Method for controlling a bleeder connected to a phase-cut dimmer and a circuit connected to a phase-cut dimmer - Patents.com

Abstract

To provide a method for controlling a bleeder connected to a phase-cut dimmer and a circuit connected to a phase-cut dimmer.SOLUTION: The method includes: a step S101 of detecting an input voltage of the bleeder to obtain a detection voltage, and comparing the detection voltage and a preset reference voltage, wherein during a first time period, the detection voltage is less than the preset reference voltage, a start point of the first time period is a first moment, and an end point of the first time period is a second moment; a step S102 of delaying a first preset duration on the basis of the second moment to turn off the bleeder; and a step S103 of advancing a second preset duration on the basis of the first moment to turn on the bleeder. The present invention can detect the operation order of a dimmer on the basis of the comparison signal input to a controller, can secure that there is no flashing in the time of dimming by controlling the bleeder, also includes a front cut-dimmer and a rear cut-dimmer, and has the excellent compatibility, the high control accuracy and the strong interference prevention performance.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to the field of electronics, and in particular to a method for controlling a bleeder connected to a phase-cut dimmer and a circuit connected to a phase-cut dimmer. [Background technology]

[0002] Currently, most phase-cut dimmers on the market are controlled by a thyristor or a triac, which is a bidirectional thyristor. According to the characteristics of a thyristor, when the current flowing through the thyristor is less than the current that keeps the thyristor ON, the thyristor will turn OFF and the light will go out.

[0003] Therefore, in order to be able to use an LED power supply with a thyristor dimmer, the current flowing through the thyristor when the LED power supply is operating must be greater than the thyristor's holding current. Only then will the thyristor dimmer operate properly and dimming can be achieved.

[0004] In order to provide sufficient holding current to ensure the normal operation of the dimmer, it is currently widely used to control the bleeder by MCU (Micro Control Unit, Microcontroller Unit) real-time detection. As shown in Figure 1, when the input voltage of the bleeder is detected, a detection voltage Vt is obtained. If the detection voltage Vt is lower than the preset threshold Vd, the MCU turns the bleeder ON by the control signal Sc. If the detection voltage Vt is higher than the preset threshold Vd, the MCU turns the bleeder OFF by the control signal Sc. However, in such a control method, the MCU needs to sample the detection voltage Vt in real time, and a relatively high sampling rate is required to accurately control the bleeder, so a relatively large MCU execution time must be taken. In addition, in such a control method, if interference occurs, the circuit loss is relatively large, the heat is significant, and the efficiency of the circuit may be affected. In addition, in the case of a rear-cut dimmer, such a control method cannot turn on the bleeder in advance, which may cause inaccurate detection of the phase cut angle, affecting dimming and causing flashing. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above-mentioned conventional problems, and provides a method for controlling a bleeder connected to a phase-cut dimmer and a circuit connected to a phase-cut dimmer, which can solve one or more defects of the prior art. [Means for solving the problem]

[0006] In order to achieve the above object, according to one embodiment of the present invention, the present invention provides a method for controlling a bleeder connected to a phase-cut dimmer, the method includes: detecting an input voltage of the bleeder to obtain a detected voltage; comparing the detected voltage with a preset reference voltage; determining that, in a first time period, the detected voltage is lower than the preset reference voltage, the start point of the first time period is a first time and the end point of the first time period is a second time; delaying the bleeder by a first predetermined time based on the second time period and turning the bleeder on by advancing the second predetermined time based on the first time period.

[0007] In one preferred embodiment of the present invention, turning the bleeder OFF corresponds to generating a low level control signal to the bleeder, and turning the bleeder ON corresponds to generating a high level control signal to the bleeder.

[0008] In one embodiment of the present invention, the bleeder is turned OFF by a first timer, and the bleeder is turned ON by a second timer different from the first timer.

[0009] In one embodiment of the invention, the method includes detecting a waveform in real time, comparing the detected voltage with the preset reference voltage; starting the first timer when a falling edge of the waveform is detected, turning the bleeder OFF when a set time of the first timer expires, the set time of the first timer being equal to the first predetermined time; starting the second timer when a rising edge of the waveform is detected, turning the bleeder ON when a set time of the second timer expires, the set time of the second timer being equal to a current reference period of the input voltage minus the second predetermined time.

[0010] In one embodiment of the invention, the method further comprises determining a current reference period of the input voltage after detecting a rising edge of the waveform and before starting the second timer.

[0011] In one embodiment of the present invention, determining a current reference period of the input voltage comprises determining a first period of the input voltage based on two adjacent rising edges of the waveform, determining a second period of the input voltage based on two adjacent falling edges of the waveform, and comparing the first period and the second period to select a smaller period as the current reference period of the input voltage.

