CN217739796U - SIM card automatic heating circuit based on hysteresis comparator - Google Patents
SIM card automatic heating circuit based on hysteresis comparator Download PDFInfo
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- CN217739796U CN217739796U CN202222217963.XU CN202222217963U CN217739796U CN 217739796 U CN217739796 U CN 217739796U CN 202222217963 U CN202222217963 U CN 202222217963U CN 217739796 U CN217739796 U CN 217739796U
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Abstract
The utility model relates to a SIM card automatic heating circuit based on hysteresis comparator, which comprises a voltage comparator, a triode switch and a heating resistor; the voltage comparator inputs and compares a reference voltage serving as a reference voltage and the NTC divided voltage; the output end of the voltage comparator feeds back a signal and compares the signal with a reference voltage to determine whether NTC divided voltage is input; the output end of the voltage comparator is connected with a triode switch to control the on-off of the heating resistor; the utility model relates to a rationally, compact structure and convenient to use.
Description
Technical Field
The utility model relates to a SIM card self-heating circuit based on hysteresis comparator.
Background
The wireless public network module (such as 4G, NB-IoT, GPRS and the like) needs to use the SIM card to access the network. The standard use temperature of the common plug-in SIM card is-25 ℃ to +70 ℃. In order to enable the product to work in a region with low ambient temperature, a heating circuit needs to be designed, and the SIM card is heated at low temperature.
A commonly used heating circuit is shown in fig. 1. The circuit can be divided into two parts: the left side is the heating body, and the right side is temperature detection. The temperature detection circuit reads the voltage division value of the NTC of the thermistor through an ADC interface of the MCU, and the resistance value of the NTC is calculated by combining the power supply voltage of 3.3V, so that the current temperature is obtained. When the temperature is lower than the set value, the MCU outputs high level, the triode QS1 is opened, and heating is started. And when the temperature is lower than the set value, the MCU outputs low level to close heating.
In summary, the MCU is required to participate in the operation of the circuit. In order to heat the SIM card in the module without a processor, an automatic heating circuit based on a comparator is required to be designed, and the heating is automatically started at low temperature.
SUMMERY OF THE UTILITY MODEL
The utility model aims to solve the technical problem that a SIM card self-heating circuit based on hysteresis comparator is provided overall.
In order to solve the above problems, the utility model adopts the following technical scheme:
an SIM card automatic heating circuit based on a hysteresis comparator comprises a voltage comparator, a triode switch and a heating resistor;
the voltage comparator inputs and compares a reference voltage serving as a reference voltage and the NTC divided voltage;
the output end of the voltage comparator feeds back a signal and compares the signal with a reference voltage to determine whether NTC divided voltage is input;
the output end of the voltage comparator is connected with a triode switch to control the on-off of the heating resistor.
As a further improvement of the technical scheme:
the voltage comparator comprises a hysteresis comparator TP2011 which is used as a main control chip UH1, the temperature change is converted into the voltage change by utilizing the thermistor, the voltage change is compared with a reference voltage, and the main control chip UH1 judges whether a heating circuit is opened or not to heat the SIM card;
the triode switch adopts a triode QH1 as a heating switch.
The hysteresis comparator TP2011 has two voltage thresholds Vtr and Vtf, where Vtr > Vtf; when the voltage of the NTC divided voltage at the non-inverting input terminal is higher than Vtr, the hysteresis comparator TP2011 outputs a high level; when the voltage at the non-inverting input terminal is lower than Vtf, the hysteresis comparator TP2011 outputs a low level.
The main control chip UH1 is a TP2011 comparator of a Schrepu, and the working voltage range is 1.8V-5V.
A pin 3 and Vcc of the main control chip UH1 are connected to the pin 3 through a resistor RH1, and the pin 3 is grounded through a resistor RH 2; the pin 2 is grounded, a filter capacitor CH2 is connected between the pins 3 and 4, a feedback resistor RH4 is connected between the pin 1 and the pin 3, the pin 4 is grounded through a thermistor NTC1 and is connected with VCC through a resistor RH3, the pin 5 is connected with VCC, the pin 1 is connected with a base electrode of a triode QH1 through a base electrode resistor RH5 of a Heating OUT1 channel, a collector electrode of the triode QH1 is connected with VCC, and an emitter electrode is grounded through a plurality of Heating resistors RH 6-RH 9;
the resistor RH3 and the thermistor NTC1 are divided to be used as reverse input;
VCC is connected to filter capacitor CH1 and ground.
