circuit is a YTPE3 type loop compensation circuit.

[0009] A further solution is that the first operational amplifier circuit includes a first operational amplifier circuit and a second operational amplifier circuit. The first operational amplifier circuit includes a first operational amplifier and several resistors. The inverting input terminal of the first operational amplifier inputs the reference voltage signal, and after being divided by several resistors, inputs the first reference voltage signal. The first operational amplifier is used to compare the voltage values of the reference voltage signal and the first reference voltage signal, and output a first inverted signal with a voltage phase opposite to that of the reference voltage signal to the input terminal of the second operational amplifier circuit. The input terminal of the second operational amplifier circuit inputs the kV feedback signal, and is used to perform an error comparison between the reference voltage signal and the kV feedback signal, and output a first error compensation signal with the same voltage phase as the reference voltage signal.

[0010] A further solution is that the second operational amplifier circuit includes a third operational amplifier circuit and a fourth operational amplifier circuit. The input terminal of the third operational amplifier circuit inputs the first error compensation signal, and is used to perform an error comparison between the first error compensation signal and the resonant current feedback signal, and output a second inverted signal to the fourth operational amplifier circuit. The fourth operational amplifier circuit is used to invert the second inverted signal and output the second error compensation signal.

[0011] A further solution is that the fourth operational amplifier circuit includes a fourth operational amplifier and several resistors. The inverting input terminal of the fourth operational amplifier inputs the second inverted signal, and after being divided by several resistors, inputs the second reference voltage signal. The fourth operational amplifier is used to compare the magnitudes of the voltage values of the second inverted signal and the second reference voltage signal, and output the signal with the smaller voltage value as the second error compensation signal, which is used to limit the maximum frequency output of the resonant circuit.

[0012] A further solution is that the resonant current sampling circuit includes a first current transformer and a first rectifier circuit. The first transformer is used to sense the resonant current of the resonant converter and convert the resonant current into a first AC induced voltage and output it to the first rectifier circuit. The first rectifier circuit is used to rectify the first AC induced voltage and output the resonant current feedback signal.

[0013] A further solution is that a resonant current overlimit protection circuit is further included. The resonant current overlimit protection circuit includes a first voltage comparator and several resistors. The inverting input terminal of the first voltage comparator inputs the resonant current feedback signal, and its non-inverting input terminal inputs a third reference voltage signal after being divided by several resistors. The first voltage comparator is used to compare the voltage values of the resonant current feedback signal and the third reference voltage signal, and output a first level signal to the main control module of the DR high-voltage generator according to the comparison result to achieve overlimit protection of the resonant current.

[0014] A further solution is that it further includes an inverter current sampling circuit and an inverter current over-limit protection circuit. The inverter current sampling circuit is used to sample and rectify the inverter current in the resonant converter and then output an inverter current feedback signal to the inverter current over-limit protection circuit. The inverter current over-limit protection circuit also inputs a fourth reference voltage signal, and is used to compare the voltage value of the inverter current feedback signal with the voltage value of the fourth reference voltage signal, and output a second level signal to the main control module of the DR high-voltage generator according to the comparison result, so as to realize the over-limit protection of the inverter current.

[0015] A high-voltage generator based on double closed-loop error compensation includes a main control module, an inverter drive circuit based on double closed-loop error compensation, a resonant converter, a step-up transformer, and a voltage multiplier rectifier circuit. The main control module is used to output a reference voltage signal to the inverter drive circuit. The inverter drive circuit performs error compensation respectively according to the voltage and current signals fed back by the kV voltage feedback loop and the resonant current feedback loop, and outputs a PFM drive signal to the resonant converter. The output end of the resonant converter is connected to the primary side of the step-up transformer, and is used to control the on and off of its switching tubes according to the PFM drive signal to realize power inversion. The secondary side of the step-up transformer is connected to the voltage multiplier rectifier circuit, and is used to provide high-voltage direct current for the X-ray tube.

[0016] A further solution is that the resonant converter adopts an LCC resonant topology, including a full-bridge inverter circuit and an LCC series resonant circuit. The full-bridge circuit includes the switching tubes provided on each bridge arm, and the on and off of the switching tubes are controlled by the PFM drive signal to invert direct current into alternating current for output. The LCC series resonant circuit includes a first resonant capacitor, a second resonant capacitor, and a resonant inductor, and different resonant frequencies are provided by adjusting the values of the first resonant capacitor, the second resonant capacitor, and the resonant inductor.

