Segmented Dimming Switch Control System

Abstract

The present invention provides a segmented dimming switch control system, which includes a DC power supply, a switching switch, a buck-type LED control circuit, and a buck-type LED circuit. Among them, the buck-type LED control circuit includes a low-voltage clamping unit, a power detection unit, a multi-channel adjustable duty cycle generation unit, a logic state latch and gating unit, a clock oscillator unit, a current control unit, a PWM logic control unit, and a pre-output driving unit. The present invention realizes segmented dimming by controlling the switch, and does not require an externally connected resistor to the DIM dimming pin for input, with simple and convenient operation, meeting the customer requirements of miniaturization and portability.

Description

Technical Field

[0001] The present invention belongs to the field of circuit design, and particularly relates to a segmented dimming switch control system. Background Art

[0002] Traditional segmented dimming control systems require a large number of control pins and external components: at the input end, a segmented dimming pin DIM (connected to an external resistor) is needed to select the reference for controlling the dimming level. Even for the power supply, two power supplies need to be provided: a low-voltage power supply VDD for the pre-stage control system and a medium-high voltage power supply VIN for the output power stage. During the process of technology update, customer requirements tend to be more miniaturized and convenient applications. Applications with a large number of control pins and peripheral components will gradually lose their competitive advantages. Summary of the Invention

[0003] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a segmented dimming switch control system to solve the problem of the large number of control pins and external components required by the existing segmented dimming control system.

[0004] To achieve the above object and other related objects, the present invention provides a segmented dimming switch control system, which includes: a DC power supply, a switching switch, a buck-type LED control circuit, and a buck-type LED circuit; the DC power supply is used to provide a control power supply for the buck-type LED control circuit; the switching switch is connected between the DC power supply and the buck-type LED control circuit, and is used to control the rising and falling processes of the control power supply to achieve the level switching of the control power supply; the output end of the buck-type LED control circuit is connected to the buck-type LED circuit, and the buck-type LED control circuit is used to output a logic control signal to the buck-type LED circuit according to the level switching of the control power supply, so as to achieve the segmented dimming of the buck-type LED circuit.

[0005] Optionally, the DC power supply is a medium-high voltage DC power supply. The buck-type LED control circuit includes: a low-voltage clamping unit, a power supply detection unit, a multi-channel adjustable duty cycle generation unit, a logic state latching and gating unit, a clock oscillator unit, a current control unit, a PWM logic control unit, and an output pre-driver unit. The low-voltage clamping unit is used to pull up the external low-voltage power supply to generate a stable low-voltage power supply for internal power supply of the control system. The power supply detection unit is used to detect whether the switching switch has a level switch and generate a state switching control signal. The clock oscillator unit is used to generate a clock signal to the multi-channel adjustable duty cycle generation unit to generate multiple selectable period signals with different duty cycles. The logic state latching and gating unit outputs an envelope signal after receiving multiple state switching control signals and the selectable period signals. The current control unit is used to generate a charging signal. The PWM logic control unit is used to generate the logic control signal according to the clock signal and the charging signal, and the logic control signal is used to control the on and off of the power transistor of the buck-type LED circuit.

[0006] Optionally, the buck-type LED control circuit further includes an AND gate for performing an AND operation on the envelope signal and the logic control signal, so that the logic control signal output to the output pre-driver unit is controlled by the envelope signal to achieve the function of segmented dimming.

[0007] Optionally, the low-voltage clamping unit includes: an operational amplifier, a clamping power transistor, a first voltage-dividing resistor, a second voltage-dividing resistor, a VDD capacitor, and an internal equivalent load module. The first end of the first voltage-dividing resistor is connected to the external low-voltage power supply, the second end is connected to the first end of the second voltage-dividing resistor and is used to divide the voltage signal with the input resistor at the first input terminal of the operational amplifier. The second end of the second voltage-dividing resistor is grounded. The second input terminal of the operational amplifier is connected to the internal clamping reference voltage. The output terminal of the operational amplifier is connected to the gate of the clamping power transistor. The first pole of the clamping power transistor is connected to the external low-voltage power supply and the internal equivalent load module, and the second pole is grounded. The first end of the VDD capacitor is connected to the external low-voltage power supply, and the second end is grounded. When the voltage-dividing signal of the external low-voltage power supply is higher than the internal clamping reference voltage, the output terminal of the operational amplifier stabilizes the voltage value of the external low-voltage power supply at the set voltage value through the clamping power transistor.

[0008] Optionally, the power detection unit includes an undervoltage protection module, a switch switching detection module, and a digital module shutdown detection module. The undervoltage protection module is configured to output an undervoltage protection signal to the output pre-driver unit when the external low-voltage power supply is lower than the undervoltage protection reference, so as to turn off the logic control signal of the output pre-driver unit. The switch switching detection module is configured to output a low-level state switching control signal to the logic state latch and gating unit when detecting that the switching switch performs a level switching, so that the logic state latch and gating unit changes its state once. The digital module shutdown detection module is configured to generate a shutdown signal to turn off the control system when detecting that the voltage of the external low-voltage power supply drops to the digital module shutdown reference, so that the control system enters the sleep mode.

[0009] Optionally, the undervoltage protection reference is obtained by internal reference voltage division. The switch switching detection module determines whether the switching switch performs a level switching by comparing the voltage of the external low-voltage power supply and the threshold voltage of the field effect transistor. The shutdown signal of the digital module is implemented by a Schmitt inverter.

