Current conditioning method and circuit, power conversion circuit and electrical equipment

Abstract

The present invention provides a current conditioning method and circuit, a power conversion circuit, and electrical equipment. The current conditioning method first merges, stores, and outputs noise and current signals obtained by conversion sampling, and then synthesizes low-energy secondary voltage noise of different time sequences and a high-energy primary current signal reflecting the switching timing of the inverter into a single monotonic single-value boost signal in which the primary current signal plays a dominant role in timing and intensity and can reflect the magnitude of the primary current of the current transformer. At the same time, when the output voltage rises to a second preset voltage, discharge and voltage stabilization processing are performed, so that the output voltage returns to a monotonic single-value step-down signal with a constant negative value within at most half a PWM cycle, thereby forming a noise-free triangular wave voltage signal that is proportional to the magnitude of the primary current of the current transformer and has the same frequency and phase as the primary current of the current transformer, thereby improving the reliability of inverter control, avoiding false triggering and false protection, and ensuring the safety and normal operation of the inverter.

Description

Technical Field

[0001] The present invention belongs to the technical field of current conditioning, and in particular relates to a current conditioning method and circuit, a power conversion circuit and electrical equipment. Background Art

[0002] The current transformer realizes current sensing and completes tasks such as current sampling and conversion output. Among them, the secondary current of the current transformer can be transformed, filtered and proportionally conditioned by the current conditioning circuit to obtain the required voltage signal. The voltage signal can be used to control the conduction time of the power tube of the inverter.

[0003] Among them, current transformers are divided into low-frequency and high-frequency types. There are usually two types of current conditioning circuits for low-frequency current transformers used for power consumption measurement.

[0004] The first method is to perform half-wave or full-wave rectification (or no rectification) on the secondary side of the current transformer, and then connect a filter capacitor and a resistor divider branch in parallel to achieve current-to-voltage conversion. Finally, a voltage signal proportional to the primary current signal is obtained through the voltage divider resistor, which can be used for power consumption or overcurrent detection.

[0005] The second method uses an additional circuit composed of components such as operational amplifiers to further process the voltage signal obtained by resistor voltage division in the first current conditioning circuit, and ultimately obtains an analog voltage signal that meets the requirements of subsequent circuit interfaces and can be used for power consumption or overcurrent detection.

[0006] In addition, the high-frequency current transformer used for peak current detection usually also uses a secondary current conditioning circuit similar to the above-mentioned low-frequency current transformer to obtain a shutdown disable voltage signal for protecting the normal operation of the inverter power tube.

[0007] However, in practical applications, conventional current conditioning circuits are only suitable for low-frequency and medium-to-low-power inverters that generate relatively low-energy EMI interference. When the inverter frequency is high and the output power is large, the serious EMI interference problem caused by itself makes the sampling signal of the current transformer obtained noisy, which may cause the inverter to be misprotected and hinder its reliable and normal power conversion. Summary of the Invention

[0008] The purpose of the present invention is to provide a current conditioning method, which aims to solve the problem that when a traditional current conditioning circuit is applied to a high-frequency inverter, the sampling signal obtained has high noise, resulting in incorrect protection of the inverter and failure to operate safely and normally.

[0009] A first aspect of an embodiment of the present invention provides a current conditioning method, which is applied to a current conditioning circuit, wherein the current conditioning circuit is connected to an inverter via a current transformer. The current conditioning method includes:

[0010] In the initial state, the current conditioning circuit is triggered to maintain a voltage stabilization mode, wherein the voltage stabilization mode is: the current conditioning circuit is triggered to shut down its own discharge channel and stabilize the output voltage to a first preset voltage, wherein the first preset voltage is less than 0V;

[0011] At an on-time point in each PWM cycle of the inverter, the current conditioning circuit is triggered to switch to a forward charging mode, wherein the forward charging mode is to obtain a voltage noise signal and a switching current signal of the inverter through the current transformer and perform charging, energy storage, and boost output;

[0012] When the output voltage rises to a second preset voltage after charging, the current conditioning circuit is triggered to switch to a discharge mode. The discharge mode is as follows: the discharge channel is triggered to conduct to perform a discharge operation, and the current is discharged to 0V after the off time point in each PWM cycle of the inverter, and the current is switched to reverse charging and step-down output.

[0013] After the output voltage is triggered to be stepped down to the first preset voltage before the start time point of the next PWM cycle, the current conditioning circuit is triggered to switch to the voltage regulation mode.

[0014] Optionally, T1+T2+T3≤T0;

[0015] Among them, T0 is the duration of a single PWM cycle, T1 is the forward charging duration in a single PWM cycle, T2 is the discharge duration in a single PWM cycle, and T3 is the reverse charging duration in a single PWM cycle.

