LED dimming circuit, LED dimming system and dimming method

Abstract

The present invention discloses an LED dimming circuit, an LED dimming system and a dimming method. The LED dimming circuit comprises: an inductor coil for connecting an LED light source, a current control switch connected to the inductor coil, a charging time control module and a switch control module; the charging time control module is used to send a first control signal to the switch control module after a preset first time interval from the moment when the inductor current passes through zero; the switch control module is used to control the current control switch to turn off; and, receiving the first control signal of the charging time control module, controls the current control switch to close. The LED dimming circuit controls the average current size of the LED by controlling the time of the zero-crossing stage of the inductor current, effectively realizes the adjustment of the luminous brightness, and can ensure the consistency of each LED light source at the same time.

Description

Technical Field

[0001] The present invention relates to the field of LED driving, and in particular to an LED dimming circuit, an LED dimming system and an LED dimming method. Background Art

[0002] LED light source is a light source based on light-emitting diodes, which has the advantages of using low-voltage power supply, low energy consumption, strong applicability, high stability, short response time, no pollution to the environment, and multi-color light emission. With the continuous development of LED technology, LED light sources have been widely used. Shopping malls, factories, houses and other scenes will use a large number of LED light sources for lighting or decoration, and adjust the brightness of these LED light sources when necessary to provide comfortable lighting.

[0003] At present, the dimming method of LED light source driving mainly adopts discontinuous conduction mode (DCM). In the dimming circuit using DCM dimming method, in each light-emitting cycle (that is, the inductor current cycle), the inductor current will be properly reset (that is, the inductor current will return to zero), and when the current control switch is closed, the inductor current is zero, and it is not easy to cause inductor saturation, so it is easy to control the circuit. However, in the existing dimming circuit using DCM dimming method, there are too many factors affecting the current size in the circuit, such as input voltage, output voltage, and changes in inductance will cause changes in output current, resulting in poor consistency of multiple LED light sources when there are multiple LED light sources in the circuit, and the dimming effect of each LED light source varies greatly. Therefore, how to effectively adjust the luminous brightness of multiple LED light sources to ensure the consistency of each LED light source has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide an LED dimming circuit, an LED dimming system and a dimming method to achieve consistency of each LED light source when dimming each LED light source.

[0005] As a first aspect of an embodiment of the present invention, an embodiment of the present invention provides an LED dimming circuit, which is used to connect an inductor coil of an LED light source, a current control switch connected to the inductor coil, a charging time control module, and a switch control module;

[0006] The charging time control module is used to send a first control signal to the switch control module after a preset first time interval starting from the moment when the inductor current passes through zero;

[0007] The switch control module is used to control the current control switch to be turned off; and receive the first control signal of the charging time control module to control the current control switch to be turned on.

[0008] In some optional embodiments, the LED dimming circuit further includes: a zero-crossing detection module;

[0009] The zero-crossing detection module is connected to the current control switch, and is used to perform zero-crossing detection on the inductor current of the inductor coil, and send a second control signal to the charging time control module when the inductor current crosses zero;

[0010] The preset first time interval is the time interval between the second control signal and the first control signal.

[0011] In some optional embodiments, the charging time control module includes: a first current source, a second current source, a first capacitor, a second capacitor and a first capacitor charging control module; the current of the second current source is adjustable; the first capacitor charging control module is respectively connected to the first current source, the first capacitor and the zero-crossing detection module, and the second current source is connected to the second capacitor;

[0012] The first capacitor charging control module is used to control the first current source to charge the first capacitor until a second control signal sent by the zero-crossing detection module is received;

[0013] The second current source is used to charge the second capacitor until the voltage of the second capacitor after being charged is equal to the voltage of the first capacitor after being charged;

[0014] The preset first time interval is a difference between a charging time of the second capacitor and a charging time of the first capacitor.

[0015] In some optional embodiments, the charging time control module further includes: a voltage comparison module, the voltage comparison module is connected to the first capacitor and the second capacitor;

[0016] The voltage comparison module is used to send a first control signal to the switch control module when the voltage of the second capacitor after being charged is equal to the voltage of the first capacitor after being charged.

[0017] In some optional embodiments, the voltage comparison module includes: a first comparator;

[0018] The first capacitor and the second capacitor are connected to two input terminals of the first comparator respectively, and the output terminal of the first comparator is connected to the switch control module.

[0019] In some optional embodiments, the charging time control module further includes: a signal inverter connected to the output end of the first comparator.

[0020] In some optional embodiments, the charging time control module further includes: an operational amplifier connected between the first capacitor and the first comparator, and / or, connected between the second capacitor and the first comparator.

[0021] In some optional embodiments, the first capacitor charging control module is further connected to the current control switch, and is configured to control the first current source to charge the first capacitor upon receiving a high level signal from the control end of the current control switch.

[0022] In some optional embodiments, the first capacitor charging control module includes: a D trigger and a charging start switch;

[0023] The charging start switch is connected to the first current source and the first capacitor; The end is connected to the control end of the charging start switch; the trigger end of the D flip-flop is connected to the control end of the current control switch, and is used to receive a high level signal from the control end of the current control switch to control the charging start switch to close; the reset end of the D flip-flop is connected to the zero-crossing detection module, and is used to control the charging start switch to open when receiving the second control signal of the zero-crossing detection module.

