LLC resonant converter and charging device

Abstract

The embodiment of the utility model relates to the technical field of power converters, in particular to an LLC resonant converter and a charging device. The converter comprises at least two LLC conversion circuits connected in parallel, at least two current sampling circuits and a control circuit. And a switching circuit in the LLC conversion circuit is used for converting an input direct current signal into an alternating current signal according to the switching control signal. The current sampling circuit is used for sampling the loop current of the corresponding LLC conversion circuit and generating a current sampling signal. And the control circuit is used for generating a switch control signal corresponding to each LLC conversion circuit, and adjusting the frequency and / or duty ratio of each switch control signal by comparing each current sampling signal in real time. Through the above structure, the loop current of each LLC conversion circuit is obtained and compared, and the frequency and / or duty ratio of each switch control signal is adjusted according to the comparison result, so that the output current of each LLC conversion circuit is kept balanced.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of power converter, in particular to an LLC resonant converter and a charging device. BACKGROUND

[0002] The LLC resonant conversion circuit has the characteristics of high efficiency, small switching tube stress and easy realization of high frequency and miniaturization, and is widely used in charging equipment. However, due to the differences in the parameters of power devices such as resonant capacitor, resonant inductor and transformer excitation inductor, when used in multiple parallel ways, the working states of each LLC conversion circuit are often different, especially the output current imbalance problem, which brings the risk of electrical stress and thermal stress to the device. CONTENT OF THE INVENTION

[0003] An object of embodiments of the present application is to provide an LLC resonant converter and a charging device to solve the technical problem of output current imbalance of each LLC resonant conversion circuit in the LLC resonant converter.

[0004] In a first aspect, embodiments of the present application provide an LLC resonant converter, comprising:

[0005] at least two LLC conversion circuits connected in parallel, the LLC conversion circuit comprising a switching circuit, the switching circuit being configured to convert an input DC signal into an AC signal according to a switching control signal; and

[0006] at least two current sampling circuits, each current sampling circuit being connected to a corresponding LLC conversion circuit, the current sampling circuit being configured to sample the loop current of the corresponding LLC conversion circuit and generate a current sampling signal; and

[0007] a control circuit, the control circuit being connected to each sampling circuit and each switching circuit, the control circuit being configured to generate the switching control signal corresponding to each LLC conversion circuit, and adjust the frequency and / or duty cycle of the switching control signal of each LLC conversion circuit by comparing the current sampling signals in real time, so that the output currents of each LLC conversion circuit remain consistent.

[0008] Optionally, the LLC conversion circuit further comprises a primary resonant cavity circuit, a secondary resonant cavity circuit and a DC output circuit, the switching circuit is electrically connected to the primary resonant cavity circuit, the primary resonant cavity circuit is coupled to the secondary resonant cavity circuit, the secondary resonant cavity circuit is electrically connected to the DC output circuit, at least one of the primary resonant cavity circuit, the secondary resonant cavity circuit and the DC output circuit is provided with a corresponding current sampling point, and each current sampling circuit is connected to each current sampling point in a corresponding LLC conversion circuit.

[0009] Optionally, the current sampling circuit comprises:

[0010] a current transformer connected with the corresponding one of the LLC conversion circuits, configured to generate a current induction signal according to a loop current of the corresponding one of the LLC conversion circuits;

[0011] a rectification unit connected with the current transformer, configured to rectify the current induction signal to obtain a direct current signal; and

[0012] a conversion unit connected with the rectification unit, configured to convert the direct current signal to a direct voltage signal;

[0013] a filtering unit connected with the conversion unit and the control circuit respectively, configured to filter the direct current signal to obtain the current sampling signal.

[0014] Optionally, the current transformer comprises a primary winding and a secondary winding coupled with each other, and the primary winding is connected with the corresponding one of the LLC conversion circuits.

[0015] The rectification unit comprises a first diode, a second diode, a third diode and a fourth diode, a positive electrode of the first diode is connected with one end of the secondary winding, a negative electrode of the first diode is connected with a positive input end of the filtering unit, a positive electrode of the second diode is connected with a negative input end of the filtering unit, a negative electrode of the second diode is connected with a positive electrode of the first diode, a positive electrode of the third diode is connected with the other end of the secondary winding, a negative electrode of the third diode is connected with the positive input end of the filtering unit, a positive electrode of the fourth diode is connected with the negative input end of the filtering unit, and a negative electrode of the fourth diode is connected with a positive electrode of the third diode.

