CN210270579U

CN210270579U - Novel heating wire protection circuit

Info

Publication number: CN210270579U
Application number: CN201921514457.9U
Authority: CN
Inventors: 吴进坤; 唐波; 董晓勇; 向杨; 皮峰; 冉亚林; 毛巧运
Original assignee: Shenzhen Yingtechuang Intelligent Technology Co ltd
Current assignee: Shenzhen Yingtechuang Intelligent Technology Co ltd
Priority date: 2019-09-11
Filing date: 2019-09-11
Publication date: 2020-04-07
Anticipated expiration: 2029-09-11

Abstract

The utility model discloses a novel heating wire protection circuit, which comprises a heating wire, a first relay, a second relay, a voltage detection circuit, an MCU and a Darlington phase inverter, wherein the first relay is used for controlling the on-off between the first end of the heating wire and an alternating current live wire; the second relay is used for controlling the on-off between the second end of the heating wire and the alternating current zero line; the voltage detection circuit is used for detecting the voltage of the second end of the heating wire and outputting a voltage signal; the MCU receives the voltage signal and respectively outputs a first control signal and a second control signal; the Darlington phase inverter receives the first control signal and controls the first relay to be opened and closed according to the first control signal, and the Darlington phase inverter receives the second control signal and controls the second relay to be opened and closed according to the second control signal.

Description

Novel heating wire protection circuit

Technical Field

The utility model relates to an electrical heating technical field especially relates to a novel heater strip protection circuit.

Background

Along with economic development, household appliances increasingly fuse leading-edge science and technology to provide convenience for clothes and eating houses, and the electric heating technology is widely applied in various innovative ways, wherein the way of heating by adopting the resistance-type heating wire is more spread at all corners in the field of household appliances.

The mode rate of heating of resistance-type heater strip heating is fast, and the temperature is high, and electric heat conversion efficiency is high, but rate of heating is fast, and the temperature is high, and when electric heat conversion efficiency is high, often also decided that the electric current that passes through that this scheme itself needs is big, and the temperature that bears is high, and this brings the hidden danger with regard to the stability for the system. The heating wire drive scheme that adopts in the present household electrical appliances field generally adopts single relay control, and considers cost and does not adopt effectual protection circuit by general designer, consequently, the defect in following several aspects exists in current heating wire drive scheme:

1. when the power of the heating wire is larger, the current is large, the heating is serious, sometimes the armature of the relay is heated seriously, when the system needs to be disconnected quickly, a certain time delay exists, even the relay cannot be disconnected effectively, and the system is unsafe.

2. The current heating wire driving mode adopts open-loop control, namely the MCU can not judge whether the heater is really disconnected or not, if the relay is damaged and is always conducted, an accident can be caused, on the other hand, the MCU can not judge whether the heating wire is conducted or not, and the system can still normally control the driving even though the heating wire is disconnected.

3. Because of the inherent design of the heating wires, the shell is connected with the ground, the creepage clearance is not large, and high-standard anti-surge capacity is required in countries in Europe and America, so that many heating wires cannot pass the 4KV surge test.

Disclosure of Invention

The utility model aims to solve the technical problem that a novel heater strip protection circuit is provided can realize closed-loop control and failure protection, still has very high anti-surge ability simultaneously.

In order to solve the technical problem, the utility model discloses a as follows technical scheme:

a novel heating wire protection circuit comprises a heating wire, a first relay, a second relay, a voltage detection circuit, an MCU and a Darlington phase inverter, wherein the first relay is used for controlling the on-off between a first end of the heating wire and an alternating current live wire; the second relay is used for controlling the on-off between the second end of the heating wire and the alternating current zero line; the voltage detection circuit is used for detecting the voltage of the second end of the heating wire and outputting a voltage signal; the MCU receives the voltage signal and respectively outputs a first control signal and a second control signal; the Darlington phase inverter receives the first control signal and controls the first relay to be opened and closed according to the first control signal, and the Darlington phase inverter receives the second control signal and controls the second relay to be opened and closed according to the second control signal.

The utility model has the advantages of: above-mentioned neotype heater strip protection circuit adopts two relays to carry out serial control to the heater strip, carries out the feedback detection through the one end of voltage detection circuit heater strip simultaneously, MCU judges whether the heater strip normally works on line according to the testing result, judges whether the relay short circuit became invalid and judges whether the drive breaks down etc. has realized relay and driven closed loop monitoring, can carry out real-time closed loop control and failure protection, prevent the heating control inefficacy emergence accident, the stability of system has been improved greatly. In addition, this circuit adopts two relay control, and when the heater strip need not the during operation, the heater strip simultaneously with live wire and zero line disconnection for the heater strip body is uncharged, has high anti-electric level when encountering with the surge like this, can improve the ann rule security performance under the thunderbolt greatly, has very high anti-surge ability.

Drawings

Fig. 1 is a schematic circuit diagram of the novel heating wire protection circuit of the present invention.

Detailed Description

To make the objects, technical solutions and advantages of the present invention more clearly understood by those skilled in the art, the present invention will be further described with reference to the accompanying drawings and examples.

