Protection circuit of printed circuit board, printed circuit board and cooking utensil

Abstract

The utility model discloses a protection circuit of a printed circuit board, the printed circuit board and a cooking utensil. The protection circuit of the printed circuit board comprises a first protection circuit section 11, a second protection circuit section 12 and a third protection circuit section 13 which are sequentially connected in series, the overcurrent resistance of the first protection circuit section 11 is smaller than that of the third protection circuit section 13, and the overcurrent resistance of the second protection circuit section 12 is larger than that of the third protection circuit section 13. According to the protection circuit, the problem that the first protection link and the second protection link which are connected with the two ends of the third protection link which is relatively high in overcurrent resistance in the protection circuit are disconnected when the current flowing through the protection circuit is greater than the preset current value in the prior art is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of protection circuits, in particular to a protection circuit of a printed circuit board, a printed circuit board and a cooking utensil. Background Art

[0002] On existing printed circuit boards, fuses are usually installed in the circuits that need to be protected to ensure the safety of the electrical load when the circuit is overloaded, overcurrent or in other abnormal operating conditions. However, fuses are usually large in size, not easy to install on the circuit board, and the installation cost is relatively high. In addition, when a fuse is installed on the circuit board, it is inevitable that there is contact resistance. When the rated current is large, it is easy to cause local overheating and damage the circuit board.

[0003] In order to solve the above problems, the related technology (CN201921347958.2) proposes a protection circuit segment of a printed circuit board for cooking appliances, wherein the protection circuit segment includes three protection links, wherein the printed circuits of the first protection link and the second protection link have the same length and similar width (about 4.5 mm), and the third protection link connected in series between the first protection link and the second protection link has the strongest ability to resist overcurrent, so that when the current flowing through the protection circuit is greater than the preset current value, the first protection link is disconnected from one of the second protection links, and the first protection link is not disconnected from the other of the second protection links and the third protection link.

[0004] It should be noted that, although the related art assumes that the third protection link has a stronger ability to resist overcurrent, when only one of the first protection link and the second protection link is disconnected, the other link will not be disconnected. However, in actual use, it is found that when the current flowing through the protection circuit is greater than the preset current value, more than 90% of the cases are that both the first protection link and the second protection link are disconnected, making it difficult to achieve the purpose of protecting the circuit multiple times through the first protection link and the second protection link.

[0005] With regard to the problem in the related art that when the current flowing through the protection circuit is greater than the preset current value, the first protection link and the second protection link connected at both ends of the third protection link with strong overcurrent resistance in the protection circuit will be disconnected, no effective solution has been proposed yet. Utility Model Content

[0006] The utility model provides a protective circuit of a printed circuit board, a printed circuit board and a cooking utensil, so as to solve the problem in the related art that when the current flowing through the protective circuit is greater than a preset current value, the first protection link and the second protection link connected at both ends of the third protection link with a strong overcurrent resistance capability in the protective circuit will be disconnected.

[0007] According to one aspect of the utility model, a protection circuit for a printed circuit board is provided. The protection circuit comprises: a first protection circuit segment, a second protection circuit segment, and a third protection circuit segment connected in series in sequence, wherein the first protection circuit segment has a lower ability to resist overcurrent than the third protection circuit segment, and the second protection circuit segment has a higher ability to resist overcurrent than the third protection circuit segment.

[0008] Optionally, the thickness of the first protection circuit segment, the second protection circuit segment and the third protection circuit segment are the same, the width of the first protection circuit segment is smaller than the width of the third protection circuit segment, the width of the third protection circuit segment is smaller than the width of the second protection circuit segment, the length of the first protection circuit segment is larger than the length of the second protection circuit segment, and the length of the second protection circuit segment is larger than the length of the third protection circuit segment. That is, when the materials are the same, the size of the circuit segment can be used to distinguish the size of the ability of the first protection circuit segment, the second protection circuit segment and the third protection circuit segment to resist overcurrent, so as to achieve the purpose that the ability of the first protection circuit segment to resist overcurrent is smaller than that of the third protection circuit segment, and the ability of the second protection circuit segment to resist overcurrent is larger than that of the third protection circuit segment.

