CN215379253U

CN215379253U - Safe heat supply circuit and electric blanket with same

Info

Publication number: CN215379253U
Application number: CN202121939696.6U
Authority: CN
Inventors: 周敏; 滕征朋
Original assignee: Wuhu Dongxifang Electronic Technology Co ltd
Current assignee: Wuhu Dongxifang Electronic Technology Co ltd
Priority date: 2021-08-18
Filing date: 2021-08-18
Publication date: 2021-12-31
Anticipated expiration: 2031-08-18

Abstract

The invention provides a safe heat supply circuit, comprising: a PTC electrical heating element that generates heat when energized; a first switching element coupled in a ground circuit of the PTC electrical heating element, configured to turn on or off a power circuit of the PTC electrical heating element based on a switching control signal; the first voltage acquisition circuit is used for sampling a first temperature voltage based on the grounding current of the PTC electric heating element; an NTC element disposed between the PTC electric heating element and the induction element; an induction element for receiving leakage current from the PTC electrothermal element conducted by the NTC element; a second voltage acquisition circuit for sampling a second temperature voltage based on the leakage current; and a controller configured to compare the first temperature voltage or the second temperature voltage with a set temperature voltage and output the switching control signal based on a comparison result. The safe heat supply circuit can accurately control the heating temperature, timely detect faults and cut off the power supply so as to ensure the safety of users.

Description

Safe heat supply circuit and electric blanket with same

Technical Field

The invention relates to an electric heating and heat preservation device, in particular to a safe heat supply circuit and an electric blanket with the circuit.

Background

The electric blanket is a common household appliance and is mainly used for increasing the temperature in a quilt when people sleep to achieve the purpose of warming. It has the advantages of low power consumption, adjustable temperature, convenient use and wide application, and has a history of more than 100 years.

However, if the electric blanket is not well maintained, the electric blanket may have electric leakage or fire, which threatens life of users. The similar situation usually occurs because the temperature of the heating wire is not accurately controlled, or key elements such as the heating wire, a switch element or a temperature sensing element are aged to cause short circuit or open circuit, so that the local temperature of the electric blanket is too high, and at the moment, if the fault cannot be timely detected and the power supply is cut off, a fire disaster is easily caused.

Therefore, the inventors of the present invention have endeavored to solve these problems based on their practical experience over many years.

Disclosure of Invention

The invention aims to solve the technical problem of providing a safe heat supply circuit in a PTC + NTC temperature control mode, and configuring a short circuit or open circuit detection protection circuit of key components, so that the heating temperature can be accurately controlled, faults can be timely detected, and a power supply can be cut off, thereby ensuring the life and property safety of a user.

In order to achieve the purpose, the invention adopts the following technical scheme:

one aspect of the present invention discloses a safe heat supply circuit, including:

a PTC electrical heating element that generates heat when energized;

a first switching element coupled in a ground circuit of the PTC electrical heating element, configured to turn on or off a power circuit of the PTC electrical heating element based on a switching control signal;

the first voltage acquisition circuit is used for sampling a first temperature voltage based on the grounding current of the PTC electric heating element;

an NTC element disposed between the PTC electric heating element and the induction element;

an induction element for receiving leakage current from the PTC electrothermal element conducted by the NTC element;

a second voltage acquisition circuit for sampling a second temperature voltage based on the leakage current;

and a controller configured to compare the first temperature voltage or the second temperature voltage with a set temperature voltage and output the switching control signal based on a comparison result.

In some embodiments, the first switching element is a thyristor, and the controller outputs a continuous trigger pulse as the switching control signal to control the thyristor to turn on.

In some embodiments, the first voltage acquisition circuit includes a first sampling resistor coupled between the first switching element and a power ground, and a first filter circuit coupled to the first sampling resistor, wherein a signal input terminal of the controller is coupled to the first filter circuit for receiving the sampled signal.

In some embodiments, the second voltage acquisition circuit includes a voltage divider circuit coupled to the current outflow end of the sensing element, and a second filter circuit coupled to the voltage divider circuit, and one signal input end of the controller is coupled to the second filter circuit to receive the sampling signal.

In some embodiments, the safety heating circuit of the present invention further comprises a step adjustment circuit coupled to one signal input of the controller for generating a step adjustment signal, the controller being further configured to adjust the set temperature voltage based on the step adjustment signal.

In some embodiments, the safety heating circuit of the present invention further comprises a display circuit, coupled to the at least one signal output of the controller, configured to display a currently set gear based on a display control signal output by the controller.