[0010] Optionally, the multi-way adjustable duty cycle generation unit first generates an envelope signal with a period of T through clock signal frequency division, where T is less than or equal to 10 ms. Then, multiple envelope signals with different duty cycles are obtained by changing the duty cycle of the envelope signal to form multiple signal levels. The buck LED control circuit is configured to select different duty cycle signal levels as the logic control signal of the buck LED circuit according to the level switching of the control power supply, so as to realize the segmented dimming of the buck LED circuit.

[0011] Optionally, the logic state latch and gating unit includes a state machine generation module based on registers. Among them, the number of registers m of the state machine generation module and the number of periods n of the duty cycle signal levels satisfy the following relationship: 2 m ≥n, where n is the number of periods of the duty cycle signal levels and n is an integer greater than or equal to 1.

[0012] Optionally, the buck LED circuit includes an inductor module, a freewheeling diode module, a power device, a sampling resistor module, and an LED lighting module. The first end of the LED lighting module is connected to the medium-high voltage DC power supply and the negative electrode of the freewheeling diode module. The second end of the LED lighting module is connected to the first end of the inductor module. The second end of the inductor module is connected to the positive electrode of the freewheeling diode module and the first pole of the power device. The second pole of the power device is connected to the first end of the sampling resistor module, and the gate is connected to the buck LED control circuit. The second end of the sampling resistor module is grounded.

[0013] Optionally, the DC power supply is a medium-high voltage DC power supply. The buck-type LED control circuit includes: a low-voltage clamping unit, a power supply detection unit, a multi-channel adjustable duty cycle generation unit, a logic state latching and gating unit, a clock oscillator unit, and a pre-output driving unit. Among them, the low-voltage clamping unit is used to pull up the external low-voltage power supply to generate a stable low-voltage power supply for internal power supply of the control system. The power supply detection unit is used to detect whether the switching switch has a level switch and generate a state switching control signal. The clock oscillator unit is used to generate a clock signal to the multi-channel adjustable duty cycle generation unit. The multi-channel adjustable duty cycle generation unit generates multiple selectable period signals with different duty cycles after receiving the clock signal. The logic state latching and gating unit outputs logic control signals with different duty cycles after receiving multiple state switching control signals and the selectable period signals. The logic control signals are used to control the turning on and off of the power transistor of the buck-type LED circuit, and different segmented dimming is achieved by adjusting the duty cycle of the logic control signals.

[0014] Optionally, the DC power supply has two power supplies. Among them, the power supply of the buck-type LED control circuit is a low-voltage DC power supply, and the power supply of the buck-type LED circuit is a medium-high voltage DC power supply. The buck-type LED control circuit includes: a power supply detection unit, a multi-channel adjustable duty cycle generation unit, a logic state latching and gating unit, a clock oscillator unit, and a pre-output driving unit. Among them, the power supply detection unit is used to detect whether the switching switch has a level switch and generate a state switching control signal. The clock oscillator unit is used to generate a clock signal to the multi-channel adjustable duty cycle generation unit. The multi-channel adjustable duty cycle generation unit generates multiple selectable period signals with different duty cycles after receiving the clock signal. The logic state latching and gating unit outputs logic control signals with different duty cycles after receiving multiple state switching control signals and the selectable period signals. The logic control signals are used to control the turning on and off of the power transistor of the buck-type LED circuit, and different segmented dimming is achieved by adjusting the duty cycle of the logic control signals.

[0015] Optionally, the buck-type LED circuit includes an inductor module, a freewheeling diode module, and a power device LED lighting module. The first end of the LED lighting module is connected to the medium-high voltage DC power supply and the negative electrode of the freewheeling diode module. The second end of the LED lighting module is connected to the first end of the inductor module. The second end of the inductor module is connected to the positive electrode of the freewheeling diode module and the first pole of the power device. The second pole of the power device is directly grounded, and the gate is connected to the buck-type LED control circuit.

[0016] As described above, the segmented dimming switch control system of the present invention has the following beneficial effects:

[0017] The present invention provides a specific implementation manner for realizing segmented dimming by using a switch control system. A DC power supply provides a control power supply for a switched buck LED control circuit. By switching a switch to control the rising and falling processes of the control power supply, the level switching of the control power supply is realized. The switched buck LED control circuit outputs a logic control signal to the buck LED circuit according to the level switching of the control power supply, thereby realizing the segmented dimming of the buck LED circuit. The present invention realizes segmented dimming by controlling a switch, and inputs a DIM dimming pin that does not require an external resistor, which is simple and convenient to operate. It meets the customer requirements of miniaturization and convenience. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It shows a schematic diagram of a switched buck LED control system with a segmented dimming pin.

[0019] Figure 2 It shows a schematic diagram of an implementation manner of segmented dimming of a switched buck LED control system.

[0020] Figure 3 It shows a schematic structural diagram of the segmented dimming switch control system according to an embodiment of the present invention.

[0021] Figure 4 It shows a schematic structural diagram of the switched buck LED control circuit of the segmented dimming switch control system according to an embodiment of the present invention.

[0022] Figure 5 It shows a schematic structural diagram of the low-voltage clamping unit according to an embodiment of the present invention.

[0023] Figure 6 It shows a timing diagram of the power supply detection unit and state selection according to an embodiment of the present invention.

[0024] Figure 7 It shows a schematic diagram of a multi-channel adjustable duty cycle generation unit generating a PWM periodic signal with an envelope according to an embodiment of the present invention.

[0025] Figure 8 It shows a schematic structural diagram of the logic state latching unit in the logic state latching and gating unit according to an embodiment of the present invention.

[0026] Figure 9 It shows a schematic diagram of a specific implementation manner of the power supply detection unit and the logic state latching and gating unit according to an embodiment of the present invention.

