A relay group zero-crossing activation and deactivation control circuit

Abstract

This utility model relates to the field of relay control in commercial cooking equipment, specifically a relay group zero-crossing engagement and release control circuit. Control chip U1 is connected to the power supply circuit; relay management chip U2 drives the relay group; the power supply circuit detects the zero-crossing point of the mains power through optocoupler U3. Using the falling edge of the zero-crossing signal as a reference, the action time window is predicted, ensuring the relay contacts precisely engage / release at the zero-crossing point. Actual measurements show a 90% reduction in arc energy. Upon load startup, both the first relay RL1 and the fifth relay RL5 are simultaneously engaged; one relay is initially disengaged and its number recorded; the other relay is disengaged again and its record is updated, repeating this cycle to balance contact wear. By precisely controlling the relay contacts to engage and release at the mains power zero-crossing point, the arc generated during contact disconnection is effectively reduced, balancing the number of actions of a single relay and contact wear.

Description

Technical Field

[0001] This utility model relates to the field of high-power load switch control technology, and in particular to a relay group zero-crossing activation and release control circuit for commercial cooking equipment. Background Technology

[0002] In the field of high-power load control for commercial cooking equipment, relays, as core switching components, directly determine the reliability of the equipment. Current mainstream technologies have the following limitations.

[0003] I. Single relay zero-crossing control scheme: By performing switching operations at the zero-crossing point of the mains power, the arc energy is reduced. However, under resistive loads above 10A and high temperature environments of 60℃, the measured contact arc energy still reaches 80-120mJ / cycle, which means that the relay life is usually no more than 100,000 cycles (refer to industry test report: GB / T 14598.1-2020).

[0004] II. Parallel non-rotating dual-relay scheme: Although it can share the current load, due to the lack of a mechanism to balance the number of operations, a single relay still bears the main switching stress. Actual tests show that under the same operating conditions, the overall system lifespan is only increased to 120,000-150,000 cycles, and there is a risk of early failure due to uneven relay wear.

[0005] III. Thyristor-assisted relay solution: Thyristors are used to achieve pre-conduction to suppress arcing, but the power consumption of thyristors is significant in high-temperature environments (typical temperature rise ≥40℃), which leads to a decrease in system reliability and an increase in cost of 40%-60%.

[0006] The above solutions are insufficient to meet the stringent operating conditions of commercial cooking equipment, which requires more than 300 on / off cycles per day, ambient temperatures above 60°C, and currents above 10A. Innovative solutions are urgently needed. Summary of the Invention

[0007] This invention aims to solve at least one of the technical problems existing in the prior art. Therefore, one objective of this invention is to provide a relay group zero-crossing activation and deactivation control circuit that can significantly extend relay life, reduce control circuit costs, improve reliability in high-temperature environments, and enhance safety compliance.

[0008] This utility model also provides a relay group zero-crossing activation and deactivation control circuit, including: The control chip U1 has its pin 1 connected to the power supply circuit; Relay management chip U2 is connected to control chip U1 and drives the relay group; Power supply circuit: includes optocoupler U3. The first pin of optocoupler U3 is connected to the ACL terminal, the second pin is connected to the ACN terminal, the first pin and the second pin are connected in parallel with diode D2, the fourth pin is connected to the GL terminal through the fifth resistor R5, and the third pin is grounded through the second capacitor C2. Relay group: includes first relay RL1 to fifth relay RL5, wherein first relay RL1 and fifth relay RL5 perform alternating on / off control, and fifth relay RL5 is the main load switch relay; the second pin of fifth relay RL5 is connected to the ACN terminal via the fifth plug-in CP5; The first pin of the fifth relay RL5 is connected to the sixth plug-in CP6 through the ninth plug-in CP9 respectively. Load circuit: includes heating element group, the common terminal of the heating element group is connected to the fifth terminal CN5 to the eighth terminal CN8; one end of the heating element group is connected to the first terminal CN1 to the fourth terminal CN4 respectively, which are connected to the corresponding relays.

