This application claims the benefit of Taiwan Patent Application Serial No. 098130654, filed Sep. 11, 2009, the subject matter of which is incorporated herein by reference.
(1) Field of the Invention
The invention relates to an electronic load and the method for operating the electronic load, and more particularly to the electronic load that is capable of simulating characteristics of a light emitting diode (LED).
(2) Description of the Prior Art
The LED is featured in high conversion efficiency, short reaction time, high glimmer frequency, energy-saving, etc. In fact, the LED has taken over various traditional lighting equipments such as tungsten lamps, fluorescent lamps and so on. For the voltage-current characteristics of the LEDs are much different from those of the traditional lighting equipments, power sources for those traditional lighting equipments can't be directly applied to the LEDs.
In the art, the testing upon an LED power source usually uses a real LED. However, the voltage-current characteristics of LEDs vary to some extents, particularly with the materials. Besides, individual manufacturers may have different standards for the LED, by which characteristic differences among LEDs in the marketplace can be foreseen. Further, the impedance of the LED is dependent on the temperature, the service time, and some external factors. Owing to the facts mentioned above, using a real LED as a device for testing a prospective power source is unable to justify the testing of simulation results.
In electronic industry, though various electronic loads are available in simulating respective electronic elements, yet there is no such electronic load for simulating an LED. In the past, the operator usually uses a constant-resistance (CR) mode electronic load to generate a straight line having a slope m in the voltage-current plot, and adjust the slope to approximate the LED characteristic curve.
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It is an object of the present invention to provide an electronic load capable of simulating signals having a voltage value and a current value approximating to a characteristic curve of an LED at any moment, so as to substantially simulate a real LED can do.
In this invention, the electronic load is powered by a power source, and receives an input signal. The electronic load comprises a processor, an amplifier, a voltage measurement unit, and a control unit. The processor further includes a parameter control unit.
The parameter control unit electronically couples with the control unit. The control unit electronically couples between the voltage measurement unit and the amplifier. The voltage measurement unit electronically couples with the power source so as able to measure/monitor the voltage of the input signal.
The control unit further includes a forward voltage processor and an equivalent impedance processor. The parameter control unit further includes a forward voltage controller and an equivalent impedance controller. The forward voltage controller electronically couples with the forward voltage processor, and the equivalent impedance controller electronically couples with the equivalent impedance processor.
The electronic load receives a set of control commands or parameters, including a forward voltage parameter and an equivalent impedance parameter. The forward voltage processor and the equivalent impedance processor receive the parameters to generate an adjustment command, and forward the adjustment command to the amplifier.
The amplifier adjusts/magnifies the input signal, according to the adjustment command, so as to convert it into a corresponding simulation signal to output therefrom, and further to trigger the power source outputting a power to the electronic load according to the simulation signal.
The forward voltage of the simulation signal equals to the forward voltage parameter, and the slope of the simulation signal in the voltage-current plot equals to the equivalent impedance parameter. As a result, the simulation signal would better present the characteristics of a real LED.
By importing different control commands, this electronic load would output the simulation signal in accordance with the control command. Hence, this invention of the electronic load can simulate different LEDs.
All these objects are achieved by the electronic load described below.
The present invention will be specified with reference to its preferred embodiment illustrated in the drawings, in which:
The invention disclosed herein is directed to an electronic load for simulating characteristics of an LED and the method for operating the electronic load. In the following description, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by one skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. Under such a circumstance, there are two preferred embodiments described herein applied for the embodiment is provided to illustrate the present invention in details.
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As long as the LED string can be successfully simplified as the aforesaid combination of the resistance and the voltage source, the characteristic curve of the LED string in a voltage-current plot can be obtained.
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The electronic load 1 comprises a processor 11, a control unit 13, an amplifier 14, and a voltage measurement unit 15. The processor 11 further includes a parameter control unit 111. The parameter control unit 111 further includes a forward voltage controller 1111 and an equivalent impedance controller 1112. The control unit 13 further includes a forward voltage processor 131 and an equivalent impedance processor 132.
