Zero-crossing trigger type solid-state relay control method and system
By grouping or parallel solid-state relays and performing phase shift control, the problem of high failure rate of zero-crossing trigger solid-state relays at high frequencies is solved, and high control accuracy and low-cost heating or lighting control are achieved.
Patent Information
- Application Number
- CN202510496232.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-21
- Publication Date
- 2025-08-12
AI Technical Summary
The existing zero-crossing trigger type solid-state relays are difficult to achieve high control accuracy without increasing the switching frequency, especially in high-power heating systems and lighting systems, resulting in high failure rates and poor control effects.
By grouping or connecting heating elements or lighting devices, using multiple solid-state relays and performing phase shift control, the on-cycle is reduced without increasing the switching frequency of a single relay, thereby achieving an improvement in control accuracy.
Without increasing the failure rate, the temperature control accuracy of the heating system and the brightness uniformity of the lighting system are improved, the cost is reduced, and the control effect of the thyristor can be replaced.
Smart Images
Figure CN120474540A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of environmental control, and in particular to a zero-crossing triggered solid-state relay control method and system for heating elements and lighting devices. Background Art
[0002] In existing heating control systems, silicon-controlled rectifiers (SCRs) or solid-state relays (SSRs) are commonly used. Using a PID algorithm, they adjust the power to the heating element to achieve temperature regulation. In existing lighting control systems, particularly those requiring precise dimming and energy savings, zero-crossing trigger solid-state relays are widely used to reduce current surges and extend lamp life.
[0003] Thyristor rectifiers can be controlled using two control methods: phase angle control and frequency division control (zero-crossing control). Phase angle control determines when the thyristor rectifier turns on by controlling the conduction phase angle during each power cycle, while frequency division control determines whether the output is on or off during each power cycle. Phase angle control offers the advantage of continuous output, while frequency division control offers the advantage of low harmonics and minimal interference with the power grid. Thyristor rectifiers typically have a DIP switch to switch between these two control methods.
[0004] Solid-state relays can be controlled using three control methods: zero-crossing triggering, cycle control, and phase angle control. Zero-crossing triggering turns on when the AC voltage waveform passes through zero. Cycle control turns the solid-state relay on or off within multiple complete AC cycles. Phase angle control controls the conduction phase angle within each power cycle to determine when the solid-state relay turns on. Only one control method can be selected when selecting a solid-state relay. Zero-crossing triggering solid-state relays are usually the cheapest and are suitable for applications with limited budgets and low control accuracy requirements. Cycle-controlled solid-state relays are slightly more expensive than zero-crossing triggering and are suitable for applications requiring medium control accuracy and high-power loads. Phase-angle controlled solid-state relays are usually the most expensive and are suitable for applications requiring high-precision control and fast response.
[0005] Compared with silicon controlled rectifiers, zero-crossing triggered solid-state relays have obvious price advantages.
[0006] Because zero-crossing trigger solid-state relays must wait for the AC power line to cross zero, and their on / off response time is typically 0.5 power cycle (20ms for a 50Hz power cycle), their switching frequency for AC loads generally cannot exceed 10Hz. The higher the switching frequency of the solid-state relay, the more severe the heat generation. When heat dissipation conditions are not met, the failure rate is relatively high. To reduce the failure rate of solid-state relays, the rated switching frequency of existing zero-crossing trigger solid-state relays is typically between 1Hz and 2Hz.
[0007] Based on the above limitations, zero-crossing triggered solid-state relays are generally only suitable for low-power heating systems or occasions with low control accuracy requirements.
[0008] To achieve relatively high control accuracy, increasing the switching frequency of zero-crossing triggered solid-state relays is often used. However, as the switching frequency increases, the heat generated by the solid-state relay increases, which can lead to an increase in the failure rate of the solid-state relay. To overcome the shortcomings of existing technologies, there are generally two ways to improve. The first is to use enhanced cooling. In addition to being installed on a heat sink, the solid-state relay also needs to add a cooling fan. However, if the cooling fan fails to operate due to a fault, the solid-state relay may be damaged by overheating. The second way is to increase the margin when selecting the solid-state relay. For resistive loads (such as heaters), the rated current of the solid-state relay is generally selected as 1.2-1.5 times the load current, and sometimes even increased to about 2 times. Summary of the Invention
[0009] The Summary of the Invention introduces a series of simplified concepts, which are simplifications of existing technologies in the field and are further described in detail in the Detailed Description of the Invention. The Summary of the Invention is not intended to define the key features and essential features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.
