Zero-crossing pull-in and release control circuit of relay set and control method thereof

Abstract

The invention relates to the field of commercial cooking equipment relay control, in particular to a relay set zero-crossing pull-in and release control circuit and a control method thereof. In the control circuit, a control chip U1 is connected with a power supply circuit; the relay management chip U2 drives the relay group; the power supply circuit detects a mains supply zero crossing point through the photoelectric coupler U3. A zero-crossing signal falling edge is taken as a reference, an action time window is pre-judged, relay contacts are accurately attracted / released at a zero-crossing point, and when actually measured arc energy is reduced by 90% and a load is started, a first relay RL1 and a fifth relay RL5 are attracted at the same time; releasing the first disconnection and recording the serial number; and the other relay is disconnected and released again, the record is updated, and the execution is cyclically performed to balance the contact loss. Wherein the relay contacts are accurately controlled to execute pull-in and release actions at the mains supply zero crossing point, so that electric arcs generated when the contacts are broken are effectively reduced, and the action times and the contact loss of a single relay are balanced.

Description

Technical Field

[0001] The present invention relates to the technical field of high-power load switch control, and particularly to a zero-crossing suction and release control circuit for a relay group applied to commercial cooking equipment and a control method therefor. Background Art

[0002] In the field of high-power load control of commercial cooking equipment, the relay is the core switching element, and its lifespan directly determines the reliability of the equipment. The current mainstream technologies have the following limitations.

[0003] I. Single-relay zero-crossing control scheme: By performing on-off operations at the zero-crossing point of the mains power to reduce the arc energy. However, in a resistive load above 10 A and a high-temperature environment of 60 °C, the measured arc energy at the contact is still 80 - 120 mJ per time, resulting in a relay lifespan usually not exceeding 100,000 cycles (reference: industry test report: GB / T 14598.1 - 2020).

[0004] II. Double-relay parallel non-rotation scheme: Although it can share the current load, due to the lack of an action count balancing mechanism, a single relay still bears the main on-off stress. Measurements show that under the same operating conditions, the overall lifespan of the system is only increased to 120,000 - 150,000 times, and there is a risk of early failure due to uneven relay losses.

[0005] III. Thyristor-assisted relay scheme: Using a thyristor to achieve pre-conduction to suppress the arc. However, the thyristor has a significant self-power consumption in a high-temperature environment (typical temperature rise ≥ 40 °C), resulting in a decrease in system reliability and a 40% - 60% increase in cost.

[0006] The above schemes are difficult to meet the stringent operating conditions of commercial cooking equipment, such as over 300 on-off operations per day, an ambient temperature above 60 °C, and a current above 10 A. There is an urgent need for innovative solutions. Summary of the Invention

[0007] The present invention aims to at least solve one of the technical problems existing in the prior art. For this reason, an object of the present invention is to provide a zero-crossing suction and release control circuit and control method for a relay group, which can significantly extend the relay lifespan, reduce the cost of the control circuit, improve the reliability in a high-temperature environment, and enhance safety and compliance.

[0008] The present invention provides a zero-crossing suction and release control circuit for a relay group, including the following.

[0009] A control chip U1, whose pin 1 is connected to the power supply circuit.

[0010] A relay management chip U2, connected to the control chip U1 and driving the relay group.

[0011] Power supply circuit: It includes an optocoupler U3. The first pin of the optocoupler U3 is connected to the ACL terminal, the second pin is connected to the ACN terminal. A diode D2 is connected in parallel between the first pin and the second pin. The fourth pin is connected to the GL terminal via a fifth resistor R5, and the third pin is grounded via a second capacitor C2.

[0012] Relay group: It includes a first relay RL1 to a fifth relay RL5. Among them, the first relay RL1 and the fifth relay RL5 perform alternating on-off control, and the fifth relay RL5 is the main load switch relay. The second pin of the fifth relay RL5 is connected to the ACN terminal via a fifth insert CP5, and the first pin of the fifth relay RL5 is respectively connected to a sixth insert CP6 to a ninth insert CP9.

