A PTC heating circuit and a heating method

Abstract

The application provides a PTC heating circuit and a heating method, which comprises the following steps: connecting the first end of the first-stage switching circuit with the L-phase line of an external AC power supply; connecting the second end of the first-stage switching circuit with the first end of the second-stage switching circuit; connecting the third end of the first-stage switching circuit with an external DC power supply; connecting the fourth end of the first-stage switching circuit with an external controller; the first-stage switching circuit comprises a relay; connecting the second end of the second-stage switching circuit with the first end of a PTC heater; connecting the third end of the second-stage switching circuit with the external DC power supply; connecting the fourth end of the second-stage switching circuit with the external controller; and connecting the second end of the PTC heater with the N-phase line of the external AC power supply. By implementing the application, the relay is not directly subjected to the large current impact of the ceramic PTC heater when it is first turned on, so that the relay type does not need to be increased, and the cost increase caused by the relay is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic devices, in particular to a PTC heating circuit and a heating method. BACKGROUND

[0002] The PTC heater is a device composed of a PTC ceramic heating element and an aluminum pipe, which is widely used in heating appliances such as air heaters and bath heaters. The PTC heater has the characteristics that the internal resistance is relatively small in the cold state, and the current is very large when starting, thereby resulting in a large starting power of the heating appliance. For example, the nominal heating power of some appliances equipped with PTC heaters is 2KW, and when the PTC heater starts in the cold state, the starting power of the appliance may reach 3KW or even more. In this case, when a relay is used to directly drive the ceramic PTC heater, the capacity of the relay needs to be selected to be twice the rated value, thereby resulting in an increase in the cost of the relay. SUMMARY

[0003] Therefore, the technical problem to be solved by the present application is to overcome the defect of high cost of the relay in the PTC heating circuit in the prior art, thereby providing a PTC heating circuit and a heating method.

[0004] The technical scheme provided by the present application is as follows:

[0005] In a first aspect, the present application provides a PTC heating circuit, comprising: a first-stage switching circuit, a second-stage switching circuit and a PTC heater, wherein a first end of the first-stage switching circuit is connected with an L-phase line of an external AC power supply, a second end of the first-stage switching circuit is connected with a first end of the second-stage switching circuit, a third end of the first-stage switching circuit is connected with an external DC power supply, a fourth end of the first-stage switching circuit is connected with an external controller, and the first-stage switching circuit comprises a relay; a second end of the second-stage switching circuit is connected with a first end of the PTC heater, a third end of the second-stage switching circuit is connected with the external DC power supply, and a fourth end of the second-stage switching circuit is connected with the external controller; and a second end of the PTC heater is connected with an N-phase line of the external AC power supply.

[0006] Optionally, a first end of the relay coil is connected with the external DC power supply, a second end of the relay coil is connected with the external controller, a first end of the relay normally open switch is connected with the L-phase line of the external AC power supply, and a second end of the relay normally open switch is connected with the first end of the second-stage switching circuit.

[0007] Optionally, the first-stage switching circuit further comprises a diode, a cathode of the diode is connected with the first end of the relay coil, and an anode of the diode is connected with the second end of the relay coil.

[0008] Optionally, the second-stage switch circuit comprises a thyristor, a thyristor protection circuit and a thyristor gate drive circuit, wherein the first end of the thyristor is connected with the first end of the thyristor protection circuit, the second end of the thyristor is connected with the second end of the thyristor protection circuit and the third end of the thyristor gate drive circuit respectively, and the third end of the thyristor is connected with the fourth end of the thyristor gate drive circuit; the first end of the thyristor gate drive circuit is connected with an external DC power supply, and the second end of the thyristor gate drive circuit is connected with an external controller.

[0009] Optionally, the thyristor protection circuit comprises a first resistor and a first capacitor, wherein the first end of the first capacitor is connected with the first end of the thyristor, and the second end of the first capacitor is connected with the second end of the thyristor through the first resistor.

[0010] Optionally, the thyristor gate drive circuit comprises an optoelectronic coupler, a second resistor and a third resistor, wherein the first end of the optoelectronic coupler is connected with an external DC power supply, the second end of the optoelectronic coupler is connected with an external controller through the third resistor, the third end of the optoelectronic coupler is connected with the second end of the thyristor through the second resistor, and the fourth end of the optoelectronic coupler is connected with the third end of the thyristor.