The forward voltage processor 131 electronically couples among the forward voltage controller 1111, the equivalent impedance processor 132 and the voltage measurement unit 15 connected with the power source 2. The equivalent impedance processor 132 electronically couples among the forward voltage processor 131, the equivalent impedance controller 1112 and the amplifier 14. The amplifier 14 contains an operational mode shifter 141 connected with the processor 11, which can make the simulation of the electronic load more accurate by determining the level of the input signal S.
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In simulation, the power source 2 generates the input signal S to the voltage measurement unit 15. The voltage measurement unit 15 measures the voltage of the input signal S to generate a measurement Vo. The measurement Vo is then passed to the forward voltage processor 131. At the same time, the electronic load 1 receives the control command C for setting specifications of an LED device to be simulated.
The control unit 13 decodes the control command C and generates accordingly at least a set of the parameters P. The set of the parameters P further includes a forward voltage parameter P1 and an equivalent impedance parameter P2. The forward voltage parameter P1 is to set up the forward voltage of the simulation signal IO. The equivalent impedance parameter P2 is to set up the equivalent impedance of the simulation signal IO, which also equals to the resistance Rd in
It is always true that the input voltage equals to the output voltage of a circuit (i.e., Vo=VF+IO×Rd). In the case that the measurement Vo is less than the magnitude of the forward voltage source VF (also called voltage source), the amplifier 14 won't work. In the case that the measurement Vo is larger in magnitude than the voltage source VF, the forward voltage processor 131 begins calculating the voltage deviation between the measurement Vo and the voltage source VF. Theoretically, the voltage deviation equals to the current of the simulation signal IO multiplying the magnitude of the resistance Rd. The inverse of the resistance Rd is the slope of the characteristic curve in the aforesaid voltage-current plot.
The forward voltage processor 131 generates an adjustment command A according to the measurement Vo and the set of the parameters P. The amplifier 14 adjusts the output according to the adjustment command A.
For instance, the measurement Vo of the power source is 4.5V, and it is expected to have the electronic load simulate an LED with a 3V forward voltage and a 5 S2 equivalent impedance. According to a control command C, the processor 11 generates a corresponding forward voltage parameter P1 of 3 and a corresponding equivalent impedance parameter P2 of 50 after decoding the control command C.
In the present invention, the electronic load 1 can further include a built-in database. The database stores LED types, LED characteristics, connection conditions, etc. Information of a particular LED to be simulated can be loaded from the database so as to generate the adjustment command A according to the information.
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In the case that the LED with the characteristic curve LED_a is to be simulated, a control command C with parameters VF
The simulation upon an LED combination with plural LEDs, serially or parallel, can also be carried out in the electronic load of the present invention by utilizing equivalent forward voltage and impedance.
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Firstly, the control command for setting up the specification of the LED to be simulated is imported to the electronic load. (S101)
Secondly, the processor inside the electronic load generates at least one set of parameters by decoding the control command. (S102)
Thirdly, the parameter control unit inside the electronic load receives the set of the parameters. (S103)
Fourthly, the power source generates an input signal to the electronic load. (S104)
Fifthly, the voltage measurement unit generates a measurement by measuring the voltage of the input signal. (S105)
Sixthly, the control unit generates an adjustment command by calculating the set of the parameters and the measurement. (S106)
Finally, the amplifier outputs the simulation signal based on the adjustment command to trigger the power source outputting a power to the electronic load according to the simulation signal. (S107)
This electronic load is capable of adjusting the magnitude of the equivalent impedance to conform a real current simulation. Furthermore, this electronic load is also capable of setting up the initial impedance so as to avoid possible voltage surge in the simulation.
While the present invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be without departing from the spirit and scope of the present invention.
Number | Date | Country | Kind |
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098130654 | Sep 2009 | TW | national |