Overcurrent protection circuit

Abstract

The invention discloses an overcurrent protection circuit, which comprises a first synchronous rectification circuit, a second synchronous rectification circuit and a control circuit, and is characterized in that the first synchronous rectification circuit is connected with a primary side of a transformer of an LLC bidirectional direct current conversion circuit and is used for detecting a first signal of the primary side; the second synchronous rectification circuit is connected with the secondary side of the transformer of the LLC bidirectional DC conversion circuit and is used for detecting a second signal of the secondary side; the control circuit is configured to turn off the LLC bidirectional DC conversion circuit when the first signal exceeds a first preset value and / or the second signal exceeds a second preset value. According to the over-current protection circuit provided by the invention, the circuit can be turned off in time when the signal exceeds the preset value, so that over-current protection of the LLC bidirectional direct-current conversion circuit is realized. Besides, as the frequency of the signal generated by the synchronous rectification circuit is usually low, a high-speed and ultra-wideband operational amplifier and a comparator are not needed, the device cost is low, and the cost is saved.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and more specifically, to an overcurrent protection circuit. Background Art

[0002] Bidirectional DC conversion circuits are widely used in distributed power generation systems, DC microgrids, new energy electric vehicles, power electronic transformers and other occasions. In order to prevent the components of the bidirectional DC conversion circuit from being affected by overcurrent, it is necessary to monitor the current of the bidirectional DC conversion circuit and shut down the bidirectional DC conversion circuit in time when overcurrent occurs to achieve overcurrent protection. The current sampling circuit needs to consider factors such as accuracy, withstand voltage, safety regulations, and distance. Therefore, it is necessary to use a precision current sensor and generate an overcurrent signal through operational amplifier processing and comparator comparison to trigger overcurrent protection. However, even so, the current sampling circuit is still difficult to use in 100KHz applications, such as LLC bidirectional DC conversion circuits. The bandwidth and rate requirements of the operational amplifier and comparator are relatively high, and the device selection is difficult and the cost is high. Summary of the invention

[0003] The embodiments of the present application provide an overcurrent protection circuit to solve at least one of the above-mentioned technical problems.

[0004] The overcurrent protection circuit of the embodiment of the present application is used in an LLC bidirectional DC conversion circuit, and the overcurrent protection circuit includes:

[0005] a first synchronous rectification circuit, wherein the first synchronous rectification circuit is connected to the primary side of the transformer of the LLC bidirectional DC conversion circuit and is used to detect a first signal of the primary side;

[0006] a second synchronous rectification circuit, the second synchronous rectification circuit being connected to a secondary side of the transformer of the LLC bidirectional DC conversion circuit and being used for detecting a second signal of the secondary side;

[0007] A control circuit, wherein the control circuit is configured to shut down the LLC bidirectional DC conversion circuit when the first signal exceeds a first preset value and / or when the second signal exceeds a second preset value.

[0008] The overcurrent protection circuit proposed in the present application uses a synchronous rectification circuit to monitor the current in the LLC bidirectional DC conversion circuit, and generates a signal to transmit to the control circuit. The control circuit shuts down the circuit in time when the signal exceeds a preset value, thereby realizing overcurrent protection for the LLC bidirectional DC conversion circuit. In addition, since the signal generated by the synchronous rectification circuit is usually of low frequency, high-speed and ultra-wide bandwidth operational amplifiers and comparators are not required, and the device cost is low, which is conducive to cost saving.

[0009] In some embodiments, the first synchronous rectification circuit is configured to detect the first signal of the primary side when the secondary side of the transformer of the LLC bidirectional DC conversion circuit is connected to the input terminal;

[0010] The second synchronous rectification circuit is configured to detect the second signal of the secondary side when the primary side of the transformer of the LLC bidirectional DC conversion circuit is connected to the input end.

[0011] In this way, the synchronous rectification circuit only detects the signal at the output end and performs over-current protection on the output end, which is beneficial to improving the efficiency and reaction speed of the over-current protection.

