Current control circuit, flyback circuit and switching power supply

Abstract

The invention provides a current control circuit, a flyback circuit and a switching power supply. The current control circuit comprises a current sampling module, a voltage dividing module and a voltage adjusting module. The voltage dividing module comprises a first resistor and a second resistor; the first end of the current sampling module is used for connecting a to-be-sampled circuit, and the second end of the current sampling module is grounded through the first resistor and the second resistor which are connected in series; a connection point of the first resistor and the second resistor is connected with a voltage output end which is used for connecting a control module; the second end of the current sampling module is also connected with the first end of the voltage regulation module; the second end of the voltage adjusting module is connected with the connection point of the first resistor and the second resistor. The third end of the voltage regulation module is connected with the voltage output end; the voltage adjusting module is used for increasing the voltage signal at the voltage output end when the voltage at the two ends of the first resistor is larger than or equal to a preset voltage threshold value. The current-limiting protection action can be triggered in advance, and the occurrence of circuit overcurrent damage is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular, to a current control circuit, a flyback circuit, and a switching power supply. Background Art

[0002] In a switching power supply, current limiting control is generally performed by sampling the current in a sampling circuit. When the sampled current exceeds a set current limiting value, the control module in the switching power supply will perform current limiting protection to prevent the circuits in the switching power supply from being damaged by overcurrent. For example, the current limiting protection function of a Pulse Width Modulation (PWM) control chip in the switching power supply is triggered. However, there is a certain delay between triggering the current limiting protection and completing the current limiting protection action. When the current limiting protection action is completed, the current output by the switching power supply may have exceeded the set current limiting value, causing circuit damage. Summary of the Invention

[0003] Embodiments of the present application provide a current control circuit, a multi-switch flyback circuit, and a switching power supply to trigger the current limiting protection function in advance and reduce the occurrence of circuit overcurrent damage.

[0004] In a first aspect, an embodiment of the present application provides a current control circuit, including a current sampling module, a voltage dividing module, and a voltage regulating module; wherein, the voltage dividing module includes a first resistor and a second resistor;

[0005] A first end of the current sampling module is used to connect a circuit to be sampled, and a second end of the current sampling module is grounded through the series-connected first resistor and second resistor; a connection point of the first resistor and the second resistor is connected to a voltage output end, and the voltage output end is used to connect a control module;

[0006] The second end of the current sampling module is further connected to a first end of the voltage regulating module; a second end of the voltage regulating module is connected to the connection point of the first resistor and the second resistor; a third end of the voltage regulating module is connected to the voltage output end;

[0007] The current sampling module is configured to collect a target current of the circuit to be sampled and output the target current to the first resistor and the second resistor;

[0008] The voltage regulating module is configured to increase a voltage signal at the voltage output end when a voltage across the first resistor is greater than or equal to a preset voltage threshold, and the voltage output end is configured to output the increased voltage signal to the control module, so that the control module performs current limiting protection on the circuit to be sampled when the voltage sampling signal exceeds the voltage threshold corresponding to the current limiting value.

[0009] In a possible implementation, the voltage regulation module includes a first switching transistor, a second switching transistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor;

[0010] The current sampling module is connected to the connection point of the first resistor and the second resistor through the series-connected third resistor and fourth resistor;

[0011] The connection point of the third resistor and the fourth resistor is also connected to the control terminal of the first switching transistor;

[0012] The first end of the first switching transistor is connected to the power supply through the fifth resistor and to the control terminal of the second switching transistor through the sixth resistor; the second end of the first switching transistor is connected to the connection point of the first resistor and the second resistor;

[0013] The first end of the second switching transistor is connected to the power supply, and the second end of the second switching transistor is connected to the voltage output terminal through the seventh resistor.

[0014] In a possible implementation, the circuit to be sampled includes multiple branches to be sampled, the current control circuit includes multiple current sampling modules, and the voltage division module includes multiple first resistors; the branches to be sampled, the current sampling modules, and the first resistors are in one-to-one correspondence; the target current includes the branch target current of each branch to be sampled collected.

[0015] The first end of each current sampling module is used to connect to the output terminal of its corresponding branch to be sampled; the second end of each current sampling module is connected to the first end of the second resistor through its corresponding first resistor; the second end of the second resistor is grounded; the second end of each current sampling module is also respectively connected to the first end of the voltage regulation module;

[0016] Each current sampling module is used to collect the branch target current of its corresponding branch to be sampled and output the branch target current to its corresponding first resistor and the second resistor;

[0017] The voltage regulation module is used to increase the voltage signal at the voltage output terminal when the voltage across the first resistor is greater than or equal to the preset voltage threshold.

[0018] In a possible implementation, the voltage regulation module includes a first switching transistor, a second switching transistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and multiple first diodes; wherein, the current sampling modules are in one-to-one correspondence with the first diodes;

[0019] Each current sampling module is connected to the anode of its corresponding first diode, and the cathode of each first diode is connected to the connection point of its corresponding first resistor and the second resistor through the series-connected third resistor and the fourth resistor;

[0020] The connection point of the third resistor and the fourth resistor is also connected to the control end of the first switching tube;

[0021] The first end of the first switching tube is connected to the power supply through the fifth resistor and to the control end of the second switching tube through the sixth resistor; the second end of the first switching tube is connected to the connection point of the first resistor and the second resistor;

[0022] The first end of the second switching tube is connected to the power supply, and the second end of the second switching tube is connected to the voltage output end through the seventh resistor.

