Abstract: Toroidal transformer and inductor configurations are described that allow for greater heat transfer away from internal device components. The inventive transformer allows for higher thermal and electrical efficiency, as well as for more efficient use of expensive components, such as copper wire. In one embodiment, a toroidal transformer provides access for cooling air by forming the primary winding from a single layer of thick wire and a secondary winding of few turns such that most of the primary winding is exposed to air flow. In another embodiment, a heat sink is positioned between the core and primary windings to conduct heat away from the transformer.

Abstract: An auger boring machine includes a track having an initial end and a terminal end, and the track is provided with a rack. The boring machine also includes a sled that is mounted on the track and adapted to be moved between the initial end and the terminal end of the track. The boring machine also includes a mechanism for rotating an auger on the sled and a drive system. The drive system includes a pinion which is mounted so as to engage with the rack on the track and a mechanism for rotating the pinion so as to drive the sled along the track.

Abstract: A soft switched zero voltage transition full bridge converter for reducing power loss at very light loads for zero voltage switching (ZVS) converters operating at high frequency. The converter has four switches in two switching legs, each having two switches connected in series between two input voltage terminals. Junction points of the legs are coupled to a primary winding of a transformer. The transformer has a secondary winding from which an output voltage of the converter is derived by rectifying and filtering. A pair of capacitive voltage dividers are connected between the input terminals, each formed by two small capacitors, each having a parallel-connected diode. The output voltage is regulated by phase shift control of the switches. The capacitors are selected small enough for storing only enough energy to enable ZVS in conjunction with two resonant inductors. The converter enables reduced component size of the inductors and energy storage capacitors.

Abstract: A switching power supply circuit has a power transformer having a core, a primary winding, and a secondary winding. A first switch has a control signal input and is connected to the primary winding of the power transformer. A synchronous rectifier has a control signal input and is connected to the secondary winding of the power transformer. A signal transformer has a primary winding and a secondary winding, and a first connection has a first end connected to the control signal input of the first switch and a second end connected to the primary winding of the signal transformer.

Abstract: A circuit controls a control signal of a free-wheeling switch and has a switch in series with the control signal signal. A timer has an output that controls the switch. The timer opens the switch for a predetermined time and closes the switch afterwards. In other embodiments, a free-wheeling switch circuit is provided for a synchronous switching power supply having an input and a pre-biased output. The switch circuit has an inductor, a first switch connected to the inductor and having a first control input, a first control signal source, a second switch having a second control input and being connected between the first control signal source and the first control input, and a control circuit having an output in communication with the second control input. The control circuit opens the second switch for a predetermined time and then closes the second switch.

Abstract: A circuit and corresponding method for reducing standby power and improving no-load to full-load regulation for ringing choke converters by maintaining a reduced duty cycle, with longer off time at no-load, while maintaining the output voltage swing closer to the full-load level. This reduced duty cycle prevents the output voltage from swinging high with respect to the full-load level, thereby providing good no-load and full-load output regulation in open feedback loop systems. The circuit and method provides very low no-load switching frequency and duty cycle by increasing the off time of the main switch through use of a turn off transistor driven by a zener diode, thereby maintaining conduction even with a very small control current and prolonging the off time of the main switch. The circuit and method achieves the benefits preferably using only less costly basic discrete converter components instead of more costly integrated circuits.

Abstract: A circuit for providing protection for power factor correction (PFC) boost converters from conditions such as input voltage surges that can otherwise cause failure. The circuit also prevents unnecessary down time of the boost converter after a power failure or on startup. The circuit detects the real time rectified input voltage and provides a real time comparison of the detected input voltage and the output voltage. The boost function is controlled as a function of the comparison. The circuit enables the boost converter to start and restart more quickly, even before the output voltage becomes stabilized, since boost is permitted as soon as the output voltage exceeds the real time sampled input voltage. By enabling boost during this period, the circuit eliminates the need to wait at least a few cycle times until the output voltage is higher than the peak of rectified input voltage.

Abstract: A soft-start circuit for a power converter including a switch controlled to cause the soft-start interval for the converter to be terminated when a predetermined condition is fulfilled. The predetermined condition is preferably the output voltage of the converter stabilizing at its normal operational level. The soft-start circuit detects when the predetermined condition is fulfilled and enables the converter to more rapidly recover after the initiation of a soft-start. In a preferred embodiment, the soft-start circuit includes a protection circuit for adjusting the soft-start voltage linearly as a function of the duration and magnitude of an overcurrent condition at the output so as to provide a scaled level of protection for the converter.

Abstract: An inductive element and corresponding method for making an inductive element for surface mounting on an adjacent structure for providing improved heat transfer characteristics. Specifically, a core and winding of the inductive element define coplanar surfaces that can then be mated to an adjacent structure, preferably a printed circuit board. Devices such as inductors or transformers including the inductive element have multiple, low thermal resistance conductive paths for removing heat from the core, and thereby enhance the heat transfer characteristics of the devices. The inductive element is particularly well suited for power electronics, such as for use as a power choke or as part of a power transformer.

