A power type compound thermistor for suppressing inrush current

Abstract

This invention discloses a power-type composite thermistor for suppressing surge current, comprising an NTC thermistor chip and a PTC thermistor chip encapsulated in a resin layer with their two electrodes in contact. A common pin is fixed to the contact electrode of the NTC and PTC thermistor chips, and NTC and PTC thermistor pins are fixed to the non-contact electrode of the NTC and PTC thermistor chips, respectively. The contact NTC and PTC thermistor chips are connected in parallel in a circuit for suppressing surge current. This invention uses a soldered encapsulation method, facilitating mass production, and offers advantages such as low-temperature start-up, surge suppression, and adaptability to frequent power-on / off cycles. Its novel structure has promising application prospects.

Description

Technical Field

[0001] This utility model relates to the field of electronic component technology, and in particular to a power composite thermistor that integrates NTC (negative temperature coefficient) and PTC (positive temperature coefficient) thermistor chips to solve the problems of low-temperature start-up and frequent start-up surge. Background Technology

[0002] When electronic devices (such as power supplies and motor drivers) start up, they generate surge currents that are much larger than the normal operating current due to factors such as capacitor charging and inductor excitation. These surge currents can be several to tens of times higher than the steady-state current, which can damage sensitive components in the circuit, reduce the lifespan of the equipment, or even cause immediate failure.

[0003] Currently, using NTC (negative temperature coefficient) thermistors as surge current suppression components is the most common solution. NTC thermistors have the characteristic of high resistance at room temperature, but when current flows through them, their resistance rapidly decreases due to the heat generated by their own heating. This characteristic allows them to limit surge current at the moment of circuit startup, and then reduce power loss as the circuit enters normal operating conditions. However, using a single NTC thermistor as a surge suppression component has the following two significant drawbacks:

[0004] First, starting up is difficult in low-temperature environments. The resistance of NTC thermistors increases dramatically, exponentially, as the temperature decreases. When the ambient temperature is low, such as below -20°C, the initial resistance of an NTC thermistor may be more than 10 times that at room temperature. This results in an excessively high equivalent circuit resistance, causing difficulty in starting the electronic device or even preventing it from starting when the starting current is insufficient.

[0005] Secondly, the surge suppression capability decreases with frequent starts. Under normal operating conditions, the NTC thermistor heats up due to the continuous flow of current, and its resistance drops to a very low level. If the circuit is frequently started and stopped in a short period of time, the NTC thermistor does not have enough time to cool down, and its residual resistance remains very small, making it unable to effectively suppress surge current during the next start-up.

[0006] Therefore, overcoming these two major shortcomings is an urgent problem that needs to be solved. Utility Model Content

[0007] The purpose of this invention is to overcome the problems existing in current NTC thermistors used for suppressing surge current. This invention's surge current suppression power-type composite thermistor combines an NTC thermistor chip and a PTC thermistor chip in parallel, giving it advantages such as good low-temperature start-up, effective surge suppression, and adaptability to frequent power-on and power-off cycles. The product uses a welding and encapsulation process, facilitating mass production. The resulting power-type composite thermistor has a novel structure and promising application prospects.

[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0009] A power-type composite thermistor for suppressing surge current includes an NTC thermistor chip and a PTC thermistor chip encapsulated in a resin layer with their two electrodes in contact. A common pin is fixed to the contact electrode of the NTC and PTC thermistor chips, and NTC and PTC thermistor pins are fixed to the non-contact electrode of the NTC and PTC thermistor chips, respectively.

[0010] The NTC thermistor pin and the PTC thermistor pin serve as one terminal of the entire power-type composite thermistor; the common pin serves as the other terminal of the entire power-type composite thermistor, connecting the NTC thermistor chip and the PTC thermistor chip in parallel in the circuit loop for suppressing surge current.

[0011] Preferably, the bonding electrodes of the NTC thermistor chip and the PTC thermistor chip are fixed together by co-firing with silver paste or solder paste, the common pin is fixed to the bonding electrodes of the NTC thermistor chip and the PTC thermistor chip by soldering, and the NTC thermistor pins and PTC thermistor pins are fixed to the corresponding electrodes of the NTC thermistor chip and the PTC thermistor chip by soldering.

