• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to an electronic circuit for current regulation of the currents I 1 to I y which flow through one or more channels, each channel being equipped with one or more LEDs. The circuit consists of the electronic components MOSFET or transistor of another type, for example field effect transistor or bipolar transistor, operational amplifier, shunt resistor RS h, RC low-pass filter, PWM output "PWM" and microcontroller or other microcomputer for specifying the setpoint for the currents I 1 to I y. The setpoint specification for the currents I 1 to I y can also be generated by another component or another electronic circuit. The electronic circuit is used for lighting purposes.
    公开号:CH715453A2
    申请号:CH01530/18
    申请日:2019-01-04
    公开日:2020-04-15
    发明作者:Wunderle Damian
    申请人:Wunderle Damian；
    IPC主号:
    专利说明:

    Abbreviations
    [0001] LED = light-emitting diode
    Technical field
    The invention relates to an electronic circuit for controlling LED lights with one or more channels. If several channels are used, they can be equipped with different light colors, for example. The invention can be used for undimmed and for dimmed systems. One possible area of application is general lighting in vehicles.
    State of the art
    It is state of the art that DC / DC converters with constant current output are used in DC-operated LED lighting. The majority of these DC / DC converters consist of Boost, Buck, Buck Boost, SEPIC or Flyback circuits. Each of these DC / DC converters requires at least one inductor, a fast-switching transistor and a component that drives the fast-switching transistor. Therefore, the DC / DC converters require a lot of space and are relatively expensive. In addition, suitable measures are required to reduce electromagnetic radiation from the high-frequency switching current. The regulated constant current I1 to Iy; see Fig. 1, at the output of each DC / DC converter is passed through a number (one or more) of connected LEDs. The connection of the LEDs can consist of one or more series connections, one or more parallel connections or one or more combinations of series connection and parallel connection. The respective output current I1 to Iy, see FIG. 1, can be constant over time, that is to say undimmed, or can change over time, that is, dimmed. LEDs that are used in general lighting have an almost linear relationship between the emitted luminous flux and their forward electrical current, so the luminous flux can be influenced by the forward current and a linear relationship can be assumed as an approximation. For a number y of channels in an LED luminaire or in LED lighting, a number y of DC / DC converters is required, see FIG. 1.
    Example: If you want to build a multichannel light, consisting of a number y = 4 of channels for operating y = 4 different light colors, then this requires y = 4 pieces of DC / DC converter, each of which has an output ( Currents Ii to I4), on which one or more LEDs are operated. This makes ambient light feasible with, for example, the main colors warm white and cold white and with the mood colors red and blue. This can be used, for example, to create a blue sky, an evening red, a bright white light and a warm yellow light. However, the amount of components, the space required and the costs for the y = 4 required DC / DC converter are very high in this example.
    Object of the invention
    The object of the invention is to divide the current I on the channel currents I1bis Iy, see Fig. 2, temporally changeable, that is, the current I can change over time (dimming of the total current I) and it can Change the distribution of the current I to the currents I1 to Iy over time (change in the individual channel currents I1 to Iy, that is to say dimming the individual channel currents I1 to Iy by changing the setpoint for I1 to Iy). The invention realizes the solution of the task in a highly efficient manner, that is to say with little loss, with few and inexpensive components, with little space requirement for the components, with the avoidance of EMC radiation, with a current control of high accuracy for each channel current I1 to Iy, and with a very small size Minimum current for I1 to Iy and therefore with a small minimum luminous flux on the number of LEDs connected to each channel (one or more LEDs). The invented circuit can also be operated with y = 1, that is to say with one channel, the advantage then being that the current I1 can be regulated with little effort and with a high degree of accuracy.
    Brief description of the invention
    The invented circuit divides the direct current I into the direct currents I1 to Iy. Only one DC / DC converter is required. The invented circuit works through a loss-optimized and cost-effective current control for each channel 1 to y and provides regulated currents I1 to Iy at the input1 to inputy connections. The total current I flows out at the output of the invention. See Figures 2 and 3.
    List of drawings
    [0007]<tb> Fig. 1: <SEP> State of the art: Number y required DC / DC converter for number y of light channels.<tb> Fig. 2: <SEP> application of the invention with a DC / DC converter.<tb> Fig. 2a: <SEP> As Fig. 2, but invention above the LEDs.<tb> Fig. 3: <SEP> electronic circuit of the invention.<tb> Fig. 4: <SEP> Real measurement on invented electronic circuit.
    Description of the drawings
    Fig. 1 shows DC / DC converters with constant current outputs I1 to Iyn according to the prior art. The DC / DC converters each have a constant current output (plus and minus), to which a number (one or more) LEDs are connected. The output voltage ULEDS1 and the output current I1 result at the DC / DC converter 1. Several DC / DC converters are required for several channels.