[0027] Figure 10Schematic diagram showing envelope signals with different duty cycles in different states generated by the multi-channel adjustable duty cycle generation unit according to an embodiment of the present invention.

[0028] Figure 11 Schematic diagram showing the structure of another segmented dimming switch control system according to an embodiment of the present invention.

[0029] Figure 12 Schematic diagram showing the structure of another buck-type LED control circuit of the segmented dimming switch control system according to an embodiment of the present invention.

[0030] Figure 13 Schematic diagram of the timing of the logic control signal PREDRV of the control system after omitting the output sampling resistor module Rsense in an embodiment of the present invention

[0031] Figure 14 Schematic diagram showing the structure of yet another segmented dimming switch control system according to an embodiment of the present invention.

[0032] Figure 15 Schematic diagram showing the structure of yet another buck-type LED control circuit of the segmented dimming switch control system according to an embodiment of the present invention.

[0033] Description of component labels

[0034] 1 Control system

[0035] 10 Medium-high voltage DC power supply

[0036] 11 Switching switch

[0037] 12 Buck-type LED control circuit

[0038] 121 Low-voltage clamping unit

[0039] 122 Power detection unit

[0040] 123 Multi-channel adjustable duty cycle generation unit

[0041] 124 Logic state latching and gating unit

[0042] 125 Clock oscillator unit

[0043] 126 Current control unit

[0044] 127 PWM logic control unit

[0045] 128 Output pre-driver unit

[0046] 129 AND gate

[0047] 13 Buck-type LED circuit

[0048] 20 Low-voltage DC power supply Specific implementation manners

[0049] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0050] When detailing the embodiments of the present invention, for ease of illustration, the cross-sectional views showing the device structure will be locally enlarged out of the general proportion, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention here. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0051] For the convenience of description, spatial relationship terms such as "under", "below", "lower than", "beneath", "above", "on", etc. may be used herein to describe the relationship between one element or feature shown in the drawings and other elements or features. It will be understood that these spatial relationship terms are intended to encompass other directions of the device in use or operation in addition to the directions depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can also be one or more intervening layers.

[0052] In the context of the present application, the structure in which the first feature is "above" the second feature described may include an embodiment in which the first and second features are formed in direct contact, and may also include an embodiment in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0053] It should be noted that the illustrations provided in this embodiment only schematically illustrate the basic concept of the present invention. Therefore, only the components related to the present invention are shown in the illustrations, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in its actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0054] Figure 1 Shown is a schematic diagram of a buck-type LED control system 1, which includes a buck-type LED control circuit, a power device Q, a sampling resistor module Rsense, a freewheeling diode module D, an inductor module L, and an LED lighting module. The input medium-high voltage power supply is Vin, and the output voltage is the voltage drop V on the LED lighting module. LED。The external power device Q is periodically turned on and off. The sampling resistor module Rsense is connected between the source terminal of the external power device and the ground, belonging to low-side sampling. The DIM pin serves as a segmented dimming pin, and different reference selections can be achieved by connecting different external resistors, thereby changing the output current.

[0055] As Figure 2 shown is a way to implement segmented dimming. Its core parts are the DIM segmented selection unit and the reference selection unit.

[0056] After the low-voltage power supply VDD is powered on, DIM serves as the dimming pin, with an external pull-down resistor Rdown connected and then connected to the internal pull-up resistor Rup (this resistor can also be moved to the system peripheral application). The specific voltage signal DIM1 of DIM is obtained by resistor voltage division through the low-voltage power supply VDD pin. The low-voltage power supply VDD generates a set of voltage division signals DIV0~DIVn through a series of resistors: DIM1 and the voltage division signals DIV0~DIVn are sent to the input terminals of the comparator Comp with hysteresis. After being compared by the comparator, a set of comparison signals SW0~SWn are generated and then sent to the data selector MUX to obtain a set of digital control signals Bit0~n. The digital control signals Bit0~n are then sent to the reference selection unit to select a set of reference signals V REF1 ~V REFn (generated by internal reference voltage division) or one of the reference voltage signals of GND as the final current comparison segmented reference REFDAC. When V REFn ≤V DIM1 ≤V REFn-1 , select V REFDAC =V REFn , n = 0, 1, 2…. The current comparison segmented reference REFDAC is compared with the voltage at the current detection sampling terminal CS to stabilize the peak or average value of the output current at

[0057] The segmented dimming control system 1 of the above solution requires more control pins and external devices: at the input end, a segmented dimming pin DIM (with an external resistor) is needed to select the reference for controlling the dimming level, and at the output stage, a current detection sampling pin CS (connected to the sampling resistor module grounded) is also needed to sample the output current. Even for the power supply, two power supplies need to be provided: the low-voltage power supply VDD of the front-stage control system 1 and the medium-high voltage power supply VIN of the output power stage.

[0058] As Figure 3As shown in the figure, this embodiment provides a segmented dimming switch control system 1, and the segmented dimming switch control system 1 includes: a DC power supply, a switching switch 11, a buck-type LED control circuit 12, and a buck-type LED circuit 13; the DC power supply is used to provide a control power supply for the buck-type LED control circuit 12; the switching switch 11 is connected between the DC power supply and the buck-type LED control circuit 12, and is used to control the rising and falling processes of the control power supply to realize the level switching of the control power supply; the buck-type LED control circuit 12 is used to output a logic control signal to the buck-type LED circuit 13 according to the level switching of the control power supply, so as to realize the segmented dimming of the buck-type LED circuit 13; the buck-type LED circuit 13 is used to realize the segmented dimming of the brightness of the LED lighting module according to the logic control signal output by the buck-type LED control circuit 12.