[0012] Preferably, the NTC thermistor pin and the PTC thermistor pin are connected by a U-shaped lead, the U-shaped lead is encapsulated with an insulating resin layer, the common pin extends out of the resin layer, and one of the NTC thermistor pins or the PTC thermistor pins also extends out of the resin layer. The two delay parts form a two-pin configuration and the portions extending out of the resin layer are arranged in parallel.

[0013] Preferably, the common pin, NTC thermistor pin, and PTC thermistor pin each include an integrally formed connecting section, a bent section, and an extension section. The connecting section is encapsulated within the resin layer on the surface of the corresponding thermistor chip. The bent section and the extension section extend out of the resin layer. The portions of the common pin, NTC thermistor pin, and PTC thermistor pin extending out of the resin layer are arranged in parallel.

[0014] Preferably, the portions of the common pin, the NTC thermistor pin, and the PTC thermistor pin extending out of the resin layer are arranged in parallel and are in the same plane.

[0015] Preferably, in the portion extending out of the resin layer, the PTC thermistor pin is located between the common pin and the NTC thermistor pin.

[0016] Preferably, in the portion extending out of the resin layer, the common pin is located at the middle position between the NTC thermistor pin and the PTC thermistor pin.

[0017] Preferably, the resin layer is a silicone resin layer, and the NTC thermistor chip and the PTC thermistor chip are eccentrically bonded, with a reserved soldering area for the common pin.

[0018] Preferably, the NTC thermistor chip is selected with a resistance value of 80Ω-1000Ω at room temperature; the PTC thermistor chip is selected with a resistance value of 5-30Ω at room temperature.

[0019] Preferably, the NTC thermistor chip is selected with a resistance value of 100Ω at room temperature; the PTC thermistor chip is selected with a resistance value of 10Ω at room temperature.

[0020] The beneficial effects of this utility model are as follows: The power-type composite thermistor for suppressing surge current of this utility model combines NTC thermistor chips and PTC thermistor chips in parallel and encapsulates them through welding, which facilitates mass production. When applied to surge current suppression starting power supply modules of electronic devices, it has the following advantages:

[0021] (1) Solve the problem of difficult start-up in low temperature environment: ensure that the circuit can still obtain sufficient start-up current in low temperature environment (such as below -20℃) to avoid start-up failure.

[0022] (2) Maintain surge suppression capability during frequent starts: Even with frequent starts and stops in a short period of time, it can still effectively suppress surge current during each start.

[0023] (3) Simplified circuit structure: The above functions are achieved through a simple dual-chip parallel structure, without the need for additional control circuits or switching components.

[0024] (4) Reduce power loss: Under normal operating conditions, maintain low power loss and improve the efficiency of electronic devices;

[0025] (5) Diverse structural forms: There is one two-pin lead-out method and two three-pin lead-out methods. It can be customized according to customer needs, which is highly adaptable and easy to promote in batches. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the pin configuration of the power-type composite thermistor for suppressing surge current according to this utility model.

[0027] Figure 2 This is a back view of the pin configuration 1 of the power-type composite thermistor for suppressing surge current of this utility model.

[0028] Figure 3 This is a schematic diagram of the pin configuration two of the power-type composite thermistor for suppressing surge current according to this utility model;

[0029] Figure 4 This is a rear view of the pin configuration 2 of the power-type composite thermistor for suppressing surge current of this utility model.

[0030] Figure 5 This is a schematic diagram of the pin configuration three of the power-type composite thermistor for suppressing surge current according to this utility model;

[0031] Figure 6 This is a rear view of pin configuration three of the power-type composite thermistor for suppressing surge current according to this utility model.

[0032] The meanings of the markings in the attached diagram are as follows:

[0033] 1: Resin layer; 2: NTC thermistor chip; 3: PTC thermistor chip; 4: Common pin; 5: NTC thermistor pin; 6: PTC thermistor pin; 7: U-shaped lead. Detailed Implementation

[0034] The present invention will now be further described in conjunction with the accompanying drawings.

[0035] like Figures 1-6As shown, the power-type composite thermistor for suppressing surge current of this invention includes an NTC thermistor chip 2 and a PTC thermistor chip 3 encapsulated in a resin layer 1 with their two electrodes in contact. A common pin 4 is fixed on the contact electrode of the NTC thermistor chip 2 and the PTC thermistor chip 3. An NTC thermistor pin 5 is fixed on the non-contact electrode of the NTC thermistor chip 2. A PTC thermistor pin 6 is fixed on the non-contact electrode of the PTC thermistor chip 3.

