Control circuit of heating pad

Abstract

The utility model relates to a control circuit of a heating pad, which comprises a master control MCU, the output end of the master control MCU is respectively connected with an LED driving module and a heating wire driving module, the heating wire driving module comprises a silicon controlled rectifier and a heating wire, and the input end of the master control MCU is respectively connected with a linear voltage reduction and stabilization module and a zero cross detection module. The output end of the linear voltage reduction and stabilization module is also electrically connected with the LED driving module; the zero-cross detection module comprises a voltage comparator, the inverted input end of the voltage comparator inputs power grid voltage, the positive input end of the voltage comparator is connected with the positive terminal of the low-voltage power supply, and the zero-cross detection module detects a zero-point phase signal and then feeds back the zero-point phase signal to the master control MCU. And after receiving the zero phase feedback signal, the main control MCU outputs a pulse to control the conduction of a silicon controlled rectifier of the heating wire driving module. According to the utility model, the main control MCU outputs a pulse to control the conduction of the silicon controlled rectifier according to the zero phase signal, thereby preventing unstable power caused by phase drift and avoiding impact on a power grid.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, in particular to a control circuit of a heating pad. Background Art

[0002] In the heating pad control circuit powered by the power grid, the heating wire is controlled by controlling the conduction or closing of the thyristor, and the single-chip microcomputer outputs a pulse signal to control the conduction of the thyristor. In the prior art, the single-chip microcomputer mainly uses a fixed frequency of 50HZ to give pulses. Once phase drift occurs, it is easy to cause power instability. The conduction of the thyristor at the peak of the sine wave will cause an impact on the power grid. Utility Model Content

[0003] The utility model discloses a control circuit of a heating pad. A zero-crossing detection module is provided to detect a phase. A single chip microcomputer outputs a pulse according to the detected phase signal, thereby effectively preventing a phase drift.

[0004] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0005] A control circuit for a heating pad comprises a main control MCU, wherein the output end of the main control MCU is respectively connected to an LED driving module and a heating wire driving module, wherein the heating wire driving module comprises a thyristor and a heating wire, and the input end of the main control MCU is respectively connected to a linear step-down voltage stabilizing module and a zero-crossing detection module, wherein the output end of the linear step-down voltage stabilizing module is also electrically connected to the LED driving module; the zero-crossing detection module comprises a voltage comparator, wherein an inverting input end of the voltage comparator inputs a grid voltage, and a positive input end of the voltage comparator is connected to a positive terminal of a low-voltage power supply, wherein the zero-crossing detection module detects a zero-point phase signal and then feeds it back to the main control MCU, and the main control MCU outputs a pulse to control the thyristor of the heating wire driving module to conduct after receiving the zero-point phase feedback signal.

[0006] Furthermore, the main control MCU adopts a FT60F123 single-chip microcomputer, and a PA3 pin of the main control MCU is connected to an output end of the zero-crossing detection module.

[0007] Further, the voltage comparator in the zero-crossing detection module adopts an LM393DT comparator, a 3.3V voltage is input to pin 8 of the comparator, pin 8 is connected to pin 1 through a resistor R104, pin 4 is grounded through a capacitor C44, the grid voltage is rectified by a diode D4 and connected in sequence to resistors R99, R100, and R101, the other end of resistor R101 is connected to pin 2 of the comparator, resistor R103 and resistor R102 are connected in series, the other end of resistor R103 is grounded, and the other end of resistor R102 is connected to pin 2 of the comparator.

[0008] Furthermore, the linear step-down voltage regulator module includes a KP3310SGA voltage regulator chip, pins 5 to 8 of the voltage regulator chip are connected together to form a common end, the common end is connected to the cathode of the diode U22, the anode of U22 is connected to the fuse, and the other end of the fuse is connected to the pin row; pin 1 of the voltage regulator chip is connected to resistor R143 and then grounded, pin 2 is grounded, pin 4 is grounded through capacitor U26, capacitor C90 and capacitor C88 are connected in parallel, one end of the parallel capacitor is connected to pin 3, and the other end is grounded, and pin 3 is respectively connected to the input end of the main control MCU and the input end of the LED driver module.

[0009] Further, the LED driver module includes a TM1624 driver chip, pin 22 of the driver chip is grounded, pins 23 and 24 of the driver chip are connected to the cathode of the digital tube, pin 4 of the driver chip is connected to the output end of the linear buck voltage regulator module, pins 1, 2, and 3 of the driver chip are respectively connected to pins 6, 4, and 3 of the main control MCU, pins 1, 2, and 3 of the driver chip are respectively connected to the output end of the linear buck voltage regulator module through resistors R88, R87, and R86, and pins 1, 2, and 3 of the driver chip are respectively connected to the output end of the linear buck voltage regulator module through capacitors C36, C35, and C34.

[0010] Furthermore, the digital tube is formed by arranging a plurality of LED lamp beads.

[0011] Furthermore, a single LED lamp bead adopts a 0603 package shape.

