Output current detection device for DC / AC converter and DC / AC converter

Abstract

The invention provides an output current detection device of a DC / AC converter and the DC / AC converter, and the device comprises a signal sampling unit which is connected with a transformer and is used for converting a current signal flowing through the transformer into a voltage signal representing the output current of the DC / AC converter according to the working state of a switching tube in a secondary bridge arm; and the low-pass filtering unit is used for filtering the voltage signal output by the signal sampling unit to obtain a sampling signal of the output current of the DC / AC converter. According to the invention, a Hall sensor at the AC side of the DC / AC converter is omitted, the production cost of a product is reduced, and the size of the product is reduced.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to an output current detection device of a DC / AC converter and a DC / AC converter. Background Art

[0002] The DC / AC converter converts the direct current generated by the photovoltaic module into alternating current, which can power household electrical appliances or the power grid.

[0003] In order to achieve energy management, it is usually necessary to detect the output current of the DC / AC converter. Figure 1 As shown, the DC side input voltage of the DC / AC converter is V in , the AC side output voltage is V ac , the AC side output current is i ac At present, the output current i is generally realized by setting a Hall sensor at the AC port. ac Sampling, due to the large size and high price of the AC side Hall sensor, is not conducive to the cost control and lightweight of the DC / AC converter. Summary of the invention

[0004] Based on this, it is necessary to provide an output current detection device of a DC / AC converter and a DC / AC converter to address the above technical problems.

[0005] In a first aspect, an embodiment of the present invention provides an output current detection device for a DC / AC converter, wherein the DC / AC converter includes a primary bridge arm, a secondary bridge arm, and a transformer connected between the primary bridge arm and the secondary bridge arm, and the device includes:

[0006] A signal sampling unit connected to the transformer, and used to convert the current signal flowing through the transformer into a voltage signal representing the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm;

[0007] A low-pass filtering unit is used to filter the voltage signal output by the signal sampling unit to obtain a sampling signal of the output current of the DC / AC converter.

[0008] In some embodiments, the signal sampling unit includes:

[0009] The sampling resistor network includes at least one sampling resistor, which is used to convert the current signal flowing through the transformer into a voltage signal representing the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm.

[0010] In some embodiments, the signal sampling unit further includes:

[0011] A current transformer is connected to the transformer and the sampling resistor network, and is used to collect the current signal flowing through the transformer and provide it to the sampling resistor network.

[0012] In some embodiments, the sampling resistor network includes:

[0013] A sampling circuit, comprising at least one sampling resistor, for converting a current signal into a voltage signal;

[0014] The selection circuit is connected to the sampling circuit and is used to select and output a voltage signal corresponding to the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm.

[0015] In some embodiments, the selection circuit comprises:

[0016] A selection switch connected to the sampling circuit, used to select and output a voltage signal corresponding to the output current of the DC / AC converter;

[0017] The logic circuit includes a logic gate, which is used to control the selection switch according to the working state of the switch tube in the secondary bridge arm.

[0018] In some embodiments, the sampling circuit includes a first sampling resistor and a second sampling resistor, the first sampling resistor is connected to two ends of the current transformer, the first end of the first sampling resistor is connected to the first end of the second sampling resistor, the second end of the first sampling resistor is connected to the second end of the second sampling resistor through the selection switch, and the second end of the second sampling resistor outputs the voltage signal;

[0019] The logic circuit controls the selection switch to be closed or opened to select and output a voltage signal corresponding to the output current of the DC / AC converter.

[0020] In some embodiments, the sampling circuit includes a first sampling resistor, the first sampling resistor is connected to two ends of the current transformer and to a first end and a second end of the selection switch, and a third end of the selection switch outputs the voltage signal;

[0021] The logic circuit selectively outputs a voltage signal corresponding to the output current of the DC / AC converter by controlling the first terminal to be connected to the third terminal or the second terminal to be connected to the third terminal.

[0022] In some embodiments, the sampling circuit includes two first sampling resistors and a second sampling resistor connected in sequence, the first sampling resistor and the second sampling resistor are connected in series to two ends of the current transformer, the common end of the first sampling resistor and the second sampling resistor is connected to the second end of the selection switch, the other ends of the first sampling resistor and the second sampling resistor are respectively connected to the first end and the third end of the selection switch, and the fourth end of the selection switch outputs the voltage signal;

[0023] The logic circuit selects to output a voltage signal corresponding to the output current of the DC / AC converter by controlling the first end and the fourth end, the second end and the fourth end, or the third end and the fourth end of the selection switch to be connected.

[0024] In some embodiments, the sampling resistor network includes a sampling circuit, a selection circuit and a differential amplifier circuit. The sampling circuit includes a first sampling resistor and a second sampling resistor. The first sampling resistor is connected to the transformer and is used to collect the current flowing through the transformer. The differential amplifier circuit is used to amplify the voltage across the first sampling resistor. The selection circuit is connected to the differential amplifier circuit. The selection circuit includes a selection switch and a logic circuit. The selection switch is connected between the output end of the differential amplifier circuit and the first end of the second sampling resistor. The first end of the second sampling resistor provides the electrical signal. The logic circuit includes a logic gate. By controlling the selection switch to be closed or opened, the voltage signal corresponding to the output current of the DC / AC converter is selected and output.