[0016] Optionally, the conversion unit comprises a first resistor, one end of the first resistor is connected with a positive output end of the rectification unit, and the other end of the first resistor is connected with a negative output end of the rectification unit.

[0017] The filtering unit comprises a second resistor, a first capacitor and a second capacitor, one end of the first capacitor is connected with one end of the first resistor and one end of the second resistor respectively, the other end of the first capacitor is connected with the other end of the first resistor, one end of the second capacitor is connected with the other end of the second resistor and a positive input end of the control circuit respectively, and the other end of the second capacitor is connected with the other end of the first capacitor and a negative input end of the control circuit respectively.

[0018] Optionally, the current sampling circuit comprises:

[0019] a sampling resistor, disposed in a loop of the LLC conversion circuit; and

[0020] a signal processing unit, electrically connected with the sampling resistor and the control circuit respectively, configured to acquire an electrical parameter of the sampling resistor, obtain the current sampling signal according to the electrical parameter of the sampling resistor, and output to the control circuit after amplification and filtering processing.

[0021] Optionally, the signal processing unit comprises a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a third capacitor, a fourth capacitor, a first amplifier and a second amplifier.

[0022] One end of the third resistor is connected to one end of the sampling resistor, the other end of the third resistor is connected to one end of the third capacitor, one end of the fourth resistor is connected to the other end of the sampling resistor, the other end of the fourth resistor is connected to the other end of the third capacitor, the non-inverting input terminal of the first amplifier is connected to one end of the third capacitor, the inverting input terminal of the first amplifier is connected to the other end of the third capacitor, the non-inverting output terminal of the first amplifier is connected to one end of the fifth resistor, the inverting output terminal of the first amplifier is connected to one end of the sixth resistor, the other end of the fifth resistor is connected to one end of the fourth capacitor and one end of the seventh resistor respectively, the other end of the sixth resistor is connected to the other end of the fourth capacitor and one end of the eighth resistor respectively, the other end of the seventh resistor is connected to the non-inverting input terminal of the second amplifier, the other end of the eighth resistor is connected to the inverting input terminal of the second amplifier, one end of the ninth resistor is connected to a power supply, the other end of the ninth resistor is connected to the non-inverting input terminal of the second amplifier, the output terminal of the second amplifier is connected to one end of the tenth resistor, the other end of the tenth resistor is connected to the control circuit, one end of the eleventh resistor is connected to the inverting input terminal of the second amplifier, and the other end of the eleventh resistor is connected to the output terminal of the second amplifier.

[0023] Optionally, the current sampling circuit comprises a Hall sensor, electrically connected with the control circuit, a sensing end of the Hall sensor is connected to the loop of the LLC conversion circuit, and the Hall sensor is configured to sense the loop current of the LLC conversion circuit and generate the current sampling signal.

[0024] Optionally, the control circuit comprises a chip, electrically connected with the current sampling circuit, and the chip is one of a digital processing chip, a microcontroller chip and a field programmable logic array chip.

[0025] In a second aspect, the embodiments of the present application provide a charging device comprising the LLC resonant converter as described in any one of the preceding embodiments.

[0026] The embodiments of the present application can achieve the following technical effects: The LLC resonant converter of the embodiments of the present application obtains the loop current of each LLC conversion circuit by the current sampling circuit, and compares the loop current of each LLC conversion circuit by the control circuit, adjusts the frequency and / or duty cycle of the switch control signal according to the comparison result, and keeps the output current of each LLC conversion circuit balanced. BRIEF DESCRIPTION OF DRAWINGS

[0027] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are schematic and not intended to be limiting of the present application, and in which like reference numerals refer to like elements in the various figures of the drawings, in which:

[0028] Figure 1 A circuit structure schematic diagram of an LLC resonant converter provided by the embodiments of the present application;

[0029] Figure 2 A structure schematic diagram of a multi-path LLC conversion circuit of an LLC resonant converter provided by the embodiments of the present application;

[0030] Figure 3 A structure schematic diagram of a two-path LLC conversion circuit of the prior art;

[0031] Figure 4 A first structure schematic diagram of a current sampling circuit of an LLC resonant converter provided by the embodiments of the present application;

[0032] Figure 5 A second structure schematic diagram of a current sampling circuit of an LLC resonant converter provided by the embodiments of the present application. DETAILED DESCRIPTION

[0033] For the convenience of understanding the utility model, the utility model is explained in more detail below in combination with the drawings and specific embodiments. It should be noted that when an element is described as being "connected" to another element, it can be directly on the other element or one or more intervening elements can be present therebetween. The terms "upper", "lower", "left", "right", "upper end", "lower end", "top" and "bottom" and the like used in the specification indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the utility model. In addition, the terms "first", "second" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0034] Unless otherwise defined, all technical and scientific terms used in the specification have the same meaning as commonly understood by one of ordinary skill in the art to which the utility model belongs. The terms used in the specification of the utility model are only for the purpose of describing specific embodiments and are not used to limit the utility model.

