CN204464953U - Low temperature protection circuits and electronic devices - Google Patents

Abstract

The utility model provides a kind of low-temperature protection circuit and electronic installation, and this low-temperature protection circuit comprises thermistor element, voltage comparator, and is arranged on the switching tube between source input voltage and DC-DC voltage conversion chip.Thermistor element is connected with the in-phase input end of voltage comparator, for sampling to obtain the sampled voltage being input to voltage comparator in-phase input end to driving voltage; The inverting input of voltage comparator connects reference voltage; Switching tube is respectively with output, the source input voltage of voltage comparator and state DC-DC voltage conversion chip and be connected; Voltage comparator is used for the size by comparing sampled voltage and reference voltage, exports output voltage with the conducting of control switch pipe or cut-off.When for protection cryogenic temperature point, switching tube ends, and the input terminal voltage of DC-DC voltage conversion chip is zero, realizes at wish protection cryogenic temperature point the protection of DC-DC voltage conversion chip backend electronics device.

Description

Low temperature protection circuits and electronic devices

technical field

The utility model relates to the field of circuits, in particular to a low-temperature protection circuit and an electronic device.

Background technique

Electronic equipment such as communication equipment, lighting equipment, etc., will contain many electronic devices or integrated circuit chips with different functions. However, these devices often need to work continuously for a long time, and during their continuous work, the ambient temperature of the work may have a large change.

Many electronic devices or chips in these devices will cause irreversible damage when working under low temperature conditions due to limitations of materials or manufacturing processes, which will easily cause these devices to work abnormally. Therefore, in order to ensure the reliability of each electronic device or chip in a low temperature environment, it is urgent to provide a low temperature protection circuit to ensure the safety and reliability of the electronic device in a low temperature environment.

Utility model content

The utility model provides a low-temperature protection circuit and an electronic device, which are used to overcome the defect that the existing electronic devices are easily damaged in a low-temperature environment.

The first aspect of the utility model is to provide a low-temperature protection circuit, including: a thermistor element, a voltage comparator, and a switch tube arranged between the source input voltage and the DC-DC DC-DC voltage conversion chip;

The thermistor element is connected to the non-inverting input terminal of the voltage comparator, and is used to sample the driving voltage to obtain a sampling voltage, and input the sampling voltage to the non-inverting input terminal of the voltage comparator, the The inverting input terminal of the voltage comparator is connected to the reference voltage;

The switch tube is respectively connected to the output terminal of the voltage comparator, the input voltage of the source terminal and the DC-DC voltage conversion chip;

The voltage comparator is used to output an output voltage by comparing the magnitude of the sampling voltage with the reference voltage, so as to control the turn-on or cut-off of the switch tube.

In the low temperature protection circuit described above, the voltage comparator is specifically used to output a first output voltage when the ambient temperature is less than or equal to the low temperature point to be protected, and the sampling voltage is greater than the reference voltage, and the first output The voltage difference between the voltage and the input voltage of the source terminal is within the threshold voltage range of the switch tube, and the switch tube is turned off;

The voltage comparator is also used to output a second output voltage when the ambient temperature is higher than the low temperature point to be protected and the sampling voltage is lower than the reference voltage, and the second output voltage is the same as the source input voltage The voltage difference is outside the threshold voltage range of the switch tube, and the switch tube is turned on.

In the low temperature protection circuit described above, the switch tube includes a field effect MOS tube, the gate of the MOS tube is connected to the output terminal of the voltage comparator, and the source of the MOS tube is connected to the source terminal input voltage connected, the drain of the MOS transistor is connected to the DC-DC voltage conversion chip.

The low temperature protection circuit described above also includes:

a first resistor, one end of the first resistor is connected to the driving voltage, the other end of the first resistor is connected to one end of the thermistor element, and the other end of the thermistor element is grounded; One end of the thermistor element is connected to the non-inverting input end of the voltage comparator.

The low temperature protection circuit described above also includes:

A second resistor and a third resistor, one end of the second resistor is connected to a preset voltage, the other end of the second resistor is connected to one end of the third resistor, and the other end of the third resistor is grounded; One end of the third resistor is connected to the inverting input end of the voltage comparator.

In the low temperature protection circuit described above, the voltage comparator has a push-pull output structure.

In the low temperature protection circuit as described above, the voltage comparator has an open-drain output structure, and the low temperature protection circuit further includes a fourth resistor;

One end of the fourth resistor is connected to the control voltage of the switching tube, and the other end of the fourth resistor is connected to the output end of the voltage comparator.

