Isolated Dimming Signal Detection Circuit and Detection Method Based on Time-Domain Parameters

Abstract

The present invention discloses an isolated dimming signal detection circuit based on time-domain parameters. The isolated dimming signal detection circuit at least includes: a transformer, a primary control unit, and a secondary control unit. Among them, the transformer includes a primary winding and a secondary winding. A first end of the primary winding and a second end of the primary winding are provided on the primary winding. A voltage comparison unit and a PWM signal control unit are provided in the primary control unit. Moreover, the primary control unit inputs a driving voltage V dd to the first end of the primary winding, and the second end of the primary winding is connected to the voltage comparison unit and the PWM signal control unit. The secondary control unit at least includes a diode and a dimming voltage V dim input terminal.

Description

Technical Field

[0001] The present invention relates to the technical field of LED dimming, and particularly to an isolated dimming signal detection circuit based on time-domain parameters. Background Art

[0002] In existing LED lighting devices, an isolated power supply method is generally adopted. An isolated power supply circuit uses a transformer to convert the mains voltage into a lower output voltage for powering a load. Due to the presence of the transformer in the isolated power supply circuit, the secondary circuit is isolated from the primary circuit, which has high safety. However, the isolated power supply circuit needs to control the primary switch chip to adjust the output. When driving a light-emitting diode using an isolated circuit, a reference signal needs to be set to control the primary switch and thus control the dimming brightness. When the brightness needs to be adjusted, the voltage value set by the regulator needs to be detected and the detected value is fed back to the primary chip to match the dimming brightness value set by the primary chip.

[0003] There are two types of dimming detections in existing lighting products. One is to use a dedicated chip on the secondary side in cooperation with an optocoupler to feedback a dimming voltage signal to the primary chip. The advantage of this solution is that the dimming curve effect is good, but the disadvantage is that it requires a secondary chip and an optocoupler, and the cost is relatively high. And as Figure 1 shown, this solution utilizes the characteristic that the voltages at both ends of the transformer are proportional. When the inductor current changes, the voltage characteristic at both ends of the inductor L m1 is detected (the voltage difference is proportional to the voltage difference at both ends of L m2 ), to obtain V DIMMER +V d , and thus obtain the value of the dimming voltage signal V DIMMER . This high-voltage differential detection method has high requirements for the design of the detection circuit.

[0004] Another solution is that in the 0-10V dimming detection solution for the lighting industry in the prior art, in order to pursue cost reduction, in some working conditions where the dimming curve requirements are not high, the secondary chip and related circuits can be omitted, and only an isolation transformer is used to replace the secondary chip and the optocoupler to reduce the cost. This solution realizes the detection of the dimming voltage by detecting the voltages at each node in different working states of the transformer. Obviously, the accuracy of this solution is poor, and it cannot be adaptively adjusted for different systems.

[0005] Therefore, there is a need in the art for a new dimming voltage signal detection method that can accurately detect the dimming voltage only relying on the system parameters of the primary winding circuit and save the secondary winding detection circuit to reduce the overall circuit structure cost. Summary of the Invention

[0006] The present invention provides an isolated dimming signal detection circuit based on time-domain parameters. The isolated dimming signal detection circuit configures relevant time parameters required for the detection circuit based on the internal drive voltage value on the primary winding side and system application parameters. And the dimming voltage value to be detected is obtained based on the system discrete current operating mode and system external parameters. Thus, without setting an additional secondary winding detection circuit, it is possible to accurately detect the dimming voltage signal on the secondary winding side only relying on the parameters of the primary winding circuit system.

[0007] Based on the above technical objectives, the present invention provides an isolated dimming signal detection circuit based on time-domain parameters, and the isolated dimming signal detection circuit at least includes: a transformer, a primary control unit, and a secondary control unit;

[0008] Wherein, the transformer includes a primary winding and a secondary winding, and a first end and a second end of the primary winding are provided on the primary winding; a voltage comparison unit and a PWM signal control unit are provided in the primary control unit;

[0009] Moreover, the primary control unit inputs the drive voltage V dd to the first end of the primary winding, and the second end of the primary winding is connected to the voltage comparison unit and the PWM signal control unit;

[0010] The secondary control unit at least includes a diode and a dimming voltage V dim input terminal.

