AC / DC conversion circuit and charging device

Abstract

The utility model discloses an AC-DC conversion circuit and a charging device, the AC-DC conversion circuit comprises a power factor correction circuit, a DC / DC conversion circuit and an auxiliary power supply circuit, the auxiliary power supply circuit comprises an auxiliary source power supply circuit, a flyback converter, a controllable switch and a control module, and the auxiliary source power supply circuit is connected in parallel between the positive output end and the negative output end of the power factor correction circuit; the flyback converter is connected in parallel with the auxiliary source power supply circuit, and the primary side midpoint is connected with the midpoint of the auxiliary source power supply circuit; one end of the controllable switch is connected with the midpoint of the output bus of the power factor correction circuit, and the other end is connected with the midpoint of the auxiliary source power supply circuit; the input end of the control module is connected with the output end of the DC / DC conversion circuit, the output end of the control module is connected with the control end of the controllable switch, and the control module is used for controlling the controllable switch to be switched off under the condition that the electrical parameters meet preset conditions. Therefore, when the charging module is in light load, voltage regulation is performed on the power factor correction circuit bus, and when the charging module is in heavy load, failure of the auxiliary source is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of electric vehicle charging, and in particular to an AC / DC conversion circuit and a charging device. Background Art

[0002] In the field of electric vehicle charging, with the market requirements and fierce competition in cost, the power required for charging modules is getting higher and higher, and the power density is also getting higher and higher, resulting in the temperature inside the charging module becoming higher and higher. In order to reduce the temperature inside the charging module, it is necessary to increase the power of the fan of the charging module. The fan is powered by the auxiliary power supply in the charging module, which brings huge pressure to the transmission power of the auxiliary power supply.

[0003] Based on the existing auxiliary power supply structure, when the charging module transmits a large amount of power, the auxiliary power supply's voltage regulation capability on the power factor correction circuit bus in the charging module will become very small or even almost lost, thereby bringing the risk of failure of other devices or the auxiliary power supply. Summary of the invention

[0004] The main purpose of the present application is to provide an AC-DC conversion circuit and a charging device, so as to realize that when the power factor correction circuit of the previous stage is turned on alone or the charging module is lightly loaded, the voltage of the power factor correction circuit bus is adjusted by using a flyback converter, so as to avoid failure of the auxiliary power supply when the charging module transmits a large power.

[0005] To achieve the above object, the present application provides an AC / DC conversion circuit, including a power factor correction circuit, a DC / DC conversion circuit and an auxiliary power supply circuit, wherein the auxiliary power supply circuit includes:

[0006] An auxiliary power supply circuit, the auxiliary power supply circuit is connected in parallel between the positive output terminal and the negative output terminal of the power factor correction circuit;

[0007] A flyback converter, wherein the flyback converter is connected in parallel with the auxiliary power supply circuit, and the midpoint of the primary side of the flyback converter is connected to the midpoint of the auxiliary power supply circuit;

[0008] A controllable switch, one end of which is connected to the midpoint of the output bus of the power factor correction circuit, and the other end of which is connected to the midpoint of the auxiliary power supply circuit;

[0009] A control module, wherein the input end of the control module is connected to the output end of the DC / DC conversion circuit, the output end of the control module is connected to the control end of the controllable switch, and the control module is used to obtain the electrical parameters of the DC / DC conversion circuit and control the controllable switch to disconnect when the electrical parameters meet preset conditions.

[0010] Optionally, the auxiliary source power supply circuit includes a first capacitor and a second capacitor, and the power factor correction circuit includes a third capacitor and a fourth capacitor, the capacitance value of the first capacitor is the same as the capacitance value of the second capacitor, and the capacitance value of the third capacitor is the same as the capacitance value of the fourth capacitor; one end of the first capacitor is connected to one end of the third capacitor to form a first node, and the other end of the first capacitor is connected to one end of the second capacitor to form a midpoint of the auxiliary source power supply circuit; the other end of the second capacitor is connected to one end of the fourth capacitor to form a second node; the other end of the third capacitor is connected to the other end of the fourth capacitor to form the midpoint of the output bus of the power factor correction circuit.

[0011] Optionally, the flyback converter includes a primary circuit and a secondary circuit; the primary circuit includes a first branch and a second branch, the first branch is connected in parallel with the first capacitor, and the second branch is connected in parallel with the second capacitor; the secondary circuit includes at least one set of output loops.

[0012] Optionally, the first branch includes a first diode, a first input winding and a first transistor, the anode of the first diode is connected to the first node, the cathode of the first diode is connected to one end of the first input winding, the other end of the first input winding is connected to the first electrode of the first transistor, the second electrode of the first transistor is connected to the midpoint of the auxiliary source power supply circuit and forms the midpoint of the primary side of the flyback converter, and the control electrode of the first transistor receives the driving voltage; the second branch includes a second diode, a second input winding and a second transistor, one end of the second input winding is connected to the midpoint of the primary side of the flyback converter, the other end of the second input winding is connected to the first electrode of the second transistor, the second electrode of the second transistor is connected to the anode of the second diode, the control electrode of the second transistor receives the driving voltage, and the cathode of the second diode is connected to the second node.

[0013] Optionally, the output circuit includes a third diode, a third winding and a fifth capacitor; the cathode of the third diode is connected to one end of the fifth capacitor, the anode of the third diode is connected to one end of the third winding, the other end of the third winding is connected to the other end of the fifth capacitor to form a third node, and the third node is grounded.

[0014] Optionally, the control module includes a detection unit, a control unit and a drive circuit in communication connection in sequence; the input end of the detection unit is connected to the output end of the DC / DC conversion circuit, and the output end of the drive circuit is connected to the control end of the controllable switch; the detection unit is used to obtain the electrical parameters of the DC / DC conversion circuit, and the electrical parameters include the output voltage and output current of the DC / DC conversion circuit; the control unit is used to determine whether the electrical parameters meet the preset conditions, and output a control signal according to the determination result, and the preset conditions include that the output voltage exceeds the preset voltage and the output power exceeds the preset power, wherein the output power is determined according to the output voltage and the output current; the drive circuit is used to control the closing or opening of the controllable switch according to the control signal.