[0009] Optionally, the thickness of the first protection circuit segment, the second protection circuit segment and the third protection circuit segment is in the range of 20 μm to 70 μm. The thickness of other traces of the printed circuit board is in the range of 20 μm to 70 μm, and the thickness of the first protection circuit segment, the second protection circuit segment and the third protection circuit segment can be the same as the thickness of other traces of the printed circuit board, thereby facilitating the manufacture of the printed circuit board.

[0010] Optionally, the width of the first protection circuit segment ranges from 0.1mm to 0.5mm, the width of the second protection circuit segment ranges from 2mm to 8mm, and the width of the third protection circuit segment ranges from 0.8mm to 2mm. When other conditions remain unchanged, the width of the circuit segment is positively correlated with the ability to resist overcurrent. When the first protection circuit segment, the second protection circuit segment, and the third protection circuit segment exist in the protection circuit at the same time, in order to achieve the effect that the first protection circuit segment is disconnected while the second and third protection circuit segments are not disconnected when the current flowing through the protection circuit is greater than a preset current value, the width of the second protection circuit segment can be set within a wider range, and the widths of the first and third protection circuit segments can be set within a narrower range, while having a clear width distinction.

[0011] Optionally, the length range of the first protection circuit segment is: 5mm~300mm, the length range of the second protection circuit segment is: 2mm~8mm, and the length range of the third protection circuit segment is: 1mm~3mm. When other conditions remain unchanged, the length of the circuit segment and the ability to resist overcurrent are inversely correlated. When the first protection circuit segment, the second protection circuit segment and the third protection circuit segment exist in the protection circuit at the same time, in order to achieve the effect that the first protection circuit segment is disconnected while the second protection circuit segment and the third protection circuit segment are not disconnected when the current flowing through the protection circuit is greater than the preset current value, the length of the first protection circuit segment can be set within a longer range, and the length of the second protection circuit segment and the third protection circuit segment can be set within a shorter range.

[0012] Optionally, the length of the second protection circuit segment is greater than the length of the third protection circuit segment. If the length of the second protection circuit segment is too short, or the length of the third protection circuit segment is too long, the probability of the first protection circuit segment and the third protection circuit segment being disconnected at the same time is greatly increased, and the second protection circuit segment is set to be wider and longer than the third protection circuit segment, thereby increasing the current carrying capacity of the second protection circuit. If the current flows from the first protection circuit segment, the wider and longer second protection circuit segment can carry more current, thereby protecting the third protection circuit segment from being burned out when the first protection circuit segment is disconnected. If the current flows from the third protection circuit segment, the second protection circuit segment and the third protection circuit segment retain the current and transfer the energy to the first protection circuit segment, thereby causing the first protection circuit segment to be disconnected first and the third protection circuit segment to be not disconnected.

[0013] Optionally, the first protection circuit segment includes a plurality of curved segments connected in sequence, so that the area occupied by the first protection circuit segment as a whole is relatively small, thus saving space on the printed circuit board.

[0014] Optionally, the width of the plurality of curved segments connected in sequence is less than or equal to the width of the second protection circuit segment, so that the widths of the first protection circuit segment, the second protection circuit segment and the third protection circuit segment are limited within a certain width range, thereby reducing the area occupied by the protection circuit on the printed circuit board.

[0015] According to another aspect of the utility model, a printed circuit board is provided, which comprises: a substrate; any one of the above-mentioned protection circuits, arranged on a live wire on the substrate, wherein a load is connected between the live wire and the neutral wire, and a varistor is also connected between the live wire and the neutral wire.

[0016] According to another aspect of the present invention, a cooking utensil is provided, which comprises: the printed circuit board mentioned above.

