CN112203381B

CN112203381B - Dimming control circuit and control method thereof

Info

Publication number: CN112203381B
Application number: CN202010917667.3A
Authority: CN
Inventors: 叶美盼
Original assignee: Hangzhou Silan Microelectronics Co Ltd
Current assignee: Hangzhou Silan Microelectronics Co Ltd
Priority date: 2020-09-03
Filing date: 2020-09-03
Publication date: 2023-01-31
Anticipated expiration: 2040-09-03
Also published as: CN112203381A

Abstract

The application discloses dimming control circuit and control method thereof, wherein, dimming control circuit includes: an excitation conversion circuit for generating an excitation signal; the primary winding of the isolation circuit is connected with the excitation conversion circuit, receives the excitation signal and transmits the excitation signal to the secondary winding of the isolation circuit; the input end of the rectifying circuit is connected with the secondary winding of the isolating circuit, and the output end of the rectifying circuit is connected with the light modulator; the excitation conversion circuit comprises an excitation module, the excitation module comprises a power supply voltage and a first current source, the first end of a primary winding of the isolation circuit receives the power supply voltage, and the first current source is connected between the second end of the primary winding of the isolation circuit and a first grounding end to generate an excitation signal. The constant current source is adopted to generate the excitation signal, the power can be stably supplied to the light modulator, and the circuit structure is simple and low in cost.

Description

Dimming control circuit and control method thereof

Technical Field

The present invention relates to power electronics technologies, and more particularly, to a dimming control circuit and a control method thereof.

Background

In a conventional 0-10V isolation dimming control circuit, an external 0-10V voltage signal is usually converted into a corresponding PWM signal through a triangular wave generator, a complex analog circuit such as PWM (pulse width modulation) adjustment, or an external 0-10V voltage signal is converted into a corresponding control signal by using a single chip microcomputer technology, and then the control signal is transmitted to a dimming pin of a primary main control chip through an isolation photocoupler to adjust the current input to an LED. After the external 0-10V voltage signal is adjusted and converted into a control signal by adopting a single chip microcomputer technology or conventional analog PWM, the control signal is transmitted to a primary main control chip through an isolation photoelectric coupler, and the whole circuit is complex and high in cost.

When the 0-10V dimmer is a passive dimmer, a power supply is required to supply power to the dimmer, and the dimmer is usually supplied with power by adding a winding to a main transformer so as to meet the isolation requirement. The existing dimming control circuit is complex in circuit and high in cost.

Disclosure of Invention

In view of the above problems, it is an object of the present invention to provide a dimming control circuit and a control method thereof, in which an excitation signal of a primary winding is transmitted to a secondary winding through an isolation circuit for transmitting a dimming signal to supply power to a dimmer, the circuit is simple and the cost is low; and a constant current source is adopted to generate an excitation signal so as to output stable current to supply power to the dimmer.

According to an aspect of the present invention, there is provided a dimming control circuit comprising: an excitation conversion circuit for generating an excitation signal; the primary winding of the isolation circuit is connected with the excitation conversion circuit, receives an excitation signal and transmits the excitation signal to the secondary winding of the isolation circuit; the input end of the rectifying circuit is connected with the secondary winding of the isolating circuit, and the output end of the rectifying circuit is connected with the dimmer; the excitation conversion circuit comprises an excitation module, the excitation module comprises a power supply voltage and a first current source, the first end of a primary winding of the isolation circuit receives the power supply voltage, and the first current source is connected between the second end of the primary winding of the isolation circuit and a first grounding end to generate the excitation signal; and the secondary winding of the isolation circuit receives the dimming signal generated by the dimmer through the rectification circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit.

Preferably, the isolation circuit transmits the excitation signal from a primary side to a secondary side, and the excitation signal is rectified by the rectifier circuit and then supplies power to the dimmer.

Preferably, the excitation signal is a pulsed current signal.

Preferably, the excitation converting circuit further includes: the detection module is connected with the first end of the first current source and is used for detecting the voltage of the second end of the primary winding of the isolation circuit during the invalid period of the excitation signal so as to obtain a dimming voltage signal; and the conversion module is respectively connected with the detection module and the first end of the primary winding of the isolation circuit and converts the dimming voltage signal into a dimming reference signal.

Preferably, the excitation converting circuit further includes a compensation module, connected between the excitation module and the second end of the primary winding of the isolation circuit, for compensating the dimming voltage signal.

Preferably, the detection module includes a first switch, a first resistor, and a first capacitor, the first switch, the first resistor, and the first capacitor are connected in series between the first end of the first current source and the first ground terminal, and a node between the first resistor and the first capacitor outputs the dimming voltage signal.

Preferably, the first switch is turned on during a period when the activation signal is inactive.

Preferably, the conversion module includes a first end, a second end and an output end, and the first end of the conversion module is connected to the first end of the primary winding of the isolation circuit; the second end of the conversion module is connected with the detection module and receives the dimming voltage signal; and the output end of the conversion module outputs a dimming reference signal.

Preferably, the compensation module includes a seventh diode and a third resistor, an anode of the seventh diode is connected to the second end of the primary winding of the isolation circuit, and a cathode of the seventh diode is connected to the first end of the first current source; the third resistor is connected between the first terminal of the first current source and the first ground terminal.

Preferably, the compensation module comprises a seventh diode, an eighth diode and a third resistor, and the seventh diode and the eighth diode are connected in series between the second end of the primary winding of the isolation circuit and the first end of the first current source; the anode of the eighth diode is connected with the second end of the primary winding of the isolation circuit, and the cathode of the eighth diode is connected with the anode of the seventh diode; the cathode of the seventh diode is connected with the first end of the first current source; the third resistor is connected between the first terminal of the first current source and the ground terminal.

Preferably, the dimming reference signal VDIM = VD _ S-VCC, where VCC is a power supply voltage, and VD _ S is a dimming voltage signal.

Preferably, the excitation converting circuit further includes: the detection module is connected with the second end of the primary winding of the isolation circuit and is used for detecting voltage signals at two ends of the primary winding of the isolation circuit in the effective period of the excitation signal so as to obtain a dimming voltage signal; and the conversion module is connected with the detection module and the first end of the secondary winding of the isolation circuit and converts the dimming voltage signal into a dimming reference signal.

Preferably, the detection module includes a first switch and a first capacitor, the first switch and the first capacitor are connected in series between the second end of the primary winding and the first ground terminal, and a node between the first switch and the first capacitor outputs the dimming voltage signal.

Preferably, the first switch is turned on during the active period of the excitation signal.

Preferably, the excitation converting circuit further includes: the compensation module is connected with the conversion module and used for outputting a first bias voltage; wherein the first bias voltage is used for compensating the dimming voltage signal.

Preferably, the compensation module comprises a second current source and a thermistor, wherein the second current source and the thermistor are connected in series between a first end of a primary winding of the isolation circuit and a first ground end; a node between the second current source and the thermistor outputs a first bias voltage.

Preferably, the compensation module comprises a twelfth pole tube, an anode of the twelfth pole tube is connected with the second end of the first current source, a cathode of the twelfth pole tube is connected with the first ground terminal, and the voltage across the twelfth pole tube is the first bias voltage.

