Texas Instruments Corporation

James Michael Walden

Satish Kumar Vemuri

Kyoung Min Lee

Isaac D Cohen

Yang Zhang

Brian Jude Linehan

Zhidong Liu

Pei-Hsin Liu

Disclosed examples include flyback converters, control circuits and methods to facilitate secondary side regulation of the output voltage. A primary side control circuit operates a primary side switch to independently initiate power transfer cycles to deliver power to a transformer secondary winding in a first mode. A secondary side control circuit operates a synchronous rectifier or secondary side switch to generate a predetermined cycle start request signal via a transformer auxiliary winding to assume secondary side regulation and to cause the primary side controller to initiate new power transfer cycles.

Flyback converter with secondary side regulation

In a transistor turnoff system, a transistor control circuit is configured to adjust a control voltage at a transistor control output responsive to a comparison signal at a control input. The control voltage has a slew rate. A comparator has a comparator output and first and second comparator inputs. The first comparator input is coupled to the transistor control output. The comparator is configured to: provide the comparison signal at the comparator output based on a reference voltage at the second comparator input; and deactivate the transistor control circuit by changing a state of the comparison signal responsive to the control voltage falling below the reference voltage. A slew-rate compensator is configured to increase the reference voltage by a compensation voltage that compensates for a time delay of the comparator or the transistor control circuit. The compensation voltage is proportional to the slew rate.

Slew-rate compensated transistor turnoff system

Gate driver bootstrap circuits and related methods are disclosed. An example gate driver stage includes a first terminal and a second terminal, the first terminal to be coupled to a capacitor, the capacitor and the second terminal to be coupled to a gate terminal of a power transistor, a gate driver coupled to the first terminal and the second terminal, and a bootstrap circuit coupled to the first terminal, the second terminal, and the gate driver, the bootstrap circuit including a control stage circuit having an output and a first transistor having a first gate terminal and a first current terminal, the first gate terminal coupled to the output, the first current terminal coupled to the first terminal.

Gate driver bootstrap circuits and related methods

One example includes a circuit that includes a transistor control circuit having an input and an output adapted to be coupled to the output of the transistor control circuit and can provide a slew-rate compensation voltage proportional to a slew-rate of a control voltage of the transistor. A reference voltage source can be coupled to the slew-rate compensator to provide a reference voltage at the output of the reference voltage source, the slew-rate compensator configured to add the slew-rate compensation voltage to the reference voltage to provide an adjusted reference voltage at the output of the slew rate compensator. A reference comparator having a first input, a second input and an output is coupled to the input of the transistor control circuit. The first input can be coupled to the control terminal of the transistor, and the second input can be coupled to the output of the slew-rate compensator.

A power converter circuit includes a power stage that includes a transformer and a switch. The switch can be controlled in response to a PWM signal to provide a primary current through a primary winding of the transformer to induce a secondary current in a secondary winding of the transformer to generate an output voltage. The power stage includes a switching node between the switch and the primary winding having a switching voltage. The circuit also includes a switching controller configured to generate the PWM signal in response to a ramp signal. The ramp signal can have an amplitude of a slope that is proportional to a decay rate of a magnetizing current of the transformer and generated in response to feedback from the power stage. The switch can be activated in response to the switching voltage having an amplitude of approximately zero volts based on the amplitude of the ramp signal.

Power converter with zero-voltage switching

Methods, systems, and apparatus to increase common-mode transient immunity in isolation devices is disclosed. An example apparatus includes a current mirror including an input terminal and an output terminal; a transistor including a gate terminal, a first current terminal, and a second current terminal, the gate terminal coupled to a reference voltage terminal, the first current terminal coupled to the input terminal of the current mirror, and the second current terminal coupled to an input node; a buffer including an input terminal and an output terminal, the input terminal of the buffer coupled to the output terminal of the current mirror; and a logic gate including an input terminal and an output terminal, the input terminal of the logic gate coupled to the output terminal of the buffer.

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Apex, NC, United States of America

James Michael Walden