[0017] The protection circuit in the utility model comprises: a first protection circuit segment, a second protection circuit segment, and a third protection circuit segment connected in series in sequence, wherein the first protection circuit segment has a lower ability to resist overcurrent than the third protection circuit segment, and the second protection circuit segment has a higher ability to resist overcurrent than the third protection circuit segment. Since the protection circuit segment with a lower ability to resist overcurrent is easier to disconnect, the first protection circuit segment has a lower ability to resist overcurrent than the third protection circuit segment, and thus the first protection circuit segment is easier to disconnect than the third protection circuit segment, and the second protection circuit segment connected in series between the first protection circuit segment and the third protection circuit has a stronger ability to resist overcurrent and can play a role in current carrying, so when the current flowing through the protection circuit is greater than a preset current value, the first protection circuit segment can be disconnected only, and the third protection circuit segment can be protected from disconnection, which solves the problem in the related art that when the current flowing through the protection circuit is greater than a preset current value, the first protection link and the second protection link connected at both ends of the third protection link with a stronger ability to resist overcurrent in the protection circuit will both be disconnected. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the accompanying drawings:

[0019] Figure 1 is a schematic diagram of a protection circuit of a printed circuit board provided according to an embodiment of the utility model;

[0020] Figure 2 is a schematic diagram of a printed circuit board provided according to an embodiment of the utility model;

[0021] Among them, 11, the first protection circuit section; 12, the second protection circuit section; 13, the third protection circuit section; L, the live wire; N, the neutral wire; R, the load; VR, the varistor. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] In order to enable those skilled in the art to better understand the solution of the utility model, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the utility model and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so as to describe the embodiments of the utility model described here.

[0025] According to an embodiment of the utility model, a protection circuit for a printed circuit board is provided.

[0026] Figure 1 Schematic diagram of a protection circuit of a printed circuit board according to an embodiment of the utility model. Figure 1 As shown, the protection circuit includes:

[0027] The first protection circuit segment 11, the second protection circuit segment 12, and the third protection circuit segment 13 are connected in series in sequence, wherein the first protection circuit segment 11 has a smaller ability to resist overcurrent than the third protection circuit segment 13, and the second protection circuit segment 12 has a larger ability to resist overcurrent than the third protection circuit segment 13.

[0028] It should be noted that, compared with the protection circuit in the related art, the first protection circuit segment 11 and the third protection circuit segment 13 in this embodiment have different abilities to resist overcurrent, and a second protection circuit segment 12 with stronger ability to resist overcurrent is arranged between the two. The second protection circuit segment 12 protects the third protection circuit segment 13 by its larger current-carrying capacity. Therefore, when the circuit is overloaded, overcurrent or in other abnormal operating conditions, the first protection circuit segment 11 and the third protection circuit segment 13 will not be disconnected at the same time, but the first protection circuit segment 11 will be disconnected first, which not only replaces the fuse in the prior art and plays a role in circuit protection, but also the second protection circuit segment 12 can be used as a connection point to connect the disconnected circuit through a wire. Since the third protection circuit segment 13 is not disconnected at the same time as the first protection circuit segment 11, the third protection circuit segment 13 is still valid and can continue to play a role in circuit protection in the circuit.

[0029] The protection circuit in the utility model comprises a first protection circuit segment 11, a second protection circuit segment 12, and a third protection circuit segment 13 connected in series in sequence, wherein the first protection circuit segment 11 has a lower ability to resist overcurrent than the third protection circuit segment 13, and the second protection circuit segment 12 has a higher ability to resist overcurrent than the third protection circuit segment 13. Since the protection circuit segment with a lower ability to resist overcurrent is easier to disconnect, the first protection circuit segment 11 has a lower ability to resist overcurrent than the third protection circuit segment 13, and thus the first protection circuit segment 11 is easier to disconnect than the third protection circuit segment 13, and the second protection circuit segment 12 connected in series between the first protection circuit segment 11 and the third protection circuit has a stronger ability to resist overcurrent and can play a role in current carrying, so when the current flowing through the protection circuit is greater than a preset current value, only the first protection circuit segment 11 can be disconnected, and the third protection circuit segment 13 can be protected from disconnection, which solves the problem in the related art that when the current flowing through the protection circuit is greater than a preset current value, both the first protection link and the second protection link connected at both ends of the third protection link with a stronger ability to resist overcurrent in the protection circuit will be disconnected.

