Current limiting circuit control method and current limiting circuit

Abstract

The invention provides a current limiting circuit control method, which comprises the following steps that: when and only when a voltage signal converted by a primary side current sampling circuit is greater than a first reference voltage and / or a voltage signal converted by a secondary side current sampling circuit is greater than a third reference voltage, a single chip microcomputer circuit keeps the current frequency of a PWM (Pulse-Width Modulation) driving signal; when the voltage signal converted by the primary side current sampling circuit is smaller than or equal to the first reference voltage and the voltage signal converted by the secondary side current sampling circuit is smaller than or equal to the third reference voltage, the influence factors of the PWM driving signal frequency comprise the input voltage and the output load. When and only when the voltage signal is greater than the first reference voltage and / or the third reference voltage, the single-chip microcomputer circuit maintains the frequency of the current PWM driving signal, on one hand, the working process of the load is not affected, and on the other hand, large impact of the current on a power device can be avoided due to the fact that the gain is kept unchanged. The invention further provides a current limiting circuit adopting the current limiting circuit control method.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply, and more specifically, to a current limiting circuit control method and a current limiting circuit. Background Art

[0002] With the continuous development of soft switching technology, LLC resonant converter has been widely used in industry, new energy vehicles, energy storage industry and other occasions due to its excellent soft switching performance and high efficiency.

[0003] Under dynamic load, there will be transient impact current in the primary current when the dynamic load is switched. Large impact current will affect the stability of the power device and even damage the power device, so the circuit needs to be current limited.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] One object of the present invention is to overcome the shortcomings of the prior art and provide a current limiting circuit control method. When the voltage signal is greater than the first reference voltage or the third reference voltage, the single-chip microcomputer circuit maintains the frequency of the current PWM drive signal. On the one hand, it will not affect the working process of the load. On the other hand, since the gain remains unchanged, it can also avoid the current from having a large impact on the power device.

[0006] A second object of the present invention is to provide a current limiting circuit using the current limiting circuit control method.

[0007] To achieve the first purpose, the basic concept of the technical solution adopted by the present invention is:

[0008] A current limiting circuit control method, when and only when the voltage signal converted by the primary current sampling circuit is greater than a first reference voltage and / or the voltage signal converted by the secondary current sampling circuit is greater than a third reference voltage, the single chip microcomputer circuit maintains the current frequency of the PWM drive signal;

[0009] When the voltage signal converted by the primary current sampling circuit is less than or equal to the first reference voltage and the voltage signal converted by the secondary current sampling circuit is less than or equal to the third reference voltage, the factors affecting the frequency of the PWM drive signal include the input voltage and the output load.

[0010] Furthermore, when the voltage signal converted by the primary current sampling circuit is greater than the second reference voltage and / or the voltage signal converted by the secondary current sampling circuit is greater than the fourth reference voltage, the single chip microcomputer circuit turns off the PWM driving signal.

[0011] Furthermore, the second reference voltage is greater than the first reference voltage, and the fourth reference voltage is greater than the third reference voltage.

[0012] Furthermore, after the PWM drive signal is turned off for a set time, the single-chip microcomputer circuit restarts the PWM drive signal;

[0013] Preferably, the single chip microcomputer circuit starts the PWM drive signal at a maximum frequency.

[0014] To achieve the second purpose, the basic concept of the technical solution adopted by the present invention is:

[0015] A current limiting circuit adopts the current limiting circuit control method mentioned above.

[0016] Furthermore, it includes a primary current sampling circuit and a secondary current sampling circuit for collecting current, the first output terminal and the second output terminal of the primary current sampling circuit are respectively connected to the first comparator and the second comparator, the third output terminal and the fourth output terminal of the secondary current sampling circuit are respectively connected to the third comparator and the fourth comparator, and the output terminal of any comparator is connected to the single-chip computer circuit.

[0017] Further, both ends of the input capacitor are connected to the LLC switch circuit, one end of the LLC switch circuit is connected to the primary side of the transformer, the secondary side of the transformer is connected to the rectifier circuit, the first filter output capacitor and the second filter output capacitor are connected in parallel, and both are connected to the rectifier circuit;

[0018] The primary current sampling circuit is used to collect the current of the resonant network of the LLC switching circuit, and the secondary current sampling circuit is used to collect the current of the secondary side of the transformer.