[0012] In a preferred embodiment of the present invention, determining a first period of the input voltage comprises: calculating a current first period by a microcontroller unit based on currently captured values ​​of two adjacent rising edges of the waveform; comparing the current first period with a power grid period, and if the current first period is within a normal range of the power grid period, the current first period is the first period of the input voltage, and if the current first period is outside the normal range of the power grid period, using a previous first period as the first period of the input voltage. Determining a second period of the input voltage comprises: calculating a current second period by the microcontroller unit based on currently captured values ​​of two adjacent falling edges of the waveform; comparing the current second period with a power grid period, and if the current second period is within the normal range of the power grid period, the current second period is the second period of the input voltage, and if the current second period is outside the normal range of the power grid period, using a previous second period as the second period of the input voltage.

[0013] In one preferred embodiment of the invention, the phase-cut dimmer is a front-cut dimmer or a rear-cut dimmer.

[0014] In one preferred embodiment of the invention, if the phase-cut dimmer is a front-cut dimmer, the bleeder is controlled by sensing the current through the bleeder.

[0015] In a preferred embodiment of the present invention, controlling the bleeder by detecting the current flowing through the bleeder includes: during a period in which the input voltage is phase-cut, the bleeder is in an ON state, the input voltage is zero, and the detected current flowing through the bleeder is also zero; and when the input voltage exceeds zero, it is detected that the current flowing through the bleeder starts to become larger than zero; and at this time, a first timer is started, and the bleeder is turned OFF after a delay of the first predetermined time.

[0016] In order to achieve the above object, the present invention further provides a circuit connected to a phase-cut dimmer, the circuit comprising: a bleeder electrically connected to the phase-cut dimmer, an input voltage detector for detecting an input voltage of the bleeder and obtaining a detected voltage, a comparator for generating a comparison signal by comparing the detected voltage with a preset reference voltage, the detected voltage being lower than the preset reference voltage in a first time period, the start point of the first time period being a first time, and the end point of the first time period being a second time, and a controller for delaying the first predetermined time based on the second time period to turn off the bleeder and advancing the second predetermined time based on the first time period based on the detected voltage and the comparison signal, to turn on the bleeder.

[0017] In another embodiment of the invention, the controller responds to turning off the bleeder by generating a low level control signal to the bleeder and responds to turning on the bleeder by generating a high level control signal to the bleeder.

[0018] In another embodiment of the invention, the controller further comprises a first timer for turning the bleeder OFF and a second timer for turning the bleeder ON.

[0019] In another embodiment of the present invention, the controller is configured to detect a waveform obtained by comparing the detected voltage and the preset reference voltage in real time, start the first timer when a falling edge of the waveform is detected, and turn off the bleeder when a set time of the first timer ends, and start the second timer when a rising edge of the waveform is detected, and turn on the bleeder when a set time of the second timer ends, wherein the set time of the first timer is equal to the first predetermined time, and the set time of the second timer is equal to a current reference period of the input voltage minus the second predetermined time.

[0020] In another embodiment of the invention, the controller is also used to determine a present reference period of the input voltage after detecting a rising edge of the waveform and before starting the second timer.

[0021] In another embodiment of the invention, the controller determining a current reference period of the input voltage comprises determining a first period of the input voltage based on two adjacent rising edges of the waveform, determining a second period of the input voltage based on two adjacent falling edges of the waveform, and selecting a smaller value of the first period and the second period as the current reference period of the input voltage.

[0022] In another embodiment of the present invention, the controller is a microcontroller unit. The controller determining a first period of the input voltage comprises: calculating a current first period by the microcontroller unit based on currently acquired values ​​of two adjacent rising edges of the waveform; comparing the first period with a power grid period; and if the current first period is within a normal range of the power grid period, the current first period is the first period of the input voltage; and if the current first period is outside the normal range of the power grid period, using a previous first period as the first period of the input voltage. The controller determining a second period of the input voltage comprises: calculating a current second period by the microcontroller unit based on currently acquired values ​​of two adjacent falling edges of the waveform; comparing the second period with the power grid period; and if the current second period is within the normal range of the power grid period, the current second period is the second period of the input voltage; and if the current second period is outside the normal range of the power grid period, using a previous second period as the second period of the input voltage.

[0023] In another embodiment of the invention, the phase-cut dimmer is a front-cut dimmer or a rear-cut dimmer.

[0024] In another embodiment of the invention, if the phase-cut dimmer is a front-cut dimmer, the controller controls the bleeder by detecting the current flowing through the bleeder.