[0024] In some optional embodiments, the charging time control module further includes: a controller, a first discharge switch, and a second discharge switch;

[0025] The controller is connected to control ends of the first discharge switch and the second discharge switch respectively, the first discharge switch is connected in parallel with the first capacitor, and the second discharge switch is connected in parallel with the second capacitor;

[0026] The controller is used to receive a high level signal from the control end of the current control switch, and control the first discharge switch and the second discharge switch to close for a preset time length to discharge the first capacitor and the second capacitor.

[0027] In some optional embodiments, the switch control module includes: a second comparator, an RS trigger and a driver;

[0028] Two input terminals of the second comparator are connected to the current control switch and the reference potential respectively, and an output terminal of the second comparator is connected to the R terminal of the RS trigger;

[0029] The S end of the RS trigger is connected to the charging time control module, the Q end of the RS trigger is connected to the input end of the driver, and the output end of the driver is connected to the current control switch.

[0030] In some optional embodiments, the current control switch is an NMOS tube, the gate of the NMOS tube is connected to the output end of the driver, the drain of the NMOS tube is connected to the inductor, the source of the NMOS tube is grounded via a current sensing resistor, and an input end of a second comparator is connected between the source of the NMOS tube and the current sensing resistor.

[0031] In some optional embodiments, the switch control module is specifically configured to control the current control switch to be turned off when the first voltage output by the current control switch is equal to the reference potential.

[0032] In some optional embodiments, the LED dimming circuit further includes a converter connected to the second current source;

[0033] The converter converts the current of the second current source according to the received preset dimming control signal.

[0034] In some optional embodiments, according to the received preset dimming control signal, a proportional coefficient of the current of the first current source and the second current source is controlled to be equal to a set value.

[0035] As a second aspect of an embodiment of the present invention, an embodiment of the present invention provides an LED dimming system, comprising: at least one LED light source and any one of the above-mentioned LED dimming circuits.

[0036] As a third aspect of an embodiment of the present invention, an embodiment of the present invention provides a method for dimming using any of the above-mentioned LED dimming circuits.

[0037] The LED dimming circuit provided in the embodiment of the present invention controls the time of the zero-crossing stage of the inductor current, that is, adjusts the duty cycle of the inductor current, and controls the average current size of the LED by adjusting the duty cycle of the inductor current, thereby effectively adjusting the luminous brightness. Therefore, when the LED dimming circuit provided in the embodiment of the present invention is used to dim each LED light source, the consistency of each LED light source can be guaranteed.

[0038] Furthermore, the LED dimming circuit provided by the embodiment of the present invention controls the time of the zero-crossing stage of the inductor current by adjusting the charging current of the second capacitor in the charging time control module, that is, adjusts the duty cycle of the LED current, and controls the size of the LED average current by adjusting the duty cycle of the LED current, thereby effectively adjusting the luminous brightness. Since the sizes of the first capacitor and the second capacitor, the current of the first current source, the threshold voltage of the circuit, and the current sensing resistor in the LED dimming circuit are pre-set invariants, the size of the average current of the LED is only related to the size of the charging current of the second capacitor.

[0039] Furthermore, the first capacitor is proportional to the second capacitor, the second current source is set to be a proportional replica of the first current source, and the dimming control signal controls the size of the ratio, so that the average current size of the LED is only related to the size of the dimming control signal, that is, the dimming control signal controls the proportional amount, not the absolute value. Therefore, when the LED dimming circuit provided by the embodiment of the present invention is used to dim each LED light source, the consistency of each LED light source can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of the structure of an LED dimming circuit provided by an embodiment of the present invention;

[0041] Figure 2 A schematic diagram of the structure of an LED dimming circuit provided by an embodiment of the present invention;

[0042] Figure 3 for Figure 2 A structural diagram of a charging time control module of an LED dimming circuit shown;

[0043] Figure 4 The inductor current I under the control of the LED dimming circuit provided in the embodiment of the present invention L Timing diagram of

[0044] Figure 5 A schematic diagram of a specific implementation of an LED dimming circuit provided by an embodiment of the present invention;

[0045] Figure 6 for Figure 5 A structural schematic diagram of a specific implementation of a charging time control module of an LED dimming circuit shown;

[0046] Figure 7 A timing diagram of current and voltage signals in an LED dimming circuit provided by an embodiment of the present invention;

[0047] Figure 8 is the second charging current I in the charging time control module dim Schematic diagram of the circuit structure of the generation;

[0048] Fig. 9 for Figure 8 The second charging current I dim A schematic structural diagram of a specific implementation scheme of a generating circuit. DETAILED DESCRIPTION

[0049] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0050] In the prior art, the driving modes of LED light sources mainly include continuous conduction mode (CCM) and discontinuous conduction mode (DCM). In the CCM dimming mode, the inductor current will not reach 0 within a light-emitting cycle, that is, the inductor will not be "reset". It has a high cost, is prone to inductor saturation, and is difficult to control, especially deep dimming. Therefore, it is not suitable for dimming of LED light sources and has gradually been out of practical application; in the DCM dimming mode, within a light-emitting cycle (that is, the inductor current cycle), the inductor current will be properly reset (that is, the inductor current will return to zero), and when the power switch is closed, the inductor current is zero. However, in the traditional DCM dimming mode, there are too many factors that affect the current size in the circuit, such as changes in input voltage, output voltage, inductance, etc., which will cause changes in output current. When there are multiple LED light sources in the circuit, the consistency of the LED light sources is poor, resulting in a large difference in the dimming effect of each LED light source. Therefore, how to effectively adjust the luminous brightness and ensure the consistency of each LED light source has become an urgent problem to be solved.