[0023] In a possible implementation, the voltage dividing module further includes an eighth resistor, a plurality of sampling resistors, and a plurality of second diodes; the voltage regulating module includes a plurality of first ends and a plurality of second ends; wherein, the current sampling module, the sampling resistor, and the second diode correspond one by one; the first end and the second end of the voltage regulating module correspond to the current sampling module one by one;

[0024] The second end of each current sampling module is connected to the anode of its corresponding second diode and one end of its corresponding sampling resistor through its corresponding first resistor; the other end of each sampling resistor is grounded;

[0025] The cathode of each second diode is connected to the first end of the second resistor through the eighth resistor; the second end of the second resistor is grounded;

[0026] The second end of each current sampling module is also respectively connected to the first end of its corresponding voltage regulating module, and each second end of the voltage regulating module is respectively connected to the connection point of its corresponding first resistor and the second diode.

[0027] In a possible implementation, the voltage regulating module includes a plurality of first switching tubes, a plurality of third resistors, and a plurality of fourth resistors, and the voltage regulating module further includes a second switching tube, a fifth resistor, a sixth resistor, and a seventh resistor; wherein, the current sampling module corresponds to the first switching tube, the third resistor, and the fourth resistor one by one;

[0028] Each current sampling module is connected to the connection point of its corresponding first resistor and the second diode through its corresponding series-connected third resistor and fourth resistor;

[0029] The connection point of each series-connected third resistor and fourth resistor is also connected to the control end of its corresponding first switching tube;

[0030] The first end of each first switching tube is connected to a power supply through the fifth resistor and to the control end of the second switching tube through the sixth resistor; the second end of each first switching tube is connected to the connection point of its corresponding first resistor and the second resistor.

[0031] The first end of the second switching tube is connected to the power supply, and the second end of the second switching tube is connected to the voltage output end through the seventh resistor.

[0032] In a possible implementation manner, the voltage dividing module further includes a ninth resistor and a first capacitor.

[0033] The connection point of the first resistor and the second resistor is connected to the first end of the first capacitor, the third end of the voltage regulation module, and the control module through the ninth resistor.

[0034] The second end of the first capacitor is grounded.

[0035] In a possible implementation manner, the current sampling module includes a current transformer and an absorption unit.

[0036] The primary winding of the current transformer is connected in series with the winding at the output end of the circuit to be sampled.

[0037] The same-named end of the secondary winding of the current transformer is connected to the first end of the absorption unit.

[0038] The second end of the absorption sub-unit is grounded through the series-connected first resistor and second resistor.

[0039] The different-named end of the secondary winding of the current transformer and the third end of the absorption unit are grounded.

[0040] In a possible implementation manner, when the voltage across the first resistor is less than the preset voltage threshold, the voltage output end is further configured to use the voltage corresponding to the second resistor as a voltage signal and output it to the control module, so that the control module adjusts the circuit to be sampled according to the voltage signal.

[0041] In a second aspect, an embodiment of the present application provides a flyback circuit, including the current control circuit in any one of the possible implementation manners in the first aspect above.

[0042] In a third aspect, an embodiment of the present application provides a switching power supply, including the multi-switch flyback circuit in the second aspect above.

[0043] The beneficial effects of the embodiments of the present application compared with the prior art are:

[0044] In the embodiment of the present application, the current sampling module collects the target current of the circuit to be sampled and outputs the target current to the first resistor and the second resistor. When the voltage regulation module detects that the voltage across the first resistor is greater than or equal to the preset voltage threshold, it indicates that the current in the circuit to be sampled is relatively large, approaching the current limit value, and the current limit protection may be triggered. Then, the voltage signal at the voltage output end is increased, and the output voltage signal can be temporarily raised. The voltage output end is used to output the increased voltage signal to the control module, so that when the voltage sampling signal exceeds the voltage threshold corresponding to the current limit value, the control module performs current limit protection on the circuit to be sampled. It can trigger the current limit protection function in advance when the current in the circuit to be sampled approaches the current limit value but does not exceed it, allowing sufficient action time for the current limit protection and reducing the occurrence of circuit overcurrent damage. Brief Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0046] Figure 1 It is a schematic diagram of the module structure of a current control circuit provided by an embodiment of the present application;

[0047] Figure 2 It is a schematic diagram of the structure of a current control circuit provided by an embodiment of the present application;

[0048] Figure 3 It is a schematic diagram of the structure of a current control circuit provided by another embodiment of the present application;

[0049] Figure 4 It is a schematic diagram of the structure of a current control circuit provided by still another embodiment of the present application;

[0050] Figure 5 It is a waveform diagram of the collected voltage provided by an embodiment of the present application. Detailed Embodiments

[0051] In order to enable those skilled in the art to better understand this solution, the following clearly describes the technical solutions in the embodiments of this solution in conjunction with the drawings in the embodiments of this solution. Obviously, the described embodiments are some but not all of the embodiments of this solution. Based on the embodiments in this solution, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this solution.

[0052] In the description, claims, and above-mentioned drawings of this solution, the term "including" and any other variations thereof mean "including but not limited to", intending to cover non-exclusive inclusion and not limited only to the examples listed in the text. In addition, terms such as "first" and "second" are used to distinguish different objects rather than to describe a specific order.

[0053] The inventor found that when the current value in the circuit to be sampled exceeds the current limit value, current limit protection will be triggered, and then the current limit protection action will be carried out to prevent the circuit from being damaged by overcurrent. However, there is a certain delay between the triggering of current protection and the completion of the current limit protection action. During the process of completing the current limit protection action, there may be a current exceeding the current limit value in the circuit to be sampled, resulting in circuit damage.