[0025] In another embodiment of the present invention, the controller controlling the bleeder by detecting the current flowing through the bleeder comprises controlling the bleeder to be in an ON state during a period in which the input voltage is phase-cut, detecting that the input voltage is zero and the detected current flowing through the bleeder is also zero, and detecting that the current flowing through the bleeder starts to become larger than zero when the input voltage exceeds zero, and controlling to start a first timer at this time, and turning off the bleeder after delaying the first predetermined time.

[0026] In another embodiment of the present invention, the comparator and the controller are integrated in a microcontroller unit.

[0027] In another embodiment of the present invention, the circuit further includes a rectifier for rectifying the voltage after the phase-cut dimmer has cut the phase and outputting the rectified voltage to the bleeder and the input voltage detector.

[0028] In another embodiment of the present invention, the circuit further comprises a power converter that receives the voltage output by the phase-cut dimmer and supplies power to a load, wherein the controller is also used to determine a dimming signal based on the comparison signal, and the power converter receives the dimming signal and adjusts the brightness of the load. Effect of the Invention

[0029] The present invention can detect the operation sequence of the dimmer based on the comparison signal input to the controller, and control the bleeder to prevent the dimmer from flickering. The present invention combines a front cut dimmer and a rear cut dimmer, with good compatibility, high control precision, and strong anti-interference ability.

[0030] Additional aspects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a waveform diagram of a conventional control method. [Diagram 2] FIG. 1 is a schematic diagram illustrating a flow chart of a method for controlling a bleeder connected to a phase-cut dimmer according to the present invention. [Diagram 3] FIG. 2 is a schematic diagram illustrating the configuration architecture of a circuit connected to a phase-cut dimmer in accordance with the present invention. [Figure 4] FIG. 13 is a schematic diagram illustrating waveforms for providing front-cut control to a bleeder connected to a phase-cut dimmer in accordance with the present invention. [Diagram 5] FIG. 13 is a schematic diagram illustrating waveforms for providing rear-cut control to a bleeder connected to a phase-cut dimmer in accordance with the present invention. [Figure 6] 1 is a schematic diagram illustrating a flow chart for performing software control by an MCU in the control method of the present invention; [Figure 7] FIG. 2 is a schematic diagram showing a circuit structure for applying the control method of the present invention to one specific embodiment. [Figure 8] FIG. 13 is a schematic diagram illustrating waveforms for performing front-cut control on a front-cut dimmer in practical application. [Figure 9] FIG. 13 is a schematic diagram illustrating waveforms for performing rear-cut control on a rear-cut dimmer in practical application. [Figure 10] FIG. 13 is a schematic diagram illustrating the configuration architecture of another embodiment of the circuit when the phase-cut dimmer is a front-cut dimmer. [Figure 11] 11 is a schematic diagram illustrating waveforms for performing front cut control in the embodiment shown in FIG. 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The above and other features and advantages of the present invention will become more apparent by describing exemplary embodiments with reference to the drawings. In order to provide a deeper understanding of the technical features and technical effects of the present invention, the present invention will be described in more detail with reference to the drawings and exemplary embodiments and parameter values. In addition, in order to more intuitively show the configuration and details of the present invention, the following description will be given using an AC charging example, but it should be noted that the present invention is not limited to AC and can also be applied to DC charging.

[0033] Hereinafter, the exemplary embodiments will be described in more detail with reference to the drawings. However, the exemplary embodiments can be implemented in various ways and should not be construed as being limited to the implementation methods described in this specification. Rather, the provision of these embodiments will make the present invention more complete and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings indicate the same or similar structures, and detailed descriptions will be omitted.

[0034] When introducing elements / components / etc. described and / or illustrated herein, the terms "a," "an," "the," "said," and "at least one" indicate the presence of one or more elements / components / etc. The terms "comprise," "include," and "have" are open-ended and inclusive, indicating that other elements / components / etc. may be present in addition to the recited elements / components / etc. Additionally, the terms "first," "second," and the like in the claims are used as labels only and do not numerically limit their subject matter.

[0035] As shown in Figure 2, the present invention provides a method 100 for controlling a bleeder connected to a phase-cut dimmer. The method mainly includes steps S101, S102 and S103.

[0036] In step S101, a detected voltage is obtained by detecting an input voltage of a bleeder, and the detected voltage is compared with a preset reference voltage. In a first time period, the detected voltage is lower than the preset reference voltage, the start point of the first time period is a first time, and the end point of the first time period is a second time.

[0037] In step S102, the bleeder is turned OFF with a delay of a first predetermined time based on the second time (that is, with an additional first predetermined time added).

[0038] In S103, the bleeder is turned ON by bringing forward a second predetermined time based on the first time (that is, by advancing the second predetermined time).