[0025] In some embodiments, the secondary bridge arm includes an upper bridge arm and a lower bridge arm, the connection point of the upper bridge arm and the lower bridge arm is connected to one end of the secondary winding of the transformer, the upper bridge arm and the lower bridge arm respectively include at least two switching tubes connected in reverse series, and when each switching tube in the upper bridge arm is turned on, the logic circuit controls the selection switch to close; otherwise, the logic circuit controls the selection switch to open.

[0026] In some embodiments, the secondary bridge arm includes an upper bridge arm and a lower bridge arm, the connection point of the upper bridge arm and the lower bridge arm is connected to one end of the secondary winding of the transformer, and the upper bridge arm and the lower bridge arm respectively include at least two switch tubes connected in reverse series.

[0027] When each switch tube in the upper bridge arm is turned on, the logic circuit controls the first end and the third end of the selection switch to be connected; otherwise, the logic circuit controls the second end and the third end of the selection switch to be connected.

[0028] In some embodiments, the secondary bridge arm includes a first upper bridge arm, a first lower bridge arm, a second upper bridge arm and a second lower bridge arm, the connection point of the first upper bridge arm and the first lower bridge arm is connected to the first end of the secondary winding of the transformer, the connection point of the second upper bridge arm and the second lower bridge arm is connected to the second end of the secondary winding of the transformer, and the first upper bridge arm, the first lower bridge arm, the second upper bridge arm and the second lower bridge arm respectively include at least two switch tubes connected in reverse series,

[0029] When each switch tube in the first upper bridge arm and the second lower bridge arm is turned on, the logic circuit controls the first end and the fourth end of the selection switch to be connected; when each switch tube in the first lower bridge arm and the second upper bridge arm is turned on, the logic circuit controls the third end and the fourth end of the selection switch to be connected.

[0030] In some embodiments, the low-pass filtering unit comprises a low-pass filtering circuit.

[0031] In a second aspect, an embodiment of the present invention provides a DC / AC converter, wherein the DC / AC converter comprises:

[0032] The primary bridge arm is used for inversion;

[0033] The secondary bridge arm is used for cross-cross transformation;

[0034] A transformer connected between the primary bridge arm and the secondary bridge arm;

[0035] And the output current detection device as described in the first aspect.

[0036] In some embodiments, a resonant circuit is further included which is connected between the transformer and the secondary bridge arm or between the transformer and the primary bridge arm.

[0037] The present application converts the current signal flowing through the transformer into a voltage signal representing the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm through a signal sampling unit, and filters the voltage signal output by the signal sampling unit through a low-pass filter unit to obtain a sampling signal of the output current of the DC / AC converter. The present application eliminates the Hall sensor on the AC side of the DC / AC converter, thereby reducing the production cost and volume of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of an output current sampling method in the related art of this application;

[0039] Figure 2 A schematic diagram of the structure of a DC / AC converter in some embodiments provided in this application;

[0040] Figure 3 A schematic diagram of the structure of a DC / AC converter in some other embodiments provided in the present application;

[0041] Figure 4 A schematic diagram of the structure of an output current detection device in some embodiments provided in this application;

[0042] Figure 5 A schematic diagram of a specific structure of an output current detection device in some embodiments provided in this application;

[0043] Figure 6 A circuit diagram of an output current detection device in a first exemplary embodiment provided in the present application;

[0044] Figure 7 A schematic diagram of key waveforms in the first exemplary embodiment provided in this application;

[0045] Figure 8 A circuit diagram of a low-pass filter unit in some other embodiments provided in the present application;

[0046] Fig. 9 A circuit diagram of a sampling resistor network in some other embodiments provided in the present application;

[0047] Fig.10 A circuit diagram of a sampling resistor network in some other embodiments provided in the present application;

[0048] Fig.11 A circuit diagram of an output current detection device in a second exemplary embodiment provided by the present application;

[0049] Fig.12 A schematic diagram of a specific structure of an output current detection device in some other embodiments provided in the present application;

[0050] Fig.13 This is a circuit diagram of an output current detection device in a third exemplary embodiment provided by the present application. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for ordinary technicians in the field related to the contents disclosed in the present application, some changes such as design, manufacturing or production based on the technical contents disclosed in the present application are only conventional technical means, and should not be understood as insufficient contents disclosed in the present application.

[0052] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0053] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantitative limitation, and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to greater than or equal to two. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, "A and / or B" can represent: A exists alone, A and B exist at the same time, and B exists alone. The terms "first", "second", "third" and the like involved in the present application are merely used to distinguish similar objects and do not represent a specific ordering of the objects.

