CN211151501U

CN211151501U - Over-temperature protection circuit and electronic product

Info

Publication number: CN211151501U
Application number: CN201922343702.0U
Authority: CN
Inventors: 应征; 高强
Original assignee: BCD Shanghai Micro Electronics Ltd
Current assignee: BCD Shanghai Micro Electronics Ltd
Priority date: 2019-12-20
Filing date: 2019-12-20
Publication date: 2020-07-31
Anticipated expiration: 2029-12-20

Abstract

The utility model discloses an over-temperature protection circuit and an electronic product, wherein in the over-temperature protection circuit, a first sampling voltage related to both the current temperature and the input external voltage and a second sampling voltage unrelated to the current temperature but related to the input external voltage are collected through a sampling module, and generating a reference voltage from the second sampled voltage, thereby enabling the reference voltage to be correlated with the external voltage, by mutually offsetting the reference voltage and the external voltage part in the second sampling voltage, the correlation between the over-temperature protection threshold point and the external voltage is greatly reduced and even completely uncorrelated, namely, when the external voltage received by the over-temperature protection circuit changes, the over-temperature protection circuit can also accurately protect the product at the same or similar temperature threshold point, so that the over-temperature protection function of certain products requiring multi-voltage output or input can be met.

Description

Over-temperature protection circuit and electronic product

Technical Field

The utility model relates to an excess temperature protection circuit technical field especially relates to an excess temperature protection circuit and electronic product.

Background

Referring to fig. 1, a conventional AC/DC power supply system with an over-temperature protection circuit function generally comprises an AC input power supply 100, a diode rectifier bridge 101, a voltage stabilizing capacitor C102, a transformer primary inductor L103, a secondary inductor L104, a primary power MOS transistor M105, a secondary rectifier diode D106, an output resistor R107, an output capacitor C108, a primary detection resistor R112, a diode D115, a sampling resistor R111, a thermistor R113(NTC), and a voltage comparator 110, wherein the voltage comparator 110 is a main part of the over-temperature protection circuit 10, and is connected to a serial node of the sampling resistor R111 and the thermistor R113(NTC) for implementing a sampling voltage V_SAMPLEAnd a fixed reference voltage V_REFTo obtain an over-temperature detection result. Diode D115 anode connected V_KThe voltage is one and the output voltage V_OUTThe voltage values of the related voltages are specifically: v_k＝KO×(V_OUT+V_D106)，V_D106K0 is a fixed multiple of the voltage across the secondary rectifier diode D106. The thermistor R113(NTC) is a negative temperature coefficient thermistor, and is characterized in that the higher the temperature, the lower the resistance value R (t), and the formula is as follows:

wherein R (T) is the resistance of the thermistor R113(NTC) at temperature T; r₀Denotes the temperature, T, of a thermistor R113(NTC) at ambient temperature₀Represents normal temperature; b is the process parameter of the thermistor R113 (NTC).

The thermistor R113(NTC) and the sampling resistor R111 are connected in series to divide the voltage to obtain a sampling voltage V_SAMPLEThen it is compared with a fixed reference voltage V_REFAnd comparing to obtain an over-temperature detection result. Specifically, from fig. 1, we can obtain:

V_K＝(V_OUT+V_D115)×K0.................................................(3)

from equations (2) and (3), one can derive:

in the above formula (4), V_OUTRepresenting the output voltage, V_D106Representing the voltage across the secondary rectifier diode D106, V_D115Represents the voltage across diode D115; r₁₁₃(T) represents the resistance of the thermistor R113, which is a function of temperature in relation to the temperature T, and is calculated by the formula (1).

As is known from the above, the thermistor R113 is monotonically negatively correlated with temperature. Therefore, as can be seen from equation (4): v_SAMPLEIs a voltage which is monotonically positively correlated with temperature, i.e. the higher the temperature, the higher V_SAMPLEThe higher.