[0011] In one embodiment, the voltage comparison unit includes a voltage division unit and a comparator unit. The voltage division unit divides the voltage V samp at the second end of the primary winding by a preset ratio and inputs it to the comparator unit. At the same time, the drive voltage V dd is also divided by the same preset ratio and input to the comparator unit, and the comparator unit outputs a comparison voltage V det .

[0012] In one embodiment, measure the time difference between when the comparison voltage V det becomes high after the high-level duration T on ends and the first time it becomes low, and perform calibration to obtain the duration T off when the current value of the secondary winding drops from the peak to zero.

[0013] In one embodiment, calculate the dimming voltage V input to the secondary control unit according to the drive voltage V dd , the voltage V samp at the second end of the primary winding, the duration T on , the duration T off , and the fixed voltage drop V d of the diode of the secondary windingdim 。

[0014] The present invention also provides an isolated dimming signal detection method based on time domain parameters, and the method includes:

[0015] Step S100, applying a driving voltage V to the first end of the primary winding of the transformer dd , and detecting the voltage V at the second end of the primary winding samp ;

[0016] Step S101, comparing the voltage V at the second end of the primary winding samp with the driving voltage V dd to obtain a comparison voltage V det ;

[0017] Step S102, detecting the time difference T between the time when the comparison voltage V det becomes high after the high-level duration T on ends and the first time it becomes low r_mes ;

[0018] Step S103, correcting the time difference T r_mes to obtain the duration T when the current value I of the secondary winding L2 L2 drops from the peak to zero off ;

[0019] Step S104, calculating the dimming voltage V according to the driving voltage V dd , the voltage V at the second end of the primary winding samp , the duration T on , the duration T off and the fixed voltage drop V of the diode of the secondary winding d . The specific calculation process satisfies: dim .

[0020]

[0021] In one embodiment, in the above step S101, the voltage V at the second end of the primary winding samp is divided by a preset ratio and then input to the comparator unit. At the same time, the driving voltage V dd is also divided by the same preset ratio and then input to the comparator unit, and the comparator unit outputs the comparison voltage V det ;

[0022] In one embodiment, the process of correcting the time difference T r_mes includes using a non-volatile memory to store the calibrated error ΔT, and calibrating the duration T output by the comparator using the pre-calibrated error ΔT, so as to obtain the duration T r_mes off .

[0023] Compared with the prior art, one or more embodiments of the present invention may have the following advantages:

[0024] The present invention obtains a comparison voltage value V by setting a voltage comparison unit det , and obtains the duration from the peak value of the secondary winding current to zero by analyzing the comparison voltage value V det . Furthermore, the dimming voltage value input to the secondary winding can be directly calculated. In the present invention, there is no dedicated dimming voltage detection circuit to detect the dimming voltage, and the dimming voltage value V can be calculated by fully reusing the drive control circuit on the primary winding side dim . That is, it saves circuit costs and improves the detection accuracy of the dimming voltage value V dim . At the same time, the voltage V at the second end of the primary winding can be detected through the second end 11 of the primary winding samp , and the current I of the primary winding L1 can also be detected L1 . By detecting the current value, the inductance value of the primary winding L1 can be further determined, and by adjusting the internal high-level duration T on and the cycle duration T p of the PWM signal, the system applicability and flexibility can be achieved

[0025] Other features and advantages of the present invention will be described in the following description, and in part, will be obvious from the description, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the description, claims, and drawings BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are used to provide a further understanding of the present invention, and constitute a part of the description. Together with the embodiments of the present invention, they are used to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0027] Figure 1 is a schematic structural diagram of a dimming voltage signal generation circuit in the prior art;

[0028] Figure 2 is a schematic structural diagram of a dimming voltage signal detection circuit of the present invention;

[0029] Figure 3 is a schematic diagram of signal waveforms in the dimming voltage signal detection circuit of the present invention;

[0030] Figure 4 is a schematic flow diagram of a dimming voltage signal detection method of the present invention DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Thus, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be referred to as the second element, component, region, layer or part. And when discussing the second element, component, region, layer or part, it does not imply that the present invention necessarily has a first element, component, region, layer or part.