The low temperature protection circuit described above also includes:

At least one first filter capacitor, one end of the at least one first filter capacitor connected in parallel is connected to the input voltage of the source terminal, and the other end is grounded;

The at least one first filter capacitor is used to filter the ripple in the input voltage of the source terminal.

The low temperature protection circuit described above also includes:

At least one second filter capacitor, one end of the at least one second filter capacitor connected in parallel is connected to the input end of the DC-DC voltage conversion chip, and the other end is grounded;

The at least one second filter capacitor is used to filter the ripple in the voltage input by the switch tube to the DC-DC voltage conversion chip when the switch tube is turned on.

The low temperature protection circuit described above also includes:

At least one third filter capacitor, one end of the at least one third filter capacitor connected in parallel is connected to the non-inverting input end of the voltage comparator, and the other end is grounded;

The at least one third filter capacitor is used to filter ripples in the sampling voltage.

The second aspect of the utility model is to provide an electronic device, including the low temperature protection circuit as described above, as well as a DC-DC voltage conversion chip, load electronic devices, source input voltage and driving voltage;

The source terminal input voltage is connected to the switch tube in the low temperature protection circuit;

The driving voltage is connected to the thermistor element in the low temperature protection circuit;

The input end of the DC-DC voltage conversion chip is connected to the switch tube in the low temperature protection circuit, and the output end of the DC-DC voltage conversion chip is connected to the load electronic device.

The low temperature protection circuit and the electronic device provided by the utility model include a low temperature protection circuit, a DC-DC voltage conversion chip and a load electronic device connected in sequence, wherein the low temperature protection circuit is composed of a thermistor element, a voltage comparator , and a switch tube arranged between the input voltage at the source end and the DC-DC voltage conversion chip. By using a thermistor element whose resistance value changes with temperature, when it reaches or falls below the low temperature to be protected, the input-to-voltage comparison is obtained by sampling the preset driving voltage according to the thermistor element of the corresponding resistance value. The sampling voltage of the non-inverting input terminal of the comparator makes the voltage comparator output a high-level output voltage when the voltage comparator confirms that the sampling voltage is greater than the reference voltage of its inverting input terminal, thereby controlling the switch tube to be cut off. The switch tube is cut off so that the input voltage of the DC-DC voltage conversion chip is zero, so that the output voltage of the DC-DC voltage conversion chip is also zero, so as to protect the load electronic devices at the back end of the DC-DC voltage conversion chip when the low temperature is to be protected. Purpose.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are only some embodiments of the present utility model, and those skilled in the art can also obtain other drawings according to these drawings without creative work.

Fig. 1 is the circuit diagram of the low temperature protection circuit provided by the utility model embodiment one;

Fig. 2 is the circuit diagram of the low temperature protection circuit provided by the second embodiment of the utility model;

Fig. 3 is a graph showing the resistance value of the TSM0A103F34D model NTC thermistor changing with temperature;

Fig. 4 is the circuit diagram of the low temperature protection circuit provided by the third embodiment of the utility model;

Fig. 5 is a circuit diagram of the low temperature protection circuit provided by the fourth embodiment of the utility model;

Fig. 6 is the voltage change curve diagram of the MOS transistor drain in the embodiment shown in Fig. 4;

FIG. 7 is a schematic structural diagram of an electronic device provided by Embodiment 5 of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. example. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without creative efforts belong to the scope of protection of the present utility model.

The basic principle of the low temperature protection circuit provided by each embodiment of the utility model is: voltages such as 3.3V, 1.8V, 1.5V, and 1.2V are the level values often used in current low-voltage application circuits, and most of these level values are passed through DC -DC voltage conversion chip obtained. Therefore, in order to achieve the purpose of protecting the electronic devices or chips at the back end of the DC-DC voltage conversion chip under low temperature conditions, it can be achieved by controlling the input voltage of the DC-DC voltage conversion chip by using the low temperature protection circuit provided by each embodiment of the utility model . Specifically, if the input voltage of the DC-DC voltage conversion chip is zero at the low temperature point to be protected, that is, at this temperature point and below this temperature point, its output voltage will also be zero, and thus lies behind it. Each electronic device or chip at the end will not work and is protected.

