Switching power supply protection circuit

Abstract

The utility model provides a protection circuit of a switching power supply, the protection circuit comprising: a latch circuit, which is arranged in the primary side circuit of the switching power supply, and generates a protection signal when receiving a first signal from the secondary side circuit of the switching power supply, the protection signal causes a control chip in the primary side circuit of the switching power supply to enter a protection mode, a first output terminal of the control chip is connected to a switch element in the primary side circuit of the switching power supply, and controls the conduction and disconnection of the switch element, the latch circuit has a first protection signal output terminal and a second protection signal output terminal, at least one of the first protection signal output terminal and the second protection signal output terminal is connected to the control chip, and the protection signal is output to the control chip through at least one of the first protection signal output terminal and the second protection signal output terminal.

Description

Technical Field

[0001] The embodiments of the present application relate to a switching power supply, and more particularly to a protection circuit of the switching power supply. Background Art

[0002] At present, in the switching power supply, the control integrated circuit (IC), also called the control chip, is set on the primary side to control the on and off of the switching elements in the switching power supply. The switching power supply is usually protected by the protection function of the control IC. The protection function of the control IC includes overvoltage protection, undervoltage protection, overcurrent protection, short circuit protection, overtemperature protection, etc.

[0003] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the utility model and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because these solutions are described in the background technology section of the utility model. Utility Model Content

[0004] The inventors have discovered that there are some defects in using the protection function of the control IC, such as: 1. Due to the need to meet the insulation distance requirements, the protection function of the control IC can only detect the current or voltage on the primary side, and cannot detect the current or voltage on the secondary side; 2. It is impossible to change the protection mode or the protection release method; 3. It is impossible to change the protection threshold.

[0005] In order to solve at least one of the above problems or other similar problems, an embodiment of the utility model provides a protection circuit of a switching power supply. A latching circuit is provided on the primary side of the switching power supply. The latching circuit causes the control IC on the primary side to enter a protection mode according to the signal of the secondary side circuit. Thus, any protection provided by the control IC on the primary side can be used to implement latching protection based on the secondary side signal, thereby expanding the selection range of the control IC and making the design of the protection function of the switching power supply more convenient.

[0006] According to one aspect of an embodiment of the utility model, a protection circuit of a switching power supply is provided, the protection circuit comprising:

[0007] A latch circuit is provided in the primary side circuit of the switching power supply, and generates a protection signal when receiving a first signal from the secondary side circuit of the switching power supply, wherein the protection signal causes a control chip in the primary side circuit of the switching power supply to enter a protection mode, and a first output terminal of the control chip is connected to a switch element in the primary side circuit of the switching power supply to control the on and off of the switch element.

[0008] in,

[0009] The latch circuit has a first protection signal output terminal and a second protection signal output terminal, at least one of the first protection signal output terminal and the second protection signal output terminal is connected to the control chip, and the protection signal is output to the control chip through at least one of the first protection signal output terminal and the second protection signal output terminal.

[0010] In one or more embodiments, the latching loop comprises:

[0011] a control element, which is turned on according to the first signal;

[0012] a first metal oxide semiconductor field effect transistor, which is in a conducting state after the control element is turned on,

[0013] A gate of the first metal oxide semiconductor field effect transistor is connected to the first protection signal output terminal, and a drain of the first metal oxide semiconductor field effect transistor is connected to the second protection signal output terminal.

[0014] In one or more embodiments, the latching loop further comprises:

[0015] The first transistor and the second transistor,

[0016] The collector of the first transistor is connected to the gate of the first metal oxide semiconductor field effect transistor,

[0017] The base of the first transistor is connected to the collector of the second transistor,

[0018] The emitter of the first transistor is connected to a high level,

[0019] The base of the second transistor is connected to the output end of the control element.

[0020] In one or more embodiments, the gate of the first metal oxide semiconductor field effect transistor is connected to the base of the third transistor through a first resistor.

[0021] In one or more embodiments, the first signal is an over-current detection signal and / or an over-voltage detection signal from a secondary side circuit of the switching power supply.

[0022] In one or more embodiments, the protection circuit further includes:

[0023] The overvoltage detection circuit is arranged in the secondary side loop of the switching power supply and outputs the overvoltage detection signal.

[0024] In one or more embodiments, the overvoltage detection circuit includes a voltage regulator tube, which is used to detect the output voltage of the secondary side loop.

[0025] The voltage regulator is connected to the control element of the latch loop. When the output voltage exceeds a first voltage threshold, the voltage regulator is turned on and outputs the overvoltage detection signal to the control element.