Preferably, the conversion module comprises a first end, a third end and an output end, wherein the first end of the conversion module is connected with the first end of the primary winding; the second end of the conversion module is connected with the detection module and receives the dimming voltage signal; the third end of the conversion module is connected with the compensation module and receives a first bias voltage; the conversion module obtains a dimming reference signal according to the dimming voltage signal, the power supply voltage and the first bias voltage, and the output end outputs the dimming reference signal.

Preferably, the compensation module includes an eleventh diode and a fifth resistor, an anode of the eleventh diode is connected to the second end of the primary winding of the isolation circuit, and a cathode of the eleventh diode is connected to the first end of the first current source; the fifth resistor is connected between the cathode of the eleventh diode and the first ground terminal.

Preferably, the conversion module includes a first end, a second end and an output end, and the first end of the conversion module is connected to the first end of the primary winding of the isolation circuit; the second end of the conversion module is connected with the detection module and receives the dimming voltage signal; the conversion module obtains a dimming reference signal according to the dimming voltage signal and the power voltage, and the output end outputs the dimming reference signal.

Preferably, the secondary winding of the isolation circuit comprises a first secondary winding and a second secondary winding; wherein the second end of the first secondary winding and the first end of the second secondary winding are shorted; the first end of the first secondary winding is a homonymous end, and the second end of the first secondary winding is a heteronymous end; the first end of the second secondary winding is a homonymous end, and the second end of the second secondary winding is a heteronymous end; the turn ratio of the number of turns of the primary winding of the isolation circuit to the number of turns of the first secondary winding to the number of turns of the second secondary winding is n:1, and n is a positive number.

Preferably, the turn ratio of the number of turns of the primary winding of the isolation circuit to the number of turns of the secondary winding is n:1, n is a positive number.

Preferably, the rectifying circuit comprises a first diode and a second diode, wherein an anode of the first diode is connected with a first end of the first secondary winding, a cathode of the first diode is connected with a cathode of the second diode, and an anode of the second diode is connected with a second end of the second secondary winding.

Preferably, the rectifying circuit comprises a third diode to a sixth diode, the anode of the third diode is connected with the first end of the secondary winding, and the cathode of the third diode is connected with the cathode of the fifth diode; the cathode of the fourth diode is connected with the first end of the secondary winding, and the anode of the fourth diode is connected with the second grounding end; the anode of the fifth diode is connected with the second end of the secondary winding; and the cathode of the sixth diode is connected with the second end of the secondary winding, and the anode of the sixth diode is connected with the second grounding end.

Preferably, the rectifying circuit comprises a ninth diode and a voltage regulator tube, wherein the anode of the ninth diode is connected with the first end of the secondary winding of the isolating circuit, and the cathode of the ninth diode is connected with the first end of the dimmer; and the voltage-stabilizing tube is connected between two ends of the secondary winding of the isolation circuit.

Preferably, the dimming control circuit further comprises: and the filter circuit is connected between the rectifying circuit and the light modulator and is used for filtering the rectified excitation signal.

Preferably, a first end of the dimmer is connected to a first output end of the rectifying circuit, and a second end of the dimmer is connected to a second end of the first secondary winding.

Preferably, a first end of the dimmer is connected to a first output end of the rectifying circuit, and a second end of the dimmer is connected to a second output end of the rectifying circuit.

Preferably, the dimming reference signal VDIM = VCC-VD _ S-Vt-Vr, where VCC is a power supply voltage, VD _ S is a dimming voltage signal, vt is a first bias voltage representing a voltage drop across the rectifying circuit, and Vr is a second bias voltage representing a voltage drop across the filtering circuit.

Preferably, the dimming reference signal VDIM =2vd _s1-VD _ S2-VCC-Vr, where VCC is a power supply voltage, VD _ S1 is a dimming voltage signal during an active period of the excitation signal, VD _ S2 is a dimming voltage signal during an inactive period of the excitation signal, and Vr is a second bias voltage, which represents a voltage drop across the filter circuit.

Preferably, the isolation circuit is a transformer.

According to another aspect of the present invention, there is provided a dimming control method for a dimming control circuit including at least an isolation circuit, the dimming control method comprising: generating an excitation signal at a primary winding of the isolation circuit by adopting a first current source; transmitting the excitation signal from a primary winding of the isolation circuit to a secondary winding; rectifying the excitation signal and supplying power to a dimmer; and the secondary winding of the isolation circuit receives a dimming signal generated by a dimmer and generates a dimming reference signal representing the dimming signal at two ends of the primary winding of the isolation circuit.

Preferably, the excitation signal is a pulsed current signal.

Preferably, when a primary winding of the isolation circuit generates current, the isolation circuit transmits the excitation signal from the primary side to the secondary side, and supplies power to the dimmer after rectification; when no current is generated in the primary winding of the isolation circuit, the secondary winding of the isolation circuit receives the dimming signal, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit.

Preferably, when a current is generated in the primary winding of the isolation circuit, the isolation circuit transmits the excitation signal from the primary side to the secondary side, and supplies power to the dimmer after rectification, and meanwhile, the secondary winding of the isolation circuit receives the dimming signal and generates a dimming reference signal representing the dimming signal at two ends of the primary winding of the isolation circuit.

The dimming control method further includes: the rectified excitation signal is filtered.

According to the dimming control circuit and the dimming control method of the embodiment of the invention, the excitation module comprises a power supply voltage and a first current source, wherein the first end of the primary winding of the isolation circuit receives the power supply voltage, and the first current source is connected between the second end of the primary winding of the isolation circuit and the first grounding end to generate the excitation signal. The dimming control circuit provided by the embodiment of the invention adopts the constant current source to generate the excitation signal, and can provide stable power supply current for the dimmer.

Further, the isolation circuit transmits an excitation signal from the primary winding to the secondary winding, and the rectifier circuit rectifies the excitation signal and then supplies power to the light modulator; and the secondary winding of the isolation circuit receives the dimming signal generated by the dimmer through the rectifying circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit. The dimming control circuit of the embodiment of the invention does not relate to a complex singlechip technology or a conventional analog PWM adjusting circuit, and the whole circuit has simple structure and low cost.

Further, when a primary winding of the isolation circuit generates current, the isolation circuit transmits the pulse current signal from the primary side to the secondary side, and the pulse current signal is rectified by the rectification circuit and then supplies power to the dimmer; when no current is generated in the primary winding of the isolation circuit, the secondary winding of the isolation circuit receives the dimming signal through the rectification circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit. The accurate isolation transmission of the dimming signal can be realized, stable and accurate power supply is provided for the dimmer, the circuit is simple to realize, and the cost is low.

Further, when a primary winding of the isolation circuit generates current, the isolation circuit transmits the pulse current signal from the primary side to the secondary side, the pulse current signal is rectified by the rectification circuit and then supplies power to the dimmer, meanwhile, the secondary winding of the isolation circuit receives the dimming signal through the rectification circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit. The dimming signal is detected while power is supplied, and the waveform of the dimming signal is not easily distorted.

Furthermore, a transformer is adopted to isolate transmission, so that the cost is low.

Further, the dimmer can be supplied with constant current, and the constant current of the dimmer is only related to the peak value, the duty ratio and the turn ratio of the excitation signal and is not related to the inductance of the transformer.

