Over-temperature protection compensation device

Abstract

The application discloses an over-temperature protection compensation device, which comprises a main control IC, a thermistor, a first resistor and a second resistor. The first end of the main control IC is connected with the first end of the first resistor and the first end of the second resistor respectively, the second end of the main control IC is connected with the second end of the second resistor and used for being connected with the positive pole of an external power supply, the second end of the first resistor is connected with the first end of the thermistor, the second end of the thermistor is grounded, the main control IC is used for detecting the working voltage of the first end of the main control IC and outputting corresponding working current to the first resistor and the thermistor according to the detected working voltage, and the second resistor is used for introducing compensation current to the first resistor and the thermistor so as to increase the working voltage of the first end of the main control IC. The application can flexibly adjust the over-temperature protection temperature hysteresis by introducing the compensation current through the second resistor, the switching frequency selection of the main control IC is not limited, the NTC resistor value is not limited and can be flexibly selected, and the circuit is simple.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, in particular to an over-temperature protection compensation device. BACKGROUND

[0002] With the development of power electronics technology, the volume of most existing electronic products is gradually reduced with the development, such as DC / DC converter, etc. However, the heat problem caused by miniaturization has always existed. The electronic products damaged by overheat due to improper use or improper installation are not in the minority every year. Therefore, most electronic products need over-temperature protection circuit to avoid the product entering abnormal state when working at high temperature, resulting in electronic product damage and other problems. The traditional over-temperature protection circuit mostly uses NTC or temperature switch. The former has poor precision and large temperature hysteresis when protecting, which will cause the product to fail to start again after triggering over-temperature protection when working at high temperature. The latter has large volume and high cost. Therefore, a new over-temperature protection circuit is needed to overcome the problem of large over-temperature protection temperature hysteresis in the prior art, and to provide an over-temperature protection circuit compensation scheme to solve the problem of too large over-temperature protection temperature hysteresis. SUMMARY

[0003] The present application aims to overcome at least one of the defects in the prior art, provide an over-temperature compensation device, and solve the problem of uncontrollable temperature hysteresis of the over-temperature protection circuit in the prior art, so as to achieve the effect of flexible adjustment of over-temperature protection temperature hysteresis.

[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0005] On the one hand, an over-temperature protection compensation device is provided, which comprises:

[0006] a main control IC, a thermistor, a first resistor and a second resistor;

[0007] The first end of the main control IC is connected with the first end of the first resistor and the first end of the second resistor respectively, the second end is connected with the second end of the second resistor and used for connecting with the positive pole of an external power supply;

[0008] The second end of the first resistor is connected with the first end of the thermistor;

[0009] The second end of the thermistor is grounded;

[0010] The main control IC is used for detecting the working voltage of the first end of the main control IC, and outputting corresponding working current to the first resistor and the thermistor according to the detected working voltage;

[0011] The second resistor is used for introducing compensation current to the first resistor and the thermistor to increase the working voltage of the first end of the main control IC.

[0012] Preferably, the working current comprises a first current and a second current, wherein the first current is greater than the second current;

[0013] The master IC outputs a corresponding working current to the first resistor and the thermistor according to the detected working voltage, comprising:

[0014] The master IC compares the detected working voltage with an internally set over-temperature protection threshold value;

[0015] When it is determined that the working voltage is greater than the over-temperature protection threshold value, the first current is maintained to be outputted;

[0016] When it is determined that the working voltage is less than the over-temperature protection threshold value, the protection mode is started and the second current is outputted.

[0017] Preferably, the first current and the second current are proportional; the first current and the second current are both proportional to the switching frequency of the master IC.

[0018] Preferably, the thermistor is a negative temperature coefficient resistor.

[0019] In another aspect, an over-temperature protection compensation device is provided, comprising: a master IC, a thermistor, a first resistor and a second resistor;

[0020] The first end of the master IC is connected with the first end of the first resistor, the second end is connected with the second end of the second resistor and is used for being connected with the positive pole of an external power supply;

[0021] The second end of the first resistor is connected with the first end of the second resistor and the first end of the thermistor respectively;

[0022] The second end of the thermistor is grounded;

[0023] The master IC is used for detecting the working voltage of the first end of the master IC, and outputs a corresponding working current to the first resistor and the thermistor according to the detected working voltage;

[0024] The second resistor is used for introducing a compensation current to the thermistor, so as to increase the working voltage of the first end of the master IC.