[0017] Therefore, the present invention has the following beneficial effects:

[0018] 1. The inverter drive circuit of the present invention performs precise error compensation on the LCC topology drive by designing a voltage-current double closed-loop feedback loop. Compared with the traditional single closed-loop feedback method, by simultaneously controlling the double-loop feedback of voltage and current, the fluctuations and distortions of the output voltage and current can be effectively reduced, thereby significantly improving the stability and output accuracy of the system.

[0019] 2. The inverter drive circuit of the present invention uses MC34067DW as the drive control chip, replacing the traditional discrete component-based VCO circuit. It has high-performance zero-voltage switching resonant mode control, which helps reduce switching losses, improve conversion efficiency, and reduce electromagnetic interference, thereby enhancing the overall performance and reliability of the power supply system. It has a high-gain wide-bandwidth error amplifier and temperature compensation reference, which helps improve the stability and response speed of the power supply system, ensure the accuracy and stability of the output voltage, and adapt to different working environment temperature changes. It has a variable frequency oscillator and an accurate one-shot timer, enabling wide-range control and adjustment.

[0020] 3. The inverter drive circuit of the present invention can achieve overcurrent protection for the resonant current and inverter current by designing a resonant current overcurrent protection circuit and an inverter current overcurrent protection circuit.

[0021] 4. The high-voltage generator of the present invention uses the LCC resonant soft-switching method for inverter drive, and performs high-frequency switching according to the drive PFM signal. Compared with the traditional hard-switching, which generates certain energy losses during the switching process, it can achieve higher power conversion efficiency, reduce energy losses, and improve reliability and lifespan.

[0022] The following further elaborates on the present invention in detail with reference to the accompanying drawings and specific embodiments. Description of the Drawings

[0023] Figure 1 is a schematic diagram of a high-voltage generator in the prior art.

[0024] Figure 2 is a schematic diagram of the inverter drive circuit based on double-loop error compensation of the present invention.

[0025] Figure 3 is a schematic diagram of the first operational amplifier circuit of the present invention.

[0026] Figure 4 is a schematic diagram of the second operational amplifier circuit of the present invention.

[0027] Figure 5 is a schematic diagram of the inverter drive control circuit of the present invention.

[0028] Figure 6 is a schematic diagram of the inverter drive circuit of the present invention.

[0029] Figure 7 is a schematic diagram of the resonant current sampling circuit and the resonant current overcurrent protection circuit of the present invention.

[0030] Figure 8 is a schematic diagram of the inverter current sampling circuit and the inverter current overcurrent protection circuit of the present invention.

[0031] Figure 9 It is the schematic diagram of the drive enable circuit of the present invention.

[0032] Figure 10 It is the schematic diagram of the high-voltage generator of the present invention.

[0033] Figure 11 It is the schematic diagram of the resonant converter, step-up transformer and voltage-doubling rectifier circuit of the present invention. Detailed implementation manners

[0034] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0035] Embodiment of an inverter drive circuit based on double closed-loop error compensation

[0036] Refer to Figure 2 , the inverter drive circuit based on double closed-loop error compensation involved in the present invention is used to provide a drive signal for the resonant converter in a DR high-voltage generator, and includes a first operational amplifier circuit 10, a second operational amplifier circuit 20, a drive control circuit 30, a drive circuit 40 and a resonant current sampling circuit 50. A reference voltage signal KV_REF is input to the input end of the first operational amplifier circuit 10, and a kV voltage feedback loop is formed by connecting with the voltage-doubling rectifier circuit 105 of the high-voltage generator to obtain a kV feedback signal KVFBK. The first operational amplifier circuit 10 is used to operate the reference voltage signal KV_REF and the kV feedback signal KVFBK and then output a first error compensation signal U19B_OUT to the input end of the second operational amplifier circuit 20. The input end of the second operational amplifier circuit 20 is connected to the output end of the resonant converter through the resonant current sampling circuit 50 to form a resonant current feedback loop to obtain a resonant current feedback signal CURRENT BACK. The second operational amplifier circuit 20 is used to operate the first error compensation signal U19B_OUT and the resonant current feedback signal CURRENT BACK and then output a second error compensation signal VSET to the drive control circuit 30. The drive control circuit 30 is used to output a PFM modulation signal to the drive circuit 40 according to the second error compensation signal VSET. The drive circuit 40 is used to process the PFM modulation signal and output a PFM drive signal to the resonant converter.