As a mature integrated IC chip, a comparator is used in various cases, and an LM324 voltage comparator is used as a main control chip of a thermal condensation controller, and a temperature sensor converts a change in temperature into a change in current, and a condensation sensor converts a change in humidity into a change in resistance. The LM324 voltage comparator is used for controlling the temperature setting controller to realize alarm display and output.
In order to heat for the SIM card in the module that does not have the treater, the utility model discloses an automatic heating circuit of comparator, the heating is opened automatically during the low temperature, the utility model relates to a rationally, low cost, durable, safe and reliable, easy operation, labour saving and time saving, saving fund, compact structure and convenient to use.
Drawings
Fig. 1 is a diagram of a conventional heating circuit.
Fig. 2 is a schematic structural diagram of the present invention.
Fig. 3 is a temperature-resistance value map according to the present invention.
Fig. 4 is a diagram of the input-output relationship of the hysteresis comparator of the present invention.
Fig. 5 is a schematic block diagram of the automatic heating circuit of the present invention.
Fig. 6 is a circuit diagram of the automatic heating device of the present invention.
Detailed Description
Referring to fig. 2-6, a hysteresis comparator TP2011 is used as a main control chip UH1, and a thermistor is used to convert a temperature change into a voltage change, which is compared with a reference voltage. And according to the result, the comparator judges whether the heating circuit is switched on or not to heat the SIM card.
The utility model discloses a circuit uses hysteresis comparator TP2011 to replace MCU's position, through the thermistor NTC1 partial pressure and the settlement voltage size of comparison NTC type, judges whether current temperature is less than the settlement temperature. If the ambient temperature is low, the hysteresis comparator TP2011 outputs an effective level to the triode QH1, and the heating is started; if the ambient temperature is high, the hysteresis comparator TP2011 outputs an opposite level, and the heating is turned off. Thereby realizing the purpose of 'automatic heating'. FIG. 3 shows the following detailed design description:
when the temperature is reduced, the resistance value of the thermistor NTC1 is increased, and the voltage division on the resistor is increased. Therefore, the magnitude of the resistance voltage division of the thermistor NTC1 may reflect the current temperature. If the voltage division value of the thermistor NTC1 is greater than a certain voltage V1, the current temperature is lower than the temperature value represented by V1.
The hysteresis comparator TP2011 has two voltage thresholds Vtr and Vtf, typically Vtr > Vtf. When the voltage of the non-inverting input terminal is higher than Vtr, the hysteresis comparator TP2011 outputs a high level; when the voltage at the non-inverting input terminal is lower than Vtf, the hysteresis comparator TP2011 outputs a low level. The hysteretic comparator TP2011 has a more stable output than a single-limit comparator.
Referring to fig. 5, in the present embodiment, a hysteresis comparator compares NTC divided voltage with a reference voltage, and when the divided voltage value is greater than a set voltage, the comparator outputs a voltage to a base of a transistor, and turns on a switch circuit to start heating; otherwise, the heating is stopped.
The main control chip UH1 is a TP2011 comparator of a Schrepu, the working voltage range is 1.8V-5V, the power consumption is low, and the response speed is high.
The NTC thermistor selects the national JYTF05-103F3I with a relatively ideal temperature coefficient.
