Abstract: An isolated DC/DC converter includes a primary stage, a transformer circuit, a secondary stage, an active clamp, a first current sense node, and a second current sense node. The primary stage includes a primary switching inverter configured to invert the source DC voltage into a high-frequency alternating current (AC) voltage. The transformer circuit adjusts an AC voltage level of the high-frequency AC voltage and outputs an adjusted AC voltage. The secondary stage includes a secondary switching converter to convert the adjusted AC voltage into a secondary voltage, and the active clamp is configured to clamp the secondary voltage to provide an output DC voltage. The first current sense node is included in the primary stage conducts a source current having a first current level, and the second current sense node is included in the secondary stage and conducts a clamp current having a second current level.

Abstract: An isolated DC/DC converter includes a primary stage, a transformer circuit, a secondary stage, an active clamp, a first current sense node, and a second current sense node. The primary stage includes a primary switching inverter configured to invert the source DC voltage into a high-frequency alternating current (AC) voltage. The transformer circuit adjusts an AC voltage level of the high-frequency AC voltage and outputs an adjusted AC voltage. The secondary stage includes a secondary switching converter to convert the adjusted AC voltage into a secondary voltage, and the active clamp is configured to clamp the secondary voltage to provide an output DC voltage. The first current sense node is included in the primary stage conducts a source current having a first current level, and the second current sense node is included in the secondary stage and conducts a clamp current having a second current level.

Abstract: A topology for double-ended dual magnetic DC-DC SPC (“Voltage Doubler”) for all else being equal provides twice the output voltage as the conventional topology. The Voltage Doubler differs in that the secondary configuration is stacked in series as compared to the conventional topology in which the secondary configuration of the dual magnetics are in parallel. The output current is AC coupled rather than DC coupled to the load thereby doubling the output voltage. Because of the AC coupling, the Voltage Doubler is configured to automatically maintain balance of the secondary capacitors. During reset of the magnetics, the primary windings are shorted and both synchronous rectifier switches are closed. Due to transformer action, the output capacitors are connected to the output such that charge equalization forces the voltage on each capacitor to be equal.

Abstract: A topology for double-ended dual magnetic DC-DC SPC (“Voltage Doubler”) for all else being equal provides twice the output voltage as the conventional topology. The Voltage Doubler differs in that the secondary configuration is stacked in series as compared to the conventional topology in which the secondary configuration of the dual magnetics are in parallel. The output current is AC coupled rather than DC coupled to the load thereby doubling the output voltage. Because of the AC coupling, the Voltage Doubler is configured to automatically maintain balance of the secondary capacitors. During reset of the magnetics, the primary windings are shorted and both synchronous rectifier switches are closed. Due to transformer action, the output capacitors are connected to the output such that charge equalization forces the voltage on each capacitor to be equal.

Abstract: A multi slope output impedance controller is configured to vary the effective impedance Zeff_n of a power converter to reduce a current imbalance between power supplies in a masterless configuration of N parallel-connected power supplies while maintaining load regulation during start-up and sready-state operation. Generally speaking, the controller commands a high value of Zeff_n when Iout_n is low to facilitate current sharing and reduce current imbalance Ib between the power supplies and commands a low value of Zeff_n when Iout_n is high to improve load regulation.

Abstract: A dual-path active damper reduces power losses while damping ringing waveforms in resonant circuits. One path clamps the peak value of a node voltage at less than a rated voltage of a protected device while allowing the node voltage to ring and decay naturally. Another path waits for some delay after the peak value is clamped until closing an active switch to draw a reset current through an RC snubber to actively dampen the ringing of the node voltage. The delay and on-time of the active switch are set to reduce or even minimize power losses for damping the ringing waveform within a specified period.