Furthermore, a compensation module is adopted in the excitation conversion circuit to perform voltage drop compensation on a voltage drop of a diode in a secondary winding rectifying circuit of the isolation circuit, so that a more accurate dimming reference signal can be obtained.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

fig. 1 shows a circuit schematic of a dimming control circuit according to an embodiment of the present invention.

Fig. 2 shows a schematic block diagram of a dimming control circuit according to a first embodiment of the present invention.

Fig. 3 illustrates a signal waveform diagram of a dimming control circuit according to a first embodiment of the present invention.

Fig. 4 shows a schematic block diagram of a dimming control circuit according to a second embodiment of the present invention.

Fig. 5 shows a schematic block diagram of a dimming control circuit according to a third embodiment of the present invention.

Fig. 6 shows a schematic block diagram of a dimming control circuit according to a fourth embodiment of the present invention.

Fig. 7 shows a schematic block diagram of a dimming control circuit according to a fifth embodiment of the present invention.

Fig. 8 is a signal waveform diagram illustrating a dimming control circuit according to a fifth embodiment of the present invention.

Fig. 9 shows a schematic block diagram of a dimming control circuit according to a sixth embodiment of the present invention.

Fig. 10 shows a schematic block diagram of a dimming control circuit according to a seventh embodiment of the present invention.

Fig. 11 shows a signal waveform diagram of a dimming control circuit according to a seventh embodiment of the present invention.

Fig. 12 shows a flowchart of a dimming control method according to an embodiment of the present invention.

Detailed Description

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In the various figures, like elements are identified with the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples.

Fig. 1 shows a schematic circuit diagram of a dimming control circuit according to an embodiment of the present invention. The dimming control circuit 100 generates an excitation signal to supply power to the dimmer 200 and converts a 0-10V dimming signal generated by the dimmer 200 into a dimming reference signal VDIM that is representative of the dimming signal.

As shown in fig. 1, the dimming control circuit 100 includes an excitation converting circuit 110, an isolating circuit 120, and a rectifying circuit 130.

Wherein the excitation converting circuit 110 generates an excitation signal Ip. The isolation circuit 120 includes a primary winding and a secondary winding, and the primary winding of the isolation circuit 120 is connected to the excitation conversion circuit 110, receives the excitation signal Ip, and transmits the excitation signal Ip to the secondary winding of the isolation circuit 120. The input end of the rectifying circuit 130 is connected to the secondary winding of the isolation circuit 120, and the output end of the rectifying circuit 130 is connected to the dimmer 300. The rectifier circuit 130 rectifies the excitation signal Ip and outputs a supply current Io, thereby supplying power to the dimmer 200. The secondary winding of the isolation circuit 120 receives the dimming signal generated by the dimmer 200 through the rectification circuit 120, and generates a dimming reference signal VDIM representing the dimming signal at two ends of the primary winding of the isolation circuit 120.

In this embodiment, when a current is generated in the primary winding of the isolation circuit 120, the isolation circuit 120 transmits the excitation signal Ip from the primary side to the secondary side, and supplies power to the dimmer 200 after being rectified by the rectification circuit 130; when no current is generated in the primary winding of the isolation circuit 120, the secondary winding of the isolation circuit 120 receives the dimming signal through the rectification circuit 130, and a dimming reference signal VDIM representing the dimming signal is generated at two ends of the primary winding of the isolation circuit 120.

In a preferred embodiment, when the primary winding of the isolation circuit 120 generates current, the isolation circuit 120 transmits the excitation signal Ip from the primary side to the secondary side, and supplies power to the dimmer 200 after being rectified by the rectification circuit 130, and the secondary winding of the isolation circuit 120 receives the dimming signal through the rectification circuit 130, so as to generate a dimming reference signal VDIM representing the dimming signal across the primary winding of the isolation circuit 120.

In a preferred embodiment, the dimming control circuit 100 further includes a filter circuit 140 connected between the rectifying circuit and the dimmer for filtering the rectified driving signal Ip and then outputting a supply current Io to supply power to the dimmer.

Fig. 2 shows a schematic block diagram of a dimming control circuit according to a first embodiment of the present invention. As shown in fig. 2, the isolation circuit 120 is a transformer T1, a primary winding of the isolation circuit 120 is connected to the excitation conversion circuit 110, and a secondary winding of the transformer T1 is connected to the rectification circuit 130.

In this embodiment, when a current is generated in the primary winding of the isolation circuit 120, the isolation circuit 120 transmits an excitation signal Ip from the primary winding to the secondary winding, and supplies power to the dimmer 200 after being rectified by the rectification circuit 130; when no current is generated in the primary winding of the isolation circuit 120, the secondary winding of the isolation circuit 120 receives the dimming signal through the rectification circuit 130, and a dimming reference signal VDIM representing the dimming signal is generated at two ends of the primary winding of the isolation circuit 120.

Referring to fig. 2, the excitation converting circuit 110 includes an excitation module 111, a detection module 112 and a conversion module 113, wherein the excitation module 111 is connected to the primary winding of the isolation circuit 120 to generate an excitation signal Ip; the detection module 112 is connected to the second end of the primary winding of the isolation circuit 120, and detects a voltage signal of the second end of the primary winding of the isolation circuit 120 during the period when the excitation signal Ip is inactive (Ip = 0) to obtain the dimming voltage signal VD _ s. A conversion module 113, connected to the detection module 112 and the first end of the primary winding of the isolation circuit 120, for converting the dimming voltage signal VD _ s into a dimming reference signal VDIM.

In this embodiment, as shown in fig. 2, the excitation module 111 includes a first current source I1 and a power supply voltage VCC, the first end of the primary winding receives the power supply voltage VCC, and the first current source I1 is connected between the second end of the primary winding and a first ground GND.

Specifically, a first end of the primary winding is connected to a supply voltage VCC. A first end of the first current source I1 is connected to the second end of the primary winding, and a second end of the first current source I1 is connected to a first ground GND.

The first current source I1 generates an excitation signal Ip, which is a pulse current signal having a period T, a peak value Ipk, and a pulse width Ton. The excitation signal Ip flows from VCC, through the primary winding of the transformer T1, into the first current source I1, and further into the primary ground.

The detection module 112 includes a first switch S1, a first resistor R1, and a first capacitor C1, where the first switch S1, the first resistor R1, and the first capacitor C1 are connected in series between a second end of the primary winding of the isolation circuit 120 and a first ground GND, and a node between the first resistor R1 and the first capacitor C1 outputs a dimming voltage signal VD _ S. The control terminal of the first switch S1 receives the control signal DR. The control signal DR may be generated by a simple oscillator or timer, and the timing of the control signal DR is matched to the timing of the excitation signal Ip. Under the control of the control signal DR, the first switch S1 is turned on during the period when the excitation signal Ip is inactive (i.e., when the current Ip =0 generated by the first current source I1). The detection module 112 detects a voltage signal VD at the second end of the primary winding of the isolation circuit 120, and outputs a dimming voltage signal VD _ s through filtering of the first resistor R1 and the first capacitor C1.

The conversion module 113 comprises a first end, a second end and an output end, wherein the first end of the conversion module 113 is connected with the first end of the primary winding of the isolation circuit 120; a second end of the conversion module 113 is connected to the detection module 112, and receives the dimming voltage signal VD _ s; the output terminal of the conversion module 113 outputs a dimming reference signal VDIM. Wherein VDIM = VD _ s-VCC. The dimming reference signal VDIM is finally given to the main control chip. And the main control chip realizes the dimming of the lamp load according to the dimming reference signal VDIM.