In some embodiments, the safety heating circuit of the present invention further comprises a third voltage collecting circuit coupled to the power terminal of the first switching element; the controller is further configured to detect a trip voltage collected by the third voltage collecting circuit when the first switching element is turned off, determine that the PTC electrothermal element and the first switching element are in a normal state if the trip voltage is at a high level, and determine that the PTC electrothermal element or the first switching element is malfunctioning if the trip voltage is at a low level.

In some embodiments, the controller is further configured to detect the first temperature voltage and compare the first temperature voltage with a first preset threshold when the open-circuit voltage is detected to be at a low level in an open state of the first switching element, determine that the PTC electrical heating element is faulty if the first temperature voltage is less than the first preset threshold, and determine that the first switching element is faulty if the first temperature voltage is greater than the first preset threshold.

In some embodiments, the third voltage collecting circuit includes a first comparator, a positive input terminal of the first comparator is coupled to a power supply terminal of the first switching element through a third filter circuit and a first current limiting circuit, a negative input terminal of the first comparator is configured to receive a reference voltage, and an output terminal of the first comparator is coupled to a signal input terminal of the controller.

In some embodiments, the safety heating circuit of the present invention further comprises a fuse protection circuit including a fuse coupled between the power terminal and the PTC electrothermal element, and a second switching element coupled between a current outflow end of the fuse and a power ground, and the controller is further configured to output a control signal to control the second switching element to be turned on to fuse the fuse when it is determined that the first switching element fails.

In some embodiments, the safety heating circuit of the present invention further comprises an inductive element detection circuit comprising a second current limiting circuit and a fourth voltage acquisition circuit; the current inflow end of the second current limiting circuit is coupled with a power supply terminal, and the current outflow end of the second current limiting circuit is coupled with the current inflow end of the induction element and the sampling end of the fourth voltage acquisition circuit; the fourth voltage acquisition circuit is used for sampling the load voltage of the current inflow end of the induction element, and the controller is further configured to receive the load voltage and compare the load voltage with a second preset threshold value, and when the load voltage is higher than the second preset threshold value, the first switch element is switched off.

In some embodiments, the fourth voltage collecting circuit includes a second comparator, a positive input terminal of the second comparator is coupled to the current outflow terminal of the second current limiting circuit through a fourth filter circuit and a third current limiting circuit, a negative input terminal of the second comparator is grounded, and an output terminal of the second comparator is coupled to a signal input terminal of the controller.

In some embodiments, the safety heating circuit of the present invention further comprises a power circuit coupled to an external power source to provide an ac voltage to the PTC electrical heating element and configured with a voltage conversion circuit configured to convert the ac voltage to a low voltage dc power source.

In some embodiments, the safety heating circuit of the present invention further comprises a power voltage detection circuit coupled between the power terminal of the PTC electrical heating element and a signal input terminal of the controller for detecting the power terminal voltage of the PTC electrical heating element, and the controller is further configured to adjust the set temperature voltage based on the power terminal voltage of the PTC electrical heating element detected by the power voltage detection circuit.

In some embodiments, the safety heating circuit of the present invention further comprises a zero-crossing detection circuit, coupled between the power supply terminal of the PTC electrical heating element and a signal input terminal of the controller, including at least one current-limiting resistor and a filter capacitor, and a clamping switch diode.

In another aspect of the present invention, there is also disclosed an electric blanket comprising:

a blanket;

and the safe heating circuit according to the first aspect, wherein the PTC electric heating element is an electric heating wire with PTC characteristics arranged in the blanket.

In some embodiments, the PTC electrical heating element, the NTC element and the sensing element are integrally disposed, wherein the PTC electrical heating element is a heating wire spirally wound on a core, the NTC element is an NTC material layer covering the heating wire, the sensing element is a sensing wire spirally wound on the NTC material layer, and a shielding layer and an insulating layer covering the sensing wire are disposed outside the sensing wire.

The safe heat supply circuit adopts a PTC + NTC temperature control mode, and can accurately control the heating temperature; meanwhile, a key component short circuit or open circuit detection protection circuit is further configured, so that a power supply can be cut off in time when the local temperature of the heating wire is overhigh or the key component is open circuit or short circuit, a fire phenomenon is prevented, and the life and property safety of a user is ensured.

Drawings

Fig. 1 is a schematic block diagram of an exemplary embodiment of a safety heating circuit of the present invention.

Fig. 2 is a schematic circuit diagram of an exemplary embodiment of the safety heating circuit of the present invention.