[0037] Refer to Figure 3 , in this embodiment, the first operational amplifier circuit 10 is a YTPE3 type loop compensation circuit.

[0038] Specifically, in this embodiment, the kV feedback signal KVFBK is output after error compensation via a YTPE3 type loop compensation circuit. Circuit analysis and adjustment are performed to ensure that the transfer function of the compensation network can meet the stability and performance requirements of the system.

[0039] Among them, through circuit analysis, information about the setting positions of the zeros and poles can be obtained, and by precisely adjusting the positions of the zeros and poles, type-3 compensation can effectively increase the phase margin of the system, thereby enhancing the system's stability and preventing oscillation and unstable behavior; by designing the unity-gain bandwidth and parasitic zeros of the operational amplifier, type-3 compensation can optimize the frequency response of the operational amplifier, ensure that the signal is transmitted within the expected frequency range, and avoid signal distortion or phase shift; through appropriate compensation design, the overall performance of the system can be improved, including reducing noise and improving signal quality.

[0040] In this embodiment, the first operational amplifier circuit 10 includes a first operational amplifier circuit and a second operational amplifier circuit. The first operational amplifier circuit includes a first operational amplifier U19A and several resistors. The inverting input terminal of the first operational amplifier U19A inputs the reference voltage signal KV_REF, and after being divided by several resistors, it inputs a first reference voltage signal. The first operational amplifier U19A is used to compare the voltage values of the reference voltage signal KV_REF and the first reference voltage signal, and outputs a first inverted signal U19A_OUT with a voltage phase opposite to that of the reference voltage signal KV_REF to the input terminal of the second operational amplifier circuit. The input terminal of the second operational amplifier circuit inputs the kV feedback signal KVFBK, which is used to perform an error comparison between the reference voltage signal KV_REF and the kV feedback signal KVFBK, and outputs a first error compensation signal U19B_OUT with a voltage phase the same as that of the reference voltage signal KV_REF.

[0041] Specifically, the first operational amplifier circuit in this embodiment further includes clamping diodes D2 to D5. The first reference voltage signal includes V+12 and V-12 direct currents. V+12 direct current is respectively connected to the cathodes of diodes D3 and D5, and the anodes of diodes D3 and D5 are respectively connected to the non-inverting input terminal and the inverting input terminal of the first operational amplifier U19A through resistors R50 and R49; V-12 direct current is respectively connected to the anodes of diodes D2 and D4, and the cathodes of diodes D2 and D4 are respectively connected to the non-inverting input terminal and the inverting input terminal of the first operational amplifier U19A through resistors R50 and R49. It can be seen that diode D4 is for inverting clamping protection. When D4 is forward-biased, it causes the first operational amplifier U19A to output a negative full-scale output.

[0042] Specifically, the reference voltage signal KV_REF in this embodiment is connected to the inverting input terminal of the first operational amplifier U19A after being divided by resistors R47 and R49 in series. The output terminal of the first operational amplifier U19A is feedback-connected to its inverting input terminal through resistor R53. Then, the first inverted signal U19A_OUT output by it is:

[0043] U19A_OUT = -R53 * KV_REF / (R47 + R49)

[0044] Specifically, the first operational amplifier U19A in this embodiment uses an operational amplifier of model LF353D. Its positive and negative power input terminals are respectively input with V+12 and V-12 direct currents, and are respectively grounded through capacitors C43 and C42.

[0045] Specifically, the second operational amplifier circuit in this embodiment is a PID control circuit, which is used to adjust and control the value of the first error compensation signal U19B_OUT according to the deviation between its actual output value and the expected output value.

[0046] Specifically, the second operational amplifier circuit in this embodiment includes a second operational amplifier U19B, several resistors and capacitors. The first inverted signal U19A_OUT is input to the inverting input terminal of the second operational amplifier U19B after being divided by resistors R54 and R58 in series. The kV feedback signal KVFBK is input to the inverting input terminal of the second operational amplifier U19B after being adjusted by a resistor-capacitor circuit. The non-inverting input terminal of the second operational amplifier U19B is grounded through resistor R61, and its output terminal is feedback-connected to its inverting input terminal through a series circuit of capacitor C46 and resistor R62.