The secondary windings of the isolation circuit 120 include a first secondary winding and a second secondary winding; wherein the second end of the first secondary winding and the first end of the second secondary winding are short-circuited, and the turn ratio of the number of turns of the primary winding of the isolation circuit 120, the number of turns of the first secondary winding, and the number of turns of the second secondary winding is n:1, where n is a positive number. The first end of the primary winding of the isolation circuit 120 is a homonymous end, and the second end is a heteronymous end. The first end of the first secondary winding is a homonymous end, and the second end of the first secondary winding is a synonym end. The first end of the second secondary winding is a homonymous end, and the second end of the second secondary winding is a heteronymous end.

In this embodiment, a first terminal of the dimmer 200 is connected to the first output terminal of the rectifying circuit 130, and a second terminal of the dimmer 200 is connected to the second terminal of the first secondary winding and to the second ground terminal.

The rectifying circuit 130 is a single-phase full-wave rectifying circuit. The rectifying circuit 130 includes a first diode D1 and a second diode D2, an anode of the first diode D1 is connected to a first end of the first secondary winding, a cathode of the first diode D1 is connected to a cathode of the second diode D2, and an anode of the second diode D2 is connected to a second end of the second secondary winding.

In this embodiment, the excitation signal Ip is a pulse current signal, which is a rectangular wave with a period T, a peak value Ipk, and a pulse width Ton. During the active period (Ton period) of the excitation signal Ip, the excitation signal Ip = Ipk, which is transmitted from the primary winding to the secondary winding by the isolation circuit 120 and rectified to generate the supply current Io for supplying the dimmer 200.

During the period that the excitation signal Ip is invalid, the excitation signal Ip =0, the secondary winding of the isolation circuit 120 receives the dimming signal generated by the dimmer 200 through the rectification circuit 130, and a dimming voltage signal VD _ s representing the dimming signal is generated across the primary winding of the isolation circuit 120; the excitation conversion circuit 110 converts the dimming voltage signal VD _ s to output a dimming reference signal VDIM.

Fig. 3 illustrates a signal waveform diagram of a dimming control circuit according to a first embodiment of the present invention. As shown in fig. 3, during a period from T0 to T1, that is, during an effective Ton of an excitation signal Ip, the first current source I1 generates an excitation signal Ip with a peak value Ipk, the excitation signal Ip flows through a primary winding of the transformer T1, due to an electromagnetic induction principle, an induced voltage is generated at the primary winding of the transformer T1, a dotted terminal and a non-dotted terminal of the primary winding of the transformer T1 have polarities positive and negative, an excitation inductor (not shown in the figure) of the transformer T1 excites, and an excitation current I _ Lm rises linearly. An induced current with a value of (Ipk-I _ Lm) × n is proportionally generated in the secondary winding of the transformer T1, and the polarity is that the induced current flows in from the different name end and flows out from the same name end of the first secondary winding.

During a period from T1 to T4, the first current source I1 generates an excitation signal Ip =0, the excitation inductor of the transformer T1 is demagnetized, an induced current is generated in the second secondary winding of the transformer T1, the polarity of the induced current is that the induced current flows in from the dotted terminal and flows out from the dotted terminal of the second secondary winding, an induced voltage is generated on the primary winding of the transformer T1, and the polarity of the induced voltage is that the dotted terminal of the primary winding of the transformer T1 is negative and the dotted terminal is positive.

During a period from T2 to T3, the first switch S1 is turned on, and the detection module 112 detects a voltage signal VD at the second end of the primary winding of the transformer T1 (i.e., the synonym end of the primary winding of the transformer T1) during the period, so as to generate a dimming voltage signal VD _ S.

During the period from T4 to T5, the demagnetization of the excitation inductance of the transformer T1 is finished, and parasitic oscillation occurs. At time t5, the first current source I1 again generates the excitation signal Ip with a peak value Ipk, and enters the next cycle.

During the whole period T0-T5, D = Ton/T, the output supply current Io = (Ipk) × n × D.

In a preferred embodiment, the filter circuit 140 includes a second resistor R2 and a second capacitor C2, the second resistor R2 is connected between the cathode of the first diode D1 and the first terminal of the dimmer 200; the second capacitor C2 is connected between the cathode of the first diode D1 and the second terminal of the dimmer 200, and is also connected between the cathode of the first diode D1 and the second terminal of the first secondary winding.

Fig. 4 shows a schematic block diagram of a dimming control circuit according to a second embodiment of the present invention. In contrast to the first embodiment shown in fig. 2, the isolation circuit 120 includes a primary winding and a secondary winding; the turn ratio of the number of turns of the primary winding of the isolation circuit 120 to the number of turns of the secondary winding is n:1, n is a positive number. The rectifier circuit 130 is a single-phase bridge rectifier circuit.

In the present embodiment, the first terminal of the dimmer 200 is connected to the first output terminal of the rectifying circuit 130, and the second terminal is connected to the second output terminal of the rectifying circuit 130.

In this embodiment, the rectifying circuit 130 includes third to sixth diodes (D3-D6), an anode of the third diode D3 is connected to the first end of the secondary winding, and a cathode is connected to a cathode of the fifth diode D5; the cathode of the fourth diode D4 is connected with the first end of the secondary winding, and the anode of the fourth diode D4 is connected with the second grounding end; the anode of the fifth diode D5 is connected to the second end of the secondary winding, and the cathode is connected to the filter circuit 140; the cathode of the sixth diode D6 is connected to the second end of the secondary winding, and the anode is connected to the second ground terminal.

The filter circuit 140 includes a second resistor R2 and a second capacitor C2, wherein the second resistor R2 is connected between the cathode of the third diode D3 and the first end of the dimmer 200; the second capacitor C2 is connected between the cathode of the third diode D3 and the second terminal of the dimmer 200, and is also connected between the cathode of the third diode D3 and the anode of the fourth diode D4.

Other aspects of the second embodiment of the present invention are the same as those of the first embodiment of the present invention, and are not described herein again.

Fig. 5 shows a schematic block diagram of a dimming control circuit according to a third embodiment of the present invention. Compared with the first embodiment shown in fig. 2, the excitation converting circuit 110 further includes a compensation module 114 connected between the excitation module 111 and the second end of the primary winding of the isolation circuit 120, and configured to compensate the dimming voltage signal VD _ s.

In this embodiment, the compensation module 114 includes a seventh diode D7 and a third resistor R3, an anode of the seventh diode D7 is connected to the second end of the primary winding of the isolation circuit 120, and a cathode thereof is connected to the first end of the first current source I1; the third resistor R3 is connected between the first terminal of the first current source I1 and the first ground GND.

In this embodiment, the detection module 112 detects that the detection signal VD _ s is lower than the voltage across the first secondary winding of the isolation circuit 120 by a forward voltage drop of the seventh diode D7. Preferably, the seventh diode D7 is the same type as the first diode D1 constituting the rectifying circuit 130, so as to compensate for an error caused by the rectifying circuit 130 in the dimming signal detection.

Further, the third resistor R3 can be adjusted in size to adjust the current flowing through the seventh diode D7, so as to fine-tune the compensation voltage.

