Dimming freewheeling circuit, circuit board and smart home device

Abstract

This application provides a dimming freewheeling circuit, circuit board, and smart home device, relating to the field of electronic circuit technology. It solves the technical problem in related technologies where the dimmer is damaged or produces noise due to excessive reverse voltage during phase switching, resulting in poor dimming effect. The dimming freewheeling circuit of this solution can provide a discharge circuit for the reverse electromotive force generated after phase switching to avoid the reverse electromotive force being fed back to the dimming part of the circuit, and turn off the discharge circuit during the conduction cycle to ensure the transmission of the sinusoidal voltage signal. It also suppresses the reverse overvoltage of the load in scenarios of load transition voltage and current change, which helps to reduce EMI and noise caused by voltage and current surges.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a dimming continuous current circuit, circuit board and smart home device. Background Technology

[0002] In the smart home field, phase-cut dimming products reduce the power of an AC sine wave by cutting the phase, thereby adjusting the power. Related technologies typically employ post-phase cutting, where the dimmer is triggered to turn off at any phase after the peak of each half-cycle of the sine wave (this is the off moment) to bring the voltage to zero. At the off moment, the dimmer causes the output voltage to abruptly drop from high to zero. However, in practical applications, the downstream load of the dimmer is often inductive. Inductive loads cannot withstand sudden voltage changes, resulting in a large back electromotive force during voltage abrupt changes. This causes the dimmer to experience a very high reverse voltage, potentially leading to overvoltage damage, excessive high-frequency harmonics, and vibration noise, ultimately affecting the dimming effect. Summary of the Invention

[0003] This application provides a dimming freewheeling circuit, circuit board, and smart home device, which solves the technical problem in related technologies that the dimmer is damaged and noisy due to excessive reverse voltage during phase switching, resulting in poor dimming effect. This solution can suppress reverse overvoltage of the load and reduce EMI and noise caused by voltage and current surges in the case of sudden voltage and current changes.

[0004] In a first aspect, this application provides a dimming freewheeling circuit, which includes an input protection module, a dimming drive module, a power dimming module, a dimming output module, a freewheeling drive module, an active freewheeling module, and an MCU.

[0005] The input terminal of the input protection module is used to connect to an AC power source. The input protection module is used to filter out high-frequency electromagnetic interference and provide a filtered and shaped sinusoidal voltage signal. The dimming drive module is used to output drive current upon receiving a first control signal; The input terminal of the power dimming module is connected to the phase line output terminal of the input protection module, and the control terminal of the power dimming module is connected to the output terminal of the dimming drive module. The power dimming module is used to turn on the dimming circuit when it receives the drive current. The input terminal of the dimming output module is connected to the output terminal of the power dimming module. The first output terminal of the dimming output module is used to connect to the light-emitting device in the subsequent stage. The second output terminal of the dimming output module is connected to the neutral line output terminal of the input protection module. The dimming output module is used to provide an output signal, and the output signal is used to adjust the light intensity. The freewheeling drive module is used to output drive current upon receiving a second control signal; The first access terminal of the active freewheeling module is connected to the output terminal of the power dimming module, the control terminal of the active freewheeling module is connected to the freewheeling drive module, and the second access terminal of the active freewheeling module is connected to the neutral line output terminal of the input protection module. The active freewheeling module is used to form a discharge circuit with the dimming output module when a drive current is received. The first control pin of the MCU is connected to the input terminal of the dimming driver module and is used to output the first control signal. The second control pin of the MCU is connected to the input terminal of the freewheeling driver module and is used to output the second control signal. The MCU is used to pause the output of the second control signal when the first control signal is output and to pause the output of the first control signal when the second control signal is output.

[0006] Secondly, this application also provides a circuit board that includes the dimming and freewheeling circuit as described in the first aspect above.

[0007] Thirdly, this application also provides a smart home device, which includes the circuit board as described in the second aspect above.

[0008] The dimming freewheeling circuit of this application can provide a discharge circuit for the reverse electromotive force generated after phase cutting to avoid the reverse electromotive force being fed back to the dimming part of the circuit, while realizing phase cutting operation. It can also turn off the discharge circuit during the conduction cycle to ensure the transmission of the sinusoidal voltage signal, and suppress the reverse overvoltage of the load in the case of load transition voltage and current change, which helps to reduce EMI and noise caused by voltage and current surges. Attached Figure Description

[0009] Figure 1 This is a waveform diagram illustrating the back-phase cutting of a sine wave in related technologies.

[0010] Figure 2 This is a structural block diagram of a dimming and freewheeling circuit provided in an embodiment of this application.

[0011] Figure 3 This is a schematic diagram of the structure of an input protection module provided in an embodiment of this application.

[0012] Figure 4 This is a schematic diagram of the structure of a controlled on / off unit provided in an embodiment of this application.

[0013] Figure 5 This is a schematic diagram of the structure of a dimming drive module provided in an embodiment of this application.

[0014] Figure 6 This is a schematic diagram of the structure of a dimming output module provided in an embodiment of this application.