[0039] As shown in FIG. 3, a circuit 200 connected to a phase-cut dimmer 25 of the present invention is shown, and the circuit 200 can be connected between an L line and an N line through a phase-cut dimmer 25, for example. The circuit 200 may include, for example, a bleeder 21, an input voltage detector 22, a comparator 23, and a controller 24. The bleeder 21 can be electrically connected to the phase-cut dimmer 25. The input voltage detector 22 can obtain a detection voltage Vt by detecting an input voltage of the bleeder 21. The comparator 23 can be used to generate a comparison signal Dim_in by comparing the detection voltage Vt with a preset reference voltage Vref. In a first time period, the detection voltage Vt is lower than the preset reference voltage Vref, the start point of the first time period is a first time, and the end point of the first time period is a second time. The controller 24 can be used to turn off the bleeder by delaying a first predetermined time based on the second time, and to turn on the bleeder by advancing a second predetermined time based on the first time, based on the detection voltage Vt and the comparison signal Dim_in.

[0040] In this embodiment, the bleeder 21 may be, for example, a constant current bleeder circuit, the controller 24 may be, for example, a microcontroller unit (MCU), and the load 28 may be, for example, an LED, but the present invention is not limited thereto.

[0041] In some embodiments of the present invention, the circuit 200 may further include a rectifier 26 for rectifying the voltage after being phase-cut by the phase-cut dimmer 25 and outputting the rectified voltage to the bleeder 21 and the input voltage detector 22.

[0042] In some embodiments of the present invention, the circuit 200 may further include a power converter 27 that receives the voltage output by the phase-cut dimmer 25 and supplies power to a load 28. The power converter 27 may be, for example, an AC / DC converter. Note that the controller 24 may further be used to determine a dimming signal Dim based on the comparison signal Dim_in, and the power converter 27 receives the dimming signal Dim and adjusts the brightness of the load 28 (e.g., an LED).

[0043] In one specific embodiment shown in FIG. 3, the controller 24 is an MCU, the load 28 is an LED, and the power converter 27 is an AC / DC converter as an example, and the circuit and its control method of the present invention will be described in more detail. In this specific embodiment, the AC voltage between the L line and the N line is phase-cut by the phase-cut dimmer 25 and then output to the power converter 27. The power converter 27 converts the phase-cut voltage and provides an output voltage to the load 28. The rectifier 26 rectifies the phase-cut voltage into a full-wave voltage. The full-wave voltage is converted by the input voltage detector 22 to obtain a detection voltage Vt, and the detection voltage Vt is sent to the sampling port (e.g., port A1) of the MCU and the comparator 23 at the same time. The reference terminal of the comparator 23 is a fixed, preset reference voltage Vref, and a comparison signal Dim_in is generated after the detection voltage Vt is compared with the preset reference voltage Vref, and is sent to the MCU (e.g., sent to port A2) for calculating the dimming current. FIG. 4 shows the waveform of the comparison signal Dim_in. Of course, the comparator 23 here can also be realized by adopting a comparator inside the MCU, that is, the comparator 23 and the controller 24 can be integrated into the MCU to save circuit costs. The MCU calculates the phase cut angle by sampling the width of the high level and low level of the comparison signal Dim_in, and outputs the dimming signal Dim corresponding to the dimming brightness from the port A3. The dimming signal Dim finally controls the power converter 27 to output a corresponding current, thereby controlling the brightness of the LED (i.e., the load 28). The rectified voltage can also be sent to the bleeder 21 at the same time, and the on and off of the bleeder 21 can be determined by the control signal Sc (output from the port A4 of the MCU), for example, the bleeder can be turned off by generating a low level control signal to the bleeder, and the bleeder can be turned on by generating a high level control signal to the bleeder, but the present invention is not limited thereto.

[0044] Specific control waveforms of the present invention include operation waveforms when a front cut dimmer and a rear cut dimmer are connected, as shown in Figs. 4 and 5. Fig. 4 shows a control waveform used in a front cut dimmer to perform front cut control, and Fig. 5 shows a control waveform used in a rear cut dimmer to perform rear cut control. As shown in Figs. 4 and 5, from top to bottom, the waveforms are the detection voltage Vt, the comparison signal Dim_in, the output DT1 of the first timer, the output DT2 of the second timer, the control signal Sc, and the current ibleeder flowing through the bleeder. The comparison signal Dim_in is a waveform obtained by comparing the detection voltage Vt with a preset reference voltage Vref. Note that, when the detection voltage Vt is greater than the preset reference voltage Vref, the comparison signal Dim_in is at a low level (Low). Conversely, when the detection voltage Vt is less than the preset reference voltage Vref, the comparison signal Dim_in is at a high level (High).