[0012] Furthermore, the fuse is of model 4F1A250V.

[0013] Furthermore, the pin header adopts the PZ254V-11-01P model.

[0014] The heating pad control circuit designed by the utility model introduces a zero-crossing detection module to detect the zero-point phase and feed back to the main control MCU. After the main control MCU detects the zero-point phase signal, it outputs a pulse to control the conduction of the thyristor. Compared with the method of giving pulses with a fixed 50HZ frequency in the prior art, power instability caused by phase drift can be prevented. At the same time, by controlling the conduction of the thyristor through the zero-crossing point, the conduction angle can be controlled within a reasonable range to prevent the impact on the power grid caused by conduction at the peak of the sine wave.

[0015] The utility model further reduces the size of the circuit board through the improved design of the power module and the digital tube display circuit, thereby reducing the manufacturing cost and improving the safety of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a functional block diagram of a heating pad control circuit in an embodiment;

[0017] Figure 2 It is the circuit diagram of the linear step-down voltage regulator module;

[0018] Figure 3 This is the circuit diagram of the zero-crossing detection module;

[0019] Figure 4 This is the pin diagram of the main control MCU;

[0020] Figure 5 This is the circuit diagram of the LED driver module. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0022] This embodiment discloses a control circuit of a heating pad, such as Figure 1 As shown, it mainly includes a main control MCU, a linear buck voltage regulator module, an LED driver module, a heating wire driver module, and a zero-crossing detection module. The output end of the main control MCU is connected to the LED driver module and the heating wire driver module respectively. The heating wire driver module controls the conduction or disconnection of the thyristor to achieve heating control of the heating wire. The output end of the linear buck voltage regulator module and the output end of the zero-crossing detection module are respectively connected to the input end of the main control MCU, and the output end of the linear buck voltage regulator module is also connected to the input end of the LED driver module. The zero-crossing detection module compares the input voltage with the low voltage, finds the zero-point phase signal and feeds it back to the main control MCU. After the main control MCU detects the zero-point phase signal, it outputs a pulse to control the conduction of the thyristor. After the thyristor is turned on, the heating wire is energized and heated.

[0023] In the present embodiment, in addition to detecting the zero-point phase by setting the zero-crossing detection module, the circuit is optimized from the design direction of miniaturization. In the prior art, the controller of the heating pad usually adopts a RC step-down scheme for its power supply circuit. The volume of the CBB capacitor or safety capacitor used in this scheme is large, which takes up more space and is not conducive to the miniaturization design of the circuit board. Therefore, in the present embodiment, the power supply circuit is optimized and designed, and the linear step-down voltage stabilizing module based on the KP3310SGA voltage stabilizing chip is used to output a 5V voltage to power the main control MCU and the LED driver module. The optimized power supply circuit in the present embodiment can achieve the same effect of the RC step-down scheme by using a small-volume capacitor voltage stabilizing scheme, and the circuit design is simpler, and the space occupied is also smaller, which helps to reduce the size of the circuit board.

[0024] In addition, the display circuit on the heating pad controller in the prior art usually uses a digital tube to display numbers. Since the digital tube is relatively high, it is not conducive to the miniaturization design of the controller. Therefore, this embodiment also improves the display circuit design, using LED lamp beads arranged in the digital display shape of the digital tube. The single LED lamp bead adopts a 0603 package shape, which is low in height and small in size, which can further reduce the size of the controller. Compared with the traditional digital tube display solution, its manufacturing cost is also lower. The specific circuit design of each of the above modules will be described below.

[0025] like Figure 2 As shown, the linear step-down voltage regulator module in this embodiment mainly adopts the KP3310SGA voltage regulator chip to reduce the 220V voltage to 5V voltage output. The specific circuit description of the module is as follows: Pins 5 to 8 of the voltage regulator chip are connected together to form a common end, the common end is connected to the cathode of the diode U22, the anode of U22 is connected to the fuse 4F1A250V, and the other end of the fuse is connected to the pin row PZ254V-11-01P, pin 1 is grounded through a resistor R143, pin 2 is grounded, pin 4 is grounded through a capacitor U26, capacitor C90 and capacitor C88 are connected in parallel, one end of the parallel capacitor is connected to pin 3, and the other end is grounded. Pin 3 is used as a 5V voltage output terminal to power the main control MCU and the LED driver module respectively.

[0026] like Figure 3 As shown in the figure, the LM393DT voltage comparator is used in the zero-crossing detection module to realize the detection of the zero-point phase. The specific circuit description of the module is as follows: Pin 8 of the comparator inputs a 3.3V voltage, and pin 8 is connected to pin 1 through a resistor R104 to form an output terminal, such as Figure 4 As shown, the main control MCU adopts FT60F123 single-chip microcomputer, the output end of the comparator is connected to the PA3 pin of the main control MCU, pin 4 is grounded through capacitor C44, pin 3 is connected to resistor R123, and the connection of pin 2 forms two branches, one of which is connected to resistor R102 and resistor R103 in sequence and then grounded, and the other is connected to resistor R101, resistor R100, resistor R99 in sequence and then connected to the cathode of diode D4, and the anode of diode D4 is connected to the 220V voltage input terminal.