[0015] Figure 7 This is a schematic diagram of the structure of a dimming and freewheeling circuit provided in an embodiment of this application. Detailed Implementation

[0016] The embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of this application and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, the accompanying drawings only show the parts related to the embodiments of this application, not all structures. Those skilled in the art, after reading this specification, should be able to conceive that any combination of technical features can constitute an optional implementation method, provided that the technical features do not contradict each other.

[0017] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship. In the description of this application, "multiple" means two or more, and "several" means one or more.

[0018] In the smart home field, phase-cut dimming products adjust power by cutting the phase of an AC sine wave. This is achieved by reducing the power of the sine wave. Related technologies typically employ post-phase cutting, where the dimmer is triggered to turn off at any phase after the peak of each half-cycle of the sine wave, causing the voltage to return to zero. At the moment of shutdown, the dimmer causes the output voltage to abruptly change from high to zero. Figure 1 As shown, Figure 1 This diagram illustrates the waveform of a sine wave after phase cutting in related technologies. The horizontal axis represents the phase angle (in degrees), and the vertical axis represents the voltage (in volts). It shows that within half a cycle (0-180°), the conduction period T1 is between 0-130°, while the turn-off time T2 corresponds to 130-180°, meaning the turn-off is triggered at 130° to bring the voltage to zero. However, in practical applications, the downstream load of the dimmer is often inductive. Inductive loads cannot withstand sudden voltage changes, resulting in a large back electromotive force during voltage abrupt changes. This causes the dimmer to experience a very high reverse voltage, easily leading to overvoltage damage, excessive high-frequency harmonics, and vibration noise, thus affecting the dimming effect.

[0019] In response, this application provides a dimming freewheeling circuit, which actively provides a freewheeling loop when dimming is off, thereby suppressing reverse overvoltage of the load under load transition voltage and current surge scenarios, and helping to reduce EMI (Electromagnetic Interference) and noise caused by voltage and current surges.

[0020] Figure 2 The structural block diagram of a dimming and freewheeling circuit provided in an embodiment of this application is shown in the figure. In one embodiment, the dimming and freewheeling circuit includes an input protection module 110, a dimming drive module 120, a power dimming module 130, a dimming output module 140, a freewheeling drive module 150, an active freewheeling module 160, and an MCU (Microcontroller Unit) 170. The input terminal of the input protection module 110 is used to connect to an AC power source. The input protection module 110 includes a phase wire output terminal corresponding to the phase wire (commonly known as the live wire) and a neutral wire output terminal corresponding to the neutral wire (commonly known as the neutral wire). The input terminal of the power dimming module 130 is connected to the phase wire output terminal of the input protection module 110. The control terminal of the power dimming module 130 is connected to the output terminal of the dimming drive module 120. The input terminal of the dimming output module 140 is connected to the output terminal of the power dimming module 130. The first output terminal of the dimming output module 140 is used to connect to the subsequent light-emitting device. The second output terminal of the dimming output module 140 is connected to the neutral wire output terminal of the input protection module 110.

[0021] Furthermore, the first access terminal of the active freewheeling module 160 is connected to the output terminal of the power dimming module 130, the control terminal of the active freewheeling module 160 is connected to the freewheeling drive module 150, the second access terminal of the active freewheeling module 160 is connected to the neutral line output terminal of the input protection module 110, the first control pin of the MCU 170 is connected to the input terminal of the dimming drive module 120 and is used to output the first control signal, and the second control pin of the MCU 170 is connected to the input terminal of the freewheeling drive module 150 and is used to output the second control signal.

[0022] It is understood that the input protection module 110 is used to filter out high-frequency electromagnetic interference and to filter and shape the input AC sinusoidal voltage signal. The filtered voltage signal then enters the power dimming module 130. The power dimming module 130 is used to activate the dimming circuit upon receiving a drive current. The dimming drive module 120 is controlled by the MCU 170 and is used to drive the power dimming module 130. Specifically, the dimming drive module 120 outputs a drive current upon receiving a first control signal to drive the power dimming module 130 to activate the dimming circuit, thus achieving the following: Figure 1As shown in the conduction cycle T1, the conduction operation implies that after the MCU170 pauses outputting the first control signal, the dimming driver module 120 cannot drive the power dimming module 130, thus turning off this dimming circuit, thereby achieving the following... Figure 1 The trigger shutdown shown is used to bring the voltage to zero. The dimming output module 140 is used to provide an output signal to adjust the light intensity. It can be imagined that the dimming output module 140 outputs a corresponding sine wave signal (uncut phase part) in each conduction cycle T1.