[0059] As Figure 3 shown, the DC power supply is a medium-high voltage DC power supply 10. The buck-type LED circuit 13 may include, for example, a power device Q, a sampling resistor module Rsense, a freewheeling diode module D, an inductor module L, and an LED lighting module 131. In this embodiment, the first end of the LED lighting module 131 is connected to the medium-high voltage DC power supply 10 and the negative electrode of the freewheeling diode module D. The second end of the LED lighting module 131 is connected to the first end of the inductor module L. The second end of the inductor module L is connected to the positive electrode of the freewheeling diode module D and the first pole of the power device Q. The second pole of the power device Q is connected to the first end of the sampling resistor module Rsense, and the gate is connected to the buck-type LED control circuit. The second end of the sampling resistor module Rsense is grounded.

[0060] As Figure 4As shown, the DC power supply is a medium-high voltage DC power supply 10. The switched buck-type LED control circuit 12 includes: a low-voltage clamping unit 121, a power supply detection unit 122, a multi-channel adjustable duty cycle generation unit 123, a logic state latching and gating unit 124, a clock oscillator unit 125, a current control unit 126, a PWM logic control unit 127, and an output pre-driver unit 128. Among them, the low-voltage clamping unit 121 is used to pull up the external low-voltage power supply to generate a stable low-voltage power supply VDD for powering the system internally. The power supply detection unit 122 is used to detect whether the switching switch 11 undergoes a level switch and generate a state switch control signal. The clock oscillator unit 125 is used to generate a clock signal CLK to the multi-channel adjustable duty cycle generation unit 123 to generate multiple selectable period signals with different duty cycles. The logic state latching and gating unit 124 receives multiple state switch control signals and the selectable period signals to select one period signal with a specific duty cycle as the envelope signal Te. The current control unit 126 receives the feedback signal generated by the current detection sampling terminal and generates a charging signal Ton. The PWM logic control unit is used to generate the logic control signal PREDRV according to the charging signal Ton and the clock signal generated by the clock oscillator unit 125. The logic control signal PREDRV is used to control the turning on and off of the power transistor Q of the buck-type LED circuit 13.

[0061] Specifically, as Figure 4As shown, the low-voltage clamping unit 121 generates a stable low-voltage power supply VDD for internal power supply through the external low-voltage power supply VDD pull-up resistor RVDD and VDD capacitor CVDD. The power supply detection unit 122 is used to detect whether the switching switch 11 makes a switch, and generates a state switching control signal EN. Among them, each time the switch makes a switch, the segmented dimming level changes once. The clock oscillation unit generates a clock signal CLK to the multi-channel adjustable duty cycle generation unit 123 to generate n selectable periodic signals with different duty cycles, where n is an integer greater than or equal to 1. These n selectable periodic signals and the state switching control signal EN are sent to the logic state latch and strobe unit 124 together, and a periodic signal with a specific duty cycle is selected as the envelope signal Te. The original current detection sampling terminal CS (the feedback signal generated by the output current ILOAD passing through the sampling resistor module) enters the input terminal of the current control unit 126. The current control unit 126 generates a charging signal Ton. The charging signal Ton and the clock signal CLK generated by the clock oscillator unit 125 are processed by the PWM logic control unit to generate a logic control signal PREDRV. The logic control signal PREDRV is used to control the turn-on and turn-off of the power transistor Q. The buck-type LED control circuit 12 further includes an AND gate 129, which is used to perform an AND operation on the envelope signal Te and the logic control signal PRESRV to generate a logic control signal PREDRV_EN with an envelope to achieve the function of segmented dimming.

[0062] As Figure 5As shown, the low-voltage clamping unit 121 is used to generate the external low-voltage power supply VDD of the control system 1. The low-voltage clamping unit includes: an operational amplifier OP, a clamping power transistor MN1, a first voltage-dividing resistor Rvdd1, a second voltage-dividing resistor Rvdd2, a VDD capacitor CVDD, and an internal equivalent load module Rload. The first end of the first voltage-dividing resistor Rvdd1 is connected to the external low-voltage power supply, and the second end is connected to the first end of the second voltage-dividing resistor Rvdd2 and is used to divide the voltage signal with the input resistor at the first input terminal of the operational amplifier OP. The second end of the second voltage-dividing resistor Rvdd2 is grounded. The second input terminal of the operational amplifier OP is connected to the internal clamping reference voltage VREF_CLAMP, and the output terminal is connected to the gate of the clamping power transistor MN1. The first pole of the clamping power transistor MN1 is connected to the external low-voltage power supply VDD and the internal equivalent load module Rload, and the second pole is grounded. The first end of the VDD capacitor CVDD is connected to the external low-voltage power supply VDD, and the second end is grounded. When the voltage-dividing signal of the external low-voltage power supply is higher than the internal clamping reference voltage, the output terminal of the operational amplifier OP stabilizes the voltage value of the external low-voltage power supply at the set voltage value through the clamping power transistor MN1. Specifically, when the voltage-dividing signal VDD_div of the external low-voltage power supply VDD is higher than the internal clamping reference VREF_CLAMP, the output terminal of the operational amplifier will adjust the VDD voltage through the clamping NMOS device MN1, and finally ensure that the voltage of the external low-voltage power supply VDD is stabilized at the set voltage value. Among them, the voltage ratio relationship between VDD_div and VDD is: Derive the resistance value of RVDD through the current I_load required by the internal load: CVDD, as a voltage-stabilizing capacitor for storing charges, is also the frequency compensation capacitor of the internal loop. The main pole of the loop gain is determined by CVDD and the output impedance:

[0063] The power detection unit 122 includes an undervoltage protection module, a switching detection module, and a digital module shutdown detection module. The undervoltage protection module is used to ensure that when the external low-voltage power supply is lower than the undervoltage protection reference (e.g., 3V), an undervoltage protection signal UVLO is output to the output front-stage drive unit 128 to turn off the logic control signal PREDRV of the output front-stage drive unit 128, and to turn off unnecessary modules in the control system 1. When the switch is turned off, the power leakage current of the control system 1 should be controlled to the minimum. The switching detection module is used to output a low-level state switching control signal EN to the logic state latch and strobe unit when it detects that the switching switch makes a level switch, so that the logic state latch and strobe unit 124 changes its state once. Specifically, when the switching detection module is at the switching reference (e.g., 1.8V), the state switching control signal EN generates a low level to ensure that the subsequent logic state latch changes its state once. When VDD = 1.8V, the logic state latch still works normally. Each time the switching switch 11 switches, due to the charge storage function of the external capacitor CVDD, the voltage of the external low-voltage power supply VDD will not be directly released to zero. Here, it is necessary to calculate the switching time of the switching switch 11 and the capacitance value. According to the charge and discharge formula of the capacitor: Q = C VDD *ΔV VDD =I discharge *ΔT is derived, where △T represents the time interval when each switching switch 11 switches off, and △V VDD represents the voltage drop of VDD during the time interval, and I discharge represents the discharge current of the capacitor. A suitable CVDD ensures that the charge stored in the capacitor will not be released to zero during the switch switching time △T. The digital module shutdown detection module is used to generate a shutdown signal SHUT to turn off the control system 1 when it detects that the voltage of the external low-voltage power supply VDD further decreases to the digital module shutdown reference, so that the control system 1 enters the sleep mode. Specifically, the digital module shutdown detection module is used to detect that when the VDD voltage further decreases to a lower voltage, for example, it can be set that when VDD < 1.4V, the SHUT signal becomes low. At this time, since the off-time interval of the switch is long enough, the entire system will be turned off and enter the sleep mode. After the VDD power supply is re-connected, it will start to work normally.

[0064] For example, the undervoltage protection reference in the power detection unit 122 is obtained by internal reference voltage division; the switching detection module detects whether the switching switch makes a level switch by comparing the voltage of the external low-voltage power supply VDD and the threshold voltage of the field effect transistor Vth(MN2); the shutdown signal SHUT of the digital module is implemented by the Schmitt inverter Smit2.

[0065] It should be noted that the three VDD set voltages need to satisfy: undervoltage protection voltage > switching voltage > digital module voltage. Figure 6 It shows the timing diagram of the power supply detection unit 122 and status selection.

[0066] The multi-way adjustable duty cycle generation unit 123 first generates an envelope signal with a period of T through the clock signal CLK frequency division, where T is less than or equal to 10 ms, that is, the corresponding frequency is greater than or equal to 100 Hz. Then, by changing the duty cycle of the envelope signal, multiple envelope signals with different duty cycles are obtained to form multiple signal levels. The switching buck LED control circuit 12 selects different duty cycle signal levels according to the level switching of the control power supply as the logic control signal of the buck LED circuit 13, so as to realize the segmented dimming of the buck LED circuit 13. Specifically, in the multi-way adjustable duty cycle generation unit 123, an envelope signal with a period of T (such as 2 ms, 500 Hz) is first generated through the clock signal CLK frequency division, and then the duty cycle of the envelope signal is changed. A reference duty cycle is selected as the maximum set dimming segment for segmented dimming (the reference duty cycle can be set to 100%). Then it is divided into n levels. When the reference duty cycle is set to Duty, the minimum duty cycle is Duty / n, and the n dimming segmented levels correspond to Duty / n, 2*Duty / n, 3*Duty / n... (n - 1)*Duty / n and Duty in sequence.

[0067] As Figure 7 shown, one path is selected from the multi-way adjustable duty cycle generation unit 123 as the envelope signal Te, which is ANDed with the output signal PREDRV of the PWM logic control unit 127 to obtain the final control signal PREDRV_EN of the external power device Q, which is a PWM period signal with an envelope.

[0068] The logic state latch and strobe unit 124 includes a state machine generation module based on registers, where the number of registers m of the state machine generation module and the number of levels n of the duty cycle period signal satisfy the following relationship: 2 m ≥ n, where n is the number of levels of the duty cycle period signal and n is an integer greater than or equal to 1. Specifically, inside the logic state latch unit is a state machine generation module composed of registers, as Figure 8 shown. For example, when n = 5, it can be implemented by 3 DFF flip-flops. If other values are selected for n, the number of DFF registers m required needs to satisfy: 2 m ≥ n.

[0069] In this embodiment, the specific implementation manners of the power supply detection unit 122 and the logic state latch and strobe unit 124 are as Figure 9 shown.

[0070] In the power detection unit 122: The undervoltage protection reference can be obtained by dividing the internal reference voltage, because the internal bandgap reference has been established before the external low-voltage power supply VDD is lower than the undervoltage protection reference. The UVLO setting voltage The switch switching reference can be set by comparing the VDD voltage of the external low-voltage power supply and the threshold voltage V of one field-effect transistor th(MN2) to set the voltage The digital module shutdown signal SHUT is implemented by the Schmitt inverter Smit2. When the set VDD voltage is lower than 2 Vth, the SHUT signal becomes low level and the device can enter the sleep mode.