[0030] Optionally, in the protection circuit of the printed circuit board provided in the embodiment of the utility model, the first protection circuit segment 11, the second protection circuit segment 12, the third protection circuit segment 13 and other traces on the printed circuit board are made of the same material.

[0031] Specifically, the materials of the first protection circuit segment 11, the second protection circuit segment 12, the third protection circuit segment 13 and other traces on the printed circuit board can all be copper foil, which has a lower cost, thereby reducing the cost of the protection circuit and the cost of the entire printed circuit board.

[0032] When the materials are the same, the ability of the first protection circuit segment 11, the second protection circuit segment 12 and the third protection circuit segment 13 to resist overcurrent can be distinguished by the size of the circuit segments. Optionally, in the protection circuit of the printed circuit board provided in the embodiment of the utility model, the thickness of the first protection circuit segment 11, the second protection circuit segment 12 and the third protection circuit segment 13 are the same, the width of the first protection circuit segment 11 is smaller than the width of the third protection circuit segment 13, the width of the third protection circuit segment 13 is smaller than the width of the second protection circuit, the length of the first protection circuit segment 11 is greater than the length of the second protection circuit segment 12, and the length of the second protection circuit segment 12 is greater than the length of the third protection circuit.

[0033] Specifically, the thickness of the first protection circuit segment 11, the second protection circuit segment 12, and the third protection circuit segment 13 can be the same as the thickness of other traces of the printed circuit board, so as to facilitate the manufacture of the printed circuit board. The thickness of the printed circuit board has a certain range. If the thickness of the trace is too thick, the overall cost of the circuit board will increase. Optionally, in the protection circuit of the printed circuit board provided in the embodiment of the utility model, the thickness of the first protection circuit segment 11, the second protection circuit segment 12, and the third protection circuit segment 13 ranges from 20 μm to 70 μm.

[0034] In the case of similar thickness, the overcurrent resistance capabilities of the first protection circuit segment 11 , the second protection circuit segment 12 , and the third protection circuit segment 13 can be distinguished by the width and length of the circuit segments.

[0035] Under the condition that other conditions remain unchanged, the width of the circuit segment and the ability to resist overcurrent are positively correlated. The wider the circuit segment, the stronger the ability to resist overcurrent. When the first protection circuit segment 11, the second protection circuit segment 12 and the third protection circuit segment 13 exist in the protection circuit at the same time, in order to achieve the effect that the first protection circuit segment 11 is disconnected while the second protection circuit segment 12 and the third protection circuit segment 13 are not disconnected when the current flowing through the protection circuit is greater than the preset current value, the width of the second protection circuit segment 12 can be set within a wider range, and the width of the first protection circuit segment 11 and the third protection circuit segment 13 can be set within a narrower range, while having obvious width distinction. In this way, after the first protection circuit segment 11 is disconnected, the circuit is connected by a wire (which can be a wire wider than the third protection circuit segment 13). The second protection circuit segment 12 and the third protection circuit segment 13 exist in the protection circuit at the same time. When the current flowing through the protection circuit is greater than the preset current value, the third protection circuit segment 13 can be disconnected while the second protection circuit segment 12 is not disconnected.

[0036] Optionally, in the protection circuit of the printed circuit board provided in the embodiment of the utility model, the width range of the first protection circuit segment 11 is: 0.1mm~0.5mm, the width range of the second protection circuit segment 12 is: 2mm~8mm, and the width range of the third protection circuit segment 13 is: 0.8mm~2mm.

[0037] In the related art, the width of the first protection link and the second protection link at both ends of the third protection link is set at about 4.5 mm, and the difference in width between the two is very small. When the current flowing through the protection circuit is greater than the preset current value, it is difficult to achieve the set goal of one being disconnected while the other is not disconnected. According to tests, the protection circuit in the related art has a probability of more than 90% that the first protection link and the second protection link are disconnected at the same time, and there is only a probability of less than 10% that one is disconnected while the other is not disconnected.