Fig. 3 is a schematic diagram of the pins of the controller in an exemplary embodiment of the safety heating circuit of the present invention.

Fig. 4 is a schematic diagram of a display circuit and a gear adjustment circuit in an exemplary embodiment of the safety heating circuit of the present invention.

Fig. 5 is a schematic block diagram of another exemplary embodiment of the safety heating circuit of the present invention.

Fig. 6 is a schematic circuit diagram of another exemplary embodiment of the safety heating circuit of the present invention.

Fig. 7 is a schematic circuit diagram of a power supply circuit in an exemplary embodiment of the safety heating circuit of the present invention.

Fig. 8 is a schematic block diagram of another exemplary embodiment of the safety heating circuit of the present invention.

Fig. 9 is a schematic circuit diagram of another exemplary embodiment of the safety heating circuit of the present invention.

Fig. 10 is a schematic view of an exemplary embodiment of an electric blanket equipped with a safety heating circuit of the present invention.

Fig. 11 is a schematic view illustrating an integrated arrangement structure of a PTC heater wire, an NTC layer and a temperature sensitive wire in an exemplary embodiment of an electric blanket equipped with a safety heating circuit according to the present invention.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention in conjunction with the examples, but it will be understood that the description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

"coupled" in the description and claims of the present invention includes direct connections, as well as indirect connections, such as connections through an electrically conductive medium, such as a conductor, where the electrically conductive medium may include parasitic inductance or parasitic capacitance. But also may include connections through other active or passive devices, such as through switches, follower circuits, etc., that serve the same or similar functional purpose.

Fig. 1 shows a schematic block diagram of a safety heating circuit according to an exemplary embodiment of the present invention. Referring to fig. 1, a safety heating circuit includes: a PTC electrical heating element 10 that generates heat when energized; a first switching element 11 coupled in a ground circuit of the PTC electrothermal element 10, configured to turn on or off a power circuit of the PTC electrothermal element 10 based on a switching control signal; a first voltage acquisition circuit 12 for sampling a first temperature voltage based on a ground current of the PTC electrical heating element 10; an NTC element 13 provided between the PTC heating element 10 and the induction element 14; an inductive element 14 for receiving leakage current from the PTC electrical heating element 10 conducted by the NTC element 13; a second voltage acquisition circuit 15 for sampling a second temperature voltage based on the leakage current; and a controller 16 configured to compare the first temperature voltage or the second temperature voltage with a set temperature voltage and output the switching control signal based on a comparison result.

Specifically, the PTC electrical heating element 10 is made of an electrical heating material having PTC characteristics, generates heat after being energized, and changes its resistance when the temperature changes (the higher the temperature, the larger the resistance). One end of the first switch element is coupled to the power circuit 20, and the other end is coupled to the power ground 17 via the first switch element 11. Accordingly, when the first switching element 11 is turned on or off, the PTC electric heating element 10 passes current and generates heat, and when the first switching element 11 is turned off or off, no current passes through the PTC electric heating element 10 and heat generation is stopped. The NTC element 13 is made of a material having NTC characteristics, which becomes less resistive when a temperature increases, thereby causing a leakage current flowing into the PTC electrothermal element in contact therewith to become large. The sensing element 14 is made of a conductive material, which is in contact with the NTC element 13, and receives a leakage current flowing through the PTC heating element.

Referring to fig. 2, in some embodiments, PTC electrical heating element 10 has a first terminal H1 coupled to a power supply circuit for receiving AC voltage, and a second terminal H4 coupled to ground via a first switching element (T1). The NTC element 13 is disposed between the PTC electrothermal element 10 and the inductive element 14, and the inductive element 14 is for receiving leakage current conducted by the NTC element 13 from the PTC electrothermal element 10.

Referring to fig. 2, in an exemplary embodiment, the first switching element is a thyristor T1 having a control signal input coupled to a signal output of the controller via a resistor R30 and a capacitor C18 for receiving the switch control signal S110. Optionally, the switch control signal S110 is a continuous trigger pulse, and the thyristor T1 is turned on when receiving the continuous trigger pulse output by the controller, and is turned off otherwise.

Referring to fig. 2, in one illustrative embodiment, the first voltage acquisition circuit includes sampling resistors R32, R33 coupled in parallel between the thyristor T1 and power ground, and a first filter circuit coupled to the sampling resistors R32, R33, the first filter circuit including a resistor R1 and a capacitor C1. A signal input terminal of the controller is coupled to the first filter circuit to receive the sampling signal S120.