Fig. 1 is the circuit diagram of the low temperature protection circuit provided by the first embodiment of the utility model. As shown in Fig. 1, the low temperature protection circuit includes: a thermistor element, a voltage comparator U1, and an input voltage POWER_INPUT and DC- The switch tube between DC DC-DC voltage conversion chips;

The thermistor element is connected to the non-inverting input terminal IN+ of the voltage comparator U1, and is used to sample the driving voltage to obtain a sampling voltage, and input the sampling voltage to the non-inverting input terminal IN+ of the voltage comparator , the inverting input terminal IN- of the voltage comparator is connected to a reference voltage;

The switch tube is respectively connected to the output terminal OUT of the voltage comparator, the source input voltage POWER_INPUT and the DC-DC voltage conversion chip;

The voltage comparator U1 is used to output an output voltage by comparing the sampling voltage with the reference voltage to control the switching on or off of the switching tube.

Wherein, specifically, the voltage comparator U1 outputs the first output voltage V1 _OUT when the ambient temperature is less than or equal to the low temperature point to be protected and the sampling voltage is greater than the reference voltage, and the first output voltage V1 _OUT is connected to the source terminal The voltage difference between the input voltages POWER_INPUT is within the threshold voltage range of the switch tube, and the switch tube is turned off;

The voltage comparator U1 outputs a second output voltage V2 _OUT when the ambient temperature is higher than the low temperature point to be protected and the sampling voltage is lower than the reference voltage, and the voltage difference between the second output voltage V2 _OUT and the source input voltage POWER_INPUT is value is outside the threshold voltage range of the switch tube, the switch tube is turned on. In a specific implementation, the above-mentioned switch tube may be, for example, a triode or a MOS tube, preferably a MOS tube; the above-mentioned thermistor element is preferably a negative temperature coefficient thermistor NTC, but it is not limited thereto. Taking the switch tube as the MOS tube Q1 and the thermistor element as the negative temperature coefficient thermistor NTC as an example, as shown in FIG. 2 , the specific working process of the low temperature protection circuit in this embodiment will be described.

As shown in Figure 2, the negative temperature coefficient thermistor NTC is connected to the non-inverting input terminal IN+ of the voltage comparator U1, and is used to sample the driving voltage to obtain a sampling voltage, and input the sampling voltage to the voltage The non-inverting input terminal IN+ of the comparator.

Optionally, as shown in FIG. 2, the low temperature protection circuit further includes: a first resistor R1, one end of the first resistor R1 is connected to the driving voltage, and the other end of the first resistor R1 is connected to the negative temperature coefficient thermistor NTC. One end is connected, and the other end of the negative temperature coefficient thermistor NTC is grounded; one end of the negative temperature coefficient thermistor NTC is connected to the non-inverting input terminal IN+ of the voltage comparator U1. Therefore, the sampling voltage input to the non-inverting input terminal IN+ of the voltage comparator U1 is obtained by dividing the driving voltage through the negative temperature coefficient thermistor NTC and the first resistor R1. Wherein, the value of the driving voltage can be determined as different voltage values according to different models of the selected negative temperature coefficient thermistor NTC, for example, it can be set to 12V; the value of the first resistor can be preset according to actual needs.

The inverting input terminal IN- of the voltage comparator U1 is connected to the reference voltage, the output terminal OUT of the voltage comparator U1 is connected to the gate G of the MOS transistor, and the source S of the MOS transistor is connected to the source input Voltage POWER_INPUT, the drain D of the MOS transistor is connected to the DC-DC voltage conversion chip. Wherein, the value of the reference voltage is predetermined according to the value of the low temperature to be protected, and the low temperature to be protected is a temperature at which the MOS transistor is turned off.

Specifically, the value of the reference voltage corresponds to the value of the low temperature to be protected, and can be preset. For example, if the low temperature to be protected is set to -20°C, the reference voltage is set to 4V, for example. If the low temperature to be protected is set If the temperature is -40°C, set the reference voltage to 5V, for example. The reference voltage values mentioned above are just to illustrate that different reference voltage values can be set according to different low temperature temperatures to be protected, and should not be limited to this.

Therefore, the voltage comparator U1 compares the magnitude of the sampling voltage with the reference voltage, and if it is determined that the sampling voltage is greater than the reference voltage, then outputs the first output voltage V1 _OUT , and the first output voltage V1 _OUT is the same as the The voltage difference between the source input voltages POWER_INPUT is within the threshold voltage range of the MOS transistor, and the MOS transistor is turned off.

In addition, if the voltage comparator U1 compares and determines that the sampling voltage is lower than the reference voltage, it outputs a second output voltage V2 _OUT , and the voltage difference between the second output voltage V2 _OUT and the source input voltage POWER_INPUT is at the specified value. If the threshold voltage range of the MOS transistor is out of range, the MOS transistor is turned on.