[0054] Figure 2This is a schematic structural diagram of a DC / AC converter in some embodiments provided in the present application. The DC / AC converter includes a primary bridge arm 101, a secondary bridge arm 102, and a transformer 103 connected between the primary bridge arm 101 and the secondary bridge arm 102.

[0055] The primary bridge arm 101 includes an inverter circuit, which includes at least two switching tubes for inverting direct current into alternating current. The inverter circuit may be a full-bridge circuit or a half-bridge circuit.

[0056] The secondary bridge arm 102 includes, for example, at least one cycloconverter, which includes a plurality of bidirectional switch tubes for AC-AC conversion, wherein each switch tube group includes at least two switch tubes connected in reverse series, and the output end of the secondary bridge arm 102 provides an AC output, for example, to a load or a power grid.

[0057] The secondary bridge arm 102 may be a half-bridge or full-bridge structure.

[0058] In some embodiments, the DC / AC converter may have multiple transformers, and the primary winding of each transformer is correspondingly connected to a primary bridge arm, and the secondary winding is correspondingly connected to the same secondary bridge arm.

[0059] In some embodiments, Figure 3 As shown, the DC / AC converter further includes a resonant circuit 104 connected between the transformer 103 and the secondary bridge arm 102. The primary side of the transformer 103 is connected to the primary bridge arm 101, and the secondary side is connected to the secondary bridge arm 102 through the resonant circuit 104 for buck-boosting.

[0060] The resonant circuit 104 is used to realize soft switching of the switch tube in the DC / AC converter, thereby reducing circuit loss. In some embodiments, the resonant circuit 104 can be arranged between the transformer 103 and the primary bridge arm 101, or can be omitted.

[0061] The resonant circuit 104 may be in various circuit forms such as single L, LC, and CLLC.

[0062] In some embodiments, the DC / AC converter further includes a filter circuit 105 connected to the output end of the secondary bridge arm 102 for filtering.

[0063] In some embodiments, the DC / AC converter further includes a controller, and the controller is used to control the primary bridge arm 101 and the secondary bridge arm 102 to achieve power conversion.

[0064] Based on the above DC / AC converter, the present application proposes an output current detection device 20 of a DC / AC converter, such as Figure 4As shown, the device includes: a signal sampling unit 201, connected to the transformer 103, for converting the current signal flowing through the transformer 103 into a current signal representing the output current i of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm 102. ac low-pass filtering unit 202, for filtering the voltage signal output by the signal sampling unit to obtain a sampling signal of the output current of the DC / AC converter.

[0065] In some embodiments, the working state of the switch tubes in the secondary bridge arm 102 can be determined according to the high and low levels of the driving signals corresponding to the switch tubes.

[0066] Specifically, the working state of the switch tube includes on and off. For example, when the driving signal of the switch tube is at a high level, the working state of the switch tube is on, and when the driving signal of the switch tube is at a low level, the working state of the switch tube is off. The present application is not limited to this.

[0067] According to the embodiment of the present application, the current signal flowing through the transformer 103 is converted into a voltage signal representing the output current of the DC / AC converter by the signal sampling unit 201 according to the working state of the switch tube in the secondary bridge arm 102, and the voltage signal output by the signal sampling unit 201 is filtered by the low-pass filter unit 202 to obtain the sampling signal of the output current of the DC / AC converter. The present application omits the Hall sensor on the AC side of the DC / AC converter, thereby reducing the production cost and volume of the product.

[0068] In some embodiments, Figure 5 As shown, the signal sampling unit 201 includes: a current transformer 2011, connected to the transformer 103 and the sampling resistor network 2012, for collecting the current signal flowing through the transformer 103 and providing it to the sampling resistor network 2012; the sampling resistor network 2012 includes at least one sampling resistor, connected to the transformer 103, and for converting the current signal flowing through the transformer 103 into a voltage signal representing the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm 102.

[0069] The current transformer 2011 is used to obtain the current flowing through the transformer 103, for example, to proportionally reduce the current flowing through the transformer. Since the current flowing through the transformer is a high-frequency current, the current transformer can use a high-permeability core with a small size and a high bandwidth.

[0070] The current transformer 2011 may be an existing current transformer provided for realizing the resonant current overcurrent protection function, that is, a current transformer provided for realizing the resonant current overcurrent protection function may be reused.

[0071] In some embodiments, the primary winding of the current transformer 2011 is connected in series with the secondary winding of the transformer 103, and the collected current flowing through the transformer 103 is the current of the secondary winding, which is also the resonant current.

[0072] In other embodiments, if the resonant circuit 104 is disposed on the primary side of the transformer 103, the current transformer 2011 may also be configured to be connected in series with the primary winding of the transformer 103 to collect the current flowing through the primary winding.

[0073] In at least one embodiment of the present application, the current transformer provided for realizing the resonant current overcurrent protection function is reused, and the output current of the DC / AC converter is detected by simply conditioning the output signal of the current transformer, thereby further reducing the product cost and the product volume.