[0013] Load circuit: It includes an invention tube group. The common terminal of the heating tube group is connected to a fifth socket CN5 to an eighth socket CN8. One end of the heating tube group is respectively connected to a first socket CN1 to a fourth socket CN4 to connect to the corresponding relay.

[0014] Specifically further, the contact of the main load switch relay RL5 is connected in series in the ACN terminal of the load power supply circuit to achieve physical power-off to meet the safety regulations requirements.

[0015] Specifically further, the eighth pin and the ninth pin of the relay management chip U2 are connected to the +12V power supply terminal via a capacitor C1, and the eighth pin is connected to the ground terminal GND.

[0016] Specifically further, the relay group further includes a third relay RL3, and the third relay RL3 is connected to the relay management chip U2.

[0017] Specifically further, the relay group further includes a fourth relay RL4, and the fourth relay RL4 is connected to the relay management chip U2.

[0018] Specifically further, a first resistor R1, a second resistor R2, and a third resistor R3 are sequentially connected between the first pin of the optocoupler U3 and the ACL terminal.

[0019] Specifically further, a fourth resistor R4 is connected to the common terminal between the fourth pin of the optocoupler U3 and the fifth resistor R5, and the fourth resistor R4 is connected to the +5V terminal.

[0020] The present invention also discloses a control method for the zero-crossing suction and release control circuit of the relay group according to any of the above technical solutions, which includes the following steps.

[0021] Detect the zero-crossing point of the mains electricity, and use the falling edge of the zero-crossing signal as the zero-crossing reference time point.

[0022] Predict the time window of the next zero-crossing point based on the difference in the pull-in / release action time of the relay.

[0023] Control the relay to perform a pull-in or release action within the time window, so that the contact action precisely steps on the zero-crossing point of the mains power.

[0024] Adopt a mechanism of alternately controlling the on / off of the load by two relays, specifically as follows.

[0025] When the load starts, simultaneously pull in the first relay RL1 and the fifth relay RL5.

[0026] When the load is first disconnected, release one of the relays and record its number.

[0027] When the load is disconnected again, release the other relay that was not released in the previous round and update the recorded number.

[0028] Subsequent on / off cycles of the load repeatedly execute the above-mentioned alternate release logic.

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

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

[0031] The present invention is significantly improved through the above technical means, and specifically has the following beneficial effects.

[0032] 1. Significantly extend the relay life: By precisely controlling the relay contacts to perform pull-in and release actions at the zero-crossing point of the mains power, the arc generated during contact breaking is effectively reduced (the measured arc energy is reduced by about 90%). At the same time, the mechanism of alternately undertaking the on / off tasks of the load by two relays balances the action times and contact losses of a single relay. Measurements show that under the same load conditions, the overall service life of the relay in this solution reaches about 2.3 times that of the single-relay solution (the measured cycle times > 200,000 times).

[0033] 2. Reduce the cost of the control circuit: Since the zero-crossing control and the two-relay rotation mechanism significantly reduce the arc stress and on / off times borne by a single relay contact, it becomes possible to select a common relay with a lower rated current specification (for example, replacing the original 16A specification with a 10A specification). Compared with the original design, this solution can reduce the relay selection cost by about 40%.

[0034] III. Improving reliability in high-temperature environments: In the constant-temperature environment test at 60°C, the continuous working life of the relay control circuit applying this solution is increased by approximately 200% compared to the control circuit without adopting this solution, significantly improving the long-term operation stability and reliability of commercial cooking equipment under high-temperature conditions.

[0035] IV. Enhancing safety and compliance: In the control circuit design, the contacts of the main load switch relay RL5 are connected in series in the neutral wire ACN or the phase wire of the load power supply circuit, achieving physical power-off isolation of the load. This design meets the relevant requirements of the safety standard (IEC 60335) for household and similar electrical appliances of the International Electrotechnical Commission, ensuring the safe use of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings.