The comparator 110 compares the fixed reference voltage V_REFAnd a sampling voltage V_SAMPLEThus, as the temperature increases, when a certain temperature (i.e., the over-temperature protection temperature threshold) is reached, V_SAMPLEGreater than V_REFOver-temperature protection is triggered. Suppose the over-temperature protection temperature threshold is T_CTHV corresponding to over-temperature protection threshold point_SAMPLEA voltage of V_{SAMPLE_TH}When the temperature reaches T_CTHThen, from equation (4):

from the above formula, one can see:

as can be seen from the publication (5), T_CTHAnd V_OUTAnd (4) correlating. Therefore, the output voltage V is different under the same system parameter_OUTLower, triggered over-temperature protection threshold point T_CTHThe disparity, whose difference is calculated as follows:

assume that there are two voltage outputs: v_OUT0And V_OUT1The corresponding over-temperature protection threshold points are respectively T_CTH0And T_CTH1We can get:

from equations (6) and (7), we can derive:

in equation (8), Δ V represents two different output voltages V_OUT0And V_OUT1Difference between, Δ R_ORGAt two different output voltages V_OUT0And V_OUT1The difference value of the resistance value, Δ R, of the thermistor R113 corresponding to the over-temperature protection threshold value_ORGThe larger the value, the more the over-temperature protection threshold point T is represented under two different output voltages_CTH0、T_CTH1The greater the phase difference therebetween. Further, as is clear from the publication (8),. DELTA.R_ORGIs strongly correlated with Δ V.

We assume that: k0 ═ 2.33, R111 ═ 1kohm, V_REF＝0.308V，V_OUT1＝3V，V_OUT2＝5V，

From equation (8): Δ R_ORG＝15kohm。

We look up a table with the thermistor R113 type VISHAYNTC L E100E3(100Kohm) resistor as a reference, assuming V is_OUT0Overtemperature protection threshold point T corresponding to 3V_CTH0At 120 ℃ then V_OUT1Over-temperature protection threshold point T corresponding to 5V_CTH160 ℃ and the difference between the two is as high as 60 ℃.

Obviously, the over-temperature protection circuit 10 only aims at a certain fixed output voltage, and after the output voltage changes, the over-temperature protection threshold point T is triggered_CTHIn turn, the over-temperature protection function becomes inaccurate, and therefore, the over-temperature protection circuit cannot be used in some product applications (such as a charger product of a rapid charging series) which need multiple voltage outputs (i.e., different output voltages).

Therefore, how to realize accurate over-temperature protection function in some products requiring multiple voltage outputs also becomes a key technical problem to be solved urgently by those skilled in the art.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide an excess temperature protection circuit and electronic product can also realize accurate excess temperature protect function in the product that needs many voltage output.

In order to achieve the above object, the present invention provides an over-temperature protection circuit, including:

the sampling module is provided with a voltage input end for receiving an external voltage, a first output end for outputting a first sampling voltage related to the current temperature according to the external voltage, and a second output end for outputting a second sampling voltage unrelated to the current temperature according to the external voltage; and the number of the first and second groups,

an over-temperature protection module comprising a sample-and-hold device for outputting a corresponding voltage according to the current temperature and the voltage received by the over-temperature protection module, a reference voltage generator for making the voltage output by the over-temperature protection module and the voltage received by the over-temperature protection module in a functional relation, and a comparator for comparing the voltages;

the voltage receiving end of the sampling holder is connected with the second output end, the output end of the sampling holder is connected with the voltage receiving end of the reference voltage generator, one input end of the comparator is connected with the output end of the reference voltage generator, the other input end of the comparator is connected with the first output end, and the output end of the comparator outputs an over-temperature protection signal; alternatively, the first and second electrodes may be,

the voltage receiving end of the reference voltage generator is connected with the second output end, the output end of the reference voltage generator is connected with the voltage receiving end of the sampling holder, one input end of the comparator is connected with the output end of the sampling holder, the other input end of the comparator is connected with the first output end, and the output end of the comparator outputs an over-temperature protection signal.