The voltage division of the divider resistor RH1 and RH2 is used as in-phase input, the voltage division of the resistor RH3 and the thermistor NTC1 is used as reverse input, RH4 is a feedback resistor, RH5 is a base resistor, and RH 6-RH 9 are heating resistors. And the CH1 and the CH2 are used as filter capacitors to remove errors caused by VCC fluctuation. CH1 is 100nF, CH2 is 1nF. QH1 is PNP type triode as heating switch. RH 5-RH 9 is consistent with the original circuit, and the value taking process of RH 1-RH 4 is as follows:
the two voltage thresholds Vtr and Vtf of the hysteresis comparator are calculated as follows:
heating was turned on when the temperature was reduced to-12 deg.C (NTC resistance 51K). For convenience of calculation, RH3= RH4= NTC1=51K, where Vtr is NTC1 partial pressure value: 1/2VCC. When the temperature rises to-7 ℃ (the NTC resistance value is 40K), the heating is stopped, and Vtf is the NTC partial pressure value: 4/9VCC. Substituting RH3, vtf, and Vtr into the above formula, RH1=51/9K, 5.6K, rh2=51/8K, and 6.2K were calculated.
The present invention has been fully described for clarity of disclosure, and is not further described in detail in the prior art.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; it is obvious to those skilled in the art that a plurality of embodiments of the present invention may be combined. Such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present invention. The technical contents not described in detail in the present application are all known technologies.
Claims (5)
1. The utility model provides a SIM card self-heating circuit based on hysteresis comparator which characterized in that: comprises a voltage comparator, a triode switch and a heating resistor;
the voltage comparator inputs and compares a reference voltage serving as a reference voltage and the NTC divided voltage;
the output end of the voltage comparator feeds back a signal and compares the signal with a reference voltage to determine whether NTC divided voltage is input;
the output end of the voltage comparator is connected with a triode switch to control the on-off of the heating resistor.
2. The hysteresis comparator based SIM card auto-heating circuit of claim 1, wherein: the voltage comparator comprises a hysteresis comparator TP2011 which is used as a main control chip UH1, the temperature change is converted into the voltage change by utilizing the thermistor, the voltage change is compared with a reference voltage, and the main control chip UH1 judges whether a heating circuit is opened or not to heat the SIM card;
the triode switch adopts a triode QH1 as a heating switch.
3. The hysteretic comparator-based SIM card auto-heating circuit of claim 2, characterized in that: the hysteresis comparator TP2011 has two voltage thresholds Vtr and Vtf, where Vtr > Vtf; when the voltage of the NTC divided voltage at the non-inverting input terminal is higher than Vtr, the hysteresis comparator TP2011 outputs a high level; when the voltage at the non-inverting input terminal is lower than Vtf, the hysteresis comparator TP2011 outputs a low level.
4. The hysteretic comparator-based SIM card auto-heating circuit of claim 3, characterized in that: the main control chip UH1 is a TP2011 comparator of a Schrepu, and the working voltage range is 1.8V-5V.
5. The hysteretic comparator-based SIM card auto-heating circuit of claim 3, characterized in that: a pin 3 and Vcc of the main control chip UH1 are connected to the pin 3 through a resistor RH1, and the pin 3 is grounded through a resistor RH 2; the pin 2 is grounded, a filter capacitor CH2 is connected between the pins 3 and 4, a feedback resistor RH4 is connected between the pin 1 and the pin 3, the pin 4 is grounded through a thermistor NTC1 and is connected with VCC through a resistor RH3, the pin 5 is connected with VCC, the pin 1 is connected with a base electrode of a triode QH1 through a base electrode resistor RH5 of a Heating OUT1 channel, a collector electrode of the triode QH1 is connected with VCC, and an emitter electrode is grounded through a plurality of Heating resistors RH 6-RH 9;
the resistor RH3 and the thermistor NTC1 are divided to be used as reverse input;
VCC is connected to filter capacitor CH1 and ground.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222217963.XU CN217739796U (en) | 2022-08-23 | 2022-08-23 | SIM card automatic heating circuit based on hysteresis comparator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222217963.XU CN217739796U (en) | 2022-08-23 | 2022-08-23 | SIM card automatic heating circuit based on hysteresis comparator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN217739796U true CN217739796U (en) | 2022-11-04 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202222217963.XU Active CN217739796U (en) | 2022-08-23 | 2022-08-23 | SIM card automatic heating circuit based on hysteresis comparator |
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| Country | Link |
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| CN (1) | CN217739796U (en) |
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- 2022-08-23 CN CN202222217963.XU patent/CN217739796U/en active Active
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