[0035] Please refer to Figure 1 In the first aspect, the embodiments of the application provide an LLC resonant converter 100, comprising at least two LLC conversion circuits 10 connected in parallel, at least two current sampling circuits 30 and a control circuit 20.

[0036] Among them, LLC resonant conversion DC-DC (direct current-direct current) conversion power topology, using resonant conversion to realize direct current-direct current conversion, LLC is the abbreviation of Lr, Lm and Cr, wherein Lr is the resonant inductance, Lm is the excitation inductance, and Cr is the resonant capacitance.

[0037] In some embodiments, the LLC conversion circuit 10 comprises a switching circuit 11, which is used to convert the input direct current signal into an alternating current signal according to a switching control signal. Each current sampling circuit 30 is connected to a corresponding LLC conversion circuit 10, and the current sampling circuit 30 is used to sample the loop current of the corresponding LLC conversion circuit 10 and generate a current sampling signal. The control circuit 20 is connected to each sampling circuit and each switching circuit 11, and the control circuit 20 is used to generate a switching control signal corresponding to each LLC conversion circuit 10, and adjust the frequency and / or duty cycle of each switching control signal by comparing each current sampling signal in real time, so that the output currents of each LLC conversion circuit 10 remain consistent.

[0038] The working principle of the LLC resonant converter 100 in the embodiment of the present application is as follows: at least two LLC conversion circuits 10 are connected in parallel with each other, each LLC conversion circuit 10 is configured with a current sampling circuit 30 for sampling current, and each current sampling circuit 30 sends a current sampling signal for representing the loop current size of the LLC conversion circuit 10 to the control circuit 20. The control circuit 20 is configured to control the switching circuit 11 of each LLC conversion circuit 10 to control the power output of each LLC conversion circuit 10. Further, the control circuit 20 adjusts the frequency and / or duty cycle of each switching control signal by comparing the current sampling signals of each current sampling circuit 30 in real time to control the loop current size of each LLC conversion circuit 10, so that the output currents of each LLC conversion circuit 10 are kept balanced.

[0039] It can be understood that the LLC resonant converter 100 in the embodiment of the present application acquires the loop current size of each LLC conversion circuit 10 by the current sampling circuit 30, and compares the loop current size of each LLC conversion circuit 10 by the control circuit 20, adjusts the frequency and / or duty cycle of each switching control signal according to the comparison result, and makes the output currents of each LLC conversion circuit 10 balanced.

[0040] In some embodiments, the control circuit 20 can include at least one chip or integrated circuit, which is provided with a logic unit in the chip or integrated circuit, and is capable of comparing the collected current sampling signals. The chip or integrated circuit is also provided with a processing unit, which is capable of analyzing at least the comparison result of the logic unit to adjust the frequency and / or duty cycle of the switching control signal. In one embodiment, the control circuit 20 determines the current size of each LLC conversion circuit by the acquired multi-channel current sampling signals, calculates the average current, compares the current of each LLC conversion circuit 10 with the average current, and outputs the corresponding switching control signal, so that the current of any LLC conversion circuit 10 with a current greater than the average current is reduced to the average current, and the current of any LLC conversion circuit with a current less than the average current is increased to the average current. In another embodiment, the control circuit 20 determines a current reference value by the power output requirement of the LLC resonant converter 100, which can be the average current size determined according to the power output requirement. The control circuit 20 compares the current of each LLC conversion circuit 10 with the current reference value, and outputs the corresponding switching control signal, so that the current of any LLC conversion circuit 10 with a current greater than the current reference value is reduced to the current reference value, and the current of any LLC conversion circuit 10 with a current less than the current reference value is increased to the current reference value. In other embodiments, the current comparison and analysis of each LLC conversion circuit 10 can be set according to actual requirements, which is not limited here.

[0041] In some embodiments, the control circuit 20 can employ a control algorithm such as PID control, fuzzy control or linear control to generate and adjust the switching control signals. The specific structure of the control circuit 20 can be set according to actual needs, which is not limited here.

