Electrolytic capacitor pre-charging circuit and control method

Abstract

The invention provides an electrolytic capacitor pre-charging circuit and a control method thereof, and the circuit comprises a power circuit and a control structure circuit. The power circuit comprises a power MOSFET S1, a power diode D1, a current-limiting inductor L1, an electrolytic capacitor C1 and a direct-current voltage source PS1, a source electrode of the power MOSFET S1 is connected with a negative electrode of the direct-current voltage source PS1 and a ground 1, and a drain electrode of the power MOSFET S1 is connected with an anode of the power diode D1, an output negative electrode of the electrolytic capacitor C1 and a ground 2; the cathode of the power diode D1 is connected with the anode of the DC voltage source PS1 and one end of the current-limiting inductor L1, and the other end of the current-limiting inductor L1 is connected with the output anode of the electrolytic capacitor C1. According to the invention, the low-current constant-current charging of the electrolytic capacitor C1 is realized, the power-on process is controllable, the power-on time limit is balanced, and the current limit is broken through.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power electronic converters, and in particular, to an electrolytic capacitor pre-charging circuit and a control method therefor. Background Art

[0002] When using a DC voltage source to pre-charge a large-capacity electrolytic capacitor, or using an AC power source to pre-charge a large-capacity electrolytic capacitor through a rectifier bridge, soft-on power technology needs to be adopted. If a high inrush current occurs, the following potential hazards will be caused: (1) The air switch or fuse operates; (2) The grid voltage drops short-term; (3) The voltage of the electrolytic capacitor rises, and the voltage change rate dv / dt of the electrolytic capacitor is too high, damaging the additional DC-DC or DC-AC converter at the rear stage; (4) The equivalent series resistance (ESR) of the electrolytic capacitor, power devices, and line losses are too large.

[0003] After retrieval, it is found that: A very large number of patented technologies involve the soft-on power technology of electrolytic capacitors, such as CN201510974289.1, CN201510974290.4, CN201210087154.X, CN201310493131.3. The only problem solved by these patented technologies is how to achieve soft pre-charging of electrolytic capacitors, that is, soft-on power. The common problems they have: (1) Belong to passive solutions, and the controllability of the power-on process is poor; (2) The problem of total loss or loss of electrolytic capacitors during the soft-on power process is not considered.

[0004] Therefore, it is highly necessary to design a pre-charging circuit and a control method for a large-capacity electrolytic capacitor with the control objectives of low electrolytic capacitor loss and total loss, good controllability, and capable of considering the power-on time limit. Summary of the Invention

[0005] Aiming at the defects in the prior art, the object of the present disclosure is to provide an electrolytic capacitor pre-charging circuit and a control method therefor.

[0006] To achieve the above object, according to one aspect of the present disclosure, there is provided an electrolytic capacitor pre-charging circuit, including: a power circuit and a control structure circuit, the power circuit and the control structure circuit are connected;

[0007] The power circuit includes a power MOSFET S1, a power diode D1, a current-limiting inductor L1, an electrolytic capacitor C1, and a DC voltage source PS1. The source of the power MOSFET S1 is connected to the negative electrode of the DC voltage source PS1 and ground 1 respectively. The drain of the power MOSFET S1 is connected to the anode of the power diode D1, the negative output terminal of the electrolytic capacitor C1, and ground 2 respectively. The cathode of the power diode D1 is connected to the positive electrode of the DC voltage source PS1 and one end of the current-limiting inductor L1 respectively. The other end of the current-limiting inductor L1 is connected to the positive output terminal of the electrolytic capacitor C1. The power circuit is used to pre-charge the electrolytic capacitor C1, and the control structure circuit is used to adjust the charging current for charging the electrolytic capacitor C1 by the power circuit to be constant.

[0008] Optionally, the control structure circuit includes a hysteresis comparator CMP1, a hysteresis comparator CMP2, an OR gate ORG1, and a driver DRV1. The negative input terminal of the hysteresis comparator CMP1 is connected to the negative DC output terminal of the power circuit. The output terminal of the hysteresis comparator CMP1 is connected to the input terminal 1 of the OR gate ORG1. The positive input terminal of the hysteresis comparator CMP2 is connected to the power circuit. The output terminal of the hysteresis comparator CMP2 is connected to the input terminal 2 of the OR gate ORG1. The output terminal of the OR gate ORG1 is connected to the input terminal of the isolated driver DRV1. The output terminal of the driver DRV1 is connected to the gate of the power MOSFET S1.

[0009] Optionally, the negative input terminal of the hysteresis comparator CMP1 is used to input the current of the current-limiting inductor L1. The positive input terminal of the hysteresis comparator CMP1 is used to input a preset current limit value. The negative input terminal of the hysteresis comparator CMP2 is used to input the input voltage ui of the DC voltage source PS1 in the power circuit. The positive input terminal of the hysteresis comparator CMP2 is used to input the output voltage uo of the electrolytic capacitor C1 in the power circuit.