[0016] A second aspect of an embodiment of the present invention provides a current conditioning circuit applied to a current transformer, wherein an inverter, the current transformer, and the current conditioning circuit are connected in sequence, and the current conditioning circuit includes a resistor-capacitor circuit and a discharge voltage stabilizing circuit connected in sequence;

[0017] The input end of the RC circuit is connected to the secondary winding of the current transformer, and the discharge voltage stabilizing circuit is connected in parallel to the output end of the RC circuit. In an initial state, the discharge channel of the RC circuit is triggered to be shut off, and the output end of the RC circuit is stabilized to a first preset voltage, which is less than 0V.

[0018] The RC circuit is configured to acquire the voltage noise signal and the switching current signal of the inverter through the current transformer at the start time point within each PWM cycle of the inverter to perform forward charging, energy storage and boost output;

[0019] The discharge voltage stabilizing circuit is configured to be triggered to conduct when the forward output voltage of the RC circuit rises to a second preset voltage, so as to provide a discharge channel;

[0020] The RC circuit is further configured to discharge through the discharge voltage stabilizing circuit after the output voltage rises to a second preset voltage, and to start reverse charging at a turn-off time point in each PWM cycle of the inverter, and to discharge to 0V after the turn-off time point in each PWM cycle of the inverter, and to switch to reverse charging and step-down output;

[0021] The discharge voltage stabilization circuit is further configured to trigger voltage stabilization when the output voltage of the resistor-capacitor circuit drops to the first preset voltage, and stabilize the output voltage of the resistor-capacitor circuit to the first preset voltage.

[0022] Optionally, the resistance-capacitance circuit includes a capacitor and a first resistor;

[0023] The first end of the capacitor is connected to the first end of the secondary winding of the current transformer, the second end of the capacitor is connected to the first end of the first resistor, and the second end of the first resistor is connected to the second end of the secondary winding of the current transformer;

[0024] Or the first end of the first resistor is connected to the first end of the secondary winding of the current transformer, the second end of the first resistor is connected to the first end of the capacitor, and the second end of the capacitor is connected to the second end of the secondary winding of the current transformer.

[0025] Optionally, the discharge voltage stabilization circuit includes a Zener diode and a second resistor;

[0026] The cathode of the Zener diode is connected to the first end of the capacitor, the anode of the Zener diode is connected to the first end of the second resistor, and the second end of the second resistor is connected to the second end of the capacitor.

[0027] Optionally, the current conditioning circuit further includes:

[0028] A potential boosting circuit connected to the signal output end of the current conditioning circuit, wherein the potential boosting circuit is configured to positively boost the voltage signal output by the current conditioning circuit to a preset voltage threshold and output it, wherein the preset voltage threshold range is V3 to V4, wherein V4 is greater than V3, and V3 ≥ 0V.

[0029] Optionally, the current conditioning circuit further includes:

[0030] The scaling circuit connected to the signal output terminal of the current conditioning circuit is configured to scale and output the voltage signal output by the current conditioning circuit.

[0031] A third aspect of an embodiment of the present invention provides a power conversion circuit, comprising an inverter, a current transformer, and the current conditioning circuit as described above, wherein the inverter, the current transformer, and the current conditioning circuit are connected in sequence.

[0032] A fourth aspect of the embodiments of the present invention provides an electrical device, comprising the power conversion circuit as described above.

[0033] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: the above-mentioned current conditioning method first merges, stores, and outputs the noise and the current signal obtained by conversion sampling, and synthesizes the low-energy secondary voltage noise of different time sequences and the high-energy main current signal reflecting the inverter switching time sequence into a single monotonic single-value boost signal in which the main current signal plays a dominant role in timing and intensity and can reflect the magnitude of the primary current of the current transformer. At the same time, when the output voltage rises to a second preset voltage, discharge and voltage stabilization processing are performed, so that the output voltage returns to a monotonic single-value step-down signal with a constant negative value within at most half a PWM cycle, thereby forming a noise-free triangular wave voltage signal that is proportional to the magnitude of the primary current of the current transformer and has the same frequency and phase as the primary current, thereby improving the control reliability of the inverter, avoiding false triggering and false protection, and ensuring the safety and normal operation of the inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of a first module of a current conditioning circuit provided by an embodiment of the present invention;

[0035] Figure 2 A schematic flow chart of a current conditioning method provided in an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of a voltage signal waveform of a current conditioning method provided by an embodiment of the present invention;

[0037] Figure 4 A second module schematic diagram of the current conditioning circuit provided by an embodiment of the present invention;

[0038] Figure 5 A first circuit diagram of a current conditioning circuit provided by an embodiment of the present invention;

[0039] Figure 6 A second circuit diagram of the current conditioning circuit provided by an embodiment of the present invention;

[0040] Figure 7 A third module schematic diagram of the current conditioning circuit provided by an embodiment of the present invention;

[0041] Figure 8 A schematic diagram of a first waveform change of a voltage signal of a current conditioning circuit provided by an embodiment of the present invention;

[0042] Figure 9 A fourth module schematic diagram of the current conditioning circuit provided by an embodiment of the present invention;

[0043] Figure 10 This is a schematic diagram of the second waveform change of the voltage signal of the current conditioning circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0046] A first aspect of an embodiment of the present invention provides a current conditioning method, which is applied to a current conditioning circuit 100 .

