Abstract: A driver circuit for one or more LEDs includes a power circuit having an output terminal, a capacitor coupled to the output terminal and a switch, and a control circuit coupled to the power circuit for controlling the power circuit. The control circuit is configured to operate the switch for coupling a resistance in series with the capacitor in response to detecting an open circuit condition at the output terminal. Additionally, or alternatively, the driver circuit may include a switched mode power supply, and the control circuit may be configured to switch operation of the switched mode power supply from a current control mode to a voltage control mode, and reduce a current setting for the current control mode, in response to detecting an open circuit condition at the output terminal.

Abstract: An assembly for processing green biomass material for pelletizing into a fuel pellet includes a heating assembly, a drying assembly and a cooling assembly. The heating assembly heats a thermal fluid to a temperature within the range of 200° F. to 550° F. The drying assembly includes a rotating dryer drum that has a plurality of thermal fluid tubes therein. Material that is dried in the dryer drum is conveyed to a rotating cooling drum that has a cooling tube extending along the interior thereof. A nozzle is mounted on the end of the cooling tube to discharge cooling fluid on the material therein, and a plurality of flights are mounted on the interior of the cooling drum and arranged to direct material from the inlet to the discharge outlet as the cooling drum is rotated.

Abstract: A method of controlling a multiphase power converter including a plurality of sub-converters coupled to provide power to a load is disclosed. Each sub-converter includes a power switch. The method includes selectively and consistently turning on the power switch of one or more of the sub-converters at substantially a same time as a reference signal representing a desired output of the power converter increases. The method further includes selectively and consistently turning off the power switch of one or more of the sub-converters at substantially a same time as the reference signal representing the desired output of the power converter decreases. Other methods, multiphase power converters and controllers for multiphase power converters are also disclosed.

Abstract: A material reduction machine includes a frame, a drum housing mounted to the frame, and a drum that is mounted for rotation within the drum housing. The drum includes a circumferential wall and a knife that is mounted on the drum. The machine includes a plurality of interchangeable belly bands, each of which is adapted to be removably attached to the frame so as to form a portion of the drum housing and to provide an inner surface that forms a belly band arc portion that is concentric with and of a larger diameter than the circumferential wall of the drum. A first interchangeable bellyband has a smooth inner surface, and a second interchangeable belly band has a plurality of flow interrupters spaced along its inner surface.

Abstract: A method of operating a switching power converter having at least one power switch controlled by a drive signal having a switching frequency is disclosed. The method includes monitoring an output power of the switching power converter, determining whether the output power has decreased below a threshold level and, in response to the output power decreasing below the threshold level, changing the switching frequency of the drive signal from a first switching frequency to a second switching frequency when an operating condition of the switching power converter is satisfied. Also disclosed are controllers and switching power converters (including PFC converters).

Abstract: According to one example embodiment, a bridgeless boost power factor correction (PFC) system includes a first input for connection to a first line of an alternating current (AC) source and a second input for connection to a second line of the AC source. The PFC system includes an output for delivering an output of the bridgeless boost PFC system, a first boost choke coupled to the first input and a second boost choke coupled to the second input. A common mode choke is coupled between the first and second input and the first and second boost choke. A first X capacitor is coupled between the first input and the output and a second X capacitor coupled between the second input and the output.

Abstract: A method of generating an output voltage from a variable input voltage with a power factor correction (PFC) system is disclosed. The PFC system includes a first power rail and a second power rail connected in parallel between an input for receiving the input voltage and an output for outputting the output voltage. The method includes operating one or both of the first power rail and the second power rail to generate the output based, at least in part, on whether the input voltage exceeds a threshold voltage. Power supplies and PFC systems suitable for performing the method are also disclosed.

Abstract: Methods of regulating an output voltage of a multi-output isolated power converter are disclosed. One method includes allowing the output voltage to vary unregulated when the output voltage is below a threshold value and preventing the output voltage from increasing when the output voltage reaches the threshold value. Additional methods and multi-output power supplies are also disclosed.

Abstract: A power supply includes an input, an output, a reverse current protection circuit, a synchronous rectifier and an output choke. The reverse current protection circuit is configured for detecting a flyback voltage indicative of reverse current, and for deactivating the synchronous rectifier in response to detecting the flyback voltage. The flyback voltage can be detected a variety of ways, including across the output choke, across a switch in the synchronous rectifier, across the secondary winding of a power transformer, etc.

Abstract: A method of controlling a power converter having at least one switching device for supplying an output voltage and a load current to a load is disclosed. The method includes sensing the output voltage and sensing the load current. The method further includes controlling a duty cycle of the switching device according to the sensed output voltage and a voltage control loop when a rate of change of the load current does not exceed a threshold level. The method also includes adjusting the duty cycle of the switching device set by the voltage control loop when the rate of change of the load current exceeds the threshold level.

Abstract: A guided boring machine includes a cutter head, a steering head and an internal casing with an auger therein for conveying material cut by the cutter head towards the rear end of the auger. The boring machine bores a tunnel from a launch pit to a target pit along a desired boring direction and simultaneously installing a selected one of a plurality of differently-sized product casings in the tunnel. When the internal casing is placed within a selected product casing with its internal casing longitudinal axis coincident with the longitudinal axis of the selected product casing, an annular space is formed with respect to the selected product casing. The guidance assembly includes a laser that is mounted behind the boring machine and oriented so as to direct its beam in a desired boring direction within the annular space. A target mount is mounted to the steering head inside surface. The target mount includes a roll correction slot which is parallel to the adjacent steering head inside surface.