Optionally, the sampling module further comprises a first voltage-dividing resistor, a second voltage-dividing resistor, a third voltage-dividing resistor and a thermistor, wherein the first voltage-dividing resistor and the second voltage-dividing resistor are connected in series between a voltage input terminal of the sampling module and ground, and a series node between the first voltage-dividing resistor and the second voltage-dividing resistor is the second output terminal; the third voltage dividing resistor and the thermistor are connected in series between the voltage input end of the sampling module and the ground, and the series node between the third voltage dividing resistor and the thermistor is the first output end.

Optionally, the sampling module further comprises a diode connected in series between the thermistor and the voltage input of the sampling module.

Optionally, the functional relationship is a linear relationship.

Optionally, the functional relationship is a proportional relationship.

Based on same utility model the design, the utility model also provides an electronic product, include the over-temperature protection circuit.

Optionally, the electronic product further comprises a power supply module for generating the external voltage.

Optionally, the power supply module includes an AC input power source, a rectifier bridge, a voltage-stabilizing capacitor, a primary inductor of the transformer, a secondary inductor of the transformer, a primary power MOS transistor, a secondary rectifier diode, an output resistor, an output capacitor, and a primary detection resistor, one end of the AC input power source is grounded, the other end of the AC input power source is connected to the input end of the rectifier bridge, the output end of the rectifier bridge is connected to one end of the voltage-stabilizing capacitor and one end of the primary inductor of the transformer, the other end of the voltage-stabilizing capacitor is grounded, the primary power MOS transistor and the primary detection resistor are connected in series between the other end of the primary inductor of the transformer and ground, the secondary rectifier diode and the output resistor are connected in series between two ends of the secondary inductor of the transformer, a series node between the output resistor and the secondary inductor of the transformer is grounded, and one end of the output capacitor is connected to a series node between, the other end of the output capacitor is grounded.

Optionally, the electronic product is a switching power supply product.

Optionally, the switching power supply product is a charger, L ED lighting, communication equipment, instrumentation equipment, medical equipment, computer chassis, or portable digital equipment.

Compared with the prior art, the technical scheme of the utility model following beneficial effect has:

the method comprises the steps that a first sampling voltage relevant to the current temperature and the input external voltage and a second sampling voltage irrelevant to the current temperature and relevant to the input external voltage are collected through a sampling module, a reference voltage is generated according to the second sampling voltage, then the reference voltage can be relevant to the external voltage, and the relevance of an over-temperature protection threshold point and the external voltage is greatly reduced or even completely irrelevant through mutual offset of the reference voltage and the external voltage in the second sampling voltage, namely when the external voltage received by an over-temperature protection circuit changes, the over-temperature protection circuit can accurately protect the product at the same or similar temperature threshold point, so that the over-temperature protection circuit can meet the requirement of over-temperature protection of certain products needing multi-voltage output or input⁺And (5) a protection function.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic circuit diagram of a conventional AC/DC power supply system with an over-temperature protection function.

Fig. 2 is a schematic circuit diagram of an over-temperature protection circuit according to an embodiment of the present invention.

Fig. 3 is a schematic circuit diagram of an electronic product according to an embodiment of the present invention.

Fig. 4 is a schematic circuit diagram of an over-temperature protection circuit according to another embodiment of the present invention.

Fig. 5 is a schematic circuit diagram of an electronic product according to another embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

As described in the background section, in the conventional AC/DC power supply having the overheat protection circuit, the reference voltage of the overheat protection circuit is a fixed value and does not follow the output voltage V of the AC/DC power supply_OUTThe change is changed, which is the reason that the traditional over-temperature protection circuit is not suitable for the product with multi-voltage output. Therefore, the utility model discloses a change sampling module and comparison module among the excess temperature protection circuit for reference voltage and V_OUTCorrelation by reference voltage and output voltage V_OUTSo that the over-temperature protection threshold point T is offset_CTH1And V_OUTThe correlation is greatly reduced.