[0015] Optionally, the driving circuit includes a third transistor; the control electrode of the third transistor is connected to the output end of the control unit, the first electrode of the third transistor is connected to the control end of the controllable switch to form a fourth node, the second electrode of the third transistor is grounded, and the fourth node is connected to an external power supply.

[0016] Optionally, the driving circuit also includes a driving resistor and a driving diode; one end of the driving resistor is connected to the first electrode of the third transistor, and the other end of the driving resistor is connected to the fourth node; the cathode of the driving diode is connected to the external power supply, and the anode of the driving diode is connected to the fourth node.

[0017] Optionally, the controllable switch comprises a relay.

[0018] In addition, to achieve the above-mentioned purpose, the present application also provides a charging device, including: the aforementioned AC / DC conversion circuit; an input filter module, used to filter the input AC voltage; a soft start module, the input end of the soft start module is connected to the output end of the input filter module; wherein the input end of the power factor correction circuit in the AC / DC conversion circuit is connected to the output end of the soft start module, and the power factor correction circuit is used to rectify, power factor correct and boost the filtered AC voltage, and output the boosted DC voltage; the positive input end of the DC / DC conversion circuit in the AC / DC conversion circuit is connected to the positive input end of the power factor correction circuit, the negative input end of the DC / DC conversion circuit is connected to the negative input end of the power factor correction circuit, and the midpoint of the DC / DC conversion circuit is connected to the midpoint of the output bus of the power factor correction circuit.

[0019] The AC / DC conversion circuit of the present application sets a controllable switch between the midpoint of the output bus of the power factor correction circuit and the midpoint of the auxiliary power supply circuit. When the control module determines that the DC / DC conversion circuit transmits a small power or the power factor correction circuit is open according to the electrical parameters of the DC / DC conversion circuit, the control module controls the controllable switch to close, so that the flyback converter regulates the voltage of the bus of the power factor correction circuit; when the control module determines that the DC / DC conversion circuit transmits a large power according to the electrical parameters of the DC / DC conversion circuit, the control module controls the controllable switch to open, thereby preventing the auxiliary power supply from overheating and causing damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is one of the circuit diagrams of the AC-DC conversion circuit of the embodiment of the present application;

[0021] Figure 2 This is the second circuit diagram of the AC-DC conversion circuit of the embodiment of the present application;

[0022] Figure 3 This is the third circuit diagram of the AC-DC conversion circuit of the embodiment of the present application;

[0023] Figure 4 This is the fourth circuit diagram of the AC-DC conversion circuit of the embodiment of the present application;

[0024] Figure 5 This is the fifth circuit diagram of the AC-DC conversion circuit of the embodiment of the present application;

[0025] Figure 6 It is a schematic diagram of the structure of the charging device of an embodiment of the present application.

[0026] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] At present, high-power DC charging modules generally include two parts: the front stage and the back stage. The front stage converts the input AC voltage into a DC voltage DC output, and the back stage converts the DC voltage DC input into the DC voltage DC output required for charging.

[0029] Among them, the front stage will include an input filter (Electromagnetic Compatibility Filter, EMC) and a power factor correction circuit (Power Factor Correction circuit, PFC). The AC voltage is input to the EMC through a three-phase input, and the input AC voltage is filtered by the EMC; the AC voltage after filtering will be input to the power factor correction circuit, which will rectify, correct the power factor and boost the AC voltage, and output a DC voltage. The back stage will include a DC / DC conversion circuit, which can convert the DC voltage output by the power factor correction circuit into a stable DC voltage required by the charging module.

[0030] In order to improve the overall conversion efficiency of the charging module and meet the market's requirements for wide-voltage output, the output bus of the front-stage PFC is often set to a high voltage of about 800V, and then divided into 400V voltages for the positive and negative buses through the series connection of two large-capacity bus capacitors. Similarly, the rear-stage DC / DC conversion circuit is also divided into two paths, and the positive bus terminal of the DC / DC conversion circuit is connected to the positive output bus terminal of the PFC, and the negative bus terminal of the DC / DC conversion circuit is connected to the negative output bus terminal of the PFC.

[0031] In addition, the charging module will also include an auxiliary power supply, which is mainly used to power the control chip, fan and other devices in the front and rear stages. There are many ways to supply the auxiliary voltage, but the most common and direct way is that the auxiliary power supply directly draws power from the output bus of the PFC to power the devices in the charging module.

[0032] However, if the power is only taken from the positive output bus or the negative output bus of the PFC, it will inevitably cause the voltage of the positive output bus of the PFC to be uneven with the voltage of the negative output bus, which will lead to different transmission powers of the positive and negative paths of the DC / DC conversion circuit, making the control system in the charging module difficult to control or output imbalance. If it works in this way for a long time, it will also cause some components in the charging module to overheat, thereby bringing a great risk of failure to the charging module. Therefore, the auxiliary power supply must be powered from both the positive and negative output buses of the PFC.

[0033] The dual-winding flyback converter has dual power supply on the primary side, and the two circuits on the primary side are symmetrical, so the heat is dispersed and will not cause overheating of individual components, thereby improving the reliability of operation; and, precisely because the dual-winding flyback converter has dual power supply on the primary side, it can simultaneously draw power from the PFC bus, so the dual-winding flyback converter can assist the PFC bus in voltage regulation. Therefore, in the application of high-power charging modules, the auxiliary power topology usually adopts a dual-winding flyback converter.

