Dummy load

Abstract: A switching power supply is modified to mitigate potentially adverse effects of near zero loads on power delivery. In one example, a processor-controlled dummy load is coupled to the power supply output in addition to an actual load. The dummy load is controlled so that at least some minimal load is presented to the power supply when the actual load is drawing low or near zero power. In another example, the feedback loop of the switching power supply is modified to mitigate the effects of a potential overvoltage condition in a bias supply from which the switch controller of the power supply draws power, which condition may occur at low or near zero load power. A lighting system may include a switching power supply thusly modified to provide power to a variable load that includes one or more LED-based lighting apparatus.

Abstract: An implantable medical device is provided with a removable dummy load across its connector output terminals to allow the device to be tested without removal from the sterile disposable package in which it is shipped and stored. The dummy load is confined with the device entirely within the sterile package to simulate the electrical impedance across the output terminals when the device is implanted in a patient and connected to an electrical lead for tissue stimulation. Testing is performed using a conventional external programmer normally provided for programming and monitoring output functions and parameters of the device. The programmer communicates by telemetry with the device confined within the package, to test selected functions and parameters. The dummy load has posts adapted to mate with the receptacles of the electrical connector of the device, and to be secured mechanically and electrically in the receptacles by set screws. The posts are dimensioned to provide a mechanical stop for the set screws when tightened down, and, when the set screws are backed off slightly from the posts to allow removal of the dummy load, to permit the proximal terminals of the replacing lead to be fully inserted into the receptacles without obstruction by the set screws.

Abstract: This paper proposes a primary-side control scheme for low-power light-emitting diode (LED) driver with Flyback topology. With average primary-side current signal and transformer auxiliary winding voltage signal, the output current can be derived and regulated precisely by the proposed control scheme without any isolated feedback circuit. Furthermore, the proposed primary-side control scheme can be implemented with power factor correction control to achieve high input power factor, which is usually required for LED drivers. Since the triode for alternating current (TRIAC) dimming is very popular in practical application, it is preferred that the LED driver can also be compatible with TRIAC dimming. With the proposed control scheme, the input characteristic of the LED driver is resistive like an incandescent bulb. No extra dummy load is needed to provide the TRIAC holding current. Both the output current signal and TRIAC dimming signal can be obtained at the primary side, the TRIAC dimming function can be easily implemented and linear dimming characteristic can be achieved. Detailed operation principles and design considerations of the proposed control scheme are presented in the paper. The experimental results from a 15-W prototype verify the theoretical analysis.

Abstract: A 170?GHz gyrotron has been developed at JAEA, which has achieved operation of 1?MW/800?s and up to 55% efficiency. This is the first demonstration of a gyrotron achieving and even exceeding the ITER operating requirements of 1?MW/500?s and 50% efficiency. In addition the gyrotron demonstrated operation for 1?h with an output power of 0.6?MW. The oscillation was stable with all cooling water temperatures and vacuum pressure reaching equilibrium conditions during the pulse length at either power level. The successful operation was aided by a very low level of stray radiation (~2% of the output power), which contributed to fast conditioning and stable operation. The output power from the gyrotron was coupled into an ITER sized corrugated waveguide ( = 63.5?mm) via a matching optics unit with a total of 0.97?MW transmitted to the dummy load after two miter bends and ~7?m of a waveguide without any trouble. These results give an encouraging outlook for the success of the ITER electron cyclotron heating and current drive system.