Specifically, the low temperature to be protected above is preset. For example, it can be set to cut off the MOS tube at -20°C, so that when the temperature drops to -20°C or below -20°C, the MOS tube Cut off, so that the source input voltage POWER_INPUT cannot be transmitted through the MOS tube, so that the input voltage of the DC-DC voltage conversion chip, that is, the value of POWER_OUTPUT is zero, and low temperature protection for the back-end devices of the DC-DC voltage conversion chip is realized. The resistance value of the negative temperature coefficient thermistor NTC changes nonlinearly with the change of temperature, as shown in Figure 3. Figure 3 shows the temperature characteristic curves of several commonly used types of negative temperature coefficient thermistor NTC, as follows In the embodiment, TSM0A103F34D will be taken as an example for illustration.

It is worth noting that in practical applications, the voltage comparator U1 includes a push-pull output (push-pull output) structure and an open-drain output (open-drain output) structure. In this embodiment, the voltage comparator U1 with a push-pull output structure will be mainly introduced, and the voltage comparator U1 with an open-drain output structure will be introduced in the following embodiments.

In practical applications, when the ambient temperature changes, the resistance value of the negative temperature coefficient thermistor NTC will also change. If the current ambient temperature is higher than the preset low temperature to be protected, then through the first resistor R1 and the current The resistance value of the negative temperature coefficient thermistor NTC divides the driving voltage, and the sampling voltage obtained by the division is input to the non-inverting input terminal of the voltage comparator U1, and the voltage comparator U1 compares the sampling voltage value of the non-inverting input terminal with the inverting input A fixed reference voltage value at the terminal is compared. It should be noted that the fixed reference voltage value means that the reference voltage will be set immediately after the low temperature to be protected is preset. Furthermore, when the current ambient temperature is higher than the preset low temperature to be protected, since the sampling voltage at this time will be lower than the reference voltage, the voltage comparator U1 outputs a low-level signal at its output terminal OUT. output voltage V2 _OUT . Therefore, the gate voltage value of MOS transistor Q1 is V2 _OUT , and its source voltage is the voltage value of the source input voltage POWER_INPUT. Since the voltage value of POWER_INPUT is much greater than the gate voltage value V2 _OUT , the difference between the gate-source voltage The value will be outside the threshold voltage range of the MOS transistor Q1, and the MOS transistor Q1 is turned on. Therefore, the input voltage POWER_OUTPUT of the DC-DC voltage conversion chip is not zero, and the electronic devices or chips at the back end of the DC-DC voltage conversion chip work normally. Wherein, the voltage value of POWER_INPUT may be, for example, 5V, and the threshold voltage range of the MOS transistor Q1 is, for example, -0.5V to -1.3V.

Moreover, when the ambient temperature continues to decrease, the resistance value of the negative temperature coefficient thermistor NTC will also change. As shown in FIG. 3 , the resistance value of the negative temperature coefficient thermistor NTC will increase. If the current ambient temperature is equal to or lower than the preset low-temperature temperature to be protected, such as -20°C, the driving voltage is divided by the first resistor R1 and the resistance value of the negative temperature coefficient thermistor NTC corresponding to the current temperature, The sampled voltage obtained by voltage division is input to the non-inverting input terminal of the voltage comparator U1, and the voltage comparator U1 compares the sampled voltage value of the non-inverting input terminal with the fixed reference voltage value of the inverting input terminal. Since the sampling voltage at this time will be greater than the reference voltage when the current ambient temperature is equal to or lower than the preset low-temperature temperature to be protected, such as -20°C, the voltage comparator U1 outputs a high voltage at its output terminal OUT. level of the output voltage V1 _OUT . Therefore, the gate voltage value of MOS transistor Q1 is V1 _OUT , and its source voltage is the voltage value of the source input voltage POWER_INPUT. Since the voltage value of POWER_INPUT is basically equal to the gate voltage value V1 _OUT , the gate-source voltage The difference will be within the threshold voltage range of the MOS transistor Q1, and the MOS transistor Q1 will be cut off. Therefore, the input voltage POWER_OUTPUT of the DC-DC voltage conversion chip is zero, and the electronic devices or chips at the back end of the DC-DC voltage conversion chip do not work.

It is worth noting that, in this embodiment, since a voltage comparator with a push-pull output structure is used, the voltage comparator with a push-pull output structure is used for the value of the supply voltage VCC at the power supply terminal and the input voltage at the source terminal. The value of POWER_INPUT is limited, and the two are required to be substantially equal, that is, the voltage difference between the two is less than or equal to a preset threshold, and the preset threshold is greater than or equal to zero. In addition, the high-level value output by the output terminal of the voltage comparator U1 is also determined by the power supply voltage VCC of its power supply terminal, that is, when the sampling voltage is higher than the reference voltage, the first output voltage V1OUT output by the output terminal OUT of the voltage comparator U1 The value of is equal to the value of the power supply voltage VCC at the power supply terminal of the voltage comparator.