Other aspects of the third embodiment of the present invention are the same as those of the first embodiment of the present invention, and are not described herein again.

Fig. 6 shows a schematic block diagram of a dimming control circuit according to a fourth embodiment of the present invention. Compared with the second embodiment shown in fig. 4, the excitation converting circuit 110 further includes a compensation module 114 connected between the excitation module 111 and the second end of the primary winding of the isolation circuit 120, and configured to compensate the dimming voltage signal VD _ s.

In this embodiment, the compensation module 114 includes a seventh diode D7, an eighth diode D8 and a third resistor R3, and the seventh diode D7 and the eighth diode D8 are connected in series between the second end of the primary winding of the isolation circuit 120 (i.e., the second end of the primary winding of the transformer T1) and the first end of the first current source I1. The third resistor R3 is connected between the first terminal of the first current source I1 and the first ground GND.

Specifically, the anode of the eighth diode D8 is connected to the second end of the primary winding of the isolation circuit 120, and the cathode is connected to the anode of the seventh diode D7; the cathode of the seventh diode D7 is connected to the first terminal of the first current source I1.

In this embodiment, the detection module 112 detects that the detection signal VD _ s is lower than the voltage across the secondary winding of the isolation circuit 120 by the forward voltage drop of the seventh diode D7 and the eighth diode D8. Preferably, the seventh diode D7 and the eighth diode D8 are the same as the first diode D3 constituting the rectifying circuit 130, so as to compensate for an error caused by the rectifying circuit 130 in the dimming signal detection.

Further, the magnitude of the third resistor R3 may be adjusted to adjust the current flowing through the seventh diode D7 and the eighth diode D8 to fine-tune the compensation voltage.

Other aspects of the fourth embodiment of the present invention are the same as those of the second embodiment of the present invention, and are not described herein again.

According to the dimming control circuit provided by the embodiment of the invention, the isolation circuit transmits an excitation signal from the primary winding to the secondary winding, and the rectifying circuit rectifies the excitation signal and then supplies power to the dimmer; and the secondary winding of the isolation circuit receives the dimming signal generated by the dimmer through the rectifying circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit. The dimming control circuit of the embodiment of the invention does not relate to a complex singlechip technology or a conventional analog PWM adjusting circuit, and the whole circuit has simple structure and low cost.

Further, a current source is adopted to generate a pulse current signal, so that constant current can be supplied to the dimmer, and the constant current of the dimmer is only related to the peak value, the duty ratio and the turn ratio of the excitation signal and is not related to inductance.

Further, when a primary winding of the isolation circuit generates current (i.e., during an active period of an excitation signal), the isolation circuit works in a forward converter state, stores energy, transmits the pulse current signal from the primary side to the secondary side, and supplies power to the dimmer after the pulse current signal is rectified by the rectification circuit. When no current is generated in the primary winding of the isolation circuit (namely during the period that the excitation signal is invalid), the isolation circuit works in a flyback converter state, the energy storage of the isolation circuit is released, the isolation circuit supplies power to a dimmer, meanwhile, the secondary winding of the isolation circuit receives the dimming signal through the rectification circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit.

Fig. 7 shows a schematic block diagram of a dimming control circuit according to a fifth embodiment of the present invention. Compared with the second embodiment shown in fig. 2, the isolation circuit 120 includes a primary winding and a secondary winding, the excitation conversion circuit further includes a compensation module 114 connected between a first end of the primary winding of the isolation circuit 120 and a first ground GND, and the detection module 112 detects a voltage signal at a second end of the primary winding of the isolation circuit 120 during an active period of the excitation signal Ip to obtain the dimming voltage signal VD _ s.

In this embodiment, the turn ratio of the number of turns of the primary winding to the number of turns of the secondary winding of the isolation circuit 120 is n:1, where n is a positive number, a first end of the primary winding is a homonymous end, and a second end of the primary winding is a heteronymous end; the first end of the secondary winding is a homonymous end, and the second end of the secondary winding is a synonym end.

In the present embodiment, the first terminal of the dimmer 200 is connected to the first output terminal of the rectifying circuit 130, and the second terminal is connected to the second terminal of the secondary winding.

In this embodiment, when a current is generated in the primary winding of the isolation circuit 120, the isolation circuit 120 transmits the pulse current signal from the primary side to the secondary side, and supplies power to the dimmer 200 after being rectified by the rectification circuit 130; when no current is generated in the primary winding of the isolation circuit 120, the secondary winding of the isolation circuit 120 receives the dimming signal through the rectification circuit 130, and a dimming reference signal VDIM representing the dimming signal is generated at two ends of the primary winding of the isolation circuit 120.

In this embodiment, the detection module 112 includes a first switch S1 and a first capacitor C1, the first switch S1 and the first capacitor C1 are connected in series between the second end of the primary winding of the isolation circuit 120 and the first ground GND, and a node between the first switch S1 and the first capacitor C1 outputs the dimming voltage signal VD _ S. The control terminal of the first switch S1 receives the control signal DR. The control signal DR may be generated by a simple oscillator or timer, and the timing of the control signal DR is matched to the timing of the excitation signal Ip. Under the control of the control signal DR, the first switch S1 is turned on during the active period of the excitation signal Ip (i.e., when the current Ip = Ipk generated by the first current source I1). The detection module 112 detects a voltage signal VD at the second end of the primary winding of the isolation circuit 120, and outputs a dimming voltage signal VD _ s through filtering by the first capacitor C1.

The compensation module 114 includes a second current source I2 and a thermistor R4, and the second current source I2 and the thermistor R4 are connected in series between the first end of the primary winding of the isolation circuit 120 and the first ground GND.

The conversion module 113 comprises a first end, a third end and an output end, wherein the first end of the conversion module 113 is connected with the first end of the primary winding of the isolation circuit 120 and the power supply voltage to receive the power supply voltage VCC; a second terminal of the conversion module 113 is connected to the detection module 112 and receives the dimming voltage signal VD _ s, and a third terminal of the conversion module 113 is connected to the compensation module 114, is connected to a node between the second current source I2 and the thermistor R4, and receives a first bias voltage Vt; the output terminal of the conversion module 113 outputs a dimming reference signal VDIM.

In this embodiment, the rectifying circuit includes a ninth diode D9 and a zener diode Z1, and the ninth diode D9 is connected between the first end of the secondary winding of the isolation circuit 120 and the first end of the dimmer 200; the zener tube Z1 is connected between the first and second ends of the secondary winding of the isolation circuit 120.

In the present embodiment, the anode of the ninth diode D9 is connected to the first end of the secondary winding of the isolation circuit 120, and the cathode of the ninth diode D9 is connected to the first end of the dimmer 200.

In a preferred embodiment, the dimming control circuit further includes a filter circuit 140 connected between the rectifying circuit 130 and the dimmer 200.

In this embodiment, the filter circuit includes a second resistor R2 and a second capacitor C2, and the second resistor R2 is connected between the cathode of the ninth diode D9 and the first end of the dimmer 200; a second capacitor C2 is connected between the cathode of the ninth diode D9 and the second terminal of the dimmer 200, and is also connected between the cathode of the ninth diode D9 and the second terminal of the secondary winding.

