Asymmetric PTC heating control method

Abstract

The invention discloses an asymmetric PTC (Positive Temperature Coefficient) heating control method, which comprises the following steps of: determining the number of switch elements which need to be simultaneously started and the starting duration corresponding to the switch elements according to an execution period and an execution duty ratio, and preferentially starting the switch elements in a full period to meet the requirement of the execution duty ratio; the number of times of opening or closing of each switch element in one cycle control period is at most one, and the opening duration of each switch element in one cycle control period corresponds to the execution duty ratio. According to the invention, the on-off frequency of the switch element can be reduced as much as possible in the cycle control period, the loss can be further reduced, simultaneous on-off of several PTC can be avoided, the impact current is prevented from being too large, the temperature uniformity can be ensured, and the control precision can be improved under the condition of satisfying electromagnetic interference and noise limitation.

Description

TECHNICAL FIELD

[0001] The application relates to an asymmetric PTC heating control method, and belongs to the technical field of thermal management. BACKGROUND

[0002] As a kind of efficient and safe electric heating conversion mode, the positive temperature coefficient (PTC) heating technology has been widely used in household appliances, new energy vehicles, industrial equipment and other fields. The core lies in the use of the unique resistance-temperature characteristics of PTC ceramic or polymer composite material: below the Curie temperature point, the resistivity is low, allowing a larger current to pass through to heat up quickly; when the temperature reaches or exceeds the Curie point, the resistivity will increase by several orders of magnitude, significantly limiting the growth of current, achieving self-limiting temperature function. This characteristic gives PTC heater intrinsic safety advantage, which can effectively prevent fire risk caused by overheating or dry burning.

[0003] However, the traditional PTC heating system control strategy is mainly based on symmetric control principle, such as pulse width modulation control and simple switch control. Pulse width modulation control uses power semiconductor devices (MOSFET, IGBT) to modulate the voltage / current applied to the PTC heater at high frequency, and adjusts the duty cycle to average control the input power of the entire heater, achieving smoother temperature regulation. Simple switch control detects the temperature of a single key point through a temperature sensor, and when the temperature is below the set threshold, a relay or contactor turns on the power supply of the entire PTC heater; when the set temperature is reached, it is completely turned off. Although the above control strategies are simple and easy to implement, they still have the following problems when faced with increasingly complex application scenarios, especially in the presence of uneven or differentiated heat demand: The resistance value of the PTC element is extremely low in the cold state. In switch control, the full-load power supply voltage is directly applied to the PTC element in the cold state with low resistance at the moment of relay closure, resulting in a large impact current much higher than the steady-state working current.

[0004] Switch control lacks continuous or fine adjustment capability of heating power. At the same time, the temperature sensor feedback has hysteresis, and the heated system has thermal inertia. When the temperature reaches the set point and the power is turned off, the residual heat in the system will continue to be released, causing the actual temperature to exceed the set point, resulting in insufficient temperature control accuracy and large fluctuations.

[0005] In the process of repeated and severe temperature rise and fall, different materials will produce significant alternating shear stress and tensile / compressive stress at the material interface and inside the material due to different expansion / contraction degrees. SUMMARY

[0006] The present application aims to overcome the deficiencies in the prior art, and provides an asymmetric PTC heating control method, which aims to eliminate thermal stress, reduce current fluctuation and improve control accuracy.

[0007] To achieve the above object, the present application is implemented by using the following technical solutions: In a first aspect, the present application provides an asymmetric PTC heating control method, comprising: obtaining the total number of switching elements; obtaining a control signal and an execution duty cycle; determining an execution period according to the preset frequency of the switching element; obtaining a cycle control period according to the total number of switching elements and the execution period; determining the number of switching elements that need to be turned on simultaneously and the on duration of the switching elements corresponding to the execution period and the execution duty cycle; wherein, the switching elements are preferentially turned on for a full period to meet the demand of the execution duty cycle; the number of on / off times of each switching element in a cycle control period is at most once, and the on duration of each switching element in a cycle control period corresponds to the execution duty cycle; adjacent switching elements are turned on in turn in an opposite phase manner with an interval of one execution period.

[0008] Further, the execution period is defined as T, and the total number of switching elements is defined as N, then the cycle control period T1 is represented as: T1=T*N.

[0009] Further, the execution duty cycle is defined as D, then in one execution period, the sum of the on duration of all switching elements divided by T*N is equal to the execution duty cycle D.

[0010] Further, in a cycle control period, the ratio of the on duration of each switching element to T1 is equal to the execution duty cycle D.

[0011] Further, each of the switching elements is connected to a group of PTCs, and the switching elements are used to control the on and off of the corresponding PTCs.

[0012] Further, the PTCs connected by adjacent switching elements have a preset gap width.