[0071] The Duty1 to Dutyn generated by the multi-channel adjustable duty cycle generation unit 123 and the b0 to b(n-1) generated by the logic state latching unit are sent to the data strobe unit MUX together to select a specific duty cycle for the final envelope signal Te, as Figure 10 shown.

[0072] It should be noted that the specific duty cycle settings of states 1 to n are not limited to Figure 10 the scheme shown. Specific segmentation methods can be given according to customer requirements, and other specific flash modes or Morse code modes can also be added.

[0073] Furthermore, the output sampling resistor module Rsense of the present invention can be omitted. Figure 11 The implementation manner of the control system 1 after omitting the output sampling resistor module Rsense is shown. At this time, the buck-type LED circuit 13 includes a power device Q, a freewheeling diode module D, an inductor module L, and an LED lighting module 131. In this embodiment, the first end of the LED lighting module 131 is connected to the medium-high voltage DC power supply 10 and the negative electrode of the freewheeling diode module D. The second end of the LED lighting module 131 is connected to the first end of the inductor module L. The second end of the inductor module L is connected to the positive electrode of the freewheeling diode module D and the first pole of the power device Q. The second pole of the power device Q is directly grounded, and the gate is connected to the switch buck-type LED control circuit. However, the inductance value and other peripheral application conditions of the inductor module L will be fixed. The generation of the internal logic control signal PREDRV requires setting a PWM period with a longer period and a larger duty cycle at the initial power-on to raise the output inductor current to the required current value, and then setting a PWM period with a shorter period to reduce the current ripple after stabilization.

[0074] For example, in one embodiment, as Figure 12As shown, the DC power supply is a medium-high voltage DC power supply 10. The buck-type LED control circuit 12 includes: a low-voltage clamping unit 121, a power supply detection unit 122, a multi-channel adjustable duty cycle generation unit 123, a logic state latching and gating unit 124, a clock oscillator unit 125, and an output pre-driver unit 128. Among them, the low-voltage clamping unit 121 is used to pull up the external low-voltage power supply to generate a stable low-voltage power supply VDD for internal power supply of the system. The power supply detection unit 122 is used to detect whether the switching switch 11 undergoes a level switch and generate a state switch control signal. The clock oscillator unit 125 is used to generate a clock signal CLK to the multi-channel adjustable duty cycle generation unit 123 to generate multiple selectable periodic signals with different duty cycles. After receiving multiple state switch control signals and the selectable periodic signals, the logic state latching and gating unit 124 outputs a logic control signal PREDRV with different duty cycles. The logic control signal PREDRV is used to control the turning on and off of the power tube of the buck-type LED circuit, and different segmented dimming is achieved by adjusting the duty cycle of the logic control signal PREDRV. After the period of the multi-channel adjustable duty cycle is stabilized, it is consistent with the logic control signal PREDRV. The logic control signal PREDRV does not carry an envelope signal. Its power-on initial state has a longer period and duty cycle, and the logic control signal PREDRV has a shorter period when the output current is stable. At this time, adjusting the duty cycle can achieve different segmented dimming segments, such as Figure 13 shown.

[0075] It should be further noted that as the switch control in the control system 1 of the present invention, it is not limited to Figure 3 the switch used to control the external medium-high voltage DC power supply 10, and can also be changed to the switch used to control the external low-voltage DC power supply 20 as shown in Figure 14 shown. If the external power supply is stable enough, the low-voltage clamping unit 121 in the internal architecture of the system can also be omitted. Figure 14 The output sampling resistor module Rsense is also omitted therein. At this time, the buck-type LED circuit 13 includes a power device Q, a freewheeling diode module D, an inductor module L, and an LED lighting module 131. In this embodiment, the first end of the LED lighting module 131 is connected to the medium-high voltage DC power supply 10 and the negative electrode of the freewheeling diode module D. The second end of the LED lighting module 131 is connected to the first end of the inductor module L. The second end of the inductor module L is connected to the positive electrode of the freewheeling diode module D and the first pole of the power device Q. The second pole of the power device Q is directly grounded, and the gate is connected to the buck-type LED control circuit. For the above-mentioned segmented dimming switch control system that omits the output sampling resistor module Rsense, such as Figure 14 and Figure 15As shown, the DC power supply has two power supplies. Among them, the power supply for the buck-boost LED control circuit is the low-voltage DC power supply 20, and the power supply for the buck LED circuit is the medium-high voltage DC power supply 10. The buck LED circuit omits the sampling resistor module. The buck-boost LED control circuit 12 includes: a power supply detection unit 122, a multi-channel adjustable duty cycle generation unit 123, a logic state latch and gating unit 124, a clock oscillator unit 125, and an output pre-driver unit 128. Among them, the power supply detection unit 122 is used to detect whether the switching switch 11 has a level switch and generate a state switch control signal. The clock oscillator unit 125 is used to generate a clock signal CLK to the multi-channel adjustable duty cycle generation unit 123 to generate multiple selectable period signals with different duty cycles. After receiving multiple state switch control signals and the selectable period signals, the logic state latch and gating unit 124 outputs a logic control signal PREDRV with different duty cycles. The logic control signal PREDRV is used to control the turn-on and turn-off of the power transistor of the buck LED circuit, and different segmented dimming is achieved by adjusting the duty cycle of the logic control signal PREDRV.