[0025] Preferably, the working current comprises a first current and a second current, wherein the first current is greater than the second current;

[0026] The master IC outputs a corresponding working current to the first resistor and the thermistor according to the detected working voltage, comprising:

[0027] The master IC compares the detected working voltage with an internally set over-temperature protection threshold value;

[0028] when the working voltage is determined to be greater than the over-temperature protection threshold, outputting a first current;

[0029] when the working voltage is determined to be less than the over-temperature protection threshold, starting a protection mode and outputting a second current.

[0030] Preferably, the first current and the second current are proportional; the first current and the second current are both proportional to a switching frequency of the master IC.

[0031] Preferably, the thermistor is a negative temperature coefficient resistor.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] 1. By the master IC outputting different currents according to the detected voltage, cooperating with an external power supply and a second resistor to provide a compensation current, the over-temperature protection temperature hysteresis is flexibly adjusted.

[0034] 2. Since the maximum resistance of the thermistor NTC on the market is 680K (25℃), the present application increases the voltage across the thermistor NTC by connecting the external power supply and the second resistor to input the compensation current into the thermistor NTC, so that a thermistor NTC with a smaller resistance can be selected under the same requirement, reducing the selection limitation of the thermistor NTC.

[0035] 3. After cooperating with the external power supply and the second resistor to input the compensation current, the switching frequency of the master IC can be further reduced, and after the switching frequency is reduced, the main power loss of the product is reduced, the product efficiency is improved, and the product heat is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a prior art over-temperature protection schematic diagram.

[0037] Figure 2 It is an over-temperature protection schematic diagram of the embodiment one of the present application.

[0038] Figure 3 It is an over-temperature protection schematic diagram of the embodiment two of the present application. DETAILED DESCRIPTION

[0039] The present application will be described in detail below with reference to the embodiments and the accompanying drawings, to help the skilled in the art better understand the practical concept of the present application, but the protection scope of the claims of the present application is not limited to the following embodiments, and all other embodiments obtained by the skilled in the art without creative labor on the premise of not departing from the inventive concept of the present application, belong to the protection scope of the present application, and the embodiments will be described in detail below with reference to the accompanying drawings.

[0040] AsFigure 1 As shown, it is a circuit principle diagram of the existing over-temperature protection circuit, the existing over-temperature protection circuit is composed of a pulse width control chip IC1, a thermistor NTC and a first resistor R1, one end of the first resistor R1 is connected to the OTP pin of the pulse width control chip IC1, the other end of the first resistor R1 is connected to one end of the thermistor NTC, and the other end of the thermistor NTC is connected to the negative input end GND. The thermistor NTC is a negative temperature coefficient resistor.

[0041] The working principle of the existing over-temperature protection circuit is as follows:

[0042] The OTP pin of the pulse width control chip IC1 outputs a current I_OTP, which flows through the first resistor R1 and the thermistor NTC to generate a negative temperature coefficient working voltage, the pulse width control chip IC1 detects the working voltage through the OTP pin, and compares the working voltage with the over-temperature protection threshold value set in the chip, when the detected working voltage is lower than the over-temperature protection threshold value V_OTP, the pulse width control chip IC1 internally outputs an over-temperature protection signal, and the product triggers over-temperature protection. The pulse width control chip IC1 has an over-temperature protection hysteresis design, when the product does not trigger over-temperature protection, the OTP pin of the pulse width control chip IC1 outputs a first current I_OTP1, when the product triggers over-temperature protection, the OTP pin of the pulse width control chip IC1 outputs a second current I_OTP2, wherein I_OTP2=0.88*I_OTP1.

[0043] When the current value of the first current I_OTP1 is small, a thermistor NTC and a resistor R1 with a larger resistance value need to be selected, and the largest thermistor NTC on the market is currently 680K (25℃), at this time, the first resistor R1 needs to have a larger resistance value, and the larger the resistance value of the first resistor R1, the larger the over-temperature protection hysteresis of the product, and the principle is as follows:

[0044] When the product triggers over-temperature protection and exits over-temperature protection, the over-temperature protection threshold value V_OTP of the OTP pin of the pulse width control chip IC1 does not change.