[0054] With the idea of reducing the possibility of the circuit being damaged by overcurrent, in the embodiment of this application, the current sampling module is used to collect the target current of the circuit to be sampled, and the detection module and the adjustment module are set. The detection module is used to make a first judgment on the target current first. When the target current is greater than or equal to the preset threshold, the adjustment module is controlled to generate a first current and output it to the current sampling module, pulling up the output signal of the current sampling module, so as to trigger the current limit protection function in advance when the current in the circuit to be sampled is close to but does not exceed the current limit value, allowing sufficient action time for the current limit protection and reducing the occurrence of circuit overcurrent damage.

[0055] To make the purpose, technical solution, and advantages of this application clearer, the following will be described through specific embodiments in conjunction with the drawings.

[0056] Figure 1 The module structure schematic diagram of the current control circuit provided by the embodiment of this application is described in detail as follows:

[0057] The current control circuit provided by this application includes a current sampling module, a voltage division module, and a voltage adjustment module; among them, the voltage division module includes a first resistor R1 and a second resistor R2.

[0058] The first end of the current sampling module is used to connect the circuit to be sampled, and the second end of the current sampling module is grounded through the series-connected first resistor R1 and second resistor R2; the connection point of the first resistor R1 and the second resistor R2 is connected to the voltage output terminal Vcs, and the voltage output terminal Vcs is used to connect the control module. The second end of the current sampling module is also connected to the first end of the voltage adjustment module; the second end of the voltage adjustment module is connected to the connection point of the first resistor R1 and the second resistor R2; the third end of the voltage adjustment module is connected to the voltage output terminal Vcs.

[0059] Here, the circuit to be sampled is a circuit that needs to perform current sampling and control, such as a forward circuit, a flyback circuit, a buck-boost circuit, a constant current circuit, etc. The control module includes a current limiting protection function, which can be used to perform current limiting protection actions. The control module can be a control chip, such as a PWM control chip, or a specific current limiting protection circuit.

[0060] The current sampling module is used to collect the target current of the circuit to be sampled and output the target current to the first resistor R1 and the second resistor R2. Among them, the current sampling module can collect the target current of the circuit to be sampled through current signals, voltage signals, current transformers, etc. The first resistor R1 and the second resistor R2 perform voltage division, and the voltage output terminal Vcs is used to output a voltage signal.

[0061] The voltage regulation module is used to increase the voltage signal at the voltage output terminal Vcs when the voltage across the first resistor R1 is greater than or equal to a preset voltage threshold. The voltage output terminal Vcs is used to output the increased voltage signal to the control module, so that the control module can perform current limiting protection on the circuit to be sampled when the voltage sampling signal exceeds the voltage threshold corresponding to the current limiting value.

[0062] In this embodiment, when the voltage across the first resistor R1 is greater than or equal to the preset voltage threshold, the voltage regulation module can pull up the voltage signal at the voltage output terminal, so that the voltage output terminal outputs a higher voltage signal to trigger the current limiting protection function in advance. When the voltage across the first resistor R1 is greater than or equal to the preset voltage threshold, it indicates that the target current is close to the current limiting value.

[0063] Among them, the preset voltage threshold can be set according to the current limiting value and the resistance value of the first resistor R1. At the same time, the ratio of the preset voltage threshold to the resistance value of the first resistor R1 can be less than and close to the current limiting value, so as to trigger the current limiting protection in advance in time when the current in the circuit to be sampled is close to the current limiting value.

[0064] Here, through the cooperation between the preset voltage threshold and the difference of the current limiting value, the current limiting protection can be triggered in advance, and it is ensured that when the current limiting protection action is completed, the current in the circuit to be sampled does not exceed the current limiting value.

[0065] Optionally, when the voltage across the first resistor R1 is less than the preset voltage threshold, the voltage regulation module will not pull up the voltage signal of the voltage output terminal Vcs; the voltage output terminal Vcs is also used to use the voltage corresponding to the second resistor R2 as a voltage signal and output it to the control module, so that the control module can adjust the circuit to be sampled according to the voltage signal.

[0066] In this embodiment, when the voltage across the first resistor R1 is less than the preset voltage threshold, it indicates that the current in the circuit to be sampled is far from the current limiting value, and current limiting protection is not required temporarily. Therefore, the voltage signal at the voltage output terminal can be not raised, and the voltage signal corresponding to the target current can be directly output to the control module, so that the control module can adjust the current in the circuit to be sampled according to the target current sampled in the circuit to be sampled.

[0067] For example, if the circuit to be sampled is a constant current circuit, the control module can adjust the current in the circuit to be sampled according to the target current sampled to maintain a constant current.

[0068] In summary, the current control circuit provided in this embodiment includes at least two states:

[0069] (1) When the target current does not reach (is less than) the preset threshold, the voltage adjustment module does not work, that is, the voltage signal at the voltage output terminal Vcs is not raised, and the voltage output terminal Vcs directly transmits the voltage signal corresponding to the collected target current to the control module, so that the control module can adjust the circuit to be sampled according to the target current.

[0070] (2) When the target current reaches (is greater than or equal to) the preset threshold, the detection module controls the adjustment module to work, raises the voltage signal at the voltage output terminal Vcs, so that the voltage signal output by the voltage output terminal Vcs exceeds the voltage signal corresponding to the current limiting value, triggers the current limiting protection in advance, and performs and completes the current limiting protection action before the target current exceeds the current limiting value.