[0011] Optionally, the PTC heating circuit further comprises a controller, which is further connected with the second end of the optoelectronic coupler and the second end of the relay coil respectively.

[0012] In the second aspect, an embodiment of the present application provides a PTC heating method based on the PTC heating circuit in the first aspect of the present application, and the PTC heating method comprises the following steps: obtaining a user demand; when the user demand is to turn on the air-warm bath heater, sending a low-level signal to drive the first-stage switch circuit to open, and after a first preset time, sending a low-level signal to drive the second-stage switch circuit to open; when the user demand is to turn off the air-warm bath heater, sending a high-level signal to drive the second-stage switch circuit to close, and after a second preset time, sending a high-level signal to drive the first-stage switch circuit to close.

[0013] Optionally, before the step of sending a low-level signal to drive the first-stage switch circuit to open, the method further comprises the following step: judging whether the PTC heater is in a cold-state start.

[0014] The technical scheme of the present application has the following advantages:

[0015] The PTC heating circuit provided by the application comprises a first-stage switching circuit, a second-stage switching circuit and a PTC heater, wherein the first end of the first-stage switching circuit is connected with the L-phase line of an external AC power supply, the second end of the first-stage switching circuit is connected with the first end of the second-stage switching circuit, the third end of the first-stage switching circuit is connected with an external DC power supply, the fourth end of the first-stage switching circuit is connected with an external controller, and the first-stage switching circuit comprises a relay; the second end of the second-stage switching circuit is connected with the first end of the PTC heater, the third end of the second-stage switching circuit is connected with the external DC power supply, the fourth end of the second-stage switching circuit is connected with the external controller, and the second end of the PTC heater is connected with the N-phase line of the external AC power supply. The two-stage switching circuit is used to control the working of the PTC heater, the opening and closing actions of the first-stage switching circuit comprising the relay are performed in the environment without the current loop, the relay is switched under low load, the relay is prevented from directly suffering the large current impact when the ceramic PTC heater is first opened, and thus the relay type is not required to be increased, and the cost increase is avoided.

[0016] The PTC heating method provided by the application comprises the following steps: obtaining user demand; when the user demand is to open the air bath heater, sending a low-level signal to drive the first-stage switching circuit to open, and sending a low-level signal to drive the second-stage switching circuit to open after a first preset time; and when the user demand is to close the air bath heater, sending a high-level signal to drive the second-stage switching circuit to close, and sending a high-level signal to drive the first-stage switching circuit to close after a second preset time. The opening and closing actions of the first-stage switching circuit comprising the relay are performed in the environment without the current loop, the relay is switched under low load, the relay is prevented from directly suffering the large current impact when the ceramic PTC heater is first opened, and thus the relay type is not required to be increased, and the cost increase is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0018] Figure 1 The principle block diagram of a specific example of the PTC heating circuit in the embodiments of the application;

[0019] Figure 2 The PTC heating circuit diagram of a specific example in the embodiments of the application;

[0020] Figure 3A flow chart of one specific example of the PTC heating method in the embodiments of the present application. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0022] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements, or it can be wireless connection, or it can be wired connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0024] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0025] Due to the characteristics of the ceramic PTC heater, when the air heating function of the air heating bath heater is first turned on, the power of the PTC heater will usually reach twice the rated power within 30 seconds of turning on the ceramic PTC heater. When a relay is used to directly drive the ceramic PTC heater, the capacity of the relay needs to be selected to reach twice the rated value, which greatly increases the cost of the relay. Therefore, the embodiments of the present application provide a PTC heating circuit applied to a bath heater control system to reduce the cost of the relay.

[0026] As Figure 1As shown, the PTC heating circuit includes: a first-stage switching circuit, a second-stage switching circuit, and a PTC heater. The first terminal of the first-stage switching circuit is connected to the L-phase line of an external AC power supply; the second terminal of the first-stage switching circuit is connected to the first terminal of the second-stage switching circuit; the third terminal of the first-stage switching circuit is connected to an external DC power supply; and the fourth terminal of the first-stage switching circuit is connected to an external controller. The first-stage switching circuit includes a relay. The second terminal of the second-stage switching circuit is connected to the first terminal of the PTC heater; the third terminal of the second-stage switching circuit is connected to the external DC power supply; and the fourth terminal of the second-stage switching circuit is connected to the external controller. The second terminal of the PTC heater is connected to the N-phase line of the external AC power supply. The relay... Figure 1 Not shown in the image.