[0042] Exemplarily, the topology of the LLC conversion circuit 10 of the embodiments of the present application can refer to the circuit topology shown in Figure 2 Figure 2 The circuit topology shown includes n (n≥2) three-phase LLC conversion circuits 10. The connection mode of any one of the primary side and the secondary side of each three-phase LLC conversion circuit 10 can adopt a delta connection or a star connection. Taking the Nth three-phase LLC conversion circuit 10 with both the primary side and the secondary side adopting a star connection as an example, the switching tubes Qn-1 to Qn-6 constitute the switching circuit 11 of the three-phase LLC conversion circuit 10, which is responsible for converting the input DC voltage into a high-frequency three-phase AC signal.

[0043] Qn-1 and Qn-2 constitute the A-phase bridge arm of the Nth three-phase LLC resonant circuit, and the A-phase bridge arm midpoint An, the capacitor Crn-A, the inductor Lrn-A and the 1-2 winding of the transformer Tn constitute the Nth A-phase primary side resonant cavity circuit 12. Qn-3 and Qn-4 constitute the B-phase bridge arm of the Nth three-phase LLC resonant circuit, and the B-phase bridge arm midpoint Bn, the capacitor Crn-B, the inductor Lrn-B and the 3-4 winding of the transformer Tn constitute the Nth B-phase primary side resonant cavity circuit 12. Qn-5 and Qn-6 constitute the C-phase bridge arm of the Nth three-phase LLC resonant circuit, and the C-phase bridge arm midpoint, the capacitor Crn-C, the inductor Lrn-C and the 5-6 winding of the transformer Tn constitute the Nth C-phase primary side resonant cavity circuit 12.

[0044] Dn-1 to Dn-6 constitute the secondary side power diodes (or power switching tubes) of the Nth three-phase LLC resonant circuit, which are responsible for rectifying the three-phase AC signal generated on the secondary side into a DC output, i.e. the DC output circuit 14 of the three-phase LLC resonant circuit.

[0045] Dn-1 and Dn-2 constitute the a-phase bridge arm of the Nth three-phase LLC resonant circuit, and the loop from the a-phase bridge arm midpoint an to the 7-8 winding of the transformer Tn constitutes the Nth a-phase secondary side resonant loop. Dn-3 and Dn-4 constitute the b-phase bridge arm of the Nth three-phase LLC resonant circuit, and the loop from the b-phase bridge arm midpoint bn to the 9-10 winding of the transformer Tn constitutes the Nth b-phase secondary side resonant loop. Dn-5 and Dn-6 constitute the c-phase bridge arm of the Nth three-phase LLC resonant circuit, and the loop from the c-phase bridge arm midpoint cn to the 11-12 winding of the transformer Tn constitutes the Nth c-phase secondary side resonant loop.

[0046] Please refer to Figure 3 ​The conventional technical solution of the LLC resonant converter 100 in the prior art adopts the transformer winding mutual cross connection between different LLC conversion circuits 10 for current sharing. Specifically, between each parallel LLC conversion circuit 10, at least one winding of the transformer needs to be used through mutual cross connection. Taking two parallel LLC conversion circuits as an example, the topology of the LLC conversion circuit 10 of the first path needs to connect at least one phase bridge arm output to the transformer of the second path, and the topology of the LLC conversion circuit 10 of the second path also needs to connect at least one bridge arm output to the transformer of the first path, so as to achieve the effect of current sharing through the cross use of the transformer winding.

[0047] However, due to the mutual cross of the multiple LLC conversion circuits 10 and the mutual influence of the working states, the complexity of the whole system is high, and the system analysis is difficult. Further, the output current sharing of each LLC conversion circuit 10 is realized by pure hardware, and the current size in the resonant cavity of each LLC conversion circuit 10 is not monitored, so that the winding overcurrent cannot be protected in time in the case of LLC resonant converter 100 circuit abnormality, and the components of the circuit are damaged.

[0048] Compared with the conventional LLC resonant converter 100, the LLC resonant converter 100 of the embodiment adopts multiple parallel LLC conversion circuits 10, and there is no cross coupling in the remaining main power loop except for the parallel connection of the input end and the output end. The system structure is simple; each LLC conversion circuit 10 can be controlled independently, and the control freedom is high. Further, each LLC conversion circuit 10 only needs one current sampling circuit 30 to realize the current sharing control of the multiple parallel LLC resonant conversion circuits, the system is simple, the cost is low, and each LLC conversion circuit 10 can be controlled independently, so the current sharing control effect is good.