[0019] Furthermore, the resonant network includes a resonant inductor, an excitation inductor and a resonant capacitor connected in series, and the secondary side of the transformer is connected in parallel with the excitation inductor.

[0020] Furthermore, the LLC switch circuit further includes a full-bridge circuit, and the full-bridge circuit includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube connected in series respectively;

[0021] The first switch tube and the third switch tube, and the second switch tube and the fourth switch tube are all connected through a resonant network.

[0022] Furthermore, the first switch tube and the third switch tube are turned on or off at the same time;

[0023] The second switch tube and the fourth switch tube are turned on or off at the same time.

[0024] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0025] 1. In the current limiting circuit control method of the present invention, when and only when the voltage signal is greater than the first reference voltage and / or the third reference voltage, the single-chip microcomputer circuit maintains the frequency of the current PWM drive signal. On the one hand, it will not affect the working process of the load. On the other hand, since the gain remains unchanged, it can also avoid the current from having a large impact on the power device.

[0026] 2. When the voltage signal is greater than the first reference voltage and / or the third reference voltage, if the current further increases to the point where the voltage signal is greater than the second reference voltage and / or the fourth reference voltage, the microcontroller circuit turns off the PWM drive signal to prevent the current from having a large impact on the power device.

[0027] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the accompanying drawings:

[0029] Figure 1 is a flow chart of an embodiment of a current limiting circuit control method of the present invention;

[0030] Figure 2 It is a structural schematic diagram of the current limiting circuit of the present invention.

[0031] The main components in the figure are: 1. Input capacitor; 2. LLC switching circuit; 201. First switch tube; 202. Second switch tube; 203. Third switch tube; 204. Fourth switch tube; 205. Resonant inductor; 206. Excitation inductor; 207. Resonant capacitor; 3. Transformer; 4. Rectifier circuit; 5. First filter output capacitor; 6. Second filter output capacitor; 7. Primary current transformer; 8. Secondary current transformer; 9. First comparator; 10. Second comparator; 11. Third comparator; 12. Fourth comparator; 13. Microcontroller circuit.

[0032] It should be noted that the drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0034] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings, and are 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 direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0035] 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 a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] LLC resonant converter has been widely used in industry, new energy vehicles and other occasions due to its excellent soft switching performance. When the load is dynamic, the primary current will have a transient impact current when the dynamic load is switched. The large impact current will affect the stability of the power device and even damage the power device, so the circuit needs to be current limited.

[0037] The present invention provides a current limiting circuit control method, wherein the current limiting circuit comprises a primary current sampling circuit and a secondary current sampling circuit for collecting current. In the present invention, both the primary current sampling circuit and the secondary current sampling circuit can convert the collected current signal into a voltage signal, wherein the first output end and the second output end of the primary current sampling circuit are respectively connected to a first comparator 9 and a second comparator 10, and the third output end and the fourth output end of the secondary current sampling circuit are respectively connected to a third comparator 11 and a fourth comparator 12, and the output end of any comparator is connected to a single-chip computer circuit 13.

[0038] The comparator is used to compare the voltage signal output by the primary current sampling circuit or the secondary current sampling circuit with the reference voltage. When the voltage signal is less than or equal to the reference voltage, the comparator outputs a low level. When the voltage signal is greater than the reference voltage, the comparator outputs a high level. The single-chip microcomputer circuit 13 adjusts the frequency of the PWM drive signal used to drive the LLC switch circuit 2 or directly turns off the PWM drive signal according to the high level or low level output by the comparator to ensure the reliability of the current limiting circuit.

[0039] Specifically, in the present invention, when the voltage signal converted by the primary current sampling circuit is less than or equal to the first reference voltage and the voltage signal converted by the secondary current sampling circuit is less than or equal to the third reference voltage, the single-chip microcomputer circuit 13 provides a PWM drive signal for driving the LLC switching circuit 2. At this time, the factors affecting the frequency of the PWM drive signal include the input voltage and the output load.