[0023] Furthermore, the active freewheeling module 160 is located between the phase line and the neutral line. The freewheeling drive module 150 is controlled by the MCU 170 and used to drive the active freewheeling module 160. Specifically, the freewheeling drive module 150 outputs a drive current upon receiving a second control signal, and the active freewheeling module 160 forms a discharge circuit upon receiving a drive current. It is understood that when the active freewheeling module 160 is driven by the freewheeling drive module 150, a conduction circuit can be formed between the phase line and the neutral line for current discharge (i.e., a discharge circuit is formed). At this time, the reverse voltage and current generated by the downstream load due to phase cutting can be discharged through this discharge circuit without feedback to the power dimming module 130, which has already been turned off in the preceding stage. It is conceivable that this discharge circuit serves as a dissipation loop for the reverse electromotive force generated by the downstream inductive device (such as an inductor). Although the reverse voltage is high, its energy storage is weak for the light-emitting device acting as a load. Therefore, during the discharge of the reverse electromotive force, the discharge circuit can complete the freewheeling consumption without affecting the downstream light-emitting device.

[0024] In this scheme, the MCU170 can control the on / off state of the dimming circuit or the discharge circuit by providing a first control signal or a second control signal at appropriate times. Specifically, the MCU170 is used to pause the output of the second control signal when the first control signal is output, and to pause the output of the first control signal when the second control signal is output. It can be understood that when the first control signal is output, the power dimming module 130, driven by the dimming driver module 120, turns on the dimming circuit and simultaneously pauses the output of the second control signal, so that the active freewheeling module 160 disconnects the discharge circuit. Conversely, when the second control signal is output, the active freewheeling module 160, driven by the freewheeling driver module 150, turns on the discharge circuit and simultaneously pauses the output of the first control signal, so that the power dimming module 130 disconnects the dimming circuit. That is, the discharge circuit is turned on when the dimming circuit is off and turned off when the dimming circuit is on.

[0025] As can be seen from the above scheme, the dimming freewheeling circuit of this scheme can provide a discharge circuit for the reverse electromotive force generated after phase cutting to avoid the reverse electromotive force being fed back to the dimming part of the circuit, and turn off the discharge circuit during the conduction period to ensure the transmission of the sinusoidal voltage signal. This enables the suppression of reverse overvoltage of the load under load transition voltage and current change scenarios, and helps to reduce EMI and noise caused by voltage and current surges.

[0026] Figure 3 The schematic diagram of an input protection module provided in an embodiment of this application is shown in the figure. The input protection module includes a fuse F1, a first varistor RV1, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, and a common-mode choke coil L1. Specifically, the first end of the first winding of the common-mode choke coil L1 is connected to one end of the fuse F1, the first end of the first capacitor C1, the first end of the first resistor R1, and the first end of the second capacitor C2. The second end of the first winding of the common-mode choke coil L1 is connected to the first end of the third capacitor C3 and the first end of the fourth capacitor C4. The second end of the first winding of the common-mode choke coil L1 serves as the phase output terminal of the input protection module. The other end of the fuse F1 is connected to the first end of the first varistor RV1, and the other end of the fuse F1 serves as the first input terminal of the input protection module to be connected to the phase line of the AC power supply. The first end of the second resistor R2 is connected to the second end of the first resistor R1, and the second end of the second resistor R2 is connected to the first end of the third resistor R3.

[0027] The first end of the second winding of the common-mode choke coil L1 is connected to the first end of the fifth capacitor C5, the second end of the third resistor R3, the second end of the first capacitor C1, and the second end of the first varistor RV1. The first end of the second winding of the common-mode choke coil L1 serves as the second input terminal of the input protection module, connected to the neutral line of the AC power supply. The second ends of the second capacitor C2 and the fifth capacitor C5 are both grounded. The second end of the second winding of the common-mode choke coil L1 is connected to the second end of the third capacitor C3 and the second end of the fourth capacitor C4. The second end of the second winding of the common-mode choke coil L1 serves as the neutral line output terminal of the input protection module.

[0028] The fuse F1 serves as a safety protection element, automatically blowing and cutting off the circuit when the current is too high, thus preventing AC power from entering the subsequent circuit. The first varistor RV1 is used for surge protection; when a momentary high-voltage surge occurs in the external AC power supply, RV1 exhibits low resistance to dissipate the surge energy and prevent damage to the subsequent circuit. The first capacitor C1, located between the phase and neutral lines, acts as an anti-interference and filter on the input side. The first resistor R1, the second resistor R2, and the third resistor R3 are connected in series and positioned between the phase and neutral lines. These resistors act as bleeder resistors, providing a circuit on the input side to dissipate the charge stored in the capacitors after power is cut off.