[0049] Please refer to Figure 2 In some embodiments, the LLC conversion circuit 10 further includes a primary side resonant cavity circuit 12, a secondary side resonant cavity circuit 13, and a direct current output circuit 14. The switching circuit 11 is electrically connected with the primary side resonant cavity circuit 12. The primary side resonant cavity circuit 12 is coupled with the secondary side resonant cavity circuit 13. The secondary side resonant cavity circuit 13 is electrically connected with the direct current output circuit 14. At least one of the primary side resonant cavity circuit 12, the secondary side resonant cavity circuit 13, and the direct current output circuit 14 is provided with a corresponding current sampling point. Each current sampling circuit 30 is connected with each current sampling point in a corresponding LLC conversion circuit 10.

[0050] It can be understood that in the embodiments of the present application, the current sampling point of each LLC conversion circuit 10 can be at least one of the primary side resonant cavity circuit 12, the secondary side resonant cavity circuit 13 and the direct current output circuit 14, so as to obtain the actual current of each LLC conversion circuit 10. The current value obtained by the current sampling point at any position can be converted by a formula to obtain the final current sampling signal. In the same LLC conversion circuit 10, multiple current sampling points are arranged, which is conducive to the flexible conversion of the specific structure of the circuit, and is also conducive to obtaining multiple sampling information to verify the accuracy of the sampling result. The control circuit 20 can compare the current sampling signals of at least one current sampling point between the LLC resonant circuits through the current sampling circuits 30 of each LLC resonant circuit, and adjust the frequency and / or duty cycle of the switching control signal of the switching circuit 11 of each LLC resonant circuit, so as to realize the output current balance of each LLC resonant circuit.

[0051] Please refer to Figure 4 In some embodiments, the current sampling circuit 30 includes a current transformer CT, a rectifying unit 31, a converting unit 32 and a filtering unit 33.

[0052] The current transformer CT is electrically connected with the corresponding LLC conversion circuit 10, and is used to generate a current induction signal according to the loop current of the corresponding LLC conversion circuit 10. The rectifying unit 31 is electrically connected with the current transformer CT, and is used to obtain a direct current signal (specifically, a pulsating direct current signal) after rectifying the current induction signal. The converting unit 32 is electrically connected with the rectifying unit 31, and is used to convert the direct current signal into a direct voltage signal (specifically, a pulsating direct voltage signal). The filtering unit 33 is respectively electrically connected with the rectifying unit 31 and the control circuit 20, and is used to obtain the current sampling signal after filtering the direct voltage signal.

[0053] It can be understood that in the embodiments of the present application, the current transformer CT is used to convert the loop current in the LLC conversion circuit 10 into a current signal (i.e. a current induction signal) which is convenient to measure. After rectifying the current induction signal, a direct current signal is obtained. After conversion, a direct voltage signal is obtained, so as to facilitate subsequent filtering and smoothing processing. After the filtering unit 33 performs filtering and smoothing processing on the direct voltage signal, the current sampling signal is obtained and output to the control circuit 20.

[0054] In some embodiments, the current transformer CT includes a primary winding and a secondary winding which are coupled to each other, and the primary winding is connected with the corresponding LLC conversion circuit 10. Specifically, taking the first three-phase LLC conversion circuit 10 as an example, the winding between the 1 and 2 pins of the CT is connected into the required current sampling network, for example Figure 2 As shown in the current sampling point CT1, I_sample+ and I_sample- are sampling signals, and are connected to the control circuit 20.

[0055] The rectifying unit 31 includes a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4. The positive pole of the first diode D1 is connected to one end of the secondary winding, the negative pole of the first diode D1 is connected to the positive input end of the filtering unit 33, the positive pole of the second diode D2 is connected to the negative input end of the filtering unit 33, the negative pole of the second diode D2 is connected to the positive pole of the first diode D1, the positive pole of the third diode D3 is connected to the other end of the secondary winding, the negative pole of the third diode D3 is connected to the positive input end of the filtering unit 33, the positive pole of the fourth diode D4 is connected to the negative input end of the filtering unit 33, and the negative pole of the fourth diode D4 is connected to the positive pole of the third diode D3.

[0056] It can be understood that the current transformer CT is used to induce the loop current in the LLC resonant current and convert it into the induced current of the secondary winding. The function of the current transformer CT is to convert the high current into a lower current for measurement and processing. The rectifying bridge composed of the first diode D1 to the fourth diode D4 converts the alternating current output by the current transformer CT into direct current, and the current output after rectification is unidirectional direct current, which is beneficial to subsequent conversion and filtering processing.