[0010] The technical problem to be solved by the present invention is to provide a zero-crossing triggered solid-state relay control method and system, which improves its control accuracy by shortening the conduction period of the entire solid-state relay combination by using multiple solid-state relays in combination without increasing the switching frequency of a single solid-state relay, so that a heating system (or lighting system) driven by a solid-state relay can obtain a control accuracy close to or even equivalent to that of a heating system (or lighting system) driven by a thyristor rectifier.
[0011] To solve the above technical problems, the present invention provides a zero-crossing triggered solid-state relay control method for controlling a heating element, comprising:
[0012] The heating elements are divided into multiple groups, and each group of heating elements is controlled by a solid-state relay;
[0013] The original PWM signal is given to the first solid-state relay, and then the original PWM signal is phase-shifted for the first time and given to the second solid-state relay. Similarly, the original PWM signal is phase-shifted for the n-1th time and given to the nth solid-state relay. The phase difference of each phase shift is equal and evenly distributed within one conduction cycle. n is the number of solid-state relays.
[0014] The zero-crossing trigger solid-state relay control system provided by the present invention is used to control a heating element, comprising:
[0015] The heating elements are divided into multiple groups, and each group of heating elements is controlled by a solid-state relay;
[0016] A controller generates an original PWM signal for controlling the solid-state relays based on a temperature set value and a temperature sensor signal, and assigns the original PWM signal to the first solid-state relay. The original PWM signal is then phase-shifted for the first time and assigned to the second solid-state relay. Similarly, the original PWM signal is phase-shifted for the n-1th time and assigned to the nth solid-state relay. The phase difference of each phase shift is equal and evenly distributed within one conduction period, where n is the number of solid-state relays.
[0017] The power supply is connected to the solid-state relay via the circuit breaker and the contactor, and the solid-state relay controls the operation of the heating element.
[0018] Optionally, the controller of the zero-crossing triggered solid-state relay control system is a PID controller composed of a PLC.
[0019] The present invention provides a zero-crossing triggered solid-state relay control method for controlling a heating element or a lighting device, comprising:
[0020] Heating elements or lighting devices are controlled by multiple solid-state relays connected in parallel;
[0021] The pulse width assigned by the original PWM signal is changed to 1 / n of the original pulse width to obtain the execution PWM signal, where n is the number of solid-state relays;
[0022] The execution PWM signal is given to the first solid-state relay, and then the execution PWM signal is phase-shifted for the first time and given to the second solid-state relay. Similarly, the execution PWM signal is phase-shifted for the n-1th time and given to the nth solid-state relay. The phase difference of each phase shift is equal and evenly distributed within one conduction cycle.
[0023] The zero-crossing trigger solid-state relay control system provided by the present invention is used to control a heating element or a lighting device, comprising:
[0024] Heating elements or lighting devices are controlled by multiple solid-state relays connected in parallel;
[0025] The controller generates the original PWM signal for controlling the solid-state relays and converts the pulse width assigned by the original PWM signal into 1 / n of the original pulse width to obtain the execution PWM signal, where n is the number of solid-state relays;
[0026] It gives the execution PWM signal to the first solid-state relay, then performs the first phase shift on the execution PWM signal and gives it to the second solid-state relay, and so on, performs the n-1th phase shift on the execution PWM signal and gives it to the nth solid-state relay, and the phase difference of each phase shift is equal and evenly distributed within one conduction period;
[0027] The power supply is connected to each solid-state relay via a circuit breaker and a contactor, and each solid-state relay controls the operation of a heating element or a lighting device.
[0028] Optionally, when the zero-crossing triggered solid-state relay control system is used to control a heating element, the controller is a PID controller composed of a PLC, which generates an original PWM signal for controlling the solid-state relay based on the temperature setting value and the temperature sensor signal.
[0029] Optionally, when the zero-crossing triggered solid-state relay control system is used for lighting device control, the controller is a PLC controller.