[0029] On the input side, the first winding of the common-mode choke coil L1 is grounded through the second capacitor C2, and the second winding of the common-mode choke coil L1 is grounded through the fifth capacitor C5. Both the second capacitor C2 and the fifth capacitor C5 are connected to the device ground, providing a high-frequency, low-impedance path to the device ground on the input side. This prevents high-frequency interference from flowing to subsequent circuits, instead directing it to the device ground along the second capacitor C2 and the fifth capacitor C5, thus ensuring the device meets electromagnetic compatibility standards. Optionally, the second capacitor C2 and the fifth capacitor C5 can be safety capacitors to enhance circuit safety. On the output side, the third capacitor C3 and the fourth capacitor C4 are connected in parallel, positioned between the phase line and the neutral line. The second end of the first winding of the common-mode choke coil L1 is filtered by the third capacitor C3 and the fourth capacitor C4 to remove residual high-frequency differential-mode interference, thus filtering the common-mode suppressed voltage signal on the output side. It is understandable that the common-mode choke coil L1 forms a common-mode filter by setting the second capacitor C2 and the fifth capacitor C5 on the input side, and forms a differential-mode filter by setting the third capacitor C3 and the fourth capacitor C4 on the output side, thereby achieving the function of EMI filtering in the front stage of the circuit, thus effectively suppressing EMI and reducing its impact on dimming.

[0030] In some embodiments, the power dimming module includes a second varistor and a controlled switching unit. The first terminal of the second varistor serves as the input terminal of the power dimming module, and the second terminal serves as the output terminal. The first input terminal of the controlled switching unit is connected to the first terminal of the second varistor, and the second input terminal is connected to the second terminal of the second varistor. The control terminal of the controlled switching unit is used to receive a first control signal. That is, the second varistor and the controlled switching unit are connected in parallel. It is conceivable that when a momentary high-voltage surge occurs in the connected AC power supply or reverse electromotive force, the second varistor exhibits a low-resistance state to dissipate the high-voltage surge energy and prevent the controlled switching unit from being damaged. The controlled switching unit is turned on under the drive of the first control signal, and remains off when the first control signal is not received. Therefore, this solution uses a controllable circuit unit to control the on / off state of the dimming circuit provided by the power dimming module, thereby effectively controlling dimming and helping to improve the accuracy of phase-cutting control.

[0031] In some embodiments, the active freewheeling module includes a cement resistor and a controlled switching unit. The first end of the cement resistor serves as the first access terminal of the active freewheeling module, the second end of the cement resistor is connected to the first access terminal of the controlled switching unit, and the second access terminal of the controlled switching unit serves as the second access terminal of the active freewheeling module. The cement resistor is a wire-wound resistor formed by winding resistance wire around an alkali-free heat-resistant ceramic piece, protecting it with heat-resistant material, and then sealing it with refractory mortar. In this active freewheeling module, the cement resistor and the controlled switching unit are connected in series. The control terminal of the controlled switching unit is connected to the output terminal of the freewheeling drive module to receive a second control signal. Driven by the second control signal, the controlled switching unit is turned on; when no second control signal is received, the controlled switching unit remains off. Therefore, this solution uses a controllable circuit unit to control the on / off state of the discharge circuit provided by the active freewheeling module, thereby effectively controlling the discharge and providing a discharge circuit even after phase cutting, which helps improve circuit stability.

[0032] In one embodiment, the controlled on / off units in the power dimming module and the active freewheeling module employ the same circuit structure. Optionally, such as... Figure 4 As shown, Figure 4This is a schematic diagram of a controlled switching unit provided in an embodiment of this application. The controlled switching unit includes a fourth resistor R4, a fifth resistor R5, a first NMOS transistor Q1, and a second NMOS transistor Q2. The drain of the first NMOS transistor Q1 serves as the first access terminal of the controlled switching unit. The gate of the first NMOS transistor Q1 is connected to the first terminal of the fourth resistor R4. The source of the first NMOS transistor Q1 is connected to the source of the second NMOS transistor Q2. The drain of the second NMOS transistor Q2 serves as the second access terminal of the controlled switching unit. The gate of the second NMOS transistor Q2 is connected to the first terminal of the fifth resistor R5. The gates of the first NMOS transistor Q1 and the second NMOS transistor Q2 both serve as control terminals of the controlled switching unit. The sources of the first NMOS transistor Q1 and the second NMOS transistor Q2, the second terminal of the fourth resistor R4, and the second terminal of the fifth resistor R5 are all connected to an isolated power ground (GND1 in the figure).

[0033] It is understandable that the first NMOS transistor Q1 and the second NMOS transistor Q2 are connected to the common source and connected to the corresponding control signal through the gate. Both the first and second control signals are high-level signals. When either the first or second control signal is received, the first NMOS transistor Q1 and the second NMOS transistor Q2 are turned on, and the controlled switching unit is turned on. When neither the first nor the second control signal is received, the first NMOS transistor Q1 and the second NMOS transistor Q2 are turned off, and the controlled switching unit is turned off. It is worth noting that although the controlled switching units in the power dimming module and the active freewheeling module use the same circuit structure and the same internal control logic, the timing of the first and second control signals is different. That is, the MCU adjusts the output of the first and second control signals to achieve two states in the circuit: the power dimming module forms a dimming loop and the active freewheeling module disconnects the discharge loop; and the power dimming module disconnects the dimming loop and the active freewheeling module forms a discharge loop. This allows the circuit to avoid the influence of reverse voltage caused by voltage surges during dimming output.