[0071] In the embodiment of the present application, the current sampling module samples the target current of the circuit to be sampled and outputs the target current to the first resistor and the second resistor; when the voltage across the first resistor detected by the voltage adjustment module is greater than or equal to the preset voltage threshold, it indicates that the current in the circuit to be sampled is large and close to the current limiting value, and current limiting protection may be triggered. Then, the voltage signal at the voltage output terminal is increased, and the voltage signal output by the current sampling module can be temporarily raised. The voltage output terminal is used to output the increased voltage signal to the control module, so that when the voltage sampling signal exceeds the voltage threshold corresponding to the current limiting value, the control module performs current limiting protection on the circuit to be sampled, and can trigger the current limiting protection function in advance when the current in the circuit to be sampled is close to the current limiting value but does not exceed the current limiting value, so that the current limiting protection has sufficient action time and reduces the occurrence of circuit overcurrent damage.

[0072] In some embodiments, as Figure 2 shown, the voltage adjustment module includes a first switching transistor Q1, a second switching transistor Q2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7.

[0073] The current sampling module is connected to the connection point of the first resistor R1 and the second resistor R2 through the series-connected third resistor R3 and fourth resistor R4; the connection point of the third resistor R3 and the fourth resistor R4 is also connected to the control end of the first switching tube Q1; the first end of the first switching tube Q1 is connected to the power supply Vaux through the fifth resistor R5, and is connected to the control end of the second switching tube Q2 through the sixth resistor R6; the second end of the first switching tube Q1 is connected to the connection point of the first resistor R1 and the second resistor R2; the first end of the second switching tube Q2 is connected to the power supply Vaux, and the second end of the second switching tube Q2 is connected to the voltage output end Vcs through the seventh resistor R7.

[0074] In this embodiment, after the third resistor R3 and the fourth resistor R4 are connected in series, they are connected in parallel with the first resistor R1, and both ends of one resistor of the third resistor R3 and the fourth resistor R4 are respectively connected to the control end and the second end of the first switching tube Q1. When the first switching tube Q1 is turned on, the power supply Vaux is connected to the first end of the first switching tube Q1 through the fifth resistor R5. Furthermore, the voltage across the fifth resistor R5 can turn on the second switching tube Q2 and raise the voltage of the voltage output end Vcs.

[0075] Refer to Figure 2 , the control end and the second end of the first switching tube Q1 can be respectively connected to both ends of the fourth resistor R4. The current collected by the current sampling module passes through the first resistor R1, and the voltage across the first resistor R1 is divided by the third resistor R3 and the fourth resistor R4. When the voltage across the fourth resistor R4 reaches the conduction voltage drop of the first switching tube Q1, the first switching tube Q1 is turned on, so that the second switching tube Q2 connected to the first end of the first switching tube Q1 can be controlled to be turned on, thereby raising the voltage signal of the voltage output end Vcs. Among them, the power supply Vaux supplies power and is divided by the seventh resistor R7 and the second resistor R2 to realize the raising of the voltage signal at the voltage output end Vcs.

[0076] Here, whether the voltage signal of the voltage output end Vcs is raised is determined by the conduction voltage drop of the first switching tube Q1. Among them, by setting the resistance values of the third resistor R3 and the fourth resistor R4, the preset voltage threshold in the voltage adjustment module is set. For example, Figure 2 in the control end and the second end of the first switching tube Q1 in are connected to both ends of the fourth resistor R4, and the voltage across the fourth resistor R4 should be the conduction voltage drop of the first switching tube Q1.

[0077] In some embodiments, the circuit to be sampled can be a circuit provided with windings, such as a forward circuit and a flyback circuit, etc. The current sampling module can include a current transformer CT and an absorption unit.

[0078] The primary winding of the current transformer CT is connected in series with the winding of the output end of the circuit to be sampled; the same-name end of the secondary winding of the current transformer CT is connected to the first end of the absorption unit; the second end of the absorption unit is connected to the first end of its corresponding first resistor; the opposite-name end of the secondary winding of the current transformer CT and the third end of the absorption unit are grounded.

[0079] In this embodiment, the primary winding of the current transformer is connected in series with the winding of the circuit to be sampled, so that the current of the corresponding winding in the circuit to be sampled can be collected.

[0080] Due to the leakage inductance of the current transformer CT, leakage magnetic flux will be formed outside the magnetic core, interfering with the normal operation of nearby components. And due to the existence of leakage inductance, current reversal may occur, that is, negative current is generated. Therefore, in order to accurately collect the current of the corresponding winding in the branch to be sampled, the absorption subunit can be used to demagnetize and remove the negative current so that only the positive current flows into the subsequent components.

[0081] Optionally, the absorption unit may include a tenth resistor R10, a third diode D3 and a fourth diode D4. A first end of the tenth resistor R10 is connected to an anode of the fourth diode D4 as a first end of the absorption unit; a cathode of the fourth diode D4 is used as a second end of the absorption unit; a second end of the tenth resistor R10 is connected to a cathode of the third diode D3; and an anode of the third diode D3 is used as a third end of the absorption unit.

[0082] In this embodiment, by providing the tenth resistor R10 and the third diode D3, demagnetization can be achieved to prevent the leakage magnetic field of the current transformer CT from interfering with nearby components.

[0083] By setting the fourth diode D4, negative current can be removed and the diode is only turned on when there is a positive current. At the same time, the tenth resistor R10 and the third diode D3 can also consume negative current to ensure the accuracy of subsequent maximum current sampling.

[0084] In addition, the inventors have also found that when the circuit to be sampled includes multiple branches, it is necessary to sample and control the current in each branch, which is usually done by sampling the sum of the currents of each branch. If the multiple primary currents have good consistency, the effect of sampling the sum of the primary currents for current limiting control will also be better. However, due to the influence of the parasitic parameters of the transformer, the multiple primary currents often have uneven currents. For example, the current of one primary winding is too large, and the current of another primary winding is too small. At this time, if the current of one primary winding is too large, but the total current of the sampled primary winding is not enough to trigger the current limiting protection, it may cause circuit damage.