[0034] The dual-winding flyback converter is powered by the positive and negative bus lines. Due to the characteristics of its own topological structure, when the dual-winding flyback converter is working, if the positive bus and negative bus voltages are equal, then the power transmitted by the positive and negative bus lines will be basically equal; if the positive bus voltage is greater than the negative bus voltage, then the power transmitted by the positive bus line will be greater than the power transmitted by the negative bus line; if the negative bus voltage is greater than the positive bus voltage, then the power transmitted by the negative bus line will be greater than the power transmitted by the positive bus line. It can be seen that the dual-winding flyback converter has the function of assisting the bus line to adjust the voltage, which is the advantage of the dual-winding flyback converter.

[0035] In addition, due to the characteristics of its own topological structure, when there is a small voltage difference between the positive and negative inputs of the dual-winding flyback converter, it will cause serious current imbalance between the positive and negative inputs. Long-term current imbalance between the positive and negative inputs may cause the dual-winding flyback converter to burn out.

[0036] Furthermore, when the auxiliary power supply is used in a low-power scenario (i.e., the transmission power of the charging module is small), the transmission power of the auxiliary power supply accounts for a large proportion of the transmission power of the charging module. Therefore, the dual-winding flyback converter in the auxiliary power supply has a more obvious voltage regulation effect on the PFC bus. However, when the auxiliary power supply is used in a high-power scenario (i.e., the transmission power of the charging module is large), the transmission power of the auxiliary power supply accounts for a small proportion of the transmission power of the charging module. The power borne by the auxiliary power supply may be less than 0.7% of the transmission power of the charging module. Therefore, the voltage regulation ability of the dual-winding flyback converter in the auxiliary power supply on the PFC bus will become very small or even almost lost.

[0037] At present, there are usually two ways to connect the midpoint of the PFC output bus and the midpoint of the auxiliary power supply. The first way is to hard-connect the midpoint of the PFC output bus and the midpoint of the auxiliary power supply through PCB routing or external soft wires. In this way, the PFC and the auxiliary power supply are connected. When the front-stage PFC is turned on or the rear-stage DC / DC conversion circuit is lightly loaded, the dual-winding flyback converter can achieve voltage equalization regulation of the PFC output bus.

[0038] However, when the front-stage PFC and the back-stage DC / DC conversion circuit are turned on at the same time, and the DC / DC conversion circuit transmits a large amount of power, the dual-winding flyback converter's ability to regulate the voltage of the PFC output bus will become very small or even almost lost; at the same time, due to the differences in circuit power devices and control waves, and more importantly, problems such as control methods and control accuracy, when the DC / DC conversion circuit transmits a large amount of power, it is inevitable that there will be a voltage difference between the positive and negative buses of the dual-winding flyback converter. Therefore, this will cause serious current imbalance in the positive and negative paths of the dual-winding flyback converter, which may eventually cause the auxiliary power supply to burn out over time.

[0039] The second method is that the midpoint of the PFC busbar is not hard-connected to the midpoint of the auxiliary power supply. In this case, by constructing a power supply circuit of upper and lower dual capacitors, the dual-winding flyback converter is connected in parallel with the self-built capacitor power supply circuit. Although this connection method can avoid the risk of overheating and damage of the dual-winding flyback converter due to long-term uneven current, it also loses the opportunity to use the topological advantages of the dual-winding flyback converter to balance the PFC busbar when the front stage is single-open or the rear stage is lightly loaded.

[0040] To this end, the embodiments of the present application provide an AC-DC conversion circuit and a charging device. When the PFC before the charging module is turned on or the charging module is lightly loaded, the midpoint of the PFC output bus is connected to the midpoint of the auxiliary power supply, so that the PFC bus can be self-equalized by utilizing the topological advantages of the dual-winding flyback converter itself; when the charging module transmits a large power, the connection between the midpoint of the PFC output bus and the midpoint of the auxiliary power supply is disconnected, thereby avoiding the consequences of overheating and damage caused by uneven current of the auxiliary power supply due to uneven voltage of the positive and negative buses of the dual-winding flyback converter.

[0041] Figure 1 This is one of the circuit diagrams of the AC-DC conversion circuit of the embodiment of the present application.

[0042] like Figure 1 As shown, the AC / DC conversion circuit may include an auxiliary power supply circuit 100, a power factor correction circuit 200 and a DC / DC conversion circuit 300, and the auxiliary power supply circuit 100 may include an auxiliary power supply circuit 110, a flyback converter 120, a controllable switch 130 and a control module 140, wherein the auxiliary power supply circuit 110 is connected in parallel between the positive output terminal and the negative output terminal of the power factor correction circuit 200; the flyback converter 120 is connected in parallel with the auxiliary power supply circuit 110, and the midpoint of the primary side of the flyback converter 120 is connected to the auxiliary power supply circuit 110; one end of the controllable switch 130 is connected to the midpoint of the output bus of the power factor correction circuit 200, and the other end of the controllable switch 130 is connected to the midpoint of the auxiliary power supply circuit 110; the input end of the control module 140 is connected to the output end of the DC / DC conversion circuit 300, and the output end of the control module 140 is connected to the control end of the controllable switch 130. The control module 140 is used to obtain the electrical parameters of the DC / DC conversion circuit 300, and control the controllable switch 130 to disconnect when the electrical parameters meet the preset conditions.

[0043] First of all, it should be noted that two large-capacity electrolytic capacitors of the same capacity are connected in series on the output bus of the power factor correction circuit 200 (PFC). The output voltage on the PFC output bus can be evenly divided by the two capacitors of the same capacity, that is, the positive output bus voltage is equal to the negative output bus voltage and equal to half of the PFC output voltage.

[0044] In this embodiment, the auxiliary power supply circuit 110 is a symmetrical structure, and the auxiliary power supply circuit 110 is also divided into positive and negative inputs. Among them, the positive input end of the auxiliary power supply circuit 110 is connected to the positive output end of the PFC output bus, the negative input end of the auxiliary power supply circuit 110 is connected to the negative output end of the PFC bus, and the midpoint of the auxiliary power supply circuit 110 is connected to the midpoint of the PFC output bus through the controllable switch 130. It should be noted that the midpoint of the PFC output bus is the midpoint of the bus between the two large-capacity electrolytic capacitors; in addition, the auxiliary power supply circuit 110 is a symmetrical structure, and the structures on both sides of the midpoint of the auxiliary power supply circuit 110 are symmetrical.