[0034] Optionally, a sixth, seventh, eighth, and ninth resistor are provided between the first NMOS transistor, the second NMOS transistor, and the isolated power ground. These resistors serve as sampling resistors for current acquisition, for example, in a power dimming module, to acquire the current during the conduction cycle. Specifically, the sixth and seventh resistors are connected in parallel, and the source of the first NMOS transistor is connected to the isolated power ground through these parallel resistors; similarly, the eighth and ninth resistors are connected in parallel, and the source of the second NMOS transistor is connected to the isolated power ground through these parallel resistors.

[0035] In one embodiment, the dimming driver module and the freewheeling driver module adopt the same circuit structure. Taking the dimming driver module as an example, Figure 5 The following is a schematic diagram of the structure of a dimming drive module provided in an embodiment of this application. As shown in the figure, the dimming drive module includes a tenth resistor R10, a gate drive optocoupler U1, a sixth capacitor C6, an eleventh resistor R11, a twelfth resistor R12, and a diode D1.

[0036] In this configuration, the first end of the tenth resistor R10 serves as the input terminal, the second end of the tenth resistor R10 is connected to the anode input terminal of the gate drive optocoupler U1, the output terminal of the gate drive optocoupler U1 is connected to the first end of the sixth capacitor C6, the first end of the eleventh resistor R11, and the first end of the twelfth resistor R12, the second end of the eleventh resistor R11 is connected to the cathode of the diode D1, the anode of the diode D1 is connected to the second end of the twelfth resistor R12, the second end of the twelfth resistor R12 serves as the output terminal, and the cathode input terminal of the gate drive optocoupler U1 and the second end of the sixth capacitor C6 are both grounded.

[0037] Understandably, the gate drive optocoupler U1, as an electronic component used to drive power semiconductor devices (such as IGBTs and MOSFETs) and achieve electrical isolation between high and low voltage circuits, can transmit control signals from the control side to the high-voltage side via optical signals, while preventing high-voltage interference from damaging the control circuit. Specifically, the tenth resistor R10 and the twelfth resistor R12 both serve as current limiters. After a high-level signal is applied to the anode of the gate drive optocoupler U1, the light-emitting diode D1 on the control side of the gate drive optocoupler U1 conducts, thereby turning on the photosensitive device on the high-voltage side. This results in a high-level signal being output at the output terminal of the gate drive optocoupler U1, serving as the corresponding first or second control signal. On the high-voltage side, the cathode of the gate drive optocoupler U1 and the second terminal of the sixth capacitor C6 are both connected to an isolated power ground (GND1 in the figure). Therefore, this solution utilizes the opto-isolation of the gate drive optocoupler U1 in the dimming drive module and the freewheeling drive module to achieve safe electrical isolation between high and low voltage circuits, while providing high-current drive to ensure accurate and reliable switching of power devices.

[0038] It should be noted that in some embodiments, a digital isolator can be used to replace the gate drive optocoupler described above, so as to transmit signals and drive the MOS transistor to work in an electrically isolated state.

[0039] In one embodiment, the dimming output module, which provides an output signal to the light-emitting device in the circuit, is provided with an inductor to smooth the current into a continuous average current using the characteristics of the inductor, while suppressing ripple and electromagnetic interference. Figure 6The figure shows a schematic diagram of a dimming output module provided in an embodiment of this application. The dimming output module includes an inductor L2, a thirteenth resistor R13, a fourteenth resistor R14, and a fifteenth resistor R15.

[0040] In this circuit, the first terminal of inductor L2 serves as the input terminal of the dimming output module, and the second terminal of inductor L2 serves as the first output terminal of the dimming output module. The second terminal of inductor L2 is connected to the first terminal of the thirteenth resistor R13, the second terminal of the thirteenth resistor R13 is connected to the first terminal of the fourteenth resistor R14, the second terminal of the fourteenth resistor R14 is connected to the first terminal of the fifteenth resistor R15, and the second terminal of the fifteenth resistor R15 serves as the second output terminal of the dimming output module. Intuitively, inductor L2 is positioned on the phase line to transmit the voltage signal. After the phase-cut voltage signal is output from the front-end stage, it passes through inductor L2 to filter out high-frequency interference before being transmitted to the subsequent stage. Furthermore, the thirteenth, fourteenth, and fifteenth resistors R13, R14, and R15 are connected in series between the phase line and the neutral line, providing a minimum sustaining current in the circuit and forming a path to ensure stable operation even at low power. The series connection also shares the voltage, thereby improving the overall voltage withstand capability. Therefore, this solution uses a dimming output module to form an interface circuit design, thereby stably transmitting the phase-cut voltage signal to the subsequent stage, reducing noise interference, and also providing a load to maintain current, which helps to reduce the occurrence of faults such as flickering and jittering of light-emitting devices, thereby improving the stability of light emission.

[0041] Optionally, a third varistor can also be set in the dimming output module. The first end of the third varistor is connected to the second end of the inductor, and the second end of the third varistor is connected to the second end of the fifteenth resistor. The third varistor is used to absorb surges to avoid overvoltage damage to the devices in the module.