[0085] With the idea of reducing the possibility of overcurrent damage to the circuit, in the embodiments of the present application, a voltage regulation module is used to determine whether the voltage across the first resistor is greater than or equal to a preset voltage threshold. When the voltage across the first resistor is greater than or equal to the preset voltage threshold, the voltage signal at the voltage output terminal is pulled up to avoid the situation of circuit damage caused by excessive current in one path, trigger the current limiting protection in a timely and accurate manner, and reduce the occurrence of overcurrent damage to the circuit.

[0086] In some embodiments, referring to Figure 3 the schematic structural diagram of the current control circuit shown, the circuit to be sampled includes multiple branches to be sampled, the current control circuit includes multiple current sampling modules, and the voltage division module includes multiple first resistors R1i (the value of i can be 1, 2, 3... n, such as Figure 3 shown, R11, R12, R13... R1n represent the first resistors); the branches to be sampled, the current sampling modules, and the first resistor R1i are in one-to-one correspondence; the target current includes the branch target current of each branch to be sampled collected.

[0087] The first end of each current sampling module is used to connect to the output end of its corresponding branch to be sampled; the second end of each current sampling module is connected to the first end of the second resistor R2 through its corresponding first resistor R1i; the second end of the second resistor R2 is grounded; the second end of each current sampling module is also respectively connected to the first end of the voltage regulation module;

[0088] Each current sampling module is used to collect the branch target current of its corresponding branch to be sampled and output the branch target current to its corresponding first resistor R1i and second resistor R2;

[0089] The voltage regulation module is used to increase the voltage signal at the voltage output terminal when the voltage across the first resistor R1i is greater than or equal to the preset voltage threshold.

[0090] In this embodiment, the voltage regulation module can determine whether the voltage across the first resistor R1i is greater than or equal to the preset voltage threshold. When the voltage across the first resistor R1i is greater than or equal to the preset voltage threshold, through the power supply Vaux, the voltage signal output at the voltage output terminal can be pulled up, thereby triggering the current limiting protection function to avoid excessive current in one branch to be sampled but the total current is not enough to trigger the current limiting protection, resulting in circuit damage.

[0091] At the same time, through the cooperation of the resistance values of each resistor, the current limiting protection function can also be triggered in advance, allowing sufficient action time for the current limiting protection and reducing the occurrence of overcurrent damage to the circuit.

[0092] Optionally, when the voltages across all the first resistors are less than the preset voltage threshold, the voltage signal at the voltage output terminal is not raised. The voltage output terminal is used to superimpose all the branch target currents (the sum of the currents of the circuit to be sampled), convert the superimposed current into a corresponding voltage signal, and output it to the control module.

[0093] The current control circuit provided in this embodiment includes the following states:

[0094] (1) When the voltages across all the first resistors do not reach (are less than) the preset voltage threshold, that is, the voltage signal at the voltage output terminal is not raised, the voltage output terminal directly transmits the sum of all the branch target currents (the sum of the currents) collected to the control module.

[0095] a. When the sum of the currents does not exceed the current limit value, the control module adjusts the circuit to be sampled according to the sampled current.

[0096] b. When the sum of the currents exceeds the current limit value, the control module performs and completes the current limiting protection action according to the sum of the currents.

[0097] (2) When there is a voltage across a first resistor that reaches (is greater than or equal to) the preset voltage threshold, the voltage signal at the voltage output terminal is raised to trigger the current limiting protection. Among them, by adjusting the preset voltage threshold, it is also possible to trigger the current limiting protection in advance and perform and complete the current limiting protection action before the target current exceeds the current limit value.

[0098] In some embodiments, as Figure 3 shown, the voltage regulation module includes a first switching transistor Q1, a second switching transistor Q2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and a plurality of first diodes D1i; among them, the current sampling module corresponds to the first diode D1i one by one.

[0099] Each current sampling module is connected to the anode of its corresponding first diode D1i, and the cathode of each first diode D1i is connected to the connection point of its corresponding first resistor R1i and second resistor R2 through the series-connected third resistor R3 and fourth resistor R4; the connection point of the third resistor R3 and the fourth resistor R4 is also connected to the control terminal of the first switching transistor Q1; the first end of the first switching transistor Q1 is connected to the power supply Vaux through the fifth resistor R5 and to the control terminal of the second switching transistor Q2 through the sixth resistor R6; the second end of the first switching transistor Q1 is connected to the connection point of the first resistor R1i and the second resistor R2; the first end of the second switching transistor Q2 is connected to the power supply Vaux, and the second end of the second switching transistor Q2 is connected to the voltage output terminal Vcs through the seventh resistor R7.

[0100] Here, the value of i can be 1, 2, 3... n, as Figure 3As shown, R11, R12, R13... R1n represent the first resistors, and D11, D12, D13... D1n represent the first diodes.

[0101] In this embodiment, the third resistor R3 and the fourth resistor R4 are connected in parallel with the corresponding first resistor R1i through each first diode D1i. Due to the reverse cut-off effect of the diode, the voltage across the third resistor R3 and the fourth resistor R4 is the maximum voltage among all the first resistors R1i, so that the voltage regulation module can detect the maximum branch target current collected by the current sampling module and judge the maximum voltage in the first resistor R1i.

[0102] In some embodiments, the voltage division module further includes a ninth resistor R9 and a capacitor C1.