[0045] In this embodiment, the flyback converter 120 used is a dual-winding flyback converter, and the flyback converter 120 also has positive and negative inputs, and the structure of the flyback converter 120 is a symmetrical structure symmetrical about its midpoint. The positive input terminal of the flyback converter 120 is connected to the positive input terminal of the auxiliary power supply circuit 110, the negative input terminal of the flyback converter 120 is connected to the negative input terminal of the auxiliary power supply circuit 110, and the midpoint of the flyback converter 120 is connected to the midpoint of the auxiliary power supply circuit 110.

[0046] Specifically, the auxiliary power supply circuit 110 has two inputs, so the auxiliary power supply circuit 110 can evenly draw power from the positive and negative output buses of the PFC, respectively, and then input it into the flyback converter 120, and discharge it to the load by the flyback converter 120. As an example, if the PFC output bus voltage is 800V, since the auxiliary power supply circuit 110 is a symmetrical structure, the auxiliary power supply circuit 110 evenly divides 400V voltage from top to bottom, that is, the voltage at the positive bus of the auxiliary power supply circuit 110 is 400V, and the voltage at the negative bus of the auxiliary power supply circuit 110 is 400V. Therefore, the positive input terminal of the flyback converter 120 inputs a 400V voltage, and the negative input terminal of the flyback converter 120 also inputs a 400V voltage.

[0047] It is worth mentioning that when the controllable switch 130 is disconnected, even if there is a certain voltage difference between the upper and lower voltages of the auxiliary power supply circuit 110, due to the topological characteristics of the flyback converter 120 itself and the fact that the auxiliary power supply circuit 110 is not externally connected to the main power module, the flyback converter 120 can play a role in equalizing the voltage of the positive and negative buses of the auxiliary power supply circuit 110. The positive and negative buses of the auxiliary power supply circuit 110 increase and decrease in a cycle. In the long run, the positive and negative buses of the auxiliary power supply circuit 110 are basically equal in voltage, so the heat generation of the upper and lower branches of the primary side of the flyback converter 120 is also basically equal, avoiding the problem of uneven current caused by uneven voltage of the two inputs of the flyback converter 120.

[0048] Therefore, when the controllable switch 130 is closed, the flyback converter 120 can use its own characteristics to regulate the voltage of the PFC output bus; when the controllable switch 130 is open, the flyback converter 120 can use its own characteristics to regulate the voltage of the auxiliary source power supply circuit 110.

[0049] Furthermore, the control module 140 is mainly used to collect electrical parameters of the DC / DC conversion circuit 300, and determine whether the charging module is in the front-stage PFC single-open state or the charging module light-load state, or the charging module heavy-load state according to the electrical parameters of the DC / DC conversion circuit 300, so as to control the controllable switch 130 to be closed or turned off according to the output state of the charging module, that is, to control whether the midpoint of the PFC output bus is connected to the midpoint of the auxiliary source power supply circuit 110 of the auxiliary power supply circuit 100.

[0050] When the control module 140 determines that the charging module is in the pre-stage PFC single-open state or the charging module is in the light-load state, the control module 140 can control the controllable switch 130 to close, so that the self-voltage equalization function of the flyback converter 120 can be used to equalize the voltage of the PFC output bus. When the control module 140 determines that the charging module is in the heavy-load state, the voltage equalization regulation effect of the flyback converter 120 is poor. At this time, the control module 140 can control the controllable switch 130 to be disconnected, and the flyback converter 120 can use its own characteristics to adjust the voltage of the auxiliary power supply circuit 110, thereby avoiding the problem of uneven current due to uneven voltage of the two inputs of the flyback converter 120, and ensuring the reliability of the auxiliary power supply circuit 100.

[0051] Figure 2 This is the second circuit diagram of the AC-DC conversion circuit of the embodiment of the present application.

[0052] like Figure 2 As shown, in some embodiments, the auxiliary source power supply circuit 110 may include a first capacitor C1 and a second capacitor C2, and the power factor correction circuit 200 may include a third capacitor C3 and a fourth capacitor C4, the capacitance value of the first capacitor C1 is the same as the capacitance value of the second capacitor C2, and the capacitance value of the third capacitor C3 is the same as the capacitance value of the fourth capacitor C4.

[0053] Among them, one end of the first capacitor C1 is connected to one end of the third capacitor C3 to form a first node N1, the other end of the first capacitor C1 is connected to one end of the second capacitor C2 to form a midpoint of the auxiliary source power supply circuit 110; the other end of the second capacitor C2 is connected to one end of the fourth capacitor C4 to form a second node N2; the other end of the third capacitor C3 is connected to the other end of the fourth capacitor C4 to form the midpoint of the output bus of the power factor correction circuit 200.

[0054] It should be noted that the third capacitor C3 and the fourth capacitor C4 are the two large-capacity electrolytic capacitors with the same capacity as mentioned above, and the first capacitor C1 and the second capacitor C2 can be two small-capacity electrolytic capacitors with the same capacity.

[0055] Specifically, the auxiliary power supply circuit 110 of this embodiment can be composed of two small-capacity electrolytic capacitors connected in series. Figure 2 As shown, the positive output bus terminal of the PFC is marked as BUS+, the midpoint of the PFC output bus is marked as BUS_N, the negative output bus terminal of the PFC is marked as BUS-, and the midpoint of the auxiliary power supply circuit 110 is marked as BUS_M. A third capacitor C3 is connected between BUS+ and BUS_N, and a fourth capacitor C4 is connected between BUS- and BUS_N. One end of the first capacitor C1 is connected to BUS+, and the other end of the first capacitor C1 is connected to BUS_M, one end of the second capacitor C2 is connected to BUS_M, and the other end of the second capacitor C2 is connected to BUS-.