[0074] In some embodiments, the low-pass filtering unit 202 is implemented by a hardware circuit. For example, the low-pass filtering unit 202 is implemented by a low-pass filtering circuit composed of passive components and the like.

[0075] In some embodiments, the low-pass filtering unit 202 is implemented by a software algorithm. For example, software low-pass filtering can be performed by a controller in a DC / AC converter.

[0076] In some embodiments, the sampling resistor network 2012 includes a sampling circuit, the sampling circuit includes at least one sampling resistor, and is used to convert a current signal into a voltage signal; a selection circuit is connected to the sampling circuit, and is used to select and output a voltage signal corresponding to the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm, so as to obtain a voltage signal representing the output current i of the DC / AC converter. ac voltage signal.

[0077] In some embodiments, the selection circuit includes: a selection switch connected to the sampling circuit, used to select and output a voltage signal corresponding to the output current of the DC / AC converter; a logic circuit, including a logic gate, used to control the selection switch according to the working state of the switch tube in the secondary bridge arm.

[0078] Figure 6 Schematic diagram of a circuit of an output current detection device of a DC / AC converter in a first exemplary embodiment of the present application.

[0079] Among them, the DC side input voltage of the DC / AC converter is V dc , the AC side output voltage is V acThe primary bridge arm 101 adopts an H-bridge structure (full bridge circuit), and the input end of the primary bridge arm 101 is connected in parallel with a capacitor Cin. The primary bridge arm 101 includes a switch tube Q1H, a switch tube Q1L, a switch tube Q2H, and a switch tube Q2L. Specifically, the switch tube Q1H and the switch tube Q1L are connected in series at the input end of the primary bridge arm 101 to form a half bridge arm, and the switch tube Q2H and the switch tube Q2L are connected in series at the input end to form the other half bridge arm. The secondary bridge arm 102 is a half-bridge type cycloconverter, including two groups of switch tubes, each group of switch tubes includes at least two switch tubes connected in reverse series. Specifically, the two groups of switch tubes are connected in series between the two output terminals of the secondary bridge arm 102 to form a half bridge arm. The first group of switch tubes of the secondary bridge arm 102 includes switch tubes Q3 and switch tubes Q4 connected in common source, forming an upper bridge arm; the second group of switch tubes includes switch tubes Q5 and switch tubes Q6 connected in common source, forming a lower upper bridge arm. The connection point of the two groups of switch tubes is the midpoint of the bridge arm. The output end of the secondary bridge arm 102 is connected to the filter circuit 105. The filter circuit 105 includes a capacitor C connected in parallel with the output end of the secondary bridge arm 102. f and an inductor L connected to the first output terminal of the secondary bridge arm 102 f At the same time, the second output terminal of the secondary bridge arm 102 is connected to one end of the secondary winding of the transformer 103, and the other end of the secondary winding of the transformer 103 is connected to the midpoint of the bridge arm of the secondary bridge arm 102 through the resonant circuit 104. The resonant circuit 104 includes an inductor Lf and a capacitor Cf connected in series. The current flowing through the transformer 103 is the resonant current i rs .

[0080] When the DC / AC converter is working normally, the output voltage V ac In the positive half cycle, the switch tubes Q4 and Q6 are controlled to be normally on, and the switch tubes Q3 and Q5 are complementary turned on to perform high-frequency switching. ac In the negative half cycle, the switch tubes Q3 and Q5 are controlled to be normally turned on, and the switch tubes Q4 and Q6 are complementary turned on to perform high-frequency switching.

[0081] The output current detection device includes: a current transformer 2011 connected to the secondary winding of the transformer 103 and the sampling resistor network 2012, and used to collect the current signal i flowing through the transformer. rs The sampling resistor network 2012 is connected to the current transformer 2011 and is used to convert the current signal flowing through the transformer 103 into a voltage signal V representing the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm 102. 1 ; Low-pass filtering unit 202, for the voltage signal V output by the sampling resistor network 2012 1Filtering is performed to obtain the output current i of the DC / AC converter ac The sampling signal V sam .

[0082] Specifically, the primary winding of the current transformer 2011 and the secondary winding of the transformer 103 are connected in series, and the secondary winding of the current transformer 2011 is connected to the sampling resistor network 2012 to provide a collected current signal.

[0083] In the first exemplary embodiment, the sampling circuit includes a first sampling resistor R sam1 and the second sampling resistor R sam2 The first sampling resistor R sam1 Connected to the two ends of the secondary winding of the current transformer 2011, the first sampling resistor R sam1 The first end and the second sampling resistor R sam2 The first end is connected to the bias voltage V bias , the first sampling resistor R sam1 The second end is connected through the selection switch Q sam The second sampling resistor R sam2 The second end of the second sampling resistor R sam2 The second end outputs the voltage signal V 1 .