In addition, it is worth noting that in this embodiment and the following several embodiments, the switch is controlled by using a thermistor element whose resistance value changes with temperature, such as a negative temperature coefficient thermistor and a voltage comparator. The voltage corresponding to the output terminal of the tube such as the MOS tube and the voltage comparator makes the input voltage of the DC-DC voltage conversion chip at the low temperature point to be protected zero, so that the output voltage of the DC-DC voltage conversion chip is also zero. The purpose of protecting the device or chip at the back end of the DC-DC voltage conversion chip at the low temperature point to be protected is achieved. If the voltage comparator is not combined, the sampling voltage obtained by dividing the driving voltage by the negative temperature coefficient thermistor and the first resistor R1 is directly used to control the gate voltage of the MOS tube. Due to the resistance value of the negative temperature coefficient thermistor The change with temperature is non-linear, which will cause the MOS tube to be turned off in advance in a certain temperature range, and it is impossible to accurately turn off the MOS tube at the low temperature point to be protected.

In this embodiment, the low temperature protection circuit is composed of a thermistor element, a voltage comparator, and a switch arranged between the input voltage at the source end and the DC-DC voltage conversion chip. By using a thermistor element whose resistance value changes with temperature, when it reaches or falls below the low temperature to be protected, the input-to-voltage comparison is obtained by sampling the preset driving voltage according to the thermistor element of the corresponding resistance value. The sampling voltage of the non-inverting input terminal of the comparator makes the voltage comparator output a high-level output voltage when the voltage comparator confirms that the sampling voltage is greater than the reference voltage of its inverting input terminal, thereby controlling the switch tube to be cut off. The switch tube is cut off so that the input voltage of the DC-DC voltage conversion chip is zero, so that the output voltage of the DC-DC voltage conversion chip is also zero, so as to protect the load electronic devices at the back end of the DC-DC voltage conversion chip when the low temperature is to be protected. Purpose.

Fig. 4 is a circuit diagram of the low temperature protection circuit provided by Embodiment 3 of the present utility model. As shown in Fig. 4, the low temperature protection circuit provided by this embodiment further includes: A second resistor R2 and a third resistor R3, one end of the second resistor R2 is connected to a preset voltage, the other end of the second resistor R2 is connected to one end of the third resistor R3, and the third resistor R3 The other end of the third resistor R3 is connected to the ground; one end of the third resistor R3 is connected to the inverting input terminal IN- of the voltage comparator U1. Wherein, the value of the preset voltage is preset according to the low temperature value to be protected, for example, when the low temperature to be protected is -20°C, the voltage value of the preset voltage is set to 5V.

Therefore, the reference voltage input to the inverting input terminal IN− of the voltage comparator U1 is obtained by dividing the preset voltage by the second resistor R2 and the third resistor R3. Wherein, according to different low temperature points to be protected, the reference voltage can be changed by changing the resistance values of the resistors R2 and R3.

In actual circuit applications, in order to ensure the stability of various voltage signals in the circuit, it is necessary to add filter design in the circuit. Therefore, in this embodiment, the low temperature protection circuit further includes: at least one first filter capacitor, one end of the at least one first filter capacitor connected in parallel is connected to the input voltage of the source terminal, and the other end is grounded. The at least one first filter capacitor is used to filter out the ripple in the input voltage of the source terminal, as shown in FIG. 4 , only one first filter capacitor C1 is shown in FIG. 4 , and the specification of the first filter capacitor C1 is, for example, 0.1uF, 16V, 0402.

The low temperature protection circuit may further include: at least one second filter capacitor, one end of the at least one second filter capacitor connected in parallel is connected to the input end of the DC-DC voltage conversion chip, and the other end is grounded. When the switch tube is a MOS tube, one end of the at least one second filter capacitor connected in parallel is connected to the drain of the MOS tube, and the other end is grounded. The at least one second filter capacitor is used to filter out the ripple in the second output voltage, as shown in Figure 4, which shows the situation where the capacitor C2 and the capacitor C3 are connected in parallel to the drain of the MOS transistor , The specification of C2 is, for example, 1uF, 10V, 0402; the specification of C3 is, for example, 0.1uF, 16V, 0402.