[0012] In some embodiments, the first synchronous rectification circuit includes a first current transformer, and the first synchronous rectification circuit is connected to the primary side of the transformer through the first current transformer;

[0013] The second synchronous rectification circuit includes a second current transformer, and the second synchronous rectification circuit is connected to the secondary side of the transformer through the second current transformer.

[0014] In this way, the synchronous rectification circuit is connected to the LLC bidirectional DC conversion circuit through the current transformer, and the current transformer can play a role of electrical isolation, saving isolation circuits and devices.

[0015] In some embodiments, the first synchronous rectification circuit further includes a first rectification circuit, one end of the first rectification circuit is grounded, the primary side of the first current transformer is connected to the primary side of the transformer, and the secondary side of the first current transformer is connected to the first rectification circuit;

[0016] The second synchronous rectification circuit also includes a second rectification circuit, one end of the second rectification circuit is grounded, the primary side of the second current transformer is connected to the secondary side of the transformer, and the secondary side of the second current transformer is connected to the second rectification circuit.

[0017] In this way, using a rectifier circuit to convert AC power into DC power is beneficial to reducing the loss of the rectifier and improving the efficiency of the DC / DC converter.

[0018] In some embodiments, the first rectifier circuit and the second rectifier circuit are diode bridge rectifier circuits.

[0019] In this way, the use of a diode bridge rectifier circuit is beneficial to improving rectification efficiency and stability, reducing the signal-to-noise ratio and saving costs.

[0020] In some embodiments, the first synchronous rectification circuit further includes a first conversion circuit, the first conversion circuit is connected in parallel with the first rectification circuit, and the first conversion circuit is configured to convert a current signal in the first synchronous rectification circuit into a first signal, and the first signal is a voltage signal;

[0021] The second synchronous rectification circuit also includes a second conversion circuit, which is connected in parallel with the second rectification circuit. The second conversion circuit is configured to convert a current signal in the second synchronous rectification circuit into a second signal, which is a voltage signal.

[0022] In this way, the conversion circuit converts the current signal into a voltage signal, which is beneficial to signal processing and transmission and to improving circuit performance.

[0023] In some embodiments, the first conversion circuit includes a first conversion resistor and a first capacitor, and the first conversion resistor is connected in parallel with the first capacitor;

[0024] The second conversion unit includes a second conversion resistor and a second capacitor, and the second conversion resistor is connected in parallel with the second capacitor.

[0025] In this way, the conversion resistor can convert the current signal into a voltage signal, which is then filtered by the capacitor, thereby retaining the peak signal, which is beneficial to improving the response speed of the control circuit.

[0026] In some embodiments, the number of the first conversion resistors is two, and the two first conversion resistors are connected in parallel;

[0027] The number of the second conversion resistors is two, and the two second conversion resistors are connected in parallel.

[0028] Thus, setting two conversion resistors is beneficial to improving conversion efficiency and reliability.

[0029] In some embodiments, the control circuit includes a first comparator, a second comparator and a controller, the first comparator is connected to the first synchronous rectifier circuit, the second comparator is connected to the second synchronous rectifier circuit, the first comparator is connected to the second comparator and the controller, the controller is grounded, the first comparator is configured to generate a first overcurrent signal when the first signal is greater than a first preset value, the second comparator is configured to generate a second overcurrent signal when the second signal is greater than a second preset value, and the controller is configured to shut down the LLC bidirectional DC conversion circuit when receiving the first overcurrent signal and / or the second overcurrent signal.

[0030] In this way, after the comparator is used to compare and process the signal, the controller turns off the LLC bidirectional DC conversion circuit when receiving the overcurrent signal transmitted by the comparator, which is beneficial to improving the processing speed of the controller and the response speed of the synchronous rectification circuit.