[0030] The main design idea of the present invention is as follows: In heating control, if the heating elements can be grouped, the number of solid-state relays can be increased, and one solid-state relay controls a group of heating elements. All solid-state relays are not synchronously controlled by a PWM signal. Instead, the PWM signal is phase-shifted, and there is a phase difference between the PWM signals of each solid-state relay. In this way, when the heating elements are viewed as a whole, the frequency of conduction increases, but the power of each conduction is reduced. For the entire solid-state relay combination, the conduction period is reduced to 1 / n of the original (n is the number of solid-state relays). Another advantage of grouping the heating elements is that zero-crossing triggered solid-state relays can also be used in high-power heating systems.
[0031] In heating control, if heating elements cannot be grouped, or in lighting control, the number of solid-state relays can be increased and multiple SSRs can be used in parallel. Similarly, all SSRs are not controlled synchronously by a single PWM signal. Instead, the PWM signal is phase-shifted, with a phase difference between the PWM signals of each SSR. Because they are connected in parallel, the pulse width of each PWM signal is reduced to 1 / n of the original (n is the number of SSRs in parallel). Similarly, for the entire SSR combination, the on-time is reduced to 1 / n of the original.
[0032] As the conduction period decreases, the temperature control accuracy will be improved in heating control, and the uniformity of brightness control will also be improved in lighting control. However, the failure rate of the solid-state relay remains at the original level. Compared with the existing design, the present invention significantly reduces the cost in heating control compared to the existing design using a thyristor rectifier, improves the control accuracy compared to the existing design using a zero-crossing trigger solid-state relay, and the failure rate of the device remains at the original level. After adopting this solution, it can replace the design using a thyristor rectifier in most situations. In lighting control, compared with the existing design using a zero-crossing trigger solid-state relay, the dimming effect can be made smoother, flickering can be avoided, and the failure rate of the device remains at the original level. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The drawings herein are intended to illustrate the general characteristics of methods, structures, and / or materials used in certain exemplary embodiments of the present invention, supplementing the descriptions in the specification. However, the drawings herein are schematic diagrams not drawn to scale and may not accurately reflect the precise structure or performance characteristics of any given embodiment. The drawings herein should not be interpreted as defining or limiting the range of values or properties encompassed by the exemplary embodiments of the present invention. The present invention is further described in detail below in conjunction with the drawings and specific embodiments:
[0034] Figure 1 This is a circuit diagram of the present invention applied to groupable heating elements.
[0035] Figure 2 It is a schematic diagram of the phase shift of PWM signals applied to groupable heating elements according to the present invention.
[0036] Figure 3 This is a circuit diagram of the present invention applied to non-groupable heating elements.
[0037] Figure 4 This is a schematic diagram of a circuit in which the present invention is applied to a lighting fixture.
[0038] Figure 5 It is a schematic diagram of the PWM signal phase shifting of the present invention applied to non-groupable heating elements or lighting fixtures.
[0039] Description of reference numerals:
[0040] 1 is the circuit breaker
[0041] 2 is the contactor
[0042] 3 is PLC Q0.0 output (thyristor output type)
[0043] 4 is the first solid state relay
[0044] 5 is the second solid state relay
[0045] 6 is PLC Q0.1 output (thyristor output type)
[0046] 7 is the heating element
[0047] 8 is a lighting fixture. DETAILED DESCRIPTION
[0048] The following describes the embodiments of the present invention through specific embodiments. Those skilled in the art will fully understand the other advantages and technical effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments, and the details in this specification can be applied based on different perspectives and various modifications or changes can be made without departing from the overall design concept of the invention. It should be noted that the following embodiments and features therein can be combined with each other unless there is a conflict. The following exemplary embodiments of the present invention can be implemented in a variety of different forms and should not be construed as being limited to the specific embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete and to fully convey the technical solutions of these exemplary embodiments to those skilled in the art. It should be understood that when an element is referred to as being "connected" or "coupled" to another element, the element can be directly connected or coupled to the other element, or intervening elements can be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Throughout the drawings, the same reference numerals represent the same element. As used herein, the term "and / or" includes any and all combinations of one or more of the relevant listed items.
[0049] For ease of analysis, application scenarios are categorized into two types: those where heating elements can be grouped, and those where solid-state relays are connected in parallel. The former corresponds to heating control scenarios where heating elements can be grouped, while the latter applies to heating control scenarios where heating elements cannot be grouped, or lighting control scenarios. The following examples illustrate each of these scenarios.