[0056] In addition, a positive input terminal of the flyback converter 120 is connected to a first node N1 in the auxiliary power supply circuit 110 , and a negative input terminal of the flyback converter 120 is connected to a second node N2 in the auxiliary power supply circuit 110 .

[0057] The first capacitor C1 and the second capacitor C2 are used to store the electric energy obtained from the positive and negative output buses of the PFC respectively, and supply power to the flyback converter 120. In this embodiment, because the capacitance values ​​of the first capacitor C1 and the second capacitor C2 are the same, the voltage division of the first capacitor C1 and the second capacitor C2 is substantially the same.

[0058] In some embodiments, the flyback converter 120 may include a primary circuit and a secondary circuit; the primary circuit includes a first branch and a second branch, the first branch is connected in parallel with the first capacitor C1, and the second branch is connected in parallel with the second capacitor C2; the secondary circuit includes at least one set of output loops.

[0059] Specifically, the input end of the first branch in the primary circuit is connected to the first node N1, and the output end of the first branch is connected to BUS_M, so that the first branch is connected in parallel with the first capacitor C1 and forms a loop. The input end of the second branch in the primary circuit is connected to BUS_M, and the output end of the second branch is connected to the second node N2, so that the second branch is connected in parallel with the second capacitor C2 and forms a loop. In addition, the composition of the first branch is the same as that of the second branch.

[0060] The primary circuit of the flyback converter 120 is connected to the auxiliary power supply circuit 110 , and the auxiliary power supply circuit 110 supplies power to the primary circuit of the flyback converter 120 .

[0061] In this embodiment, the secondary circuit may include at least one group of output loops, and each group of output loops has the same composition. Specifically, the number of output loops may be determined according to the number of devices that need to be powered in the charging module. For example, if the devices that need to be powered by an auxiliary power supply in the charging module include a DSP (Digital Signal Processing) chip, a control chip, and a fan, the number of output loops may also be three, and each output loop is connected to the three devices respectively and supplies power to them.

[0062] Figure 3 This is the third circuit diagram of the AC-DC conversion circuit of the embodiment of the present application.

[0063] like Figure 3 As shown, in some embodiments, the first branch may include a first diode D1, a first input winding L1, and a first transistor Q1, the anode of the first diode D1 is connected to the first node N1, the cathode of the first diode D1 is connected to one end of the first input winding, the other end of the first input winding is connected to the first electrode of the first transistor Q1, the second electrode of the first transistor Q1 is connected to the midpoint of the auxiliary source power supply circuit 110 and forms the midpoint of the primary side in the flyback converter 120, and the control electrode of the first transistor receives the driving voltage.

[0064] The second branch may include a second diode D2, a second input winding L2 and a second transistor Q2, one end of the second input winding is connected to the midpoint of the primary side in the flyback converter 120, the other end of the second input winding is connected to the first electrode of the second transistor Q2, the second electrode of the second transistor Q2 is connected to the anode of the second diode D2, the control electrode of the second transistor receives a driving voltage, and the cathode of the second diode D2 is connected to the second node N2.

[0065] Among them, the first diode D1 and the second diode D2 are used for reverse protection to prevent the reverse voltage generated by the first branch to the second branch from feeding back current to the negative bus input power supply, or to prevent the reverse voltage generated by the second branch to the first branch from feeding back current to the positive bus input power supply; the first transistor Q1 and the second transistor Q2 are used as switches for charging and discharging the flyback converter 120.

[0066] It should be noted that the first transistor Q1 and the second transistor Q2 may be any type of transistor such as an IGBT (Insulated Gate Bipolar Transistor), a MOS transistor, etc., and no specific limitation is made here.

[0067] Continue to refer Figure 3In some embodiments, the output circuit includes a third diode D3, a third winding L3 and a fifth capacitor C5, the cathode of the third diode D3 is connected to one end of the fifth capacitor C5, the anode of the third diode D3 is connected to one end of the third winding L3, the other end of the third winding L3 is connected to the other end of the fifth capacitor C5 to form a third node N3, and the third node N3 is grounded.

[0068] It should be noted that a voltage output terminal Vs may be provided between the third diode D3 and the fifth capacitor C5, and power may be supplied to the load through the voltage output terminal Vs.

[0069] Specifically, the working process of the flyback converter 120 can be: when the first transistor Q1 and the second transistor Q2 are turned on and the third diode D3 is turned off, the flyback converter 120 stores the electric energy input by the auxiliary power supply circuit 110; at this time, if power is required to be supplied to the load, the fifth capacitor C5 supplies power to the load. When the first transistor Q1 and the second transistor Q2 are turned off and the third diode D3 is turned on, the flyback converter 120 supplies power to the load through the output circuit and stores energy in the fifth capacitor C5 at the same time.

[0070] Figure 4 This is the fourth circuit diagram of the AC-DC conversion circuit of the embodiment of the present application.

[0071] like Figure 4 As shown, in some embodiments, the control module 140 may include a communication-connected detection unit 141 , a control unit 142 , and a driving circuit 143 in sequence.

[0072] The input end of the detection unit 141 is connected to the output end of the DC / DC conversion circuit 300, and the output end of the drive circuit 143 is connected to the control end of the controllable switch 130; the detection unit 141 is used to obtain the electrical parameters of the DC / DC conversion circuit 300, and the electrical parameters include the output voltage and output current of the DC / DC conversion circuit 300; the control unit 142 is used to determine whether the electrical parameters meet the preset conditions, and output a control signal according to the determination result, and the preset conditions include that the output voltage exceeds the preset voltage and the output power exceeds the preset power, wherein the output power is determined according to the output voltage and the output current; the drive circuit 143 is used to control the closing or closing of the controllable switch 130 according to the control signal.