The over-temperature protection circuit and the electronic product using the over-temperature protection circuit of the present invention will be described in detail with reference to fig. 2 to 5 and specific embodiments.

Referring to FIG. 2, an embodiment of the present inventionThe embodiment provides an over-temperature protection circuit, which comprises a sampling module 20 and an over-temperature protection module 30. The sampling module 20 is used for receiving an external voltage V_kAnd according to said external voltage V_kGenerating a first sampling voltage V related to the current temperature_SAMPLEAnd a second sampling voltage V independent of the current temperature_DEM. In this embodiment, the sampling module 20 includes a diode D115, a first voltage-dividing resistor R109, a second voltage-dividing resistor R110, a third voltage-dividing resistor R111, and a thermistor R113, wherein the first voltage-dividing resistor R109 and the second voltage-dividing resistor R110 are connected in series at a voltage input end V of the sampling module 20_kAnd ground, and a series node n1 between the first voltage-dividing resistor R109 and the second voltage-dividing resistor R110 is a second output terminal of the sampling module 20, for outputting a second sampling voltage V_DEM. The third voltage dividing resistor R111 and the thermistor R113 are connected in series at the voltage input end V of the sampling module_kAnd ground, and a series node n2 between the third voltage dividing resistor R111 and the thermistor R113 is a first output terminal of the sampling module 20, for outputting a first sampling voltage V_SAMPLE. A diode D115 is connected in series between the thermistor R113 and the voltage input end V of the sampling module 20_kAnd the voltage stabilizing module is used for stabilizing the input of the sampling module.

The over-temperature protection module 30 is used for implementing an accurate over-temperature protection function according to the sampling result of the sampling module 20, and the over-temperature protection module 30 includes a sample holder 314 for outputting a corresponding voltage according to the current temperature T and the voltage received by the sample holder, a reference voltage generator 315 for making the voltage output by the sample holder and the voltage received by the sample holder be in a functional relationship, and a comparator 316 for comparing the voltages. In this embodiment, the voltage receiving terminal of the sample-and-hold unit 314 is connected to the second output terminal (i.e. the node n1) to receive the second sampled voltage V_DEMThe output terminal of the sample holder 314 is connected to the voltage receiving terminal of the reference voltage generator 315, and the sample holder 314 holds the second sample voltage V according to the current temperature_DEMSampled as the voltage V required by the reference voltage generator 315_{DEMG_Sample}The reference voltage generator 315 can convert the output voltage and the input voltage into a functional relationship, such as a linear relationship or a proportional relationship (proportional relationship), i.e. the voltage V_{DEMG_Sample}Is converted into a reference voltage V through a corresponding functional relation_REFOne input terminal of the comparator 316 is connected to the output terminal of the reference voltage generator 315, and the other input terminal of the comparator 316 is connected to the first output terminal (i.e., the node n2) to receive the first sampling voltage V_SAMPLEThe comparator 316 compares the first sampling voltage V_SAMPLEAnd a reference voltage V_REFAnd according to the comparison result, the over-temperature protection signal OTP _ EN. The sample-and-hold device 314 may be a sample-and-hold chip known to those skilled in the art, and the reference voltage generator may be a circuit composed of a multiplier, a subtractor, and the like. The thermistor R113 is a negative temperature coefficient thermistor, and has a characteristic that the higher the temperature is, the lower the resistance value R (t) is, and the resistance value formula is shown in formula (1) in the background art, which is not described herein again. In other embodiments of the present invention, the thermistor R113 can also be a positive temperature coefficient thermistor.