[0051] The embodiment of the present invention aims at solving the problems existing in the prior art and provides a new LED dimming circuit in the DCM dimming mode. Figure 1 As shown, the LED dimming circuit includes: an inductor coil for connecting to an LED light source, a current control switch connected to the inductor coil, a charging time control module, and a switch control module;

[0052] The charging time control module is used to send a first control signal to the switch control module after a preset first time interval starting from the moment when the inductor current passes through zero;

[0053] The switch control module is used to control the current control switch to be turned off; and receive the first control signal of the charging time control module to control the current control switch to be turned on.

[0054] The LED dimming circuit provided in the embodiment of the present invention controls the time of the zero-crossing stage of the inductor current, that is, adjusts the duty cycle of the inductor current. By adjusting the duty cycle of the inductor current, the average current of the LED is controlled, and the luminous brightness is effectively adjusted. Therefore, when using the LED dimming circuit provided in the embodiment of the present invention to dim each LED light source, the consistency of each LED light source can be guaranteed.

[0055] In one embodiment, referring to Figure 2 As shown, the LED dimming circuit further includes: a zero-crossing detection module;

[0056] The zero-crossing detection module is connected to the current control switch, and is used to perform zero-crossing detection on the inductor current of the inductor coil, and send a second control signal to the charging time control module when the inductor current crosses zero;

[0057] The preset first time is the time interval between the second control signal and the first control signal.

[0058] In order to better illustrate the specific implementation of the embodiment of the present invention, a specific embodiment 1 is described in detail as follows:

[0059] Embodiment 1

[0060] Reference Figure 2 and Figure 3 As shown, the LED dimming circuit includes: an inductor coil for connecting an LED light source, a current control switch connected to the inductor coil, a charging time control module, a switch control module and a zero-crossing detection module; wherein:

[0061] The zero-crossing detection module is connected to the current control switch, and is used to perform zero-crossing detection on the inductor current of the inductor coil, and send a second control signal to the charging time control module at the moment when the inductor current crosses zero;

[0062] The charging time control module includes: a first current source, a second current source, a first capacitor, a second capacitor, a first capacitor charging control module and a voltage comparison module; the current of the first current source is a preset current value, and the current of the second current source is adjustable;

[0063] The first capacitor charging control module is respectively connected to the first current source, the first capacitor, the current control switch and the zero-crossing detection module, and is used to control the first current source to charge the first capacitor when receiving a high-level signal from the current control switch, and control the first current source to stop charging the first capacitor until receiving a second control signal sent by the zero-crossing detection module;

[0064] The second current source is connected to the second capacitor and is used to charge the second capacitor until the voltage comparison module determines that the voltage of the second capacitor after being charged is equal to the voltage of the first capacitor after being charged;

[0065] a voltage comparison module, configured to send a first control signal to the switch control module when the voltage of the second capacitor after being charged is equal to the voltage of the first capacitor after being charged;

[0066] The switch control module is connected to a reference potential, and controls the current control switch to be turned off when the first voltage output by the current control switch is equal to the reference potential; and receives the first control signal of the charging time control module to control the current control switch to be closed.

[0067] In the embodiment of the present invention, the difference between the charging time of the second capacitor and the charging time of the first capacitor is the preset first time interval, and the time length of the first time interval can be set by adjusting the magnitude of the charging current of the second current source to the second capacitor. Obviously, if the capacitance of the first capacitor is equal to the capacitance of the second capacitor, in order to ensure that the charging time of the first capacitor is always less than the charging time of the second capacitor, in the embodiment of the present invention, the current of the first current source needs to be greater than the current of the second current source.

[0068] In the above embodiment, the first capacitor charging control module controls the first current source to charge the first capacitor when receiving a high-level signal from the current control switch. In this embodiment, for the current control switch, the signal when current passes through the current control switch is a high-level signal, and the signal when no current passes through the current control switch is a low-level signal.

[0069] It should be noted that, in the embodiment of the present invention, the specific circuit implementation of the zero-crossing detection module can refer to the prior art, and is not limited in the embodiment of the present invention. In this example, the zero-crossing detection module can achieve the purpose of detecting the zero-crossing point of the inductor current, and is not strictly limited in the embodiment of the present invention.