[0042] Figure 7The figure shows a schematic diagram of a dimming and freewheeling circuit according to an embodiment of this application. In one embodiment, the dimming and freewheeling circuit includes an input protection module 110, a dimming drive module 120, a power dimming module 130, a dimming output module 140, a freewheeling drive module 150, an active freewheeling module 160, and an MCU (not shown in the figure). The input protection module 110 includes a fuse F1, a first varistor RV1, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2, a third capacitor C3, and a fourth capacitor C4. The dimming module 130 includes a fifth capacitor C5 and a common-mode choke coil L1. The power dimming module 130 includes a second varistor RV2, a fourth resistor R4, a fifth resistor R5, a first NMOS transistor Q1, and a second NMOS transistor Q2. The dimming drive module 120 includes a tenth resistor R10, a gate drive optocoupler U1, a sixth capacitor C6, an eleventh resistor R11, a twelfth resistor R12, and a diode D1. The freewheeling drive module 150 has the same circuit structure as the dimming drive module 120, and each module has corresponding drive circuit sections for each of the two NMOS transistors. The dimming output module 140 includes an inductor L2, a thirteenth resistor R13, a fourteenth resistor R14, and a fifteenth resistor R15.

[0043] Specifically, the first end of the first winding of the common-mode choke coil L1 is connected to one end of the fuse F1, the first end of the first capacitor C1, the first end of the first resistor R1, and the first end of the second capacitor C2. The second end of the first winding of the common-mode choke coil L1 is connected to the first end of the third capacitor C3 and the first end of the fourth capacitor C4. The other end of the fuse F1 is connected to the first end of the first varistor RV1. The first end of the second resistor R2 is connected to the second end of the first resistor R1, and the second end of the second resistor R2 is connected to the first end of the third resistor R3. The first end of the second winding of the common-mode choke coil L1 is connected to the first end of the fifth capacitor C5, the second end of the third resistor R3, the second end of the first capacitor C1, and the second end of the first varistor RV1. The second ends of the second capacitor C2 and the fifth capacitor C5 are both grounded. The second end of the second winding of the common-mode choke coil L1 is connected to the second end of the third capacitor C3 and the second end of the fourth capacitor C4.

[0044] The second varistor RV2 is connected to the first terminal of the third capacitor C3 and the drain of the first NMOS transistor Q1. The gate of the first NMOS transistor Q1 is connected to the first terminal of the fourth resistor R4. The source of the first NMOS transistor Q1 is connected to the source of the second NMOS transistor Q2. The gate of the second NMOS transistor Q2 is connected to the first terminal of the fifth resistor R5. The sources of the first NMOS transistor Q1, the source of the second NMOS transistor Q2, the second terminal of the fourth resistor R4, and the second terminal of the fifth resistor R5 are all connected to the isolated power ground (i.e., GND1).

[0045] The gate of the first NMOS transistor Q1 and the gate of the second NMOS transistor Q2 are respectively connected to the corresponding dimming drive module 120, and the circuit structure of the drive circuit connected to both is the same. Taking the first NMOS transistor Q1 as an example, the gate of the first NMOS transistor Q1 is connected to the second end of the twelfth resistor R12, and the second end of the tenth resistor R10 is connected to the anode input terminal of the gate drive optocoupler U1. The output terminal of the gate drive optocoupler U1 is connected to the first end of the sixth capacitor C6, the first end of the eleventh resistor R11, and the first end of the twelfth resistor R12. The second end of the eleventh resistor R11 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the second end of the twelfth resistor R12. The cathode input terminal of the gate drive optocoupler U1 and the second end of the sixth capacitor C6 are both grounded.

[0046] Furthermore, the drain of the second NMOS transistor Q2 is connected to the first terminal of inductor L2, the second terminal of inductor L2 is connected to the first terminal of the thirteenth resistor R13, the second terminal of the thirteenth resistor R13 is connected to the first terminal of the fourteenth resistor R14, the second terminal of the fourteenth resistor R14 is connected to the first terminal of the fifteenth resistor R15, and the second terminal of the fifteenth resistor R15 serves as the second output terminal of the dimming output module 140. In the active freewheeling module 160, the drain of NMOS transistor Q3 is connected to the first terminal of inductor L2 via a cement resistor Rx. NMOS transistors Q3 and Q4 are connected to a common source, and the gates of both NMOS transistors Q3 and Q4 are connected to grounded resistors (resistors R16 and R17 in the figure) and driven by the corresponding freewheeling drive module 150. The circuit structure of the freewheeling drive module is the same as that of the dimming drive module, and will not be elaborated further here.