In this embodiment, the external voltage V connected to the anode of the diode D115_KIs a and an output voltage V_OUTThe voltage values of the related voltages are specifically: v_k＝K0×(V_OUT+V_D106)，V_D106K0 is a fixed multiple of the voltage across the secondary rectifier diode D106. Therefore, the working principle of the over-temperature protection circuit of the embodiment is as follows: a first voltage dividing resistor R109 and a second voltage dividing resistor R110 for detecting the external voltage V_K(i.e. the output voltage V of the voltage generating module_OUT) And outputs a second sampling voltage V independent of the current temperature_DEMAnd then the second sampled voltage V is applied through the sample-and-hold unit 314_DEMSampling to generate V_{DEMG_Sample}Voltage, then, V is coupled through the reference voltage generator 315_{DEMG_Sample}The voltage is subjected to functional relation processing to generate a reference voltage V_REF(ii) a The third voltage dividing resistor R111 and the thermistor R112 also detect the external voltage V_K(i.e. the output voltage V of the power supply module_OUT) And outputs a first sampling voltage V related to the current temperature_SAMPLE(ii) a Finally, the first sampling voltage V_SAMPLEAnd V_REFThe over-temperature protection signal OTP _ EN is obtained through comparison by the comparator 316.

The following describes the effect of the over-temperature protection circuit of this embodiment in detail with reference to fig. 3, taking as an example that the function of the reference voltage generator 315 is to make the output voltage and the input voltage thereof have a linear relationship. That is, at this time, V_REF＝K1*(V_{DEMG_Sample}-V_OFFSET) In which V is_OFFSET＝V_D115R110/(R110+ R109); to simplify the formula, we assume V_{DEMG_Sample}Is equal to V_DEM。

This gives:

wherein V_D115Is the voltage difference across diode D115. Also as can be seen from fig. 3:

V_K＝(V_OUT+V_D106)×K0.................................................(9)

from the formulae (9), (10), (11):

substituting the above formula into formula (5) can obtain:

as can be seen from the above equation (13), the over-temperature protection threshold point T_CTHAnd V_OUTIs irrelevant. Therefore, when the voltage V is output_OUTAt a different time,over-temperature protection threshold point T_CTHAre identical.

Thus, the over-temperature protection circuit of the present embodiment is described, which has an over-temperature protection threshold point T_CTHWith the external voltage V received thereby_KIndependent of variations (i.e. for the output voltage V of the electrical module)_OUTIndependent of the change of the voltage), can be suitable for the requirement of the over-temperature protection function of various voltage output or input electronic products.

It should be noted that, in the technical solution of the present invention, the functional relationship of the reference voltage generator 315 is not limited to the linear relationship, but may be other functional relationships, such as a quadratic functional relationship, a proportional relationship, and the like. The proportional relationship is equivalent to further simplifying the function of the reference voltage generator 315, so that the simplified function of the reference voltage generator 315 is to make the output voltage thereof have a proportional relationship with the input voltage thereof, i.e., V_REF＝K1*V_{DEMG_Sample}. K1 is a proportionality constant, which is proportional when K1 is greater than or equal to 1 and inversely proportional when K1 is greater than 0 and less than 1. In this case, the over-temperature protection threshold point T of the over-temperature protection circuit_CTHTo an external voltage V_KIs still related (i.e. to the output voltage V of the power supply module)_OUTIs still relevant), but the relevance is greatly reduced compared with the traditional over-temperature protection circuit. Specifically, as can be seen from fig. 2 and 3:

V_K＝(V_OUT+V_D106)×K0................................................(14)

V_REF＝K1×V_DEM.....................................................(16)

from the formulae (14), (15), (16):

substituting the above formula into formula (5) can obtain:

as can be seen from the above equation (18), the over-temperature protection threshold point T_CTHIs still in contact with V_OUTAnd (4) correlating. In practice, however, the V is different from the over-temperature detection of the conventional over-temperature protection circuit shown in FIG. 1_OUTResulting over-temperature protection threshold point T_CTHThe deviation will become much smaller, and the specific analysis is as follows:

assume that there are two output voltages of the power supply module: v_OUT0And V_OUT1Their corresponding reference voltages are respectively V_REF0And V_REF1The corresponding over-temperature protection threshold points (i.e. two temperature thresholds) are T_CTH0And T_CTH1Output voltage V_OUT0And V_OUT1The difference of (d) is Δ V.