Referring to fig. 2, in one illustrative embodiment, the second voltage acquisition circuit includes a voltage divider circuit coupled to the current outflow terminal H2 of the inductive element 14, and a second filter circuit coupled to the voltage divider circuit. The voltage dividing circuit consists of resistors R64 and R16, and the second filter circuit consists of a resistor R15 and a capacitor C6. A signal input terminal of the controller is coupled to the second filter circuit to receive the sampling signal S150. Further, in order to protect the controller, a clamping diode D3 is disposed on the second voltage acquisition circuit.

In some embodiments, the controller 16 may optionally be a CPU, MCU, or other programmable device. Referring to fig. 3, in one illustrative example, the controller employs a single chip Microcomputer (MCU)160 having a plurality of signal input/output pins (pins 1-16) through which signals can be received and through which signals can be output based on a configured program. In the illustrated example, pin 2(PC0) of the single chip Microcomputer (MCU)160 is used to output the switch control signal S110, and pin 10(PA6/AN5) and pin 11 (PA5/AN4) are used to receive the sampling signal S120 and the sampling signal S150, respectively. In subsequent embodiments, the signals received or output by the controller will be identified in the same manner.

Referring to fig. 1, in some embodiments, the safety heating circuit of the present invention further comprises a step adjustment circuit 18, the step adjustment circuit 18 being coupled to a signal input of the controller 16 for generating a step adjustment signal, the respective controller 16 being further configured to adjust the set temperature voltage based on the step adjustment signal.

Referring to FIG. 4, in one illustrative example, the range adjustment circuit 18 includes a switch SW1 and a ground resistor R13. By pressing switch SW1, a range adjustment signal S180 is generated so that controller 16 can adjust the set temperature voltage based on the range adjustment signal S180.

Referring to fig. 1, in some embodiments, the safety heating circuit of the present invention further includes a display circuit 19, the display circuit 19 being coupled to at least one signal output terminal of the controller 16 and configured to display a currently set gear based on a display control signal output by the controller.

Referring to fig. 4, in one illustrative example, the display circuit 19 includes light emitting diodes L1-L4, LEDs 5 that receive display control signals S190-S192 from the controller to display the currently set gear in different combinations.

The working principle of the safety heating circuit in this embodiment is further explained below with reference to the above illustrative embodiments:

when the operation is started, the controller 16 outputs a continuous trigger pulse to the first switching element (thyristor T1) to turn on, and the PTC electric heating element 10 is powered on and heats. The resistors R33 and R32 in the first voltage acquisition circuit form a sampling resistor, and a sampling voltage signal forms a sampling signal S120 after being subjected to current limiting filtering through a first filter circuit formed by resistors R1 and C1 and enters the controller. When the temperature rises, the resistance of the PTC electrical heating element 10 becomes large, thereby causing the sampling voltage of the first voltage acquisition circuit to decrease. When the controller detects that the sampling voltage is lower than the set temperature voltage corresponding to the current configuration gear, the controller stops outputting the trigger pulse to the first switch element (the thyristor T1), and further disconnects the first switch element (the thyristor T1) to stop heating. Then, along with the temperature reduction, the resistance value of the PTC electric heating element 10 is gradually reduced; when the resistance value becomes smaller, the sampling voltage acquired by the first voltage acquisition circuit rises. When the controller detects that the sampling voltage is higher than the set temperature voltage corresponding to the current configuration gear, a continuous trigger pulse is output to the first switching element (the thyristor T1) to be conducted, so that the power supply loop of the PTC electric heating element 10 is switched on, and heating is resumed. In the heating process, the two processes are alternately carried out, and the purpose of constant temperature is achieved through cyclic control.

On the other hand, when the PTC electrothermal device 10 is powered on and heated, the ac voltage flowing through it forms a leakage current through the NTC device 13 and enters the sensing device 14, and then is sampled by the voltage divider circuit (resistors R64, R16) in the second voltage acquisition circuit and filtered by the second filter circuit (resistor R15, capacitor C6) to form a sampling signal S150, which enters the controller, so as to acquire the NTC temperature voltage. When the NTC temperature voltage is lower than the set temperature voltage corresponding to the currently configured shift, the controller outputs a continuous trigger pulse to the first switching element (thyristor T1) to turn on, and the PTC electric heating element 10 is kept powered on and heated. When the overall temperature or the local temperature sensed by the NTC element exceeds the NTC protection setting value, the leakage current entering the sensing element 14 through the NTC element 13 becomes large, which further causes the voltage signal (NTC temperature voltage) collected by the second voltage to rise, and when the controller detects that the NTC temperature voltage is higher than the set temperature voltage corresponding to the currently configured gear, the controller stops outputting the trigger pulse to the first switching element (the thyristor T1) to disconnect the trigger pulse, and further disconnects the power supply loop of the PTC electrothermal element 10 to stop heating.