[0009] Specifically, the contacts of the total load switch relay RL5 are connected in series in the ACN terminal of the load power supply circuit to achieve physical power disconnection to meet safety requirements.

[0010] Specifically, the eighth and ninth pins of the relay management chip U2 are connected to a +12V power supply terminal via capacitor C1, and the eighth pin is connected to a ground terminal GND.

[0011] Furthermore, the relay group also includes a third relay RL3, which is connected to the relay management chip U2.

[0012] Furthermore, the relay group also includes a fourth relay RL4, which is connected to the relay management chip U2.

[0013] Specifically, the first pin of the optocoupler U3 is connected to the ACL terminal by a first resistor R1, a second resistor R2 and a third resistor R3 in sequence.

[0014] Specifically, the common terminal between the fourth pin of the optocoupler U3 and the fifth resistor R5 is connected to a fourth resistor R4, and the fourth resistor R4 is connected to a +5V terminal.

[0015] This utility model achieves significant improvements through the above-mentioned technical means, with the following specific beneficial effects: I. Significantly Extended Relay Life: By precisely controlling the relay contacts to engage and disengage at the zero-crossing point of the mains power, the arc generated during contact disconnection is effectively reduced (measured arc energy reduction of approximately 90%). Simultaneously, the mechanism of dual relays taking turns handling load switching balances the number of operations and contact wear of a single relay. Actual measurements show that, under the same load conditions, the overall lifespan of the relays using this scheme is approximately 2.3 times that of a single-relay scheme (measured cycle count > 200,000 cycles).

[0016] II. Reduced Control Circuit Costs: The zero-crossing control and dual-relay switching mechanism significantly reduce the arc stress and switching frequency experienced by individual relay contacts, making it possible to use ordinary relays with lower rated current specifications (e.g., replacing the original 16A with a 10A relay). Compared to the original design, this solution can reduce relay selection costs by approximately 40%.

[0017] III. Improved reliability in high-temperature environments: In a constant temperature environment test at 60℃, the continuous working life of the relay control circuit using this solution was increased by approximately 200% compared to the control circuit without this solution, significantly improving the long-term operational stability and reliability of commercial cooking equipment under high-temperature conditions.

[0018] IV. Enhanced Safety Compliance: In the control circuit design, the contacts of the main load switch relay RL5 are connected in series with the neutral line ACN or the phase line of the load power supply circuit, achieving physical power isolation of the load. This design complies with the relevant requirements of the International Electrotechnical Commission's safety standard for household and similar electrical appliances (IEC 60335), ensuring the safe use of the product. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings.

[0020] Figure 1 This is a circuit diagram showing the connection between the control chip U1 and the relay management chip U2 of this utility model.

[0021] Figure 2 This is the power supply circuit diagram of this utility model.

[0022] Figure 3 This is a schematic diagram of the connection between the relay group and the load circuit of this utility model.

[0023] Figure 4 This is the working logic diagram of the first relay RL1 and the fifth relay RL5 of this utility model. Detailed Implementation

[0024] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0025] The following is for reference. Figures 1 to 4 A control circuit for a relay group zero-crossing activation and deactivation control method according to an embodiment of the present invention is described, comprising: The control chip U1 has its pin 1 connected to the power supply circuit; Relay management chip U2 is connected to control chip U1 and drives the relay group; Power supply circuit: includes optocoupler U3. The first pin of optocoupler U3 is connected to the ACL terminal, the second pin is connected to the ACN terminal, the first pin and the second pin are connected in parallel with diode D2, the fourth pin is connected to the GL terminal through the fifth resistor R5, and the third pin is grounded through the second capacitor C2. Relay group: includes first relay RL1 to fifth relay RL5, wherein first relay RL1 and fifth relay RL5 perform alternating on / off control, and fifth relay RL5 is the main load switch relay; the second pin of fifth relay RL5 is connected to the ACN terminal via fifth plug CP5; the first pin of fifth relay RL5 is connected to sixth plug CP6 to ninth plug CP9 respectively. Load circuit: includes heating element group, the common terminal of the heating element group is connected to the fifth terminal CN5 to the eighth terminal CN8; one end of the heating element group is connected to the first terminal CN1 to the fourth terminal CN4 respectively, which are connected to the corresponding relays.