From equation (15), one can derive:

from equation (18), one can obtain:

from equations (19) to (22), it can be found that:

for convenience of comparison with the conventional over-temperature protection circuit shown in fig. 1, we assume that the output V is output V_OUT0As a basis for the systemQuasi point, so accordingly, V_REF0And V in FIG. 1_REFAre equal.

Comparing equation (8) yields:

in general

Therefore, the thermistor difference Δ R corresponding to the equation (23)_MODWill be much smaller than the thermistor difference value DeltaR corresponding to the formula (8)_ORGTherefore, the difference of the over-temperature protection threshold points is greatly reduced under different output voltages.

The following examples demonstrate the superiority of the over-temperature protection circuit over the conventional over-temperature protection circuit shown in fig. 1. For convenience of comparison, we assume that the over-temperature protection circuit of the present invention and the conventional over-temperature protection circuit shown in fig. 1 have the same system parameters, namely: k0 ═ 2.33, R111 ═ 1kohm (K Ω), V_OUT0＝3V，V_OUT1＝5V，R109＝18kohm，R110＝200kohm，V_D115＝0.6V，V_D106＝0.5V。

From the formula (17): when V is_OUT0When equal to 3V, V_REF00.308V, which is the same as V in the conventional over-temperature protection circuit shown in fig. 1_REFAre equal.

From the formula (23), Δ R_MOD706ohm, much less than Δ R_ORG＝15kohm。

Similarly, looking up the table with the thermistor R113 type VISHAY NTC L E100E3(100K) resistor as a reference, if V is_OUT0Overtemperature protection threshold point T corresponding to 3V_CTH0At 120 ℃ then V_OUT1Over-temperature protection threshold point T corresponding to 5V_CTH1At 112 ℃ and a difference of only 8 ℃. Compared with the T of the traditional over-temperature protection circuit_CTH0And T_CTH1The difference between them is 60 c, which is clearly much better.

Therefore, even though the functional relationship of the reference voltage generator 315 of the present embodiment is simplified to a proportional relationship, the over-temperature protection circuit of the present embodiment can still meet the over-temperature protection requirements of some electronic products with multiple voltage outputs or inputs, and can provide an accurate over-temperature protection function for the electronic products.

Based on the same utility model concept, please refer to fig. 3, an embodiment of the present invention further provides an electronic product, including the over-temperature protection circuit shown in fig. 2. Wherein the electronic product further comprises an external voltage V for generating the over-temperature protection circuit_KIn this embodiment, the power supply module includes an AC input power source 100, a rectifier bridge 101, a voltage stabilizing capacitor C102, a transformer primary inductor L, a transformer secondary inductor L, a primary power MOS transistor M105, a secondary rectifier diode D106, an output resistor R107, an output capacitor C108, and a primary detection resistor R112, one end of the AC input power source 100 is grounded, the other end is connected to an input end of the rectifier bridge 101, an output end of the rectifier bridge 101 is connected to one end of the voltage stabilizing capacitor C102 and one end of the transformer primary inductor L, the other end of the voltage stabilizing capacitor C102 is grounded, the primary power MOS transistor M105 and the primary detection resistor R112 are connected in series between the other end of the transformer primary inductor L103 and ground, the secondary rectifier diode D106 and the output resistor R107 are connected in series between two ends of the transformer secondary inductor L, a series node n3 between the output resistor R107 and the transformer secondary inductor L is grounded, one end of the output capacitor C108 is connected in series between the rectifier diode D106 and the secondary inductor R107, and the output node n 8678 provides an output voltage V for the output node n 8678, and the output voltage of the output capacitor C108 is connected in series for providing a power supply voltage to the external ground, and the external voltage supply module_OUT. In this embodiment, the external voltage V connected to the anode of the diode D115 of the sampling module 20_KIs a and an output voltage V_OUTThe voltage values of the related voltages are specifically: v_k＝K₀×(V_OUT+V_D106)，V_D106K0 is a fixed multiple of the voltage across the secondary rectifier diode D106.