[0033] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. are used herein for convenience in describing the relationship of one element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientation shown in the figures, spatial relationship terms are intended to include different orientations of the device in use and operation. For example, if the device in the figures is flipped, then an element or feature described as "under" or "beneath" or "below" other elements or features will be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "below" can include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientation) and the spatial descriptors used herein are to be interpreted accordingly.

[0034] The purpose of the terms used herein is only to describe specific embodiments and is not a limitation of the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, identify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. As used herein, the term "and / or" includes any and all combinations of the related listed items.

[0035] Example 1

[0036] As Figures 2 - 3 shown, the dimming voltage signal detection circuit of the present invention includes: a transformer 1, a primary control unit 2, and a secondary control unit 3. The transformer 1 includes a primary winding L1 and a secondary winding L2. A first end 10 of the primary winding and a second end 11 of the primary winding are provided on the primary winding. A voltage comparison unit 20 and a PWM signal control unit 21 are provided in the primary control unit 2, and the primary control unit 2 inputs a driving voltage V dd to the first end 10 of the primary winding, and the second end 11 of the primary winding is connected to the voltage comparison unit 20 and the PWM signal control unit 21. The voltage comparison unit 20 includes a voltage division unit and a comparator unit. The voltage division unit divides the voltage V samp at the second end of the primary winding by a preset ratio and inputs it to the comparator unit. At the same time, the driving voltage V dd is also divided by the same preset ratio and input to the comparator unit, and the comparator unit outputs a comparison voltage V det . The PWM signal control unit 21 includes at least one switch control element, and the switch controls the second end 11 of the primary winding to be grounded according to the PWM signal. The duty cycle Duty of the PWM signal is expressed as: Duty = T on / T p . Wherein, the T on is the high-level duration in a PWM cycle of the PWM signal, and the T p is the total duration of a PWM cycle of the PWM signal. The secondary control unit 3 includes at least one diode and an input terminal of the dimming voltage V dim .

[0037] In the discontinuous conduction mode (DCM), the volt-second balance relationship of the transformer 1 can be expressed as:

[0038] (V dd -V samp )×T on =(V dim +V d )×T off ;

[0039] That is:

[0040]

[0041] Among them, V d is the voltage drop across the diode in the secondary control unit 3, which is a fixed device parameter value. T off is the duration during which the current value I L2 of the secondary winding L2 drops from the peak value to zero.

[0042] In this embodiment, the driving voltage V dd , the voltage V at the second end of the primary winding samp , and the high-level duration T on are all internal parameters of the primary winding side circuit and can be accurately detected on the primary winding side. The duration T off needs to be further calculated in the present invention.

[0043] As Figure 4 shown in the schematic diagram of the signal waveform in the dimming voltage signal detection circuit of the present invention. Based on the physical characteristics of the transformer: the voltage at the second end of the primary winding V samp will become high when the current I L1 in the primary winding L1 suddenly becomes zero, and will oscillate when the current I L2 in the secondary winding L2 becomes zero. The comparison voltage V det output by the voltage comparison unit 20 of the primary control unit 2 increases when the current I L1 in the primary winding L1 becomes lower, and oscillates and becomes lower when the current I L2 in the secondary winding L2 passes through zero. The duration T off that needs to be detected in the present invention is the time difference T det between the time when the comparison voltage V on becomes high after the end of the high-level duration T r_off and the first time it becomes low. However, due to the error ΔT of the comparator unit itself. Actually, the time difference between the time when the comparison voltage V det becomes high after the end of the high-level duration T on and the first time it becomes low is T r_mes = T r_off ± ΔT.