[0037] Figure 1 is the circuit diagram of the connection between the control chip U1 and the relay management chip U2 of the present invention.

[0038] Figure 2 is the power supply circuit diagram of the present invention.

[0039] Figure 3 is the schematic diagram of the connection between the relay group and the load circuit of the present invention.

[0040] Figure 4 is the working logic diagram of the first relay RL1 and the fifth relay RL5 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described by referring to the drawings below are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0042] Reference will be made below to Figures 1 to 4 Describe a zero-crossing suction and release control circuit for a relay group according to an embodiment of the present invention, including the following.

[0043] A control chip U1, whose pin 1 is connected to the power supply circuit.

[0044] A relay management chip U2, connected to the control chip U1 and driving the relay group.

[0045] Power supply circuit: It includes an optocoupler U3. The first pin of the optocoupler U3 is connected to the ACL terminal, the second pin is connected to the ACN terminal, a diode D2 is connected in parallel between the first pin and the second pin, the fourth pin is connected to the GL terminal via a fifth resistor R5, and the third pin is grounded via a second capacitor C2.

[0046] Relay group: It includes a first relay RL1 to a fifth relay RL5. Among them, the first relay RL1 and the fifth relay RL5 perform alternate on-off control, and the fifth relay RL5 is the main load switch relay; the second pin of the fifth relay RL5 is connected to the ACN terminal via a fifth insert CP5; the first pin of the fifth relay RL5 is respectively connected to a sixth insert CP6 to a ninth insert CP9.

[0047] Load circuit: It includes a heating tube group. The common terminal of the heating tube group is connected to a fifth socket CN5 to an eighth socket CN8; one end of the heating tube group is respectively connected to a first socket CN1 to a fourth socket CN4 to connect to the corresponding relay.

[0048] Specifically further, the contact of the main load switch relay RL5 is connected in series in the ACN terminal of the load power supply circuit to achieve physical power-off to meet the safety regulations requirements. The eighth pin and the ninth pin of the relay management chip U2 are connected to the +12V power supply terminal via a capacitor C1, and the eighth pin is connected to the ground terminal GND. The relay group also includes a third relay RL3, and the third relay RL3 is connected to the relay management chip U2. The relay group also includes a fourth relay RL4, and the fourth relay RL4 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 of the optocoupler U3 and the ACL terminal. The total resistance value of the first resistor R1, the second resistor R2, and the third resistor R3 is 200kΩ ± 10%.

[0049] Specifically further, a fourth resistor R4 is connected to the common terminal between the fourth pin of the optocoupler U3 and the fifth resistor R5, and the fourth resistor R4 is connected to the +5V terminal.

[0050] For the above zero-crossing on / off control circuit of the relay group, the control method adopted includes the following steps.

[0051] Detect the zero-crossing point of the mains electricity, and use the falling edge of the zero-crossing signal as the zero-crossing reference time point.

[0052] According to the on / off action time difference of the relay, predict the time window of the next zero-crossing point.

[0053] Control the relay to perform the on / off action within the time window, so that the contact action precisely steps on the zero-crossing point of the mains electricity.

[0054] The load is controlled to be turned on and off by two relays taking turns, as follows.

[0055] When the load starts, the first relay RL1 and the fifth relay RL5 are simultaneously energized.

[0056] When the load is first turned off, one of the relays is released and its number is recorded.

[0057] When the load is turned off again, the other relay that was not released in the previous round is released and the recorded number is updated.

[0058] Subsequently, the above-mentioned alternating release logic is cyclically executed for the load on and off.

[0059] Specifically further, in the application of single-phase electricity, the fifth relay RL5 controls the live wire ACL of the load, and the first relay RL1 controls the neutral wire ACN of the load; in the application of two-phase electricity, the first relay RL1 controls the first phase line L1, and the fifth relay RL5 controls the second phase line L2.