[0013] In a second aspect, the present application provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to realize the steps of the method in any one of the preceding aspects.

[0014] In a third aspect, the present application provides a computer device, comprising: a memory for storing computer programs / instructions; a processor for executing the computer programs / instructions to implement the steps of the method of any one of the preceding.

[0015] Compared with the prior art, the present application has the following beneficial effects: The present application provides an asymmetric PTC heating control method, the execution period is determined according to the frequency of the control signal; the cycle control period is obtained according to the total number of switching elements and the execution period, and the number of switching elements that need to be turned on simultaneously and the on duration of the switching elements are determined according to the execution period and the execution duty cycle, the present application preferentially turns on the switching elements through full period to meet the demand of the execution duty cycle, so that the number of switching elements that need to be turned on in the same execution period can be minimized, and the loss can be reduced.

[0016] The present application also sets that the number of on / off times of each switching element in a cycle control period is at most once, so that the on / off times of the switching elements in the cycle control period can be minimized, the loss can be further reduced, and the simultaneous turning on of several PTCs can be avoided to prevent the excessive impact current.

[0017] The present application realizes cycle control through cycle control period, which can guarantee the uniformity of temperature and improve the control precision under the condition of meeting the electromagnetic interference and noise limit. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a control flow chart of the asymmetric PTC heating control method of the present application; Figure 2 is a reverse sequence time-sharing wheel sequence control flow chart in the embodiment of the present application; Figure 3 is a 3-way IGBT control strategy (duty cycle less than or equal to 33.3%); Figure 4 is a 3-way IGBT control strategy (duty cycle greater than 33.3% and less than or equal to 66.6%); Figure 5 is a 3-way IGBT control strategy (duty cycle greater than 66.6%); Figure 6 is a 4-way IGBT control strategy (duty cycle less than or equal to 25%); Figure 7 is a 4-way IGBT control strategy (duty cycle greater than 25% and less than or equal to 50%); Figure 8 is a 4-way IGBT control strategy (duty cycle greater than 50% and less than or equal to 75%); Figure 9 is a 4-way IGBT control strategy (duty cycle greater than 75%). DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0020] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0021] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances. Example

[0022] See also Figure 1 and Figure 2 This embodiment introduces an asymmetric PTC heating control method, and the switching element is set to IGBT. In other embodiments, other types of switching elements that can achieve the same function can be used.

[0023] Each IGBT is connected to a group of PTCs, and the IGBT is used to control the opening and closing of the corresponding PTC. There is a preset gap width between the PTCs connected to adjacent IGBTs.

[0024] The asymmetric PTC heating control method of this embodiment includes the following steps: S100: Obtain the total number of switching elements.

[0025] S200: Acquire a control signal and execute a duty cycle.

[0026] S300, determine an execution period according to the frequency preset for the switching element; determine a cycle control period according to the total number of switching elements and the execution period.

[0027] S400, determine the number of switching elements that need to be turned on simultaneously and the on duration of the switching elements according to the execution period and the execution duty cycle.

[0028] Among them, the switching elements are preferentially turned on for a full period to meet the execution duty cycle; the number of times each switching element is turned on or turned off within a cycle control period is at most once, and the on duration of each switching element within a cycle control period corresponds to the execution duty cycle; adjacent switching elements of each path are turned on in a staggered manner with an interval of one execution period.

[0029] Specifically, the execution period is defined as T, the total number of switching elements is N, and the cycle control period T1 is represented as: T1=T*N. The execution duty cycle is defined as D, and the sum of the on durations of all switching elements within one execution period is equal to the execution duty cycle D divided by T*N. Within one cycle control period, the on duration of the switching elements of each path is equal to the execution duty cycle D divided by T1.

[0030] The asymmetric PTC heating control method provided by the application has the following characteristics: The total cycle control period T1 is composed of the sum of the periods T of N single-channel IGBTs. By adding a small period T, the multiple of the cycle control period T1 can be virtually increased to improve the control accuracy of the duty cycle.

[0031] The impact current is reduced by limiting the number of times each switching element is turned on or turned off within a cycle control period to at most once, which can stagger the on time of multiple IGBTs and avoid the problem of excessive impact current caused by simultaneous opening of several PTCs.

[0032] Thermal stress elimination: By limiting the on duration of the same PTC within a cycle control period, and the corresponding PTC physical position is also interval, the problem of local high heat caused by adjacent PTC heating can be avoided, and the problem of thermal stress elimination can be solved.

[0033] Temperature uniformity: cycle control is performed according to the large period T to achieve temperature uniformity.