[0036] The NTC thermistor pin 5 and the PTC thermistor pin 6 serve as one terminal of the entire power-type composite thermistor; the common pin 4 serves as the other terminal of the entire power-type composite thermistor, connecting the NTC thermistor chip 2 and the PTC thermistor chip 3 in parallel in the circuit loop for suppressing surge current.

[0037] The bonding electrodes of the NTC thermistor chip 2 and the PTC thermistor chip 3 are fixed together by co-firing with silver paste or tin paste, preferably by co-firing with silver paste, which provides a firm and reliable fixation. The common pin 4 is fixed to the bonding electrodes of the NTC thermistor chip 2 and the PTC thermistor chip 3 by soldering. The NTC thermistor pins 5 and 6 are fixed to the corresponding electrodes of the NTC thermistor chip 2 and the PTC thermistor chip 3 by soldering. The soldering method can firmly and reliably fix the common pin 4, the NTC thermistor pin 5, and the PTC thermistor pin 6 to the corresponding thermistor chip electrodes.

[0038] like Figures 1-2 As shown, in the first pin configuration of this utility model: the NTC thermistor pin 5 and the PTC thermistor pin 6 are connected by a U-shaped lead 7. The U-shaped lead 7 is encapsulated with an insulating resin layer 1. The common pin 4 extends out of the resin layer 1. One of the NTC thermistor pin 5 or the PTC thermistor pin 6 also extends out of the resin layer 1. The two delay parts form a two-pin configuration, and the portions extending out of the resin layer 1 are arranged in parallel, which facilitates the carrying on the material tape and improves the overall efficiency of the material tape packaging.

[0039] like Figure 3-6Figure 2 shows the pin configurations of this utility model, specifically: the common pin 4, NTC thermistor pin 5, and PTC thermistor pin 6 each include an integrally formed connecting section, a bending section, and an extension section. The connecting section is encapsulated within the resin layer 1 on the surface of the corresponding thermistor chip. The bending section and the extension section extend beyond the resin layer 1. The portions of the common pin 4, NTC thermistor pin 5, and PTC thermistor pin 6 extending beyond the resin layer 1 are arranged in parallel and within the same plane, facilitating their loading on the material tape and improving the overall efficiency of the material tape packaging.

[0040] In the portion extending beyond the resin layer 1, the PTC thermistor pin 6 is located between the common pin 4 and the NTC thermistor pin 5, as shown below. Figure 3 As shown in Figure 4, in this second pin configuration, the pin positions of the NTC thermistor pin 5 and the PTC thermistor pin 6 are relatively close, which facilitates connection in actual application circuits.

[0041] In the portion extending from the resin layer 1, the common pin 4 is located between the NTC thermistor pin 5 and the PTC thermistor pin 6, as shown below. Figure 5 As shown in Figure 6, this pin configuration is convenient to process and has an aesthetically pleasing appearance.

[0042] like Figure 1 and Figure 2 As shown, both common pin 4, NTC thermistor pin 5, and PTC thermistor pin 6 are acceptable lead-out options, and adjustments can be made according to customer or market requirements.

[0043] The resin layer 1 is a silicone resin layer, which has a mature process, low encapsulation cost, and is easy to implement. It can also protect the reliability of the NTC thermistor chip 2 and the PTC thermistor chip 3 when used at high temperatures.

[0044] The NTC thermistor chip 2 and the PTC thermistor chip 3 are eccentrically attached, leaving a soldering area for the common pin 4.

[0045] The NTC thermistor chip 2 is selected with a resistance value of 80Ω-1000Ω at room temperature; the PTC thermistor chip 3 is selected with a resistance value of 5-30Ω at room temperature, preferably, the NTC thermistor chip 2 is selected with a resistance value of 100Ω at room temperature. The PTC thermistor chip 3 is selected with a resistance value of 10Ω at room temperature, which can overcome the shortcomings of a single NTC thermistor in starting up at low temperatures and the decrease in surge suppression capability during frequent starts. By connecting a high-resistance NTC thermistor in parallel with a low-resistance PTC thermistor, the complementary temperature characteristics of the two are utilized to achieve effective surge suppression over a wide temperature range. Moreover, in low-temperature environments, the resistance change of the PTC thermistor is small, ensuring that the circuit can obtain sufficient starting current. Under normal operating conditions, although the resistance of the NTC thermistor decreases, it still maintains a certain resistance value, ensuring that surge current can still be effectively suppressed during frequent starts. Furthermore, the integrated encapsulation process results in a simple and compact structure, which is easy to manufacture and requires no additional control circuitry. It has the advantages of good low-temperature starting performance, long-lasting suppression capability during frequent starts, and high reliability.