[0076] Generally speaking, the present invention internally has a power supply detection module to judge whether there is a switching action of an external switch, and externally has a switching switch and a capacitor to realize the rising and falling processes of the external low-voltage power supply VDD of the control system 1, and realize the high and low level switching of the switch control signal. The internally built multi-channel adjustable duty cycle generation unit 123 is used to generate n periodic signals with different duty cycles, and select one of the n periodic signals with different duty cycles as the envelope signal of the logic control signal PREDRV. This envelope signal presents different brightnesses on the output LED lighting module, thus realizing the function of segmented dimming. The internally built logic state latch and gating unit 124 is realized by DFF flip-flops. The latch state is changed once every time the switch is switched, so as to realize the selection of different state gating. In addition, the present invention can be extended to a situation without an external sampling resistor module. Internally, a high-frequency clock oscillator unit 125 and a multi-channel adjustable duty cycle generation unit 123 with initial state control are adopted. The output logic control signal PREDRV does not have an envelope signal and directly controls the turn-on and turn-off of the power device Q, which can further simplify the internal module of the control system 1.

[0077] As described above, the segmented dimming switch control system of the present invention has the following beneficial effects:

[0078] The present invention provides a specific implementation method for achieving segmented dimming by using a switching control system. A DC power supply provides a control power supply for a switched buck LED control circuit. By switching a switch to control the rising and falling processes of the control power supply, the level switching of the control power supply is realized. The switched buck LED control circuit outputs a logic control signal to the buck LED circuit according to the level switching of the control power supply, thereby achieving segmented dimming of the buck LED circuit. The present invention realizes segmented dimming by controlling a switch, and inputs a DIM dimming pin that does not require an external resistor, which is simple and convenient to operate. It meets the customer requirements of miniaturization and convenience.

[0079] Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0080] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A segmented dimming switch control system, characterized in that, The segmented dimming switch control system includes: a DC power supply, a switching switch, a buck-type LED control circuit, and a buck-type LED circuit; The DC power supply is used to provide a control power supply for the buck-type LED control circuit; The switching switch is connected between the DC power supply and the buck-type LED control circuit, and is used to control the rising and falling processes of the control power supply to achieve the level switching of the control power supply; The output end of the buck-type LED control circuit is connected to the buck-type LED circuit. The buck-type LED control circuit is used to output a logic control signal to the buck-type LED circuit according to the level switching of the control power supply, so as to realize the segmented dimming of the buck-type LED circuit; The DC power supply is a medium-high voltage DC power supply. The buck-type LED control circuit includes: a low-voltage clamping unit, a power supply detection unit, a multi-channel adjustable duty ratio generation unit, a logic state latching and gating unit, a clock oscillator unit, a current control unit, a PWM logic control unit, and a pre-output driving unit; The low-voltage clamping unit is used to pull up the external low-voltage power supply to generate a stable low-voltage power supply for internal power supply of the control system; the power supply detection unit is used to detect whether the switching switch has a level switching and generate a state switching control signal; the clock oscillator unit is used to generate a clock signal to the multi-channel adjustable duty ratio generation unit to generate multiple selectable period signals with different duty ratios; the logic state latching and gating unit outputs an envelope signal after receiving multiple state switching control signals and the selectable period signals; the current control unit is used to generate a charging signal; the PWM logic control unit is used to generate the logic control signal according to the clock signal and the charging signal, and the logic control signal is used to control the turning on and off of the power tube of the buck-type LED circuit.

2. The segmented dimming switch control system according to claim 1, wherein: The buck-type LED control circuit further includes an AND gate, which is used to perform an AND operation on the envelope signal and the logic control signal, so that the logic control signal output to the pre-output driving unit is controlled by the envelope signal to realize the function of segmented dimming.

3. The segmented dimming switch control system according to claim 1, wherein: The low-voltage clamping unit includes: an operational amplifier, a clamping power transistor, a first voltage-dividing resistor, a second voltage-dividing resistor, a VDD capacitor, and an internal equivalent load module. The first end of the first voltage-dividing resistor is connected to an external low-voltage power supply, and the second end is connected to the first end of the second voltage-dividing resistor and is used to divide the voltage signal with an input resistor at the first input terminal of the operational amplifier. The second end of the second voltage-dividing resistor is grounded. The second input terminal of the operational amplifier is connected to an internal clamping reference voltage. The output terminal of the operational amplifier is connected to the gate of the clamping power transistor. The first pole of the clamping power transistor is connected to the external low-voltage power supply and the internal equivalent load module, and the second pole is grounded. The first end of the VDD capacitor is connected to the external low-voltage power supply, and the second end is grounded. When the voltage-dividing signal of the external low-voltage power supply is higher than the internal clamping reference voltage, the output terminal of the operational amplifier stabilizes the voltage value of the external low-voltage power supply at a set voltage value through the clamping power transistor.

4. The segmented dimming switch control system according to claim 1, wherein: The power supply detection unit includes an undervoltage protection module, a switch switching detection module, and a digital module shutdown detection module. The undervoltage protection module is used to output an undervoltage protection signal to the pre-output driving unit when the external low-voltage power supply is lower than the undervoltage protection reference, so as to turn off the logic control signal of the pre-output driving unit. The switch switching detection module is used to output a low-level state switching control signal to the logic state latch and gating unit when it detects that the switching switch makes a level switch, so that the logic state latch and gating unit changes its state once. The digital module shutdown detection module is used to generate a shutdown signal to turn off the control system when it detects that the voltage of the external low-voltage power supply drops to the digital module shutdown reference, so that the control system enters the sleep mode.