[0084] Among them, the first sampling resistor R sam1 The second sampling resistor R is used to convert the current signal output by the current transformer 2011 into a voltage signal. sam2 For output bias voltage V bias , generally design the second sampling resistor R sam2 Much larger than the first sampling resistor R sam1 , for example, the second sampling resistor R sam2 The first sampling resistor R sam1 It is Ω level.

[0085] It should be noted that the bias voltage V bias Not necessary, the first sampling resistor R sam1 and the second sampling resistor R sam2 The first end may be directly grounded.

[0086] In the first exemplary embodiment, the logic circuit is an AND gate. The logic circuit controls the selection switch Q sam Close or open, select to output a voltage signal corresponding to the output current of the DC / AC converter, and obtain a voltage signal representing the output current i of the DC / AC converter. ac The voltage signal V 1 .

[0087] Specifically, when the switch tubes (Q3 and Q4) in the upper bridge arm of the secondary bridge arm 102 are turned on, the logic circuit controls the selection switch Q sam Closed; otherwise, the logic circuit controls the selection switch Q sam disconnect.

[0088] Table 1 shows the driving signals (G Q3 and G Q4 ) and the voltage signal V output by the sampling resistor network 1 , where “0” indicates that the driving signal is at a low level and “1” indicates that the driving signal is at a high level.

[0089] Table 1

[0090]

[0091] Figure 7 is the driving signal G of the switch tube Q3 Q3 , the driving signal G of the switch tube Q4 Q4 , select switch Q sam The control signal and resonant current i rs , voltage signal V 1 , sampling signal V sam Waveform diagram of sampling switch Q sam The control signal of the switch tube Q3 is driven by the drive signal G Q3 The driving signal G of the switch tube Q4 Q4 Generated after passing through the AND gate.

[0092] Specifically, in a possible implementation, if and only if the drive signal G of the switch tubes Q3 and Q4 Q3 and G Q4 When both are high level "1", i.e. when switch tubes Q3 and Q4 are turned on, the control selects switch Q sam Closed, otherwise the control selector switch Q sam When the selector switch Q sam When closed, the output voltage signal corresponds to the output current of the DC / AC converter. At this time, the voltage signal V output by the sampling resistor network 2012 is 1 equal n represents the turns ratio of the secondary winding to the primary winding of the current transformer 2011. sam When disconnected, the voltage signal V output by the sampling resistor network 2012 1 Equal to V bias .

[0093] In some embodiments, the low-pass filter unit 202 includes a low-pass filter circuit and a forward proportional amplifier circuit, such as Figure 6As shown, the low-pass filter circuit is a second-order low-pass filter circuit, including a resistor R1, a capacitor C1, a resistor R2 and a capacitor C2; the forward proportional amplifier circuit includes resistors Rf1, Rf2 and an operational amplifier A1. The low-pass filter circuit is used to filter out the voltage signal V 1 The high-frequency component of the forward proportional amplifier circuit is used to amplify the filtered voltage signal V 1 , output sampling signal V sam .

[0094] In some possible implementations, the resistance values ​​R of the resistors R1 and R2 are designed to be 1 =R 2 , the capacitance value of capacitors C1 and C2 is C 1 =C 2 , the resistance values ​​of resistors Rf1 and Rf2 are R f1 , R f2 The input signal of the low-pass filter unit 202 is a voltage signal V 1 , the output signal is the sampling signal V sam , voltage signal V 1 With the sampling signal V sam The transfer function is:

[0095]

[0096] In some other embodiments, the forward proportional amplifier circuit can be omitted, and the low-pass filter circuit can use a first-order RC low-pass filter circuit, such as Figure 8 shown.

[0097] In some embodiments, the sampling signal V sam The analog quantity is converted into a digital quantity by the controller in the DC / AC converter, and the output current i of the DC / AC converter can be obtained. ac .

[0098] In some other embodiments, the switch Q is selected sam A single-pole double-throw switch can be used to omit Figure 6 The second sampling resistor R sam2 At this time, Fig. 9 As shown, the sampling circuit includes a first sampling resistor R sam1 , the first sampling resistor R sam1 Connected to the two ends of the secondary winding of the current transformer 2011 and connected to the selection switch Q sam The first end and the second end are connected, the selection switch Q sam The third end outputs the voltage signal V1.

[0099] When the switch tubes (Q3, Q4) in the upper bridge arm are turned on, the logic circuit controls the selection switch Qsam The first end and the third end are connected; otherwise, the logic circuit controls the selection switch Q sam The second end and the third end are connected.

[0100] In some embodiments, the selection of switch Q5 and Q6 can be determined based on the drive signals of switch tubes Q5 and Q6. sam The control signal, at this time the logic circuit can use the NAND gate, such as Fig.10 As shown, select switch Q sam The control signal is composed of the drive signal G of the switch tubes Q5 and Q6. Q5 , G Q6 Generated after passing through the AND gate.

[0101] Fig.11 Schematic diagram of a circuit of an output current detection device of a DC / AC converter in a second exemplary embodiment of the present application.