[0034] Precision improvement: at a frequency of 10 Hz, a duty cycle of 1% (an integer, cannot be a decimal, because increasing one decimal place requires increasing the frequency by 10 times, and the corresponding EMC (electromagnetic interference) and noise cannot meet the requirements), through the cycle control period T1, the precision is improved to 1% divided by N, and the precision is improved under the condition of meeting the EMC and noise limits. Example

[0035] This embodiment provides an asymmetric PTC heating control method. Based on the first embodiment, it more specifically sets how to control when the number of IGBTs is an odd number, such as Figure 3 、 Figure 4 and Figure 5 As shown, taking 3-way IGBT as an example, the following steps are included: like Figure 3 As shown, because there are only three IGBTs, each accounts for 33.3%. When the execution duty cycle sent by the thermal management system is less than or equal to 33.3%, when the frequency is 10 Hz, a cycle T is 0.1s. Therefore, only one IGBT needs to be turned on during a cycle, and the time-sharing operation ensures that each IGBT is heated evenly, avoiding thermal stress caused by continuous heating of one IGBT.

[0036] Figure 4 When the thermal management system sends an execution duty cycle greater than 33.3% and less than or equal to 66.6%, both IGBTs need to be turned on. Based on the staggered start-up principle, during the first execution cycle, the first IGBT is fully turned on, while the third IGBT is adjusted to the required opening (in this embodiment, the opening refers to the duration of the IGBT's on-state) to meet the required duty cycle. During the second execution cycle, to avoid large current fluctuations caused by the third IGBT turning off and the second IGBT turning on, the third IGBT is fully turned on, while the second IGBT is adjusted to the required opening to meet the required duty cycle. During the third execution cycle, the second IGBT is fully turned on, while the first IGBT is adjusted to the required opening to meet the required duty cycle. This cycle repeats in sequence. This prevents the problem of excessive inrush current.

[0037] Figure 5 When the execution duty cycle sent by the thermal management system is greater than 66.6%, it is necessary to turn on all three IGBTs. During the first execution cycle, the first and third IGBTs are fully turned on, and the second IGBT is adjusted to the required opening to meet the duty cycle requirements. During the second execution cycle, the second and third IGBTs are fully turned on, and the first IGBT is adjusted to the required opening to meet the duty cycle requirements. During the third execution cycle, the first and second IGBTs are fully turned on, and the third IGBT is adjusted to the required opening to meet the duty cycle requirements, and so on. This can suppress inrush current and reduce thermal stress.

[0038] This avoids the problem of a certain IGBT being heated all the time, and also avoids opening multiple IGBTs at the same time, which would cause excessive inrush current. The original minimum duty cycle accuracy was increased from 1% to 0.33% through this algorithm, and the control accuracy was also improved. Example

[0039] The embodiment provides an asymmetric PTC heating control method. On the basis of the embodiment 1, how to control is more specifically set in the case that the number of IGBTs is even, as shown in Figure 6 、 Figure 7 、 Figure 8 and Figure 9 , taking 4-way IGBTs as an example, the method comprises the following steps: Please refer to Figure 6 Because there are 4-way IGBTs, each way accounts for 25%. When the duty cycle is less than or equal to 25%, when the frequency is 10HZ, one cycle is 0.1S, and therefore only one way of IGBT needs to be turned on in one cycle. By time-sharing opening, it can be ensured that each way of PTC can be uniformly heated, and the problem of thermal stress caused by continuous heating of a certain way of IGBT can be avoided.

[0040] Please refer to Figure 7 When the execution duty cycle sent by the thermal management system is greater than 25% and less than or equal to 50%, two ways of IGBTs need to be turned on. In the first execution cycle, the first way of IGBT is fully turned on, and the third way of IGBT is adjusted to the required opening degree; in the second execution cycle, in order to avoid that the third way of IGBT is turned off and the second way of IGBT is turned on to cause large current fluctuation, the third way of IGBT is fully turned on, and the second way of IGBT is adjusted to the required opening degree; in the third execution cycle, the second way of IGBT is fully turned on, and the fourth way of IGBT is adjusted to the required opening degree; in the fourth execution cycle, the fourth way of IGBT is fully turned on, and the first way of IGBT is adjusted to the required opening degree. The above steps are repeated. In this way, each way of IGBT can be uniformly heated, and meanwhile, the problem of large impact current caused by simultaneous opening of multiple ways of IGBT can be avoided.

[0041] Please refer to Figure 8 When the execution duty cycle sent by the thermal management system is greater than 50% and less than or equal to 75%, three ways of IGBTs need to be turned on. In the first execution cycle, the first way of IGBT and the fourth way of IGBT are fully turned on, and the second way of IGBT is adjusted to the required opening degree. In the second execution cycle, the first way of IGBT and the second way of IGBT are fully turned on, and the third way of IGBT is adjusted to the required opening degree. In the third execution cycle, the second way of IGBT and the third way of IGBT are fully turned on, and the fourth way of IGBT is adjusted to the required opening degree. In the fourth execution cycle, the third way of IGBT and the fourth way of IGBT are fully turned on, and the first way of IGBT is adjusted to the required opening degree. The above steps are repeated. In this way, the impact current can be inhibited, and the thermal stress can be reduced.