[0026] In one or more embodiments, the protection circuit further includes:

[0027] The overcurrent detection circuit is arranged in the secondary side loop of the switching power supply and outputs the overcurrent detection signal.

[0028] In one or more embodiments, the overcurrent detection circuit comprises:

[0029] an amplifying circuit, used for converting the output current of the secondary side circuit into a first voltage; and

[0030] a comparison circuit, which is used to compare the first voltage with a second voltage threshold,

[0031] The comparison circuit is connected to a control element of the latch circuit, and when the first voltage exceeds the second voltage threshold, the comparison circuit outputs the overcurrent detection signal to the control element.

[0032] In one or more embodiments, the overcurrent detection circuit further includes:

[0033] The adjustable voltage stabilizing circuit is connected to the comparison loop and provides the second voltage threshold. The output voltage of the adjustable voltage stabilizing circuit can be adjusted to adjust the second voltage threshold.

[0034] One of the beneficial effects of the embodiment of the utility model is that a latch circuit is provided on the primary side of the switching power supply, and the latch circuit causes the control IC on the primary side to enter a protection mode according to the signal of the secondary side circuit, thereby being able to utilize any protection provided by the control IC on the primary side to implement latch protection based on the secondary side signal, thereby being able to expand the selection range of the control IC and making the design of the protection function of the switching power supply more convenient.

[0035] With reference to the following description and drawings, specific embodiments of the present invention are disclosed in detail, indicating the manner in which the principles of the present invention can be adopted. It should be understood that the embodiments of the present invention are not limited in scope. Within the spirit and scope of the appended claims, the embodiments of the present invention include many changes, modifications and equivalents.

[0036] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The included drawings are used to provide a further understanding of the embodiments of the utility model, which constitute a part of the specification, are used to illustrate the implementation of the utility model, and together with the text description, explain the principle of the utility model. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0038] Figure 1 It is a schematic diagram of the primary side circuit of the switching power supply of the embodiment of the utility model;

[0039] Figure 2 It is a schematic diagram of the secondary side circuit of the switching power supply of the embodiment of the utility model. DETAILED DESCRIPTION

[0040] With reference to the accompanying drawings, the above and other features of the utility model will become apparent through the following description. In the description and the accompanying drawings, specific embodiments of the utility model are specifically disclosed, which show some embodiments in which the principles of the utility model can be adopted. It should be understood that the utility model is not limited to the described embodiments, but rather, the utility model includes all modifications, variations and equivalents within the scope of the attached claims.

[0041] In addition, in the various figures used in the following description, since each structural element is made to be a size that can be recognized on the drawing, the scale varies according to each structural element. The present invention is not limited to the number of structural elements recorded in these figures, the shape of the structural elements, the ratio of the size of the structural elements, and the relative positional relationship of the structural elements.

[0042] In the embodiments of the present invention, the terms "comprise", "include", "have" and the like refer to the existence of stated features, elements, components or assemblies, but do not exclude the existence or addition of one or more other features, elements, components or assemblies.

[0043] In the embodiments of the present invention, the singular forms "a", "the", etc. include plural forms and should be broadly understood as "a kind" or "a type" rather than being limited to the meaning of "one"; in addition, the term "said" should be understood to include both singular and plural forms, unless the context clearly indicates otherwise. In addition, the term "according to" should be understood as "at least in part according to...", and the term "based on" should be understood as "at least in part based on...", unless the context clearly indicates otherwise.

[0044] The protection circuit of the switching power supply according to the embodiment of the utility model is described below with reference to the accompanying drawings.

[0045] An embodiment of the utility model provides a protection circuit for a switching power supply.

[0046] Figure 1 FIG. 1 is a schematic diagram of the primary side circuit of the switching power supply of the embodiment of the utility model. Figure 1 As shown, the protection circuit of the switching power supply includes a latch circuit 10. The latch circuit 10 is arranged in the primary side circuit 1 of the switching power supply. The latch circuit 10 receives the secondary side circuit 2 (at the Figure 1 When a first signal (not shown) is received, a protection signal is generated, which causes the control chip (control IC) 20 in the primary side loop 1 of the switching power supply to enter the protection mode. The first output terminal 204 of the control chip 20 is connected to the switching element (not shown) in the primary side loop 1 of the switching power supply to control the on and off of the switching element. The latch circuit 10 has two protection signal output terminals, a first protection signal output terminal 105 and a second protection signal output terminal 106. At least one of the first protection signal output terminal 105 and the second protection signal output terminal 106 is connected to the control chip 20, and the protection signal is output to the control chip 20 through at least one of the first protection signal output terminal 105 and the second protection signal output terminal 106.

