Linear Technology Corporation

Analog Devices International Unlimited Company

William Hall Coley

Charles Edward Hawkes

Kurk David Mathews

Kurk David Matthews

A DC/DC converter may include a power stage circuit, a pulse generator circuit, a flux density monitor, and power control logic. The power stage circuit includes an input, an output, and a transformer with a core. The power stage circuit may be configured to operate in a power transfer phase during which power is transferred from the input to the output and a reset phase during which flux density in the core of the transformer is reduced. The pulse generator circuit may be configured to generate pulses that regulate the output of the power stage circuit. The flux density monitor circuit may be configured to generate flux density information indicative of the flux density of the core of the transformer during both the power transfer phase and the reset phase. The power stage control logic may be configured to regulate the output of the power stage circuit based on the pulses and to prevent the core of the transformer from saturating based on the flux density information.

DC/DC converter with magnetic flux density limits

Novel system and methodology are provided for controlling a DC/DC forward converter having a transformer with primary and secondary windings, a reset switch, and a first switch coupled to the primary winding of the transformer. The control system involves a PWM control circuit responsive to an output signal of the converter for producing a PWM signal to control switching of the reset switch, and the first switch. A period of the PWM signal includes an on-time interval for enabling transfer of power via the transformer when the first switch is on, and a reset time interval for enabling reset of the transformer when the reset switch is on. A maximum value of the on-time interval is pre-set to provide sufficient time for the reset. The reset switch is turned off when the PWM signal goes from a first level to a second level. A first delay period is set between time when the reset switch turns off and time when the first switch turns on. A first delay control circuit is provided for reducing the first delay time when the on-time interval approaches the maximum value. Further, the converter may include a second switch coupled to the secondary winding of the transformer. A second delay period shorter than the first delay period may be set between time when the reset switch turns off and time when the second switch turns on. A second delay control circuit may be provided for reducing the second delay period when the on-time interval approaches the maximum value.

Extending achievable duty cycle range in DC/DC forward converter with active clamp reset

A DC/DC converter and a method protect a MOSFET driven by the converter from overcurrent conditions. No extra pins are required to sense the current, which saves IC package area and cost.

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Cary, NC, United States of America

William Hall Coley