    Fig. 2 shows the DC / DC converter 1 with constant current output (plus and minus), to which a number y of channels are connected, with one or more LEDs being connected to each channel. The current distribution between the channels is done by the invention (invented electronic circuit). The invention (invented electronic circuit) has the following connections for power distribution: inputs: input 1 to input y for connecting the LEDs; Outputs: an output which is connected to the minus of the DC / DC converter. There are a number y of current sources with the currents I1 to Iy. The result is the output voltage U and the output current I on the DC / DC converter. The voltages ULEDS1 to ULEDSyan are on the LEDs of the individual channels (in the drawing, only ULEDSye was drawn in for reasons of space) and the voltages U1 to Uyan form within the invented electronic circuit the power sources.The following applies: ULEDs1 + U1 = U; ULEDS2 + U2 = U; ...; ULEDSy + Uy = U;in addition, I1 + I2 + ... + Iy = I.
    Fig. 2a as Fig. 2, but invention above the LEDs. Here, the invention is connected to the positive pole of the DC / DC converter.
    Fig. 3 shows the invention (invented electronic circuit), consisting of the inputs input 1 to input y for connecting the LEDs and an output which is connected to the minus of the DC / DC converter. Fig. 3 also shows the electronic components of the invention (invented electronic circuit), these are a MOSFET or other transistor, an operational amplifier, a shunt resistor RSh for each channel. In addition, an RC low-pass filter, a PWM output «PWM» connected to the microcontroller and a microcontroller.
    Fig. 4 shows an example of a real efficiency measurement of a circuit built in the laboratory with y = 2 channels. Channel 1 is equipped with 16 warm white LEDs and channel 2 is equipped with 16 cold white LEDs. The characteristic curve shown shows the characteristic curve of a single LED, which was determined in the measurement.
    Detailed description of the invention
    The invention consists of a circuit with a number y of channels. The number of channels y is an integer with the minimum value 1. It applies that the sum of all input currents I1 to I corresponds to the output current I of the DC / DC converter.
    [0014] The invented electronic circuit regulates the currents I1 to Iy.
    The basic control principle is such that a microcontroller or another setpoint generator for the input currents I1bis Iyden specifies the setpoint, then the operational amplifiers each the currents I1bis Iyrechte to their respective setpoint, and then the DC / DC converter automatically regulates itself that it always reaches the current I at the output, which corresponds to the sum of all currents I1 to Iy.
    The current control from channel 1 to channel y is realized by a number y of regulated current sources, which work as regulated current sinks. The regulated current sink of each channel consists of at least one MOSFET or other transistor, an operational amplifier, a shunt RSh, an RC low-pass filter and a PWM output (controlled by the microcontroller or another microcomputer) PWM1 to PWMy. The PWM outputs PWM1 to PWMy can either be integrated in the microcontroller or implemented via external hardware. For control-related reasons, further signals can be fed to the microcontroller, for example the currents I1 to Iy or the current I or the voltage U, see FIGS. 2 and 3 or the gate voltages of the respective MOSFETs or other electrical variables or the value of other physical variables. The MOSFET with the connected shunt RSh and the connected operational amplifier form a regulated current source, which is always operated as a current sink, i.e. like an adjustable electronic load, with the actual value (voltage proportional to the actual current) at the negative input of the operational amplifier, with the setpoint (voltage proportional to the nominal current) at the positive input of the operational amplifier and with gate voltage for the MOSFET at the output of the operational amplifier. Because the operational amplifier is operated in negative feedback, the operational amplifier always tries to keep the voltage at the positive input the same as the voltage at the negative input of the operational amplifier.
    The following applies to each channel: Usollist is the voltage at the positive input of the operational amplifier compared to GND.
    For the setpoint of the channel current I1, the following applies, for example: I1Soll = U1Soll / R1Sh.
    [0019] The shunt RShd thus determines the ratio of the target voltage and the target current of each current sink of the respective channel.
    For each channel: Uistist is the voltage at the negative input of the operational amplifier compared to GND.
    The following applies, for example, to the actual value of the channel current I1: I1Ist = U1Ist / R1Sh.
    The shunt RShund the upstream MOSFET behave like a series resistor to the load connected to the respective channel, consisting of one or more LEDs. Each of the 1 to y regulated current controllers receives its setpoint from a microcontroller or another microcomputer or from another setpoint generator. The microcontroller gives the setpoints for I1 to Iyvor in the form of a PWM signal on its respective output pin. The microcontroller calculates the duty cycle of the PWM signal, i.e. the ratio of the pulse duty cycle to the total pulse duration. This PWM voltage (it is a square wave voltage) of each channel is converted into an analog voltage for each channel by an RC low-pass filter. This analog voltage corresponds to the target current of the respective channel. The analog voltage after the RC low-pass filter is proportional to the duty cycle of the PWM signal. For example, a duty cycle of 20% can be set with a microcontroller and an analog voltage of 20% of the operating voltage of the microcontroller can be obtained as a voltage after the RC low-pass filter; The prerequisite for this is, of course, that if the logic "high" is at the PWM output, the full operating voltage of the microcontroller is present and if the logic "low" is zero volts at the PWM output, which is almost the case in practice. If the microcontroller is supplied with 5 V, for example, then there is an analog voltage of (20% / 100%) * 5 V = 1 V. This analog DC voltage from IV is at the positive input of the operational amplifier, which then tries to measure the current of the Adjust the channel to a value according to the following equation: Isoll = UOperationsamplifierPositiverEingang / RShunt, for example Isoll = 1 V / 10 Ohm = 100 mA. The invented electronic circuit takes advantage of the fact that white light is predominantly used in general lighting and only very small proportions of colored light are added. Explanation for the high efficiency of the circuit, see Fig. 4, is that the white LEDs of different light color (e.g. cold white, warm white) used in general lighting for main light generation have the same or almost the same characteristics forward current = f (forward voltage). The voltages ULEDS1 to ULEDsy thus move in similar value ranges, so that the voltages at the current sinks U1 to Uy do not become too different and good efficiency is achieved. The number of LEDs for the electronic circuit of this invention is dimensioned (definition of n1, n2 to n3, see Fig. 2) so that the total forward voltages of the LEDs ULEDs1 to ULEDs are approximate by properly selecting the number of LEDs per channel, at least in the main operating point of the application are equally high, so that the voltages at the current sinks U1 to Uyklein can be kept to minimize losses.
