Abstract: Synchronous rectifier gate drive mechanisms are revealed which are universally applicable to zero voltage switching power converters which rely on an auxiliary inductor to drive the critical turn on transition of the main switch of the power converter. One of the gate drive mechanisms revealed can also be used to improve the ZVS load range of the converter and to increase the power capability of the converter. Voltage limiting circuits that clamp the gate voltage of a synchronous rectifier during the turn off transition of the synchronous rectifier, preventing inadvertent turn on of the synchronous rectifier, are revealed.

Abstract: Several novel zero voltage switching (ZVS) cells and a ZVS dc to dc transformer circuit are revealed. A U core transformer structure for use with the dc to dc transformer circuit is also revealed. An optimal gate drive circuit that achieves optimal switch timing for ZVS switches is revealed. The optimal gate drive circuit achieves optimal timing for the case in which there is sufficient energy available to drive a zero voltage transition and also for the case in which there is insufficient energy to drive a zero voltage transition providing turn on current to the switch at the minimum drain voltage of the switch. A magnetically coupled multi-phase converter cell structure is revealed which achieves reduced switch ripple current and fast transient response for multi-phase systems with three or more cells. A ZVS active reset switch drive scheme is revealed for providing zero voltage switching in bi-directional power flow converters for both directions of power flow using a single active reset circuit.

Abstract: Synchronous rectifier self drive mechanisms are revealed which are universally applicable to zero voltage switching power converters which rely on an auxiliary inductor to drive the critical turn on transition of the main switch of the power converter. The voltage wave form generated by the auxiliary inductor is well suited to synchronous rectifier self drive. Voltage limiting circuits that reduce the voltage swing of synchronous rectifier gates are also revealed. These voltage limiting circuits reduce the energy circulated into and out of the synchronous rectifier gates and protect the synchronous rectifier gate circuits from negative over voltage.

Abstract: Simple adaptive gate drive circuits, applicable to switches that turn on at zero voltage, such as mosfets or IGBTs, are revealed. The new gate drive circuits improve the timing for turn on of the switches, reduce gate drive losses, and limit gate voltage stress. In its simplest form the gate drive circuit requires only a single small mosfet and two diodes. The adaptive gate drive circuit provides optimal switch turn on timing for the case in which the drive energy available to drive the turn on transition is sufficient to drive the main switch to zero volts. The adaptive gate drive circuit also provides optimal switch turn on timing for the case in which the energy available to drive the transition is insufficient to drive the transition all the way to zero volts, turning the main switch on at the minimum main switch voltage thereby minimizing main switch switching losses.

Abstract: Five circuit synthesis methods, for forming new power conversion circuits with enhanced electromagnetic compatibility and improved AC performance from old circuits with AC performance and/or electromagnetic compatibility deficiencies, are revealed. The new synthesis methods achieve performance improvements without requiring the addition of magnetic cores. In all cases a simple toroidal magnetic core structure is not precluded. In all cases splitting or adding magnetic windings is required, and, in many cases, additional capacitors are required. Many new circuits formed by applying the synthesis methods are revealed. The results achieved by application of the synthesis methods include zero ripple current at all terminals without adding magnetic cores or requiring a complex magnetic circuit element, cancellation of common mode currents, improved control loop bandwidth, and faster transient response.

Abstract: Composite switches comprising multiple mosfets arranged in cascode which achieve higher efficiency and faster switching are revealed. The gate of a lower mosfet, a low voltage small die size mosfet, is driven with a conventional control circuit for modulation of the composite switch. The upper mosfet, a large die size high voltage mosfet, is controlled at its source terminal by the smaller mosfet while the gate of the upper mosfet is connected to a capacitor whose voltage remains fixed such that no net drive power is required by the gate circuit to drive the upper mosfet. The composite switch simultaneously achieves the low conduction losses of a large die device with the gate drive losses and fast switching of a small die device.