[0031] In some embodiments, the controller is connected to the first synchronous rectification circuit and the second synchronous rectification circuit, and the controller is configured to detect the synchronous rectification current signal of the LLC bidirectional DC conversion circuit according to the first signal and / or the second signal.

[0032] In this way, the controller can also detect the synchronous rectification current signal of the LLC bidirectional DC conversion circuit through the synchronous rectification circuit, so as to monitor the working state of the circuit in real time, and facilitate adjusting the working parameters of the circuit to optimize the performance of the circuit.

[0033] Additional aspects and advantages of the embodiments of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0035] Figure 1 It is a module schematic diagram of an overcurrent protection circuit and an LLC bidirectional DC conversion circuit according to an embodiment of the present application;

[0036] Figure 2 is a circuit diagram of an overcurrent protection circuit and an LLC bidirectional DC conversion circuit according to an embodiment of the present application;

[0037] Figure 3 is a circuit diagram of an overcurrent protection circuit according to an embodiment of the present application;

[0038] Figure 4 It is a steamed bun wave schematic diagram of the overcurrent protection circuit in the implementation mode of the present application.

[0039] Description of main component symbols: overcurrent protection circuit 100, first synchronous rectification circuit 10, first current transformer 11, first rectification circuit 12, first conversion circuit 13, first conversion resistor 131, first capacitor 132, second synchronous rectification circuit 20, second current transformer 21, second rectification circuit 22, second conversion circuit 23, second conversion resistor 231, second capacitor 232, control circuit 30, first comparator 31, second comparator 32, controller 33, LLC bidirectional DC conversion circuit 200, first end 201, second end 202, transformer 203, first DCDC circuit 204, first resonant network 205, second DCDC circuit 206, second resonant network 207. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention. In the description of the present invention, it is necessary to understand that the orientation or position relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0041] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be directly connected or indirectly connected through an intermediate medium. It can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0043] The disclosure herein provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described herein. Of course, they are merely examples, and the purpose is not to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art may appreciate the application of other processes and / or the use of other materials.

[0044] Bidirectional DC conversion circuits are widely used in distributed power generation systems, DC microgrids, new energy electric vehicles, power electronic transformers and other occasions. In order to prevent the components of the bidirectional DC conversion circuit from being affected by overcurrent, it is necessary to monitor the current of the bidirectional DC conversion circuit and shut down the bidirectional DC conversion circuit in time when overcurrent occurs to achieve overcurrent protection. The current sampling circuit needs to consider factors such as accuracy, withstand voltage, safety regulations, and distance. Therefore, it is necessary to use a precision current sensor and generate an overcurrent signal through operational amplifier processing and comparator comparison to trigger overcurrent protection. However, even so, the current sampling circuit is still difficult to use in 100KHz applications, such as LLC bidirectional DC conversion circuits. The bandwidth and rate requirements of the operational amplifier and comparator are relatively high, and the device selection is difficult and the cost is high.

[0045] See also Figure 1The overcurrent protection circuit 100 of the embodiment of the present application is used for an LLC bidirectional DC conversion circuit. The overcurrent protection circuit 100 includes a first synchronous rectification circuit 10, a second synchronous rectification circuit 20 and a control circuit 30. The first synchronous rectification circuit 10 is connected to the primary side of the transformer 203 of the LLC bidirectional DC conversion circuit for detecting a first signal on the primary side; the second synchronous rectification circuit 20 is connected to the secondary side of the transformer 203 of the LLC bidirectional DC conversion circuit for detecting a second signal on the secondary side; the control circuit 30 is configured to shut down the LLC bidirectional DC conversion circuit when the first signal exceeds a first preset value and / or the second signal exceeds a second preset value.