[0045] V_OTP=I_OTP1*(R1+NTC)=0.88*I_OTP1(R1+NTC+△NTC)

[0046] (1-0.88)I_OTP1*(R1+NTC)=0.88*I_OTP1*△NTC

[0047] In the above formula, △NTC is the resistance value change amount of the thermistor NTC at two different temperatures when triggering the over-temperature protection and when the over-temperature protection is restored, NTC is the resistance value of the thermistor NTC, R1 is the resistance value of the first resistor R1, I_OTP1 is the current value of the first current I_OTP1, and I_OTP2 is the current value of the second current I_OTP2.

[0048] From the above formula, when R1 increases, △NTC increases, which means that the over-temperature protection temperature point hysteresis increases. However, when the over-temperature protection temperature hysteresis increases to a certain value, it will cause the product to be unable to start again after triggering the over-temperature protection when working at high temperature.

[0049] In order to overcome the problem of large over-temperature protection temperature hysteresis in the prior art, the embodiment provides an over-temperature protection circuit compensation scheme to solve the problem of too large over-temperature protection temperature hysteresis.

[0050] First embodiment

[0051] As shown in Figure 2 , it is a circuit schematic diagram of the over-temperature protection compensation device of the embodiment, and the over-temperature protection scheme is different from Figure 1 the circuit scheme shown in the circuit principle diagram of the prior over-temperature protection. The difference is that the over-temperature protection control circuit is additionally provided with a second resistor R2 to perform current compensation on the pulse width control chip IC1.

[0052] In the embodiment, an over-temperature protection compensation device is provided, which comprises:

[0053] a master control IC, a thermistor NTC, a first resistor R1, and a second resistor R2;

[0054] The first end of the master control IC is connected with the first end of the first resistor R1 and the first end of the second resistor R2 respectively, the second end is connected with the second end of the second resistor R2, and is used for being connected with the positive electrode of an external power supply;

[0055] The second end of the first resistor R1 is connected with the first end of the thermistor NTC;

[0056] The second end of the thermistor NTC is grounded;

[0057] The master control IC is used for detecting the working voltage of the first end of the master control IC, and outputting a corresponding working current to the first resistor R1 and the thermistor NTC according to the detected working voltage;

[0058] The second resistor R2 is used for introducing a compensation current to the first resistor R1 and the thermistor NTC to increase the working voltage of the first end of the master control IC.

[0059] Specifically, the main control IC is a pulse width control chip IC1, a first end of the main control IC is an OTP pin, and a second end of the main control IC is a VCC pin; a first end of the second resistor R2 is connected to the VCC pin of the pulse width control chip IC1, and a second end of the second resistor R2 is connected to a first end of the first resistor R1; wherein the working voltage of the first end of the main control IC is the sum of the voltage between the first resistor R1 and the voltage between the thermistor NTC.

[0060] Specifically, the first current I_OTP1 and the second current I_OTP2 are proportional; the first current I_OTP1 and the second current I_OTP2 are both proportional to the switching frequency of the main control IC.

[0061] When the external power supply flows the compensation current into the second resistor R2 in real time, at this time the current value of the compensation current I_COM is Wherein, VCC is the voltage value of the external power supply.

[0062] The working principle of the over-temperature protection circuit is as follows:

[0063] The OTP pin of the pulse width control chip IC1 outputs the first current I_OTP1, which flows through the first resistor R1 and the thermistor NTC to generate a negative temperature coefficient working voltage, that is, the working voltage of the OTP pin. The pulse width control chip IC1 detects the working voltage and compares it with the over-temperature protection threshold V_OTP set in the chip. When the detected working voltage is lower than the over-temperature protection threshold V_OTP, the pulse width control chip IC1 internally outputs an over-temperature protection signal, the product triggers over-temperature protection, and the pulse width control chip IC1 outputs the second current I_OTP2 from the OTP pin. It can be understood that when the first current I_OTP1 or the second current I_OTP2 flows out of the OTP pin of the pulse width control chip IC1, the internal part of the pulse width control chip IC1 can detect the working voltage of the OTP pin in real time, that is, the working voltage of the OTP pin is formed by the current flowing through the first resistor R1 and the thermistor NTC.