Abstract: A tapped inductor buck converter which achieves zero voltage switching and continuous input and output terminal currents is revealed. To achieve these results an additional switch, a small inductor, and a capacitor are required. The small inductor serves as a source of energy for driving the critical turn on transition of the main switch and the same small inductor also serves as a filter component for smoothing the input and output terminal currents. Simple adaptive gate drive circuits are revealed that improve the timing for turn on of zero voltage switches and reduce gate drive losses. A synchronous rectifier self drive mechanism is revealed which is universally applicable to zero voltage switching power converters with a single main switch which rely on an auxiliary inductor to drive the critical turn on transition of the single main switch. The wave form generated by the auxiliary inductor is ideally suited to synchronous rectifier self drive.

Abstract: Zero voltage switching cells using a small magnetic circuit element, a pair of switches, and a capacitor are revealed. The application of the zero voltage switching cells to any of a wide variety of hard switching power converter topologies yields equivalent power converters with zero voltage switching properties, without the requirement that the magnetizing current in the main magnetic energy storage element be reversed during each switching cycle. The new switching cells either provide integral line filtering or a means to accomplish zero voltage switching with no high side switch drive mechanism. In the subject invention the energy required to drive the critical zero voltage switching transition is provided by the small magnetic circuit element, either a single winding choke or a two winding coupled choke, that forms part of the zero voltage switching cell. The application of the zero voltage switching cells to buck, buck boost, Cuk, flyback, and forward converters is shown.

Abstract: PWM DC to DC converter circuits which accomplish ripple cancellation at one or more terminals are revealed. Four or more inductors are required in each case, however, in all cases multiple inductors can be combined into a single simple coupled inductor to accomplish the ripple cancellation. Some of the circuits revealed accomplish ripple cancellation at all terminals and some also provide zero voltage switching and galvanic load isolation. The non-isolated DC to DC converter networks revealed accomplish buck, boost, buck boost (flyback), buck complement, boost complement, or flyback complement conversion using a simple circuit requiring only two switches, one of which may be a simple diode rectifier, two or more capacitors, and four or more inductors, which may be co-located on a single common magnetic core. The isolated converters revealed provide continuous and discontinuous forward converter and continuous flyback converter transfer functions.

Abstract: A universal zero voltage transition switching cell using a small choke, a pair of switches, and a capacitor is revealed. The application of the universal zero voltage transition switching cell to any of a wide variety of hard switching pulse width modulated power converter topologies yields identical power converters with zero voltage switching properties, without the requirement that the magnetizing current in the main power choke be reversed during each switching cycle. In the subject invention the energy required to drive the critical zero voltage switching transition is provided by the small choke that forms part of the universal zero voltage transition switching cell. The application of the universal zero voltage transition switching cell to buck, boost, buck boost, Cuk, Wittenbreder, flyback, forward, and SEPIC converters is shown.

Abstract: Three terminal PWM DC to DC converter networks which accomplish both non-pulsating input and non-pulsating output currents using a single simple coupled inductor is revealed. The DC to DC converter networks accomplish buck, boost, buck boost (flyback), buck complement, boost complement, or flyback complement (SEPIC) conversion using a simple circuit requiring only two switches, one of which may be a simple diode rectifier, one or two capacitors, and three or four inductors, which may be co-located on a single common magnetic core. Also revealed are techniques to accomplish isolation, high order (quadrature) transfer functions, methodology for reducing current ripple to near zero levels at all terminals simultaneously, and methodology for generalizing the process of changing three terminal networks with pulsating terminal currents into three terminal networks with non-pulsating terminal currents.

Abstract: The power converter of this invention accomplishes zero voltage switching at both turn on and turn off transitions of all primary switches. A pair of coupled inductors serve as both energy storage devices and isolation mechanisms. The placement of a small inductor in series with the coupled inductors enables the invariance of primary current direction throughout the switching transition which provides for zero voltage switching for all switches for all transitions. The power converter behaves as a pair of interleaved coupled inductor buck converters with oppositely directed magnetizing currents. During a first half cycle, while one inductor is coupled to the output, the other uncoupled inductor behaves as a current source, setting the primary winding currents for both inductors equal to the magnetizing current of the uncoupled inductor. The inductor which is coupled to the output appears as an output filter capacitor or voltage source to the uncoupled inductor during the first half cycle.