[0044] Since the error ΔT is the offset of the comparator flip point caused by semiconductor manufacturing process deviations (such as etching accuracy, etc.), this error ΔT can be pre-calibrated by measurement. Thus, the error ΔT can be removed by digital calibration. The specific digital calibration method includes storing the calibrated error ΔT using a non-volatile memory (such as OTP, eFues, etc.), and calibrating the duration T r_mes output by the comparator using the pre-calibrated error ΔT to obtain the duration T r_off .

[0045] In the present invention, the voltage V at the second end of the primary winding can be detected through the second end 11 of the primary winding samp , and at the same time, the current I L1 in the primary winding L1 can also be detected. By detecting the current value, the inductance value of the primary winding L1 can be further determined, and by adjusting the internal high-level duration T of the PWM signalon and the total cycle duration T of the PWM signal p to achieve system applicability and flexible expansion.

[0046] Such as Figure 4 The dimming voltage signal detection method of the present invention shown includes:[[]]

[0047] S100, applying a driving voltage V to the first end of the primary winding of the transformer dd , and detecting the voltage V at the second end of the primary winding samp ;

[0048] S101, comparing the voltage V at the second end of the primary winding samp with the driving voltage V dd to obtain a comparison voltage V det ; Specifically, the voltage V at the second end of the primary winding is divided by a preset ratio and then input into the comparator unit. At the same time, the driving voltage V samp is also divided by the same preset ratio and then input into the comparator unit, and the comparator unit outputs the comparison voltage V dd det ;;

[0049] S102, detecting the time difference T between the time when the comparison voltage V det becomes high after the high-level duration T on ends and the first time it becomes low r_mes ;

[0050] S103, correcting the time difference T r_mes to obtain the duration T L2 when the current value I of the secondary winding L2 drops from the peak to zero off ;

[0051] S104, calculating the dimming voltage V dd according to the driving voltage V samp , the voltage V at the second end of the primary winding on , the duration T off , the fixed voltage drop V of the diode of the secondary winding d and the duration T dim . The specific calculation process satisfies:[[]]

[0052]

[0053] The present invention can be any possible system, method, and / or computer program product at the integrated technical detail level. The computer program product can include a computer-readable storage medium (or multiple media) having computer-readable program instructions thereon for causing a processor to execute aspects of the present invention.

[0054] A computer-readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer-readable storage medium can be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing devices. A non-exhaustive list of more specific examples of computer-readable storage media includes the following: a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), a memory stick, a floppy disk, a mechanically encoded device such as a punched card or raised structures in grooves having instructions recorded thereon, and any suitable combination of the foregoing. A computer-readable storage medium, as used herein, shall not be construed to be a transitory signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through an optical fiber cable), or an electrical signal transmitted through a wire.

[0055] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to a corresponding computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium within the corresponding computing / processing device.

[0056] The computer-readable program instructions for performing the operations of the present invention may be assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuits, or source code or object code written in any combination of one or more programming languages and procedural programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server. In the latter case, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may make a connection to an external computer (e.g., through the Internet using an Internet service provider). In some embodiments, an electronic circuit, including, for example, a programmable logic circuit, a field-programmable gate array (FPGA), or a programmable logic array (PLA), may execute the computer-readable program instructions by utilizing the state information of the computer-readable program instructions to personalize the electronic circuit, thereby performing various aspects of the present invention.

[0057] Aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0058] These computer-readable program instructions may be provided to a processor of a computer, or other programmable data processing device, to produce a machine, such that the instructions executed via the processor of the computer or other programmable data processing device create means for implementing the functions / acts specified in the flowchart and / or block Figure 1 diagrams. These computer-readable program instructions may also be stored in a computer-readable storage medium that can direct a computer, a programmable data processing device, and / or other devices to operate in a particular manner, such that the computer-readable storage medium in which the instructions are stored comprises a manufacture including instructions for implementing aspects of the functions / acts specified in the flowchart and / or block diagrams.