[0103] The connection point of the first resistor R1i and the second resistor R2 is connected to the first end of the first capacitor C1, the third end of the voltage regulation module, and the control module through the ninth resistor R9; the second end of the first capacitor C1 is grounded.

[0104] In this embodiment, filtering is performed through the ninth resistor R9 and the first capacitor C1 to remove high-frequency noise and interference, making the voltage sampling signal smoother and more stable, and ensuring the control effect of the control module on the circuit to be sampled. At the same time, when the second switching transistor Q2 is turned on, the voltage of the power supply is divided by the seventh resistor R7, the ninth resistor R9, and the second resistor R2, and the voltage output terminal outputs the voltage of the ninth resistor R9 and the second resistor R2, so that the output voltage signal is relatively high and can trigger current limiting protection.

[0105] Here, the resistance value of the first resistor R1i can be one order of magnitude higher than that of the second resistor R2 to ensure sufficient sampling accuracy. For example, the resistance value of the first resistor R1i is 100 Ω, the resistance value of the second resistor R2 is 4.7 Ω, and the ratio of the resistance value of the first resistor R1i to that of the second resistor R2 is about 20.

[0106] In addition, the sum of the resistance values of the ninth resistor R9 and the second resistor R2 can be one order of magnitude higher than that of the seventh resistor R7, so as to raise the voltage signal of the voltage output terminal when the second switching transistor Q2 is turned on. For example, the ratio range of the sum of the resistance values of the ninth resistor R9 and the second resistor R2 to the resistance value of the seventh resistor R7 can be 4 to 10. In a specific embodiment, the resistance value of the second resistor R2 is 4.7 Ω, the resistance value of the ninth resistor R9 is 510 Ω, the resistance value of the seventh resistor R7 is 100 Ω, the sum of the resistance values of the ninth resistor R9 and the second resistor R2 is about 515 Ω, and the ratio of this sum value to the resistance value of the seventh resistor R7 is about 5.15.

[0107] The current control circuit has been introduced in detail above for the to-be-sampled circuit including multiple branches. Among them, by sampling the sum of currents and detecting the maximum voltage across each first resistor, timely and effective current limiting protection is achieved. Next, a specific introduction will be made for another feasible method.

[0108] With the idea of reducing the possibility of overcurrent damage to the circuit, the inventor also considered converting the branch target current of each branch in the to-be-sampled circuit collected into a voltage, and screening out the maximum voltage among them as the voltage sampling signal for output. That is, by collecting the branch target current of each branch in the to-be-sampled circuit, using the maximum branch target current for current limiting protection, to avoid the situation of circuit damage caused by excessive current in one branch, and trigger the current limiting protection of the multi-tube flyback circuit in a timely and accurate manner.

[0109] In some embodiments, as Figure 4 shown, the voltage division module further includes an eighth resistor R8, a plurality of sampling resistors R0i, and a plurality of second diodes D2i (the value of i can be 1, 2, 3... n, as Figure 4 shown, R01, R02, R03... R0n represent sampling resistors, and D21, D22, D23... D2n represent second diodes); the voltage regulation module includes a plurality of first ends and a plurality of second ends; among them, the current sampling module, the sampling resistor R0i, and the second diode D2i are in one-to-one correspondence; the first end and the second end of the voltage regulation module are in one-to-one correspondence with the current sampling module.

[0110] The second end of each current sampling module is connected to the anode of its corresponding second diode D2i and one end of its corresponding sampling resistor R0i through its corresponding first resistor R1i; the other end of each sampling resistor R0i is grounded; the cathode of each second diode D2i is connected to the first end of the second resistor R2 through the eighth resistor R8; the second end of the second resistor R2 is grounded; the second end of each current sampling module is also respectively connected to the first end of its corresponding voltage regulation module, and each second end of the voltage regulation module is respectively connected to the connection point of its corresponding first resistor R1i and second diode D2i.

[0111] In this embodiment, the sampling resistor R0i can convert the branch target current collected by its corresponding current sampling module into a voltage for output. The plurality of second diodes D2i form a common cathode diode. Through the common cathode second diodes D2i, the screening of the maximum voltage corresponding to each current sampling module can be realized, so that the subsequent control chip can perform accurate current limiting control according to the maximum voltage, and avoid the situation of overcurrent damage to the circuit caused by excessive current in one primary winding.

[0112] Among them, the cathode connection of each second diode D2i is connected to the first end of the second resistor R2 through the eighth resistor R8, that is, the cathode voltages of the second diodes D2i are the same. Therefore, the second diode D2i with the highest voltage will conduct, and the other second diodes D2i with lower voltages cannot meet the conduction conditions, thereby screening out the maximum branch target current.

[0113] The voltage regulation module can be determined for each current sampling module to judge whether there is a voltage across the first resistor corresponding to the current sampling module that is greater than or equal to a preset voltage threshold. When there is a voltage across the first resistor that is greater than or equal to the preset voltage threshold, the voltage signal output from the voltage output terminal is pulled high to trigger current limiting protection.

[0114] In addition, a second capacitor C2 can be provided in parallel with the second resistor R2 in the voltage division module to filter the output voltage signal.

[0115] Optionally, as Figure 4 shown, the voltage regulation module may also include a plurality of first switching transistors Q1i, a plurality of third resistors R3i, and a plurality of fourth resistors R4i. The voltage regulation module further includes a second switching transistor Q2, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; among them, the current sampling module corresponds one-to-one with the first switching transistor Q1i, the third resistor R3i, and the fourth resistor R4i. Here, the value of i can be 1, 2, 3... n, Q11, Q12, Q13... Q1n are the first switching transistors, R31, R32, R33... R3n represent the third resistors, and R41, R42, R43... R4n are the fourth resistors.