Abstract: A DC to DC converter circuit which accomplishes both non-pulsating input and output currents using a single simple coupled inductor is revealed. The DC to DC converter accomplishes either buck or boost conversion using a simple circuit requiring only two switches, one of which may be a simple diode rectifier, a capacitor, and two inductors, which may be colocated on a single common magnetic core. These converters are, in some ways, similar to the Cuk converter, but they do not provide inverted outputs. Zero voltage switching versions of these converters are revealed. Also revealed are techniques and methodology for reducing both input and output current ripple to near zero levels. The buck version of the circuit accomplishes DC to DC conversion without inversion and with no right half plane zero in its control to output transfer function. The boost version is also non-inverting.

Abstract: A generalized active reset switching network using a small choke, a pair of switches, and a capacitor is revealed. The application of the generalized active reset switching network to any of a wide variety of hard switching power converter topologies yields equivalent power converters with zero voltage switching properties, without the requirement that the magnetizing current in the main power choke be reversed during each switching cycle. In the subject invention the energy required to drive the critical zero voltage switching transition is provided by the small choke that forms part of the generalized active reset switching network. The application of the generalized active reset switching network to buck, boost, buck boost, Cuk, and SEPIC converters is shown. A variation of the generalized active reset switching network which adds a single diode to clamp ringing associated with the parasitic capacitance of off switches is also revealed.

Abstract: A DC transformer circuit which accomplishes zero voltage switching for all switches for all transitions is revealed. The DC transformer is also self clamping so that clamping can be accomplished without compromising tight magnetic coupling and without using valuable window area for a clamp winding. The wave forms generated at the secondary windings are suitable for synchronous rectifier self drive. The combination of lossless switching, tight coupling, synchronous rectifier self drive, and maximum window utilization results in a DC transformer circuit which is suitable for high frequency, high efficiency operation. The DC transformer circuit uses two independent transformers with primary windings activated in anti-synchronization. The primary windings of the transformers are driven by a half bridge, a full bridge, or a push pull switching network.

Abstract: The power converter of this invention accomplishes zero voltage switching at both turn on and turn off transitions of four primary switches (220, 224, 228, and 232). A pair of coupled inductors (242 and 244) serve as both energy storage devices and isolation mechanisms. The stored energy in the coupled inductors (242 and 244) is used to drive the resonant transitions. The availability of stored energy in a coupled inductor for driving a switching transition is dependent on the timing of secondary switches (250 and 252) whereby the turn off of the secondary switches is delayed until the transition of the primary switches is complete. The power converter behaves as a pair of interleaved coupled inductor buck converters with oppositely directed magnetizing currents. During a first half cycle, while one inductor is coupled to the output, the other uncoupled inductor behaves as a current source, setting the primary winding currents for both inductors equal to the magnetizing current of the uncoupled inductor.

Abstract: The magnetic circuit element structure of this invention comprises a minimum four layer stacked layer sandwich construction in which layers of printed wiring board are alternately interleaved with layers of magnetic core material. Pins or wires form a part of the structure and are provided to electrically connect printed wiring board layers to form winding turns. Specifically, the pins or wires connect the copper foil patterns on layer 1 to the copper foil patterns on layer 3. Legs made of a magnetic core material also form a part of the structure and are provided to magnetically connect the core layers 2 and 4 in order to provide a closed path for magnetic flux. In the minimal structure a first layer consisting of a printed wiring board contains half turns of copper foil in one or more printed wiring board layers. The second layer is formed of ferrite or some other ferromagnetic core material.

Abstract: The power conversion system of this invention achieves precisely regulated input current and precisely regulated output voltage in a two step process whereby one power converter sub-system (141) provides input current regulation and a second power converter sub-system (158) provides output voltage regulation. The two converter sub-systems are arranged so that the second power converter sub-system (158) is powered by the first power converter sub-system (141) and the output of the second power converter sub-system (158) is placed in series with an output of the first power converter sub-system (141) to form the system output so that the load voltage is the sum of the two outputs placed in series. With this arrangement only a small fraction of the load power needs to be processed by the second power converter sub-system (158) which yields higher system efficiency and smaller system size, weight, and cost.