Based on the principle, the safe heat supply circuit in the embodiment can realize accurate control of heating temperature, and meanwhile, safety accidents caused by local overheating of the heating wire can be avoided.

Fig. 5 shows a schematic block diagram of a safety heating circuit according to another exemplary embodiment of the present invention. Referring to fig. 5, a safety heating circuit includes: a PTC electrical heating element 10 that generates heat when energized; a first switching element 11 coupled in a ground circuit of the PTC electrothermal element 10, configured to turn on or off a power circuit of the PTC electrothermal element 10 based on a switching control signal; a first voltage acquisition circuit 12 for sampling a first temperature voltage based on a ground current of the PTC electrical heating element 10; an NTC element 13 provided between the PTC heating element 10 and the induction element 14; an inductive element 14 for receiving leakage current from the PTC electrical heating element 10 conducted by the NTC element 13; a second voltage acquisition circuit 15 for sampling a second temperature voltage based on the leakage current; a controller 16 configured to compare the first temperature voltage or the second temperature voltage with a set temperature voltage and output the switching control signal based on a comparison result. And a third voltage acquisition circuit 21 coupled to a power source terminal of the first switching element 11; accordingly, the controller 16 is further configured to detect the open circuit voltage collected by the third voltage collecting circuit 21 when the first switching element 11 is turned off, and determine that the PTC electrothermal element 10 and the first switching element 11 are in a normal state if the open circuit voltage is at a high level, and determine that the PTC electrothermal element 10 or the first switching element 11 is out of order if the open circuit voltage is at a low level.

As a further improvement, in the present exemplary embodiment, the controller 16 is further configured to further detect a first temperature voltage sampled by the first voltage acquisition circuit 15 and compare the first temperature voltage with a first preset threshold when the above-mentioned trip voltage is detected to be a low level in the off state of the first switching element 11, determine that the PTC electrical heating element 10 is failed (tripped) if the first temperature voltage is less than the first preset threshold, and determine that the first switching element 11 is failed (shorted) if the first temperature voltage is greater than the first preset threshold.

Referring to fig. 6, in an exemplary embodiment, the third voltage acquisition circuit includes a first comparator U3B, a forward input terminal of the first comparator U3B is coupled to a power supply terminal of a first switching element (thyristor T1) via a third filter circuit composed of a resistor R40, a capacitor C3 and a diode D8, and a first current limiting circuit composed of resistors R27 and R28, a reverse input terminal of the first comparator is coupled to a voltage dividing circuit composed of resistors R4 and R7 for receiving a reference voltage, and an output terminal of the first comparator is coupled to a signal input terminal of the controller for outputting the trip voltage signal S210. The illustrated examples of the first voltage collecting circuit and the second voltage collecting circuit are similar to those in the foregoing embodiments, and are not specifically described here.

when the first switching element 11 is turned off, the controller 16 detects the open-circuit voltage collected by the third voltage collecting circuit 21 (i.e. the open-circuit voltage signal S210 output by the output terminal of the first comparator U3B), and if the open-circuit voltage is at a high level, it indicates that the first switching element 11 is normally turned off, thereby determining that the states of the PTC electrothermal element 10 and the first switching element 11 are normal. If the trip voltage is low, it may be determined that the PTC electrical heating element 10 or the first switching element 11 has failed because the PTC electrical heating element 10 has tripped or the first switching element 11 has failed and cannot be normally turned off.

At this time, the controller 16 further detects the first temperature voltage sampled by the first voltage acquisition circuit 12 and compares the first temperature voltage with a first preset threshold, and if the first temperature voltage is smaller than the first preset threshold, it indicates that the PTC electric heating element 10 is open-circuited, resulting in a low level at the ground terminal H4, thereby determining that the PTC electric heating element 10 is in a fault (open circuit); if the first temperature voltage is greater than the first preset threshold, it indicates that the first switching element 11 fails to be normally turned off, and usually the first switching element 11 fails to be short-circuited, so that a voltage is generated at a ground terminal thereof, thereby determining that the first switching element 11 fails (is short-circuited). The first preset threshold value can be set according to actual conditions.