[0073] In this embodiment, the detection unit 141 may be a voltage and current sampling circuit, and the voltage and current sampling circuit is connected to the output end of the DC / DC conversion circuit 300 to collect the output voltage and output current of the DC / DC conversion circuit 300. It should be noted that the voltage and current sampling circuit may adopt an existing sampling circuit, which will not be specifically described here.

[0074] Furthermore, the control unit 142 may include an MCU (Microcontroller Unit) chip, or may include an existing main control chip, in which a corresponding functional unit may be developed, and the output end of the detection unit 141 may be connected to the output end of the MCU chip. Specifically, when the charging module is powered on and the auxiliary power supply circuit 100 is started, after the detection unit 141 obtains the output voltage and output current of the DC / DC conversion circuit 300, the MCU chip may run the following program:

[0075] After the control unit 142 receives the output voltage of the DC / DC conversion circuit 300 sent by the detection unit 141, it can first compare the output voltage with the preset voltage. It should be noted here that the preset voltage can be set according to the minimum DC output voltage specified in the charging module specification. For example, if the minimum DC output voltage specified in the charging module specification is 200V, the preset voltage can also be set to 200V. Therefore, the current output state of the charging module can be determined by comparing the output voltage with the preset voltage.

[0076] As an example, if the preset voltage is 200V and the output voltage received by the control unit 142 is 100V, it means that the charging module may be in a state where the front-stage PFC is not turned on or is turned on alone. As another example, if the preset voltage is 200V and the output voltage received by the control unit 142 is 300V, it means that the rear-stage DC / DC conversion circuit 300 is turned on, and the charging module may be in a light load state (i.e., the transmission power of the charging module is small) or in a heavy load state (i.e., the transmission power of the charging module is large).

[0077] When the control unit 142 determines that the output voltage exceeds the preset voltage, the control unit 142 calculates the output power of the charging module according to the output voltage and the output current. The output power can be calculated by the following formula:

[0078] Po=Vo*Io

[0079] Among them, Po is the output power, Vo is the output voltage, and Io is the output current.

[0080] After determining the output power of the charging module, the control module 140 compares the output power with the preset power to further determine the current state of the charging module.

[0081] Specifically, when the output power is less than or equal to the preset power, it is determined that the charging module is currently in the state of the front-stage PFC single opening or the charging module light load. At this time, the control unit 142 controls the controllable switch 130 to remain in a closed state through the drive circuit 143, and the midpoint of the PFC bus is connected to the midpoint of the auxiliary power supply circuit 110, so that the flyback converter 120 can play its self-voltage equalization role on the PFC bus when the front-stage PFC is single opened or the charging module is lightly loaded.

[0082] When the output power exceeds the preset power, it is determined that the charging module is currently in an overload state. At this time, the control signal output by the control unit 142 to the drive circuit 143 is a shutdown signal, that is, the controllable switch 130 is controlled to be turned off through the drive circuit 143. As a result, the midpoint of the PFC bus is disconnected from the midpoint of the auxiliary power supply circuit 110, and the flyback converter 120 can use its own characteristics to regulate the voltage of the auxiliary power supply circuit 110, avoiding the problem of uneven current in the flyback converter 120, and ensuring the reliability of the auxiliary power supply circuit 100.

[0083] In some embodiments, after the controllable switch 130 is controlled to be closed or turned off, the output voltage and current of the charging module can be re-detected after a certain preset time. Because the process of overheating caused by the uneven current of the flyback converter 120 is a slow and cumulative process, it is not necessary to frequently control the controllable switch 130 to be closed or turned off, thereby avoiding damage to the controllable switch 130 due to frequent operation and the problem that the control module 140 occupies a large amount of memory due to frequent operation.

[0084] Figure 5 This is the fifth circuit diagram of the AC-DC conversion circuit of the embodiment of the present application.

[0085] like Figure 5 As shown, in some embodiments, the driving circuit 143 includes a third transistor Q3; the control electrode of the third transistor Q3 is connected to the output end of the control unit 142, the first electrode of the third transistor Q3 is connected to the control end of the controllable switch and forms a fourth node, the second electrode of the third transistor is grounded, and the fourth node is connected to an external power supply.

[0086] It should be noted that the third transistor Q3 can be any transistor such as a triode, a MOS transistor, etc., and no specific limitation is made here.

[0087] In some embodiments, the driving circuit also includes a driving resistor R1 and a driving diode D4; one end of the driving resistor R1 is connected to the first electrode of the third transistor Q3, and the other end of the driving resistor R1 is connected to the fourth node N4; the cathode of the driving diode D4 is connected to the external power supply, and the anode of the driving diode D4 is connected to the fourth node N4.

[0088] Continue to refer Figure 5 In some embodiments, the controllable switch 130 may include a relay K1. In this embodiment, the relay K1 includes four pins, wherein the first pin is connected to the midpoint BUS_N of the PFC bus, the second pin is connected to the midpoint BUS_M of the auxiliary power supply circuit 110, the third pin is connected to the external power supply VCC, and the fourth pin is connected to the fourth node N4.

[0089] It should be noted that the controllable switch 130 in this embodiment may be a normally open switch. In addition, the output voltages of the two external power supplies used in this embodiment may be the same or similar.

[0090] Specifically, the initial state of the relay K1 contact can be set to a normally open state. When the control signal sent by the control unit 142 to the drive circuit 143 is a closing signal, the closing signal is a high-level signal, which turns on the third transistor Q3, and then the fourth pin of the relay K1 is grounded through the driving resistor R1, so that the current flows in the relay K1 coil and the relay K1 contact is closed. When the control signal sent by the control circuit is a shut-off signal, the shut-off signal is a low-level signal, which turns off the third transistor Q3, and the fourth pin of the relay K1 is connected to the external power supply through the driving diode D4. At this time, the voltages at both ends of the relay K1 coil are the same. Therefore, there is no current flowing in the relay K1 coil, so that the magnetic field of the relay K1 coil disappears, so that the relay K1 core cannot control the contact to close, and the contact automatically opens.