[0047] Among them, the resistor-capacitor circuit includes resistors R59, R155, R60 and capacitor C45. The series circuit of resistors R59 and R155 is in parallel with the series circuit of capacitor C45 and resistor R60. One end of this parallel circuit inputs the kV feedback signal KVFBK, and the other end is connected to the inverting input terminal of the second operational amplifier U19B.

[0048] Thus, the transfer function of the first operational amplifier circuit 10 is:

[0049]

[0050] It can be seen that the present invention uses a YTPE3 type loop compensation circuit combined with PID control to perform error compensation on the kV feedback signal KVFBK, which can achieve refined control and optimization while improving the stability and performance of the system.

[0051] See Figure 4, in this embodiment, the second operational amplifier circuit 20 includes a third operational amplifier circuit and a fourth operational amplifier circuit. The input terminal of the third operational amplifier circuit inputs a first error compensation signal U19B_OUT, which is used to perform an error comparison between the first error compensation signal U19B_OUT and the resonant current feedback signal CURRENT BACK, and output a second inverted signal to the fourth operational amplifier circuit. The fourth operational amplifier circuit is used to invert the second inverted signal and then output a second error compensation signal VSET.

[0052] Specifically, the third operational amplifier circuit in this embodiment is a PI control circuit, which is used to adjust and control the value of the second error compensation signal VSET according to the deviation between its actual output value and the expected output value.

[0053] Specifically, the third operational amplifier circuit in this embodiment includes a third operational amplifier U20A, several resistors and capacitors. The first error compensation signal U19B_OUT is input to the inverting input terminal of the third operational amplifier U20A after being divided by the series connection of resistors R63 and R65. The resonant current feedback signal CURRENT BACK is input to the inverting input terminal of the third operational amplifier U20A after being adjusted by a resistor-capacitor circuit. The non-inverting input terminal of the third operational amplifier U20A is grounded through a resistor R68, and its output terminal is respectively feedback to its inverting input terminal through the parallel connection of a capacitor C48 and a resistor R69.

[0054] Among them, the above resistor-capacitor circuit includes resistors R66, R67 and a capacitor C47. The series circuit of the capacitor C47 and the resistor R67 is connected in parallel with the resistor R66. One end of this parallel circuit inputs the resonant current feedback signal CURRENT BACK, and the other end is connected to the inverting input terminal of the third operational amplifier U20A.

[0055] Thus, the transfer function of the second operational amplifier circuit is:

[0056]

[0057] Among them, R4 = R63 + R65, R1 = R66, R2 = 69, R3 = 67,, C2 = 48, C3 = 47, V cur is the voltage value of the resonant feedback current signal, V e is the voltage value of the first error compensation signal U19B_OUT.

[0058] In this embodiment, the fourth operational amplifier circuit includes a fourth operational amplifier U20B and several resistors. The inverting input terminal of the fourth operational amplifier U20B inputs a second inverted signal, and after being divided by several resistors, a second reference voltage signal is input. The fourth operational amplifier U20B is used to compare the voltage values of the second inverted signal and the second reference voltage signal, and output the signal with the smaller voltage value as the second error compensation signal VSET, which is used to limit the maximum frequency output of the resonant circuit.

[0059] Specifically, the fourth operational amplifier circuit in this embodiment further includes a diode D10. The second inverted signal is input to the inverting input terminal of the fourth operational amplifier U20B after being clamped by the diode D10. The second reference voltage is -12V DC, which is grounded after being divided in series by resistors R72 and R73. One end of the resistor R70 is connected to the common connection terminal of the resistors R72 and R73, and the other end is connected to the inverting input terminal of the fourth operational amplifier U20B.

[0060] Among them, when the value of the second inverted signal is greater than the divided voltage signal value sent through the resistor R70, this divided voltage signal is used as the second error compensation signal VSET output by the fourth operational amplifier U20B to limit the maximum frequency output of the LCC topology; when the value of the second inverted signal is less than the divided voltage signal value, the second inverted signal is inverted and used as the second error compensation signal VSET output by the fourth operational amplifier U20B.