[0046] The overcurrent protection circuit 100 proposed in the present application uses a synchronous rectification circuit to monitor the current in the LLC bidirectional DC conversion circuit, and generates a signal to transmit to the control circuit 30. The control circuit 30 shuts down the circuit in time when the signal exceeds a preset value, thereby realizing overcurrent protection for the LLC bidirectional DC conversion circuit. In addition, since the signal generated by the synchronous rectification circuit is usually of low frequency, high-speed and ultra-wide bandwidth operational amplifiers and comparators are not required, and the device cost is low, which is conducive to cost saving.

[0047] Specifically, the LLC bidirectional direct current conversion circuit, namely, the LLC bidirectional DC / DC converter, is a highly efficient energy conversion circuit that can realize bidirectional flow and conversion of electric energy.

[0048] See also Figure 1 and Figure 2 The LLC bidirectional DC conversion circuit includes a first end 201, a second end 202, a transformer 203, a first DCDC circuit 204, a first resonant network 205, a second DCDC circuit 206 and a second resonant network 207. The first end 201 is connected in parallel with the first DCDC circuit 204. One end of the primary side of the transformer 203 is connected to the first DCDC circuit 204 through the first resonant network 205, and the other end is connected to the first DCDC circuit 204 through the first synchronous rectification circuit 10. The second end 202 is connected in parallel with the second DCDC circuit 206. One end of the secondary side of the transformer 203 is connected to the second DCDC circuit 206 through the second resonant network 207, and the other end is connected to the second DCDC circuit 206 through the second synchronous rectification circuit 20.

[0049] In some embodiments, the first synchronous rectification circuit 10 is configured to detect the first signal of the primary side when the secondary side of the transformer 203 of the LLC bidirectional DC conversion circuit is connected to the input terminal;

[0050] The second synchronous rectification circuit 20 is configured to detect the second signal of the secondary side when the primary side of the transformer 203 of the LLC bidirectional DC conversion circuit is connected to the input terminal.

[0051] In this way, the synchronous rectification circuit only detects the signal at the output end and performs over-current protection on the output end, which is beneficial to improving the efficiency and reaction speed of the over-current protection.

[0052] Specifically, in an embodiment of the present application, the first synchronous rectifier circuit 10 is used to detect a first signal at the output end, and the second synchronous rectifier circuit 20 is used to detect a second signal at the output end, that is, when the first end 201 is used as the input end, the second synchronous rectifier circuit 20 monitors the second signal at the secondary side of the transformer 203, and when the second end 202 is used as the input end, the first synchronous rectifier circuit 10 monitors the first signal at the primary side of the transformer 203. Only one of the first synchronous rectifier circuit 10 and the second synchronous rectifier circuit 20 is working at the same time to improve the response speed.

[0053] In other embodiments, the first synchronous rectification circuit 10 and the second synchronous rectification circuit 20 may also operate simultaneously, that is, no matter which end is used as the output end, the first synchronous rectification circuit 10 monitors the first signal on the primary side of the transformer 203, and the second synchronous rectification circuit 20 monitors the second signal on the secondary side of the transformer 203.

[0054] See also Figure 2 and Figure 3 In some embodiments, the first synchronous rectification circuit 10 includes a first current transformer 11, and the first synchronous rectification circuit 10 is connected to the primary side of the transformer 203 through the first current transformer 11;

[0055] The second synchronous rectification circuit 20 includes a second current transformer 21 . The second synchronous rectification circuit 20 is connected to the secondary side of the transformer 203 via the second current transformer 21 .

[0056] In this way, the synchronous rectification circuit is connected to the LLC bidirectional DC conversion circuit through the current transformer, and the current transformer can play a role of electrical isolation, saving isolation circuits and devices.

[0057] Specifically, a current transformer refers to an electrical instrument based on the principle of electromagnetic induction. It is mainly used to convert the large current on the primary side of the power system into a small current on the secondary side for measurement, protection and control. The current transformer is mainly composed of a closed iron core and a winding. Its primary winding has a small number of turns and is usually connected in series in the line of the current to be measured, so the entire current of the line often flows through it. The secondary winding has a large number of turns and is connected in series in the measuring instrument and protection circuit.