[0045] Referring to Fig. 3, as shown in Fig. 4, taking the front cut control of the front cut dimmer as an example, the control logic of the bleeder is as follows: MCU detects the comparison signal Dim_in in real time, and if the comparison signal Dim_in is within a first time period tp, the detection voltage Vt is lower than the preset reference voltage Vref, and the start point of the first time period tp is set as the first time t1, and the end point of the first time period tp is set as the second time t2.

[0046] When the MCU detects a falling edge of the comparison signal Dim_in, the MCU starts a first timer, and the first timer outputs a high level within a set time Td1. The first timer starts a set time based on the second time t2, and this set time starts, for example, at a time point ST of the output DT1 waveform of the first timer and ends at that time point EN. When the set time Td1 of the first timer ends, the MCU turns off the bleeder 21 by the control signal Sc, and the current flowing through the bleeder 21 becomes zero. For example, when the set time Td1 ends, the control signal Sc changes from a high level to a low level to prevent the bleeder 21 from operating (i.e., the bleeder is turned off).

[0047] When the MCU detects a rising edge of the comparison signal Dim_in, the MCU starts the second timer, which outputs a high level within a set time Td2. The second timer starts the set time based on the first time t1, and this set time starts, for example, at a time point ST of the output DT2 waveform of the second timer and ends at that time point EN. When the set time Td2 of the second timer ends, the MCU turns on the bleeder 21 by the control signal Sc. For example, when the set time Td2 ends, the control signal Sc changes from a low level to a high level, causing the bleeder 21 to operate (i.e., the bleeder turns on).

[0048] In some embodiments of the present invention, the set time Td1 of the first timer is equal to the first predetermined time and is a fixed value. The set time Td1 should not be too large. For a front cut dimmer, the input voltage at this time is relatively high, so if the set time Td1 is too large, the loss of the bleeder will be large, which will affect the circuit efficiency. Therefore, it is only necessary to ensure that the dimmer is not turned off when linking occurs in the dimmer. The set time Td2 of the second timer is not fixed, and the MCU needs to ensure that the second timer turns on the bleeder before the next rising edge of the comparison signal Dim_in so that the MCU can correctly detect the comparison signal Dim_in. Therefore, the second timer can calculate the set time Td2 by subtracting the second predetermined time Tahead from the current reference period T of the input voltage of the bleeder, that is, Td2=T-Tahead.

[0049] In some embodiments of the present invention, the method further comprises determining a current reference period of the input voltage after detecting a rising edge of the comparison signal Dim_in and before starting a second timer. In particular, the MCU detects a current reference period T of the input voltage based on the comparison signal Dim_in. In order to avoid input voltage distortion or dimming interference, the MCU simultaneously detects a first period T1 of two adjacent rising edges of the comparison signal Dim_in and a second period T2 of two adjacent falling edges, and selects a relatively smaller value of the first period T1 and the second period T2 as the current reference period T of the input voltage, which is used as a reference value for calculating a set time Td2 of the second timer. This can improve reliability and avoid turning off the dimmer due to the bleeder being turned on too late.

[0050] In a preferred embodiment, the first period T1 and the second period T2 can be realized by the acquisition function of the MCU, and the specific control can refer to the flowchart shown in Fig. 6. The MCU can determine the first period T1 based on the currently acquired values ​​of two adjacent rising edges of the comparison signal Dim_in, and determine the second period T2 based on the currently acquired values ​​of two adjacent falling edges of the comparison signal Dim_in.

[0051] More specifically, as shown in Fig. 6, when the MCU detects a rising edge of the comparison signal Dim_in (S11: yes), the MCU can read the current acquisition value and calculate a current first period Ts1 based on the current acquisition values ​​of two adjacent rising edges (S12). When the current first period Ts1 is within the normal range of the power grid period (for example, Ts1 satisfies 50Hz ± 3Hz or 60Hz ± 3Hz (S13: yes), but the present invention is not limited thereto), the MCU selects the current first period Ts1 as the first period T1 (S14). When the current first period Ts1 is not within the normal range of the power grid period (for example, Ts1 does not satisfy 50Hz ± 3Hz or 60Hz ± 3Hz (S13: no), but the present invention is not limited thereto), the MCU selects the previous first period as the first period T1.

[0052] If the MCU detects a falling edge of the waveform of the comparison signal Dim_in (S24: yes), the MCU can read the current acquisition value and calculate the current second period Ts2 based on the current acquisition value of the two adjacent falling edges (S25). If the current second period Ts2 is within the normal range of the power grid period (for example, Ts2 satisfies 50Hz±3Hz or 60Hz±3Hz (S26: yes), but the present invention is not limited to this), the MCU selects the current second period Ts2 as the second period T2 (S27). If the current second period Ts2 is not within the normal range of the power grid period (for example, Ts2 does not satisfy 50Hz±3Hz or 60Hz±3Hz (S26: no), but the present invention is not limited to this), the MCU selects the previous second period as the second period T2. In addition, the second period T2 can also be used to calculate the current reference period T of the input voltage by comparing it with the first period T1 calculated the next time (the area indicated by the dashed line in the same figure).