The second current source I2 generates a certain current to the thermistor R4, and the voltage Vt across the thermistor R4 can represent the voltage across the ninth diode D9 in the rectifying circuit 130, i.e. the first bias voltage. Since the voltage across the ninth diode D9 is different at different temperatures of the ninth diode D9, the voltage across the ninth diode D9 is simulated by multiplying the current generated by the second current source I2 by the thermistor R4. The voltage Vr across the second resistor R2 in the filter circuit 140, i.e., the second bias voltage, may be obtained by a product of the supply current Io output by the filter circuit 140 and the second resistor R2, i.e., vr = Io × R2. The dimming reference signal VDIM = VCC-VD _ s-Vt-Vr obtained by the conversion module 113. The dimming reference signal VDIM is finally sent to the main control chip, and the main control chip controls the lamp load according to the dimming reference signal VDIM to realize dimming of the lamp load.

Fig. 8 is a signal waveform diagram of a dimming control circuit according to a fifth embodiment of the present invention. As shown in fig. 8, during a period from T0 to T1, that is, during an effective period (Ton period) of an excitation signal Ip, the first current source I1 generates the excitation signal Ip with a peak value Ipk, the excitation signal Ip flows through the primary winding of the transformer T1, an induced voltage is generated on the primary winding of the transformer T1 due to an electromagnetic induction principle, a polarity of a same-name end of the primary winding of the transformer T1 is positive, a polarity of a different-name end of the primary winding of the transformer T1 is negative, an excitation inductance (not shown in the figure) of the transformer T1 excites, and an excitation current I _ Lm linearly increases. An induced current of (Ipk-I _ Lm) × n is generated in proportion in the secondary winding of the transformer T1, and the polarity is such that the induced current flows in from the different-name end and flows out from the same-name end of the secondary winding.

Meanwhile, during the period from T0 to T1, the first switch S1 is turned on, and the detection module 112 detects the voltage signal VD at the synonym terminal of the primary winding of the transformer T1 during this period to generate the dimming voltage signal VD _ S.

During a period from T1 to T2, an excitation signal Ip generated by the first current source I1 is 0, the excitation inductance of the transformer T1 is demagnetized, an induced current is generated in the secondary winding of the transformer T1, the polarity of the induced current is that the induced current flows in from the dotted terminal and flows out from the synonym terminal of the secondary winding, an induced voltage is generated in the primary winding of the transformer T1, the polarity of the induced voltage is that the dotted terminal of the primary winding of the transformer T1 is negative and the synonym terminal is positive, and the time is long enough until the demagnetization of the excitation inductance is finished.

During the whole period T0-T2, D = Ton/T, the supply current Io = (Ipk-I _ Lm) × n = (ip =) (Vr = Io × R2), I _ Lm = (Vo + Vr + Vt) × Ton/Lm. When the I _ Lm fraction is sufficiently small, io is substantially fixed. Lm is the inductance value of the excitation inductor, and T is the excitation period of the excitation signal Ip.

Other aspects of the fifth embodiment of the present invention are the same as those of the second embodiment of the present invention, and are not described herein again.

Fig. 9 shows a schematic block diagram of a dimming control circuit according to a sixth embodiment of the present invention. Compared to the fifth embodiment shown in fig. 7, the conversion module 113 and the compensation module 114 are different.

In this embodiment, the compensation module 114 includes a twelfth diode D10 connected between the first current source I1 and the first ground GND, and further connected to the conversion module 113. Specifically, a first terminal of the first current source I1 is connected to a second terminal of the primary winding of the isolation circuit 120, a second terminal of the first current source I1 is connected to an anode of a twelfth pole tube D10, and a cathode of the twelfth pole tube D10 is connected to the first ground GND.

The voltage across the ninth diode D9 in the rectifying circuit 130, i.e. the first bias voltage Vt, can be obtained by sampling the voltage across the twelfth diode D10. Specifically, by connecting the first current source I1 and the twelfth diode D10 in series to the primary ground, the voltage across the twelfth diode D10 may characterize the voltage across the ninth diode D9 in the rectifying circuit 130, i.e., the first bias voltage Vt, during the active period (Ton period) of the excitation signal Ip.

The conversion module 113 includes a first end, a second end and an output end, and the first end of the conversion module 113 is connected to the first end of the primary winding of the isolation circuit 120; a second end of the conversion module 113 is connected to the detection module 112, and receives the dimming voltage signal VD _ s; the output terminal of the conversion module 113 outputs a dimming reference signal VDIM. Wherein VDIM = VCC-VD _ s-Vt-Vr.

Other aspects of the sixth embodiment of the present invention are the same as those of the fifth embodiment of the present invention, and are not described herein again.

Fig. 10 shows a schematic block diagram of a dimming control circuit according to a seventh embodiment of the present invention. Compared to the fifth embodiment shown in fig. 7, the conversion module 113 and the compensation module 114 are different.

The compensation module 114 includes an eleventh diode D11 and a fifth resistor R5, an anode of the eleventh diode D11 is connected to the second end of the primary winding of the isolation circuit 120, and a cathode thereof is connected to the first end of the first current source I1; the fifth resistor R5 is connected between the first terminal of the first current source I1 and the first ground terminal GND. The second terminal of the first current source I1 is connected to the first ground GND.

The conversion module 113 includes a first end, a second end and an output end, and the first end of the conversion module 113 is connected to the first end of the primary winding of the isolation circuit 120; a second end of the conversion module 113 is connected to the detection module 112, and receives the dimming voltage signal VD _ s; the output terminal of the conversion module 113 outputs a dimming reference signal VDIM. The driving method comprises the following steps that VDIM =2VD \s1-VD _ s2-VCC-Vr, wherein VD _ s1 is a voltage signal sampled in an effective period of an excitation signal Ip; VD _ s2 is the voltage signal sampled during the period when the excitation signal Ip is inactive.

As shown in fig. 11, during the active period (Ton period) of the excitation signal Ip, i.e., the excitation signal Ip = Ipk, the dimming voltage signal VD _ s1 is obtained, during the inactive period of the excitation signal Ip, i.e., the excitation signal Ip =0, the primary winding of the transformer T1 is short-circuited, the power supply voltage VCC, the primary winding of the transformer T1, the eleventh diode D11, and the fourth resistor R4 form a loop, and the sampling voltage VD _ s2 is obtained, and a voltage difference exists between the sampling voltage VD _ s2 and the power supply voltage VCC, and the value is a voltage drop of the eleventh diode D11.

Other aspects of the seventh embodiment of the present invention are the same as those of the fifth embodiment of the present invention, and are not described herein again.

According to the dimming control circuit provided by the embodiment of the invention, the isolation circuit transmits the excitation signal from the primary winding to the secondary winding, and the rectifying circuit rectifies the excitation signal and supplies power to the dimmer; and the secondary winding of the isolation circuit receives the dimming signal generated by the dimmer through the rectifying circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit. The dimming control circuit of the embodiment of the invention does not relate to a complex singlechip technology or a conventional analog PWM adjusting circuit, and the whole circuit has simple structure and low cost.

Further, when a primary winding of the isolation circuit generates current (i.e., during an active period of an excitation signal), the isolation circuit works in a forward converter state, the isolation circuit stores energy, the isolation circuit transmits the pulse current signal from the primary winding to the secondary winding, the pulse current signal is rectified by the rectification circuit and then supplies power to the dimmer, meanwhile, the secondary winding of the isolation circuit receives the dimming signal through the rectification circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit. When no current is generated in the primary winding of the isolation circuit (namely during the period that the excitation signal is invalid), the isolation circuit works in a forward converter state, and the energy stored in the isolation circuit is released to supply power to the dimmer. The dimming voltage signal of the representative dimming signal is sampled in the forward working state, and the waveform is more stable and reliable.