[0047] like Figure 1 As shown, the current conditioning circuit 100 is connected to the inverter 200 through the current transformer CT and obtains the current signal after proportional conversion. In order to realize the conditioned output of the current signal to provide a sampling signal or a reference signal to the subsequent module or the control circuit of the inverter 200, and at the same time, to avoid the noise signal from interfering with the control of the inverter 200, a current conditioning method is proposed, such as Figure 2 As shown, the current conditioning methods include:

[0048] Step S10: In the initial state, the current conditioning circuit 100 is triggered to maintain a voltage stabilization mode. The voltage stabilization mode is: the current conditioning circuit 100 is triggered to shut down its own discharge channel and stabilize the output voltage to a first preset voltage V1, which is less than 0V.

[0049] Step S20: At the on-time point in each PWM cycle of the inverter 200, the current conditioning circuit 100 is triggered to switch to the forward charging mode. The forward charging mode is as follows: the voltage noise signal and the switching current signal of the inverter 200 are obtained through the current transformer CT and charging and energy storage and boost output are performed;

[0050] Step S30: When the output voltage rises to the second predetermined voltage V2 after charging, the current conditioning circuit 100 is triggered to switch to a discharge mode. The discharge mode is as follows: the discharge channel is triggered to conduct to perform a discharge operation, and the voltage is discharged to 0V after the off time point in each PWM cycle of the inverter 200, and the current is switched to reverse charging and step-down output.

[0051] Step S40 : After the output voltage is triggered to drop to the first preset voltage V1 before the start time point of the next PWM cycle, the current conditioning circuit 100 is triggered to switch to the voltage regulation mode.

[0052] In this embodiment, in the initial state, that is, when the inverter 200 is not performing an inverter conversion, the current conditioning circuit 100 is maintained in a voltage regulation mode, and stabilizes the output voltage of its own output end at a first preset voltage V1, and triggers switching to a corresponding operating mode when the inverter 200 is performing an inverter conversion.

[0053] Specifically, refer to Figure 1 and Figure 3 When the PWM cycle of the inverter 200 switches to the on time point, the inverter 200 is in the on state. At this time, when the first end S3 of the secondary winding of the current transformer CT is positive and the second end S4 is negative, the output voltage of the current conditioning circuit 100 is the first preset voltage V1, that is, point P0. At this time, the current conditioning circuit 100 triggers the switch to the forward charging mode and starts to obtain the voltage noise signal and the switching current signal of the inverter 200 through the current transformer CT to perform forward charging and energy storage. The charging time constant is τ1=R1C1, which is determined by the resistance and capacitance values ​​of the charging energy storage module in the current conditioning circuit 100. The output end of the current conditioning circuit 100 gradually rises from the negative voltage first preset voltage V1 to 0V, and then continues to gradually rise at a preset slope, and rises to the second preset voltage V2 at the first time point, that is, Figure 3 At point P1, a monotonic single-value boost signal V1~V2 is formed, which realizes the merging, storage and output of the noise signal and the current signal obtained by conversion sampling, and synthesizes the secondary voltage noise with low energy of different timing and the main current signal with high energy that reflects the switching timing of the inverter 200 into a single monotonic single-value boost signal in which the timing and intensity are dominated by the main current signal. The monotonic single-value boost signal can reflect the primary current of the current transformer CT, thereby submerging the low-energy noise in the high-energy current signal without interfering, and eliminates the difference in timing between the two signals through the charging time effect. The current signal is effectively and proportionally converted into a ramp voltage signal that can be used as the output voltage at the output end of the resistor-capacitor circuit 10, and the ramp voltage signal rises monotonically and linearly with a single value.

[0054] At the same time, when the output terminal voltage of the current conditioning circuit 100 reaches the second preset voltage V2, the current conditioning circuit 100 is triggered to switch to the discharge mode, and the charge stored in the current conditioning circuit 100 begins to discharge through its own discharge channel. The discharge time constant is τ2=R2C1, where R2 represents the resistance of the discharge channel, and C1 represents the capacitance of the charging energy storage module in the current conditioning circuit 100. As the discharge proceeds, the output terminal voltage of the current conditioning circuit 100 gradually decreases until the closing time point of the PWM cycle, that is, Figure 3 Point P2 in .

[0055] Due to the requirement for resetting the magnetic flux of the current transformer CT within a switching cycle, during the off time of the PWM cycle, the first end S3 of the secondary winding of the current transformer CT becomes negative and the second end S4 becomes positive, so that the excitation energy and leakage inductance energy of the current transformer CT are gradually released. At the same time, during the process of releasing the excitation energy and leakage inductance energy of the current transformer CT, the discharge channel of the current conditioning circuit 100 continues to discharge until the voltage at the output end drops from the positive voltage to 0V, and then the current conditioning circuit 100 switches to reverse charging.

