Bootstrap startup and assist circuit
A bootstrap assist circuit and a startup circuit comprising a voltage controlled switch and a startup ramp voltage generator connected to the voltage controlled switch that will control a high side switch, a dimming interface or an enable/disable input function. Said system is used to provide a bootstrap technique to continuously switch a floating high side switch (MOSFET) by continuously charging a capacitor and then “level shifting” said capacitor voltage across the gate and source of the said high side switch to turn the switch on.
1. A method of bootstrap startup comprising:
receiving an input signal to begin bootstrapping;
initiating a startup voltage ramp;
initiating an artificial ramp current sense;
determining if a voltage controlled switch is reverse-biased; and
terminating the artificial ramp current sense if the voltage controlled switch is reverse-biased.
2. The method of claim 1 wherein if the voltage controlled switch is not reverse-biased, repeating initiating the artificial ramp current sense and determining if the voltage controlled switch is reverse-biased until it is determined that the voltage controlled switch is reverse-biased.
3. The method of claim 1 wherein initiating a startup voltage ramp comprises:
transmitting a current through an RC time constant.
4. The method of claim 1 wherein initiating the artificial ramp current sense comprises:
turning on a gate drive signal from a power factor corrected (PFC) transition mode (TM) control.
5. The method of claim 1 wherein initiating the artificial ramp current sense comprises:
detecting a voltage at a current sense pin within a power factor corrected (PFC) transition mode (TM) control.
6. The method of claim 1 wherein initiating the artificial ramp current sense comprises:
detecting a signal at a zero current detector within a power factor corrected (PFC) transition mode (TM) control.
7. The method of claim 1 wherein initiating an artificial ramp current sense comprises:
coupling a gate drive signal of a power factor corrected (PFC) transition mode (TM) control with a current sense of the PFC TM control.