[0042] Please refer to Figure 9When the execution duty ratio sent by the heat management system is greater than 75%, four paths need to be opened, in the first execution period, the first path IGBT, the second path IGBT and the third path IGBT are fully opened, and the fourth path IGBT is adjusted to the required opening degree. In the second execution period, the second path IGBT, the third path IGBT and the fourth path IGBT are fully opened, and the first path IGBT is adjusted to the required opening degree. In the third execution period, the first path IGBT, the third path IGBT and the fourth path IGBT are fully opened, and the second path IGBT is adjusted to the required opening degree. In the fourth execution period, the first path IGBT, the second path IGBT and the fourth path IGBT are fully opened, and the third path IGBT is adjusted to the required opening degree, and so on. In this way, the impact current can be inhibited and the thermal stress can be reduced.

[0043] In this way, the problem of heating a certain path IGBT all the time is avoided, and the problem of opening multiple path IGBTs at the same time is avoided, and the problem of excessive impact current is avoided, and the minimum precision of the original duty ratio is 1%, which is improved to 0.25% by the method of the present application.

[0044] Embodiment 4 provides a computer readable storage medium having stored thereon a computer program, which, when executed by a processor, implements the steps of the method of any one of Embodiment 1.

[0045] Embodiment 5 provides a computer device, comprising: a memory for storing computer programs / instructions; a processor for executing the computer programs / instructions to implement the steps of the method of any one of Embodiment 1.

[0046] Embodiment 6 provides a computer program product comprising computer programs / instructions, which, when executed by a processor, implement the steps of the method of any one of Embodiment 1.

[0047] The above only describes the preferred embodiments of the present application, and it should be pointed out that for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

[0048] Those skilled in the art will appreciate that embodiments of the present disclosure can be provided as methods, systems or computer program products. Therefore, the present disclosure can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Moreover, the present disclosure can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0049] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0050] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0051] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0052] Finally, it should be noted that the above-mentioned embodiments are only used to illustrate the technical solutions of the present disclosure, rather than limit the protection scope of the present disclosure. Although the present disclosure has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that, after reading the present disclosure, the specific embodiments of the present disclosure can be modified, changed or replaced by equivalents without departing from the principles of the present disclosure. These modifications, changes or replacements are also within the scope of protection of the appended claims.

Claims

1. An asymmetric PTC heating control method, characterized in that: include: Get the total number of switch elements; Get control signals and implement duty cycles; determining an execution cycle according to a preset frequency of the switching element; Obtaining a loop control period according to the total number of switching elements and an execution period; Determine the number of switching elements that need to be turned on simultaneously and the corresponding turn-on time of the switching elements according to the execution cycle and the execution duty cycle; Among them, the switching element is preferably turned on through a full cycle to meet the demand of the execution duty cycle; Each switching element is turned on or off a maximum of once in a cyclic control period, and the duration of the on-state of each switching element in a cyclic control period corresponds to the execution duty cycle; each adjacent switching element is turned on in a staggered manner at intervals of an execution period.

2. The asymmetric PTC heating control method according to claim 1, characterized in that: The execution period is defined as T, and the total number of switch elements is defined as N. Then the cyclic control period T1 is expressed as: T1=T*N.

3. The asymmetric PTC heating control method according to claim 2, characterized in that: The execution duty cycle is defined as D. Then, in one execution cycle, the ratio of the sum of the on-times of all switching elements to T*N is equal to the execution duty cycle D.

4. The asymmetric PTC heating control method according to claim 3, characterized in that: In a cyclic control period, the ratio of the on-time of each switching element to T1 is equal to the execution duty cycle D.

5. The asymmetric PTC heating control method according to claim 1, characterized in that: Each of the switching elements is connected to a group of PTCs, and the switching element is used to control the opening and closing of the corresponding PTC.

6. The asymmetric PTC heating control method according to claim 1, characterized in that: There is a preset gap width between the PTCs connected to adjacent switching elements.

7. A computer-readable storage medium, characterized in that A computer program is stored thereon, and when the program is executed by a processor, the steps of the asymmetric PTC heating control method as described in any one of claims 1 to 6 are implemented.

8. A computer device, characterized in that: include: Memory, used to store computer programs / instructions; A processor is used to execute the computer program / instructions to implement the steps of the asymmetric PTC heating control method as described in any one of claims 1 to 6.

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