[0026] Specifically, the contacts of the main load switch relay RL5 are connected in series in the ACN terminal of the load power supply circuit to achieve physical power disconnection to meet safety requirements. The eighth and ninth pins of the relay management chip U2 are connected to a +12V power supply terminal via capacitor C1, and the eighth pin is connected to the ground terminal GND. The relay group also includes a third relay RL3, which is connected to the relay management chip U2. The relay group also includes a fourth relay RL4, which is connected to the relay management chip U2. A first resistor R1, a second resistor R2, and a third resistor R3 are sequentially connected between the first pin and the ACL terminal of the optocoupler U3. The total resistance of the first resistor R1, the second resistor R2, and the third resistor R3 is 200kΩ ± 10%.

[0027] Specifically, the common terminal between the fourth pin of the optocoupler U3 and the fifth resistor R5 is connected to a fourth resistor R4, and the fourth resistor R4 is connected to a +5V terminal.

[0028] This utility model applies the control method of the above-mentioned relay group zero-crossing activation and release control circuit, including the following steps: The zero-crossing point of the mains power is detected, and the falling edge of the zero-crossing signal is used as the zero-crossing reference time point; Based on the time difference between the relay's activation and deactivation, predict the time window for the next zero-crossing point; The control relay performs an engaging or disengaging action within the time window, ensuring that the contact action precisely lands at the zero-crossing point of the mains power. The load is switched on and off using dual relays in turn. When the load starts, the first relay RL1 and the fifth relay RL5 are activated simultaneously. When the load is first disconnected, release one of the relays and record its number; When the load is disconnected again, release another relay that was not released in the previous round and update the record number; The above-mentioned turn-on release logic is then executed repeatedly during subsequent load switching cycles.

[0029] Specifically, in single-phase applications, the fifth relay RL5 controls the load live wire ACL, and the first relay RL1 controls the load neutral wire ACN; in two-phase applications, the first relay RL1 controls the first phase wire L1, and the fifth relay RL5 controls the second phase wire L2.

[0030] Specifically, zero-crossing detection is achieved through optocoupler U3. Its input is connected to the mains power line ACL via first resistor R1, second resistor R2, and third resistor R3. Its output is grounded via filter capacitor C2 to generate a zero-crossing signal, which is then transmitted to the input pin of control chip U1.

[0031] To achieve the above-mentioned utility model content, the present utility model adopts the following specific technical solution: The capture of the zero-crossing point of the mains power is based on the different activation and release times of the relay group, including the possible action time of the control relay group, to calculate the pre-activation and release time so that the relay group is activated and released just at the zero-crossing point. The zero-crossing engagement and release logic must take into account the application of the product on 50Hz / 60Hz mains power, and also consider that the relay group can engage and release even when there is no zero-crossing input signal or when the zero-crossing signal is interfered with (fault). During cooking, the relay management chip U2 controls all relays from RL1 to RL5 to be engaged for the load to operate. Disengaging any one relay stops the load output. Therefore, with single-phase power, the relay group controls the L and N terminals of the load separately. With two-phase power, the relay group controls the L1 and L2 terminals of the load separately. When the cooking load is operating, both RL1 and RL5 are engaged. When the cooking operation indicates temporary load disconnection, RL1 is released (remember the relay number released in this cycle). When the load resumes operation, RL1 is closed. When the load needs to be disconnected again, the other relay (RL5) is disconnected (remember the relay number released in this cycle). When the load resumes operation, RL5 is closed again. Disconnecting the load again disconnects the other relay (RL1), and so on, with the relays engaging and disengaging in turn.