[0056] When the reverse voltage formed at the output end of the current conditioning circuit 100 due to reverse charging reaches the first preset voltage V1, the current conditioning circuit 100 is triggered to switch to the voltage regulation mode, so that the reverse voltage at the output end of the current conditioning circuit 100 is maintained at the first preset voltage V1 until the turn-on time point of the next PWM cycle arrives, so that the output voltage returns to a monotonic single-value step-down signal with a constant negative value within at most half a PWM cycle, and returns to the constant negative voltage return state. During this period, the inverter 200 does not transmit energy.

[0057] When the next PWM cycle starts, the entire process is repeated, thereby forming a noise-free triangular wave voltage signal that is proportional to the primary current of the current transformer CT and has the same frequency as the primary current of the current transformer CT.

[0058] The triangular wave voltage signal is used to indirectly detect the primary current of the inverter 200 and can be used as a sampling signal to further achieve reliable control of the inverter 200 to prevent false triggering and false protection.

[0059] Furthermore, in order to ensure reliable output of the triangular wave voltage signal, optionally, T1+T2+T3≤T0;

[0060] Among them, T0 is the duration of a single PWM cycle, T1 is the forward charging duration within a single PWM cycle, T2 is the discharge duration within a single PWM cycle, and T3 is the reverse charging duration within a single PWM cycle.

[0061] By setting the corresponding parameters, the sum of the voltage rise time, voltage discharge time and reverse charge time is less than or equal to the PWM period, thereby ensuring that the output voltage of the current conditioning circuit 100 stably drops to the first preset voltage V1 within each period, thereby achieving periodic change.

[0062] In this embodiment, the current conditioning method first merges, stores, and outputs the noise and the current signal obtained by conversion sampling, and then synthesizes the low-energy secondary voltage noise of different time sequences and the high-energy main current signal reflecting the switching timing of the inverter 200 into a single monotonic single-valued boost signal in which the main current signal plays a dominant role in timing and intensity and can reflect the magnitude of the primary current of the current transformer CT. At the same time, when the output voltage rises to the second preset voltage V2, discharge and voltage stabilization are performed, so that the output voltage returns to a monotonic single-valued step-down signal with a constant negative value within at most half a PWM cycle, thereby forming a noise-free triangular wave voltage signal that is proportional to the magnitude of the primary current of the current transformer CT and has the same frequency as it. This improves the control reliability of the inverter 200, avoids false triggering and false protection, and ensures the safety and normal operation of the inverter.

[0063] The second aspect of the embodiment of the present invention provides a current conditioning circuit 100, which is applied to a current transformer CT, such as Figure 1 As shown, the inverter 200, the current transformer CT and the current conditioning circuit 100 are connected in sequence.

[0064] Among them, such as Figure 4 As shown, the current conditioning circuit 100 includes a resistor-capacitor circuit 10 and a discharge voltage stabilizing circuit 20 connected in sequence;

[0065] The input end of the RC circuit 10 is connected to the secondary winding of the current transformer CT. The discharge voltage stabilizing circuit 20 is connected in parallel to the output end of the RC circuit 10 and triggers to shut off its own discharge channel in the initial state and stabilize the output end of the RC circuit 10 to a first preset voltage V1, which is less than 0V.

[0066] The RC circuit 10 is configured to obtain the voltage noise signal and the switching current signal of the inverter 200 through the current transformer CT at the start time point of each PWM cycle of the inverter 200 to perform positive charging energy storage and boost output;

[0067] The discharge voltage stabilizing circuit 20 is configured to be triggered to conduct when the forward output voltage of the RC circuit 10 rises to a second preset voltage V2, so as to provide a discharge channel;

[0068] The RC circuit 10 is further configured to discharge through the discharge voltage stabilizing circuit 20 after the output voltage rises to the second preset voltage V2, and to start reverse charging at the off time point in each PWM cycle of the inverter 200, and to discharge to 0V after the off time point in each PWM cycle of the inverter 200, and to switch to reverse charging and step-down output;

[0069] The discharge voltage stabilization circuit 20 is further configured to trigger voltage stabilization when the output voltage of the RC circuit 10 drops to the first preset voltage V1, and stabilize the output voltage of the RC circuit 10 to the first preset voltage V1.

[0070] In this embodiment, in the initial state, when the current conditioning circuit 100 does not perform current-to-voltage conversion, the discharge voltage stabilizing circuit 20 works and reverse-stabilizes the output end of the resistor-capacitor circuit 10 at the first preset voltage V1, and is switched to the corresponding working state when the inverter 200 performs the inverter conversion.