The low temperature protection circuit may further include: at least one third filter capacitor, one end of the at least one third filter capacitor connected in parallel is connected to the non-inverting input end of the voltage comparator, and the other end is grounded. The at least one third filter capacitor is used to filter out the ripple in the sampling voltage, as shown in FIG. 4 , only one third filter capacitor C4 is shown in FIG. 4 , and the specification of C4 is, for example, 0.1uF, 16V ,0201.

Fig. 5 is a circuit diagram of the low temperature protection circuit provided by Embodiment 4 of the present utility model. As shown in Fig. 5, in the low temperature protection circuit provided by this embodiment, the voltage comparator U1 has an open-drain output structure, so that the low temperature protection On the basis of the above embodiments, the circuit further includes a fourth resistor R4, one end of the fourth resistor R4 is connected to the switching tube control voltage, and the other end of the fourth resistor R4 is connected to the output terminal OUT of the voltage comparator. When the switch tube is a MOS tube, correspondingly, one end of the fourth resistor R4 is connected to the gate control voltage VCC_CONTROL of the MOS tube, and the other end of the fourth resistor R4 is connected to the output terminal OUT of the voltage comparator U1 and the Between the gate G of the MOS transistor.

At this time, when the voltage comparator U1 adopts a voltage comparator with an open-drain output (open-drain output) structure, the high-level voltage value of the output voltage of the voltage comparator U1, that is, the voltage value of the first output voltage V1 _OUT is determined by the resistor The power supply voltage VCC_Control of R4 is determined. Specifically, the voltage value of the first output voltage V1 _OUT output by the voltage comparator U1 is determined according to the voltage value of the MOS transistor gate control voltage VCC_CONTROL, and may be equal to the voltage value of VCC_CONTROL. The working principle of the voltage comparator with an open-drain output structure is the prior art, and will not be described in detail in this embodiment.

Therefore, when the ambient temperature is higher than the low temperature point to be protected, the sampling voltage of the negative temperature coefficient thermistor NTC is lower than the reference voltage, and the voltage between the source input voltage POWER_INPUT and the MOS transistor gate control voltage VCC_Control The difference is outside the threshold voltage range of the MOS tube, and the MOS tube is turned on; when the ambient temperature is less than or equal to the low temperature point to be protected, the sampling voltage of the negative temperature coefficient thermistor NTC is greater than the reference voltage, and the The voltage difference between the source input voltage POWER_INPUT and the MOS transistor gate control voltage VCC_Control is within the threshold voltage range of the MOS transistor, and the MOS transistor is turned off.

The low temperature protection circuit for the DC-DC voltage conversion chip will be described below with a specific example in conjunction with FIG. 5 .

Among them, the voltage comparator U1 adopts a voltage comparator with an open-drain output structure, the source input voltage POWER_INPUT adopts 5V, the driving voltage sampled by the negative temperature coefficient thermistor NTC adopts 12V, and the power supply voltage VCC of the voltage comparator U1 adopts 5V , the power supply voltage VCC_CONTROL of resistor R4 adopts 4.3V, the MOS tube Q1 adopts the model AO3401A, the negative temperature coefficient thermistor NTC adopts the model TSM0A103F34D, the temperature point to protect the low temperature is -20°C, and the DC-DC voltage conversion chip adopts the model MP2161.

According to the foregoing description, it can be seen that the sampling voltage input by the non-inverting input terminal IN+ of the voltage comparator U1 can be determined according to the following formula:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{<span\; class="notranslate">\; +</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; NTC</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; NTC</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}$

Among them, V ₊ is the ground voltage of the non-inverting input terminal IN+ of the voltage comparator U1, that is, the sampling voltage of the negative temperature coefficient thermistor NTC at a certain temperature; R _NTC is the negative temperature coefficient thermistor NTC at a certain temperature The lower resistance value. Among them, when the low temperature point to be protected is -20°C, R _NTC is the resistance value of the negative temperature coefficient thermistor NTC at this temperature point. The specifications of R1 are shown in Table 1 as 130Kohm, 5%, 0402

Similarly, according to the foregoing description, it can be known that the reference voltage of the inverting input terminal IN- input of the voltage comparator U1 can be determined according to the following formula:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{<span\; class="notranslate">\; \_</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}$

Wherein, V_ is the ground voltage of the inverting input terminal IN- of the voltage comparator U1 , that is, the reference voltage. The specification of R2 is, for example, 100Kohm, 5%, 0402; the specification of R3 is, for example, 400Kohm, 5%, 0402.