[0058] In the embodiment of the present application, the first current transformer 11 and the second current transformer 21 can reduce the current according to the turns ratio, so as to facilitate the measuring instrument to perform accurate measurement. In addition, when the current transformer is working, the primary side and the secondary side of the current transformer are electrically isolated by the iron core and the winding, which is conducive to ensuring the safety of the measuring instrument and the protection circuit.

[0059] In the embodiment of the present application, the first current transformer 11 is used to detect the current flowing through the first resonant network 205, and the second current transformer 21 is used to detect the current flowing through the second resonant network.

[0060] See also Figure 3 In some embodiments, the first synchronous rectifier circuit 10 further includes a first rectifier circuit 12, one end of the first rectifier circuit 12 is grounded, the primary side of the first current transformer 11 is connected to the primary side of the transformer 203, and the secondary side of the first current transformer 11 is connected to the first rectifier circuit 12;

[0061] The second synchronous rectification circuit 20 further includes a second rectification circuit 22 , one end of which is grounded, the primary side of the second current transformer 21 is connected to the secondary side of the transformer 203 , and the secondary side of the second current transformer 21 is connected to the second rectification circuit 22 .

[0062] In this way, using a rectifier circuit to convert AC power into DC power is beneficial to reducing the loss of the rectifier and improving the efficiency of the DC / DC converter.

[0063] Specifically, in the embodiment of the present application, the first rectifier circuit 12 and the second rectifier circuit 22 take the absolute value of the high-frequency pulsating alternating current into a steamed-bun waveform. After the alternating current is converted into a steamed-bun waveform, it is beneficial to improve the measurement accuracy and avoid external interference, thereby reducing its influence on the measurement result. In addition, the steamed-bun waveform has a simple mathematical form, which is convenient for mathematical processing and algorithm analysis. After the high-frequency pulsating alternating current is converted into a steamed-bun waveform, it can meet the needs of different measuring devices and sensors.

[0064] In some embodiments, the first rectifier circuit 12 and the second rectifier circuit 22 are diode bridge rectifier circuits.

[0065] In this way, the use of a diode bridge rectifier circuit is beneficial to improving rectification efficiency and stability, reducing the signal-to-noise ratio and saving costs.

[0066] Specifically, a diode bridge rectifier circuit is a commonly used rectifier circuit that can convert alternating current into direct current. In the embodiment of the present application, taking the first rectifier circuit 12 as an example, the circuit is mainly composed of four diodes, which are connected in series in pairs and then connected in parallel with the secondary side of the first current transformer 11 to form a "bridge" structure.

[0067] The diode bridge rectifier circuit has high and stable output voltage, high rectification efficiency, strong adaptability and high reliability. In addition, the bridge rectifier circuit requires relatively few components, consisting of only four diodes, with a simple structure, and due to the small number of components and easy availability, the cost is relatively low.

[0068] In some embodiments, the first synchronous rectification circuit 10 further includes a first conversion circuit 13, the first conversion circuit 13 is connected in parallel with the first rectification circuit 12, and the first conversion circuit 13 is configured to convert the current signal in the first synchronous rectification circuit 10 into a first signal, and the first signal is a voltage signal;

[0069] The second synchronous rectification circuit 20 further includes a second conversion circuit 23 , which is connected in parallel with the second rectification circuit 22 . The second conversion circuit 23 is configured to convert the current signal in the second synchronous rectification circuit 20 into a second signal, which is a voltage signal.

[0070] In this way, the conversion circuit converts the current signal into a voltage signal, which is beneficial to signal processing and transmission and to improving circuit performance.

[0071] Specifically, since the control circuit 30 can usually only process voltage signals, in the embodiment of the present application, the current signal is converted into a voltage signal by setting a first conversion circuit 13 and a second conversion circuit 23. In addition, converting the current signal into a voltage signal is also beneficial for filtering peak values, which is beneficial for improving the response speed of the overcurrent protection circuit 100.