[0057] Please continue to refer to Figure 4 In some embodiments, the converting unit 32 includes a first resistor R1, and the filtering unit 33 includes a second resistor R2, a first capacitor C1 and a second capacitor C2. One end of the first resistor R1 is connected to the positive output end of the rectifying unit 31, the other end of the first resistor R1 is connected to the negative output end of the rectifying unit 31, one end of the first capacitor C1 is connected to one end of the first resistor R1 and one end of the second resistor R2 respectively, the other end of the first capacitor C1 is connected to the other end of the first resistor R1, one end of the second capacitor C2 is connected to the other end of the second resistor R2 and the positive input end of the control circuit 20 respectively, and the other end of the second capacitor C2 is connected to the other end of the first capacitor C1 and the negative input end of the control circuit 20 respectively.

[0058] It can be understood that the converting unit 32 converts the direct current signal into a direct voltage signal through the first resistor R1. In the filtering unit 33, the direct voltage signal is filtered and smoothed by the RC filtering network composed of the second resistor R2, the first capacitor C1 and the second capacitor C2, to output a smooth current sampling signal.

[0059] Specifically, one end of the first resistor R1 is connected to the negative pole of the third diode D3, and the other end of the first resistor R1 is connected to the positive pole of the fourth diode D4.

[0060] Please refer to Figure 5In some embodiments, the current sampling circuit 30 comprises a sampling resistor Rshunt and a signal processing unit 34. The sampling resistor Rshunt is arranged in the loop of the LLC conversion circuit 10. The signal processing unit 34 is electrically connected to the sampling resistor Rshunt and the control circuit 20 respectively, for obtaining an electrical parameter of the sampling resistor Rshunt, obtaining a current sampling signal according to the electrical parameter of the sampling resistor Rshunt, and outputting the current sampling signal to the control circuit 20 after amplification and filtering. It can be understood that the signal processing unit 34 obtains an electrical signal of the sampling resistor Rshunt, obtains a current sampling signal according to the electrical signal of the sampling resistor Rshunt, and outputs the current sampling signal to the control circuit 20 after amplification and filtering. The electrical parameter obtained by the signal processing unit 34 can be a current parameter or a voltage parameter. For example, the signal processing unit 34 collects the voltage across the sampling resistor Rshunt, and converts the voltage into a current sampling signal I_sample to the control circuit 20 after processing. In the embodiments of the present application, the sampling resistor Rshunt and the signal processing unit 34 are combined, so that the current flowing through the sampling resistor Rshunt can be converted into a voltage signal that is easy to detect, and the function of current sampling is realized.

[0061] Optionally, the signal processing unit 34 comprises a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a third capacitor C3, a fourth capacitor C4, a first amplifier U1, and a second amplifier U2.

[0062] One end of the third resistor R3 is connected to one end of the sampling resistor Rshunt, the other end of the third resistor R3 is connected to one end of the third capacitor C3, one end of the fourth resistor R4 is connected to the other end of the sampling resistor Rshunt, the other end of the fourth resistor R4 is connected to the other end of the third capacitor C3, the non-inverting input terminal of the first amplifier U1 is connected to one end of the third capacitor C3, the inverting input terminal of the first amplifier U1 is connected to the other end of the third capacitor C3, one end of the fifth resistor R5 is connected to the non-inverting output terminal of the first amplifier U1, one end of the sixth resistor R6 is connected to the inverting output terminal of the first amplifier U1, the other end of the fifth resistor R5 is connected to one end of the fourth capacitor C4 and one end of the seventh resistor R7 respectively, the other end of the sixth resistor R6 is connected to the other end of the fourth capacitor C4 and one end of the eighth resistor R8 respectively, the other end of the seventh resistor R7 is connected to the non-inverting input terminal of the second amplifier U2, the other end of the eighth resistor R8 is connected to the inverting input terminal of the second amplifier U2, one end of the ninth resistor R9 is connected to the power supply, the other end of the ninth resistor R9 is connected to the non-inverting input terminal of the second amplifier U2, the output terminal of the second amplifier U2 is connected to one end of the tenth resistor R10, the other end of the tenth resistor R10 is connected to the control circuit 20, one end of the eleventh resistor R11 is connected to the inverting input terminal of the second amplifier U2, the other end of the eleventh resistor R11 is connected to the output terminal of the second amplifier U2.