[0038] Under the condition that other conditions remain unchanged, the length of the circuit segment and the ability to resist overcurrent are inversely correlated. The longer the length of the circuit segment, the greater the resistance, the series voltage division, the greater the voltage to be borne, and the smaller the current flowing through. When the first protection circuit segment 11, the second protection circuit segment 12 and the third protection circuit segment 13 exist in the protection circuit at the same time, in order to achieve the effect that the first protection circuit segment 11 is disconnected when the current flowing through the protection circuit is greater than the preset current value, while the second protection circuit segment 12 and the third protection circuit segment 13 are not disconnected, the length of the first protection circuit segment 11 can be set within a longer range, and the length of the second protection circuit segment 12 and the third protection circuit segment 13 can be set within a shorter range. In this way, after the first protection circuit segment 11 is disconnected, the circuit is connected by a wire (which can be a wire wider than the third protection circuit segment 13). The second protection circuit segment 12 and the third protection circuit segment 13 exist in the protection circuit at the same time. When the current flowing through the protection circuit is greater than the preset current value, the third protection circuit segment 13 can be disconnected while the second protection circuit segment 12 is not disconnected.

[0039] Optionally, in the protection circuit of the printed circuit board provided in the embodiment of the utility model, the length range of the first protection circuit segment 11 is: 5mm~300mm, the length range of the second protection circuit segment 12 is: 2mm~8mm, and the length range of the third protection circuit segment 13 is: 1mm~3mm.

[0040] It should be noted that, although the length of the circuit segment and the ability to resist overcurrent are inversely correlated when other conditions remain unchanged, in theory, the length of the second protection circuit segment 12 should be set shorter than the length of the third protection circuit segment 13, so as to better achieve the purpose of the second protection circuit segment 12 having a stronger ability to resist overcurrent than the third protection circuit segment 13. However, when the first protection circuit segment 11, the second protection circuit segment 12 and the third protection circuit segment 13 are all present in the protection circuit, this embodiment expects the first protection circuit segment 11 to be disconnected before the third protection circuit segment 13. When only the second protection circuit segment 12 and the third protection circuit segment 13 are present in the protection circuit, this embodiment expects the third protection circuit segment 13 to be disconnected before the second protection circuit segment 12. If the length of the second protection circuit segment 12 is too short or the length of the third protection circuit segment 13 is too long, the probability of the first protection circuit segment 11 and the third protection circuit segment 13 being disconnected at the same time is greatly increased. In this embodiment, the second protection circuit segment 12 can be set wider than the third protection circuit segment 13 and longer than the third protection circuit segment 13, so as to increase the current carrying capacity of the second protection circuit. Optionally, in the protection circuit of the printed circuit board provided in the embodiment of the utility model, the length of the second protection circuit segment 12 is greater than the length of the third protection circuit segment 13 .

[0041] The current has a flow direction. If the current flows from the first protection circuit segment 11, the wider and longer second protection circuit segment 12 can carry more current, thereby protecting the third protection circuit segment 13 from being burned out when the first protection circuit segment 11 is disconnected. If the current flows from the third protection circuit segment 13, the second protection circuit segment 12 and the third protection circuit segment 13 retain the current and transfer the energy to the first protection circuit segment 11, so that the first protection circuit segment 11 is disconnected first and the third protection circuit segment 13 is not disconnected.