[0072] See also Figure 2 and Figure 3 In some embodiments, the first conversion circuit 13 includes a first conversion resistor 131 and a first capacitor 132, and the first conversion resistor 131 is connected in parallel with the first capacitor 132;

[0073] The second conversion unit includes a second conversion resistor 231 and a second capacitor 232 . The second conversion resistor 231 and the second capacitor 232 are connected in parallel.

[0074] In this way, the conversion resistor can convert the current signal into a voltage signal, which is then filtered by the capacitor, thereby retaining the peak signal, which is beneficial to improving the response speed of the control circuit 30.

[0075] Specifically, in the embodiment of the present application, the first resistor is used to convert the current signal into a voltage signal, and the first capacitor 132 is used to filter the peak value of the first signal. Similarly, the second resistor is used to convert the current signal into a voltage signal, and the second capacitor 232 is used to filter the peak value of the second signal.

[0076] In some embodiments, the number of the first conversion resistors 131 is two, and the two first conversion resistors 131 are connected in parallel;

[0077] The number of the second conversion resistors 231 is two, and the two second conversion resistors 231 are connected in parallel.

[0078] Thus, setting two conversion resistors is beneficial to improving conversion efficiency and reliability.

[0079] Specifically, there are multiple first conversion resistors 131 , and multiple first conversion resistors 131 are connected in parallel to improve the efficiency and reliability of converting current signals into voltage signals. In the embodiment of the present application, there are two first conversion resistors 131 .

[0080] Similarly, there are multiple second conversion resistors 231, and multiple second conversion resistors 231 are connected in parallel to improve the efficiency and reliability of converting current signals into voltage signals. In the embodiment of the present application, there are two second conversion resistors 231.

[0081] In some embodiments, the control circuit 30 includes a first comparator 31, a second comparator 32 and a controller 33, the first comparator 31 is connected to the first synchronous rectifier circuit 10, the second comparator 32 is connected to the second synchronous rectifier circuit 20, the first comparator 31 is connected to the second comparator 32 and the controller 33, the controller 33 is grounded, the first comparator 31 is configured to generate a first overcurrent signal when the first signal is greater than a first preset value, the second comparator 32 is configured to generate a second overcurrent signal when the second signal is greater than a second preset value, and the controller 33 is configured to shut down the LLC bidirectional DC conversion circuit when receiving the first overcurrent signal and / or the second overcurrent signal.

[0082] In this way, after the comparator is used to compare and process the signal, the controller 33 turns off the LLC bidirectional DC conversion circuit when receiving the overcurrent signal transmitted by the comparator, which is beneficial to improving the processing speed of the controller 33 and the response speed of the synchronous rectification circuit.

[0083] Specifically, the comparator is mainly used to compare the sizes of two voltage or current signals and generate an output signal based on the comparison result. In the embodiment of the present application, the first comparator 31 is used to compare the first signal with the first preset value, and the second comparator 32 is used to compare the second signal with the second preset value. The first signal, the second signal, the first preset value and the second preset value are all voltage signals.

[0084] See also Figure 2 and Figure 3 In some embodiments, the controller 33 is connected to the first synchronous rectification circuit 10 and the second synchronous rectification circuit 20, and the controller 33 is configured to detect the synchronous rectification current signal of the LLC bidirectional DC conversion circuit according to the first signal and / or the second signal.

[0085] In this way, the controller 33 can also detect the synchronous rectification current signal of the LLC bidirectional DC conversion circuit through the synchronous rectification circuit, so as to monitor the working state of the circuit in real time, and facilitate adjusting the working parameters of the circuit to optimize the performance of the circuit.

[0086] Specifically, in the embodiment of the present application, in addition to performing overcurrent protection, the controller 33 can also monitor the working state of the circuit in real time, so as to adjust the working parameters of the circuit to optimize the performance of the circuit.