In the case described in this example, the low temperature protection circuit has been tested and verified at different temperature points. As the temperature changes, the voltage changes of the three pins D, G, and S of the MOS transistor Q1 and the DC-DC voltage The voltage and current changes of the input and output terminals of the conversion chip MP2161 are shown in Table 1, and the voltage changes of the drain D of the MOS transistor Q1 are shown in Figure 6.

Table 1 Test data list at different temperatures

temperature VIN(V) Vs(V) NTC (Kohm) R1 (Kohm) Vg(V) Vgs Vd(V) Id(A) Vout(mp2161) Ven(V) Iout(A) Rout(ohm) Low temperature -40℃ 12 5 220 130 4.3 -0.7 0 0 0 0 0 4 Low temperature -30℃ 12 5 220 130 4.3 -0.7 0 0 0 0 0 4 Low temperature -20℃ 12 5 68 130 4.3 -0.7 0 0 0 0 0 4 Low temperature -18℃ 12 5 62 130 0 -5 5 0.76 3.16 4.1 0.76 4 Low temperature -16℃ 12 5 56 130 0 -5 5 0.76 3.18 4.13 0.76 4 Low temperature -15℃ 12 5 50 130 0 -5 5 0.76 3.18 4.1 0.77 4 Low temperature -10℃ 12 5 43 130 0 -5 5 0.76 3.18 4.1 0.77 4 0°C 12 5 30 130 0 -5 5 0.76 3.18 4.1 0.76 4 10°C 12 5 18 130 0 -5 5 0.76 3.18 4.1 0.77 4 25°C 12 5 11 130 0 -5 5 0.76 3.18 4.1 0.76 4

Among them, V _out is the output voltage of the DC-DC voltage conversion chip MP2161, V _en is the enable pin voltage of the DC-DC voltage conversion chip MP2161, I _out is the output current of the DC-DC voltage conversion chip MP2161, R _out is The load connected to the DC-DC voltage conversion chip MP2161.

It can be seen from Table 1 that when the ambient temperature is -20°C, the output voltage of the voltage comparator U1 is 4.3V, V _GS = -0.7V, which is within the operating voltage threshold range of the MOS transistor Q1 -0.5 to -1.3V , then the MOS transistor Q1 is in the off state, and the input voltage and output voltage of the DC-DC voltage conversion chip MP2161 are both zero, which can protect the electronic devices or chips at the back end of the DC-DC voltage conversion chip at the low temperature point to be protected. Purpose. This circuit can also be used as a detection circuit for product preheating. When the ambient temperature is higher than the temperature point to be protected, the MOS tube is turned on, and each load electronic device supplies power normally.

Fig. 7 is a schematic structural diagram of an electronic device provided by Embodiment 5 of the present utility model. As shown in Fig. 7, the electronic device includes: any low-temperature protection circuit as described in the above embodiment, a DC-DC voltage conversion chip, and a load electronics device, source input voltage POWER_INPUT, and drive voltage.

Wherein, the source input voltage POWER_INPUT is connected to the switch tube in the low temperature protection circuit; the driving voltage is connected to the thermistor element in the low temperature protection circuit;

The input end of the DC-DC voltage conversion chip is connected to the switch tube in the low temperature protection circuit, and the output end of the DC-DC voltage conversion chip is connected to the load electronic device.

The electronic device provided in this embodiment includes a low-temperature protection circuit, a DC-DC voltage conversion chip, and a load electronic device connected in sequence, wherein the low-temperature protection circuit can be any low-temperature protection circuit in the above embodiments. protect the circuit. The low temperature protection circuit uses a thermistor element whose resistance value changes with temperature, such as a negative temperature coefficient thermistor. The sampling voltage input to the non-inverting input terminal of the voltage comparator obtained by sampling the preset driving voltage, so that the voltage comparator outputs a high-level output voltage when the comparison determines that the sampling voltage is greater than the reference voltage at its inverting input terminal, thereby According to the voltage difference between the output voltage obtained by the switch tube from the output terminal of the voltage comparator and the input voltage obtained from the source terminal falls within the threshold voltage range of the switch tube, for example, when the switch tube is a MOS tube, the gate-source voltage of the MOS tube falls Within the threshold voltage range of the MOS tube, the MOS tube is controlled to be cut off, so that the input voltage of the DC-DC voltage conversion chip is zero, and the output voltage of the DC-DC voltage conversion chip is also zero, so as to protect the DC when the low temperature is to be protected. - The purpose of the load electronics at the back end of the DC voltage conversion chip.

Those of ordinary skill in the art can understand that all or part of the steps for implementing the above method embodiments can be completed by program instructions and related hardware. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps including the above-mentioned method embodiments; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other various media that can store program codes.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present utility model, and are not intended to limit it; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand : It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements to some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions depart from the various embodiments of the present invention Scope of technical solutions.