[0061] See Figure 5 , specifically, the drive control circuit 30 in this embodiment uses a PFM drive chip of model MC34067 to replace the traditional VCO circuit built with discrete components. It has high-performance zero-voltage-switching resonant mode control, which helps to reduce switching losses, improve conversion efficiency, and at the same time reduce electromagnetic interference, thereby improving the overall performance and reliability of the power supply system; it has a high-gain broadband error amplifier and a temperature compensation reference, which helps to improve the stability and response speed of the power supply system, ensure the accuracy and stability of the output voltage, and at the same time adapt to different working environment temperature changes; it has a variable-frequency oscillator and an accurate single-shot timer, which can achieve wide-range control and adjustment.

[0062] See Figure 9 , specifically, this embodiment further includes a drive enable circuit 90. The drive enable circuit 90 includes transistors Q2, Q4, and Q5. The control terminal of the transistor Q4 is connected to the total protection signal SAM FAULT from the main control module 101. Only when the level of the total protection signal SAM FAULT is not low, the transistor Q5 outputs a low-level drive enable signal KV_ON to the base of the transistor Q2.

[0063] Specifically, the output terminal of the first operational amplifier U19A in this embodiment is connected to the collector of the triode Q2. The base of the triode Q2 is connected to the drive enable signal KV_ON, and its emitter is connected to the V + 12 DC power supply through a voltage stabilizing diode. Only when the drive enable signal KV_ON is pulled low can the second operational amplifier U19B input the first inverting signal U19A_OUT for voltage compensation.

[0064] See Figure 6 , specifically, the drive circuit 40 in this embodiment uses two low-side ultra-fast driver chips of the model IXDD614CI. The input terminals of the two driver chips are respectively connected to the two drive signal output terminals of the PFM drive chip. It has characteristics such as low output impedance, low propagation delay, and fast rise and fall times, and is suitable for enhancing high-frequency and high-power PFM drive signals, and can efficiently drive switching tubes such as MOSFETs and IGBTs.

[0065] See Figure 7 , in this embodiment, the resonant current sampling circuit 50 includes a first current transformer T2 and a first rectification circuit. The first current transformer T2 is used to sense the resonant current of the resonant converter and convert the resonant current into a first AC induced voltage and output it to the first rectification circuit. The first rectification circuit is used to rectify the first AC induced voltage and then output the resonant current feedback signal CURRENT BACK.

[0066] Specifically, the first rectification circuit in this embodiment uses a full-bridge rectification circuit composed of diodes D11 - D14.

[0067] In this embodiment, a resonant current over-limit protection circuit 70 is further included. The resonant current over-limit protection circuit 70 includes a first voltage comparator U28 and several resistors. The inverting input terminal of the first voltage comparator U28 inputs the resonant current feedback signal CURRENT BACK, and its non-inverting input terminal inputs a third reference voltage signal after being divided by several resistors. The first voltage comparator U28 is used to compare the voltage value of the resonant current feedback signal CURRENT BACK with the voltage value of the third reference voltage signal, and output a first level signal CURRENT OVER to the main control module 101 of the DR high-voltage generator according to the comparison result to achieve over-limit protection of the resonant current.

[0068] Specifically, the third reference voltage signal in this embodiment is V - 12 DC power supply, and it is input to the non-inverting input terminal of the first voltage comparator U28 after being divided by the variable resistor RW2.

[0069] See Figure 8, in this embodiment, it further includes an inverter current sampling circuit 60 and an inverter current over-limit protection circuit 80. The inverter current sampling circuit 60 is used to sample and rectify the inverter current in the resonant converter and then output an inverter current feedback signal to the inverter current over-limit protection circuit 80. The inverter current over-limit protection circuit 80 also inputs a fourth reference voltage signal, and is used to compare the voltage value of the inverter current feedback signal with the voltage value of the fourth reference voltage signal, and output a second level signal to the main control module 101 of the DR high-voltage generator according to the comparison result, so as to achieve over-limit protection of the inverter current.

[0070] Specifically, the inverter current sampling circuit 60 in this embodiment includes a second current transformer T3 and a second rectifying circuit. The second current transformer T3 is used to sense the inverter current of the resonant converter and convert the inverter current into a second AC induced voltage and output it to the second rectifying circuit. The second rectifying circuit is used to rectify the second AC induced voltage and then output the inverter current feedback signal.

[0071] Among them, specifically, the first rectifying circuit in this embodiment adopts a half-wave rectifying circuit composed of a diode D15.