[0087] In summary, the principle of the overcurrent protection circuit 100 is:

[0088] When the first end 201 charges the second end 202, the four switches of the first DCDC circuit 204 switch at a fixed frequency and duty cycle. The duty cycle is generally close to 50%, and the frequency range is 60K to 250K. The specific operating frequency is related to the input-output voltage ratio, the transformer 203 turns ratio, and the transmission power. The waveform flowing through the second current transformer 21 is approximately a sine wave, and the frequency of the waveform is the switching frequency.

[0089] The second current transformer 21 detects the current flowing through the second resonant network 207. The current signal is isolated and converted into a current of a certain proportion by the second current transformer 21, and then rectified by the second rectifier circuit 22. The current signal is converted from a sine wave to a steamed wave. Figure 4 As shown. The current flows through the second conversion resistor 231 and is converted into a second signal, which is a voltage signal. The second signal is respectively connected to the controller 33 and the second comparator 32. The second comparator 32 compares and determines whether there is an overcurrent. If it is greater than the second preset value, the second comparator 32 generates a second overcurrent signal and sends it to the controller 33. After receiving the second overcurrent signal, the controller 33 turns off the LLC bidirectional DC conversion circuit to play the role of overcurrent protection. The controller 33 also monitors the working state of the circuit in real time according to the second signal, so as to adjust the working parameters of the circuit to optimize the performance of the circuit.

[0090] When the second end 202 charges the first end 201, the four switch tubes of the second DCDC circuit 206 switch at a fixed frequency and duty cycle. The duty cycle is generally close to 50%, and the frequency range is 60K to 250K. The specific operating frequency is related to the input-output voltage ratio, the transformer 203 turns ratio, and the transmission power. The waveform flowing through the first current transformer 11 is approximately a sine wave, and the frequency of the waveform is the switching frequency.

[0091] The first current transformer 11 detects the current flowing through the first resonant network 205. The current signal is isolated and converted into a current of a certain proportion by the first current transformer 11, and then rectified by the first rectifier circuit 12. The current signal is converted from a sine wave to a steamed wave. Figure 4As shown. The current flows through the first conversion resistor 131 and is converted into a first signal, which is a voltage signal. The first signal is respectively connected to the controller 33 and the first comparator 31. The first comparator 31 compares and determines whether there is overcurrent. If it is greater than the first preset value, the first comparator 31 generates a first overcurrent signal and sends it to the controller 33. After receiving the first overcurrent signal, the controller 33 turns off the LLC bidirectional DC conversion circuit to play the role of overcurrent protection. The controller 33 also monitors the working state of the circuit in real time according to the first signal, so as to adjust the working parameters of the circuit to optimize the performance of the circuit.

[0092] In the description of this specification, the description with reference to the terms "certain embodiments", "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0093] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, unless otherwise clearly and specifically defined.

[0094] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application. The scope of the present application is defined by the claims and their equivalents.

Claims

1. An overcurrent protection circuit (100) for an LLC bidirectional DC conversion circuit, characterized in that: The overcurrent protection circuit (100) comprises: A first synchronous rectification circuit (10), the first synchronous rectification circuit (10) being connected to the primary side of the transformer (203) of the LLC bidirectional DC conversion circuit and being used to detect a first signal of the primary side; A second synchronous rectification circuit (20), the second synchronous rectification circuit (20) being connected to a secondary side of a transformer (203) of the LLC bidirectional DC conversion circuit and being used to detect a second signal of the secondary side; A control circuit (30), wherein the control circuit (30) is configured to shut down the LLC bidirectional DC conversion circuit when the first signal exceeds a first preset value and / or when the second signal exceeds a second preset value.