[0102] In the second exemplary embodiment, the secondary bridge arm of the DC / AC converter is a full-bridge topology. The secondary bridge arm 102 includes a first upper bridge arm, a first lower bridge arm, a second upper bridge arm and a second lower bridge arm, the connection point of the first upper bridge arm and the first lower bridge arm is connected to the first end of the secondary winding of the transformer 103, and the connection point of the second upper bridge arm and the second lower bridge arm is connected to the second end of the secondary winding of the transformer 103. The first upper bridge arm includes two reverse series connected switch tubes Q31 and Q41; the first lower bridge arm includes two reverse series connected switch tubes Q51 and Q61; the second upper bridge arm includes two reverse series connected switch tubes Q32 and Q42; the second lower bridge arm includes two reverse series connected switch tubes Q52 and Q62.

[0103] The sampling circuit includes two first sampling resistors R connected in sequence. sam1 and the second sampling resistor R sam2 , the first sampling resistor R sam1 and the second sampling resistor R sam2 After being connected in series, the first sampling resistor R sam1 The second sampling resistor R sam2 The common terminal is connected to the bias voltage V bias and the selection switch Q sam The second end of the first sampling resistor R sam1 The second sampling resistor R sam2 The other end is connected to the selection switch Q sam The first and third terminals of the selection switch Q sam The fourth terminal outputs the voltage signal V 1 .

[0104] Selector switch Q sam It is a multiplexer, the fourth end of which is an output end, and the first end, the second end, and the third end are input ends.

[0105] The logic circuit controls the selection switch Q sam The first end and the fourth end are connected, the second end and the fourth end are connected, or the third end and the fourth end are connected, and the output is selected to be the same as the output current i of the DC / AC converter. ac The corresponding voltage signal is finally obtained to characterize the output current i of the DC / AC converter. ac The voltage signal V 1 .

[0106] Specifically, when each switch tube in the first upper bridge arm and the second lower bridge arm is turned on, the logic circuit controls the selection switch Q sam The first end and the fourth end are connected; when each switch tube in the first lower bridge arm and the second upper bridge arm is turned on, the logic circuit controls the selection switch Q sam The third end and the fourth end are connected; in other cases, the logic circuit controls the selection switch Q sam The second end and the fourth end are connected, for example, when each switch tube in the first upper bridge arm and the second upper bridge arm is turned on, or when each switch tube in the first lower bridge arm and the second lower bridge arm is turned on, the selection switch Q is controlled sam The second end and the fourth end are connected.

[0107] In some possible implementations, the connectivity of the selection switches may be controlled according to the driving signals of the switch tubes Q31 , Q41 and the switch tubes Q32 , Q42 .

[0108] Specifically, according to the driving signals (G Q31 , G Q41 , G Q32 , G Q42 ) Determine the selection switch Q according to Table 2 sam The bit number of the sampling resistor is used to sample the voltage on different sampling resistors. Among them, the bit number "1" corresponds to the selection switch Q sam The first end, position "2" corresponds to the selection switch Q sam The second end of the switch, position "3", corresponds to the selection switch Q sam The third end.

[0109] The driving signal of the switch tubes Q31, Q41, Q32, and Q42 is high level "1". When the drive switch tubes Q31, Q41, Q32, and Q42 are turned on, the control selection switch Q sam Connected to bit number "2", the voltage signal V output by the sampling resistor network 2012 is 1 Vbias When the drive signal of the switch tubes Q31 and Q41 is high level "1", the drive switch tubes Q31 and Q41 are turned on, and the drive signal of the switch tubes Q32 and Q42 is low level "0", the drive switch tubes Q32 and Q42 are turned off, that is, the corresponding switch tubes Q31, Q41, Q52, and Q62 are turned on, the control selection switch Q sam Connected to bit number "1", the voltage signal V output by the sampling resistor network 2012 is 1 for When the drive signal of the switch tubes Q31 and Q41 is low level "0", the switch tubes Q31 and Q41 are turned off, and the drive signal of the switch tubes Q32 and Q42 is high level "1", the switch tubes Q32 and Q42 are turned on, that is, the corresponding switch tubes Q32, Q42, Q51, and Q61 are turned on, the control selection switch Q sam Connected to position "3", the voltage signal V output by the sampling resistor network 2012 is 1 for The driving signal of the switch tubes Q31, Q41, Q32, and Q42 is low level "0". When the driving switch tubes Q31, Q41, Q32, and Q42 are turned off, the corresponding switch tubes Q51, Q61, Q52, and Q62 are turned on, and the control selection switch Q sam Connected to bit number "2", the voltage signal V output by the sampling resistor network 2012 is 1 V bias .

[0110] Table 2

[0111]

[0112] The low-pass filter unit 202 samples the voltage signal V output by the resistor network 2012. 1 After low-pass filtering, the output sampling signal V sam , and finally after analog-to-digital conversion, the output current i is obtained ac .