[0053] When the first period T1 and the second period T2 are determined, the MCU compares the first period T1 and the second period T2 (S15), selects a relatively smaller value between the first period T1 and the second period T2 as the current reference period T of the input voltage, and sets the current reference period T as the reference value of the set time Td2 of the second timer. For example, if T1>T2, the current reference period T=T2 (S16), otherwise the current reference period T=T1 (S17). Therefore, the MCU can further calculate the set time Td2=T-Tahead of the second timer (S18), and when it detects a rising edge of the waveform of the comparison signal Dim_in, it can start the second timer (S19), and when it detects a falling edge of the waveform of the comparison signal Dim_in, it can start the first timer (S28). When the set time Td2 of the second timer ends (S20: yes), the MCU turns on the bleeder by the control signal Sc (S21). When the set time Td1 of the first timer has elapsed (S22: yes), the MCU turns off the bleeder using a control signal Sc (S23).

[0054] Figure 5 shows the waveforms of the rear cut dimmer performing rear cut control. As can be seen from the waveforms in Figure 5, the same control logic can also be applied to the rear cut dimmer. Figure 6 shows the specific control flow of the MCU.

[0055] FIG. 7 shows a circuit structure of one specific embodiment of the control method of the present invention. In the specific embodiment shown in FIG. 7, the rectifier 26 includes a diode D1 and a diode D2 for rectifying the input voltage of the power converter 27. The input voltage detector 22 includes resistors R2 and R3 connected in series to detect the input voltage of the bleeder and obtain a detection voltage Vt. The bleeder 21 includes a switch tube Q1, a resistor R1, a resistor R6, a resistor R7, a capacitor C1, a diode D3, a triode transistor Q2, a resistor R4, and a resistor R5. The MCU detects the detection voltage Vt and the comparison signal Dim_in to control the bleeder on and off and generate a dimming signal Dim for dimming. The resistors R2 and R3 of the input voltage detector 22 divide the input voltage to obtain the detection voltage Vt and send the detection voltage Vt to the MCU. The comparator 23 generates a comparison signal Dim_in by comparing the detection voltage Vt with a preset reference voltage Vref, and the comparison signal Dim_in is used by the MCU to calculate the magnitude of the phase cut angle and control the bleeder 21. The stable voltage source Vcc generates a stable voltage at the G pole of the switch tube Q1 through resistors R6, R7, capacitor C1 and diode D3. When the control signal Sc output by the MCU is at a low level, the triode transistor Q2 is turned OFF, the switch tube Q1 is turned ON by controlling the driving voltage, and a current flows through the resistor R1. When the current through the resistor R1 increases, the voltage Vgs across the G pole and S pole of the switch tube Q1 decreases due to the action of negative feedback, and finally stabilizes at one fixed value, so that the current through the resistor R1 is a constant value. This current can provide a holding current for the phase cut dimmer 25 of the circuit. When the control signal Sc output by the MCU is at a high level, the triode transistor Q2 is turned on, the driving end of the switch tube Q1 is grounded, the switch tube Q1 is turned off, and no current flows through the resistor R1. Figures 8 and 9 show specific control waveforms for the front cut dimmer and the rear cut dimmer in practical application.

[0056] The advantages of the control method of the present invention are as follows: (1) The input voltage period is sampled in real time, so that it can adapt to the fluctuations of the power grid voltage and frequency, and flicker caused by abnormal control can be avoided. (2) The same control logic can be used simultaneously for the front cut dimmer and the rear cut dimmer, and there is no need to detect whether the connected dimmer is a front cut dimmer or a rear cut dimmer, so that the compatibility is high and the control is simple. (3) The on and off time of the bleeder can be accurately controlled using digital control, so that the control is precise, the circuit loss can be reduced, and the efficiency can be improved. (4) By selecting an appropriate current reference period T, the abnormal situation of the bleeder control sequence caused by the positive and negative half-wave asymmetry of the power grid voltage can be reduced, the detection accuracy of the phase cut angle can be improved, and flicker can be avoided.