The switching power supply product is industrial automation and control equipment, military equipment, scientific research equipment, L ED lighting equipment, communication equipment, electromechanical equipment, instrumentation equipment, medical equipment, semiconductor refrigeration and heating equipment, air purifier, refrigerator, liquid crystal display equipment, audio-visual equipment, computer case, portable digital equipment, etc.

Referring to fig. 4, in an over-temperature protection circuit according to another embodiment of the present invention, a reference voltage may be generated by another method. For example, the positions of the reference voltage generator and the sample holder in the over-temperature protection module are swapped. Specifically, the over-temperature protection circuit includes a sampling module 20 and an over-temperature protection module 40, where a circuit structure of the sampling module 20 is the same as that of the sampling module 20 in the over-temperature protection circuit shown in fig. 2, and reference may be specifically made to the above description, which is not described herein again. The over-temperature protection module 40 comprises a sample holder 415, a reference voltage generator 414, and a comparator 416, wherein a voltage receiving terminal of the reference voltage generator 414 is connected to the second output terminal (i.e., the node n1) to receive the second sampled voltage V_DEMAn output terminal of the reference voltage generator 414 is connected to a voltage receiving terminal of the sample holder 415, an input terminal of the comparator 416 is connected to an output terminal of the sample holder 415, and the comparator 416₊Is connected to the first output terminal (i.e., node n2) to receive a first sampled voltage V_SAMPLEThe output end of the comparator 416 outputs an over-temperature protection signal OTP _ EN.

The working principle of the over-temperature protection circuit of the embodiment is as follows: a first voltage dividing resistor R109 and a second voltage dividing resistor R110 for detecting the external voltage V_K(i.e. the output voltage V of the voltage generating module_OUT) And outputs a second sampling voltage V independent of the current temperature_DEMThe reference voltage generator 414 generates a second sampling voltage V_DEMPerforming functional relation processing to generate V_{REF_PRE}The signal is then passed through a sample and hold unit 415 to pair V according to the current temperature_{REF_PRE}The signal is sampled to generate a reference voltage V_REFA signal; a third voltage dividing resistor R111 and a thermistor R112Also detects the external voltage V_K(i.e. the output voltage V of the power supply module_OUT) And outputs a first sampling voltage V related to the current temperature_SAMPLE(ii) a Finally, the first sampling voltage V_SAMPLEAnd V_REFThe over-temperature protection signal OTP _ EN is obtained through comparison by the comparator 416. When the function of the reference voltage generator 414 is to make its output voltage in linear or proportional relationship with its input voltage, the reference voltage V_REFIs still (V)_OUT+V_D106) Linearly related, i.e. V_REF＝K1*(V_DEM-V_OFFSET) Or V_REF＝K1*V_DEMIn which V is_OFFSET＝V_D115R110/(R110+ R109). That is, the over-temperature protection circuit of the present embodiment is substantially the same as the over-temperature protection circuit of the embodiment shown in fig. 2, and can achieve the same over-temperature protection effect, except that the sampling and holding positions are different. Therefore, the over-temperature protection circuit of the embodiment specifically reduces or avoids the correlation between the over-temperature protection threshold point and the change of the external voltage (i.e., how to avoid the over-temperature protection threshold point and the output voltage V of the power supply module)_OUTThe correlation between the changes) can be referred to the above description, and the detailed description thereof is omitted.