[0113] In some other possible implementations, the connectivity of the selection switches may also be controlled according to the driving signals of the switch tubes Q51 , Q61 and the switch tubes Q52 , Q62 .

[0114] In other embodiments, Fig.12 As shown, the sampling resistor network 2012 directly collects the current signal flowing through the transformer 103 through the sampling resistor and converts it into a voltage signal at the same time, and selects to output a voltage signal representing the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm 102.

[0115] According to the embodiment of the present application, the sampling resistor network 2012 directly collects the current signal flowing through the transformer 103 through the sampling resistor and converts it into a voltage signal at the same time, and selects to output a voltage signal representing the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm 102, and filters the voltage signal output by the sampling resistor network 2012 through the low-pass filter unit 202 to obtain a sampling signal of the output current of the DC / AC converter. It can be applied to different application scenarios, and at the same time, the Hall sensor on the AC side of the DC / AC converter is omitted, which reduces the production cost and volume of the product.

[0116] Fig.13 Schematic diagram of a circuit of an output current detection device of a DC / AC converter in a third exemplary embodiment of the present application.

[0117] In the third exemplary embodiment, the output current detection device omits the current transformer and adds a differential amplifier circuit in the sampling resistor network 2012. Specifically, Fig.12 As shown, the sampling circuit includes a first sampling resistor R sam1 and the second sampling resistor R sam2 , the first sampling resistor R sam1 connected to the transformer 103 and used to collect the current flowing through the transformer 103. The second sampling resistor R sam2 The first end passes through the selection switch Q sam Connected to the output end of the differential amplifier circuit and outputs the voltage signal V 1 , the second sampling resistor R sam2 The second end is connected to the bias voltage V bias The differential amplifier circuit is used to sam1 The voltage signal at both ends is amplified; the logic circuit controls the selection switch Q sam Close or open, select to output a voltage signal V corresponding to the output current of the DC / AC converter 1 .

[0118] Specifically, the first sampling resistor R sam1 It can be a high-precision current sampling resistor, which can be connected in series with the secondary winding of the transformer 103 to sample the current signal and convert it into a voltage signal.

[0119] The differential amplifier circuit is connected to the first sampling resistor R sam1 Specifically, the differential amplifier circuit includes resistors R3, R4, Rp, Rf3 and an operational amplifier A2, one end of the resistor R3 is connected to the first sampling resistor R sam1One end of the resistor R4 is connected to the first sampling resistor R sam1 The other end of the resistor Rp is connected to the non-inverting input terminal of the operational amplifier A2, and the other end is connected to the bias voltage V bias , the two ends of the resistor Rf3 are respectively connected to the inverting input terminal and the output terminal of the operational amplifier A2.

[0120] The selection circuit selects the output current i of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm 102. ac The corresponding voltage signal. Select switch Q sam The control strategy is the same as that of the first exemplary embodiment described above, so it will not be described in detail.

[0121] An embodiment of the present application also proposes a DC / AC converter, which includes: a primary bridge arm for inversion; a secondary bridge arm for AC-AC conversion; a transformer connected between the primary bridge arm and the secondary bridge arm; and an output current detection device as described in the above embodiment.

[0122] In some embodiments, a resonant circuit is further included which is connected between the transformer and the secondary bridge arm or between the transformer and the primary bridge arm.

[0123] In the above embodiments, the output current detection device may be arranged in the DC / AC converter to detect the output current of the DC / AC converter.

[0124] Since the processing and functions implemented by the DC / AC converter of this embodiment correspond to the embodiments, principles and examples of the aforementioned output current detection device, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be given here.

[0125] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0126] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. An output current detection device for a DC / AC converter, the DC / AC converter comprising a primary bridge arm, a secondary bridge arm, and a transformer connected between the primary bridge arm and the secondary bridge arm, characterized in that: The device comprises: A signal sampling unit connected to the transformer, and used to convert the current signal flowing through the transformer into a voltage signal representing the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm; A low-pass filtering unit is used to filter the voltage signal output by the signal sampling unit to obtain a sampling signal of the output current of the DC / AC converter.

2. The device according to claim 1, characterized in that The signal sampling unit comprises: The sampling resistor network includes at least one sampling resistor, which is used to convert the current signal flowing through the transformer into a voltage signal representing the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm.

3. The device according to claim 2, characterized in that The signal sampling unit also includes: A current transformer is connected to the transformer and the sampling resistor network, and is used to collect the current signal flowing through the transformer and provide it to the sampling resistor network.

4. The device according to claim 3, characterized in that The sampling resistor network comprises: A sampling circuit, comprising at least one sampling resistor, for converting a current signal into a voltage signal; The selection circuit is connected to the sampling circuit and is used to select and output a voltage signal corresponding to the output current of the DC / AC converter according to the working state of the switch tube in the secondary bridge arm.