Abstract: The present invention provides a prestart control circuit that measures a reflected voltage on the primary side of a switching power converter. The prestart control circuit pulses the synchronous rectifier switch OPEN and CLOSED, which allows a measurement of the reflected voltage on the primary side of the switching power converter. The reflected voltage is proportionate to the output voltage of the switching power converter. The prestart control circuit uses the reflected voltage to establish the initial duty cycle of the switching power converter. The switching power converter may be any converter that includes a synchronous rectifier, such as a flyback converter or a forward converter, in a single-ended, double-ended and/or multi-phased configuration.

Abstract: The present invention provides a prestart control circuit that measures a reflected voltage on the primary side of a switching power converter. The prestart control circuit pulses the synchronous rectifier switch OPEN and CLOSED, which allows a measurement of the reflected voltage on the primary side of the switching power converter. The reflected voltage is proportionate to the output voltage of the switching power converter. The prestart control circuit uses the reflected voltage to establish the initial duty cycle of the switching power converter. The switching power converter may be any converter that includes a synchronous rectifier, such as a flyback converter or a forward converter, in a single-ended, double-ended and/or multi-phased configuration.

Abstract: A pre-bias control circuit for a switching power converter detects the slope of the output voltage over time and outputs an OPEN command when the slope detected is more NEGATIVE than a pre-defined threshold and a pre-charge current that flows back through the switching power converter has reached a maximum value. In response, the synchronous rectifier switch OPENs overriding the typical control waveform to control the energy from the output voltage from flowing back through the switching power converter. The switching power converter may be any converter that includes a synchronous rectifier, such as a flyback converter, a forward converter, a buck converter, in a single-ended, double-ended and/or multi-phased configuration.

Abstract: The present invention is directed generally to a power supply. According to various embodiments, the power supply includes at least one DC/DC converter. The converter includes a primary switch controlled by a pulse width modulated control signal such that the primary switch is on for a D time period of each switching cycle of the converter and is off for a 1-D time period of each switching cycle. Also, the power supply includes a current sensing element connected in series with the primary switch. In addition, the power supply includes a current limit circuit connected to the current sensing element. The current limit circuit includes a functional circuit having a first input responsive to a first signal whose voltage is proportional to the output current of the converter during the D time period of the switching cycle of the converter.

Abstract: The present invention is directed generally to a power supply. According to various embodiments, the power supply includes at least one DC/DC converter. The converter includes a primary switch controlled by a pulse width modulated control signal such that the primary switch is on for a D time period of each switching cycle of the converter and is off for a 1-D time period of each switching cycle. Also, the power supply includes a current sensing element connected in series with the primary switch. In addition, the power supply includes a current limit circuit connected to the current sensing element. The current limit circuit includes a functional circuit having a first input responsive to a first signal whose voltage is proportional to the output current of the converter during the D time period of the switching cycle of the converter.

Abstract: A synchronous rectifier control circuit for controlling a synchronous rectifier of a power converter is disclosed. According to one embodiment, the control circuit includes a differentiator circuit responsive to the output voltage of the power converter. The control circuit also includes a summing circuit responsive to an output of the differentiator circuit and a step function signal. The control circuit further includes an integrator circuit responsive to an output of the summing circuit. In addition, the control circuit includes a gate drive circuit responsive to an output of the integrator circuit and a switching signal that controls a primary switch of the converter. The gate drive circuit also includes an output terminal for coupling to a control terminal of the synchronous rectifier.

Abstract: A drive circuit for a synchronous rectifier of a switch mode power converter is disclosed. The switch mode power converter may include a main power transformer and a primary switch for cyclically coupling the main power transformer to an input source. The drive circuit may comprise a turn-on switch, a turn-off switch, a charge pump and a pulse transformer. The charge pump may be coupled to a secondary winding of the main power transformer. The turn-on switch is for turning on the synchronous rectifier and may be coupled to the charge pump. The pulse transformer may include primary and secondary windings, wherein the primary winding is responsive to a control signal supplied to the primary switch. The turn-off switch is for turning off the synchronous rectifier and may include a control terminal coupled to the secondary winding of the pulse transformer.