Abstract: A circuit that utilizes most of the energy stored in the bulk capacitor of an AC to DC or DC to DC converter power supply by providing an intermediate converter between a first stage boost converter and a DC-DC converter. When the bulk voltage starts to fall during the hold-up time, the intermediate converter boosts the falling voltage to maintain the regulated DC input to the DC to DC converter while reducing the operating range and increasing the operating duty cycle, so as to increase efficiency, reduce peak current and voltage stresses. The circuit also reduces the size of the output filter components and reduces the size of the bulk capacitance by up to half.

Abstract: A circuit for controlling the operation of synchronous rectifiers. The circuit delays the turn-off of the synchronous rectifiers in accordance with the load current. The magnitude of the load current is examined to determine which of a plurality of delay elements is selected to delay turn-off of the synchronous rectifiers. Delay is accomplished by holding up for a predetermined time period one of a plurality of control signals utilized to determine when the synchronous rectifier should be turned-off.

Abstract: An undershoot eliminator circuit is disclosed that avoids the occurrence of a negative undershoot that typically happens when an isolated DC-DC converter with a secondary side synchronous driver that is turned off. The undershoot eliminator circuit functions to discharge an energy storage element in an auxiliary supply on said secondary side of said converter.

Abstract: The present invention provides a terminal pin for connecting a DC—DC power converter module or the like to a PCB. The pin has improved current carrying capabilities by having a diameter over most of its length that is larger than the ends that are connected to either the module or PCB. The larger diameter also provides for improved heat flow from the power converter module to the PCB. A smaller diameter portion near the PCB board provides for improved flow of solder between the pin and the PCB. A stand-off member is also provided to maintain the module and PCB at a predetermined stand-off distance.

Abstract: A power converter having a two stage boost circuit and a small boost converter. The main power flow for the power converter is via the two stage booster circuit having a single switch. The voltage spike of the switch is clamped by a diode and a capacitor. The energy at the capacitor is transferred to the power converter's output terminals by the small boost converter. The two stage boost converter topology enables the use of much lower voltage and Rdson MOSFET switches so as to reduce cost, switch conduction loss and turn on loss.

Abstract: A coupled-inductor current-doubler topology for a power converter has first and second rectifiers and first and second coupled inductors. Each coupled inductor has a main inductor inductively coupled with a secondary inductor. The secondary inductor of the first coupled inductor is coupled in series with one of the first and second rectifiers and the secondary inductor of the second coupled inductor coupled in series with the other one of the first and second rectifiers.

Abstract: A control circuit and corresponding method, particularly for power converters in a system having paralleled power converters, for rapidly and efficiently controlling a free-wheeling synchronous rectifier, so as to prevent any large negative current flow that might cause damage to components of the converter during a fault condition where the PWM signal turns off or has missing cycles. Preferably, clock signal and the gate drive output of a PWM controller are compared in order to recognize a failure condition and to rapidly provide control of the synchronous rectifier so as to prevent the large negative current flow. Control of the free-wheeling synchronous rectifier is provided in a way that is dependent on the gate drive output of the PWM controller and independent of timing, current sense signals, voltage sense signals, the current share system, and the operation of the forward synchronous rectifier of the power converter.

Abstract: A device for enlarging a bore includes an elongate body having a forward end, a rear end and an axis of rotation. The body of the device is adapted to be moved through the bore while being rotated about its axis. The device also includes a cutting blade which is attached to the body at or near its forward end, and a plurality of mixing wings. Each of the mixing wings has a unique shape, and each is attached to the body behind the cutting blade so that the axis of rotation of the body is within the plane spanned by the mixing wing.

Abstract: An asphalt production plant includes an asphalt binder storage tank, a mixer for mixing asphalt binder and aggregate materials, an asphalt binder pumping system for conveying asphalt binder to the mixer and an asphalt binder metering system for controlling the rate of flow of asphalt binder to the mixer. The asphalt production plant also includes a cold feed proportioning system having a plurality of cold feed bins for holding aggregate materials, with each such bin having a discharge opening through which aggregate materials may be discharged, a cold feed conveyor system that extends from beneath the discharge openings for the plurality of bins for conveying aggregate materials to the mixer and an apparatus and system for adjusting the relative proportions of aggregate materials from each of the cold feed bins that are conveyed to the mixer.

Abstract: A duty-cycle-shifted pulse-width modulation controlled half-bridge zero-voltage switching DC—DC converter has a primary side, a secondary side and a transformer coupling the primary side to the secondary side. The primary side has first and second primary switches coupled to a primary winding of the transformer and an auxiliary branch having one side coupled to a junction of the first and second primary switches and a second side coupled to common. The auxiliary branch includes a grounded auxiliary switch that is switched on when one of the first and second primary switches is on to trap leakage inductance energy of the transformer when that primary switch is turned off and thereafter switched off to release the trapped leakage inductance energy to provide a zero voltage switching condition for the other primary switch.

Abstract: A transformer having at least one primary winding and one secondary winding. The windings are disposed between walls of a first and second bobbin member. In preferred eombodiments, the creepage distance between the windings can be increased by providing a flange on one of the walls of one of the bobbin members.