[0064] The external power supply of the embodiment supplies power to the main control IC in real time and provides compensation current to the first resistor R1 and the thermistor NTC through the second resistor R2. At this time, due to the superposition of the compensation current and the first current I_OTP1 or the second current I_OTP2, the total current flowing through the first resistor R1 and the thermistor NTC is increased, thereby effectively reducing the resistance value of the first resistor R1, flexibly adjusting the protection point of the over-temperature protection, and the over-temperature protection return difference.

[0065] Specifically, since the product triggers the over-temperature protection and exits the over-temperature protection, the over-temperature protection threshold V OTP of the OTP pin of the pulse width control chip IC1 is unchanged, therefore, when the product triggers the over-temperature protection, the compensation current I COM is superimposed on the second current I OTP2, and

[0066] V OTP = (I OTP2 + I COM) * (R1 + NTC)

[0067] When the product exits the over-temperature protection, the compensation current I COM is superimposed on the first current I OTP1, and

[0068] V OTP = (I OTP1 + I COM) * (R1 + NTC)

[0069] Therefore, when the compensation current I COM is superimposed on the first current I OTP1, in order to achieve the same voltage value of the over-temperature protection threshold V OTP of the OTP pin of the pulse width control chip IC1, at this time, the resistance value of the first resistor R1 can be smaller than the resistance value of the first resistor R1 in the prior art, that is, the change amount of the resistance value of the NTC is also smaller, and the over-temperature protection temperature hysteresis of the product is reduced.

[0070] Meanwhile, when the compensation current I COM is superimposed on the first current I OTP1, under the same over-temperature protection hysteresis of the product, the first current I OTP1 can be appropriately reduced, that is, the switching frequency of the pulse width control chip IC1 can be reduced, and after the switching frequency of the pulse width control chip IC1 is reduced, the product loss can be reduced and the efficiency is improved.

[0071] Specifically, the circuit topology of the embodiment is used Figure 2 to make a sample for testing; in order to illustrate the beneficial effects of the over-temperature protection compensation device of the first embodiment of the present application, the over-temperature protection circuit of the prior art used for comparison adopts the same circuit parameters: including the resistance value of the thermistor NTC and the over-temperature protection trigger point temperature.

[0072] As shown in Table 1, the over-temperature hysteresis and efficiency comparison test results of the over-temperature hysteresis circuit of the present embodiment and the prior art are shown in Table 1, and from the comparison test data in Table 1, it can be obviously seen that when the resistance value of the thermistor NTC and the over-temperature protection trigger point temperature are the same, compared with the prior art, the over-temperature protection compensation device of the present embodiment can use a first resistor R1 with a smaller resistance value, so that the change amount of the resistance value of the NTC is also smaller, the over-temperature protection temperature hysteresis of the product is reduced, and the switching frequency of the pulse width control chip IC1 can also be reduced, the product loss is reduced, and the product efficiency is improved.

[0073] Table 1 is the over-temperature hysteresis and efficiency comparison test results of the present application and the prior art

[0074]

[0075] Second embodiment

[0076] As Figure 3 shown, different from the first embodiment, in the embodiment, the first end of the second resistance R2 is connected with the VCC pin of the pulse width control chip IC1, the second end of the second resistance R2 is connected with the first end of the thermistor NTC and the second end of the first resistance R1.

[0077] Specifically, the first current and the second current are proportional; the first current and the second current are both proportional to the switching frequency of the main control IC.

[0078] When the external power supply flows the compensation current into the second resistance R2 in real time, at this time, the current value of the compensation current I_COM is Wherein, VCC is the voltage value of the external power supply.

[0079] When the product triggers the over-temperature protection and exits the over-temperature protection, the over-temperature protection threshold V_OTP of the OTP pin of the pulse width control chip IC1 is unchanged. When the product triggers the over-temperature protection, after the compensation current is superimposed on the second current I_OTP2:

[0080] V_OTP=I_OTP2*R1+(I_OTP2+I_COM)*NTC

[0081] When the product exits the over-temperature protection, after the compensation current is superimposed on the first current I_OTP1:

[0082] V_OTP=I_OTP1*R1+(I_OTP1+I_COM)*NTC

[0083] Therefore, when the compensation current I_COM is superimposed on the first current I_OTP1, in order to achieve the same over-temperature protection threshold V_OTP voltage value of the OTP pin of the pulse width control chip IC1, at this time, the first resistance R1 can be smaller than the original scheme, that is, the △NTC resistance value change is also smaller, and the product over-temperature protection temperature hysteresis is reduced.