[0070] The LED dimming circuit provided by the embodiment of the present invention controls the time of the zero-crossing stage of the inductor current by adjusting the charging current of the second capacitor in the charging time control module, that is, adjusts the duty cycle of the inductor current. By adjusting the duty cycle of the inductor current, the size of the average current of the LED is controlled, and the luminous brightness is effectively adjusted. Since in the LED dimming circuit, the sizes of the first capacitor and the second capacitor, the current of the first current source, the threshold voltage of the circuit and the current sensing resistor are pre-set invariants, the size of the average current of the LED is only related to the size of the charging current of the second capacitor. Therefore, when using the LED dimming circuit provided by the embodiment of the present invention to dim each LED light source, the consistency of each LED light source can be guaranteed.

[0071] The core idea of ​​the present invention is that in the LED dimming circuit of the DCM dimming mode, how to control the brightness of the lamp is actually to control the size of the LED average current, and the size of the LED average current can be controlled by controlling the time T of the inductor current zero-crossing stage (the inductor current remains zero) in the inductor current cycle. OFF That can be achieved, the specific instructions are as follows:

[0072]

[0073] Where: I AVG is the average current of the LED (that is, the average value of the inductor current), V REF is the threshold voltage in the LED dimming circuit, R is the current sensing resistor in the LED dimming circuit, T ON is the time of the inductor energy storage stage, T dmg is the time of the inductor energy storage release stage, T is the period of the inductor current in the LED dimming circuit;

[0074] In the embodiment of the present application, it should be noted that in formula (1), the threshold voltage V REF , is the peak voltage that the inductor current can reach on the current sensing resistor R in the LED dimming circuit; Represents the inductor current I in the LED dimming circuit L The peak current I PEAK ;reference Figure 4 The timing diagram of the inductor current change in the dimming circuit shown in the figure, the time T of the inductor energy storage stage ON , that is, the length of the conduction time of the current control switch in the inductor current cycle in the LED dimming circuit; the time T of the inductor energy release phase dmg , that is, the length of time for the inductor to release energy after the current control switch is disconnected during the inductor current cycle in the LED dimming circuit; the time T of the inductor current zero crossing stage OFF , that is, the length of time that the inductor current is zero in the inductor current cycle in the LED dimming circuit; the inductor current cycle T is the time T of the inductor energy storage stage ON and the time T of the inductive energy storage release phase dmg and the time T of the inductor current zero crossing phase OFF The sum of ON +T dmg +T OFF .

[0075] It can be seen from formula (1) that the average current of the inductor current I AVG , and the duty cycle of the inductor current, that is, is positively correlated, achieving control of the time T of the inductor current zero crossing stage OFF, the average current I of the inductor can be realized AVG Therefore, the inventors further thought of controlling the time T of the inductor energy storage stage. ON and the time T of the inductive energy storage release phase dmg The sum of the durations of the inductor current zero-crossing phase is realized by controlling the time T OFF Furthermore, by using the first current source and the second current source to charge the first capacitor C1 and the second capacitor C2 respectively, the charging time of the first capacitor C1 is used to represent the time when there is current in the inductor, that is, the time T of the inductor energy storage stage. ON and the time T of the inductive energy storage release phase dmg The charging time of the second capacitor C2 is used to represent the inductor current cycle T of the LED dimming circuit. This is equivalent to using the charging time of the capacitor to represent the time of each stage of the inductor current. The specific formula derivation process is:

[0076]

[0077]

[0078] Substituting equation (2) and equation (3) into equation (1) above, we can obtain:

[0079]

[0080] In the above formulas (2)-(4), I R is the current of the first current source, I dim is the current of the second current source.

[0081] From the above formula (4), it can be seen that since the sizes of the first capacitor C1 and the second capacitor C2 are pre-selected fixed values, and the current sensing resistor R and the current I of the first current source R and the threshold voltage V in the LED dimming circuit REF is also a pre-determined invariant, so the only real variable is I dim Therefore, in the LED dimming circuit provided by the embodiment of the present invention, the factors affecting the current size in the prior art are simplified, and by adjusting I dim One variable can achieve the effect of adjusting the brightness of the LED light source. The average current I AVG The current I of the second current source can be dim There are few factors that affect the current size in the LED dimming circuit, which effectively achieves the consistency of the current of the LED light source in the LED dimming circuit.

[0082] Furthermore, I dim isI R The proportional replication, that is, I dim =K·IR , and K is greater than or equal to 0, then I dim =K·I R Substituting into the above formula (4), we can get:

[0083]

[0084] From the above formula (5), we can know that the average current of the LED, that is, the average value of the inductor current I AVG Only the ratio of the first capacitor C1 to the second capacitor C2 and the threshold voltage V REF and the current sensing resistor R, and I dim with I R For the above formula (5), the capacitance ratio of the first capacitor C1 and the second capacitor C2, the threshold voltage V REF The current sensing resistor R and current sensing resistor R are both high precision parameter values. Therefore, only by controlling I dim with I R The proportional coefficient K can achieve the average current I of the LED AVG Adjustment can achieve high-precision dimming control and ensure the dimming consistency of multiple LED light sources.