[0047] Understandably, in practical applications, the common-mode choke coil L1 is connected to the phase line and neutral line through the first winding and the second winding, respectively, and is equipped with capacitors and resistors to perform common-mode filtering on the input side of the voltage signal. On the output side, the residual high-frequency differential-mode interference is filtered out through the parallel third capacitor C3 and the fourth capacitor C4, thereby transmitting a stable voltage signal to the first NMOS transistor Q1. During the conduction period, the MCU outputs the first control signal and pauses the output of the second control signal. In response, the gate drive optocouplers U1 and U2 (corresponding to the gate drive optocouplers of the second NMOS transistor Q2) output drive currents respectively, and form a high level on the gate of the first NMOS transistor Q1 through the fourth resistor R4, and form a high level on the gate of the second NMOS transistor Q2 through the fifth resistor R5. Thus, both the first NMOS transistor Q1 and the second NMOS transistor Q2 are turned on to transmit the voltage to the inductor L2 of the subsequent stage, and then to the light-emitting device of the subsequent stage through the inductor L2, that is, the dimming circuit is turned on. Furthermore, during the conduction period, both NMOS transistors Q3 and Q4 in the active freewheeling module 160 are turned off. If the MCU pauses outputting the second control signal, then the gate drive optocouplers U3 (which is the gate drive optocoupler corresponding to NMOS transistor Q3) and U4 (which is the gate drive optocoupler corresponding to NMOS transistor Q4) cannot provide drive current to NMOS transistors Q3 and Q4. That is, the gates of NMOS transistors Q3 and Q4 are both at a low level, and therefore, both NMOS transistors Q3 and Q4 are turned off.

[0048] During the shutdown period, the MCU outputs the second control signal and pauses the output of the first control signal. In response, both gate drive optocouplers U1 and U2 stop outputting drive current, creating a low-level signal at the gate of the first NMOS transistor Q1 and the gate of the second NMOS transistor Q2, thus turning off both NMOS transistors Q1 and Q2. Gate drive optocouplers U3 and U4 provide drive current to NMOS transistors Q3 and Q4, creating a high-level signal at the gate of NMOS transistor Q3 through resistor R16 and a high-level signal at the gate of NMOS transistor Q4 through resistor R17. This turns on both NMOS transistors Q3 and Q4, providing a discharge path for inductor L2 to discharge the back electromotive force generated by inductor L2.

[0049] Therefore, the dimming freewheeling circuit of this solution can provide a discharge circuit for the reverse electromotive force generated after phase cutting to avoid the reverse electromotive force being fed back to the dimming part of the circuit, while realizing phase cutting operation. It can also turn off the discharge circuit during the conduction period to ensure the transmission of the sinusoidal voltage signal and suppress the reverse overvoltage of the load in the case of load transition voltage and current change.

[0050] This application embodiment also provides a circuit board including the dimming freewheeling circuit provided in the above embodiment, so as to provide a discharge circuit for the generated reverse electromotive force after phase cutting to avoid the reverse electromotive force being fed back to the dimming part of the circuit, and to turn off the discharge circuit during the conduction period to ensure the transmission of the sinusoidal voltage signal, and suppress the reverse overvoltage of the load in the scenario of load transition voltage and current change.

[0051] This application also provides a smart home device, which includes the circuit board provided in the above embodiments. Through the dimming and continuous current circuit set on the circuit board, the smart home device can form a stable dimming control, effectively suppress reverse overvoltage of the load, and improve the stability of the product.

[0052] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0053] Note that the above are merely preferred embodiments and the technical principles employed in this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of this application, the scope of which is determined by the scope of the appended claims.

Claims

1. A dimming freewheeling circuit, characterized in that, include: An input protection module is provided, the input terminal of which is used to connect to an AC power source. The input protection module is used to filter out high-frequency electromagnetic interference and provide a filtered and shaped sinusoidal voltage signal. A dimming drive module, wherein the dimming drive module is used to output a drive current upon receiving a first control signal; A power dimming module, wherein the input terminal of the power dimming module is connected to the phase line output terminal of the input protection module, and the control terminal of the power dimming module is connected to the output terminal of the dimming drive module, and the power dimming module is used to turn on the dimming circuit when a drive current is received; A dimming output module, wherein the input terminal of the dimming output module is connected to the output terminal of the power dimming module, the first output terminal of the dimming output module is used to connect to the light-emitting device in the subsequent stage, the second output terminal of the dimming output module is connected to the neutral line output terminal of the input protection module, and the dimming output module is used to provide an output signal, the output signal being used to adjust the light intensity; A freewheeling drive module, wherein the freewheeling drive module is used to output a drive current upon receiving a second control signal; An active freewheeling module is provided, wherein the first access terminal of the active freewheeling module is connected to the output terminal of the power dimming module, the control terminal of the active freewheeling module is connected to the freewheeling drive module, and the second access terminal of the active freewheeling module is connected to the neutral line output terminal of the input protection module. The active freewheeling module is used to form a discharge circuit with the dimming output module when a drive current is received. The MCU has a first control pin connected to the input of the dimming drive module and used to output the first control signal, and a second control pin connected to the input of the freewheeling drive module and used to output the second control signal. The MCU is used to pause the output of the second control signal when the first control signal is output and to pause the output of the first control signal when the second control signal is output.