As shown in fig. 1, in an embodiment of the present invention, the novel heater protection circuit includes a heater R1, a first relay RL1, a second relay RL2, a voltage detection circuit 10, an MCU U2 and a darlington inverter U1, wherein the first relay RL1 is used to control the connection/disconnection between the first end of the heater R1 and an ac live wire (ACL); the second relay RL2 is used for controlling the on-off between the second end of the heating wire R1 and an alternating current neutral conductor (ACN); the voltage detection circuit 10 is used for detecting the voltage at the second end (point B) of the heating wire R1 and outputting a voltage signal; the MCUU2 receives the voltage signal and outputs a first control signal and a second control signal respectively; the darlington inverter U1 receives the first control signal and controls the opening and closing of the first relay RL1 according to the first control signal, and the darlington inverter U1 receives the second control signal and controls the opening and closing of the second relay RL2 according to the second control signal.

The MCU U2 adopts a single chip microcomputer with the model number of SN8F570212S SOP16, the Darlington inverter U1 adopts a Darlington IC with the model number of ULN2001DS, a first input end (a No. 2 pin) of the Darlington inverter U1 is connected with a No. 2 pin of the MCU U2, a first output end Heat-L (a No. 7 pin) of the Darlington inverter U1 is connected with a first end of an inductance coil of the first relay RL1, and a second end of the inductance coil of the first relay RL1 is connected with a +12V direct-current power supply; a second input end (a 1 st pin) of the darlington inverter U1 is connected with a 3 rd pin of the MCU U2, a second output end Heat-R (an 8 th pin) of the darlington inverter U1 is connected with a first end of an inductor of the second relay RL2, and a second end of the inductor of the second relay RL2 is connected with a +12V dc power supply. The No. 2 pin and the No. 3 pin of the MCU U2 are control pins of the MCU respectively, a first control signal and a second control signal are output respectively to correspondingly control the on-off of the first relay RL1 and the second relay RL2, and when the first relay RL1 and the second relay RL2 are closed effectively at the same time, the heating wire R1 is electrified normally to work.

The novel heating wire protection circuit further comprises a diode D1 and a diode D2, the anode of the diode D1 is connected with the first end of an inductance coil of the first relay RL1, the anode of the diode D2 is connected with the first end of an inductance coil of the second relay RL2, and the cathodes of the diode D1 and the diode D2 are both connected with a direct-current power supply. A diode connected with the relay in an inverse parallel mode is added in the circuit, the diode and an inductance coil of the relay form a loop, and high electromotive force generated by the inductance coil of the relay is consumed in the loop in a continuous current mode, so that elements in the circuit are protected from being damaged.

The voltage detection circuit 10 comprises a resistor R2, a capacitor C2 and a transistor Q2, wherein a first end of the resistor R2 is connected to a second end of the heater R2, a second end of the resistor R2 is respectively connected to a first end of the resistor R2 and a first end of the resistor R2, a second end of the resistor R2 is respectively connected to a second end of the resistor R2, a first end of the capacitor C2 and a base of the transistor Q2, a second end of the resistor R2, a second end of the capacitor C2 and an emitter of the transistor Q2 are all grounded, a collector of the transistor FB 2 is connected to a collector of the transistor Q2 through a resistor R2-Q2, and a collector of a resistor R2 (a post-transistor R2) connected to a post-, the capacitor C2 is connected between the collector and emitter of the transistor Q1.

The novel heating wire protection circuit working process of the embodiment is as follows:

when the heating wire needs to be opened, the MCU U2 firstly outputs a high level from the 2 nd pin according to the instruction of a built-in program, the high level is subjected to phase inversion processing by the Darlington inverter U1 and then outputs a low level from the first output terminal Heat-L (the 7 th pin) of the Darlington inverter U1, the first relay RL1 is electrified and closed, the current on the ACL flows into the heating wire R1 through the first relay RL1, alternating current passes through the second end (the B point) of the heating wire R1, the resistor R2, the resistor R3, the resistor R4, the resistor R5, the resistor R6 and the resistor R7 form a voltage division circuit, the resistor R7 divides the voltage and filters the voltage through the capacitor C1, when the resistor R7 exceeds the upper limit of the gate voltage of the triode Q1, the triode Q1 is switched on, the MCU detects the low level at the Haet-FB (the 15 th pin) of the detection pin, because the B point is the sine alternating current voltage, the rule of the Haet-FB-, the first relay RL1 is indicated to be normally controlled, and the heating wire R1 is on line. And then, the pin 3 of the MCU U2 enables to output a high level, the high level is subjected to phase inversion processing by the darlington inverter U1, and then a low level is output from the second output terminal Heat-R (pin 8) of the darlington inverter U1, so that the second relay RL2 is powered on and closed, the second end (point B) of the heating wire R2 is communicated with the ACN to form a loop, because the novel heating wire protection circuit of the present embodiment is a non-isolated circuit, and GND floats on the ACN and belongs to the same network, the transistor Q1 cannot be turned on, and the MCUU2 detects a constant high level in the Haet-FB.