[0063] It can be understood that the third resistor R3 and the fourth resistor R4 form a resistor voltage dividing network, and the voltage across the sampling resistor Rshunt is input to the non-inverting input terminal and the inverting input terminal of the first amplifier U1 respectively. The first amplifier U1 is used to amplify the voltage signal generated by the current flowing through the sampling resistor Rshunt, and the third capacitor C3 and the fourth capacitor C4 are used for filtering processing of the input terminal and the output terminal of the first amplifier U1 respectively, to eliminate noise and interference. The fifth resistor R5 to the ninth resistor R9 together constitute an impedance matching network of the input terminal of the second amplifier U2, which is used to control the gain of the second amplifier U2, and the eleventh resistor R11 constitutes a negative feedback loop of the second amplifier U2. The tenth resistor R10 is the output terminal resistance of the second amplifier U2, and the output signal of the second amplifier U2 is output to the control circuit 20 after being divided.

[0064] Specifically, the voltage signal of the sampling resistor Rshunt is sequentially subjected to signal amplification by the first amplifier U1 and the second amplifier U2 and filtering by the peripheral filter circuit, and then a current sampling signal is output to the control circuit 20, which is conducive to ensuring the signal quality and signal stability of the current sampling signal. Exemplarily, the first amplifier U1 is an isolation operational amplifier, and the second amplifier U2 is a commonly used operational amplifier. In other embodiments, the specific circuit structure of the signal processing unit 34 can be set according to actual needs, which is not limited here.

[0065] In some embodiments, the current sampling circuit comprises a Hall sensor, the Hall sensor is electrically connected with the control circuit 20, a sensing end of the Hall sensor is connected to the loop of the LLC conversion circuit 10, and the Hall sensor is used to sense the loop current of the LLC conversion circuit 10 and generate a current sampling signal.

[0066] It can be understood that, as a current sampling device, the sensing end of the Hall sensor can sense the current in the LLC conversion circuit 10 and output a corresponding voltage signal (i.e. a current sampling signal), and the current size of the LLC conversion circuit can be obtained by the voltage signal.

[0067] In some embodiments, the control circuit comprises a chip, the chip is electrically connected with the current sampling circuit, and the chip is one of a digital signal processing chip, a microcontroller chip and a field programmable logic array chip.

[0068] In some embodiments, the control circuit can be built by two or more chips, and each chip can work in coordination with each other. For example, the control circuit can also be built by various logic devices, such as a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a single-chip microcomputer, an ARM (Acorn RISC Machine) or other programmable logic devices, discrete gates or transistor logic, discrete hardware components or any combination of these components.

[0069] In a second aspect, the embodiments of the present application provide a charging device comprising the LLC resonant converter of the above embodiments. Exemplarily, the charging device can be a charging pile host.

[0070] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above. In order to be brief, they are not provided in details; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An LLC resonant converter, characterized by, The application relates to a current sampling method and device for LLC converter. The application comprises: at least two parallel LLC converter circuits, wherein a switching circuit is arranged in the LLC converter circuit, and the switching circuit is used to convert an input direct current signal into an alternating current signal according to a switching control signal; at least two current sampling circuits, wherein each current sampling circuit is connected to a corresponding LLC converter circuit, and the current sampling circuit is used to sample a loop current of the corresponding LLC converter circuit and generate a current sampling signal; and a control circuit, wherein the control circuit is connected to each current sampling circuit and each switching circuit, and the control circuit is used to generate the switching control signal corresponding to each LLC converter circuit, and by comparing each current sampling signal in real time, the frequency and / or duty cycle of the switching control signal is adjusted to keep the output current of each LLC converter circuit consistent. The LLC converter circuit further comprises a primary side resonant cavity circuit, a secondary side resonant cavity circuit and a direct current output circuit, the switching circuit is electrically connected to the primary side resonant cavity circuit, the primary side resonant cavity circuit is coupled to the secondary side resonant cavity circuit, the secondary side resonant cavity circuit is electrically connected to the direct current output circuit, and at least one of the primary side resonant cavity circuit, the secondary side resonant cavity circuit and the direct current output circuit is provided with a corresponding current sampling point, and each current sampling circuit is connected to each current sampling point in the corresponding LLC converter circuit.