[0060] Specifically further, the zero-crossing detection is realized through the optocoupler U3. Its input terminal is connected to the mains live wire ACL through the first resistor R1, the second resistor R2, and the third resistor R3. The output terminal is grounded through the filter capacitor C2 to generate a zero-crossing signal, which is transmitted to the input pin of the control chip U1.

[0061] In order to achieve the above-mentioned invention content, the present invention adopts the following specific technical solutions.

[0062] Capture of the mains zero-crossing point. According to the different on and off times of the relay group, including the possible action times of the control relay group, calculate the pre-on and off times so that the relay group just releases and energizes on the zero-crossing point.

[0063] The zero-crossing on and off logic processing must take into account the application of the product on 50Hz / 60Hz mains electricity, and consider that the relay group can also perform on and off actions when there is no zero-crossing input signal or when the zero-crossing signal is interfered (faulty).

[0064] During cooking, the relay management chip U2 controls the first relay RL1 to the fifth relay RL5 to all be attracted for the load to work. Only when any relay is released will the load output stop. Therefore, when using single-phase electricity, the relay group separately controls the connection of the L terminal and the N terminal of the load. When using two-phase electricity, the relay group separately controls the L1 terminal and the L2 terminal of the load. When the cooking load is operating, the first relay RL1 and the fifth relay RL5 are both attracted. When the cooking operation indicator temporarily disconnects the load, at this time, release the first relay RL1 (remember the relay number released in this round). When the load runs again, close the original first relay RL1. When it is necessary to disconnect the load again, at this time, disconnect the other fifth relay RL5 except the one that was disconnected last time (remember the relay number released in this round). When the load runs again, close the fifth relay RL5 back. When disconnecting the load again, disconnect the other first relay RL1 except the one that was disconnected last time, and so on, alternately attracting and releasing the relays.

[0065] As Figure 4 shown, first, when the load output changes, there is a load output, and then the first relay RL1 and the fifth relay RL5 are attracted. Second, when the load is disconnected, according to the serial number of the relay disconnected last time, it is divided into two paths. When the fifth relay RL5 conducts, the first relay RL1 is disconnected this time; when the first relay RL1 conducts, the fifth relay RL5 is disconnected this time. Among them, for the on-off state of the relay group to perform the attracting and releasing actions, it is necessary to seize the timing point and detect the zero-crossing state of the real-time mains power as necessary.

[0066] This circuit uses the zero-crossing signal, pre-attraction, and release to drive the relay, so that the on-off actions of the relay group are stepped on the zero-crossing point of the mains power. Detect the zero-crossing signal, the input end is a level signal, select the falling edge as the zero-crossing reference time point, and then judge that after the relay is at this zero-crossing falling edge, that is, the "zero-crossing reference time point", before the time difference for the next zero-crossing point to arrive (50Hz and 60Hz need to be distinguished), how long it takes to control the attraction and release to drive the relay. Wait for the time required for the relay itself to attract and release, so that the corresponding relay's on-off actions are all stepped on the zero-crossing point. During the implementation process, it can be adjusted and optimized according to the actual situation to achieve the best technical effect.

[0067] The zero-crossing attraction and release technology of the first relay RL1 and the fifth relay RL5: It not only utilizes the advantages of attracting and releasing the relay at the zero-crossing point, but also uses the alternating operation of the dual-relay control to achieve "1 + 1 > 2" to increase the operation life time of the relay and achieve the expected effect.

[0068] Among them: The zero-crossing detection pre-attracts and releases the relay, and the first relay RL1 and the fifth relay RL5 operate and release alternately.

[0069] Commercial microwave ovens, characterized in that: the load current of products in this field is nearly 10A or above, with high power, high operating environment temperature, long operating time, and high switching frequency of controlled components.