5. The segmented dimming switch control system according to claim 4, characterized in that: The undervoltage protection reference is obtained by internal reference voltage division; the switch switching detection module detects whether the switching switch makes a level switch by comparing the voltage of the external low-voltage power supply and the threshold voltage of the field-effect transistor; the shutdown signal of the digital module is realized through a Schmitt inverter.

6. The segmented dimming switch control system according to claim 1, characterized in that: The multi-channel adjustable duty cycle generation unit first generates an envelope signal with a period of T through clock signal frequency division, where T is less than or equal to 10 ms, and then obtains envelope signals with multiple different duty cycles by changing the duty cycle of the envelope signal to form multiple signal levels. The switched buck LED control circuit is used to select different duty cycle signal levels according to the level switch of the control power supply as the logic control signal of the buck LED circuit, so as to realize the segmented dimming of the buck LED circuit.

7. The segmented dimming switch control system according to claim 1, wherein: The logic state latch and strobe unit includes a register-based state machine generation module, wherein the number of registers m of the state machine generation module and the number of duty cycle period signal gears n satisfy the following relationship: 2 m ≥n, where n is the number of duty cycle period signal gears and n is an integer greater than or equal to 1.

8. The segmented dimming switch control system according to claim 1, wherein: The step-down LED circuit includes an inductor module, a freewheeling diode module, a power device, a sampling resistor module, and an LED lighting module. The first end of the LED lighting module is connected to a medium-high voltage DC power supply and the negative electrode of the freewheeling diode module. The second end of the LED lighting module is connected to the first end of the inductor module. The second end of the inductor module is connected to the positive electrode of the freewheeling diode module and the first pole of the power device. The second pole of the power device is connected to the first end of the sampling resistor module, and the gate is connected to the switching step-down LED control circuit. The second end of the sampling resistor module is grounded.

9. A segmented dimming switch control system, characterized in that, The segmented dimming switch control system includes: a DC power supply, a switching switch, a switching step-down LED control circuit, and a step-down LED circuit; The DC power supply is used to provide a control power supply for the switching step-down LED control circuit; The switching switch is connected between the DC power supply and the switching step-down LED control circuit, and is used to control the rising and falling processes of the control power supply to achieve the level switching of the control power supply; The output end of the switching step-down LED control circuit is connected to the step-down LED circuit. The switching step-down LED control circuit is used to output a logic control signal to the step-down LED circuit according to the level switching of the control power supply, so as to achieve the segmented dimming of the step-down LED circuit; The DC power supply is a medium-high voltage DC power supply. The switching step-down LED control circuit includes: a low-voltage clamping unit, a power supply detection unit, a multi-channel adjustable duty cycle generation unit, a logic state latching and gating unit, a clock oscillator unit, and an output pre-driver unit; Among them, the low-voltage clamping unit is used to pull up the external low-voltage power supply to generate a stable low-voltage power supply for internal power supply of the control system. The power supply detection unit is used to detect whether the switching switch has a level switching and generate a state switching control signal. The clock oscillator unit is used to generate a clock signal to the multi-channel adjustable duty cycle generation unit. The multi-channel adjustable duty cycle generation unit generates multiple selectable periodic signals with different duty cycles after receiving the clock signal. The logic state latching and gating unit outputs a logic control signal with different duty cycles after receiving multiple state switching control signals and the selectable periodic signals. The logic control signal is used to control the turning on and off of the power tube of the step-down LED circuit, and different segmented dimming is achieved by adjusting the duty cycle of the logic control signal.

10. A segmented dimming switch control system, characterized in that, The segmented dimming switch control system includes: a DC power supply, a switching switch, a switching step-down LED control circuit, and a step-down LED circuit; The DC power supply is used to provide a control power supply for the switching step-down LED control circuit; The switching switch is connected between the DC power supply and the switching step-down LED control circuit, and is used to control the rising and falling processes of the control power supply to achieve the level switching of the control power supply; The output terminal of the switching buck-type LED control circuit is connected to the buck-type LED circuit. The switching buck-type LED control circuit is used to output a logic control signal to the buck-type LED circuit according to the level switching of the control power supply, so as to realize the segmented dimming of the buck-type LED circuit; The DC power supply has two power sources. Among them, the power supply of the switching buck-type LED control circuit is a low-voltage DC power supply, and the power supply of the buck-type LED circuit is a medium-high voltage DC power supply. The switching buck-type LED control circuit includes: a power supply detection unit, a multi-channel adjustable duty ratio generation unit, a logic state latching and gating unit, a clock oscillator unit, and an output pre-driver unit; Among them, the power supply detection unit is used to detect whether the switching switch has a level switch and generate a state switching control signal; the clock oscillator unit is used to generate a clock signal to the multi-channel adjustable duty ratio generation unit; the multi-channel adjustable duty ratio generation unit generates a plurality of selectable period signals with different duty ratios after receiving the clock signal; the logic state latching and gating unit outputs a logic control signal with different duty ratios after receiving a plurality of the state switching control signals and the selectable period signals. The logic control signal is used to control the turning on and off of the power transistor of the buck-type LED circuit, and different segmented dimming is realized by adjusting the duty ratio of the logic control signal.

11. The segmented dimming switch control system according to claim 9 or 10, characterized in that: The buck-type LED circuit includes an inductor module, a freewheeling diode module, and a power device LED lighting module. The first end of the LED lighting module is connected to the medium-high voltage DC power supply and the negative electrode of the freewheeling diode module. The second end of the LED lighting module is connected to the first end of the inductor module. The second end of the inductor module is connected to the positive electrode of the freewheeling diode module and the first pole of the power device. The second pole of the power device is directly grounded, and the gate is connected to the switching buck-type LED control circuit.

Images