2. The LLC resonant converter of claim 1, wherein, The current sampling circuit comprises:

3. The LLC resonant converter of claim 1, wherein, a current transformer, which is connected to the corresponding LLC converter circuit and used to generate a current induction signal according to the loop current of the corresponding LLC converter circuit; a rectifying unit, which is electrically connected to the current transformer and used to rectify the current induction signal to obtain a direct current signal; and a converting unit, which is electrically connected to the rectifying unit and used to convert the direct current signal into a direct current voltage signal; a filtering unit, which is electrically connected to the converting unit and the control circuit and used to filter the direct current voltage signal to obtain the current sampling signal. The current transformer comprises a primary winding and a secondary winding which are coupled to each other, and the primary winding is connected to the corresponding LLC converter circuit; 4. The LLC resonant converter of claim 3, wherein, the rectifying unit comprises a first diode, a second diode, a third diode and a fourth diode, wherein one end of the secondary winding is connected to the positive electrode of the first diode, the negative electrode of the first diode is connected to the positive input end of the filtering unit, the positive electrode of the second diode is connected to the negative input end of the filtering unit, the negative electrode of the second diode is connected to the positive electrode of the first diode, the other end of the secondary winding is connected to the positive electrode of the third diode, the negative electrode of the third diode is connected to the positive input end of the filtering unit, the positive electrode of the fourth diode is connected to the negative input end of the filtering unit, and the negative electrode of the fourth diode is connected to the positive electrode of the third diode. ​ 5. The LLC resonant converter of claim 3, wherein, The converting unit comprises a first resistor, one end of the first resistor is connected to the positive output end of the rectifying unit, and the other end of the first resistor is connected to the negative output end of the rectifying unit. The filtering unit comprises a second resistor, a first capacitor and a second capacitor, one end of the first capacitor is connected to one end of the first resistor and one end of the second resistor respectively, the other end of the first capacitor is connected to the other end of the first resistor, one end of the second capacitor is connected to the other end of the second resistor and the positive input end of the control circuit respectively, and the other end of the second capacitor is connected to the other end of the first capacitor and the negative input end of the control circuit respectively.

6. The LLC resonant converter of claim 1, wherein, The current sampling circuit comprises: a sampling resistor arranged in the loop of the LLC conversion circuit; and a signal processing unit electrically connected to the sampling resistor and the control circuit, configured to obtain an electrical parameter of the sampling resistor, obtain the current sampling signal according to the electrical parameter of the sampling resistor, and output the current sampling signal to the control circuit after amplification and filtering.

7. The LLC resonant converter of claim 6, wherein, The signal processing unit comprises a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a third capacitor, a fourth capacitor, a first amplifier and a second amplifier. One end of the third resistor is connected to one end of the sampling resistor, the other end of the third resistor is connected to one end of the third capacitor, one end of the fourth resistor is connected to the other end of the sampling resistor, the other end of the fourth resistor is connected to the other end of the third capacitor, the non-inverting input end of the first amplifier is connected to one end of the third capacitor, the inverting input end of the first amplifier is connected to the other end of the third capacitor, the non-inverting output end of the first amplifier is connected to one end of the fifth resistor, the inverting output end of the first amplifier is connected to one end of the sixth resistor, the other end of the fifth resistor is connected to one end of the fourth capacitor and one end of the seventh resistor respectively, the other end of the sixth resistor is connected to the other end of the fourth capacitor and one end of the eighth resistor respectively, the other end of the seventh resistor is connected to the non-inverting input end of the second amplifier, the other end of the eighth resistor is connected to the inverting input end of the second amplifier, one end of the ninth resistor is connected to a power supply, the other end of the ninth resistor is connected to the non-inverting input end of the second amplifier, the output end of the second amplifier is connected to one end of the tenth resistor, the other end of the tenth resistor is connected to the control circuit, one end of the eleventh resistor is connected to the inverting input end of the second amplifier, and the other end of the eleventh resistor is connected to the output end of the second amplifier.

8. The LLC resonant converter of claim 1, wherein, The current sampling circuit comprises a Hall sensor, the Hall sensor is electrically connected to the control circuit, a sensing end of the Hall sensor is connected to the loop of the LLC conversion circuit, and the Hall sensor is configured to sense the loop current of the LLC conversion circuit and generate the current sampling signal.

9. The LLC resonant converter of claim 1, wherein, The control circuit comprises a chip, the chip is electrically connected with the current sampling circuit, and the chip is one of a digital processing chip, a microcontroller chip and a field programmable logic array chip.

10. A charging device, characterized by An LLC resonant converter as claimed in any of claims 1 to 9.

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