[0085] As a specific implementation of the embodiment of the present invention, the first capacitor charging control module includes: a D trigger and a charging start switch M2;

[0086] In a specific embodiment, referring to Figure 6 As shown, the charging start switch M2 is a PMOS tube, the drain and source of the PMOS tube are connected to the first current source and the first capacitor C1 respectively, and the control end of the PMOS tube, that is, the gate, is connected to the D trigger The D terminal of the D flip-flop is connected to the voltage input terminal of the first current source, so the D terminal maintains a high level. Figure 5 and Figure 6 As shown, the trigger end of the D flip-flop is connected to the control end of the current control switch M1. When the control end of the current control switch M1 is a high level signal, the D flip-flop The terminal outputs a low level signal, the charging start switch M2 is closed, and the first current source starts to charge the first capacitor C1. Figure 5 and Figure 6 As shown, the reset terminal CLR of the D flip-flop is connected to the zero-crossing detection module. When the zero-crossing detection module detects that the current of the current control switch M1 crosses the zero point, the zero-crossing detection module sends a second control signal, the D flip-flop is reset, and the D flip-flop The terminal outputs a high level signal, the charging start switch M2 is disconnected, and the first current source stops charging the first capacitor C1.

[0087] The LED dimming circuit provided in the embodiment of the present invention adjusts the current I when the second current source charges the second capacitor C2 dim The size of the inductor current cycle T is used to realize the time T of the inductor energy storage phase. ON and the time T of the inductive energy storage release phase dmg The sum of the durations of the inductor current and the time T of the zero-crossing phase OFF The proportion of the inductor current can be adjusted to adjust the average current of the inductor current and dim the LED light source. Through the charging time control module, the influence of other factors in the LED dimming circuit on the brightness of the LED light source is reduced, ensuring the consistency of the current of each LED light source.

[0088] In a specific embodiment, when the capacitance of the first capacitor C1 is equal to the capacitance of the second capacitor C2, the current I of the first current source is R is greater than the current I of the second current source dim .

[0089] In a specific embodiment, it can be, referring to Figure 6 As shown, the voltage comparison module is a first comparator COMP1, and a signal inverter is connected to the output end of the first comparator COMP1, and is connected to the switch control module through the signal inverter; the first capacitor C1 and the second capacitor C2 are respectively connected to the two input ends of the first comparator COMP1. In the embodiment of the present invention, when the first capacitor C1 starts charging, the second current source starts to charge the second capacitor C2, and the voltages of the first capacitor C1 and the second capacitor C2 are compared by the first comparator COMP1. When the voltages of the first capacitor and the second capacitor are equal, the output end of the first comparator COMP1 outputs a negative signal, which is inverted by the connected signal inverter and then sends a first control signal V to the switch control module. SET At this time, the first control signal V SET It is a positive signal.

[0090] In a specific embodiment, referring to Figure 6 As shown, the charging time control module also includes: a controller, a first discharge switch M3 and a second discharge switch M4;

[0091] The controller is connected to the control end of the first discharge switch M3 and the second discharge switch M4 respectively, the first discharge switch M3 is connected in parallel with the first capacitor C1, and the second discharge switch M4 is connected in parallel with the second capacitor C2; the input end of the controller is connected to the control end of the current control switch M1, and when the control end of the current control switch M1 is a high level signal, the controller controls the first discharge switch M3 and the second discharge switch M4 to close for a preset time length, so that the first capacitor C1 and the second capacitor C2 are discharged, and the charges in the first capacitor C1 and the second capacitor C2 are completely discharged, so that the first current source and the second current source recharge the first capacitor C1 and the second capacitor C2 respectively. Because the discharge time of the capacitor C1 and the capacitor C2, that is, the preset time length, is very short, the impact on the entire inductor current cycle T of the LED dimming circuit can be ignored.

[0092] It should be noted that, in the embodiment of the present invention, the specific circuit implementation of the controller can refer to the prior art, and is not limited in the embodiment of the present invention. As long as the control end of the detection current control switch M1 is a high-level signal, and the purpose of driving the first discharge switch M3 and the second discharge switch M4 to close is achieved, this is not strictly limited in the embodiment of the present invention.

[0093] In a specific embodiment, referring to Figure 6 As shown, the charging time control module also includes: an operational amplifier connected between the first capacitor C1 and the first comparator COMP1, so that the output end of the operational amplifier outputs the voltage V C1 The voltage V is equal to e , thereby preventing the voltage V of the second capacitor C2 from C2 Affects the voltage V of the first capacitor C1 C1 , resulting in inaccurate comparison results of the voltage signals of the first capacitor C1 and the second capacitor C2. Of course, in the embodiment of the present invention, the operational amplifier can also be connected between the second capacitor C2 and the first comparator COMP1, or an operational amplifier is connected between the first capacitor C1 and the first comparator COMP1, and between the second capacitor C2 and the first comparator COMP1, respectively. As long as the effect of signal isolation can be achieved and the accuracy of the comparison results of the voltage signals of the first capacitor C1 and the second capacitor C2 is guaranteed, the specific implementation method of signal isolation is not specifically limited in the embodiment of the present invention.