[0040] When and only when the voltage signal converted by the primary current sampling circuit is greater than the first reference voltage and / or the voltage signal converted by the secondary current sampling circuit is greater than the third reference voltage, the single-chip microcomputer circuit 13 maintains the current frequency of the PWM drive signal and does not change with the input voltage and output load. At this time, the voltage signal converted by the primary current sampling circuit is less than the second reference voltage and the voltage signal converted by the secondary current sampling circuit is less than the fourth reference voltage. Since the single-chip microcomputer circuit 13 still provides the PWM drive signal for driving the LLC switch circuit 2, the working process of the load will not be affected, and the frequency of the PWM drive signal remains unchanged, that is, the gain of the LLC switch circuit 2 remains unchanged, avoiding the power device in the circuit from being subjected to a large current shock as the gain increases.

[0041] If the output load decreases, the corresponding input voltage also decreases. Since the gain of the LLC switching circuit 2 remains unchanged, the current in the circuit will decrease until the voltage signal converted by the primary current sampling circuit is less than or equal to the first reference voltage and the voltage signal converted by the secondary current sampling circuit is less than or equal to the third reference voltage. The current limiting circuit resumes PID regulation, and the frequency of the PWM drive signal changes again with the changes in the input voltage and output load.

[0042] When the output load increases, the input voltage will also increase, and since the gain of the LLC switch circuit 2 remains unchanged, the current in the circuit will increase.

[0043] In the present invention, the second reference voltage of the second comparator 10 connected to the primary current sampling circuit is greater than the first reference voltage of the first comparator 9, and the fourth reference voltage of the fourth comparator 12 connected to the secondary current sampling circuit is greater than the third reference voltage of the third comparator 11.

[0044] As the output load increases, when the voltage signal converted by the primary current sampling circuit is greater than the second reference voltage and / or the voltage signal converted by the secondary current sampling circuit is greater than the fourth reference voltage, the single-chip microcomputer circuit 13 turns off the PWM drive signal to prevent the electrical components from suffering a large current shock.

[0045] After the PWM driving signal is turned off for a set time, the single chip microcomputer circuit 13 restarts the PWM driving signal, and the LLC switch circuit 2 resumes operation.

[0046] In one embodiment of the present invention, in order to avoid excessive current in the circuit, the single-chip microcomputer circuit 13 starts the PWM drive signal at the maximum frequency. At this time, the gain of the LLC switch circuit 2 is small and will not produce a large current impact on the power device. Then the single-chip microcomputer circuit 13 adjusts the frequency of the PWM drive signal according to the input voltage and output load.

[0047] In the present invention, the first comparator 9, the second comparator 10, the third comparator 11 and the fourth comparator 12 can feed back a high level or a low level to the single chip computer circuit 13 at the same time, or can feed back to the single chip computer circuit 13 in sequence.

[0048] like Figure 1 As shown, in one embodiment of the present invention, the second comparator 10 and the fourth comparator 12 firstly feed back to the single-chip microcomputer circuit 13. If the second comparator 10 and / or the fourth comparator 12 outputs a high level, the single-chip microcomputer circuit 13 turns off the PWM drive signal to protect the circuit.

[0049] If the second comparator 10 and the fourth comparator 12 both output low levels, the single chip computer circuit 13 further determines the output signals of the first comparator 9 and the third comparator 11;

[0050] If both the first comparator 9 and the third comparator 11 output low levels, the frequency of the PWM drive signal provided by the single-chip circuit 13 changes with the input voltage and the output load;

[0051] If the first comparator 9 and / or the third comparator 11 outputs a high level, in order to avoid affecting the working progress of the load, the single-chip microcomputer circuit 13 maintains the current frequency of the PWM drive signal until the first comparator 9 and the third comparator 11 both output a low level. The single-chip microcomputer circuit 13 adjusts the frequency of the PWM drive signal accordingly according to the changes in the input voltage and the output load.

[0052] like Figure 2 As shown, the present invention also provides a current limiting circuit using the above-mentioned current limiting circuit control method, wherein both ends of the input capacitor 1 are connected to the LLC switching circuit 2, one end of the LLC switching circuit 2 is connected to the primary side of the transformer 3, the secondary side of the transformer 3 is connected to the rectifier circuit 4, the rectifier circuit 4 is used to convert alternating current into direct current, the first filter output capacitor 5 and the second filter output capacitor 6 are connected in parallel, and both are connected to the rectifier circuit 4.