Abstract: A DC-DC power supply with at least two paralleled converters and a current share method for the power supply are presented. According to one embodiment, the power supply includes first and second current mode controlled power converters connected in parallel for powering a load. Each of the paralleled power converters may include a voltage error amplifier, and the output terminals of the respective voltage error amplifiers are connected together. The power supply further includes a slow loop current share control circuit that is responsive to a sensed current in each of the power converters and, based on the sensed currents, forces the power converters to equally contribute to the load current.

Abstract: A DC-DC power converter is presented. According to one embodiment, the converter includes first and second transformers, and a double-ended input circuit, including first and second primary switches, for generating an alternating voltage across the primary windings of the first and second transformers. The converter also includes a control circuit (such as, for example, a PWM control circuit) for controlling the primary switches such that the primary switches are simultaneously OFF for a first time period during a switching cycle of the converter. In addition, the converter includes first and second synchronous rectifiers. The first synchronous rectifier is coupled to the secondary winding of the first transformer and the second synchronous rectifier is coupled to the secondary winding of the second transformer.

Abstract: A synchronous rectifier control circuit for controlling a synchronous rectifier of a power converter is disclosed. According to one embodiment, the control circuit includes a differentiator circuit responsive to the output voltage of the power converter. The control circuit also includes a summing circuit responsive to an output of the differentiator circuit and a step function signal. The control circuit further includes an integrator circuit responsive to an output of the summing circuit. In addition, the control circuit includes a gate drive circuit responsive to an output of the integrator circuit and a switching signal that controls a primary switch of the converter. The gate drive circuit also includes an output terminal for coupling to a control terminal of the synchronous rectifier.

Abstract: A DC-DC power supply with at least two paralleled converters and a current share method for the power supply are presented. According to one embodiment, the power supply includes first and second current mode controlled power converters connected in parallel for powering a load. Each of the paralleled power converters may include a voltage error amplifier, and the output terminals of the respective voltage error amplifiers are connected together. The power supply further includes a slow loop current share control circuit that is responsive to a sensed current in each of the power converters and, based on the sensed currents, forces the power converters to equally contribute to the load current.

Abstract: A DC-DC power converter is presented. According to one embodiment, the converter includes first and second transformers, and a double-ended input circuit, including first and second primary switches, for generating an alternating voltage across the primary windings of the first and second transformers. The converter also includes a control circuit (such as, for example, a PWM control circuit) for controlling the primary switches such that the primary switches are simultaneously OFF for a first time period during a switching cycle of the converter. In addition, the converter includes first and second synchronous rectifiers. The first synchronous rectifier is coupled to the secondary winding of the first transformer and the second synchronous rectifier is coupled to the secondary winding of the second transformer.

Abstract: A drive circuit for a synchronous rectifier of a switch mode power converter is disclosed. The switch mode power converter may include a main power transformer and a primary switch for cyclically coupling the main power transformer to an input source. The drive circuit may comprise a turn-on switch, a turn-off switch, a charge pump and a pulse transformer. The charge pump may be coupled to a secondary winding of the main power transformer. The turn-on switch is for turning on the synchronous rectifier and may be coupled to the charge pump. The pulse transformer may include primary and secondary windings, wherein the primary winding is responsive to a control signal supplied to the primary switch. The turn-off switch is for turning off the synchronous rectifier and may include a control terminal coupled to the secondary winding of the pulse transformer.

Abstract: A method for assembling a multi-deck power supply device including control and power components. The method comprises providing a first circuit board having a first and a second side. Two prefabricated pin holders are positioned on the first side of the first circuit board. Each pin holder includes two threaded inserts, a set of first pins and a set of second pins. The first pins are floating for self-alignment during soldering. After the first pins are soldered on the first side of the first circuit board, a second circuit board is aligned above the first circuit board, and the first and second pins are soldered to the second circuit board. The first pins may include pre-assembled oscillation dampers, such as magnetic material beads.