[0094] In a specific embodiment, referring to Figure 5As shown, the switch control module includes: a second comparator COMP2, an RS trigger and a driver, the current control switch M1 is an NMOS tube; the gate of the NMOS tube is connected to the output end of the driver, the drain of the NMOS tube is connected to the inductor coil, the source of the NMOS tube is grounded via a current sensing resistor R, and an input end of the second comparator COMP2 is connected between the source of the NMOS tube and the current sensing resistor R; the other input end of the second comparator COMP2 is connected to the reference potential V REF1 The output end of the second comparator COMP2 is connected to the R end of the RS trigger; the S end of the RS trigger is connected to the output end V of the signal inverter of the charging time control module SET , the Q end of the RS trigger is connected to the input end of the driver.

[0095] In an inductor current cycle of the LED dimming circuit, when the current control switch M1 is turned on, the current flows through the LED light source, the inductor coil L1, the current control switch M1 and the current sensing resistor R. At this stage, the system is in the inductor energy storage stage. The current flowing through the current control switch M1 and the current sensing resistor R gradually increases, and the voltage Vcs across the current sensing resistor R also gradually increases. When Vcs increases to the reference potential V REF1 When the two terminals are equal, the second comparator COMP2 sends a positive signal V to the R terminal of the RS trigger. PEAK , the Q end of the RS trigger sends a negative signal to the driver, and the driver controls the NMOS tube M1 to turn off. At this time, the first capacitor C1 and the second capacitor C2 of the charging time control module continue to charge. At this time, the system enters the inductor energy storage release stage, and the current flows through the inductor L1, the freewheeling diode and the LED light source. When the inductor coil L1 is fully discharged, an oscillation signal will be formed at the drain of the current control switch M1. The zero-crossing detection module detects this oscillation signal through the gate of the current control switch M1, thereby issuing a second control signal V ZCD , the system enters the inductor current zero-crossing stage. At this time, the first capacitor C1 stops charging, and the second capacitor C2 continues charging. When the voltage of the second capacitor C2 is equal to the voltage of the first capacitor C1, the output end of the first comparator COMP1 outputs a negative signal, which is inverted by the connected signal inverter, and the charging time control module sends a first control signal V to the S end of the RS trigger. SET , the Q end of the RS trigger sends a positive signal to the driver, the driver controls the NMOS tube M1 to close again, and the system enters the next switching cycle.

[0096] Reference Figure 2 and Figure 5 As shown, in the embodiment of the present invention, the external AC power is converted into a DC driving power of the LED light source by a rectifier module. In the embodiment of the present invention, the specific implementation method of the rectifier module can be adopted Figure 5The structure shown may also adopt other existing technologies, which will not be described in detail here. The embodiment of the present invention does not strictly limit the specific circuit implementation method of the rectifier module.

[0097] In order to better reflect the dimming consistency of each LED light source by the LED dimming circuit of the embodiment of the present invention, the following reference Figure 7 The timing diagram of the current and voltage signals in the LED dimming circuit shown in the figure is combined with Figure 5 and Figure 6 , the specific implementation process of the above circuit in one LED dimming cycle (ie one inductor current cycle) is described in detail.

[0098] Reference Figure 7 It can be seen that the charging time of the first capacitor C1 is the time T of the inductor energy storage stage. ON and the time of the inductive energy storage release phase T dmg The charging time of the second capacitor C2 is the period T of an inductor current of the LED dimming circuit. The LED dimming circuit of the embodiment of the present invention is described below from the starting point to the end point of a period T of the inductor current of the LED dimming circuit, and the action process of each module and component in the circuit, wherein the end point of the previous period T of the inductor current is also the starting point of the next period T of the inductor current:

[0099] At the beginning of the cycle, the control terminal signal V GATE The current control switch M1 is closed, and the LED dimming circuit enters the inductor energy storage stage. ON , the trigger end of the D flip-flop of the charging time control module receives V GATE After the high-level signal, since the D terminal of the D flip-flop keeps the high-level signal, the D flip-flop The terminal outputs a negative signal, and the charging start switch M2 of the charging time control module is closed. At this time, the first current source starts to charge the first capacitor C1, and at the same time, the second current source also starts to charge the second capacitor C2;

[0100] The first current source and the second current source respectively charge the first capacitor C1 and the second capacitor C2 continuously. When the source output voltage V CS Reaching the reference potential V REF1 When the second comparator COMP2 outputs V PEAK The positive signal is sent to the R terminal of the RS trigger, and the Q terminal of the RS trigger outputs a negative signal. The driver controls the current control switch M1 to turn off according to the negative signal. After the current control switch M1 is turned off, the inductor current I L The time T when the LED dimming circuit enters the inductor energy storage release stage begins to decrease dmg ;