[0046] The power-type composite thermistor for suppressing surge current of this invention has the following parameter design.

[0047] NTC thermistor chip 2, resistance value at room temperature (25℃): 100Ω; B value: 3600K (25℃ / 50℃)

[0048] Dissipation coefficient δ: 30mW / ℃; Material: Manganese-cobalt-nickel-iron-copper ceramic, with the desired properties achieved by adjusting the proportions;

[0049] PTC thermistor chip 3: Resistance value at room temperature (25℃): 10Ω; Curie point: 125℃; Material: barium titanate-based ceramic, with the Curie point controlled by doping elements;

[0050] Connection materials: Silver paste: 80% Ag content, with 3% glass powder added as a sintering aid; Sintering temperature: 750℃-850℃, sintering time: 45 minutes; Structural parameters: NTC thermistor chip 2 dimensions: φ20mm×2.5mm; PTC thermistor chip 3 dimensions: φ13mm×2.5mm, lead material: tin-plated copper wire, diameter 0.8mm. These NTC and PTC thermistor chips are connected in parallel to form a power-type composite thermistor. Analysis of the working process of this power-type composite thermistor for suppressing surge current:

[0051] (1) Low temperature start-up condition (-20℃):

[0052] The resistance of the NTC thermistor chip, calculated based on the B value, is approximately 1000Ω at this temperature; the resistance of the PTC thermistor chip is approximately 15Ω (a slow increase due to temperature decreases). Therefore, the total parallel resistance is approximately 14.78Ω, sufficient for normal startup. However, even using a single NTC thermistor chip with a room temperature resistance of only 10Ω (because the resistance of an NTC thermistor increases dramatically at low temperatures, so the room temperature resistance of a single NTC thermistor chip cannot be high), the resistance is approximately 100Ω. The difference between the two is 6.8 times. At this low temperature, starting with a single NTC thermistor chip becomes difficult. Using a parallel structure of NTC and PTC thermistor chips effectively solves this problem.

[0053] (2) Under normal operating conditions, the temperature rise is approximately 180℃ (assuming the operating current is 1.5A):

[0054] At this point, the resistance of the NTC thermistor chip is approximately 2Ω (which decreases sharply due to temperature rise), the resistance of the PTC thermistor chip is approximately 12Ω, the total parallel resistance is approximately 1.71Ω, and the power loss is 3.85W in this embodiment, compared to the 1.125W power loss of a single 10Ω NTC thermistor chip during normal operation (assuming a current of 1.5A). Although slightly higher, this is acceptable considering the significant improvement in surge suppression.

[0055] (3) Frequent start-up situations (starting immediately after power failure):

[0056] At this point, the resistance of a single 10Ω NTC resistor chip is only 0.5Ω under the same conditions, while the resistance in this embodiment is 1.71Ω, a difference of 3.42 times. Therefore, even if the power is turned on immediately after being turned off, this embodiment still has a certain surge current suppression capability. In addition, because this embodiment has a higher temperature rise at normal operating current, under the same conditions, the cooling rate is faster and the temperature drop is greater after power failure, and its resistance will increase more quickly. Therefore, it can still suppress surge current under frequent start-up conditions.

[0057] In summary, the power-type composite thermistor for suppressing surge current of this invention connects NTC and PTC thermistor chips in parallel and encapsulates them through soldering, facilitating mass production. It offers the following advantages for surge current suppression starting power supply modules in electronic devices:

[0058] (1) Solve the problem of difficult start-up in low temperature environment: ensure that the circuit can still obtain sufficient start-up current in low temperature environment (such as below -20℃) to avoid start-up failure.

[0059] (2) Maintain surge suppression capability during frequent starts: Even with frequent starts and stops in a short period of time, it can still effectively suppress surge current during each start.