Referring to fig. 1 and 5, in some embodiments, the safety heating circuit of the present invention further includes a power circuit 20 coupled to an external power source to supply an ac voltage to the PTC heating elements 10, and configured with a voltage conversion circuit configured to convert the ac voltage into a 5V low voltage dc power.

Referring to fig. 7, in an exemplary embodiment, the power circuit includes a live terminal L and a neutral terminal N for coupling to an external power source, and a fuse F1 connected in series behind the live terminal L, and a protection circuit including a varistor (surge receiver) ZNR1, a filter capacitor CX1, and resistors RX1 and RX1 is provided behind the fuse F1, and then the PTC electrothermal element 10 is coupled to supply power thereto. Meanwhile, a voltage conversion circuit is coupled, and comprises a current-limiting resistor R38, a capacitor C16, a voltage-stabilizing diode ZD1, a diode D2, and filter capacitors C17 and C7, and then a stable 5V low-voltage direct-current power supply is generated after the voltage-stabilizing chip U2 and the filter capacitors C26 and C25 filter the voltage-stabilizing chip U2.

Referring to fig. 7, in one illustrative embodiment, the power circuit further includes a fuse protection circuit including a second switching element SCR1 coupled between the current outflow terminal of the fuse F1 and a power ground.

Accordingly, in some embodiments, the controller 16 is further configured to output the control signal S220 to control the second switching element SCR1 to be turned on when it is determined that the first switching element 11 is faulty, and at this time, the ac power introduced by the live terminal L is grounded through the second switching element SCR1, so as to fuse the fuse F1 to cut off the power supply, thereby achieving a protection effect.

Referring to fig. 1, in some embodiments, the safety heating circuit of the present invention further includes a power supply voltage detection circuit 25. Referring to fig. 7, in an exemplary embodiment, the power voltage detection circuit is coupled between the power terminal of the PTC electrical heating element 10 and a signal input terminal of the controller, and includes a resistor R36 coupled to the power terminal (current flowing terminal of the fuse F1) of the PTC electrical heating element 10, and a resistor R19, a diode D1 and a capacitor C4 coupled in parallel to the resistor R36 and grounded. The power supply voltage detection circuit is used for sampling and generating a power supply voltage detection signal S250, so that the controller can detect the power supply end voltage of the PTC electric heating element by receiving the power supply voltage detection signal S250, and further adjust the set temperature voltage to avoid the influence on the heating temperature control due to the fluctuation of the power supply voltage.

Referring to fig. 1, in some embodiments, the safety heating circuit of the present invention further comprises a zero-crossing detection circuit 24. Referring to fig. 7, in one illustrative embodiment, the zero crossing detection circuit is coupled between the power supply terminal of the PTC thermistor 10 and a signal input terminal of the controller 16, and includes two current limiting resistors R39, R22, and a filter capacitor C9, and a clamp switching diode D6. The zero-crossing detection circuit outputs the sampling signal S240 to a signal input terminal of the controller 16, so that the controller 16 can detect the zero-crossing abnormality of the power supply based on the sampling signal S240.

Fig. 8 shows a schematic block diagram of a safety heating circuit according to another exemplary embodiment of the present invention. Referring to fig. 8, a safety heating circuit includes: a PTC electrical heating element 10 that generates heat when energized; a first switching element 11 coupled in a ground circuit of the PTC electrothermal element 10, configured to turn on or off a power circuit of the PTC electrothermal element 10 based on a switching control signal; a first voltage acquisition circuit 12 for sampling a first temperature voltage based on a ground current of the PTC electrical heating element 10; an NTC element 13 provided between the PTC heating element 10 and the induction element 14; an inductive element 14 for receiving leakage current from the PTC electrical heating element 10 conducted by the NTC element 13; a second voltage acquisition circuit 15 for sampling a second temperature voltage based on the leakage current; a controller 16 configured to compare the first temperature voltage or the second temperature voltage with a set temperature voltage and output the switching control signal based on a comparison result. And an inductive element detection circuit including a second current limiting circuit 22 and a fourth voltage acquisition circuit 23. The current inflow end of the second current limiting circuit 22 is coupled to the power supply terminal, and the current outflow end is coupled to the current inflow end of the sensing element 14 and the sampling end of the fourth voltage collecting circuit 22; the fourth voltage acquisition circuit 22 is used for sampling the load voltage at the current inflow end of the inductive element 14. Accordingly, the controller 16 is further configured to receive the load voltage sampling signal and compare the load voltage sampling signal with a second preset threshold, and to turn off the first switching element 11 when the load voltage is higher than the second preset threshold.