[0084] At the same time, when the compensation current I_COM is superimposed on the first current I_OTP1, under the same product over-temperature protection hysteresis, the first current I_OTP1 can be appropriately reduced, that is, the switching frequency of the pulse width control chip IC1 can be reduced, after the switching frequency of the pulse width control chip IC1 is reduced, the product loss can be reduced, and the efficiency is improved.

[0085] The present application is not limited to the above specific embodiments, according to the above content, according to the ordinary technical knowledge and conventional means in the art, without departing from the above basic technical idea of the present application, the present application can also make other various forms of equivalent modification, replacement or change, all fall within the protection scope of the present application.

Claims

1. An over-temperature protection compensation device, characterized in that, include: Main control IC, thermistor, first resistor and second resistor; The first terminal of the main control IC is connected to the first terminal of the first resistor and the first terminal of the second resistor, respectively, and the second terminal is connected to the second terminal of the second resistor and is used to connect to the positive terminal of an external power supply. The second end of the first resistor is connected to the first end of the thermistor; The second terminal of the thermistor is grounded; The main control IC is used to detect the operating voltage of the first terminal of the main control IC, and output the corresponding operating current to the first resistor and the thermistor according to the detected operating voltage; The second resistor is used to introduce compensation current to the first resistor and the thermistor to increase the operating voltage of the first terminal of the main control IC; The operating current includes a first current and a second current, wherein the first current is greater than the second current; The main control IC outputs a corresponding operating current to the first resistor and the thermistor based on the detected operating voltage, including: The main control IC compares the detected operating voltage with the internally set over-temperature protection threshold; When the operating voltage is determined to be greater than the over-temperature protection threshold, the first output current is maintained. When the operating voltage is determined to be less than the over-temperature protection threshold, the protection mode is activated and a second current is output.

2. The over-temperature protection compensation device according to claim 1, characterized in that, The first current and the second current are proportional; both the first current and the second current are proportional to the switching frequency of the main control IC.

3. The over-temperature protection compensation device according to any one of claims 1-2, characterized in that, The main control IC is a pulse width control chip.

4. The over-temperature protection compensation device according to any one of claims 1-2, characterized in that, The thermistor is a negative temperature coefficient resistor.

5. An over-temperature protection compensation device, characterized in that, include: Main control IC, thermistor, first resistor and second resistor; The first terminal of the main control IC is connected to the first terminal of the first resistor, and the second terminal is connected to the second terminal of the second resistor and is used to connect to the positive terminal of an external power supply. The second end of the first resistor is connected to the first end of the second resistor and the first end of the thermistor, respectively. The second terminal of the thermistor is grounded; The main control IC is used to detect the operating voltage of the first terminal of the main control IC, and output the corresponding operating current to the first resistor and the thermistor according to the detected operating voltage; The second resistor is used to introduce compensation current to the thermistor to increase the operating voltage of the first terminal of the main control IC; The operating current includes a first current and a second current, wherein the first current is greater than the second current; The main control IC outputs a corresponding operating current to the first resistor and the thermistor based on the detected operating voltage, including: The main control IC compares the detected operating voltage with the internally set over-temperature protection threshold; When the operating voltage is determined to be greater than the over-temperature protection threshold, the first output current is maintained. When the operating voltage is determined to be less than the over-temperature protection threshold, the protection mode is activated and a second current is output.

6. The over-temperature protection compensation device according to claim 5, characterized in that, The first current and the second current are proportional; both the first current and the second current are proportional to the switching frequency of the main control IC.

7. The over-temperature protection compensation device according to any one of claims 5-6, characterized in that, The main control IC is a pulse width control chip.

8. The over-temperature protection compensation device according to any one of claims 5-6, characterized in that, The thermistor is a negative temperature coefficient resistor.

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