[0091] In this embodiment, the driving resistor R1 is disposed between the third transistor Q3 and the relay K1 to control the magnitude of the current input to the relay K1, thereby ensuring the safe operation of the circuit; in addition, the driving diode D4 is used for reverse protection.

[0092] Therefore, by setting a relay K1 at the midpoint of the PFC bus and the midpoint of the auxiliary power supply circuit 110, the output voltage and output current of the charging module are obtained through the detection unit 141, and the control unit 142 determines the current charging state of the charging module according to the output voltage and output current. When the charging module is in the state of the front-stage PFC single opening or the charging module is lightly loaded, the control unit 142 controls the relay K1 to close by controlling the driving circuit 143, so that the midpoint of the PFC bus is connected to the midpoint of the auxiliary power supply circuit 110, and then the flyback converter 120 performs voltage equalization regulation on the PFC bus. When the charging module is currently in a heavy load state, the control unit 142 controls the relay K1 to turn off by controlling the driving circuit 143, so that the midpoint of the PFC bus is disconnected from the midpoint of the auxiliary power supply circuit 110, and the flyback converter 120 can use its own characteristics to adjust the voltage of the auxiliary power supply circuit 110, avoid the problem of uneven current in the flyback converter 120, and ensure the reliability of the auxiliary power supply circuit 100.

[0093] Figure 6 It is a schematic diagram of the structure of the charging device of an embodiment of the present application.

[0094] like Figure 6 As shown, the charging device may include: an AC / DC conversion circuit, an input filter module 400 and a soft start module 500 in any of the above embodiments, wherein the AC / DC conversion circuit includes an auxiliary power supply circuit 100, a power factor correction circuit 200, and a DC / DC conversion circuit 300.

[0095] The input filter module 400 can be used to filter the input AC voltage; the input end of the soft start module 500 is connected to the output end of the input filter module 400; the input end of the power factor correction circuit 200 is connected to the output end of the soft start module 500, and the power factor correction circuit 200 is used to rectify, power factor correct and boost the filtered AC voltage, and output the boosted DC voltage; the positive input end of the DC / DC conversion circuit 300 is connected to the positive input end of the power factor correction circuit 200, the negative input end of the DC / DC conversion circuit 300 is connected to the negative input end of the power factor correction circuit 200, and the midpoint of the DC / DC conversion circuit 300 is connected to the midpoint of the power factor correction circuit 200.

[0096] Specifically, the input filter module 400 may be an EMC filter. The AC voltage is input to the input filter module 400 in a three-phase input manner, and the input filter module 400 performs filtering processing on the AC voltage.

[0097] The soft start module 500 is also connected to the input filter module 400 in three phases, and the soft start module 500 may include a soft start relay and a soft start resistor connected in parallel. When the charging module is powered on, the input soft start relay is disconnected first, so that the current output by the input filter module 400 flows from the branch where the soft start resistor is located to the power factor correction circuit 200 (PFC); when the voltage of the charging module is stable, the soft start relay is controlled to be turned on, so that the soft start resistor is short-circuited, and then the current output by the input filter module 400 flows from the branch where the soft start relay is located to the power factor correction circuit 200. Because the impedance of the soft start relay is smaller than the soft start resistor, the use of this method for soft starting can improve the efficiency of the charging module.

[0098] The PFC is also three-phase connected with the soft start module 500. The PFC is composed of two large-capacity electrolytic capacitors with the same capacity connected in series on the bus. The specific structure of the PFC can refer to the structure of the PFC in the aforementioned AC-DC conversion circuit embodiment, which will not be repeated here. The PFC is used to rectify the filtered AC voltage output by the soft start module 500, as well as to correct the power factor, and the PFC then outputs a boosted DC voltage.

[0099] The DC / DC conversion circuit 300 can be a DC / DC converter. The DC / DC conversion circuit 300 and the PFC are connected in three lines. Specifically, the positive input end of the DC / DC conversion circuit 300 is connected to the positive bus of the PFC, the negative input end of the DC / DC conversion circuit 300 is connected to the negative bus of the PFC, and the midpoint of the DC / DC conversion circuit 300 is connected to the bus midpoint of the PFC. The DC / DC conversion circuit 300 is used to convert the boosted DC voltage output by the PFC into the DC voltage required for charging output by the charging module.

[0100] The structure of the auxiliary power supply circuit 100 and the connection method with other modules can refer to the structure and connection method of the auxiliary power supply circuit 100 in the aforementioned AC / DC conversion circuit embodiment, which will not be repeated here. The auxiliary power supply circuit 100 is used to power the control circuit of the soft start module 500, the power factor correction circuit 200 and the DC / DC conversion circuit 300, and to power the fan and other devices of the charging module.

[0101] Therefore, the charging device adopts the auxiliary power supply circuit 100, and sets a relay K1 at the midpoint of the PFC bus and the midpoint of the auxiliary power supply circuit 110, obtains the output voltage and output current of the charging module through the detection unit 141, and the control unit 142 determines the current charging state of the charging module according to the output voltage and output current. When the charging module is in the state of the front-stage PFC single opening or the charging module is lightly loaded, the control unit 142 controls the relay K1 to close by controlling the driving circuit 143, so that the midpoint of the PFC bus is connected to the midpoint of the auxiliary power supply circuit 110, and then the flyback converter 120 performs voltage equalization regulation on the PFC bus. When the charging module is currently in a heavy load state, the control unit 142 controls the relay K1 to turn off by controlling the driving circuit 143, so that the midpoint of the PFC bus is disconnected from the midpoint of the auxiliary power supply circuit 110, and the flyback converter 120 can use its own characteristics to adjust the voltage of the auxiliary power supply circuit 110, avoid the problem of uneven current in the flyback converter 120, and ensure the reliability of the operation of the auxiliary power supply circuit 100.