[0050] First embodiment;
[0051] The present invention provides a zero-crossing trigger solid-state relay control method for controlling a heating element. This embodiment is used in situations where the heating elements can be grouped, and includes:
[0052] The heating elements are divided into multiple groups, and each group of heating elements is controlled by a solid-state relay;
[0053] The original PWM signal is given to the first solid-state relay, and then the original PWM signal is phase-shifted for the first time and given to the second solid-state relay. Similarly, the original PWM signal is phase-shifted for the n-1th time and given to the nth solid-state relay. The phase difference of each phase shift is equal and evenly distributed within one conduction cycle. n is the number of solid-state relays.
[0054] Second embodiment;
[0055] refer to Figure 1As shown, the present invention provides a zero-crossing trigger solid-state relay control system for controlling a heating element. This embodiment is used in situations where the heating elements can be grouped, and includes:
[0056] The heating elements are divided into multiple groups, and each group of heating elements is controlled by a solid-state relay;
[0057] A controller generates an original PWM signal for controlling the solid-state relays based on a temperature set value and a temperature sensor signal, and assigns the original PWM signal to the first solid-state relay. The original PWM signal is then phase-shifted for the first time and assigned to the second solid-state relay. Similarly, the original PWM signal is phase-shifted for the n-1th time and assigned to the nth solid-state relay. The phase difference of each phase shift is equal and evenly distributed within one conduction period, where n is the number of solid-state relays.
[0058] The controller is a PID controller (Proportional-Integral-Differential Controller) composed of a PLC (Programmable Logic Controller). It receives the temperature set value and the temperature sensor signal (feedback value), processes it through the PID algorithm, obtains a percentage output value (0-100%), and converts it into a PWM signal (called the original PWM signal);
[0059] The power supply is connected to the solid-state relay via the circuit breaker and the contactor, and the solid-state relay controls the operation of the heating element.
[0060] The principle is explained in detail using two solid-state relays as an example. The situation is similar for three or more solid-state relays. The heating element in the figure is a three-phase device. The situation is similar when the heating element is a single-phase device. Figure 2 As shown, the conduction period of the solid-state relay combination after phase shifting (the two solid-state relays are regarded as a whole) becomes 1 / 2 of the original period, and when the PID controller output is ≥50%, when all the grouped heating elements are regarded as a whole, current always flows.
[0061] Third embodiment;
[0062] The present invention provides a zero-crossing triggered solid-state relay control method for controlling a heating element or a lighting device. This embodiment is used when solid-state relays are connected in parallel, and includes:
[0063] The pulse width assigned by the original PWM signal is changed to 1 / n of the original pulse width to obtain the execution PWM signal, where n is the number of solid-state relays;
[0064] The execution PWM signal is given to the first solid-state relay, and then the execution PWM signal is phase-shifted for the first time and given to the second solid-state relay. Similarly, the execution PWM signal is phase-shifted for the n-1th time and given to the nth solid-state relay. The phase difference of each phase shift is equal and evenly distributed within one conduction cycle.
[0065] Fourth embodiment;
[0066] refer to Figure 3 、 Figure 4 As shown, the present invention provides a zero-crossing trigger solid-state relay control system for controlling a heating element or a lighting device. This embodiment is used when solid-state relays are connected in parallel, and includes:
[0067] The heating elements are controlled by multiple solid-state relays connected in parallel;
[0068] The controller generates the original PWM signal for controlling the solid-state relays and converts the pulse width assigned by the original PWM signal into 1 / n of the original pulse width to obtain the execution PWM signal, where n is the number of solid-state relays;
[0069] It assigns the execution PWM signal to the first solid-state relay, then performs the first phase shift on the execution PWM signal and assigns it to the second solid-state relay, and so on, performs the n-1th phase shift on the execution PWM signal and assigns it to the nth solid-state relay, and the phase difference of each phase shift is equal and evenly distributed within one conduction period;
[0070] The power supply is connected to each solid-state relay through a circuit breaker and a contactor, and each solid-state relay controls the operation of the heating element;
[0071] When the fourth embodiment is used for heating element control, the controller is a PID controller composed of a PLC, which generates an original PWM signal for controlling a solid-state relay based on a temperature setting value and a temperature sensor signal;
[0072] When the fourth embodiment is used for controlling lighting devices, the controller is a PLC controller.