[0072] Specifically, the inverter current over-limit protection circuit 80 in this embodiment includes a second voltage comparator U29 and several resistors. The non-inverting input terminal of the second voltage comparator U29 inputs the inverter current feedback signal, and its inverting input terminal inputs the fourth reference voltage signal after being divided by several resistors. The second voltage comparator is used to compare the voltage value of the inverter current feedback signal with the voltage value of the fourth reference voltage signal, and output a second level signal INV_OVER to the main control module 101 of the DR high-voltage generator according to the comparison result, for over-limit protection of the inverter current.

[0073] Among them, the fourth reference voltage signal is +12V DC, and it is input to the inverting input terminal of the second voltage comparator U29 after being divided by a variable resistor RW1.

[0074] Specifically, the above-mentioned inverter drive circuit based on double closed-loop error compensation in this embodiment is applicable to the inverter drive of high-voltage generators for CBCT devices, security inspection types, and DR fluoroscopy types.

[0075] Embodiment of a high-voltage generator based on double closed-loop error compensation

[0076] See Figures 10 - 11, the high-voltage generator based on double closed-loop error compensation according to the present invention includes a main control module 101, an inverter drive circuit 100 based on double closed-loop error compensation, a resonant converter, a step-up transformer 104, and a voltage multiplier rectifier circuit 105. The main control module 101 is used to output a reference voltage signal KV_REF to the inverter drive circuit 100. The inverter drive circuit 100 performs error compensation respectively according to the voltage and current signals fed back by the kV voltage feedback loop and the resonant current feedback loop, and outputs a PFM drive signal to the resonant converter. The output end of the resonant converter is connected to the primary side of the step-up transformer 104, and is used to control the on-off of its switching tubes according to the PFM drive signal to realize power inversion. The secondary side of the step-up transformer 104 is connected to the voltage multiplier rectifier circuit 105, and is used to provide high-voltage direct current for the X-ray tube 200.

[0077] In this embodiment, the resonant converter adopts an LCC resonant topology, including a full-bridge inverter circuit 102 and an LCC series resonant circuit 103. The full-bridge circuit includes the switching tubes provided on each bridge arm, and the on-off of the switching tubes is controlled by the PFM drive signal to invert direct current into alternating current for output. The LCC series resonant circuit 103 includes a first resonant capacitor, a second resonant capacitor, and a resonant inductor, and different resonant frequencies are provided by adjusting the values of the first resonant capacitor, the second resonant capacitor, and the resonant inductor.

[0078] Specifically, this embodiment further includes a filament drive circuit 106, and the filament drive circuit 106 is used to provide a filament current for the filament of the X-ray tube 200.

[0079] The above-mentioned implementation manners are only the preferred implementation manners 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 those skilled in the art on the basis of the present invention belong to the scope of protection required by the present invention.

Claims

1. Inverter drive circuit based on double closed-loop error compensation, characterized in that, For providing a driving signal for a resonant converter in a DR high-voltage generator, including: A first operational amplifier circuit, a second operational amplifier circuit, a driving control circuit, a driving circuit, and a resonant current sampling circuit. The input end of the first operational amplifier circuit inputs a reference voltage signal and forms a kV voltage feedback loop by connecting with the voltage doubling and rectifying circuit of the high-voltage generator to obtain a kV feedback signal. The first operational amplifier circuit is used to operate the reference voltage signal and the kV feedback signal and then output a first error compensation signal to the input end of the second operational amplifier circuit. The input end of the second operational amplifier circuit is connected to the output end of the resonant converter through the resonant current sampling circuit to form a resonant current feedback loop to obtain a resonant current feedback signal. The second operational amplifier circuit is used to operate the first error compensation signal and the resonant current feedback signal and then output a second error compensation signal to the driving control circuit. The driving control circuit is used to output a PFM modulation signal to the driving circuit according to the second error compensation signal. The driving circuit is used to process the PFM modulation signal and output a PFM driving signal to the resonant converter.

2. The inverter driving circuit based on double closed-loop error compensation according to claim 1, wherein: The first operational amplifier circuit is a YTPE3 type loop compensation circuit.

3. The inverter driving circuit based on double closed-loop error compensation according to claim 2, wherein: The first operational amplifier circuit includes a first operational amplifier circuit and a second operational amplifier circuit. The first operational amplifier circuit includes a first operational amplifier and several resistors. The inverting input end of the first operational amplifier inputs the reference voltage signal and inputs a first reference voltage signal after voltage division by several resistors. The first operational amplifier is used to compare the voltage values of the reference voltage signal and the first reference voltage signal and output a first inverted signal with a voltage phase opposite to that of the reference voltage signal to the input end of the second operational amplifier circuit. The input end of the second operational amplifier circuit inputs the kV feedback signal and is used to compare the error between the reference voltage signal and the kV feedback signal and output the first error compensation signal with the same voltage phase as the reference voltage signal.

