Abstract: A dense and efficient output stage for a DC/DC converter includes center tapped secondary windings of a transformer having an offset core with respect to a PCB, two pairs of synchronous rectifiers configured to define two pairs of paralleled symmetrical AC loops respective to the secondary windings, and at least two bus bars disposed within a forced cooling airstream to act as heat sinks for the synchronous rectifiers, while further providing a filtering impedance between the transformer windings and an output capacitance. A split capacitance is disposed in close proximity with the synchronous rectifiers to filter out ripple current, in one embodiment characterized by first and second capacitors each respectively coupled between opposing ends of the first and second bus bars, wherein the bus bars are arranged about at least three sides of the transformer core.

Abstract: An AC-DC power converter is provided with two pairs of self-driven synchronous rectifier switches in addition to, or in place of, diode bridge rectifiers for boosting efficiency and reducing cost. An AC sensing circuit is coupled to AC input terminals, and a DC level shifting circuit applies a DC offset to an AC input signal received via the sensing circuit. A comparator circuit determines positive and negative half waves of the AC input signal relative to the DC offset value. Gate drive signals are provided for driving a first set of parallel rectifier switches during a positive half cycle of the AC input signal, and for driving a second and opposing pair of parallel rectifier switches during a negative half cycle of the AC input signal. In an embodiment, high side gate drive signals may be electrically isolated from the active rectifier control circuitry.

Abstract: A resonant DC/DC power converter is provided with isolated primary and secondary circuits. The primary circuit includes at least four switches as first and second pairs in a bridge configuration, an isolation transformer having at least one primary and at least one secondary winding, and a resonant tank including a resonant capacitor and a split resonant inductor having two separate windings. In one embodiment, the split resonant inductor windings are substantially identical. Synchronous switching of diagonally opposed switch pairs in the bridge configuration thereby produces a center point voltage of the primary transformer winding is substantially free of stepwise voltage changes.

Abstract: A hybrid diode-less power converter topology of the present invention converts power from an AC power source to a variable load with high efficiency. The power converter includes a non-symmetrical arrangement of rectifying switches for rectifying an input AC voltage and shaping switches for shaping an input AC current. The shaping switches are operated in Continuous Conduction Mode (CCM) based on an input AC current. Operation of each of the rectifying switches and shaping switches are further controlled wherein a commutation time for the shaping switches is associated with a first voltage rise and fall time (e.g., less than 10 ns), and a commutation time for the rectifying switches is associated with a second voltage rise and fall time (e.g., at least 100 ns), wherein the first voltage rise and fall time is less than the second voltage rise and fall time by a factor of nine or more.

Abstract: A resonant power converter is provided with auxiliary circuit branches and control circuitry for switchably coupling the auxiliary branches to resonant circuit components during holdup times. Auxiliary branches are coupled in parallel with any one or more of a resonant inductor, a resonant capacitor, and a magnetizing inductive winding via respective switches. When a holdup time condition is detected in accordance with, for example, a drop in the mains line voltage, the switches are controlled to adjust the corresponding inductance or capacitance for the duration of the holdup time condition or otherwise for a predetermined duration. The power converter in normal operation is configured for high efficiency and in a holdup time operation is configured to produce sufficient holdup time.

Abstract: A power conversion system and method includes a DC-DC converter and an auxiliary circuit configured to ensure that a minimum input voltage is provided to the DC-DC converter during power interruption and for at least a predetermined hold-up time period. The auxiliary circuit includes an energy storage device, an auxiliary energy source for charging the energy storage device, and a clamping circuit to limit the energy stored by the energy storage device to a threshold voltage. A discharge time of the energy storage device from the threshold voltage to the minimum voltage thereby exceeds the predetermined hold-up time, but is only incrementally greater such that the size of the energy storage device is substantially reduced. The auxiliary energy source may typically be a current source, with the clamping circuit being control logic effective to disable the current source as a voltage across the storage device approaches the threshold.

Abstract: A transformer having a bobbinless winding assembly positioned on a base includes a primary winding having multiple radially-spiraling turns of a wire and a secondary winding including a substantially planar annular disk having a radial gap defined therein. A primary winding having first and second primary windings including multiple radially-spiraling turns of wire with free ends extending from outer turns and a method of forming the same is provided. A secondary winding having a planar annular disk with a radial gap defined therein and a method of forming the same is also provided.

Abstract: A switch-mode power converter includes a power isolation transformer and a drive transformer having their various windings collectively wound on a magnetic core having a center leg and outer legs. A primary winding and one or more secondary windings of the power transformer are wound on the center leg, and first and second windings of the drive transformer are wound on an outer leg. A primary control circuit controls one or more primary switches to supply the input voltage to the primary winding. A secondary control circuit controls secondary switches connected between the secondary windings and a load. Another control circuit controls operation the primary and secondary control circuits based at least in part on a feedback signal. The drive transformer windings are further configured to provide isolation between the primary control circuit and the synchronous rectifier control circuit.

Abstract: A multiphase power converter includes one or both of a phase control circuit and a valley switching locking circuit. The phase control circuit measures a phase difference between a first phase circuit and a second phase circuit and varies an on-time of a drive switch of the second phase circuit to produce and maintain a predetermined phase difference between the first phase circuit and the second phase circuit. When the multiphase power converter is operating in a discontinuous mode of operation, the valley switching locking circuit counts the number of zero crossings of an input current of the first phase circuit and blocks a second zero crossing detection signal from a waveform generator (i.e., PWM driver) associated with the second phase circuit until an input current of the second phase circuit has as many zero crossings as that of the first phase circuit input current.

Abstract: System and methods are provided for reducing vibration in server or data storage units. An anti-vibration system according to the present invention includes one or more disk drives and one or more fans in a defined area, and a controller which is configured to control operation of each of the one or more fans. A nominal speed setting and a speed range are determined for the one or more fans, either commonly or independently with respect to each, and the fans are caused to be driven in accordance with the determined speed setting and speed range. As a result the occasions in which individual fan speeds are coincident with fixed frequency sensitivities for each disk drive are substantially minimized.