Referring to fig. 9, in one illustrative embodiment, the second current limiting circuit 22 includes series-connected current limiting resistors R21 and R29 having one end coupled to the power supply terminal and the other end coupled as a current outflow end to the current inflow end of the inductive element 14.

Referring to fig. 9, in an exemplary embodiment, the fourth voltage collecting circuit includes a second comparator U3A, a forward input terminal of the second comparator U3A is coupled to a current flowing terminal of the second current limiting circuit through a fourth filter circuit composed of a capacitor C2, a resistor R23 and a diode D9, and a third current limiting circuit composed of resistors R37 and R66, a reverse input terminal of the second comparator U3 is coupled to ground through a resistor R3 and is coupled to an output terminal of the second comparator U2, and the output terminal of the second comparator U3 is coupled to a signal input terminal of the controller for outputting the load voltage signal S230. In addition, a clamping diode D4 is coupled to the fourth voltage acquisition circuit for protecting the comparator and the controller chip.

In the present illustrative embodiment, the illustrated examples of the first voltage acquisition circuit and the second voltage acquisition circuit are similar to those in the foregoing embodiments, and are not specifically described here.

when the sensing element 14 works normally, the current led from the second current limiting circuit is divided into two paths, one path flows into the sensing element 14 through the current inflow end H3 of the sensing element 14 and flows out of the current outflow end H2, and then enters a second voltage acquisition circuit consisting of resistors R64, R16, R15 and a capacitor C6; and the other path enters the fourth voltage acquisition circuit. At this time, the load voltage signal S230 sampled by the fourth voltage acquisition circuit received by the controller is a more stable voltage value. When the sensing element 14 is disconnected due to a fault, the voltage at the current inflow terminal H3 will become high, and the load voltage sampled by the fourth voltage acquisition circuit changes accordingly, and when the controller detects the change, it can be determined that the sensing element 14 has a fault (open circuit), so as to disconnect the first switching element (thyristor T1), and send an alarm signal through the display circuit.

Fig. 10 shows another exemplary embodiment of the present invention, which is an electric blanket configured with the safety heating circuit in one or more embodiments described above. The electric blanket comprises:

blanket 1; and a safety heating circuit as shown in one or more of the embodiments described above. The PTC electric heating elements in the safety heating circuit are PTC heating wires arranged in blanket 1, and the NTC elements and the sensing elements are arranged in parallel with the PTC heating wires and coupled to control box 3 through wires 4. The controller, the first switch element, the gear adjusting circuit, the display circuit and the like are arranged in the control box 3, and the power circuit is also integrated in the control box 3 and takes electricity through the plug 5.

Referring to fig. 11, in an exemplary embodiment, the PTC heating wire, the NTC element and the sensing element are integrally provided. The PTC heating wire 100 is spirally wound on the core 101, the NTC element is an NTC material layer with NTC characteristics and coated on the PTC heating wire 100, and the sensing element is a conductive wire 103 spirally wound on the NTC material layer. Outside the conductive line 103, a shield layer 104 is further coated, and an insulating layer 105 is provided on the outermost layer. Optionally, the core 101 is made of PET, and the shielding layer 104 is made of tin-copper alloy. The materials of the PTC heating wire, the NTC element and the induction element can be selected according to actual requirements.

It should be noted that, in some embodiments, the electric blanket of the present invention may be configured with a certain safety heat supply circuit shown in the foregoing embodiments, or may be configured with several safety heat supply circuits shown in the foregoing embodiments in combination, so as to achieve better temperature control and protection purposes, and achieve better safety. Since several implementations of the safety heating circuit and its operation principle have been described in detail in the foregoing embodiments, they will not be described again.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims

1. A safety heating circuit, comprising:

a PTC electrical heating element that generates heat when energized;

2. A safety heating circuit according to claim 1, wherein the first switching element is a thyristor and the controller outputs a continuous trigger pulse as the switching control signal to control the thyristor to turn on.

3. A safety heating circuit as claimed in claim 1, wherein the first voltage acquisition circuit comprises a first sampling resistor coupled between the first switching element and the power ground, and a first filter circuit coupled to the first sampling resistor, and a signal input terminal of the controller is coupled to the first filter circuit for receiving the sampling signal.

4. A safety heating circuit as claimed in claim 1, wherein the second voltage acquisition circuit comprises a voltage divider circuit coupled to the current outlet of the sensing element, and a second filter circuit coupled to the voltage divider circuit, wherein a signal input terminal of the controller is coupled to the second filter circuit to receive the sampled signal.