[0073] The PWM signal output by the controller is processed as follows Figure 5 As shown, the total conduction time of the two parallel solid-state relays is equal to the conduction time of a single solid-state relay in the prior art, so the pulse width of the processed PWM signal is 1 / 2 of the original. Figure 5 As shown in the figure, the conduction period of the solid-state relay combination after phase shifting (the two solid-state relays are regarded as a whole) becomes 1 / 2 of the original period.
[0074] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will also be understood that, unless expressly defined herein, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, rather than being interpreted in an idealized or overly formal sense.
[0075] The present invention has been described in detail above by way of specific embodiments and examples, but these do not constitute limitations of the present invention. Without departing from the principles of the present invention, those skilled in the art may make many variations and improvements, which should also be considered within the scope of protection of the present invention.
Claims
1. A zero-crossing trigger solid-state relay control method for controlling a heating element, characterized in that: include: The heating elements are divided into multiple groups, and each group of heating elements is controlled by a solid-state relay; The original PWM signal is given to the first solid-state relay, and then the original PWM signal is phase-shifted for the first time and given to the second solid-state relay. Similarly, the original PWM signal is phase-shifted for the n-1th time and given to the nth solid-state relay. The phase difference of each phase shift is equal and evenly distributed within one conduction cycle. n is the number of solid-state relays.
2. A zero-crossing trigger solid-state relay control system for controlling a heating element, characterized in that: include: The heating elements are divided into multiple groups, and each group of heating elements is controlled by a solid-state relay; A controller generates an original PWM signal for controlling the solid-state relays based on a temperature set value and a temperature sensor signal, and assigns the original PWM signal to the first solid-state relay. The original PWM signal is then phase-shifted for the first time and assigned to the second solid-state relay. Similarly, the original PWM signal is phase-shifted for the n-1th time and assigned to the nth solid-state relay. The phase difference of each phase shift is equal and evenly distributed within one conduction period, where n is the number of solid-state relays. The power supply is connected to the solid-state relay via the circuit breaker and the contactor, and the solid-state relay controls the operation of the heating element.
3. The zero-crossing triggered solid-state relay control system according to claim 2, wherein: The controller is a PID controller composed of PLC.
4. A zero-crossing trigger solid-state relay control method for controlling a heating element or a lighting device, characterized in that: include: Heating elements or lighting devices are controlled by multiple solid-state relays connected in parallel; The pulse width assigned by the original PWM signal is changed to 1 / n of the original pulse width to obtain the execution PWM signal, where n is the number of solid-state relays; The execution PWM signal is given to the first solid-state relay, and then the execution PWM signal is phase-shifted for the first time and given to the second solid-state relay. Similarly, the execution PWM signal is phase-shifted for the n-1th time and given to the nth solid-state relay. The phase difference of each phase shift is equal and evenly distributed within one conduction cycle.
5. A zero-crossing trigger solid-state relay control system for controlling a heating element or a lighting device, characterized in that: include: Heating elements or lighting devices are controlled by multiple solid-state relays connected in parallel; The controller generates the original PWM signal for controlling the solid-state relays and converts the pulse width assigned by the original PWM signal into 1 / n of the original pulse width to obtain the execution PWM signal, where n is the number of solid-state relays; It gives the execution PWM signal to the first solid-state relay, then performs the first phase shift on the execution PWM signal and gives it to the second solid-state relay, and so on, the execution PWM signal performs the n-1th phase shift and gives it to the nth solid-state relay, and the phase difference of each phase shift is equal and evenly distributed within one conduction cycle; The power supply is connected to each solid-state relay via a circuit breaker and a contactor, and each solid-state relay controls the operation of a heating element or a lighting device.
6. The zero-crossing triggered solid-state relay control system according to claim 5, characterized in that: When it is used for heating element control, the controller is a PID controller composed of a PLC, which generates an original PWM signal for controlling the solid-state relay based on the temperature setting value and the temperature sensor signal.
7. The zero-crossing triggered solid-state relay control system according to claim 5, characterized in that: When it is used for lighting device control, the controller is a PLC controller.