[0010] According to a second aspect of the present disclosure, a control method for an electrolytic capacitor pre-charging circuit is provided, including:

[0011] Obtain the input voltage of the DC voltage source PS1;

[0012] Determine the input voltage state of the DC voltage source PS1 according to a preset input voltage threshold and the input voltage of the DC voltage source PS1;

[0013] If the input voltage state of the DC voltage source PS1 is normal, obtain the output voltage of the electrolytic capacitor C1;

[0014] Determine the output voltage state of the electrolytic capacitor C1 according to the preset output voltage threshold and the output voltage of the electrolytic capacitor C1;

[0015] If the output voltage state of the electrolytic capacitor C1 is normal, determine the voltage difference according to the input voltage of the DC voltage source PS1 and the output voltage of the electrolytic capacitor C1;

[0016] Determine the voltage signal according to the preset voltage difference threshold and the voltage difference;

[0017] Obtain the inductor current of the current-limiting inductor L1;

[0018] Determine the inductor current state of the current-limiting inductor L1 according to the preset current threshold and the inductor current of the current-limiting inductor L1;

[0019] If the inductor current state of the current-limiting inductor L1 is normal, determine the current difference according to the preset current and the inductor current of the current-limiting inductor L1;

[0020] Determine the current signal according to the preset current difference threshold and the current difference;

[0021] Perform an OR operation on the voltage signal and the current signal to determine the drive signal of the power MOSFET S1 in the power circuit.

[0022] Optionally, the determining the input voltage state of the DC voltage source PS1 according to the preset input voltage threshold and the input voltage of the DC voltage source PS1 includes:

[0023] If the input voltage of the DC voltage source PS1 is greater than the preset input voltage threshold, the input voltage of the DC voltage source PS1 is overvoltage, and determine that the input voltage state of the DC voltage source PS1 is abnormal;

[0024] If the input voltage of the DC voltage source PS1 is less than the preset input voltage threshold, the input voltage of the DC voltage source PS1 is undervoltage, and determine that the input voltage state of the DC voltage source PS1 is abnormal;

[0025] If the input voltage of the DC voltage source PS1 is equal to the preset input voltage threshold, determine that the input voltage state of the DC voltage source PS1 is normal;

[0026] The determining the output voltage state of the electrolytic capacitor C1 according to the preset output voltage threshold and the output voltage of the electrolytic capacitor C1 includes:

[0027] If the output voltage of the electrolytic capacitor C1 is greater than the preset output voltage threshold, the output voltage of the electrolytic capacitor C1 is overvoltage, and determine that the output voltage state of the electrolytic capacitor C1 is abnormal;

[0028] If the output voltage of the electrolytic capacitor C1 is less than the preset output voltage threshold, the output voltage of the electrolytic capacitor C1 is overvoltage, and it is determined that the output voltage state of the electrolytic capacitor C1 is abnormal;

[0029] If the output voltage of the electrolytic capacitor C1 is equal to the preset output voltage threshold, the output voltage of the electrolytic capacitor C1 is overvoltage, and it is determined that the output voltage state of the electrolytic capacitor C1 is normal.

[0030] Optionally, the determining the voltage signal according to the preset pressure difference threshold and the pressure difference includes:

[0031] If the pressure difference is greater than the preset pressure difference threshold, it is determined that the voltage signal is a first voltage signal;

[0032] If the pressure difference is not greater than the preset pressure difference threshold, it is determined that the voltage signal is a second voltage signal.

[0033] Optionally, the determining the inductance current state of the current-limiting inductor L1 according to the preset current threshold and the inductance current of the current-limiting inductor L1 includes:

[0034] If the inductance current of the current-limiting inductor L1 is greater than or less than the preset current threshold, it is determined that the inductance current state of the current-limiting inductor L1 is abnormal;

[0035] If the inductance current of the current-limiting inductor L1 is equal to the preset current threshold, it is determined that the inductance current state of the current-limiting inductor L1 is normal.

[0036] Optionally, the determining the current signal according to the preset current difference threshold and the current difference includes:

[0037] If the current difference is greater than the preset current difference threshold, it is determined that the current signal is a first current signal;

[0038] If the current difference is less than the preset current difference threshold, it is determined that the current signal is a second current signal.

[0039] Optionally, the performing an OR operation on the voltage signal and the current signal to determine the drive signal of the power MOSFET S1 in the power circuit includes:

[0040] Performing an OR operation on the voltage signal and the current signal to determine the OR operation result;

[0041] If the OR operation result is a high level, it is determined that the drive signal of the power MOSFET S1 in the power circuit is a conduction signal;

[0042] If the result of the OR operation is low level, determine that the drive signal of the power MOSFET S1 in the power circuit is an off signal.

[0043] Optionally, the method further includes:

[0044] If the input voltage state of the DC voltage source PS1 is abnormal, send an input voltage abnormal alarm signal and return to the step of obtaining the input voltage of the DC voltage source PS1;

[0045] If the output voltage of the electrolytic capacitor C1 is abnormal, send an output voltage abnormal alarm signal and return to the step of obtaining the input voltage of the DC voltage source PS1;

[0046] If the inductor current state of the current-limiting inductor L1 is abnormal, send an inductor current abnormal alarm signal and return to the step of obtaining the input voltage of the DC voltage source PS1;

[0047] After determining the drive signal, return to the step of obtaining the input voltage of the DC voltage source PS1.