Claims (11)

1. a low-temperature protection circuit, is characterized in that, comprising: thermistor element, voltage comparator, and is arranged on the switching tube between source input voltage and DC-to-DC DC-DC voltage conversion chip;

Described thermistor element is connected with the in-phase input end of described voltage comparator, for sampling to obtain sampled voltage to driving voltage, and described sampled voltage being input to the in-phase input end of described voltage comparator, the inverting input of described voltage comparator connects reference voltage;

Described switching tube is connected with the output of described voltage comparator, described source input voltage and described DC-DC voltage conversion chip respectively;

Described voltage comparator is used for the size by more described sampled voltage and described reference voltage, exports output voltage to control conducting or the cut-off of described switching tube.

2. low-temperature protection circuit according to claim 1, it is characterized in that, described voltage comparator is specifically for being less than or equal to for protection cryogenic temperature point in ambient temperature, when described sampled voltage is greater than described reference voltage, export the first output voltage, voltage difference between described first output voltage and described source input voltage is within the threshold voltage scope of described switching tube, described switching tube cut-off;

Described voltage comparator is also described for protection cryogenic temperature point for being greater than in ambient temperature; when described sampled voltage is less than described reference voltage; export the second output voltage; the voltage difference of described second output voltage and described source input voltage is in outside the threshold voltage scope of described switching tube, described switching tube conducting.

3. low-temperature protection circuit according to claim 1; it is characterized in that; described switching tube comprises field effect metal-oxide-semiconductor; the grid of described metal-oxide-semiconductor is connected with the output of described voltage comparator; the source electrode of described metal-oxide-semiconductor is connected with described source input voltage, and the drain electrode of described metal-oxide-semiconductor is connected with described DC-DC voltage conversion chip.

4. low-temperature protection circuit according to claim 1, is characterized in that, also comprise:

First resistance, one end of described first resistance is connected with described driving voltage, and the other end of described first resistance is connected with one end of described thermistor element, the other end ground connection of described thermistor element; One end of described thermistor element is connected with the in-phase input end of described voltage comparator.

5. low-temperature protection circuit according to claim 1, is characterized in that, also comprise:

Second resistance and the 3rd resistance, one end of described second resistance is connected with predeterminated voltage, and the other end of described second resistance is connected with one end of described 3rd resistance, the other end ground connection of described 3rd resistance; One end of described 3rd resistance is connected with the inverting input of described voltage comparator.

6. low-temperature protection circuit according to claim 1, is characterized in that, described voltage comparator is for recommending export structure.

7. low-temperature protection circuit according to claim 1, is characterized in that, described voltage comparator is open-drain output structure, and described low-temperature protection circuit also comprises the 4th resistance;

One end connecting valve pipe control voltage of described 4th resistance, the other end of described 4th resistance connects the output of described voltage comparator.

8. low-temperature protection circuit according to any one of claim 1 to 7, is characterized in that, also comprise:

At least one first filter capacitor, the one end after at least one first filter capacitor parallel connection described is connected with described source input voltage, other end ground connection;

At least one first filter capacitor described, for the ripple in source input voltage described in filtering.

9. low-temperature protection circuit according to any one of claim 1 to 7, is characterized in that, also comprise:

At least one second filter capacitor, the one end after at least one second filter capacitor parallel connection described is connected with the input of described DC-DC voltage conversion chip, other end ground connection;

At least one second filter capacitor described, for described in filtering during switching tube conducting described switching tube be input to the ripple in the voltage of described DC-DC voltage conversion chip.

10. low-temperature protection circuit according to any one of claim 1 to 7, is characterized in that, also comprise:

At least one the 3rd filter capacitor, the one end after at least one the 3rd filter capacitor parallel connection described is connected with the in-phase input end of described voltage comparator, other end ground connection;

At least one the 3rd filter capacitor described, for the ripple in sampled voltage described in filtering.

11. 1 kinds of electronic installations, is characterized in that, comprise the low-temperature protection circuit according to any one of claim 1 to 10, and DC-DC voltage conversion chip, load electronic device, source input voltage and driving voltage;

Described source input voltage is connected with the described switching tube in described low-temperature protection circuit;

Described driving voltage is connected with the described thermistor element in described low-temperature protection circuit;

The input of described DC-DC voltage conversion chip is connected with the described switching tube in described low-temperature protection circuit, and the output of described DC-DC voltage conversion chip is connected with described load electronic device.