[0027] In one specific embodiment, a two-stage switching circuit is used to control the operation of the PTC heater. The first-stage switching circuit, including a relay, is installed at the front near the 220VAC / 50Hz AC power supply terminal, and the second-stage switching circuit is installed at the rear near the PTC heater terminal. When the user needs to use the bathroom heater function, the external controller sends a control signal to activate the first-stage switching circuit. After a first preset time, the external controller sends a control signal to activate the second-stage switching circuit. When the user does not need to use the bathroom heater function, the external controller sends a control signal to deactivate the second-stage switching circuit. After a second preset time, the external controller sends a control signal to deactivate the first-stage switching circuit. In this embodiment, the first and second preset times are determined based on actual conditions.

[0028] By controlling the timing of the switching circuit, the first-stage switching circuit, including the relay, operates in an environment without a current loop, allowing the relay to switch under low load. This avoids the relay being directly subjected to the large current surge when the ceramic PTC heater is first turned on, significantly extending the relay's lifespan. Furthermore, there is no need to consider the increased cost caused by using a larger relay model.

[0029] In one embodiment, such as Figure 2 As shown, RY1 is the symbol for a relay. The first terminal of the RY1 coil is connected to an external DC power supply, the second terminal of the RY1 coil is connected to an external controller, the first terminal of the normally open switch of the RY1 relay is connected to the L-phase line of the external AC power supply, and the second terminal of the normally open switch of the RY1 relay is connected to the first terminal of the second-stage switching circuit.

[0030] In one specific embodiment, the first-stage switching circuit further includes: a diode D1, the cathode of which is connected to the first end of the coil of relay RY1, and the anode of which is connected to the second end of the coil of relay RY1.

[0031] In this embodiment of the invention, the fan-heated bathroom heater control system uses a 220VAC / 50HZ power supply, and the ceramic PTC heater can reach a maximum power of 3000W. When power is supplied to the ceramic PTC heater, it heats up, and the fan-heated bathroom heater generates a heat source. An external +12V DC power supply powers the coil circuit of relay RY1. D1 is a relay protection diode used to protect relay RY1. IO1 is the signal code of the MCU unit of the fan-heated bathroom heater control system. The MCU unit controls the level signal of IO1 to turn relay RY1 on and off.

[0032] In one embodiment, the second-stage switching circuit includes: a thyristor Q1, a thyristor protection circuit, and a thyristor gate drive circuit. The first terminal of the thyristor Q1 is connected to the first terminal of the thyristor protection circuit, the second terminal of the thyristor Q1 is connected to both the second terminal of the thyristor protection circuit and the third terminal of the thyristor gate drive circuit, and the third terminal of the thyristor Q1 is connected to the fourth terminal of the thyristor gate drive circuit. The first terminal of the thyristor gate drive circuit is connected to an external DC power supply, and the second terminal of the thyristor gate drive circuit is connected to an external controller.

[0033] In one specific embodiment, such as Figure 2 As shown, the thyristor protection circuit includes: a first resistor R1 and a first capacitor CX1, wherein the first terminal of the first capacitor CX1 is connected to the first terminal of the thyristor Q1, and the second terminal of the first capacitor CX1 is connected to the second terminal of the thyristor Q1 through the first resistor R1.

[0034] The thyristor gate drive circuit includes: an optocoupler U1, a second resistor R2, and a third resistor R3. The first terminal of the optocoupler U1 is connected to an external DC power supply, the second terminal of the optocoupler U1 is connected to an external controller through the third resistor R3, the third terminal of the optocoupler U1 is connected to the second terminal of the thyristor Q1 through the second resistor R2, and the fourth terminal of the optocoupler U1 is connected to the third terminal of the thyristor Q1.

[0035] In this embodiment of the invention, an external +5V DC power supply powers the optocoupler U1. IO2 is the signal code of the MCU unit of the bathroom heater control system. The MCU unit controls the level signal of IO2 to turn the thyristor gate drive circuit on and off, thereby using the thyristor gate drive circuit to drive the thyristor Q1 to turn on and off. When relay RY1 and thyristor Q1 are both in the on state, the ceramic PTC heater is in working state, generating a heat source.