[0047] According to the above embodiment, a latch circuit is provided on the primary side of the switching power supply, and the latch circuit causes the control IC on the primary side to enter a protection mode according to a signal from the secondary side circuit. Thus, any protection provided by the control IC on the primary side can be utilized to implement latch protection based on the secondary side signal, thereby expanding the selection range of the control IC and making the design of the protection function of the switching power supply more convenient.

[0048] For example, Figure 1 As shown, the primary side loop 1 of the switching power supply is provided with a latch loop 10 and a control chip 20. The latch loop 10 is connected to the protection terminal of the control chip 20.

[0049] For another example, the latch circuit 10 has two protection signal output terminals, namely, a first protection signal output terminal 105 and a second protection signal output terminal 106. The first protection signal output terminal 105 and the second protection signal output terminal 106 have opposite levels, the first protection signal output terminal 105 is a high level, and the second protection signal output terminal 106 is a low level.

[0050] In some embodiments, the latch circuit 10 includes a control element 101 and a first metal oxide semiconductor field effect transistor (MOS) 102. The control element 101 is turned on according to the first signal. After the control element 101 is turned on, the first MOS transistor 102 is in a conducting state. The gate of the first MOS transistor 102 is connected to the first protection signal output terminal 105, and the drain of the first MOS transistor 102 is connected to the second protection signal output terminal 106.

[0051] For example, the control element 101 may be an optocoupler element, an input end of which is connected to the secondary side loop 2 of the switching power supply; the first MOS 102 may be an N-channel MOS, for example.

[0052] In some embodiments, the latch circuit 10 further includes a first triode 103 and a second triode 104. The collector of the first triode 103 is connected to the gate of the first MOS transistor 102, the base of the first triode 103 is connected to the collector of the second triode 104, the emitter of the first triode 103 is connected to a high level, and the base of the second triode 104 is connected to the first output terminal 1013 of the control element 101.

[0053] In some embodiments, the gate of the first MOS transistor 102 and the base of the second transistor 104 are connected via a first resistor R1 .

[0054] Combine the following Figure 1 The structure and operation principle of the latch circuit 10 will be described.

[0055] like Figure 1As shown, the control element 101 is an optical coupling element, the first transistor 103 is a PNP transistor, and the second transistor 104 is an NPN transistor. The second output terminal 1014 of the control element 101 is connected to a high level, the first output terminal 1013 of the control element 101 is connected to the base of the second transistor 104 through the second resistor R2, and the first output terminal 1013 of the control element 101 is connected to the gate of the first MOS transistor 102 through the second resistor R2 and the first resistor R1. The collector of the second transistor 104 is connected to the base of the first transistor 103 through the third resistor R3, and the collector of the second transistor 104 is connected to a high level through the fourth resistor R4. The base of the second transistor 104 is connected to the gate of the first MOS transistor 102 through the first resistor R1. The emitter of the first triode 103 is connected to a high level, the collector of the first triode 103 is connected to the gate of the first MOS tube 102, and the collector of the first triode 103 is connected to the first protection terminal 201 of the control chip 20 through the first protection signal output terminal 105. The drain of the first MOS tube 102 is connected to the second protection terminal 202 of the control chip 20 through the second protection signal output terminal 106. For example, the first protection terminal 201 is a high voltage pin, that is, when the first protection terminal 201 receives a high level signal, the control chip 20 enters the protection mode; the second protection terminal 202 is a low voltage pin, that is, when the second protection terminal 202 receives a low level signal, the control chip 20 enters the protection mode.

[0056] When the first signal received by the control element 101 from the secondary side loop 2 of the switching power supply is at a high level, the control element 101 is turned on. After the control element 101 is turned on, the gate of the first MOS transistor 102 is connected to the high level through the first resistor R1 and the second resistor R2, so the voltage of the gate of the first MOS transistor 102 becomes a high level, and the first MOS transistor 102 is turned on. In addition, when the control element 101 is turned on, the base of the second triode 104 is connected to the high level through the second resistor R2, so the voltage of the base of the second triode 104 becomes a high level, and the second triode 104 is turned on. After the second triode 104 is turned on, the base of the first triode 103 is grounded through the third resistor R3, so the voltage of the base of the first triode 103 becomes a low level, and the first triode 103 is turned on. After the first triode 103 is turned on, the voltage of the gate of the first MOS transistor 102 can continue to maintain a high level, so the first MOS transistor 102 can remain turned on, thereby realizing the latching function. Only when the high level is disconnected, the first MOS transistor 102 will release the latch.