[0042] That is, at the level of fuse protection, although the second protection circuit segment 12 does not play the role of fuse protection, the second protection circuit segment 12 is equivalent to a transfer point, which plays the role of a watershed partition. On the one hand, when the current flows through, if the second protection circuit segment 12 is narrow, the ability to resist overcurrent is weak. When the current flows from the first protection circuit segment 11, the second protection circuit segment 12 is also likely to be burned out. When the second protection circuit segment 12 is burned out, the third protection circuit segment 13 will inevitably be burned out. On the other hand, if the second protection circuit segment 12 is short, although the ability to resist overcurrent is stronger and it is not easy to be burned out, the ability to carry current is weak, and the protection effect on the third protection circuit segment 13 is very weak. When the first protection circuit segment 11 is burned out, the third protection circuit segment 13 will also be burned out. On the other hand, if the third protection circuit segment 13 is too long, when testing the protection circuit including the first protection circuit segment 11, the second protection circuit segment 12, and the third protection circuit segment 13, the current will burn out the third protection circuit segment 13 while burning out the first protection circuit segment 11. For example, when the length of the third protection circuit segment 13 is less than 3 mm, the probability that the first protection circuit segment 11 is disconnected first is 80% to 90%. When the length of the third protection circuit segment 13 is greater than 3 mm, the probability that the first protection circuit segment 11 is disconnected first is 20% to 30%.

[0043] Theoretically, the larger the size of the second protection circuit segment 12 is, the better. Considering the limited space occupied by the protection circuit on the printed circuit board, the size of the second protection circuit segment 12 only needs to meet actual needs. Therefore, the length of the second protection circuit segment 12 is set between 2mm and 8mm.

[0044] Since the length of the first protection circuit segment 11 is relatively long, ranging from 5 mm to 300 mm, if the first protection circuit segment 11 is arranged in a straight line, the length occupied on the printed circuit board is relatively long. Optionally, in the protection circuit of the printed circuit board provided in the embodiment of the utility model, the first protection circuit segment 11 includes a plurality of curved segments connected in sequence. The term "plurality" refers to two or more.

[0045] That is, in this embodiment, the first protection circuit segment 11 is configured as a plurality of curved segments connected in sequence, so that the area occupied by the first protection circuit segment 11 as a whole is relatively small, thus saving space on the printed circuit board.

[0046] Optionally, in the protection circuit of the printed circuit board provided in the embodiment of the utility model, the width of the plurality of curved sections connected in sequence is less than or equal to the width of the second protection circuit section 12 .

[0047] It should be noted that, since the second protection circuit segment 12 is the widest, setting the width of multiple curved segments connected in sequence to be less than or equal to the width of the second protection circuit segment 12 can limit the width of the first protection circuit segment 11, the second protection circuit segment 12 and the third protection circuit segment 13 to a certain width range, thereby reducing the area occupied by the protection circuit on the printed circuit board.

[0048] In an optional embodiment, the materials of the first protection circuit segment 11, the second protection circuit segment 12 and the third protection circuit segment 13 are copper foils, the thickness of which is set to 35 μm, the width of the first protection circuit segment 11 is set to 0.3 mm, the length is set to 70 mm, the width of the second protection circuit segment 12 is set to 5 mm, the length is set to 5 mm, the width of the third protection circuit segment 13 is set to 1 mm, and the length is set to 2 mm. After testing, the parameter configuration of this embodiment is reasonable. When an overcurrent occurs, the first protection circuit segment 11 is disconnected first with a probability of 90%, thereby well replacing the insurance circuit in the relevant technology.

[0049] The utility model also provides a printed circuit board. Figure 2 Schematic diagram of a printed circuit board according to an embodiment of the utility model.

[0050] like Figure 2 As shown, the printed circuit board includes: a substrate; any one of the above-mentioned protection circuits is arranged on the live wire L on the substrate, wherein a load R is connected between the live wire L and the neutral wire N, and a varistor VR is also connected between the live wire L and the neutral wire N.

[0051] exist Figure 2In the embodiment, the protection circuit is arranged on the live wire, the first protection circuit segment 11 in the protection circuit is connected to the head end of L, the third protection circuit segment 13 is connected to one end of the load R, the load R can be a 220V load, the varistor VR is used for lightning protection, when the live wire L and the neutral wire N are short-circuited, it is hoped that the circuits and devices outside the live wire 1 will not be burned, in order to prevent L from being burned when the voltage is too large, the varistor VR will be short-circuited, and the first protection circuit segment 11 in the protection circuit will be burned first when the varistor VR is short-circuited, thereby taking away the energy from the live wire L to the neutral wire N, preventing the energy from being added to the load R, thereby protecting the load R. It should be noted that, since the upper half cycle of the normal wave of the electrical signal may come first or the lower half cycle may come, the positions of the first protection circuit segment 11 and the third protection circuit segment 13 in the printed circuit board can be interchanged, that is, the third protection circuit segment 13 is connected to the head end of the live wire L, and the first protection circuit segment 11 is connected to one end of the load R.