[0048] Compared with the prior art, the embodiments of the present disclosure have at least one of the following beneficial effects:

[0049] Through the above technical solutions, by using the DC voltage source PS1, the power MOSFET S1, the power diode D1, and the current-limiting inductor L1, it is possible to keep the current of the current-limiting inductor L1 constant, perform constant-current charging on the electrolytic capacitor C1, and the voltage of the electrolytic capacitor C1 rises approximately linearly; by using a control structure circuit, the electrolytic capacitor C1 is controlled to charge with a lower current within a limited power-on time range, minimizing the equivalent series resistance loss of the electrolytic capacitor C1 and the total line loss, and realizing controllable power-on current. The circuit structure is simple and easy to implement.

[0050] In the embodiments of the present disclosure, the positive input terminal of the hysteresis comparator CMP1 in the control structure circuit is used to input a preset current limit value, so as to realize constant-current charging of the electrolytic capacitor C1 with a lower current by the power circuit and minimize the circuit loss.

[0051] In the embodiments of the present disclosure, after the soft power-on of the electrolytic capacitor C1 is completed, the power MOSFET S1 is in the on state for a long time, which is suitable for application scenarios with frequent power-on startups.

[0052] In the embodiments of the present disclosure, by detecting the input voltage state of the DC voltage source PS1, the output voltage state of the electrolytic capacitor C1, and the inductor current state of the current-limiting inductor, the controllability of the power-on process is realized, the charging current waveform is controllable, and the input voltage, current, output voltage, and current are protected. Description of the Drawings

[0053] Other features, objects, and advantages of the present disclosure will become more apparent from the following detailed description of non-limiting embodiments read in conjunction with the accompanying drawings:

[0054] Figure 1 is a schematic diagram of the overall structure of an electrolytic capacitor precharging circuit shown according to an exemplary embodiment.

[0055] Figure 2 is a schematic diagram of the overall structure of a power circuit shown according to an exemplary embodiment.

[0056] Figure 3 is a schematic diagram of the overall structure of a power circuit considering distributed parameters shown according to an exemplary embodiment.

[0057] Figure 4 is a flowchart showing a control method for an electrolytic capacitor precharging circuit shown according to an exemplary embodiment.

[0058] Figure 5 is a flowchart showing a control process for an electrolytic capacitor precharging circuit shown according to an exemplary embodiment. Detailed Embodiments

[0059] The present disclosure will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present disclosure, but do not limit the present disclosure in any way. It should be noted that those of ordinary skill in the art can make several modifications and improvements without departing from the concept of the present disclosure. These all fall within the protection scope of the present disclosure.

[0060] Figure 1 is a schematic diagram of the overall structure of an electrolytic capacitor precharging circuit shown according to an exemplary embodiment. Figure 2 is a schematic diagram of the overall structure of a power circuit shown according to an exemplary embodiment.

[0061] As Figure 1 shown, the present disclosure provides an electrolytic capacitor precharging circuit, including a power circuit and a control structure circuit, and the power circuit and the control structure circuit are connected.

[0062] As Figure 1 、 Figure 2As shown, the power circuit includes a power MOSFET S1, a power diode D1, a current-limiting inductor L1, an electrolytic capacitor C1, and a DC voltage source PS1. The source of the power MOSFET S1 is connected to the negative terminal of the DC voltage source PS1 and ground 1 respectively. The drain of the power MOSFET S1 is connected to the anode of the power diode D1, the output negative terminal of the electrolytic capacitor C1, and ground 2 respectively. The cathode of the power diode D1 is connected to the positive terminal of the DC voltage source PS1 and one end of the current-limiting inductor L1 respectively. The other end of the current-limiting inductor L1 is connected to the output positive terminal of the electrolytic capacitor C1. The power circuit is used to pre-charge the electrolytic capacitor C1, and the control structure circuit is used to regulate the charging current of the power circuit for charging the electrolytic capacitor C1 to be constant.

[0063] Through the above technical solution, by using the DC voltage source PS1, the power MOSFET S1, the power diode D1, and the current-limiting inductor L1, it is possible to make the current of the current-limiting inductor L1 constant and charge the electrolytic capacitor C1 with a constant current. The voltage of the electrolytic capacitor C1 rises approximately linearly. By using the control structure circuit, the electrolytic capacitor C1 is controlled to charge with a lower current within a limited power-on time range, minimizing the equivalent series resistance loss of the electrolytic capacitor C1 and the total line loss. Moreover, the power-on current can be controlled, and the circuit structure is simple and easy to implement.

[0064] In a possible embodiment, as Figure 1 shown, the control structure circuit includes a hysteresis comparator CMP1, a hysteresis comparator CMP2, an OR gate ORG1, and a driver DRV1.

[0065] The negative input terminal of the hysteresis comparator CMP1 is connected to the DC output negative terminal in the power circuit. The output terminal of the hysteresis comparator CMP1 is connected to the input terminal 1 of the OR gate ORG1. The output terminal of the hysteresis comparator CMP2 is connected to the input terminal 2 of the OR gate ORG1. The output terminal of the OR gate ORG1 is connected to the input terminal of the isolated driver DRV1. The output terminal of the driving driver DRV1 is connected to the gate of the power MOSFET S1.

[0066] The negative input terminal of the hysteresis comparator CMP1 is used to input the current of the current-limiting inductor L1. The positive input terminal of the hysteresis comparator CMP1 is used to input a preset current limit value. The negative input terminal of the hysteresis comparator CMP2 is used to input the input voltage ui of the DC voltage source PS1 in the power circuit. The positive input terminal of the hysteresis comparator CMP2 is used to input the output voltage uo of the electrolytic capacitor C1 in the power circuit.