Fig. 12 shows a flowchart of a dimming control method according to an embodiment of the present invention. As shown in fig. 12, the dimming control method includes the following steps.

In step S1201, an excitation signal is generated.

In this embodiment, the excitation signal Ip is a pulse current signal, which is a rectangular wave having a period T, a peak value Ipk, and a pulse width Ton, and is generated by an excitation conversion circuit.

In step S1202, the excitation signal is transmitted from the primary winding to the secondary winding of the isolation circuit.

In this embodiment, the isolation circuit is a transformer T1, a primary winding of the transformer T1 is connected to the excitation conversion circuit, and a secondary winding of the transformer T1 is connected to the rectification circuit; the turn ratio of the number of turns of the primary winding of the transformer T1 to the number of turns of the secondary winding is n:1, n is a positive number. The first end of the primary winding is a homonymous end, and the second end of the primary winding is a heteronymous end. The first end of the secondary winding is a homonymous end, and the second end of the secondary winding is a synonym end. The first end of the dimmer is connected with the first output end of the rectifying circuit, and the second end of the dimmer is connected with the second end of the secondary winding or the second output end of the rectifying circuit and is connected with a second grounding end.

In a preferred embodiment, the secondary winding includes a first secondary winding and a second secondary winding. The second end of the first secondary winding and the first end of the second secondary winding are in short circuit, the turn ratio of the coil turns of the primary winding of the isolation circuit to the coil turns of the first secondary winding to the coil turns of the second secondary winding is n:1, and n is a positive number. The first end of the primary winding of the isolation circuit is a homonymous end, and the second end of the primary winding of the isolation circuit is a heteronymous end. The first end of the first secondary winding is a homonymous end, and the second end of the first secondary winding is a heteronymous end. The first end of the second secondary winding is a homonymous end, and the second end of the second secondary winding is a synonym end. The first end of the dimmer is connected with the first output end of the rectifying circuit, and the second end of the dimmer is connected with the second end of the first secondary winding and the second grounding end.

In step S1203, the excitation signal is rectified.

In step S1204, the rectified excitation signal is filtered to output a supply current Io for supplying power to the dimmer. When the power is supplied to the dimmer, the secondary winding of the isolation circuit receives the dimming signal through the rectification circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit.

In a preferred embodiment, when a primary winding of the isolation circuit generates current, the isolation circuit transmits an excitation signal Ip from the primary winding to the secondary winding, and the excitation signal Ip is rectified by the rectification circuit and then supplies power to the dimmer; when no current is generated in the primary winding of the isolation circuit, the secondary winding of the isolation circuit receives the dimming signal through the rectification circuit, and a dimming reference signal VDIM representing the dimming signal is generated at two ends of the primary winding of the isolation circuit. Wherein the supply current Io = Ipk n Ton/T.

In another preferred embodiment, when a current is generated in the primary winding of the isolation circuit, the isolation circuit transmits an excitation signal Ip from the primary winding to the secondary winding, and supplies power to the dimmer after the excitation signal is rectified by the rectification circuit, and meanwhile, the secondary winding of the isolation circuit receives the dimming signal through the rectification circuit, and a dimming reference signal VDIM representing the dimming signal is generated at two ends of the primary winding of the isolation circuit. Wherein the supply current Io = (Ipk-I _ Lm) × n = Ton/T.

The dimming control circuit provided by the embodiment of the invention can be applied to an LED drive circuit, and provides a dimming reference signal VDIM for the main control chip, and the main control chip adjusts the drive current of an LED load according to the dimming reference signal VDIM, thereby realizing dimming on the LED load.

While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A dimming control circuit, comprising:

an excitation conversion circuit for generating an excitation signal;

the primary winding of the isolation circuit is connected with the excitation conversion circuit, receives an excitation signal and transmits the excitation signal to the secondary winding of the isolation circuit;

the input end of the rectifying circuit is connected with the secondary winding of the isolating circuit, and the output end of the rectifying circuit is connected with the dimmer;

the excitation conversion circuit comprises an excitation module, the excitation module comprises a power supply voltage and a first current source, the first end of a primary winding of the isolation circuit receives the power supply voltage, and the first current source is connected between the second end of the primary winding of the isolation circuit and a first grounding end to generate the excitation signal;

and the secondary winding of the isolation circuit receives the dimming signal generated by the dimmer through the rectification circuit, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit.

2. The dimming control circuit of claim 1, wherein the isolation circuit transmits the excitation signal from a primary side to a secondary side, and the excitation signal is rectified by the rectification circuit to supply power to the dimmer.

3. The dimming control circuit of claim 1, wherein the excitation signal is a pulsed current signal.

4. The dimming control circuit of claim 1, wherein the excitation conversion circuit further comprises:

the detection module is connected with the first end of the first current source and is used for detecting the voltage of the second end of the primary winding of the isolation circuit during the invalid period of the excitation signal so as to obtain a dimming voltage signal;

and the conversion module is respectively connected with the detection module and the first end of the primary winding of the isolation circuit and converts the dimming voltage signal into a dimming reference signal.

5. The dimming control circuit of claim 4, wherein the excitation conversion circuit further comprises a compensation module coupled between the excitation module and the second end of the primary winding of the isolation circuit to compensate for the dimming voltage signal.

6. The dimming control circuit of claim 4 or 5, wherein the detection module comprises a first switch, a first resistor and a first capacitor,

the first switch, the first resistor and the first capacitor are connected in series between the first end of the first current source and the first grounding end, and a node between the first resistor and the first capacitor outputs a dimming voltage signal.

7. The dimming control circuit of claim 6, wherein the first switch is turned on during a period when the excitation signal is inactive.

8. The dimming control circuit of claim 4 or 5, wherein the conversion module comprises a first terminal and a second terminal and an output terminal,

the first end of the conversion module is connected with the first end of the primary winding of the isolation circuit;

the second end of the conversion module is connected with the detection module and receives the dimming voltage signal;

and the output end of the conversion module outputs a dimming reference signal.

9. The dimming control circuit of claim 5, wherein the compensation module comprises a seventh diode and a third resistor,

the anode of the seventh diode is connected with the second end of the primary winding of the isolation circuit, and the cathode of the seventh diode is connected with the first end of the first current source;

the third resistor is connected between the first terminal of the first current source and the first ground terminal.

10. The dimming control circuit of claim 5, wherein the compensation module comprises a seventh diode, an eighth diode, and a third resistor,

the seventh diode and the eighth diode are connected in series between the second end of the primary winding of the isolation circuit and the first end of the first current source;

the anode of the eighth diode is connected with the second end of the primary winding of the isolation circuit, and the cathode of the eighth diode is connected with the anode of the seventh diode;

the cathode of the seventh diode is connected with the first end of the first current source;

the third resistor is connected between the first terminal of the first current source and the ground terminal.

11. The dimming control circuit of claim 8, wherein the dimming reference signal VDIM = VD _ S-VCC, wherein VCC is a supply voltage and VD _ S is a dimming voltage signal.