4. The inverter driving circuit based on double closed-loop error compensation according to claim 1, wherein: The second operational amplifier circuit includes a third operational amplifier circuit and a fourth operational amplifier circuit. The input end of the third operational amplifier circuit inputs the first error compensation signal and is used to compare the error between the first error compensation signal and the resonant current feedback signal and output a second inverted signal to the fourth operational amplifier circuit. The fourth operational amplifier circuit is used to invert the second inverted signal and then output the second error compensation signal.

5. The inverter driving circuit based on double closed-loop error compensation according to claim 4, wherein: The fourth operational amplifier circuit includes a fourth operational amplifier and several resistors. The inverting input terminal of the fourth operational amplifier inputs the second inverted signal, and after being divided by several resistors, inputs the second reference voltage signal. The fourth operational amplifier is used to compare the voltage values of the second inverted signal and the second reference voltage signal, and output the signal with the smaller voltage value as the second error compensation signal, which is used to limit the maximum frequency output of the resonant circuit.

6. The inverter drive circuit based on double closed-loop error compensation according to claim 1, wherein: The resonant current sampling circuit includes a first current transformer and a first rectifier circuit. The first transformer is used to sense the resonant current of the resonant converter and convert the resonant current into a first AC induced voltage and output it to the first rectifier circuit. The first rectifier circuit is used to rectify the first AC induced voltage and output the resonant current feedback signal.

7. The inverter drive circuit based on double closed-loop error compensation according to claim 6, wherein: It further includes a resonant current overlimit protection circuit. The resonant current overlimit protection circuit includes a first voltage comparator and several resistors. The inverting input terminal of the first voltage comparator inputs the resonant current feedback signal, and its non-inverting input terminal inputs the third reference voltage signal after being divided by several resistors. The first voltage comparator is used to compare the voltage values of the resonant current feedback signal and the third reference voltage signal, and output a first level signal to the main control module of the DR high-voltage generator according to the comparison result to achieve overlimit protection of the resonant current.

8. The inverter drive circuit based on double closed-loop error compensation according to claim 1, wherein: It further includes an inverter current sampling circuit and an inverter current overlimit protection circuit. The inverter current sampling circuit is used to sample and rectify the inverter current in the resonant converter and output the inverter current feedback signal to the inverter current overlimit protection circuit. The inverter current overlimit protection circuit also inputs a fourth reference voltage signal, which is used to compare the voltage values of the inverter current feedback signal and the fourth reference voltage signal, and output a second level signal to the main control module of the DR high-voltage generator according to the comparison result to achieve overlimit protection of the inverter current.

9. The high-voltage generator based on double closed-loop error compensation is characterized in that Comprising: A main control module, the inverter drive circuit based on double closed-loop error compensation according to any one of claims 1 to 8, a resonant converter, a step-up transformer, and a voltage multiplier rectifier circuit. The main control module is used to output a reference voltage signal to the inverter drive circuit. The inverter drive circuit respectively performs error compensation according to the voltage and current signals fed back by the kV voltage feedback loop and the resonant current feedback loop, and outputs a PFM drive signal to the resonant converter. The output terminal of the resonant converter is connected to the primary side of the step-up transformer, and is used to control the on-off of its switching tube according to the PFM drive signal to achieve power inversion. The secondary side of the step-up transformer is connected to the voltage multiplier rectifier circuit, which is used to provide high-voltage direct current for the X-ray tube.

10. The high-voltage generator based on double closed-loop error compensation according to claim 9, wherein: The resonant converter adopts an LCC resonant topology, including a full-bridge inverter circuit and an LCC series resonant circuit. The full-bridge circuit includes the switching tubes provided on each arm. The on-off of the switching tubes is controlled by the PFM drive signal to invert direct current into alternating current for output. The LCC series resonant circuit includes a first resonant capacitor, a second resonant capacitor, and a resonant inductor. Different resonant frequencies are provided by adjusting the values of the first resonant capacitor, the second resonant capacitor, and the resonant inductor.

Images