[0067] In the present disclosure, the preset current limit value is (<1A).

[0068] The positive input terminal of the hysteresis comparator CMP1 in the control structure circuit is used to input a preset current limit value, so as to realize that the power circuit charges the electrolytic capacitor C1 with a relatively low current in a constant current manner, minimizing circuit losses.

[0069] In the present disclosure, after the soft start-up of the electrolytic capacitor C1 is completed, the power MOSFET S1 is in the on state for a long time. An electrolytic capacitor pre-charging circuit provided by the present disclosure is suitable for application scenarios with frequent start-up and power-on.

[0070] Figure 3 It is a schematic diagram of the overall structure of a power circuit considering distributed parameters shown according to an exemplary embodiment.

[0071] As Figure 3 shown, when considering distributed parameters, r dis represents the lumped line distribution resistance, r ES represents the equivalent series resistance ESR of the electrolytic capacitor C1, r dson represents the on-resistance of the power MOSFET S1, r DC represents the DC resistance of the current-limiting inductor L1, u DF represents the on-voltage drop of the power diode D1.

[0072] One end of the lumped line distribution resistance r dis is connected to the positive pole of the DC voltage source PS1, and the other end is respectively connected to the cathode of the power diode D1 and one end of the current-limiting inductor L1; one end of the equivalent series resistance ESR r ES of the electrolytic capacitor C1 is connected to the output negative pole of the electrolytic capacitor C1, and the other end is grounded 2; one end of the on-resistance r dson of the power MOSFET S1 is connected to the drain of the power MOSFET S1, and the other end is connected to the anode of the power diode D1; one end of the DC resistance r DC of the current-limiting inductor L1 is connected to the other end of the current-limiting inductor L1, and the other end is connected to the output positive pole of the electrolytic capacitor C1.

[0073] Based on the power circuit considering distributed parameters of an electrolytic capacitor pre-charging circuit provided by the present disclosure, the equivalent series resistance loss of the electrolytic capacitor C1 and the total line loss can be minimized, and the power-on current can be controlled, and the circuit structure is simple and easy to implement.

[0074] Figure 4 It is a schematic flowchart of a control method for an electrolytic capacitor pre-charging circuit shown according to an exemplary embodiment.

[0075] As Figure 4 shown, the present disclosure also provides a control method for an electrolytic capacitor pre-charging circuit, including S11 to S21.

[0076] S11. Obtain the input voltage of the DC voltage source PS1.

[0077] Among them, the input voltage of the DC voltage source PS1 is represented as u i .

[0078] S12. Determine the input voltage state of the DC voltage source PS1 according to the preset input voltage threshold and the input voltage of the DC voltage source PS1.

[0079] Among them, the input voltage state of the DC voltage source PS1 includes normal and abnormal, and the abnormal state includes undervoltage and overvoltage.

[0080] S13. If the input voltage state of the DC voltage source PS1 is normal, obtain the output voltage of the electrolytic capacitor C1.

[0081] Among them, the output voltage of the electrolytic capacitor C1 is represented as u o .

[0082] S14. Determine the output voltage state of the electrolytic capacitor C1 according to the preset output voltage threshold and the output voltage of the electrolytic capacitor C1.

[0083] Among them, the output voltage state of the electrolytic capacitor C1 includes normal and abnormal, and the abnormal state includes undervoltage and overvoltage.

[0084] S15. If the output voltage state of the electrolytic capacitor C1 is normal, determine the pressure difference according to the input voltage of the DC voltage source PS1 and the output voltage of the electrolytic capacitor C1.

[0085] Among them, the pressure difference represents the difference between the input voltage of the DC voltage source PS1 and the output voltage of the electrolytic capacitor C1, that is, (u i - u o ).

[0086] S16. Determine the voltage signal according to the preset pressure difference threshold and the pressure difference.

[0087] Among them, the voltage signal includes the first voltage signal: voltage signal 1, and the second voltage signal: voltage signal 0.

[0088] S17. Obtain the inductor current of the current-limiting inductor L1.

[0089] Among them, the inductor current of the current-limiting inductor L1 is represented as i L1 .

[0090] S18. Determine the inductor current state of the current-limiting inductor L1 according to the preset current threshold and the inductor current of the current-limiting inductor L1.

[0091] Among them, the inductor current state includes normal and abnormal, and the abnormal state includes overcurrent and undercurrent.

[0092] S19. If the inductor current state of the current-limiting inductor L1 is normal, determine the current difference according to the preset current and the inductor current of the current-limiting inductor L1.

[0093] Among them, the preset current is represented as i L1,ref , and the inductor current of the current-limiting inductor L1 is represented as i L1 , i L1 also represents the actual inductor current of the current-limiting inductor L1.

[0094] The current difference is represented as the difference between the preset current and the inductor current of the current-limiting inductor L1 (i L1,ref - i L1 ).

[0095] S20. Determine the current signal according to the preset current difference threshold and the current difference.

[0096] Among them, the current signal includes the first current signal: current signal 1, and the second current signal: current signal 0.

[0097] S21. Perform an OR operation on the voltage signal and the current signal to determine the drive signal of the power MOSFET S1 in the power circuit.