[0116] Each current sampling module is connected to the connection point of its corresponding first resistor R1i and second diode D2i through its corresponding series-connected third resistor R3i and fourth resistor R4i; the connection point of each series-connected third resistor R3i and fourth resistor R4i is also connected to the control terminal of its corresponding first switching transistor Q1i; the first end of each first switching transistor Q1i is connected to the power supply Vaux through the fifth resistor R5 and to the control terminal of the second switching transistor Q2 through the sixth resistor R6; the second end of each first switching transistor Q1i is connected to the connection point of its corresponding first resistor R1i and second resistor R2; the first end of the second switching transistor Q2 is connected to the power supply Vaux, and the second end of the second switching transistor Q2 is connected to the voltage output terminal Vcs through the seventh resistor R7.

[0117] Here, each first switching transistor Q1i judges the voltage across the corresponding first resistor R1i. When the voltage across the first resistor reaches (is greater than or equal to) the preset voltage threshold, the second switching transistor Q2 is controlled to conduct, and the voltage signal of the voltage output terminal Vcs is pulled high. For specific details, reference can be made to the description in the above embodiments, which will not be elaborated here.

[0118] In some embodiments, the resistance value of the second resistor R2 can be made as large as possible so that the voltage signal across it is as large as possible, in order to be able to ignore the voltage drop of the second diode D2i and ensure the accuracy of the sampled voltage.

[0119] In addition, the ratio of the sum of the resistance values of the eighth resistor R8 and the second resistor R2 to the resistance value of a sampling resistor R0i is a preset multiple.

[0120] In this embodiment, the sum of the resistance values of the eighth resistor R8 and the second resistor R2 can be one order of magnitude higher than the resistance value of a sampling resistor R0i to ensure sufficient sampling accuracy. For example, the ratio range of the sum of the resistance values of the eighth resistor R8 and the second resistor R2 to the resistance value of a sampling resistor R0i can be 8 to 50.

[0121] In a specific embodiment, the resistance value of the eighth resistor R8 can be 50 Ω, the resistance value of the second resistor R2 can be 2400 Ω, and the resistance value of a sampling resistor R0i can be 100 Ω, that is, the ratio of the sum of the resistance values of the eighth resistor R8 and the second resistor R2 to the resistance value of a sampling resistor R0i is 29.

[0122] In some embodiments, taking the four-switch flyback circuit as the circuit to be sampled as an example for illustration, a current control circuit as shown in Figure 3 is adopted. Four current sampling modules are arranged in the corresponding current control circuit to sample the branch target current. Exemplarily, the primary side currents of the four primary side windings in the four-switch flyback circuit are Ip1, Ip2, Ip3, and Ip4.

[0123] Correspondingly, the sampled branch target current flows through the first resistors R11, R12, R13, and R14, and is converted into voltages VR1 (the voltage across the first resistor R11), VR2 (the voltage across the first resistor R12), VR3 (the voltage across the first resistor R13), and VR4 (the voltage across the first resistor R14).

[0124] For more intuitive comparison, voltage signals are used for display, and there will be a voltage threshold corresponding to the preset threshold. As shown in Figure 5 , Vset in the figure is the voltage threshold corresponding to the preset threshold. The voltage VR1 is greater than the voltage threshold Vset, and the voltages VR2, VR3, and VR4 are not greater than the voltage threshold Vset, that is, only the first branch target current is greater than the preset threshold. The detection module controls the adjustment module to work, increases the first current, and the voltage sampling signal Vcs output by the voltage conversion unit is directly pulled high and is no longer a normal sampling triangular waveform, which can realize the current limiting protection function of the PWM control chip in a timely manner.

[0125] The present application also provides a flyback circuit and a switching power supply. For details not described in detail herein, reference may be made to the corresponding circuit embodiments above.

[0126] In some embodiments, the flyback circuit may include the current control circuit in any of the above embodiments.

[0127] In this embodiment, a current transformer is provided in the current sampling module of the current control circuit to sample the current using the current transformer. The primary winding of the current transformer CT may be connected in series with the primary winding of the transformer in the flyback circuit to sample the primary current. The voltage output terminal Vcs of the current control circuit is connected to the PWM control chip (control module) of the flyback circuit, and is used to input the voltage sampling signal into the PWM control chip, so that the PWM control chip performs control according to the voltage sampling signal.

[0128] The flyback circuit may be a multi-switch flyback circuit. Among them, the primary winding of each transformer in the multi-switch flyback circuit may be a branch to be sampled. In the current control circuit, a current transformer is respectively provided in each current sampling module to collect the branch target current of the primary winding of each transformer using the current transformer.

[0129] In some embodiments, the switching power supply may include the flyback circuit as described above.

[0130] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not described or recorded in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0131] The above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they may still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A current control circuit, characterized in that, It includes a current sampling module, a voltage dividing module, and a voltage regulating module; wherein, the voltage dividing module includes a first resistor and a second resistor; The first end of the current sampling module is used to connect the circuit to be sampled, and the second end of the current sampling module is grounded through the series-connected first resistor and second resistor; the connection point of the first resistor and the second resistor is connected to the voltage output end, and the voltage output end is used to connect the control module; The second end of the current sampling module is also connected to the first end of the voltage regulating module; the second end of the voltage regulating module is connected to the connection point of the first resistor and the second resistor; the third end of the voltage regulating module is connected to the voltage output end; The current sampling module is used to collect the target current of the circuit to be sampled and output the target current to the first resistor and the second resistor; The voltage regulating module is used to increase the voltage signal at the voltage output end when the voltage across the first resistor is greater than or equal to the preset voltage threshold, and the voltage output end is used to output the increased voltage signal to the control module, so that the control module can perform current limiting protection on the circuit to be sampled when the voltage sampling signal exceeds the voltage threshold corresponding to the current limiting value.