When the heating wires need to be disconnected, the MCU U2 firstly outputs a low level to the Darlington inverter U1 according to a built-in program instruction of the MCU U2 in a 3 rd pin enabling mode to disconnect the second relay RL2, and if the second relay RL2 is normally disconnected, the MCU detects a regular square wave in Haet-FB; if the Haet-FB still keeps constant high level, the control failure of the second relay RL2 is proved, the system needs to enter protection, the MCU U2 starts the failure protection of the circuit through software reset or other triggering modes, and meanwhile, the failure protection is communicated to other modules through SCL and SDA, and the failure of the heating wire circuit is indicated. When the square wave is detected, the MCU U2 firstly outputs a low level to the Darlington inverter U1 according to a built-in program instruction of the MCU U2 in a 2 nd pin enabling mode to disconnect the first relay RL1, if the first relay RL1 is normally disconnected, the heating wire R1 is completely in an open circuit state, the MCU detects a constant high level in Haet-FB, and the constant high level indicates that the first relay RL1 is normally disconnected; if the Haet-FB still keeps, the fact that the control of the first relay RL1 is failed is proved, the system needs to enter protection, the MCU U2 starts the failure protection of the circuit through software reset or other triggering modes, and meanwhile, the failure protection is communicated to other modules through the SCL and the SDA to indicate that the circuit of the heating wire is failed.

The neotype heater strip protection circuit of this embodiment adopts two relays to carry out serial control to the heater strip, simultaneously carry out the feedback detection in the one end of heater strip through voltage detection circuit, MCU judges whether the heater strip normally works on line according to the waveform of triggering, judge whether the relay short circuit became invalid and judge whether the drive breaks down and so on, realized relay and driven closed-loop monitoring, can carry out real-time closed-loop control and failure protection, prevent that heating control from becoming invalid and the emergence accident, the stability of system has been improved greatly. In addition, this circuit adopts two relay control, and when the heater strip need not the during operation, the heater strip is simultaneously with ACL and ACN disconnection for the heater strip body is uncharged, has high anti-electric level when encountering with the surge like this, can improve the ann rule security performance under the thunderbolt greatly, has very high anti-surge ability. The novel heating wire protection circuit of the embodiment has the advantages of simple peripheral control, low cost, and strong applicability and economic value.

The foregoing is considered as illustrative of the preferred embodiments of the invention and is not intended to limit the invention in any way. Various equivalent changes and modifications can be made on the basis of the above embodiments by those skilled in the art, and all equivalent changes and modifications within the scope of the claims should fall within the protection scope of the present invention.

Claims

1. The utility model provides a novel heater strip protection circuit which characterized in that, novel heater strip protection circuit including:

a heating wire;

the first relay is used for controlling the on-off between the first end of the heating wire and the alternating current live wire;

the second relay is used for controlling the on-off between the second end of the heating wire and the alternating current zero line;

the voltage detection circuit is used for detecting the voltage of the second end of the heating wire and outputting a voltage signal;

the MCU receives the voltage signal and respectively outputs a first control signal and a second control signal;

and the Darlington phase inverter receives the first control signal and controls the opening and closing of the first relay according to the first control signal, and the Darlington phase inverter receives the second control signal and controls the opening and closing of the second relay according to the second control signal.

2. The novel heating wire protection circuit as claimed in claim 1, wherein the darlington inverter is a darlington IC with model number ULN2001DS, a first input end and a second input end of the darlington inverter are connected with the MCU, a first output end of the darlington inverter is connected with a first end of an inductance coil of the first relay, and a second end of the inductance coil of the first relay is connected with a direct current power supply; and a second output end of the Darlington phase inverter is connected with a first end of an inductance coil of the second relay, and a second end of the inductance coil of the second relay is connected with the direct-current power supply.

3. The novel heating wire protection circuit as claimed in claim 2, wherein the heating wire protection circuit further comprises a diode D1 and a diode D2, wherein an anode of the diode D1 is connected to the first end of the inductance coil of the first relay, an anode of the diode D2 is connected to the first end of the inductance coil of the second relay, and cathodes of the diode D1 and the diode D2 are connected to a dc power supply.

4. The novel heating wire protection circuit as claimed in claim 1, wherein the voltage detection circuit comprises a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C1, a capacitor C2 and a transistor Q1, a first end of the resistor R2 is connected to a second end of the heating wire, a second end of the resistor R2 is respectively connected to a first end of the resistor R2 and a first end of the resistor R2, a second end of the resistor R2 is respectively connected to a second end of the resistor R2, a first end of the capacitor C2 and a base of the transistor Q2, a second end of the resistor R2, a second end of the capacitor C2 and a second end of the transistor Q2 are respectively connected to a collector of the transistor Q2 through a direct current source, the collector of the triode Q1 is connected with the MCU through a resistor R8, and the capacitor C2 is connected between the collector and the emitter of the triode Q1.

5. A novel heating wire protection circuit as claimed in any one of claims 1 to 4, wherein the MCU is a single chip microcomputer of model SN8F570212S SOP 16.