[0098] By detecting the input voltage state of the DC voltage source PS1, the output voltage state of the electrolytic capacitor C1, and the inductor current state, the controllability of the power-on process is realized, the charging current waveform is controllable, and the input voltage, current, and output voltage and current are protected.

[0099] In a possible embodiment, S12. According to the preset input voltage threshold and the input voltage of the DC voltage source PS1, determining the input voltage state of the DC voltage source PS1 may include S121 to S123.

[0100] S121. If the input voltage of the DC voltage source PS1 is greater than the preset input voltage threshold, the input voltage of the DC voltage source PS1 is overvoltage, and it is determined that the input voltage state of the DC voltage source PS1 is abnormal.

[0101] S122. If the input voltage of the DC voltage source PS1 is less than the preset input voltage threshold, the input voltage of the DC voltage source PS1 is undervoltage, and it is determined that the input voltage state of the DC voltage source PS1 is abnormal.

[0102] S123. If the input voltage of the DC voltage source PS1 is equal to the preset input voltage threshold, it is determined that the input voltage state of the DC voltage source PS1 is normal.

[0103] In a possible embodiment, S14. Determining the output voltage state of the electrolytic capacitor C1 according to a preset output voltage threshold and the output voltage of the electrolytic capacitor C1 may include S141 to S143.

[0104] S141. If the output voltage of the electrolytic capacitor C1 is greater than the preset output voltage threshold, the output voltage of the electrolytic capacitor C1 is overvoltage, and it is determined that the output voltage state of the electrolytic capacitor C1 is abnormal.

[0105] S142. If the output voltage of the electrolytic capacitor C1 is less than the preset output voltage threshold, the output voltage of the electrolytic capacitor C1 is overvoltage, and it is determined that the output voltage state of the electrolytic capacitor C1 is abnormal.

[0106] S143. If the output voltage of the electrolytic capacitor C1 is equal to the preset output voltage threshold, the output voltage of the electrolytic capacitor C1 is overvoltage, and it is determined that the output voltage state of the electrolytic capacitor C1 is normal.

[0107] In a possible embodiment, S16. Determining a voltage signal according to a preset pressure difference threshold and the pressure difference may include S161 to S162.

[0108] S161. If the pressure difference is greater than the preset pressure difference threshold, it is determined that the voltage signal is a first voltage signal.

[0109] Wherein, the first voltage signal is represented as voltage signal 1.

[0110] S162. If the pressure difference is not greater than the preset pressure difference threshold, it is determined that the voltage signal is a second voltage signal.

[0111] Wherein, the second voltage signal is represented as voltage signal 0.

[0112] In a possible embodiment, S18. Determining the inductor current state of the current-limiting inductor L1 according to a preset current threshold and the inductor current of the current-limiting inductor L1 may include S181 to S182.

[0113] S181. If the inductor current of the current-limiting inductor L1 is greater than or less than the preset current threshold, it is determined that the inductor current state of the current-limiting inductor L1 is abnormal.

[0114] S182. If the inductor current of the current-limiting inductor L1 is equal to the preset current threshold, it is determined that the inductor current state of the current-limiting inductor L1 is normal.

[0115] In a possible embodiment, S20. Determining a current signal according to a preset current difference threshold and the current difference may include S201 to S202:

[0116] S201. If the current difference is greater than the preset current difference threshold, it is determined that the current signal is a first current signal.

[0117] Among them, the first current signal is represented as current signal 1.

[0118] S202: If the current difference is less than a preset current difference threshold, determine that the current signal is the second current signal.

[0119] The second current signal is represented as current signal 0.

[0120] In a possible embodiment, S21: Perform an OR operation on the voltage signal and the current signal to determine the drive signal of the power MOSFET S1 in the power circuit, including S211 to S213.

[0121] S211: Perform an OR operation on the voltage signal and the current signal to determine the OR operation result.

[0122] Among them, the OR operation result includes a high-level signal and a low-level signal.

[0123] S212: If the OR operation result is a high level, determine that the drive signal of the power MOSFET S1 in the power circuit is a conduction signal.

[0124] S213: If the OR operation result is a low level, determine that the drive signal of the power MOSFET S1 in the power circuit is a turn-off signal.

[0125] Based on the drive signal of the power MOSFET S1 in the power circuit determined by the above method, control the power MOSFET S1 in the power circuit to conduct or turn off.

[0126] In a possible embodiment, a control method for an electrolytic capacitor pre-charging circuit further includes S22.

[0127] S22: If the input voltage state of the DC voltage source PS1 is abnormal, send an input voltage abnormal alarm signal and return to the step of obtaining the input voltage of the DC voltage source PS1.

[0128] Step S22 is executed after step S12.

[0129] In a possible embodiment, a control method for an electrolytic capacitor pre-charging circuit further includes S23.

[0130] S23: If the output voltage of the electrolytic capacitor C1 is abnormal, send an output voltage abnormal alarm signal and return to the step of obtaining the input voltage of the DC voltage source PS1.

[0131] Step S23 is executed after step S14.

[0132] In a possible embodiment, a control method for an electrolytic capacitor pre-charging circuit further includes S24.

[0133] S24. If the inductor current state of the current-limiting inductor L1 is abnormal, send an abnormal current sensing alarm signal and return to the step of obtaining the input voltage of the DC voltage source PS1.