[0071] Specifically, refer to Figure 3 and Figure 4 When the PWM cycle of the inverter 200 switches to the on time point, the inverter 200 is in the on state. At this time, when the first end S3 of the secondary winding of the current transformer CT is positive and the second end S4 is negative, the output terminal voltage of the RC circuit 10 is the first preset voltage V1, that is, point P0, and the RC circuit 10 begins to charge in the forward direction. The charging time constant is τ1=R1C1, which is determined by the resistance and capacitance values ​​of the RC circuit 10. The output terminal of the RC circuit 10 gradually rises from the negative first preset voltage V1 to 0V, and then continues to gradually rise at a preset slope, and rises to the second preset voltage V2 at the first time point, that is, Figure 3 At point P1, a monotonic single-value boost signal V1~V2 is formed, which realizes the storage of noise and the current signal obtained by conversion sampling at the output end of the resistor-capacitor circuit 10, and synthesizes the secondary voltage noise with low energy of different timings and the main current signal with high energy that reflects the switching timing of the inverter 200 into a single monotonic single-value boost signal in which the timing and intensity are dominated by the main current signal. The monotonic single-value boost signal can reflect the primary current of the current transformer CT, thereby drowning the low-energy noise in the high-energy current signal without interference, and eliminates the difference in timing between the two signals through the charging time effect. The current signal is effectively and proportionally converted into a ramp voltage signal at the output end of the resistor-capacitor circuit 10, which can be used as the output voltage. The ramp voltage signal rises monotonically and approximately linearly with a single value.

[0072] At the same time, when the output terminal voltage of the RC circuit 10 reaches the second preset voltage V2, at this time, the discharge voltage stabilizing circuit 20 receives the forward voltage of the RC circuit 10, triggers conduction and switches to the discharge mode, and the charge stored in the RC circuit 10 begins to discharge through the discharge voltage stabilizing circuit 20. The discharge time constant is τ2=R2C1, wherein R2 represents the resistance of the discharge voltage stabilizing circuit 20, and C1 represents the capacitance of the RC circuit 10. At the same time, the discharge current flowing through the discharge voltage stabilizing circuit 20 includes the discharge current of the RC circuit 10 and the forward current applied by the secondary side of the current transformer CT. As the discharge proceeds, the output terminal voltage of the RC circuit 10 gradually decreases until the closing time point of the PWM cycle, that is, Figure 3 Point P2 in .

[0073] Due to the requirement of resetting the magnetic flux of the current transformer CT within a switching cycle, during the off time of the PWM cycle, the first end S3 of the secondary winding of the current transformer CT becomes negative and the second end S4 becomes positive, so that the excitation energy and leakage inductance energy of the current transformer CT are gradually released. At the same time, during the process of releasing the excitation energy and leakage inductance energy of the current transformer CT, the output end of the resistor-capacitor circuit 10 continues to discharge until the voltage at the output end drops from the positive voltage to 0V, and then the resistor-capacitor circuit 10 is reversely charged.

[0074] When the reverse voltage formed at the output end of the RC circuit 10 due to reverse charging reaches the first preset voltage V1, the discharge voltage stabilization circuit 20 is triggered to switch to the voltage stabilization mode, so that the reverse voltage at the output end of the RC circuit 10 is maintained at the first preset voltage V1 until the turn-on time point of the next PWM cycle arrives, so that the output voltage of the RC circuit 10 returns to a monotonic single-value step-down signal with a constant negative value within at most half a PWM cycle, and returns to the return state of constant negative voltage. During this period, the inverter 200 has no energy transmission.

[0075] When the next PWM cycle starts, the current conditioning circuit 100 repeats the entire operation process, thereby generating a noise-free triangular wave voltage signal that is proportional to the primary current of the current transformer CT and has the same frequency as the primary current of the current transformer CT.

[0076] The triangular wave voltage signal can indirectly detect the primary current of the inverter 200 and can be used as a sampling signal to further realize reliable control of the inverter 200, prevent false triggering and false protection, and ensure the safety and normal operation of the inverter.

[0077] Among them, the rising curve of the voltage at the output end of the resistor-capacitor circuit 10 rises at a preset slope, and the falling curve falls at another preset slope. The slopes of each time period and each point of the rising curve may be equal or different, and the slopes of each time period and each point of the falling curve may be equal or different. The rising curve and the falling curve are approximately linear, and the specific size is determined according to the different structures of the resistor-capacitor circuit 10 and the discharge voltage stabilizing circuit 20, and is not specifically limited here.

[0078] The RC circuit 10 may adopt a RC coupling circuit of corresponding structure, and the discharge voltage stabilizing circuit 20 may adopt a corresponding switch, diode, resistor and other structures, and the specific structure is not limited.

[0079] Furthermore, in order to ensure reliable output of the triangular wave voltage signal, optionally, T1+T2+T3≤T0;

[0080] T0 is the duration of a single PWM cycle, T1 is the forward charging duration of the RC circuit 10 in a single PWM cycle, T2 is the discharge duration of the RC circuit 10 in a single PWM cycle, and T3 is the reverse charging duration of the RC circuit 10 in a single PWM cycle.

[0081] By setting the corresponding parameters of the RC circuit 10 and the discharge voltage stabilizing circuit 20, the sum of the voltage rise time, the voltage discharge time and the reverse charging time is less than or equal to the PWM period, thereby ensuring that the output voltage of the RC circuit 10 drops to the first preset voltage V1 within each period, thereby achieving periodic change.