[0057] like Figure 1As shown, the control chip 20 also has a first input terminal 203 and a first output terminal 204. The first input terminal 203 is connected to a high level. The first output terminal 204 is connected to a switch element (not shown) in the primary side loop 1 of the switching power supply to control the on and off of the switch element. For example, when the control chip 20 enters the protection mode, the first output terminal 204 outputs a low level signal to keep the switch element in the primary side loop 1 of the switching power supply off or off within a predetermined time period.

[0058] In some embodiments, the first signal is an overcurrent detection signal and / or an overvoltage detection signal from the secondary side loop 2 of the switching power supply. That is, the control element 101 receives the overcurrent detection signal and / or the overvoltage detection signal from the secondary side loop 2 of the switching power supply, and is turned on according to the overcurrent detection signal and / or the overvoltage detection signal.

[0059] Figure 2 It is a schematic diagram of the secondary side circuit of the switching power supply of the embodiment of the utility model.

[0060] In some embodiments, Figure 2 As shown, the protection circuit further includes an overvoltage detection circuit 30. The overvoltage detection circuit 30 is arranged in the secondary side loop 2 of the switching power supply and outputs an overvoltage detection signal.

[0061] In some embodiments, Figure 2 As shown, the overvoltage detection circuit 30 includes a first voltage regulator tube 301. The first voltage regulator tube 301 is used to detect the output voltage of the secondary side loop 2. The first voltage regulator tube 301 is connected in series with the control element 101 (for example, the first voltage regulator tube 301 is connected to the input terminal 1011 of the control element 101). When the output voltage exceeds the first voltage threshold, the first voltage regulator tube 301 is turned on and outputs an overvoltage detection signal to the control element 101. For example, the first voltage threshold is the turn-on voltage of the first voltage regulator tube 301. When the output voltage of the secondary side loop 2 is greater than the turn-on voltage of the first voltage regulator tube 301, the first voltage regulator tube 301 is turned on, and the control element 101 is turned on, thereby realizing the above-mentioned latching function.

[0062] In some embodiments, Figure 2 As shown, the protection circuit further includes an overcurrent detection circuit 40. The overcurrent detection circuit 40 is arranged in the secondary side loop 2 of the switching power supply and outputs an overcurrent detection signal.

[0063] In some embodiments, Figure 2As shown, the overcurrent detection circuit 40 includes an amplifier circuit 401 and a comparison circuit 402. The amplifier circuit 401 is used to convert the output current of the secondary side circuit 2 into a first voltage. The comparison circuit 402 is used to compare the first voltage with the second voltage threshold. The comparison circuit 402 is connected to the control element 101, and when the first voltage exceeds the second voltage threshold, the comparison circuit 402 outputs an overcurrent detection signal to the control element 101.

[0064] For example, Figure 2 As shown, the amplifier circuit 401 is a chip with an amplification function, which outputs a first voltage from a first terminal 4011. The first terminal 4011 is an output terminal. The first voltage is connected to a first input terminal 4021 of a comparison circuit 402 through a fifth resistor R5. The adjustable voltage stabilizing circuit 403 is connected to a second input terminal 4022 of the comparison circuit 402, and inputs a second voltage threshold into the comparison circuit 402. The comparison circuit 402 compares the first voltage with the second voltage threshold.

[0065] For another example, the amplifier circuit 401 further has a second terminal 4012, a third terminal 4013, a fourth terminal 4014, a fifth terminal 4015, a sixth terminal 4016 and a seventh terminal 4017. The second terminal 4012 and the third terminal 4013 are input terminals, the second terminal 4012 is connected to the output end of the secondary side circuit 2 through the sixth resistor R6 and the seventh resistor R7, and the third terminal 4013 is connected to the output end of the secondary side circuit 2 through the eighth resistor R8. The fourth terminal 4014 and the fifth terminal 4015 are connected to a high level. The fourth terminal 4014 is, for example, a VDD pin for power supply. The fifth terminal 4015 is, for example, a control signal pin for switching the operational amplifier mode. The sixth terminal 4016 is, for example, a pin for providing a reference voltage. The seventh terminal 4017 is, for example, a ground terminal.

[0066] In some embodiments, the overcurrent detection circuit 40 further includes an adjustable voltage stabilizing circuit 403. The adjustable voltage stabilizing circuit 403 is connected to the comparison loop 402 and is used to provide a second voltage threshold. The output voltage of the adjustable voltage stabilizing circuit 403 can be adjusted to adjust the second voltage threshold.