[0101] When the inductor current I L When the current drops to zero, the LED dimming circuit enters the zero-crossing phase of the inductor current. OFF The zero-crossing detection module detects the inductor current I L When it passes through zero, a second control signal V is sent to the reset terminal of the D flip-flop. ZCD , the reset terminal of the D flip-flop receives V ZCD After the signal, the D flip-flop The terminal outputs a positive signal, the charging start switch M2 of the charging time control module is disconnected, and the potential V C1 Keep in the current state, after the operational amplifier is connected to output a C1 Voltage signal V e The time T of the inductor current zero-crossing phase in the LED dimming circuit OFF The second current source still continues to charge the second capacitor C2. When the potential V C2 The voltage signal rises to the voltage signal V e When the magnitudes of are equal, the first comparator COMP1 outputs a negative signal, which is inverted by the signal inverter and then outputs a positive signal V SET , the S terminal of the RS trigger of the switch control module receives a positive signal V SET After that, the Q end of the RS trigger outputs a positive signal to the driver, and the driver drives the current control switch M1 to close again. At this time, the LED dimming circuit re-enters the inductor energy storage stage T ON It should be noted that when the LED dimming circuit enters a new inductor current cycle T, the inductor energy storage phase time T ON At the beginning, the controller of the charging time control module receives the control terminal V of the current control switch M1. GATE The signal is a high-level signal, and the controller sends a pulse signal to close the first discharge switch M3 and the second discharge switch M4, so that the charges in the first capacitor C1 and the second capacitor C2 are completely discharged. At this time, the first current source and the second current source immediately recharge the first capacitor C1 and the second capacitor C2 in a new dimming cycle.

[0102] It is not difficult to conclude from the detailed description of the specific implementation process of the above LED dimming circuit that the average current I of the inductor current in the LED dimming circuit AVG The size of the adjustment can be adjusted by adjusting the charging current I of the second current source to the second capacitor C2 dim Therefore, the factor affecting the current in the circuit is single, and when dimming the LED light source, when there are multiple LED light sources in the circuit, the consistency of each LED light source can also be guaranteed.

[0103] In some optional embodiments, the LED dimming circuit further includes a converter connected to the second current source; the converter converts the current of the second current source according to the received preset dimming control signal. In the embodiment of the present invention, the connection relationship between the converter and the second current source can refer to the method in the prior art, and is not specifically limited here.

[0104] In a specific embodiment, referring to Figure 8 As shown, the current I of the second current source dim The current size can be obtained by the converter according to the preset dimming control signal. Specifically, the preset dimming control signal can be a digital signal representing the current size of the LED light source; it can also be an analog level signal representing the current size in the LED light source; it can also be a pulse width modulation signal (PWM signal) with adjustable duty cycle, and its duty cycle represents the current size of the LED light source. It is not strictly limited in the present invention. The converter converts the received dimming control signal to obtain a variable output current, that is, the current I of the second current source dim , used to charge the second capacitor C2. The converter may be a digital-to-analog converter (DAC), or a combination of an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC), which is not strictly limited in the present invention.

[0105] As a specific implementation of the embodiment of the present invention, according to the received preset dimming control signal, the proportional coefficient of the current of the first current source and the second current source is controlled to be equal to the set value. The above preset dimming control signal is a digital signal, and the current I dim The current I from the first current source R Replication, that is, I dim =K·I R According to formula 5, the LED current is the average value of the inductor current I AVG , only the ratio of the first capacitor C1 to the second capacitor C2, and the threshold voltage V in the LED dimming circuit REF Related to the current sensing resistor R, etc., these parameters are high-precision values. Therefore, by controlling I dim with I R The proportionality coefficient K is used to achieve the average LED current I AVG The adjustment not only achieves high-precision dimming control, but also ensures the dimming consistency of multiple LED light sources.

[0106] Reference Fig. 9 As shown, the first current source VDD provides a current I R The first current source and the second current source form a plurality of proportional current mirrors, each current mirror corresponds to a control switch (K1 to KN ), each control switch is connected to a current source of corresponding proportional size through a proportional current mirror. According to the received dimming control signal, the control switches K1 to K N By closing different switches in the circuit, we can get the proportional parameter K and the corresponding current I of the second current source. dim In the dimming application scenario, according to the size of the received dimming control signal, the corresponding at least one control switch is closed to obtain the corresponding proportional coefficient K, and the corresponding current I of the second current source can be obtained. dim , thereby achieving the dimming purpose of the LED light source.

[0107] The technical solution of the present invention can be applied to a variety of application scenarios, such as household lighting, stage lighting, etc. The embodiments of the present invention do not strictly limit the application scenarios.

[0108] Based on the same inventive concept, an embodiment of the present invention further provides an LED dimming system, comprising: at least one LED light source and the LED dimming circuit in the above embodiment.

[0109] Regarding the LED dimming system in the above embodiment, the specific manner in which the LED dimming circuit performs the operation has been described in detail in the LED dimming circuit in the above embodiment, and will not be elaborated here.

[0110] Based on the same inventive concept, an embodiment of the present invention further provides a method for dimming using the LED dimming circuit of the above embodiment.

[0111] Regarding the dimming method of the LED dimming circuit in this embodiment, the specific implementation steps can refer to the detailed description of the LED dimming circuit in the above embodiment, and will not be elaborated here.