[0082] like Figure 5 As shown, optionally, the RC circuit 10 includes a capacitor C1 and a first resistor R1;

[0083] A first end of the capacitor C1 is connected to a first end S3 of the secondary winding of the current transformer CT, a second end of the capacitor C1 is connected to a first end of the first resistor R1, and a second end of the first resistor R1 is connected to a second end S4 of the secondary winding of the current transformer CT.

[0084] The discharge voltage stabilizing circuit 20 includes a Zener diode D1 and a second resistor R2;

[0085] The cathode of the Zener diode D1 is connected to the first end of the capacitor C1 , the anode of the Zener diode D1 is connected to the first end of the second resistor R2 , and the second end of the second resistor R2 is connected to the second end of the capacitor C1 .

[0086] In this embodiment, reference Figure 2 and Figure 3When the PWM cycle of the inverter 200 switches to the on time point, the inverter 200 is in the on state. At this time, when the first end S3 of the secondary winding of the current transformer CT is positive and the second end S4 is negative, the voltage across the capacitor C1 is the first preset voltage V1, that is, point P0, and the capacitor C1 begins to charge forward through the first resistor R1. The charging time constant is τ1=R1C1, which is determined by the resistance value of the first resistor R1 and the capacitance value of the capacitor C1. The voltage across the capacitor C1 gradually rises from the negative first preset voltage V1 to 0V, and then continues to gradually rise at a preset slope, and rises to the second preset voltage V2 at the first time point, that is, Figure 2 At point P1, a monotonic, single-valued boost signal V1-V2 is formed, which realizes the storage of noise and the current signal obtained by conversion sampling at both ends of capacitor C1, and synthesizes the secondary voltage noise with low energy of different timing and the main current signal with high energy that reflects the switching timing of inverter 200 into a single monotonic, single-valued boost signal in which the main current signal plays a dominant role in timing and intensity. The monotonic, single-valued boost signal can reflect the magnitude of the primary current of the current transformer CT, thereby submerging the low-energy noise in the high-energy current signal without causing interference, and eliminates the difference in timing between the two signals through the charging time effect. The current signal is effectively and proportionally converted into a ramp voltage signal at both ends of capacitor C1 that can be used as the output voltage. The ramp voltage signal has a simple, single-valued, monotonic, and approximately linear rise.

[0087] At the same time, when the voltage across the capacitor C1 reaches the second preset voltage V2, the Zener diode D1 receives the forward voltage of the RC circuit 10 and is reversely broken down and turned on. The charge stored in the capacitor C1 begins to discharge through the Zener diode D1 and the second resistor R2. The discharge time constant is τ2=R2C1, where R2 represents the resistance value of the second resistor R2. At the same time, the discharge current flowing through the Zener diode D1 and the second resistor R2 includes the discharge current of the capacitor C1 and the forward current applied by the secondary side of the current transformer CT. As the discharge progresses, the voltage across the capacitor C1 gradually decreases until the closing time point of the PWM cycle.

[0088] Due to the requirement for resetting the magnetic flux of the current transformer CT within a switching cycle, during the off time of the PWM cycle, the first end S3 of the secondary winding of the current transformer CT becomes negative and the second end S4 becomes positive, so that the excitation energy and leakage inductance energy of the current transformer CT are gradually released. At the same time, during the process of releasing the excitation energy and leakage inductance energy of the current transformer CT, the two ends of the capacitor C1 continue to discharge until the voltage at the output end drops from the positive voltage to 0V, and the capacitor C1 is reversely charged.

[0089] When the reverse voltage formed across the capacitor C1 due to reverse charging reaches the first preset voltage V1, the Zener diode D1 is forward-biased and switches to the voltage regulation mode. The reverse voltage across the capacitor C1 is maintained at the first preset voltage V1 through the second resistor R2 until the turn-on time point of the next PWM cycle arrives, so that the output voltage of the capacitor C1 returns to a monotonic single-valued step-down signal with a constant negative value within at most half a PWM cycle, and returns to the return state of the constant negative voltage. During this period, the inverter 200 does not transmit energy.

[0090] When the next PWM cycle starts, the current conditioning circuit 100 repeats the entire operation process, thereby forming a noise-free triangular wave voltage signal that is proportional to the primary current of the current transformer CT and has the same frequency and phase as the primary current.

[0091] The triangular wave voltage signal can indirectly detect the primary current of the inverter 200 and further realize reliable control of the inverter 200, thereby preventing false triggering and false protection, achieving strong anti-interference against EMI interference, and having a high signal-to-noise ratio.

[0092] Among them, by selecting and combining the parameters of the first resistor R1, the second resistor R2, the capacitor C1 and the Zener diode D1, the primary current detection of the current transformer CT of the inverter 200 with various capacities and switching frequencies is realized, meeting the current-voltage conversion requirements of the current signal detection of energy converters with different power levels and different switching frequencies.

[0093] Meanwhile, the current conditioning circuit 100 has a simple structure, low cost, and is easy to debug, and can be reused for different current transformers CT.