[0057] In some embodiments of the present invention, if the connected phase-cut dimmer is a front-cut dimmer as shown in FIG. 10, the current ibleeder flowing through the bleeder can be detected to control the on-off logic of the bleeder. For example, the current ibleeder can be detected by a detection branch circuit including resistor R8 and resistor R9, and the detected current ibleeder is sent to port A5 of the MCU, and FIG. 11 shows a specific control waveform. For a front-cut dimmer, during the period when the input voltage is phase-cut, the bleeder is always in an enabled state, that is, the control signal received by the bleeder is at a high level, but the input voltage is zero, so the detected current ibleeder flowing through the bleeder is also zero. When the input voltage exceeds zero, the detected current ibleeder flowing through the bleeder begins to be greater than zero, so at this time, a first timer is started, and when a set time Td1 (e.g., equal to a first predetermined time) is finished, the bleeder is turned off again. The on-off logic of the bleeder is the same as the previous method.

[0058] The advantages of controlling the bleeder using the control method of the embodiment shown in Figures 10 to 11 are as follows: By directly sampling the bleeder current ibleeder of the bleeder, the MCU can more conveniently and accurately calculate the actual loss of the bleeder, and provide appropriate protection to prevent the bleeder from overheating or being damaged, and further reduce the loss while protecting the circuit. The above-mentioned embodiments are merely illustrative of the present invention, and the present invention is not limited to these embodiments. Note that those skilled in the art may make various modifications and changes to the present invention without departing from the spirit of the present invention, and these modifications and changes are also within the scope of the present invention.

Claims

1. detecting an input voltage of the bleeder to obtain a detected voltage, comparing the detected voltage with a preset reference voltage, and if the detected voltage is less than the preset reference voltage in a first time period, setting a first time as a start point of the first time period and a second time as an end point of the first time period; turning off the bleeder with a delay of a first predetermined time from the second time; detecting a waveform obtained by comparing the detected voltage with the preset reference voltage in real time, starting a second timer when a rising edge of the waveform is detected, and turning on the bleeder when a set time of the second timer ends, thereby bringing forward a second predetermined time from the first time and turning on the bleeder, 11. A method for controlling a bleeder connected to a phase-cut dimmer, wherein the set time of the second timer is equal to a present reference period of the input voltage minus the second predetermined time.

2. 2. The method for controlling a bleeder connected to a phase-cut dimmer according to claim 1, further comprising: generating and sending a low-level control signal to the bleeder in response to turning the bleeder OFF; and generating and sending a high-level control signal to the bleeder in response to turning the bleeder ON.

3. A method for controlling a bleeder connected to a phase-cut dimmer described in claim 1, comprising turning off the bleeder using a first timer different from the second timer.

4. The method includes starting the first timer when a falling edge of the waveform is detected, and turning off the bleeder when a set time of the first timer expires, 4. The method of controlling a bleeder connected to a phase-cut dimmer as claimed in claim 3, wherein the set time of the first timer is equal to the first predetermined time.

5. 5. The method of controlling a bleeder connected to a phase-cut dimmer of claim 4, further comprising determining a current reference period of the input voltage prior to detecting a rising edge of the waveform and starting the second timer.

6. determining a present reference period of the input voltage; 6. A method for controlling a bleeder connected to a phase-cut dimmer as described in claim 5, comprising: determining a first period of the input voltage based on two adjacent rising edges of the waveform; determining a second period of the input voltage based on two adjacent falling edges of the waveform; and comparing the first period with the second period, determining the smaller period as the current reference period of the input voltage.

7. determining the first period of the input voltage; Calculating a current first period based on current captured values ​​of two adjacent rising edges of the waveform by the microcontroller unit; comparing the current first period with a power grid period, and if the current first period is within a normal range of the power grid period, setting the current first period as a first period of the input voltage, and if the current first period is outside the normal range of the power grid period, setting a previous first period as the first period of the input voltage; determining the second period of the input voltage; Calculating, by the microcontroller unit, a current second period based on current captured values ​​of two adjacent falling edges of the waveform; 7. The method for controlling a bleeder connected to a phase-cut dimmer of claim 6, further comprising: comparing the current second period with the power grid period; and if the current second period is within a normal range of the power grid period, setting the current second period as the second period of the input voltage; and if the current second period is outside the normal range of the power grid period, setting a previous second period as the second period of the input voltage.

8. 2. The method for controlling a bleeder connected to a phase-cut dimmer as claimed in claim 1, wherein the phase-cut dimmer is a front-cut dimmer or a rear-cut dimmer.

9. 9. The method for controlling a bleeder connected to a phase-cut dimmer of claim 8, further comprising: controlling the bleeder by detecting a current flowing through the bleeder when the phase-cut dimmer is a front-cut dimmer.