[0032] like Figure 4 As shown, firstly, when the load output changes, one load output is activated, and then the first relay RL1 and the fifth relay RL5 are activated. Secondly, when the load is disconnected, the relay sequence number that was previously disconnected is split into two paths: the fifth relay RL5 is activated, and the first relay RL1 is deactivated; the first relay RL1 is activated, and the fifth relay RL5 is deactivated. It is necessary to perform activation and deactivation actions for the relay group in both closed and open states, requiring precise timing and monitoring of the real-time zero-crossing state of the mains power.

[0033] This circuit utilizes a zero-crossing signal to pre-engage and release relays, ensuring that the relay group's engagement and release actions coincide with the zero-crossing point of the mains power. The zero-crossing signal is detected via a level input; the falling edge is selected as the zero-crossing reference time point. Then, after this zero-crossing falling edge (the "zero-crossing reference time point"), and before the predicted time difference (distinguishing between 50Hz and 60Hz) for the next zero-crossing point, the circuit controls the engagement and release of the relays. This ensures that the corresponding relays' engagement and release actions coincide with the zero-crossing point. During implementation, adjustments and optimizations can be made based on actual conditions to achieve the best technical results.

[0034] The zero-crossing pull-in and release technology of the first relay RL1 and the fifth relay RL5: It not only utilizes the advantages of the zero-crossing pull-in and release relay, but also uses the dual relay control to take turns operating to achieve "1+1>2" to increase the relay's operating life and achieve the expected effect. Among them: the zero-crossing detection pre-engages and releases the relay, and the first relay RL1 and the fifth relay RL5 operate alternately to release; Commercial microwave ovens or ovens are characterized by: a load current of nearly 10A or more, high power, high operating temperature, long operating time, and high switching frequency of controlled components.

[0035] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A relay bank zero-crossing pick-up release control circuit, characterized by, include: The control chip U1 has its pin 1 connected to the power supply circuit; Relay management chip U2 is connected to control chip U1 and drives the relay group; Power supply circuit: includes optocoupler U3. The first pin of optocoupler U3 is connected to the ACL terminal, the second pin is connected to the ACN terminal, the first pin and the second pin are connected in parallel with diode D2, the fourth pin is connected to the GL terminal through the fifth resistor R5, and the third pin is grounded through the second capacitor C2. Relay group: includes first relay RL1 to fifth relay RL5, wherein first relay RL1 and fifth relay RL5 perform alternating on / off control, and fifth relay RL5 is the main load switch relay; the second pin of fifth relay RL5 is connected to the ACN terminal via the fifth plug-in CP5; The first pin of the fifth relay RL5 is connected to the sixth plug-in CP6 through the ninth plug-in CP9 respectively; Load circuit: includes heating element group, the common terminal of the heating element group is connected to the fifth terminal CN5 to the eighth terminal CN8; one end of the heating element group is connected to the first terminal CN1 to the fourth terminal CN4 respectively, which are connected to the corresponding relays.

2. A relay bank zero-crossing pull-in release control circuit according to claim 1, characterized in that: The contacts of the total load switch relay RL5 are connected in series in the ACN terminal of the load power supply circuit to achieve physical power disconnection to meet safety requirements.

3. A relay bank zero-crossing pull-in release control circuit as claimed in claim 1, wherein: The eighth and ninth pins of the relay management chip U2 are connected to a +12V power supply via capacitor C1, and the eighth pin is connected to the ground terminal GND.

4. A relay bank zero-crossing pull-in release control circuit as claimed in claim 1, wherein: The relay group also includes a third relay RL3, which is connected to the relay management chip U2.

5. A relay bank zero-crossing pull-in release control circuit as claimed in claim 1, wherein: The relay group also includes a fourth relay RL4, which is connected to the relay management chip U2.

6. A relay bank zero-crossing attract-release control circuit as defined in claim 1 wherein: The first pin of the optocoupler U3 is connected to the ACL terminal by a first resistor R1, a second resistor R2, and a third resistor R3 in sequence.

7. A relay bank zero-crossing attract-release control circuit as defined in claim 4 wherein: The common terminal between the fourth pin of the optocoupler U3 and the fifth resistor R5 is connected to the fourth resistor R4, and the fourth resistor R4 is connected to the +5V terminal.

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