    Color mixtures can thus be achieved with white LEDs of different light colors with a typical controller efficiency of over 96%, see FIG. 4.
    [0024] The present invention can also operate individual channels with very small currents up to minimum values of approximately 1% of the maximum current of the respective channel. This is possible because, in practice, the accuracy of the regulation of the currents I1 to Iy essentially depends only on the accuracy of the shunt resistor RSh1 to RShy and on the accuracy of the operating voltage of the microcontroller. If one chooses an electronic circuit according to the “state of the art”, see FIG. 1, then commercially available low-cost DC / DC converters cannot reach minimum currents of 1% with usable accuracy, values from 5% to 10% are often only possible here analog dimming. With PWM dimming, DC / DC converters according to the "state of the art" can achieve dimming values of 1%, but PWM dimming brings a number of disadvantages, such as high EMC radiation, stroboscopic effect, noise generation from electronic components and the like Risk of triggering epileptic seizures in people with a corresponding previous illness.
    The invented electronic circuit realizes the solution of the task highly efficiently, that is to say with little loss.
    The circuit requires only a few and inexpensive components. Because of the few components required, the space required is small. Because no clocked current flows in the electronic circuit of this invention, there is no EMC radiation.
    The invented electronic circuit can also be operated with y = 1, that is to say with one channel, in order to be able to regulate the current I1 with little effort and with high accuracy.
    [0028] The luminous flux of an LED is approximately proportional to the forward current of the LED.
    Because of the approximately linear relationship between forward current and emitted luminous flux of an LED, the brightness of an LED can be proportionally influenced with sufficient accuracy by the current through the LED.
    In practice, this means that an LED with 50% forward current emits half the luminous flux on the same LED with sufficient accuracy compared to the 100% forward current on the same LED.
    In practice, for example, each channel will be operated with LEDs with their own light color. For example, channel 1 for warm white LEDs, channel 2 for cold white LEDs, ...
    Other applications are also possible with this circuit.
    The forward voltage on an LED, which is operated with constant current, naturally has a large number of influencing and disturbance variables, such as the semiconductor material, the junction temperature, component fluctuations, different types of binnings, ...
    All these disturbances are compensated for by the circuit described here.
    权利要求:
    Claims (2)
    [1]
    1. Electronic circuit for operating LEDs for lighting purposes, which is characterized by one or more channels according to FIGS. 2 and 3 (one or more LEDs are operated on each channel), using a current control circuit for the currents I1 to Iyn according to FIG. 3, consisting of at least the following electronic components for each channel: a MOSFET or a transistor of another type, for example a field effect transistor or a bipolar transistor, an operational amplifier, a shunt resistor RSh, an RC low-pass filter or another filter, a PWM Output (for controlling the setpoint at the positive input of the operational amplifier) integrated in a microcontroller or other microcomputer or controlled by a microcontroller or other microcomputer. Instead of the PWM output and the RC low-pass filter according to FIG. 3, another circuit can also be used which generates the setpoint for the respective channel (setpoint for I1 to Iy) by the circuit generating a voltage which is applied to the positive input of the respective operational amplifier is created. The regulation with the help of at least one operational amplifier per channel regulates the currents I1 to Iy and the DC / DC converter is controlled in such a way that the current I = I1 + I2 + ... + oxygen is generated at its output, see Fig. 2.
    [2]
    2. Electronic circuit according to claim 1, wherein, in contrast to FIG. 2, the invention is arranged in the circuit diagram above, that is to say the invention is connected directly to the positive pole of the DC / DC converter, see FIG. 2a.The circuit is then not arranged according to Fig. 3, but mirrored. That means: The current path of each LED channel leads from the positive pole of the DC / DC converter via the shunt resistor RSh, then via the MOSFET (or transistor of another type, for example a field effect transistor or bipolar transistor) and then via the LEDs of the respective channel to the negative pole of the DC / DC converter. Other variants are also possible for the sequence of the current-carrying components of the current paths from the positive pole of the DC / DC converter to the negative pole of the DC / DC converter.
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    同族专利:
    公开号 | 公开日
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2021-08-31| AZW| Rejection (application)|
    优先权:
    申请号 | 申请日 | 专利标题
    CH9402018|2018-07-31|
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