2. The current control circuit according to claim 1, wherein The voltage regulating module includes a first switching tube, a second switching tube, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor; The current sampling module is connected to the connection point of the first resistor and the second resistor through the series-connected third resistor and fourth resistor; The connection point of the third resistor and the fourth resistor is also connected to the control end of the first switching tube; The first end of the first switching tube is connected to the power supply through the fifth resistor and to the control end of the second switching tube through the sixth resistor; the second end of the first switching tube is connected to the connection point of the first resistor and the second resistor; The first end of the second switching tube is connected to the power supply, and the second end of the second switching tube is connected to the voltage output end through the seventh resistor.

3. The current control circuit according to claim 1, wherein The circuit to be sampled includes multiple branches to be sampled, the current control circuit includes multiple current sampling modules, and the voltage dividing module includes multiple first resistors; the branches to be sampled, the current sampling modules, and the first resistors are in one-to-one correspondence; the target current includes the branch target current of each branch to be sampled collected; The first end of each current sampling module is used to connect the output end of its corresponding branch to be sampled; the second end of each current sampling module is connected to the first end of the second resistor through its corresponding first resistor; the second end of the second resistor is grounded; the second end of each current sampling module is also respectively connected to the first end of the voltage regulating module; Each current sampling module is used to collect the branch target current of its corresponding branch to be sampled and output the branch target current to its corresponding first resistor and second resistor; The voltage regulating module is used to increase the voltage signal at the voltage output end when there is a voltage across the first resistor greater than or equal to the preset voltage threshold.

4. The current control circuit according to claim 3, wherein The voltage regulation module includes a first switching transistor, a second switching transistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and a plurality of first diodes; wherein, the current sampling modules correspond to the first diodes one by one; Each current sampling module is connected to the anode of its corresponding first diode, and the cathode of each first diode is connected to the connection point of its corresponding first resistor and second resistor through the serially connected third resistor and fourth resistor; The connection point of the third resistor and the fourth resistor is also connected to the control terminal of the first switching transistor; The first terminal of the first switching transistor is connected to the power supply through the fifth resistor and to the control terminal of the second switching transistor through the sixth resistor; the second terminal of the first switching transistor is connected to the connection point of the first resistor and the second resistor; The first terminal of the second switching transistor is connected to the power supply, and the second terminal of the second switching transistor is connected to the voltage output terminal through the seventh resistor.

5. The current control circuit according to claim 3, characterized in that, The voltage dividing module further includes an eighth resistor, a plurality of sampling resistors, and a plurality of second diodes; the voltage regulation module includes a plurality of first terminals and a plurality of second terminals; wherein, the current sampling modules, the sampling resistors, and the second diodes correspond to each other one by one; the first terminals and the second terminals of the voltage regulation module correspond to the current sampling modules one by one; The second terminal of each current sampling module is connected to the anode of its corresponding second diode and one end of its corresponding sampling resistor through its corresponding first resistor; the other end of each sampling resistor is grounded; The cathode of each second diode is connected to the first terminal of the second resistor through the eighth resistor; the second terminal of the second resistor is grounded; The second terminal of each current sampling module is also respectively connected to the first terminal of its corresponding voltage regulation module, and each second terminal of the voltage regulation module is respectively connected to the connection point of its corresponding first resistor and second diode.

6. The current control circuit according to claim 5, wherein The voltage regulation module includes a plurality of first switching transistors, a plurality of third resistors, and a plurality of fourth resistors, and the voltage regulation module further includes a second switching transistor, a fifth resistor, a sixth resistor, and a seventh resistor; wherein, the current sampling modules correspond to the first switching transistors, the third resistors, and the fourth resistors one by one; Each current sampling module is connected to the connection point of its corresponding first resistor and second diode through its corresponding serially connected third resistor and fourth resistor; The connection point of each serially connected third resistor and fourth resistor is also connected to the control terminal of its corresponding first switching transistor; The first terminal of each first switching transistor is connected to the power supply through the fifth resistor and to the control terminal of the second switching transistor through the sixth resistor; the second terminal of each first switching transistor is connected to the connection point of its corresponding first resistor and the second resistor; The first terminal of the second switching transistor is connected to the power supply, and the second terminal of the second switching transistor is connected to the voltage output terminal through the seventh resistor.

7. The current control circuit according to any one of claims 1 to 4, characterized in that The voltage dividing module further includes a ninth resistor and a first capacitor; The connection point of the first resistor and the second resistor is connected to the first terminal of the first capacitor, the third terminal of the voltage regulation module, and the control module through the ninth resistor; The second terminal of the first capacitor is grounded.

8. The current control circuit according to any one of claims 1 to 6, characterized in that, The current sampling module includes a current transformer and an absorption unit; The primary winding of the current transformer is connected in series with the winding at the output end of the circuit to be sampled; The same-named end of the secondary winding of the current transformer is connected to the first end of the absorption unit; The second end of the absorption unit is grounded through the first resistor and the second resistor connected in series; The different-named end of the secondary winding of the current transformer and the third end of the absorption unit are grounded.

9. A flyback circuit, characterized in that, It includes the current control circuit according to any one of claims 1 to 8 above.

10. A switching power supply, characterized in that, It includes the flyback circuit according to claim 9 above.

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