[0036] Specifically, when the relay RY1 is turned on for 500 ms by the MCU unit controlling the low-level signal of IO1, the thyristor Q1 is turned on by the MCU unit controlling the low-level signal of IO2. When the thyristor Q1 is turned off for 500 ms by the MCU unit controlling the high-level signal of IO2, the relay RY1 is turned off by the MCU unit controlling the high-level signal of IO1. The turning on and off of the relay RY1 in the environment without a current loop allows the relay RY1 to be a low-load switch, avoiding the direct impact of the large current of the ceramic PTC heater when it is turned on for the first time, greatly prolonging the service life of the relay RY1. In addition, the cost increase caused by increasing the relay model does not need to be considered. The protection of the relay RY1 is realized by controlling the switching sequence of the relay RY1 and the thyristor Q1, thereby realizing the economy and reliability of the relay RY1 selection.

[0037] In an embodiment, a two-stage switching scheme of a first relay RY1 and a first thyristor Q1 in series is used to control the ceramic PTC heater in the bathroom heater. The relay RY1 is installed at the front near the power supply 220VAC / 50HZ end, and the thyristor Q1 is installed at the rear end near the ceramic PTC heater end. When the user needs to use the bathroom heater, the wind-warm bathroom heater control system needs to simultaneously act on the front and rear relays RY1 and thyristors Q1 to realize the work of the ceramic PTC heater, avoiding the wind-warm bathroom heater control system failure caused by the hardware failure short circuit of a single switch or the misoperation of a single switch.

[0038] In an embodiment, the relay RY1 is installed at the front near the power supply 220VAC / 50HZ end, and the thyristor Q1 is installed at the rear end near the ceramic PTC load end. During the period when the user does not use the bathroom heater, the thyristor Q1 is always in a non-powered state due to the relay RY1 being turned off, avoiding the long-term impact of the power grid on the thyristor Q1, thereby prolonging the service life of the thyristor Q1 and further prolonging the service life of the ceramic PTC heater control scheme.

[0039] In an embodiment, the PTC heating circuit further comprises a controller, and the controller is further connected with the second end of the optoelectronic coupler and the second end of the relay coil, respectively.

[0040] In a specific embodiment, the controller is an MCU unit. The MCU unit uses the level signal of IO1 to realize the turning on and off of the relay RY1. The MCU unit uses the level signal of IO2 to realize the conduction and cutoff of the thyristor gate drive circuit, and further uses the thyristor gate drive circuit to drive the turning on and off of the thyristor Q1.

[0041] The embodiment of the present application also provides a PTC heating method based on the PTC heating circuit, the PTC heating method comprises the following steps: Figure 3 as shown in the figure, comprising the following steps:

[0042] Step S1: obtaining user demand.

[0043] In a specific embodiment, the user demand comprises starting the air-warming bath heater and stopping the air-warming bath heater.

[0044] Step S2: when the user demand is starting the air-warming bath heater, a low-level signal is sent to drive the first-stage switch circuit to open, and after a first preset time, a low-level signal is sent to drive the second-stage switch circuit to open.

[0045] In a specific embodiment, when the user demand is starting the air-warming bath heater, it is further needed to judge whether the PTC heater is cold-state starting. If the PTC heater is cold-state starting, the two-stage switch control mode is adopted to start the PTC heater, so as to avoid the relay directly suffering from the large current impact when the ceramic PTC heater is started for the first time.

[0046] In the embodiment of the present application, when the user demand is starting the air-warming bath heater, the low-level signal of IO1 controlled by the MCU unit is used to realize that the relay RY1 is opened for 500 ms, and then the low-level signal of IO2 controlled by the MCU unit is used to realize that the thyristor Q1 is opened. In the embodiment of the present application, the first preset time is 500 ms, which is only an example and is not limited thereto.

[0047] Step S3: when the user demand is stopping the air-warming bath heater, a high-level signal is sent to drive the second-stage switch circuit to close, and after a second preset time, a high-level signal is sent to drive the first-stage switch circuit to close.

[0048] In a specific embodiment, when the user demand is starting the air-warming bath heater, the high-level signal of IO2 controlled by the MCU unit is used to realize that the thyristor Q1 is closed for 500 ms, and then the high-level signal of IO1 controlled by the MCU unit is used to realize that the relay RY1 is closed. In the embodiment of the present application, the second preset time is 500 ms, which is only an example and is not limited thereto.

[0049] The opening and closing actions of the relay RY1 are in the environment without current loop, the relay RY1 is low-load switched, the relay RY1 directly suffers from the large current impact when the ceramic PTC heater is started for the first time is avoided, and the service life of the relay RY1 is greatly prolonged. In addition, the cost increase caused by increasing the relay model does not need to be considered. The protection of the relay RY1 is realized by controlling the switch sequence of the relay RY1 and the thyristor Q1, so that the economy and reliability of the relay RY1 selection are realized.