[0134] Step S24 is executed after step S18.

[0135] In a possible embodiment, a control method for an electrolytic capacitor pre-charging circuit further includes S25.

[0136] S25. After determining the drive signal, return to the step of obtaining the input voltage of the DC voltage source PS1.

[0137] Step S25 is executed after step S21.

[0138] Figure 5 It is a schematic flow chart of a control process of an electrolytic capacitor pre-charging circuit shown according to an exemplary embodiment.

[0139] As Figure 5 shown, the implementation process of a control method for an electrolytic capacitor pre-charging circuit of the present disclosure is as follows:

[0140] Entrance initialization, entrance:

[0141] V1 input voltage detection: Detect the input voltage u from the DC voltage source PS1 i ;

[0142] V2 Is the input voltage normal? Judge whether the input voltage u i is undervoltage and overvoltage. If it is normal, set it to Y; if it is abnormal, set it to N.

[0143] V3 Input voltage abnormal alarm: Set and send an input voltage abnormal alarm signal;

[0144] V4 Output voltage detection: Detect the output voltage u from the electrolytic capacitor C1 o ;

[0145] V5 Is the output voltage normal? Judge whether the output voltage u i is undervoltage and overvoltage. If it is normal, set it to Y; if it is abnormal, set it to N.

[0146] V6 Voltage abnormal alarm: Set and send an output voltage abnormal alarm signal;

[0147] V7 Pressure difference calculation: Calculate the difference between the output voltage u o and the input voltage u i ((u i -u o ));

[0148] V8 Is the pressure difference greater than the threshold? Judge whether the difference (u i -u oWhether it exceeds the preset pressure difference threshold. When it exceeds, set Y; when it does not exceed, set N. Set the size of the preset pressure difference threshold as needed.

[0149] V9 Voltage Signal 1: Set and send out Voltage Signal 1;

[0150] V10 Voltage Signal 0: Set and send out Voltage Signal 0;

[0151] I1 Inductive Current Detection: Detect the inductive current i from the current-limiting inductor L1 L1 ;

[0152] I2 Is Inductive Current Normal?: Judge whether the inductive current i L1 is overcurrent. When it is normal, set Y; when it is abnormal, set N;

[0153] I3 Inductive Current Abnormality Alarm: Set and send out the inductive current i L1 abnormality alarm signal;

[0154] I4 Current Difference Calculation: Calculate the set current i L1,ref and the actual inductive current i L1 of the current difference (i L1,ref -i L1 );

[0155] I5 Is Current Difference Greater Than Threshold?: Judge whether the current difference (i L1,ref -i L1 ) is greater than the preset current difference threshold. When it exceeds, set Y; when it does not exceed, set N. Set the size of the preset current difference threshold as needed;

[0156] I6 Current Signal 1: Set and send out Current Signal 1;

[0157] I7 Is Current Difference Less Than Threshold?: Judge whether the current difference (i L1,ref -i L1 ) is less than the preset current difference threshold. When it is less, set Y; when it is not less, set N;

[0158] I8 Current Signal 0: Set and send out Current Signal 0;

[0159] P1 Signal or Operation 1: Set and send out Voltage Signal 1;

[0160] P2 Generate Drive Signal 0: Set and send out Voltage Signal 0;

[0161] Return to the entrance.

[0162] Adopt the above-mentioned safe charging process and timing of V1--V9, I1--I8, P1--P2 to control the electrolytic capacitor pre-charging circuit to charge the electrolytic capacitor C1.

[0163] In existing soft power - on technologies or pre - charging technologies, during power - on, the inrush current is relatively large and the power - on time is uncontrollable, resulting in still relatively large total line losses and ESR losses of the electrolytic capacitor C1. For example, in the power - on scheme of the DC voltage source PS1 using a power resistor, it can be proved that the total loss of the power resistor is equal to the electric - field energy storage of the electrolytic capacitor C1. If the input voltage fluctuates, the total loss of the power resistor will increase. In the scheme of using a relay to cut off the power resistor, there will also be problems of relay contact - resistance loss and relay vibration and loosening. In the scheme of using a power switch to cut off the power resistor, there will be problems of power - switch conduction loss and the need for an additional drive circuit.

[0164] An electrolytic - capacitor pre - charging circuit and its control method provided by the present disclosure use a current - limiting inductor L1 for current - limiting during power - on and a power MOSFET S1 as a switch for current control. Compared with a power - on resistor of several tens of ohms, the introduced additional resistance is limited, and the loss of the free - wheeling power diode D1 is limited. Therefore, the additional total loss is relatively low.

[0165] Taking the soft power - on scheme with a power - resistor current - limiting as a comparison, the resistor energy consumption is equal to the capacitor energy storage The power - on time is relatively short, which is Δt1, where R Σ1 = R0 + r dis + r dES .

[0166] For the soft power - on scheme of the current - limiting inductor using the electrolytic - capacitor pre - charging circuit and its control method of the present disclosure, assuming that the operating mode of the current - limiting inductor L1 is the continuous - conduction mode CCM and the duty ratio is d, and the final capacitor energy storage remains unchanged, the resistor energy consumption where R Σ2 = r dis + r ES + r DC + d·r dson , the loss of the diode D1 is W D2 =(1 - d)·i L1 ·u DF , and the switching loss of the power MOSFET S1 is W LSW =Δt2·f s ·(E on + e off ).

