Self-adjusting bootstrap recharge system in dual-switch flyback converters

A method for operating a converter comprising a bootstrap capacitor, a high-side switch, and a low-side switch, the bootstrap capacitor having a first terminal coupled to a floating ground node, the high-side switch having a source terminal coupled to the bootstrap capacitor through the floating ground node, the method comprising:

• generating a first control signal at a control terminal of the high-side switch;
• and
• generating a second control signal at a control terminal of the low-side switch,
• wherein a transitioning of the second control signal to turn OFF the low-side switch is delayed after a duration from a transitioning of the first control signal to turn OFF the high-side switch,
• wherein the delay is decreased in response to a voltage across the bootstrap capacitor being greater than a threshold voltage,
• wherein the delay is increased in response to the voltage across the bootstrap capacitor being less than the threshold voltage, and
• wherein the delay begins in response to a voltage at the floating ground node being less than zero.

A controller for operating a converter comprising a bootstrap capacitor, a high-side switch, and a low-side switch, the bootstrap capacitor having a first terminal coupled to a floating ground node, the high-side switch having a source terminal coupled to the bootstrap capacitor through the floating ground node, the controller configured to:

• provide a first control signal to a control terminal of the high-side switch, and
• provide a second control signal to a control terminal of the low-side switch,
• wherein a transitioning of the second control signal to turn OFF the low-side switch is delayed after a duration from a transitioning of the first control signal to turn OFF the high-side switch,
• wherein the delay is decreased in response to a voltage across the bootstrap capacitor being greater than a threshold voltage,
• wherein the delay is increased in response to the voltage across the bootstrap capacitor being less than the threshold voltage, and
• wherein the delay begins in response to a voltage at the floating ground node being less than zero.