[0052] The embodiment of the utility model further provides a cooking utensil. The cooking utensil comprises: the above-mentioned printed circuit board.

[0053] Specifically, the cooking utensil may be a rice cooker, a pressure cooker, etc. The above-mentioned printed circuit board can be used in any place where a small fuse is needed in the cooking utensil, so that when an overcurrent occurs, the first protection circuit segment 11 in the protection circuit is first disconnected to protect the electrical load. After the first protection circuit segment 11 is disconnected, the disconnected part can be connected by a wire, so that the protection circuit includes a second protection circuit segment 12 and a third protection circuit segment 13, so that when an overcurrent occurs, the third protection circuit segment 13 in the protection circuit is first disconnected to protect the electrical load again without replacing the entire protection circuit. The electrical appliance using the printed circuit board of this embodiment can more reliably meet the requirements of 19.1 of General Requirements for Safety Part 1 of GB 4706.1-2005 Household and Similar Electrical Appliances.

[0054] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A protective circuit for a printed circuit board, characterized in that: include: A first protection circuit segment (11), a second protection circuit segment (12), and a third protection circuit segment (13) are connected in series in sequence, wherein the first protection circuit segment (11) has a lower ability to resist overcurrent than the third protection circuit segment (13), and the second protection circuit segment (12) has a higher ability to resist overcurrent than the third protection circuit segment (13).

2. The protective circuit of the printed circuit board according to claim 1, characterized in that: The first protection circuit segment (11), the second protection circuit segment (12) and the third protection circuit segment (13) have the same thickness, the width of the first protection circuit segment (11) is smaller than the width of the third protection circuit segment (13), the width of the third protection circuit segment (13) is smaller than the width of the second protection circuit, the length of the first protection circuit segment (11) is greater than the length of the second protection circuit segment (12), and the length of the second protection circuit segment (12) is greater than the length of the third protection circuit.

3. The protective circuit of the printed circuit board according to claim 2, characterized in that: The thickness of the first protection circuit segment (11), the second protection circuit segment (12) and the third protection circuit segment (13) ranges from 12 μm to 70 μm.

4. The protective circuit of the printed circuit board according to claim 2, characterized in that: The width of the first protection circuit segment (11) ranges from 0.1 mm to 0.5 mm, the width of the second protection circuit segment (12) ranges from 2 mm to 8 mm, and the width of the third protection circuit segment (13) ranges from 0.8 mm to 2 mm.

5. The protective circuit of the printed circuit board according to claim 2, characterized in that: The length range of the first protection circuit segment (11) is 5 mm to 130 mm, the length range of the second protection circuit segment (12) is 2 mm to 8 mm, and the length range of the third protection circuit segment (13) is 1 mm to 3 mm.

6. The protective circuit of the printed circuit board according to claim 5, characterized in that: The length of the second protection circuit section (12) is greater than the length of the third protection circuit section (13).

7. The protective circuit for a printed circuit board according to claim 5, characterized in that: The first protection circuit segment (11) comprises a plurality of curved segments connected in sequence.

8. The protective circuit for a printed circuit board according to claim 7, characterized in that: The width of the plurality of curved sections connected in sequence is less than or equal to the width of the second protection circuit section (12).

9. A printed circuit board, comprising: substrate; The protective circuit of the printed circuit board according to any one of claims 1 to 8 is arranged on the live wire (L) on the substrate, wherein a load (R) is connected between the live wire (L) and the neutral wire (N), and a varistor (VR) is also connected between the live wire (L) and the neutral wire (N).

10. A cooking utensil, characterized in that: The cooking appliance comprises the printed circuit board according to claim 9, or comprises the protective circuit of the printed circuit board according to any one of claims 1 to 8.

Images