[0067] For example, Figure 2 As shown, the adjustable voltage stabilizing circuit 403 at least includes a second chip 4031 and an adjustable resistance resistor 4032, and the adjustable resistance resistor 4032 is, for example, a sliding rheostat. The output end of the second chip 4031 is connected to the adjustable resistance resistor 4032 through a resistor R15, and the adjustable resistance resistor 4032 adjusts the reference voltage output by the second chip 4031, thereby obtaining an adjusted second voltage threshold.

[0068] For example, Figure 2As shown, the overcurrent detection circuit 40 further includes a fourth transistor 404. When the output current of the secondary side loop 2 is greater than the first current threshold (ie, the first voltage exceeds the second voltage threshold), the fourth transistor 404 is turned on, and the control element 101 is turned on, thereby realizing the above latching function.

[0069] For example, Figure 2 As shown, the overcurrent detection circuit 40 is connected in parallel with the overvoltage detection circuit 30 .

[0070] According to the above embodiment, a latch circuit is provided on the primary side of the switching power supply, and the latch circuit causes the control IC on the primary side to enter a protection mode according to a signal from the secondary side circuit. Thus, any protection provided by the control IC on the primary side can be utilized to implement latch protection based on the secondary side signal, thereby expanding the selection range of the control IC and making the design of the protection function of the switching power supply more convenient.

[0071] The present invention is described above in conjunction with specific implementation methods, but it should be clear to those skilled in the art that these descriptions are exemplary and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make various modifications and variations to the present invention based on the spirit and principles of the present invention, and these modifications and variations are also within the scope of the present invention.

Claims

1. A protection circuit for a switching power supply, characterized in that: The protection circuit comprises: A latch circuit is provided in the primary side circuit of the switching power supply, and generates a protection signal when receiving a first signal from the secondary side circuit of the switching power supply, wherein the protection signal causes a control chip in the primary side circuit of the switching power supply to enter a protection mode, and a first output terminal of the control chip is connected to a switch element in the primary side circuit of the switching power supply to control the on and off of the switch element. in, The latch circuit has a first protection signal output terminal and a second protection signal output terminal, at least one of the first protection signal output terminal and the second protection signal output terminal is connected to the control chip, and the protection signal is output to the control chip through at least one of the first protection signal output terminal and the second protection signal output terminal.

2. The protection circuit according to claim 1, characterized in that: The latching circuit comprises: a control element, which is turned on according to the first signal; a first metal oxide semiconductor field effect transistor, which is in a conducting state after the control element is turned on, A gate of the first metal oxide semiconductor field effect transistor is connected to the first protection signal output terminal, and a drain of the first metal oxide semiconductor field effect transistor is connected to the second protection signal output terminal.

3. The protection circuit according to claim 2, characterized in that: The latching circuit also includes: The first transistor and the second transistor, The collector of the first transistor is connected to the gate of the first metal oxide semiconductor field effect transistor, The base of the first transistor is connected to the collector of the second transistor, The emitter of the first transistor is connected to a high level, The base of the second transistor is connected to the output end of the control element.

4. The protection circuit according to claim 3, characterized in that: The gate of the first metal oxide semiconductor field effect transistor is connected to the base of the second transistor through a first resistor.

5. The protection circuit according to claim 1, characterized in that: The first signal is an overcurrent detection signal and / or an overvoltage detection signal from a secondary side circuit of the switching power supply.

6. The protection circuit according to claim 5, characterized in that: The protection circuit further comprises: The overvoltage detection circuit is arranged in the secondary side loop of the switching power supply and outputs the overvoltage detection signal.

7. The protection circuit according to claim 6, characterized in that: The overvoltage detection circuit includes a voltage regulator tube, which is used to detect the output voltage of the secondary side circuit. The voltage regulator is connected to the control element of the latch loop. When the output voltage exceeds a first voltage threshold, the voltage regulator is turned on and outputs the overvoltage detection signal to the control element.

8. The protection circuit according to claim 5, characterized in that: The protection circuit further comprises: The overcurrent detection circuit is arranged in the secondary side loop of the switching power supply and outputs the overcurrent detection signal.

9. The protection circuit according to claim 8, characterized in that: The overcurrent detection circuit comprises: an amplifying circuit, used for converting the output current of the secondary side circuit into a first voltage; and a comparison circuit, which is used to compare the first voltage with a second voltage threshold, The comparison circuit is connected to a control element of the latch circuit, and when the first voltage exceeds the second voltage threshold, the comparison circuit outputs the overcurrent detection signal to the control element.

10. The protection circuit according to claim 9, characterized in that: The overcurrent detection circuit further includes: The adjustable voltage stabilizing circuit is connected to the comparison loop and provides the second voltage threshold. The output voltage of the adjustable voltage stabilizing circuit can be adjusted to adjust the second voltage threshold.

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