[0053] The current limiting circuit of the present invention also includes a primary current sampling circuit and a secondary current sampling circuit for collecting current. The first output end and the second output end of the primary current sampling circuit are respectively connected to the first comparator 9 and the second comparator 10, and the third output end and the fourth output end of the secondary current sampling circuit are respectively connected to the third comparator 11 and the fourth comparator 12, and the output end of any comparator is connected to the single-chip computer circuit 13.

[0054] The primary current sampling circuit includes a primary current transformer 7, which is used to collect the current of the resonant network of the LLC switching circuit 2; the secondary current sampling circuit includes a secondary current transformer 8, which is used to collect the current of the secondary side of the transformer 3.

[0055] The resonant network of the LLC switch circuit 2 includes a resonant inductor 205 , an excitation inductor 206 and a resonant capacitor 207 connected in series, wherein the excitation inductor 206 is connected in parallel with the secondary side of the transformer 3 .

[0056] The LLC switch circuit 2 also includes a full-bridge circuit, which includes a first switch tube 201, a second switch tube 202, a third switch tube 203, and a fourth switch tube 204 connected in series, respectively, wherein the first switch tube 201 and the third switch tube 203, the second switch tube 202 and the fourth switch tube 204 are all connected through a resonant network.

[0057] The PWM drive signal provided by the single chip microcomputer circuit 13 is used to control the opening or closing of the first switch tube 201, the second switch tube 202, the third switch tube 203 and the fourth switch tube 204, wherein the first switch tube 201 and the third switch tube 203 are opened or closed at the same time, and the second switch tube 202 and the fourth switch tube 204 are opened or closed at the same time.

[0058] Compared with when the second switch tube 202 and the fourth switch tube 204 are turned on, the direction of the current in the circuit is opposite when the first switch tube 201 and the third switch tube 203 are turned on, thereby converting direct current into alternating current.

[0059] In one embodiment of the present invention, the working process of the current limiting circuit is:

[0060] The first comparator 9, the second comparator 10, the third comparator 11 and the fourth comparator 12 simultaneously feed back to the single chip microcomputer circuit 13, and the single chip microcomputer circuit 13 controls the PWM driving signal provided by it according to the received feedback signal. Specifically,

[0061] When the first comparator 9 and the third comparator 11 both output low levels, the single chip microcomputer circuit 13 does not perform current limiting action. At this time, the single chip microcomputer circuit 13 adjusts the frequency of the PWM driving signal for driving the LLC switch circuit 2 according to the changes in the input voltage and the output load.

[0062] When and only when the first comparator 9 and / or the third comparator 11 outputs a high level, to avoid affecting the working process of the load, the single chip circuit 13 maintains the current frequency of the PWM drive signal. At this time, the second comparator 10 and the fourth comparator 12 both output a low level.

[0063] When the output load decreases, since the gain of the LLC switch circuit 2 remains unchanged, the current in the circuit decreases accordingly, until the first comparator 9 and the third comparator 11 both output a low level, the current limiting circuit resumes PID regulation, and the single-chip microcomputer circuit 13 adjusts the frequency of the PWM drive signal according to the input voltage and the output load.

[0064] Since the second reference voltage is greater than the first reference voltage and the third reference voltage is greater than the fourth reference voltage, if the current in the circuit continues to increase, the second comparator 10 and / or the fourth comparator 12 will output a high level. At this time, the current in the circuit is large, which will produce a large current impact on the power device. The single-chip computer circuit 13 turns off the PWM drive signal to avoid affecting the reliability of the current limiting circuit.

[0065] After the PWM driving signal is turned off for a set time, the single chip microcomputer circuit 13 restarts the PWM driving signal at the maximum frequency.

[0066] In another embodiment of the present invention, since the second reference voltage and the fourth reference voltage are relatively high, if the second comparator 10 and / or the fourth comparator 12 output a high level, it means that the current in the circuit is relatively large at this time, and the PWM drive signal needs to be turned off in time to avoid danger; if the second comparator 10 and the fourth comparator 12 both output a low level, the current in the current limiting circuit is relatively small at this time, and no danger will occur. The single-chip computer circuit 13 can further receive feedback signals from the first comparator 9 and the third comparator 11 for judgment. Specifically,

[0067] The second comparator 10 and the fourth comparator 12 firstly feed back to the single chip microcomputer circuit 13. If the second comparator 10 and / or the fourth comparator 12 outputs a high level, the single chip microcomputer circuit 13 turns off the PWM driving signal to protect the circuit.