Abstract: A control circuit for controlling a switching device having a first terminal, a second terminal, and a control terminal is disclosed. The control circuit includes a first diode for coupling to the first terminal of the switching device, a second diode for coupling to the second terminal of the switching device, a first transistor for coupling to the control terminal of the switching device, and a second transistor coupled to the second diode. The first transistor is coupled to the first diode. The control circuit is configured to allow current flow in only one direction between the first and second terminals of the switching device.

Abstract: A method of controlling an isolated switching power converter that includes a transformer with a primary side and a secondary side, at least one primary switch coupled to the primary side of the transformer and at least one synchronous rectifier coupled to the secondary side of the transformer is disclosed. The method includes turning on the synchronous rectifier a first fixed time after turning on the primary switch and turning off the synchronous rectifier a second fixed time after turning off the primary switch. Power converters for operation according to this method are also disclosed, including power converters without an output inductor.

Abstract: A cost effective integrated automotive solution for a charger transformer with minimized fringing flux and core grounding for reducing electromagnetic interference (EMI). The method provides an air gap filled with a mixture of an adhesive and ferrite powder that bonds the ferrite core sections together. In addition, the ground pin of the transformer is exposed through a groove in the pocket of the bobbin on which the core is mounted and an electrical contact is established between the exposed end of the ground pin and the core surface by means of a drop of epoxy.

Abstract: A method of controlling a dimming level of one or more light emitting diodes (“LEDs”) includes receiving a phase cut dimming signal having a pulse width and frequency, generating a PWM signal having a duty cycle and frequency corresponding to the pulse width and frequency, respectively, of the phase cut dimming signal, and controlling a power converter coupled to the one or more LEDs with the generated PWM signal so that the dimming level of the one or more LEDs is a function of the duty cycle of the generated PWM signal. Example circuits for practicing this method and alternative methods are also disclosed.

Abstract: A method of operating an LED driver including a power converter to generate an output current for powering an LED and to provide active power factor correction is disclosed. The power converter is coupled between an input to receive a rectified AC voltage and an output for providing the output current to the LED. The method includes operating the power converter at a substantially fixed frequency in an open loop mode based on a current through the inductive element and the rectified AC voltage. LED drivers operable in accordance with the disclosed method are disclosed.

Abstract: A switching power converter includes an input for receiving an input voltage, an output for providing an output voltage, a controller, and a power circuit coupled between the input and the output and including at least one switch. The controller is configured to determine a duty cycle for the switch to regulate the output voltage and control the switch with a PWM drive signal having an on-time and an off-time. The PWM drive signal has a constant frequency and a duty cycle equal to the determined duty cycle when the determined duty cycle is greater than or equal to a minimum duty cycle. The PWM drive signal has a variable frequency and a duty cycle equal to the minimum duty cycle when the determined duty cycle is less than the minimum duty cycle.

Abstract: A modular-based, zero-current-switched (ZCS), isolated full-bridge boost converter with multiple inputs is disclosed. Each converter module is used to match the connected input source and control the amount of power drawn from the source. The power from various sources are combined together and delivered to the load through a multiphase transformer. The input inductor of each boost-derived converter module keeps the input current constant and acts as a current source to drive the multiphase transformer through a phase-shifted-controlled full bridge converter. By connecting an auxiliary circuit across the full-bridge input in each module, the transformer leakage inductance and output capacitance of the switching devices are used to create resonant paths for facilitating zero-current-switching of all switching devices.

Abstract: A power conversion system for use with a photovoltaic (PV) power source may include a DC/DC converter for converting a first DC voltage into a second DC voltage, an isolation transformer, an inverter for converting DC power to AC power, and at least one controller for controlling the DC/DC converter and the inverter. The controller may be configured to operate the DC/DC converter as a buck converter or a boost converter based, at least in part, on whether the first DC voltage is less or greater than a reference voltage. Additionally, the controller may operate the converter according to a maximum power point tracking algorithm. Further, the controller may be configured to operate the inverter to control the DC voltage at the inverter's input as a function of the AC voltage at the inverter's output. Example embodiments of power systems, DC/DC converters, DC/AC inverters and related methods are also disclosed.

Abstract: A method and template are provided for modifying an asphalt dryer/mixer that includes an outer drum and an inner drum with a plurality of mixing paddles, the two drums forming an annular mixing chamber in which asphalt cement and aggregate materials are mixed. The template comprises a bracket marking portion that is adapted to locate one or more brackets on the inner drum and a paddle reference portion that is adapted to locate the bracket marking portion with respect to a mixing paddle. A mixing paddle to be referenced for locating a bracket is selected and the template is placed on the inner drum with the paddle reference portion referencing the selected mixing paddle. The template is used to mark the location of the bracket, the bracket is affixed to the outer surface of the inner drum at the bracket location marked; and an agitation strand is attached to the bracket.