[0167] For a certain CoolSiC MOSFET 650V G2, the turn - on loss for one time is 26 μJ, and the turn - off loss for one time is 13 μJ. For a certain CoolSiC MOSFET 650V G2, the turn - on loss for one time is 43 μJ, and the turn - off loss for one time is 33 μJ. E on and e offIt is related to semiconductor materials, device types, temperature rise, rated current, and manufacturing processes.

[0168] Therefore, during soft power-on, within Δt2, ensure that the current i of the current-limiting inductor L1 L1 is as flat as possible, with a small ripple component, and it is very easy to achieve W RΣ2 +W D2 +W LSW <W R0 , and achieve low-loss soft power-on.

[0169] Different devices have different soft power-on times, such as 0.1 s to several seconds.

[0170] In a possible embodiment, in a specific embodiment of using a pre-charging circuit and control method for electrolytic capacitors provided by the present disclosure to perform soft power-on for electrolytic capacitor C1, the parameters of each functional module or electronic component can be set as follows:

[0171] Input DC voltage of DC voltage source PS1: DC 400V;

[0172] Output DC voltage of electrolytic capacitor C1: DC 400V;

[0173] Switching frequency of power MOSFET S1: 20 kHz;

[0174] Power MOSFET S1: SiC power MOSFET 35A@85, 650V;

[0175] Power diode D1: 5A@85, 650V;

[0176] Electrolytic capacitor C1: 6800F, withstand voltage 400V;

[0177] Current-limiting inductor L1: 100F, 2A.

[0178] Hysteresis comparator CMP1: reference current at the positive input terminal <1A, hysteresis width 0.1A or others;

[0179] Hysteresis comparator CMP2: hysteresis width 1V or others;

[0180] OR gate ORG1: two-input OR gate;

[0181] Isolation driver DRV1: isolation type driver.

[0182] An electrolytic capacitor pre - charging circuit and its control method provided by the present disclosure appropriately extend the pre - charging time, based on a power circuit and a control structure circuit, and adopt the control method of the electrolytic capacitor pre - charging circuit to form a constant small current to charge the electrolytic capacitor C1. The voltage of the electrolytic capacitor C1 rises linearly, and the total loss during the entire charging process and the ESR loss of the electrolytic capacitor C1 are relatively low, having good controllability. After the pre - charging is completed, the current - limiting inductor L1 can be retained to play a stabilizing role, or a power switch can be used for short - circuiting.

[0183] An electrolytic capacitor pre - charging circuit and its control method provided by the present disclosure can also suppress or eliminate the inductor current zero - crossing crossover distortion, make the total current distortion tend to zero, obtain a near - unity power factor on the grid side, prevent harmonic current from polluting the power grid, and can be applied to the totem - pole PFC scenario, and can also be applied to the fields of commerce, household appliances, communication, charging piles, and wireless power transmission for vehicles. The circuit structure is simple and the operability is strong.

[0184] The specific embodiments of the present disclosure have been described above. It should be understood that the present disclosure is not limited to the above - mentioned specific implementation manners. Those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present disclosure. The above - mentioned preferred features can be combined arbitrarily without conflict.

Claims

1. An electrolytic capacitor pre-charging circuit, characterized in that: include: A power circuit and a control structure circuit, wherein the power circuit and the control structure circuit are connected; The power circuit includes a power MOSFET S1, a power diode D1, a current limiting inductor L1, an electrolytic capacitor C1 and a DC voltage source PS1. The source of the power MOSFET S1 is respectively connected to the negative electrode of the DC voltage source PS1 and ground 1, the drain of the power MOSFET S1 is respectively connected to the anode of the power diode D1, the output negative electrode of the electrolytic capacitor C1 and ground 2, the cathode of the power diode D1 is respectively connected to the positive electrode of the DC voltage source PS1 and one end of the current limiting inductor L1, the other end of the current limiting inductor L1 is connected to the output positive electrode of the electrolytic capacitor C1, the power circuit is used to pre-charge the electrolytic capacitor C1, and the control structure circuit is used to adjust the charging current of the power circuit to charge the electrolytic capacitor C1 to be constant.

2. The electrolytic capacitor pre-charging circuit according to claim 1, characterized in that: The control structure circuit includes a hysteresis comparator CMP1, a hysteresis comparator CMP2, an OR gate ORG1, and a driver DRV1. The negative input terminal of the hysteresis comparator CMP1 is connected to the negative electrode of the DC output in the power circuit, the output terminal of the hysteresis comparator CMP1 is connected to the input terminal 1 of the OR gate ORG1, the output terminal of the hysteresis comparator CMP2 is connected to the input terminal 2 of the OR gate ORG1, the output terminal of the OR gate ORG1 is connected to the input terminal of the isolated driver DRV1, and the output terminal of the driver DRV1 is connected to the gate of the power MOSFET S1.

3. The electrolytic capacitor pre-charging circuit according to claim 2, characterized in that: The negative input terminal of the hysteresis comparator CMP1 is used to input the current of the current limiting inductor L1, the positive input terminal of the hysteresis comparator CMP1 is used to input a preset current limit, the negative input terminal of the hysteresis comparator CMP2 is used to input the input voltage ui of the DC voltage source PS1 in the power circuit, and the positive input terminal of the hysteresis comparator CMP2 is used to input the output voltage uo of the electrolytic capacitor C1 in the power circuit.