5. The device according to claim 4, characterized in that The selection circuit comprises: A selection switch connected to the sampling circuit, used to select and output a voltage signal corresponding to the output current of the DC / AC converter; The logic circuit includes a logic gate, which is used to control the selection switch according to the working state of the switch tube in the secondary bridge arm.

6. The device according to claim 5, characterized in that The sampling circuit comprises a first sampling resistor and a second sampling resistor, the first sampling resistor is connected to two ends of the current transformer, a first end of the first sampling resistor is connected to a first end of the second sampling resistor, a second end of the first sampling resistor is connected to a second end of the second sampling resistor through the selection switch, and the second end of the second sampling resistor outputs the voltage signal; The logic circuit controls the selection switch to be closed or opened to select and output a voltage signal corresponding to the output current of the DC / AC converter.

7. The device according to claim 5, characterized in that The sampling circuit comprises a first sampling resistor, the first sampling resistor is connected to two ends of the current transformer and to a first end and a second end of the selection switch, and a third end of the selection switch outputs the voltage signal; The logic circuit selectively outputs a voltage signal corresponding to the output current of the DC / AC converter by controlling the first terminal to be connected to the third terminal or the second terminal to be connected to the third terminal.

8. The device according to claim 5, characterized in that The sampling circuit comprises two first sampling resistors and a second sampling resistor connected in sequence, the first sampling resistor and the second sampling resistor are connected in series to two ends of the current transformer, a common end of the first sampling resistor and the second sampling resistor is connected to the second end of the selection switch, the other ends of the first sampling resistor and the second sampling resistor are respectively connected to the first end and the third end of the selection switch, and the fourth end of the selection switch outputs the voltage signal; The logic circuit selects to output a voltage signal corresponding to the output current of the DC / AC converter by controlling the first end and the fourth end, the second end and the fourth end, or the third end and the fourth end of the selection switch to be connected.

9. The device according to claim 2, characterized in that The sampling resistor network includes a sampling circuit, a selection circuit and a differential amplifier circuit. The sampling circuit includes a first sampling resistor and a second sampling resistor. The first sampling resistor is connected to the transformer and is used to collect the current flowing through the transformer. The differential amplifier circuit is used to amplify the voltage across the first sampling resistor. The selection circuit is connected to the differential amplifier circuit. The selection circuit includes a selection switch and a logic circuit. The selection switch is connected between the output end of the differential amplifier circuit and the first end of the second sampling resistor. The first end of the second sampling resistor provides an electrical signal. The logic circuit includes a logic gate. By controlling the selection switch to be closed or opened, the voltage signal corresponding to the output current of the DC / AC converter is selected and output.

10. The device according to claim 6 or 9, characterized in that The secondary bridge arm includes an upper bridge arm and a lower bridge arm, the connection point of the upper bridge arm and the lower bridge arm is connected to one end of the secondary winding of the transformer, the upper bridge arm and the lower bridge arm respectively include at least two switch tubes connected in reverse series, when each switch tube in the upper bridge arm is turned on, the logic circuit controls the selection switch to close; otherwise, the logic circuit controls the selection switch to open.

11. The device according to claim 7, characterized in that The secondary bridge arm comprises an upper bridge arm and a lower bridge arm, the connection point of the upper bridge arm and the lower bridge arm is connected to one end of the secondary winding of the transformer, and the upper bridge arm and the lower bridge arm respectively comprise at least two switch tubes connected in reverse series. When each switch tube in the upper bridge arm is turned on, the logic circuit controls the first end and the third end of the selection switch to be connected; otherwise, the logic circuit controls the second end and the third end of the selection switch to be connected.

12. The device according to claim 8, characterized in that The secondary bridge arm comprises a first upper bridge arm, a first lower bridge arm, a second upper bridge arm and a second lower bridge arm, the connection point of the first upper bridge arm and the first lower bridge arm is connected to the first end of the secondary winding of the transformer, the connection point of the second upper bridge arm and the second lower bridge arm is connected to the second end of the secondary winding of the transformer, and the first upper bridge arm, the first lower bridge arm, the second upper bridge arm and the second lower bridge arm respectively comprise at least two switch tubes connected in reverse series, When each switch tube in the first upper bridge arm and the second lower bridge arm is turned on, the logic circuit controls the first end and the fourth end of the selection switch to be connected; when each switch tube in the first lower bridge arm and the second upper bridge arm is turned on, the logic circuit controls the third end and the fourth end of the selection switch to be connected.

13. The device according to claim 1, characterized in that The low-pass filtering unit includes a low-pass filtering circuit.

14. A DC / AC converter, characterized in that: The DC / AC converter comprises: The primary bridge arm is used for inversion; The secondary bridge arm is used for cross-cross transformation; A transformer connected between the primary bridge arm and the secondary bridge arm; And an output current detection device as described in any one of claims 1 to 13.

15. The DC / AC converter according to claim 14, characterized in that: It also includes a resonant circuit connected between the transformer and the secondary bridge arm or between the transformer and the primary bridge arm.

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