[0050] Obviously, the above embodiments are merely example for clearly illustrating but not limitation to the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments need not and can not be enumerated. The obvious changes or variations derived from the above description are still within the protection scope of the present application.

Claims

1. A PTC heating circuit, characterized in that, include: The circuit consists of a first-stage switching circuit, a second-stage switching circuit, and a PTC heater. The first terminal of the first-stage switching circuit is connected to the L-phase line of the external AC power supply, the second terminal of the first-stage switching circuit is connected to the first terminal of the second-stage switching circuit, the third terminal of the first-stage switching circuit is connected to the external DC power supply, and the fourth terminal of the first-stage switching circuit is connected to the external controller. The first-stage switching circuit includes a relay. The second terminal of the second-stage switching circuit is connected to the first terminal of the PTC heater, the third terminal of the second-stage switching circuit is connected to an external DC power supply, and the fourth terminal of the second-stage switching circuit is connected to an external controller. The second end of the PTC heater is connected to the N-phase line of an external AC power supply; When the user requests to turn on the fan-heated bathroom heater, a low-level signal is sent to drive the first-stage switching circuit to turn on, and after a first preset time, a low-level signal is sent to drive the second-stage switching circuit to turn on; when the user requests to turn off the fan-heated bathroom heater, a high-level signal is sent to drive the second-stage switching circuit to turn off, and after a second preset time, a high-level signal is sent to drive the first-stage switching circuit to turn off.

2. The PTC heating circuit according to claim 1, characterized in that, The first end of the relay coil is connected to an external DC power supply, the second end of the relay coil is connected to an external controller, the first end of the normally open switch of the relay is connected to the L phase line of the external AC power supply, and the second end of the normally open switch of the relay is connected to the first end of the second-stage switching circuit.

3. The PTC heating circuit according to claim 2, characterized in that, The first-stage switching circuit further includes a diode, wherein the cathode of the diode is connected to a first end of the relay coil, and the anode of the diode is connected to a second end of the relay coil.

4. The PTC heating circuit according to claim 2, characterized in that, The second-stage switching circuit includes: a thyristor, a thyristor protection circuit, and a thyristor gate drive circuit, wherein, The first terminal of the thyristor is connected to the first terminal of the thyristor protection circuit, the second terminal of the thyristor is connected to the second terminal of the thyristor protection circuit and the third terminal of the thyristor gate drive circuit, and the third terminal of the thyristor is connected to the fourth terminal of the thyristor gate drive circuit. The first terminal of the thyristor gate drive circuit is connected to an external DC power supply, and the second terminal of the thyristor gate drive circuit is connected to an external controller.

5. The PTC heating circuit according to claim 4, characterized in that, The thyristor protection circuit includes: a first resistor and a first capacitor, wherein, The first terminal of the first capacitor is connected to the first terminal of the thyristor, and the second terminal of the first capacitor is connected to the second terminal of the thyristor through the first resistor.

6. The PTC heating circuit according to claim 4, characterized in that, The thyristor gate drive circuit includes: an optocoupler, a second resistor, and a third resistor, wherein, The first end of the optocoupler is connected to an external DC power supply, the second end of the optocoupler is connected to an external controller through the third resistor, the third end of the optocoupler is connected to the second end of the thyristor through the second resistor, and the fourth end of the optocoupler is connected to the third end of the thyristor.

7. The PTC heating circuit according to claim 6, characterized in that, It also includes a controller, which is connected to the second end of the optocoupler and the second end of the relay coil, respectively.

8. A PTC heating method, characterized in that, Based on the PTC heating circuit according to any one of claims 1-7, the PTC heating method includes: Obtain user needs; When the user requests to turn on the fan-heated bathroom heater, a low-level signal is sent to drive the first-level switching circuit to turn on, and after a first preset time, a low-level signal is sent to drive the second-level switching circuit to turn on. When the user requests to turn off the fan-heated bathroom heater, a high-level signal is sent to drive the second-stage switching circuit to turn off, and after a second preset time, a high-level signal is sent to drive the first-stage switching circuit to turn off.

9. The PTC heating method according to claim 8, characterized in that, Before executing the step of sending a low-level signal to drive the first-stage switching circuit to turn on, the following steps are also included: Determine if the PTC heater is cold-started.

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