2. The overcurrent protection circuit (100) according to claim 1, characterized in that: The first synchronous rectification circuit (10) is configured to detect a first signal on the primary side when the secondary side of the transformer (203) of the LLC bidirectional DC conversion circuit is connected to the input end; The second synchronous rectification circuit (20) is configured to detect the second signal of the secondary side when the primary side of the transformer (203) of the LLC bidirectional DC conversion circuit is connected to the input end.

3. The overcurrent protection circuit (100) according to claim 1, characterized in that: The first synchronous rectification circuit (10) comprises a first current transformer (11), and the first synchronous rectification circuit (10) is connected to the primary side of the transformer (203) via the first current transformer (11); The second synchronous rectification circuit (20) comprises a second current transformer (21), and the second synchronous rectification circuit (20) is connected to the secondary side of the transformer (203) via the second current transformer (21).

4. The overcurrent protection circuit (100) according to claim 3, characterized in that: The first synchronous rectification circuit (10) further comprises a first rectification circuit (12), one end of the first rectification circuit (12) is grounded, the primary side of the first current transformer (11) is connected to the primary side of the transformer (203), and the secondary side of the first current transformer (11) is connected to the first rectification circuit (12); The second synchronous rectification circuit (20) further comprises a second rectification circuit (22), one end of the second rectification circuit (22) is grounded, the primary side of the second current transformer (21) is connected to the secondary side of the transformer (203), and the secondary side of the second current transformer (21) is connected to the second rectification circuit (22).

5. The overcurrent protection circuit (100) according to claim 4, characterized in that: The first rectifier circuit (12) and the second rectifier circuit (22) are diode bridge rectifier circuits.

6. The overcurrent protection circuit (100) according to claim 4, characterized in that: The first synchronous rectification circuit (10) further comprises a first conversion circuit (13), the first conversion circuit (13) being connected in parallel with the first rectification circuit (12), the first conversion circuit (13) being configured to convert a current signal in the first synchronous rectification circuit (10) into a first signal, the first signal being a voltage signal; The second synchronous rectification circuit (20) further comprises a second conversion circuit (23), wherein the second conversion circuit (23) is connected in parallel with the second rectification circuit (22), and the second conversion circuit (23) is configured to convert a current signal in the second synchronous rectification circuit (20) into a second signal, wherein the second signal is a voltage signal.

7. The overcurrent protection circuit (100) according to claim 6, characterized in that: The first conversion circuit (13) comprises a first conversion resistor (131) and a first capacitor (132), wherein the first conversion resistor (131) and the first capacitor (132) are connected in parallel; The second conversion unit comprises a second conversion resistor (231) and a second capacitor (232), and the second conversion resistor (231) and the second capacitor (232) are connected in parallel.

8. The overcurrent protection circuit (100) according to claim 6, characterized in that: The number of the first conversion resistors (131) is two, and the two first conversion resistors (131) are connected in parallel; The number of the second conversion resistors (231) is two, and the two second conversion resistors (231) are connected in parallel.

9. The overcurrent protection circuit (100) according to claim 1, characterized in that: The control circuit (30) comprises a first comparator (31), a second comparator (32) and a controller (33), wherein the first comparator (31) is connected to the first synchronous rectification circuit (10), the second comparator (32) is connected to the second synchronous rectification circuit (20), the first comparator (31) is connected to the second comparator (32) and the controller (33), the controller (33) is grounded, the first comparator (31) is configured to generate a first overcurrent signal when the first signal is greater than a first preset value, the second comparator (32) is configured to generate a second overcurrent signal when the second signal is greater than a second preset value, and the controller (33) is configured to shut down the LLC bidirectional DC conversion circuit when receiving the first overcurrent signal and / or the second overcurrent signal.

10. The overcurrent protection circuit (100) according to claim 9, characterized in that: The controller (33) is connected to the first synchronous rectification circuit (10) and the second synchronous rectification circuit (20), and the controller (33) is configured to detect a synchronous rectification current signal of the LLC bidirectional DC conversion circuit according to the first signal and / or the second signal.

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