[0094] Meanwhile, the first resistor R1 and the second resistor R2 can be formed by one resistor or multiple resistors connected in series and parallel, and the specific structure is not limited.

[0095] Based on the periodic sampling output requirement of the triangular wave voltage signal, optionally, the resistance of the second resistor R2 is smaller than the resistance of the first resistor R1, so that the terminal voltage of the capacitor C1 decreases faster than the increase speed, and the decrease time is shorter than the increase time, thereby reserving the reverse charging time and ensuring that the terminal voltage of the capacitor C1 reliably drops to the first preset voltage V1.

[0096] In another embodiment, Figure 6 As shown, the RC circuit 10 includes a capacitor C1 and a first resistor R1;

[0097] A first end of the first resistor R1 is connected to a first end S3 of the secondary winding of the current transformer CT, a second end of the first resistor R1 is connected to a first end of the capacitor C1, and a second end of the capacitor C1 is connected to a second end S4 of the secondary winding of the current transformer CT.

[0098] The discharge voltage stabilizing circuit 20 includes a Zener diode D1 and a second resistor R2;

[0099] The cathode of the Zener diode D1 is connected to the first end of the capacitor C1 , the anode of the Zener diode D1 is connected to the first end of the second resistor R2 , and the second end of the second resistor R2 is connected to the second end of the capacitor C1 .

[0100] Compared with the circuit structure of the previous embodiment, the RC circuit 10 has a different arrangement position of the first resistor R1 , but the working principle is the same, so it will not be described in detail.

[0101] like Figure 7 and Figure 8 As shown, in another embodiment, based on the voltage sampling requirements of the inverter circuit or another sampling circuit, the current conditioning circuit 100 further includes:

[0102] The potential boosting circuit 30 is connected to the signal output end of the current conditioning circuit 100. The potential boosting circuit 30 is configured to positively boost the voltage signal output by the current conditioning circuit 100 to a preset voltage threshold and output it. The preset voltage threshold range is V3~V4, where V4 is greater than V3, and V3≥0V.

[0103] In this embodiment, the potential boosting circuit 30 boosts the overall voltage of the triangular wave voltage signal, so that the triangular wave voltage signal output to the back-end module is a positive voltage, meeting the voltage sampling requirements of the back-end module.

[0104] The potential boosting circuit 30 may be a pull-up resistor, a voltage source, a bias circuit, or the like, and the specific structure is not limited.

[0105] Furthermore, if Figure 9 and Figure 10 As shown, the current conditioning circuit 100 further includes:

[0106] The scaling circuit 40 connected to the signal output terminal of the current conditioning circuit 100 is configured to scale and output the voltage signal output by the current conditioning circuit 100 .

[0107] In this embodiment, in order to meet the voltage level requirements of different sampling of the back-end module, the current conditioning circuit 100 is also provided with a proportional scaling circuit 40 to achieve proportional scaling of the triangular wave voltage signal, amplifying or reducing it to the back-end module to meet the sampling requirements, wherein the proportional scaling circuit 40 includes a proportional reduction circuit and / or a proportional amplification circuit, and can respectively adopt corresponding amplification circuits, step-down circuits, etc., such as transistor amplification circuits, voltage divider circuits and other structures, and the specific structure is not limited.

[0108] The present invention also provides a power conversion circuit, such as Figure 1 As shown, the power conversion circuit includes an inverter 200, a current transformer CT, and a current conditioning circuit 100. The specific structure of the current conditioning circuit is similar to the above-mentioned embodiments. Since this power conversion circuit adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above-mentioned embodiments, and will not be described in detail here. The inverter 200, the current transformer CT, and the current conditioning circuit 100 are connected in sequence.

[0109] In this embodiment, the inverter 200 is configured to invert the input DC power into AC power. At the same time, the current transformer CT realizes current mutual induction output. The secondary winding of the current transformer CT is connected to the current conditioning circuit 100 to realize indirect sampling of the primary current of the current transformer CT. The current conditioning circuit 100 realizes the conversion of the current signal into a voltage signal and forms a noise-free triangular wave voltage signal that is proportional to the magnitude of the primary current of the current transformer CT and has the same frequency as the primary current of the current transformer CT. The triangular wave voltage signal realizes indirect detection of the primary current of the inverter 200 and further realizes reliable control of the inverter 200 to prevent false triggering and false protection of the inverter 200.

[0110] At the same time, according to different power inputs, the power conversion circuit may also include a rectifier circuit, a filter circuit, etc. to realize the rectification and filtering of the AC power supply, and then form the rectification filtering, inversion conversion, mutual inductance output and current conditioning of the entire power conversion, sampling and inversion control work with the inverter 200, the current transformer CT and the current conditioning circuit 100.

[0111] The present invention also proposes an electrical device, which includes a power conversion circuit. The specific structure of the power conversion circuit refers to the above-mentioned embodiment. Since this electrical device adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0112] The electrical equipment converts the output corresponding working power to the corresponding power-consuming module of the electrical equipment through the internal power conversion circuit, thereby realizing the power supply work of the power-consuming module. Among them, the electrical equipment can be an inverter welding machine, a cutting machine, a UPS device, an inverter 200, etc., and the specific application field is not limited.