[0112] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An LED dimming circuit, comprising: An inductor coil connected to an LED light source and a current control switch connected to the inductor coil, characterized in that it also includes: a charging time control module and a switch control module; The charging time control module is used to send a first control signal to the switch control module after a preset first time interval starting from the moment when the inductor current passes through zero; The switch control module is used to control the current control switch to turn off; and receive the first control signal of the charging time control module to control the current control switch to turn on; The charging time control module includes: a first current source, a second current source, a first capacitor, a second capacitor and a first capacitor charging control module; the current of the second current source is adjustable to control the proportional coefficient of the current of the first current source and the second current source to be equal to a set value K; The first capacitor charging control module is respectively connected to the first current source, the first capacitor and the zero-crossing detection module, and the second current source is connected to the second capacitor; the first capacitor charging control module is used to control the first current source to charge the first capacitor until a second control signal sent by the zero-crossing detection module is received; the charging time of the first capacitor is the sum of the duration of the inductor energy storage stage and the duration of the inductor energy storage release stage; The second current source is used to charge the second capacitor until the voltage of the second capacitor after being charged is equal to the voltage of the first capacitor after being charged; the charging time of the second capacitor is one LED dimming cycle of the LED dimming circuit; The preset first time interval is a difference between a charging time of the second capacitor and a charging time of the first capacitor.

2. The LED dimming circuit according to claim 1, characterized in that: Also includes: Zero-crossing detection module; The zero-crossing detection module is connected to the current control switch, and is used to perform zero-crossing detection on the inductor current of the inductor coil, and send a second control signal to the charging time control module when the inductor current crosses zero; The preset first time interval is the time interval between the second control signal and the first control signal.

3. The LED dimming circuit according to claim 1, characterized in that: The charging time control module further includes: a voltage comparison module, wherein the voltage comparison module is connected to the first capacitor and the second capacitor; The voltage comparison module is used to send a first control signal to the switch control module when the voltage of the second capacitor after being charged is equal to the voltage of the first capacitor after being charged.

4. The LED dimming circuit according to claim 3, characterized in that: The voltage comparison module includes: a first comparator; The first capacitor and the second capacitor are connected to two input terminals of the first comparator respectively, and the output terminal of the first comparator is connected to the switch control module.

5. The LED dimming circuit according to claim 4, characterized in that: The charging time control module further includes: a signal inverter connected to the output end of the first comparator.

6. The LED dimming circuit according to claim 4, characterized in that: The charging time control module further includes: an operational amplifier connected between the first capacitor and the first comparator, and / or connected between the second capacitor and the first comparator.

7. The LED dimming circuit according to claim 1, characterized in that: The first capacitor charging control module is also connected to the current control switch, and is used to control the first current source to charge the first capacitor when receiving a high level signal from the control end of the current control switch.

8. The LED dimming circuit according to claim 7, characterized in that: The first capacitor charging control module includes: a D trigger and a charging start switch; The charging start switch is connected to the first current source and the first capacitor; the Q end of the D trigger is connected to the control end of the charging start switch; the trigger end of the D trigger is connected to the control end of the current control switch, and is used to receive a high-level signal from the control end of the current control switch to control the charging start switch to close; the reset end of the D trigger is connected to the zero-crossing detection module, and is used to control the charging start switch to open when receiving the second control signal of the zero-crossing detection module.

9. The LED dimming circuit according to claim 1, characterized in that: The charging time control module further includes: a controller, a first discharge switch and a second discharge switch; The controller is connected to control ends of the first discharge switch and the second discharge switch respectively, the first discharge switch is connected in parallel with the first capacitor, and the second discharge switch is connected in parallel with the second capacitor; The controller is used to receive a high level signal from the control end of the current control switch, and control the first discharge switch and the second discharge switch to close for a preset time length to discharge the first capacitor and the second capacitor.

10. The LED dimming circuit according to any one of claims 1 to 9, characterized in that: The switch control module includes: a second comparator, an RS trigger and a driver; Two input terminals of the second comparator are connected to the current control switch and the reference potential respectively, and an output terminal of the second comparator is connected to the R terminal of the RS trigger; The S end of the RS trigger is connected to the charging time control module, the Q end of the RS trigger is connected to the input end of the driver, and the output end of the driver is connected to the current control switch.

11. The LED dimming circuit according to claim 10, characterized in that: The current control switch is an NMOS tube, the gate of the NMOS tube is connected to the output end of the driver, the drain of the NMOS tube is connected to the inductor, the source of the NMOS tube is grounded via a current sensing resistor, and an input end of the second comparator is connected between the source of the NMOS tube and the current sensing resistor.

12. The LED dimming circuit according to claim 10, characterized in that: The switch control module is specifically used to control the current control switch to be turned off when the first voltage output by the current control switch is equal to the reference potential.

13. The LED dimming circuit according to any one of claims 1 to 9, characterized in that: Also included is a converter connected to a second current source; The converter converts the current of the second current source according to the received preset dimming control signal.

14. The LED dimming circuit according to claim 13, characterized in that: According to the received preset dimming control signal, the proportionality coefficient of the current of the first current source and the second current source is controlled to be equal to a set value.

15. An LED dimming system, characterized in that: include: At least one LED light source and the LED dimming circuit according to any one of claims 1-14.

16. A method for dimming using the LED dimming circuit according to any one of claims 1 to 14.

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