[0059] The computer-readable program instructions may also be loaded onto a computer, other programmable data processing device, or other device to cause a series of operational steps to be performed on the computer, other programmable device, or other device to produce a computer-implemented process, such that the instructions executed on the computer, other programmable device, or other device implement the functions / acts specified in the flowchart and / or block diagrams.

[0060] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagram may represent a module, segment, or portion of instructions that includes one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, in fact, two consecutive blocks shown may be completed as one step, concurrently, substantially concurrently, or sometimes in a reverse order, depending on the functions involved, in a partially or fully time-overlapping manner. It will also be noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by a system based on dedicated hardware that performs the specified functions or actions or a combination of dedicated hardware and computer instructions.

[0061] Embodiments of the present application are described with reference to the flowcharts and / or block diagrams of methods, apparatuses (devices), and computer program products according to embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, and combinations of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce a means for implementing the specified function in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0062] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including an instruction means that implements the specified function in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0063] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the specified function in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

Claims

1. An isolated dimming signal detection circuit based on time-domain parameters, characterized in that The isolated dimming signal detection circuit at least includes: a transformer, a primary control unit, and a secondary control unit; Among them, the transformer includes a primary winding and a secondary winding. A first end of the primary winding and a second end of the primary winding are provided on the primary winding; a voltage comparison unit and a PWM signal control unit are provided in the primary control unit; Moreover, the primary control unit inputs the driving voltage V dd to the first end of the primary winding, and the second end of the primary winding is connected to the voltage comparison unit and the PWM signal control unit; The secondary side control unit includes at least one diode and a dimming voltage V dim input terminal; The voltage comparison unit includes a voltage division unit and a comparator unit. The voltage division unit divides the voltage V at the second end of the primary winding by a preset ratio and then inputs it into the comparator unit. At the same time, the driving voltage V samp is also divided by the same preset ratio and input into the comparator unit, and the comparator unit outputs a comparison voltage V dd ; det ; Measure and compare voltage V det At the high-level duration T on After it ends, measure the time difference between the rising edge and the first falling edge and perform calibration to obtain the duration T during which the current value of the secondary winding drops from the peak to zero off ; According to the driving voltage V dd , the voltage V at the second end of the primary winding samp , the duration T on , the duration T off and the fixed voltage drop V of the diode in the secondary winding d calculate the dimming voltage V input to the secondary control unit dim .

2. An isolation dimming signal detection method for the isolation dimming signal detection circuit according to claim 1, characterized in that The method includes: Step S100, apply a driving voltage V to the first end of the primary winding of the transformer dd , and detect the voltage V at the second end of the primary winding samp ; Step S101, compare the voltage V at the second end of the original side winding samp with the driving voltage V dd to obtain a comparison voltage V det ; Step S102, detect the comparison voltage V det at the high-level duration T on after the end, the time difference T between going high and going low for the first time r_mes ; Step S103, correct the time difference T r_mes to obtain the current value I of the secondary winding L2 L2 of the duration T from the peak value dropping to zero off ; Step S104, according to the driving voltage V dd , the voltage V samp at the second end of the primary winding, the duration T on , the duration T off and the fixed voltage drop V d of the diode in the secondary winding, calculate the dimming voltage V dim ; the specific calculation process satisfies:

3. The isolation type dimming signal detection method according to claim 2, wherein, In the above step S101, the voltage V at the second end of the primary side winding samp is divided by a preset ratio and then input into the comparator unit. At the same time, the driving voltage V dd is also divided by the same preset ratio and input into the comparator unit, and the comparator unit outputs a comparison voltage V det .

4. The isolation type dimming signal detection method according to claim 3, wherein For the time difference T r_mes The process of calibration includes using a non-volatile memory to store the calibrated error ΔT, and calibrating the duration T output by the comparator r_mes using the pre-calibrated error ΔT to obtain the duration T off .

5. A computer-readable storage medium having computer instructions stored thereon, wherein, When the computer instruction is executed by a processor, the steps of the method according to any one of claims 2-4 are implemented.

6. An LED dimming control system, characterized in that The LED dimming control system includes the isolated dimming signal detection circuit according to any one of claim 1.

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