12. The dimming control circuit of claim 1, wherein the excitation conversion circuit further comprises:

the detection module is connected with the second end of the primary winding of the isolation circuit and is used for detecting voltage signals at two ends of the primary winding of the isolation circuit in the effective period of the excitation signal so as to obtain a dimming voltage signal;

and the conversion module is connected with the detection module and the first end of the primary winding of the isolation circuit and converts the dimming voltage signal into a dimming reference signal.

13. The dimming control circuit of claim 12, wherein the detection module comprises a first switch and a first capacitor,

the first switch and the first capacitor are connected in series between the second end of the primary winding and the first ground terminal, and a node between the first switch and the first capacitor outputs a dimming voltage signal.

14. The dimming control circuit of claim 13, wherein the first switch is turned on during an active period of the excitation signal.

15. The dimming control circuit of claim 12, wherein the excitation conversion circuit further comprises:

the compensation module is connected with the conversion module and used for outputting a first bias voltage;

wherein the first bias voltage is used for compensating the dimming voltage signal.

16. The dimming control circuit of claim 15, wherein the compensation module comprises a second current source and a thermistor, wherein the second current source and the thermistor are connected in series between a first terminal of a primary winding of the isolation circuit and a first ground terminal;

a node between the second current source and the thermistor outputs a first bias voltage.

17. The dimming control circuit of claim 15, wherein the compensation module comprises a twelfth diode, an anode of the twelfth diode is connected to the second terminal of the first current source, a cathode of the twelfth diode is connected to the first ground, and a voltage across the twelfth diode is the first bias voltage.

18. The dimming control circuit of claim 16 or 17, wherein the conversion module comprises a first end to a third end and an output end,

the first end of the conversion module is connected with the first end of the primary winding;

the third end of the conversion module is connected with the compensation module and receives a first bias voltage;

the conversion module obtains a dimming reference signal according to the dimming voltage signal, the power voltage and the first bias voltage, and the output end outputs the dimming reference signal.

19. The dimming control circuit of claim 15, wherein the compensation module comprises an eleventh diode and a fifth resistor,

the anode of the eleventh diode is connected with the second end of the primary winding of the isolation circuit, and the cathode of the eleventh diode is connected with the first end of the first current source;

the fifth resistor is connected between the cathode of the eleventh diode and the first ground terminal.

20. The dimming control circuit of claim 19, wherein the conversion module comprises a first terminal, a second terminal, and an output terminal,

the conversion module obtains a dimming reference signal according to the dimming voltage signal and the power voltage, and the output end outputs the dimming reference signal.

21. The dimming control circuit of claim 1, wherein the secondary winding of the isolation circuit comprises a first secondary winding and a second secondary winding;

wherein the second end of the first secondary winding and the first end of the second secondary winding are shorted;

the first end of the first secondary winding is a homonymous end, and the second end of the first secondary winding is a heteronymous end;

the first end of the second secondary winding is a homonymous end, and the second end of the second secondary winding is a heteronymous end;

the turn ratio of the number of turns of the primary winding, the number of turns of the first secondary winding and the number of turns of the second secondary winding of the isolation circuit is n:1, and n is a positive number.

22. The dimming control circuit of claim 1, wherein a turns ratio of a number of turns of a primary winding of the isolation circuit to a number of turns of a secondary winding is n:1, n being a positive number.

23. The dimming control circuit of claim 21, wherein the rectifying circuit comprises a first diode and a second diode, wherein an anode of the first diode is connected to the first end of the first secondary winding, a cathode of the first diode is connected to the cathode of the second diode, and an anode of the second diode is connected to the second end of the second secondary winding.

24. The dimming control circuit of claim 22, wherein the rectification circuit comprises a third diode through a sixth diode,

the anode of the third diode is connected with the first end of the secondary winding, and the cathode of the third diode is connected with the cathode of the fifth diode;

the cathode of the fourth diode is connected with the first end of the secondary winding, and the anode of the fourth diode is connected with the second grounding end;

the anode of the fifth diode is connected with the second end of the secondary winding;

and the cathode of the sixth diode is connected with the second end of the secondary winding, and the anode of the sixth diode is connected with the second grounding end.

25. The dimming control circuit of claim 22, wherein the rectifying circuit comprises a ninth diode and a zener diode, an anode of the ninth diode is connected to the first end of the secondary winding of the isolation circuit, and a cathode of the ninth diode is connected to the first end of the dimmer; and the voltage-stabilizing tube is connected between two ends of the secondary winding of the isolation circuit.

26. The dimming control circuit according to claim 5 or 15, further comprising:

and the filter circuit is connected between the rectifying circuit and the dimmer and is used for filtering the rectified excitation signal.

27. The dimming control circuit of claim 21, wherein a first terminal of the dimmer is connected to the first output terminal of the rectifying circuit, and a second terminal of the dimmer is connected to the second terminal of the first secondary winding.

28. The dimming control circuit of claim 22, wherein a first terminal of the dimmer is coupled to the first output terminal of the rectifying circuit and a second terminal of the dimmer is coupled to the second output terminal of the rectifying circuit.

29. The dimming control circuit of claim 16 or 17, wherein the dimming reference signal VDIM = VCC-VD _ S-Vt-Vr, wherein VCC is a supply voltage, VD _ S is a dimming voltage signal, vt is a first bias voltage characterizing a voltage drop across the rectifying circuit, and Vr is a second bias voltage characterizing a voltage drop across the filtering circuit.

30. The dimming control circuit of claim 19, wherein the dimming reference signal VDIM =2vd _s1-VD _ S2-VCC-Vr, wherein VCC is a power supply voltage, VD _ S1 is a dimming voltage signal during active periods of the excitation signal, VD _ S2 is a dimming voltage signal during inactive periods of the excitation signal, and Vr is a second bias voltage characterizing a voltage drop across the filter circuit.

31. The dimming control circuit of claim 1, wherein the isolation circuit is a transformer.

32. A dimming control method for a dimming control circuit, the dimming control circuit including at least an isolation circuit, the dimming control method comprising:

generating an excitation signal at a primary winding of the isolation circuit by adopting a first current source;

transmitting the excitation signal from a primary winding to a secondary winding of the isolation circuit;

rectifying the excitation signal and supplying power to a dimmer;

and the secondary winding of the isolation circuit receives a dimming signal generated by a dimmer and generates a dimming reference signal representing the dimming signal at two ends of the primary winding of the isolation circuit.

33. The method of claim 32, wherein the excitation signal is a pulsed current signal.

34. The method of claim 32, wherein the isolation circuit transfers the excitation signal from the primary side to the secondary side when a current is generated in a primary side winding of the isolation circuit, and rectifies the excitation signal to supply power to the dimmer; when no current is generated in the primary winding of the isolation circuit, the secondary winding of the isolation circuit receives the dimming signal, and dimming reference signals representing the dimming signal are generated at two ends of the primary winding of the isolation circuit.

35. The method of claim 32, wherein the isolation circuit transmits the excitation signal from the primary winding to the secondary winding and rectifies the excitation signal to power the dimmer when a current is generated in the primary winding, and wherein the secondary winding receives the dimming signal and generates a dimming reference signal indicative of the dimming signal across the primary winding of the isolation circuit.

36. The method of claim 32, further comprising:

the rectified excitation signal is filtered.