[0113] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A current conditioning method, applied to a current conditioning circuit, wherein the current conditioning circuit is connected to an inverter via a current transformer, characterized in that: The current conditioning method comprises: In the initial state, the current conditioning circuit is triggered to maintain a voltage stabilization mode, wherein the voltage stabilization mode is: the current conditioning circuit is triggered to shut down its own discharge channel and stabilize the output voltage to a first preset voltage, wherein the first preset voltage is less than 0V; At an on-time point in each PWM cycle of the inverter, the current conditioning circuit is triggered to switch to a forward charging mode, wherein the forward charging mode is to obtain a voltage noise signal and a switching current signal of the inverter through the current transformer and perform charging, energy storage, and boost output; When the output voltage rises to a second preset voltage after charging, the current conditioning circuit is triggered to switch to a discharge mode. The discharge mode is as follows: the discharge channel is triggered to conduct to perform a discharge operation, and the current is discharged to 0V after the off time point in each PWM cycle of the inverter, and the current is switched to reverse charging and step-down output. After the output voltage is triggered to be stepped down to the first preset voltage before the start time point of the next PWM cycle, the current conditioning circuit is triggered to switch to the voltage regulation mode.

2. The current conditioning method according to claim 1, wherein: T1+T2+T3≤T0; Among them, T0 is the duration of a single PWM cycle, T1 is the forward charging duration in a single PWM cycle, T2 is the discharge duration in a single PWM cycle, and T3 is the reverse charging duration in a single PWM cycle.

3. A current conditioning circuit, applied to a current transformer, wherein an inverter, the current transformer and the current conditioning circuit are connected in sequence, characterized in that: The current conditioning circuit includes a resistor-capacitor circuit and a discharge voltage stabilizing circuit connected in sequence; The input end of the RC circuit is connected to the secondary winding of the current transformer, and the discharge voltage stabilizing circuit is connected in parallel to the output end of the RC circuit. In an initial state, the discharge channel of the RC circuit is triggered to be shut off, and the output end of the RC circuit is stabilized to a first preset voltage, which is less than 0V. The RC circuit is configured to acquire the voltage noise signal and the switching current signal of the inverter through the current transformer at the start time point within each PWM cycle of the inverter to perform forward charging, energy storage and boost output; The discharge voltage stabilizing circuit is configured to be triggered to conduct when the forward output voltage of the RC circuit rises to a second preset voltage, so as to provide a discharge channel; The RC circuit is further configured to discharge through the discharge voltage stabilizing circuit after the output voltage rises to a second preset voltage, and to start reverse charging at a turn-off time point in each PWM cycle of the inverter, and to discharge to 0V after the turn-off time point in each PWM cycle of the inverter, and to switch to reverse charging and step-down output; The discharge voltage stabilization circuit is further configured to trigger voltage stabilization when the output voltage of the resistor-capacitor circuit drops to the first preset voltage, and stabilize the output voltage of the resistor-capacitor circuit to the first preset voltage.

4. The current conditioning circuit according to claim 3, wherein: The RC circuit includes a capacitor and a first resistor; The first end of the capacitor is connected to the first end of the secondary winding of the current transformer, the second end of the capacitor is connected to the first end of the first resistor, and the second end of the first resistor is connected to the second end of the secondary winding of the current transformer; Or the first end of the first resistor is connected to the first end of the secondary winding of the current transformer, the second end of the first resistor is connected to the first end of the capacitor, and the second end of the capacitor is connected to the second end of the secondary winding of the current transformer.

5. The current conditioning circuit according to claim 4, wherein: The discharge voltage stabilizing circuit includes a Zener diode and a second resistor; The cathode of the Zener diode is connected to the first end of the capacitor, the anode of the Zener diode is connected to the first end of the second resistor, and the second end of the second resistor is connected to the second end of the capacitor.

6. The current conditioning circuit according to claim 5, wherein: The resistance of the second resistor is less than or equal to the resistance of the first resistor.

7. The current conditioning circuit according to claim 3, wherein: The current conditioning circuit further includes: A potential boosting circuit connected to the signal output end of the current conditioning circuit, wherein the potential boosting circuit is configured to positively boost the voltage signal output by the current conditioning circuit to a preset voltage threshold and output it, wherein the preset voltage threshold range is V3 to V4, wherein V4 is greater than V3, and V3 ≥ 0V.

8. The current conditioning circuit according to claim 3, wherein: The current conditioning circuit further includes: The scaling circuit connected to the signal output terminal of the current conditioning circuit is configured to scale and output the voltage signal output by the current conditioning circuit.

9. A power conversion circuit, characterized in that: The invention comprises an inverter, a current transformer and a current conditioning circuit according to any one of claims 3 to 8, wherein the inverter, the current transformer and the current conditioning circuit are connected in sequence.

10. An electrical device, characterized in that: Comprising the power conversion circuit as claimed in claim 9.

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