4. A control method for an electrolytic capacitor pre-charging circuit, characterized in that: include: Obtain the input voltage of the DC voltage source PS1; Determining an input voltage state of the DC voltage source PS1 according to a preset input voltage threshold and an input voltage of the DC voltage source PS1; If the input voltage state of the DC voltage source PS1 is normal, the output voltage of the electrolytic capacitor C1 is obtained; Determining the output voltage state of the electrolytic capacitor C1 according to a preset output voltage threshold and the output voltage of the electrolytic capacitor C1; If the output voltage state of the electrolytic capacitor C1 is normal, the voltage difference is determined according to the input voltage of the DC voltage source PS1 and the output voltage of the electrolytic capacitor C1; Determining a voltage signal according to a preset voltage difference threshold and the voltage difference; Obtain the inductor current of the current limiting inductor L1; Determining the inductor current state of the current limiting inductor L1 according to a preset current threshold and the inductor current of the current limiting inductor L1; If the inductor current state of the current limiting inductor L1 is normal, determine the current difference according to the preset current and the inductor current of the current limiting inductor L1; Determining a current signal according to a preset current difference threshold and the current difference; An OR operation is performed on the voltage signal and the current signal to determine a driving signal of a power MOSFET S1 in a power circuit.

5. The method according to claim 4, characterized in that The step of determining the input voltage state of the DC voltage source PS1 according to a preset input voltage threshold and the input voltage of the DC voltage source PS1 includes: If the input voltage of the DC voltage source PS1 is greater than the preset input voltage threshold, the input voltage of the DC voltage source PS1 is overvoltage, and it is determined that the input voltage state of the DC voltage source PS1 is abnormal; If the input voltage of the DC voltage source PS1 is less than the preset input voltage threshold, the input voltage of the DC voltage source PS1 is undervoltage, and it is determined that the input voltage state of the DC voltage source PS1 is abnormal; If the input voltage of the DC voltage source PS1 is equal to the preset input voltage threshold, it is determined that the input voltage state of the DC voltage source PS1 is normal; The step of determining the output voltage state of the electrolytic capacitor C1 according to a preset output voltage threshold and the output voltage of the electrolytic capacitor C1 includes: If the output voltage of the electrolytic capacitor C1 is greater than the preset output voltage threshold, the output voltage of the electrolytic capacitor C1 is overvoltage, and it is determined that the output voltage state of the electrolytic capacitor C1 is abnormal; If the output voltage of the electrolytic capacitor C1 is less than the preset output voltage threshold, the output voltage of the electrolytic capacitor C1 is overvoltage, and it is determined that the output voltage state of the electrolytic capacitor C1 is abnormal; If the output voltage of the electrolytic capacitor C1 is equal to the preset output voltage threshold, it is determined that the output voltage state of the electrolytic capacitor C1 is normal.

6. The method according to claim 4, characterized in that The step of determining the voltage signal according to the preset voltage difference threshold and the voltage difference comprises: If the voltage difference is greater than the preset voltage difference threshold, determining that the voltage signal is a first voltage signal; If the voltage difference is not greater than the preset voltage difference threshold, it is determined that the voltage signal is a second voltage signal.

7. The method according to claim 4, characterized in that The determining the inductor current state of the current limiting inductor L1 according to the preset current threshold and the inductor current of the current limiting inductor L1 includes: If the inductor current of the current limiting inductor L1 is greater than or less than the preset current threshold, it is determined that the inductor current state of the current limiting inductor L1 is abnormal; If the inductor current of the current-limiting inductor L1 is equal to the preset current threshold, it is determined that the inductor current state of the current-limiting inductor L1 is normal.

8. The method according to claim 4, characterized in that The step of determining the current signal according to a preset current difference threshold and the current difference value comprises: If the current difference is greater than the preset current difference threshold, determining that the current signal is a first current signal; If the current difference is less than the preset current difference threshold, it is determined that the current signal is a second current signal.

9. The method according to claim 4, characterized in that The step of performing an OR operation on the voltage signal and the current signal to determine a driving signal of a power MOSFET S1 in a power circuit includes: Performing an OR operation on the voltage signal and the current signal to determine an OR operation result; If the result of the OR operation is a high level, determining that the driving signal of the power MOSFET S1 in the power circuit is a conduction signal; If the result of the OR operation is a low level, it is determined that the driving signal of the power MOSFET S1 in the power circuit is a turn-off signal.

10. The method according to claim 4, characterized in that The method further comprises: If the input voltage state of the DC voltage source PS1 is abnormal, an input voltage abnormality alarm signal is issued, and the process returns to the step of obtaining the input voltage of the DC voltage source PS1; If the output voltage of the electrolytic capacitor C1 is abnormal, an abnormal output voltage alarm signal is issued, and the process returns to the step of obtaining the input voltage of the DC voltage source PS1; If the inductor current state of the current-limiting inductor L1 is abnormal, an abnormal inductor current alarm signal is issued, and the process returns to the step of obtaining the input voltage of the DC voltage source PS1; After determining the driving signal, the process returns to the step of obtaining the input voltage of the DC voltage source PS1.

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