[0102] It should be noted that for details not disclosed in the charging device of this embodiment, please refer to the details disclosed in the embodiment of the AC-DC conversion circuit in the embodiment of this specification, and no further details will be given here.

[0103] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application 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. However, 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 embodiments of the present application.

Claims

1. An AC-DC conversion circuit, characterized in that: It includes a power factor correction circuit, a DC / DC conversion circuit and an auxiliary power supply circuit, wherein the auxiliary power supply circuit includes: An auxiliary power supply circuit, the auxiliary power supply circuit is connected in parallel between the positive output terminal and the negative output terminal of the power factor correction circuit; A flyback converter, wherein the flyback converter is connected in parallel with the auxiliary power supply circuit, and the midpoint of the primary side of the flyback converter is connected to the midpoint of the auxiliary power supply circuit; A controllable switch, one end of which is connected to the midpoint of the output bus of the power factor correction circuit, and the other end of which is connected to the midpoint of the auxiliary power supply circuit; A control module, wherein the input end of the control module is connected to the output end of the DC / DC conversion circuit, the output end of the control module is connected to the control end of the controllable switch, and the control module is used to obtain the electrical parameters of the DC / DC conversion circuit and control the controllable switch to disconnect when the electrical parameters meet preset conditions.

2. The AC-DC conversion circuit according to claim 1, characterized in that: The auxiliary power supply circuit includes a first capacitor and a second capacitor, the power factor correction circuit includes a third capacitor and a fourth capacitor, the capacitance value of the first capacitor is the same as the capacitance value of the second capacitor, and the capacitance value of the third capacitor is the same as the capacitance value of the fourth capacitor; One end of the first capacitor is connected to one end of the third capacitor to form a first node, and the other end of the first capacitor is connected to one end of the second capacitor to form a midpoint of the auxiliary source power supply circuit; The other end of the second capacitor is connected to one end of the fourth capacitor to form a second node; The other end of the third capacitor is connected to the other end of the fourth capacitor and forms a midpoint of the output bus of the power factor correction circuit.

3. The AC-DC conversion circuit according to claim 2, characterized in that: The flyback converter comprises a primary circuit and a secondary circuit; The primary circuit includes a first branch and a second branch, the first branch is connected in parallel with the first capacitor, and the second branch is connected in parallel with the second capacitor; The secondary circuit includes at least one set of output loops.

4. The AC-DC conversion circuit according to claim 3, characterized in that: The first branch includes a first diode, a first input winding, and a first transistor, an anode of the first diode is connected to the first node, a cathode of the first diode is connected to one end of the first input winding, the other end of the first input winding is connected to a first electrode of the first transistor, a second electrode of the first transistor is connected to a midpoint of the auxiliary source power supply circuit and forms a midpoint of the primary side of the flyback converter, and a control electrode of the first transistor receives a driving voltage; The second branch includes a second diode, a second input winding and a second transistor, one end of the second input winding is connected to the midpoint of the primary side of the flyback converter, the other end of the second input winding is connected to the first electrode of the second transistor, the second electrode of the second transistor is connected to the anode of the second diode, the control electrode of the second transistor receives the driving voltage, and the cathode of the second diode is connected to the second node.

5. The AC-DC conversion circuit according to claim 3, characterized in that: The output loop includes a third diode, a third winding and a fifth capacitor; The cathode of the third diode is connected to one end of the fifth capacitor, the anode of the third diode is connected to one end of the third winding, the other end of the third winding is connected to the other end of the fifth capacitor to form a third node, and the third node is grounded.

6. The AC-DC conversion circuit according to claim 1, characterized in that: The control module includes a detection unit, a control unit and a drive circuit in communication connection in sequence; the input end of the detection unit is connected to the output end of the DC / DC conversion circuit, and the output end of the drive circuit is connected to the control end of the controllable switch; The detection unit is used to obtain the electrical parameters of the DC / DC conversion circuit, wherein the electrical parameters include the output voltage and output current of the DC / DC conversion circuit; The control unit is used to determine whether the electrical parameter meets the preset condition and output a control signal according to the determination result, wherein the preset condition includes that the output voltage exceeds the preset voltage and the output power exceeds the preset power, wherein the output power is determined according to the output voltage and the output current; The driving circuit is used to control the closing or opening of the controllable switch according to the control signal.

7. The AC-DC conversion circuit according to claim 6, characterized in that: The driving circuit includes a third transistor; The control electrode of the third transistor is connected to the output end of the control unit, the first electrode of the third transistor is connected to the control end of the controllable switch to form a fourth node, the second electrode of the third transistor is grounded, and the fourth node is connected to an external power supply.

8. The AC-DC conversion circuit according to claim 7, characterized in that: The driving circuit also includes a driving resistor and a driving diode; One end of the driving resistor is connected to the first electrode of the third transistor, and the other end of the driving resistor is connected to the fourth node; A cathode of the driving diode is connected to the external power supply, and an anode of the driving diode is connected to the fourth node.

9. The AC-DC conversion circuit according to claim 1, characterized in that: The controllable switch comprises a relay.

10. A charging device, characterized in that: include: The AC-DC conversion circuit according to any one of claims 1 to 9; An input filter module is used to filter the input AC voltage; A soft start module, the input end of the soft start module is connected to the output end of the input filter module; The input end of the power factor correction circuit in the AC / DC conversion circuit is connected to the output end of the soft start module, and the power factor correction circuit is used to rectify, power factor correct and boost the filtered AC voltage, and output the boosted DC voltage; The positive input terminal of the DC / DC conversion circuit in the AC / DC conversion circuit is connected to the positive input terminal of the power factor correction circuit, the negative input terminal of the DC / DC conversion circuit is connected to the negative input terminal of the power factor correction circuit, and the midpoint of the DC / DC conversion circuit is connected to the midpoint of the output bus of the power factor correction circuit.

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