[0060] (3) Simplified circuit structure: The above functions are achieved through a simple dual-chip parallel structure, without the need for additional control circuits or switching components.

[0061] (4) Reduce power loss: Under normal operating conditions, maintain low power loss and improve the efficiency of electronic devices;

[0062] (5) Diverse structural forms: There is one two-pin lead-out method and two three-pin lead-out methods. It can be customized according to customer needs, which is highly adaptable and easy to promote in batches.

[0063] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A power-type composite thermistor for suppressing surge current, characterized in that: The device includes an NTC thermistor chip (2) and a PTC thermistor chip (3) encapsulated in a resin layer (1) with their two electrodes in contact. A common pin (4) is fixed on the contact electrode of the NTC thermistor chip (2) and the PTC thermistor chip (3). An NTC thermistor pin (5) is fixed on the non-contact electrode of the NTC thermistor chip (2), and a PTC thermistor pin (6) is fixed on the non-contact electrode of the PTC thermistor chip (3). The NTC thermistor pin (5) and PTC thermistor pin (6) serve as one terminal of the entire power-type composite thermistor; the common pin (4) serves as the other terminal of the entire power-type composite thermistor, and the NTC thermistor chip (2) and PTC thermistor chip (3) that are attached to each other are connected in parallel in the circuit loop for suppressing surge current.

2. The power-type composite thermistor for suppressing surge current according to claim 1, characterized in that: The bonding electrodes of the NTC thermistor chip (2) and the PTC thermistor chip (3) are fixed together by silver paste or tin paste co-firing. The common pin (4) is fixed to the bonding electrodes of the NTC thermistor chip (2) and the PTC thermistor chip (3) by soldering. The NTC thermistor pin (5) and the PTC thermistor pin (6) are fixed to the corresponding electrodes of the NTC thermistor chip (2) and the PTC thermistor chip (3) by soldering.

3. The power-type composite thermistor for suppressing surge current according to claim 2, characterized in that: The NTC thermistor pin (5) and the PTC thermistor pin (6) are connected by a U-shaped lead (7). The U-shaped lead (7) is covered with an insulating resin layer (1). The common pin (4) extends out of the resin layer (1). One of the NTC thermistor pin (5) or the PTC thermistor pin (6) also extends out of the resin layer (1). The two delay parts form a two-pin configuration and the parts extending out of the resin layer (1) are arranged in parallel.

4. The power-type composite thermistor for suppressing surge current according to claim 2, characterized in that: The common pin (4), NTC thermistor pin (5), and PTC thermistor pin (6) each include an integrally formed connecting section, a bent section, and an extension section. The connecting section is encapsulated on the surface of the corresponding thermistor chip within the resin layer (1). The bent section and the extension section extend out of the resin layer (1). The portions of the common pin (4), NTC thermistor pin (5), and PTC thermistor pin (6) extending out of the resin layer (1) are arranged in parallel.

5. The power-type composite thermistor for suppressing surge current according to claim 4, characterized in that: The portions of the common pin (4), NTC thermistor pin (5), and PTC thermistor pin (6) extending out of the resin layer (1) are arranged in parallel and are in the same plane.

6. The power-type composite thermistor for suppressing surge current according to claim 5, characterized in that: In the portion extending out of the resin layer (1), the PTC thermistor pin (6) is located between the common pin (4) and the NTC thermistor pin (5).

7. The power-type composite thermistor for suppressing surge current according to claim 5, characterized in that: In the portion extending out of the resin layer (1), the common pin (4) is located between the NTC thermistor pin (5) and the PTC thermistor pin (6).

8. The power-type composite thermistor for suppressing surge current according to claim 1, characterized in that: The resin layer (1) is a silicone resin layer. The NTC thermistor chip (2) and the PTC thermistor chip (3) are eccentrically attached, leaving a welding area for the common pin (4).

9. The power-type composite thermistor for suppressing surge current according to claim 1, characterized in that: The NTC thermistor chip (2) is selected with a resistance value of 80Ω-1000Ω at room temperature; the PTC thermistor chip (3) is selected with a resistance value of 5-30Ω at room temperature.

10. The power-type composite thermistor for suppressing surge current according to claim 9, characterized in that: The NTC thermistor chip (2) is selected with a resistance value of 100Ω at room temperature; the PTC thermistor chip (3) is selected with a resistance value of 10Ω at room temperature.

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