[0027] like Figure 5As shown, the LED driver module uses the TM1624 driver chip to drive the common cathode LED lamp beads. Only three IO ports are needed to control the LED lamp beads, and the brightness of the LED lamp beads can be set by the program. There is no need to set a current limiting resistor, and the circuit design is simpler. The specific circuit description of the module is as follows: Pin 22 of the driver chip is grounded, pins 23 and 24 of the driver chip are used as the driving connection ends of the LED lamp beads, pin 4 of the driver chip is connected to pin 3 of the KP3310SGA voltage regulator chip, pin 1, pin 2, and pin 3 of the driver chip are respectively connected to pin 6, pin 4, and pin 3 of the FT60F123 microcontroller, pin 1, pin 2, and pin 3 of the driver chip are respectively connected to pin 3 of the KP3310SGA voltage regulator chip through resistors R88, R87, and R86, and pin 1, pin 2, and pin 3 of the driver chip are respectively grounded through capacitors C36, C35, and C34.

[0028] This embodiment reduces the size of the circuit board and the manufacturing cost through the improved design of the above-mentioned control circuit. It can effectively avoid the thyristor controlling the heating wire from being turned on at the peak of the sine wave, and prevent the heating pad from causing impact on the power grid when powered by the power grid, thereby improving the safety of product use.

[0029] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A control circuit of a heating pad, comprising a main control MCU, wherein the output end of the main control MCU is respectively connected to an LED driving module and a heating wire driving module, wherein the heating wire driving module comprises a thyristor and a heating wire, and wherein: The input end of the main control MCU is respectively connected to the linear buck voltage regulator module and the zero-crossing detection module, and the output end of the linear buck voltage regulator module is also electrically connected to the LED driving module; the zero-crossing detection module includes a voltage comparator, the inverting input end of the voltage comparator inputs the grid voltage, and the positive input end of the voltage comparator is connected to the positive terminal of the low-voltage power supply. The zero-crossing detection module detects the zero-point phase signal and then feeds it back to the main control MCU. After receiving the zero-point phase feedback signal, the main control MCU outputs a pulse to control the thyristor of the heating wire driving module to turn on.

2. A control circuit for a heating pad according to claim 1, characterized in that: The main control MCU adopts FT60F123 single chip microcomputer, and the PA3 pin of the main control MCU is connected to the output end of the zero crossing detection module.

3. The control circuit of a heating pad according to claim 1, characterized in that: The voltage comparator in the zero-crossing detection module adopts an LM393DT comparator, a 3.3V voltage is input to pin 8 of the comparator, pin 8 is connected to pin 1 through a resistor R104, pin 4 is grounded through a capacitor C44, the grid voltage is rectified by a diode D4 and connected in sequence to resistors R99, R100, and R101, the other end of resistor R101 is connected to pin 2 of the comparator, resistors R103 and R102 are connected in series, the other end of resistor R103 is grounded, and the other end of resistor R102 is connected to pin 2 of the comparator.

4. The control circuit of a heating pad according to claim 1, characterized in that: The linear step-down voltage regulator module includes a KP3310SGA voltage regulator chip, pins 5 to 8 of the voltage regulator chip are connected together to form a common end, the common end is connected to the cathode of the diode U22, the anode of U22 is connected to the fuse, and the other end of the fuse is connected to the pin row; pin 1 of the voltage regulator chip is connected to the resistor R143 and then grounded, pin 2 is grounded, pin 4 is grounded through capacitor U26, capacitor C90 and capacitor C88 are connected in parallel, one end of the parallel capacitor is connected to pin 3, and the other end is grounded, and pin 3 is respectively connected to the input end of the main control MCU and the input end of the LED driver module.

5. The control circuit of a heating pad according to claim 2, characterized in that: The LED driver module includes a TM1624 driver chip, wherein pin 22 of the driver chip is grounded, pins 23 and 24 of the driver chip are connected to the cathode of the digital tube, pin 4 of the driver chip is connected to the output end of the linear buck voltage regulator module, pins 1, 2 and 3 of the driver chip are respectively connected to pins 6, 4 and 3 of the main control MCU, pins 1, 2 and 3 of the driver chip are respectively connected to the output end of the linear buck voltage regulator module through resistors R88, R87 and R86, and pins 1, 2 and 3 of the driver chip are respectively grounded through capacitors C36, C35 and C34.

6. A control circuit for a heating pad according to claim 5, characterized in that: The digital tube is formed by arranging a plurality of LED lamp beads.

7. A control circuit for a heating pad according to claim 6, characterized in that: The single LED lamp bead adopts 0603 package appearance.

8. The control circuit of a heating pad according to claim 4, characterized in that: The fuse is model 4F1A250V.

9. A control circuit for a heating pad according to claim 4, characterized in that: The pin header adopts the PZ254V-11-01P model.

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