10. In controlling the bleeder by detecting a current flowing through the bleeder, During a time period in which a phase cut process is performed on the input voltage, the bleeder is in an ON state, the input voltage is zero, and the detected current flowing through the bleeder is also zero, 10. The method for controlling a bleeder connected to a phase-cut dimmer of claim 9, further comprising: detecting a current flowing through the bleeder rising from zero when the input voltage exceeds zero; starting a first timer at this time; and delaying the first predetermined time before turning off the bleeder.

11. a bleeder electrically connected to the phase cut dimmer; an input voltage detector that detects an input voltage of the bleeder and acquires the detected voltage; a comparator that generates a comparison signal by comparing the detected voltage with a preset reference voltage, and when the detected voltage is less than the preset reference voltage in a first time period, sets a first time as a start point of the first time period and a second time as an end point of the first time period; a controller that turns off the bleeder by delaying a first predetermined time from the second time based on the detected voltage and the comparison signal, and turns on the bleeder by advancing a second predetermined time from the first time, the controller is configured to include a second timer for turning on the bleeder, detect a waveform obtained by comparing the detected voltage with the preset reference voltage in real time, start the second timer when a rising edge of the waveform is detected, and turn on the bleeder when a set time of the second timer ends; A circuit connected to a phase-cut dimmer, wherein the second timer has a set time equal to a present reference period of the input voltage minus the second predetermined time.

12. 12. The circuit connected to a phase-cut dimmer of claim 11, wherein the controller generates and sends a low level control signal to the bleeder in response to turning the bleeder OFF, and generates and sends a high level control signal to the bleeder in response to turning the bleeder ON.

13. 12. The circuit connected to a phase-cut dimmer of claim 11, wherein the controller further comprises a first timer that turns off the bleeder.

14. the controller is configured to start the first timer when a falling edge of the waveform is detected, and to turn off the bleeder when a set time of the first timer expires; 14. The circuit connected to a phase-cut dimmer of claim 13, wherein the first timer has a set time equal to the first predetermined time.

15. 15. The circuit connected to a phase-cut dimmer of claim 14, wherein the controller further determines a present reference period of the input voltage prior to detecting a rising edge of the waveform and starting the second timer.

16. 16. A circuit connected to a phase-cut dimmer as described in claim 15, wherein, in determining the current reference period of the input voltage, the controller determines a first period of the input voltage based on two adjacent rising edges of the waveform, determines a second period of the input voltage based on two adjacent falling edges of the waveform, and, as a result of comparing the first period and the second period, determines the smaller period as the current reference period of the input voltage.

17. the controller is a microcontroller unit; In determining the first period, the controller Calculating a current first period based on current captured values ​​of two adjacent rising edges of the waveform by the microcontroller unit; comparing the current first period with a power grid period, and setting the current first period as the first period if the current first period is within a normal range of the power grid period, and setting a previous first period as the first period if the current first period is outside the normal range of the power grid period; In determining the second period, the controller Calculating, by the microcontroller unit, a current second period based on current captured values ​​of two adjacent falling edges of the waveform; 17. The circuit connected to a phase-cut dimmer of claim 16, further comprising: comparing the current second period with the power grid period; and setting the current second period as the second period if the current second period is within a normal range of the power grid period; and setting a previous second period as the second period if the current second period is outside the normal range of the power grid period.

18. 12. The circuit connected to a phase-cut dimmer of claim 11, wherein the phase-cut dimmer is a front-cut dimmer or a rear-cut dimmer.

19. 20. The circuit connected to a phase-cut dimmer of claim 18, wherein if the phase-cut dimmer is a front-cut dimmer, the controller controls the bleeder by detecting a current flowing through the bleeder.

20. In controlling the bleeder by detecting a current flowing through the bleeder, the controller During a time period in which a phase cut process is performed on the input voltage, the bleeder is turned on, the input voltage is set to zero, and the detected current flowing through the bleeder is also set to zero; 20. A circuit connected to a phase-cut dimmer as described in claim 19, which detects when the input voltage exceeds zero and detects when the current flowing through the bleeder rises from zero, starts a first timer at this time, and adds the first predetermined time before turning off the bleeder.

21. The circuit connected to a phase-cut dimmer of claim 11 , wherein the comparator and the controller are integrated in a microcontroller unit.

22. Further comprising a rectifier; A circuit connected to a phase-cut dimmer described in any one of claims 11 to 21, wherein the rectifier rectifies the voltage that has been subjected to phase-cut processing by the phase-cut dimmer, and outputs the rectified voltage to the bleeder and the input voltage detector.

23. a power converter for receiving a voltage from the phase-cut dimmer and supplying power to a load; 23. The circuit connected to a phase-cut dimmer of claim 22, wherein the controller determines a dimming signal based on the comparison signal, and the power converter receives the dimming signal and adjusts the brightness of the load.

Images