2. The dimming freewheeling circuit according to claim 1, characterized in that, The input protection module includes a fuse, a first varistor, a first resistor, a second resistor, a third resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, and a common-mode choke coil; The first end of the first winding of the common mode choke coil is connected to one end of the fuse, the first end of the first capacitor, the first end of the first resistor, and the first end of the second capacitor. The second end of the first winding of the common mode choke coil is connected to the first end of the third capacitor and the first end of the fourth capacitor. The second end of the first winding of the common mode choke coil serves as the phase line output terminal of the input protection module. The other end of the fuse is connected to the first end of the first varistor, and the other end of the fuse serves as the first input terminal of the input protection module to be connected to the phase line of the AC power supply. The first end of the second resistor is connected to the second end of the first resistor, and the second end of the second resistor is connected to the first end of the third resistor. The first end of the second winding of the common mode choke coil is connected to the first end of the fifth capacitor, the second end of the third resistor, the second end of the first capacitor, and the second end of the first varistor. The first end of the second winding of the common mode choke coil serves as the second input terminal of the input protection module to be connected to the neutral line of the AC power supply. The second terminal of the second capacitor and the second terminal of the fifth capacitor are both grounded. The second terminal of the second winding of the common mode choke coil is connected to the second terminal of the third capacitor and the second terminal of the fourth capacitor. The second terminal of the second winding of the common mode choke coil serves as the neutral line output terminal of the input protection module.

3. The dimming freewheeling circuit according to claim 1, characterized in that, The power dimming module includes a second varistor and a controlled on / off unit. The first end of the second varistor serves as the input end of the power dimming module, and the second end of the second varistor serves as the output end of the power dimming module. The first input end of the controlled on / off unit is connected to the first end of the second varistor, and the second input end of the controlled on / off unit is connected to the second end of the second varistor. The control end of the controlled on / off unit is used to receive the first control signal.

4. The dimming freewheeling circuit according to claim 1, characterized in that, The active current-continuing module includes a cement resistor and a controlled switching unit. The first end of the cement resistor serves as the first access terminal of the active current-continuing module, the second end of the cement resistor is connected to the first access terminal of the controlled switching unit, and the second access terminal of the controlled switching unit serves as the second access terminal of the active current-continuing module.

5. The dimming freewheeling circuit according to claim 3 or 4, characterized in that, The controlled switching unit includes a fourth resistor, a fifth resistor, a first NMOS transistor, and a second NMOS transistor; The drain of the first NMOS transistor serves as the first access terminal of the controlled on / off unit. The gate of the first NMOS transistor is connected to the first terminal of the fourth resistor. The source of the first NMOS transistor is connected to the source of the second NMOS transistor. The drain of the second NMOS transistor serves as the second access terminal of the controlled on / off unit. The gate of the second NMOS transistor is connected to the first terminal of the fifth resistor. Both the gate of the first NMOS transistor and the gate of the second NMOS transistor serve as the control terminals of the controlled on / off unit. Furthermore, the sources of the first NMOS transistor, the second NMOS transistor, the second terminal of the fourth resistor, and the second terminal of the fifth resistor are all connected to an isolated power ground.

6. The dimming freewheeling circuit according to claim 5, characterized in that, It also includes the sixth, seventh, eighth, and ninth resistors; The source of the first NMOS transistor is connected to an isolated power ground through the sixth and seventh resistors connected in parallel, and the source of the second NMOS transistor is connected to an isolated power ground through the eighth and ninth resistors connected in parallel.

7. The dimming freewheeling circuit according to claim 1, characterized in that, Both the dimming drive module and the freewheeling drive module include a tenth resistor, a gate drive optocoupler, a sixth capacitor, an eleventh resistor, a twelfth resistor, and a diode; The first end of the tenth resistor serves as the input terminal, the second end of the tenth resistor is connected to the anode input terminal of the gate drive optocoupler, the output terminal of the gate drive optocoupler is connected to the first end of the sixth capacitor, the first end of the eleventh resistor, and the first end of the twelfth resistor, the second end of the eleventh resistor is connected to the cathode of the diode, the anode of the diode is connected to the second end of the twelfth resistor, the second end of the twelfth resistor serves as the output terminal, and both the cathode input terminal of the gate drive optocoupler and the second end of the sixth capacitor are grounded.

8. The dimming freewheeling circuit according to claim 1, characterized in that, The dimming output module includes an inductor, a thirteenth resistor, a fourteenth resistor, and a fifteenth resistor; The first end of the inductor serves as the input end of the dimming output module, the second end of the inductor serves as the first output end of the dimming output module, the second end of the inductor is connected to the first end of the thirteenth resistor, the second end of the thirteenth resistor is connected to the first end of the fourteenth resistor, the second end of the fourteenth resistor is connected to the first end of the fifteenth resistor, and the second end of the fifteenth resistor serves as the second output end of the dimming output module.

9. A circuit board, characterized in that, Includes the dimming freewheeling circuit as described in any one of claims 1-8.

10. A smart home device, characterized in that, Includes the circuit board as described in claim 9.

Images