Referring to fig. 5, based on this, the present embodiment further provides an electronic product including the over-temperature protection circuit shown in fig. 4. Wherein the electronic product further comprises an external voltage V for generating the over-temperature protection circuit_KIn this embodiment, the power supply module includes an AC input power source 100, a rectifier bridge 101, a voltage-stabilizing capacitor C102, a transformer primary inductor L103, a transformer secondary inductor L104, a primary power MOS transistor M105, a secondary rectifier diode D106, an output resistor R107, an output capacitor C108, and a primary detection resistor R112, one end of the AC input power source 100 is grounded, the other end of the AC input power source is connected to an input end of the rectifier bridge 101, an output end of the rectifier bridge 101 is connected to one end of the voltage-stabilizing capacitor C102 and one end of the transformer primary inductor L103, the other end of the voltage-stabilizing capacitor C102 is grounded, the primary power MOS transistor M105 and the primary detection resistor R112 are connected in series to the transformer, and the primary power MOS transistor M105 and the primary detectionThe other end of the primary inductor L103 of the transformer is connected to ground, the secondary rectifying diode D106 and the output resistor R107 are connected in series between two ends of the secondary inductor L104 of the transformer, the series node n3 between the output resistor R107 and the secondary inductor L104 of the transformer is grounded, one end of the output capacitor C108 is connected to the series node n4 between the secondary rectifying diode D106 and the output resistor R107, the other end of the output capacitor C108 is grounded, and the series node n4 is a voltage output end of the power supply module and is used for providing an output voltage V outwards_OUT. In this embodiment, the external voltage V connected to the anode of the diode D115 of the sampling module 20_KIs a and an output voltage V_OUTThe voltage values of the related voltages are specifically: v_k＝K0×(V_OUT+V_D106)，V_D106K0 is a fixed multiple of the voltage across the secondary rectifier diode D106.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An over-temperature protection circuit, comprising:

2. The over-temperature protection circuit of claim 1, wherein the sampling module further comprises a first voltage-dividing resistor, a second voltage-dividing resistor, a third voltage-dividing resistor, and a thermistor, wherein the first voltage-dividing resistor and the second voltage-dividing resistor are connected in series between a voltage input terminal of the sampling module and ground, and a series node between the first voltage-dividing resistor and the second voltage-dividing resistor is the second output terminal; the third voltage dividing resistor and the thermistor are connected in series between the voltage input end of the sampling module and the ground, and the series node between the third voltage dividing resistor and the thermistor is the first output end.

3. The over-temperature protection circuit of claim 2, wherein the sampling module further comprises a diode connected in series between the thermistor and a voltage input of the sampling module.

4. The over-temperature protection circuit of claim 1, wherein the functional relationship is a linear relationship.

5. The over-temperature protection circuit of claim 1, wherein the functional relationship is a proportional relationship.

6. An electronic product characterized by comprising the excess temperature protection circuit according to any one of claims 1 to 5.

7. The electronic product of claim 6, further comprising a power supply module for generating the external voltage.

8. The electronic product according to claim 7, wherein the power supply module comprises an AC input power source, a rectifier bridge, a voltage stabilizing capacitor, a primary inductor of a transformer, a secondary inductor of the transformer, a primary power MOS transistor, a secondary rectifier diode, an output resistor, an output capacitor, and a primary detection resistor, one end of the AC input power source is grounded, the other end of the AC input power source is connected to an input end of the rectifier bridge, an output end of the rectifier bridge is connected to one end of the voltage stabilizing capacitor and one end of the primary inductor of the transformer, the other end of the voltage stabilizing capacitor is grounded, the primary power MOS transistor and the primary detection resistor are connected in series between the other end of the primary inductor of the transformer and ground, the secondary rectifier diode and the output resistor are connected in series between two ends of the secondary inductor of the transformer, and a series node of the output resistor and the secondary inductor of the transformer is grounded, one end of the output capacitor is connected with a series node between the secondary side rectifier diode and the output resistor, and the other end of the output capacitor is grounded.

9. The electronic product according to any one of claims 6 to 8, wherein the electronic product is a switching power supply product.

10. An electronic product according to claim 9, wherein the switching power supply product is a charger, L ED lighting, communications equipment, instrumentation equipment, medical equipment, computer chassis, or portable digital equipment.