5. A safety heating circuit as claimed in claim 1, further comprising a step adjustment circuit coupled to one signal input of the controller for generating a step adjustment signal, the controller being further configured to adjust the set temperature voltage based on the step adjustment signal.

6. A safety heating circuit as claimed in claim 5, further comprising a display circuit coupled to at least one signal output of the controller and configured to display a currently set gear based on a display control signal output by the controller.

7. A safety heating circuit according to any one of claims 1 to 6, further comprising a third voltage acquisition circuit coupled to a power terminal of the first switching element; the controller is further configured to detect a trip voltage collected by the third voltage collecting circuit when the first switching element is turned off, determine that the PTC electrothermal element and the first switching element are in a normal state if the trip voltage is at a high level, and determine that the PTC electrothermal element or the first switching element is malfunctioning if the trip voltage is at a low level.

8. A safety heating circuit according to claim 7, wherein the controller is further configured to detect the first temperature voltage and compare it with a first preset threshold when the open-circuit voltage is detected to be low in an open state of the first switching element, determine that the PTC electrical heating element is faulty if the first temperature voltage is less than the first preset threshold, and determine that the first switching element is faulty if the first temperature voltage is greater than the first preset threshold.

9. A safety heating circuit according to claim 7, wherein the third voltage collecting circuit comprises a first comparator, a positive input terminal of the first comparator is coupled to a power terminal of the first switching element via a third filter circuit and the first current limiting circuit, a negative input terminal of the first comparator is configured to receive the reference voltage, and an output terminal of the first comparator is coupled to a signal input terminal of the controller.

10. A safety heating circuit according to claim 8, further comprising a fuse protection circuit including a fuse coupled between the power terminal and the PTC electrothermal element, and a second switching element coupled between a current outflow end of the fuse and a power ground, wherein the controller is further configured to output a control signal to control the second switching element to be turned on to fuse the fuse when it is determined that the first switching element has failed.

11. A safety heating circuit according to any one of claims 1 to 6, further comprising an inductive element detection circuit comprising a second current limiting circuit and a fourth voltage harvesting circuit; the current inflow end of the second current limiting circuit is coupled with a power supply terminal, and the current outflow end of the second current limiting circuit is coupled with the current inflow end of the induction element and the sampling end of the fourth voltage acquisition circuit; the fourth voltage acquisition circuit is used for sampling the load voltage of the current inflow end of the induction element, and the controller is further configured to receive the load voltage and compare the load voltage with a second preset threshold value, and when the load voltage is higher than the second preset threshold value, the first switch element is switched off.

12. A safety heating circuit as claimed in claim 11, wherein the fourth voltage collecting circuit comprises a second comparator, a forward input terminal of the second comparator is coupled to the current outflow terminal of the second current limiting circuit via a fourth filter circuit and a third current limiting circuit, a reverse input terminal of the second comparator is grounded, and an output terminal of the second comparator is coupled to a signal input terminal of the controller.

13. A safety heating circuit according to any one of claims 1 to 6, further comprising a power supply circuit coupled to an external power supply to provide an AC voltage to the PTC electrical heating element and provided with a voltage conversion circuit configured to convert the AC voltage to a low voltage DC power supply.

14. A safety heating circuit as claimed in claim 13, further comprising a power voltage detection circuit coupled between the power terminal of the PTC electrical heating element and a signal input terminal of the controller for detecting a power terminal voltage of the PTC electrical heating element, the controller being further configured to adjust the set temperature voltage based on the power terminal voltage of the PTC electrical heating element detected by the power voltage detection circuit.

15. A safety heating circuit as claimed in claim 13, further comprising a zero-crossing detection circuit coupled between the power supply terminal of the PTC electrical heating element and a signal input terminal of the controller, including at least one current-limiting resistor and filter capacitor, and a clamping switching diode.

16. An electric blanket, comprising:

a blanket;

and a safety heating circuit according to any one of claims 1 to 15, wherein the PTC electrical heating element is a heating wire having PTC characteristics arranged in the blanket.

17. The electric blanket of claim 16, wherein the PTC electric heating element, the NTC element and the sensing element are integrally formed, wherein the PTC electric heating element is a heating wire spirally wound on a core, the NTC element is an NTC material layer covering the heating wire, the sensing element is a sensing wire spirally wound on the NTC material layer, and a shielding layer and an insulating layer covering the sensing wire are provided at the outside.