[0070] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A zero-crossing suction and release control circuit for a relay group, characterized in that, Including: A control chip U1, whose pin 1 is connected to a power supply circuit; A relay management chip U2, connected to the control chip U1 and driving a relay group; A power supply circuit: including an optocoupler U3. The first pin of the optocoupler U3 is connected to an ACL terminal, the second pin is connected to an ACN terminal. A diode D2 is connected in parallel between the first pin and the second pin. The fourth pin is connected to a GL terminal through a fifth resistor R5, and the third pin is grounded through a second capacitor C2; A relay group: including a first relay RL1 to a fifth relay RL5. Among them, the first relay RL1 and the fifth relay RL5 perform alternating on-off control, and the fifth relay RL5 is a total load switch relay; The second pin of the fifth relay RL5 is connected to an ACN terminal through a fifth insert CP5, and the first pin of the fifth relay RL5 is respectively connected to a sixth insert CP6 to a ninth insert CP9; A load circuit: including an invention tube group. The common end of the heating tube group is connected to a fifth socket CN5 to an eighth socket CN8; One end of the heating tube group is respectively connected to a first socket CN1 to a fourth socket CN4 and connected to the corresponding relay.

2. The zero-crossing suction and release control circuit for the relay group according to claim 1, wherein: The contact of the total load switch relay RL5 is connected in series in the ACN terminal of the load power supply circuit to achieve physical power-off to meet the safety regulations requirements.

3. The zero-crossing suction and release control circuit of the relay group according to claim 1, wherein: The eighth pin and the ninth pin of the relay management chip U2 are connected to a +12V power supply terminal through a capacitor C1, and the eighth pin is connected to a ground terminal GND.

4. The zero-crossing on / off control circuit for the relay bank according to claim 1, wherein: The relay group further includes a third relay RL3, and the third relay RL3 is connected to the relay management chip U2.

5. The zero-crossing suction and release control circuit of the relay group according to claim 1, characterized in that: The relay group further includes a fourth relay RL4, and the fourth relay RL4 is connected to the relay management chip U2.

6. The zero-crossing suction and release control circuit for the relay group according to claim 1, characterized in that: A first resistor R1, a second resistor R2 and a third resistor R3 are sequentially connected between the first pin of the optocoupler U3 and the ACL terminal.

7. The zero-crossing on / off control circuit for the relay bank according to claim 1, characterized in that: A fourth resistor R4 is connected to the common end between the fourth pin of the optocoupler U3 and the fifth resistor R5, and the fourth resistor R4 is connected to a +5V terminal.

8. A control method for the zero-crossing suction and release control circuit of the relay group according to any one of claims 1 to 7, characterized in that, Including the following steps: Detect the zero-crossing point of the commercial power, and use the falling edge of the zero-crossing signal as the zero-crossing reference time point; According to the on / off action time difference of the relay, predict the time window of the next zero-crossing point; Control the relay to perform an on or off action within the time window, so that the contact action precisely steps on the zero-crossing point of the commercial power; Adopt double-relay alternating control of the load on / off: When the load starts, the first relay RL1 and the fifth relay RL5 are simultaneously closed; When the load is first disconnected, release one of the relays and record its number; When the load is disconnected again, release the other relay that was not released in the previous round and update the recorded number; Subsequent load on / off cycles execute the above alternating release logic.

9. The control method according to claim 8, wherein: In the application of single-phase electricity for the double-relay, the fifth relay RL5 controls the load live wire ACL, and the first relay RL1 controls the load neutral wire ACN; In the application of two-phase electricity, the first relay RL1 controls the first phase line L1, and the fifth relay RL5 controls the second phase line L2.

10. The control method according to claim 8 or 9, characterized in that: Zero-crossing detection is achieved through the optocoupler U3. Its input terminal is connected to the mains live wire ACL via the first resistor R1, the second resistor R2, and the third resistor R3. The output terminal is grounded through the filter capacitor C2 to generate a zero-crossing signal, which is transmitted to the input pin of the control chip U1.

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