[0068] If the second comparator 10 and the fourth comparator 12 both output low levels, the single chip computer circuit 13 further determines the output signals of the first comparator 9 and the third comparator 11;

[0069] If both the first comparator 9 and the third comparator 11 output low levels, the frequency of the PWM drive signal provided by the single-chip circuit 13 changes with the input voltage and the output load;

[0070] If the first comparator 9 and / or the third comparator 11 outputs a high level, in order to avoid affecting the operation of the load, the single-chip microcomputer circuit 13 maintains the current frequency of the PWM drive signal until the first comparator 9 and the third comparator 11 both output a low level. The single-chip microcomputer circuit 13 adjusts the frequency of the PWM drive signal accordingly according to changes in the input voltage and the output load.

[0071] The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical content suggested above without departing from the scope of the technical solution of the present invention. The implementation scheme in the above embodiment can be further combined or replaced. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the solution of the present invention.

Claims

1. A current limiting circuit control method, characterized in that: The single-chip circuit maintains the current frequency of the PWM drive signal when and only when the voltage signal converted by the primary current sampling circuit is greater than the first reference voltage and / or the voltage signal converted by the secondary current sampling circuit is greater than the third reference voltage; When the voltage signal converted by the primary current sampling circuit is less than or equal to the first reference voltage and the voltage signal converted by the secondary current sampling circuit is less than or equal to the third reference voltage, the factors affecting the frequency of the PWM drive signal include the input voltage and the output load.

2. A current limiting circuit control method according to claim 1, characterized in that: When the voltage signal converted by the primary current sampling circuit is greater than the second reference voltage and / or the voltage signal converted by the secondary current sampling circuit is greater than the fourth reference voltage, the single chip circuit turns off the PWM driving signal.

3. A current limiting circuit control method according to claim 2, characterized in that: The second reference voltage is greater than the first reference voltage, and the fourth reference voltage is greater than the third reference voltage.

4. A current limiting circuit control method according to claim 2, characterized in that: After the PWM drive signal is turned off for a set time, the single chip microcomputer circuit restarts the PWM drive signal; Preferably, the single chip microcomputer circuit starts the PWM drive signal at a maximum frequency.

5. A current limiting circuit, characterized in that: A current limiting circuit control method as described in any one of claims 1 to 4 is adopted.

6. A current limiting circuit according to claim 5, characterized in that: It includes a primary current sampling circuit and a secondary current sampling circuit for collecting current. The first output terminal and the second output terminal of the primary current sampling circuit are respectively connected to the first comparator and the second comparator. The third output terminal and the fourth output terminal of the secondary current sampling circuit are respectively connected to the third comparator and the fourth comparator. The output terminal of any comparator is connected to the single-chip computer circuit.

7. A current limiting circuit according to claim 6, characterized in that: Two ends of the input capacitor are connected to the LLC switch circuit, one end of the LLC switch circuit is connected to the primary side of the transformer, the secondary side of the transformer is connected to the rectifier circuit, the first filter output capacitor and the second filter output capacitor are connected in parallel, and both are connected to the rectifier circuit; The primary current sampling circuit is used to collect the current of the resonant network of the LLC switching circuit, and the secondary current sampling circuit is used to collect the current of the secondary side of the transformer.

8. A current limiting circuit according to claim 7, characterized in that: The resonant network includes a resonant inductor, an excitation inductor and a resonant capacitor connected in series, and the secondary side of the transformer is connected in parallel with the excitation inductor.

9. A current limiting circuit according to claim 7, characterized in that: The LLC switch circuit further includes a full-bridge circuit, which includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube connected in series respectively; The first switch tube and the third switch tube, and the second switch tube and the fourth switch tube are all connected through a resonant network.

10. A current limiting circuit according to claim 9, characterized in that: The first switch tube and the third switch tube are turned on or off at the same time; The second switch tube and the fourth switch tube are turned on or off at the same time.

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