DC/DC converter having a bootstrapped high side driver
First Claim
Patent Images
1. A step-down converter for converting an input voltage to a lower output voltage, said converter comprising:
- a pair of NMOS switches coupled in series, a first one of said switches being coupled to said input voltage and a second one of said switches being coupled to ground;
an output filter coupled to said pair of switches, said output filter providing an output terminal at which said output voltage is provided;
a bootstrap capacitor charged by said input voltage through a path including said second switch and having a bootstrap voltage thereacross; and
a control circuit receiving a signal indicative of said output voltage and providing gate drive signals to each of said pair of switches to control the duty cycles of said switches so as to maintain said output voltage substantially constant, said control circuit including a sensor for sensing said bootstrap voltage and increasing the duty cycle of said second switch in response to said bootstrap voltage being below a first predetermined level and said first switch being closed.
1 Assignment
0 Petitions
Accused Products
Abstract
A synchronous step-down DC to DC converter includes a bootstrap capacitor monitored by a controller for maintaining a desired bootstrap voltage to drive a high side NMOS switch. The controller temporarily increases the duty cycle of the low side NMOS switch when the bootstrap voltage decreases below a predetermined level to maintain a minimum level of charge on the bootstrap capacitor.
-
Citations
14 Claims
-
1. A step-down converter for converting an input voltage to a lower output voltage, said converter comprising:
-
a pair of NMOS switches coupled in series, a first one of said switches being coupled to said input voltage and a second one of said switches being coupled to ground; an output filter coupled to said pair of switches, said output filter providing an output terminal at which said output voltage is provided; a bootstrap capacitor charged by said input voltage through a path including said second switch and having a bootstrap voltage thereacross; and a control circuit receiving a signal indicative of said output voltage and providing gate drive signals to each of said pair of switches to control the duty cycles of said switches so as to maintain said output voltage substantially constant, said control circuit including a sensor for sensing said bootstrap voltage and increasing the duty cycle of said second switch in response to said bootstrap voltage being below a first predetermined level and said first switch being closed. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
-
8. A step-down converter for converting an input voltage to a lower output voltage, said converter comprising:
-
a pair of NMOS switches coupled in series, a first one of said pair of switches having a drain terminal coupled to said input voltage, a gate terminal, and a source terminal and a second one of said pair of switches having a source terminal coupled to ground, a drain terminal coupled to the source terminal of the said first switch, and a gate terminal, said pair of switches having complementary duty cycles; an inductor having a first terminal coupled to the source terminal of the first switch and the drain terminal of said second switch and a second terminal providing an output terminal of the converter at which said output voltage is provided; a capacitor having a first terminal coupled to said output terminal of said converter and a second terminal coupled to ground; a gate drive circuit for providing a gate drive signal to each of said pair of switches to control said duty cycles of said pair of switches; a bootstrap capacitor charged by a regulated voltage and coupled to said source terminal of said first switch, said bootstrap capacitor having a bootstrap voltage thereacross, said bootstrap voltage being greater than said input voltage and being provided to said gate drive circuit enabling said gate drive circuit to provide a gate drive signal to said first switch having a voltage greater than said input voltage; a PWM circuit coupled between said output terminal and said gate drive circuit, said PWM circuit providing a PWM command signal to said gate drive circuit to control said duty cycles of said pair of switches; and a bootstrap controller for monitoring said bootstrap voltage, said controller providing a control signal to said PWM circuit for adjusting said PWM command signal so as to increase the duty cycle of said second switch in response to said bootstrap voltage being below a predetermined level and said first switch being closed. - View Dependent Claims (9, 10, 11)
-
-
12. A method for driving a high side switch of a synchronous Buck converter comprising said high side switch coupled to an input voltage and a low side switch coupled between said high side switch and ground, said high side switch and said low side switch being NMOS devices, comprising the steps of:
-
coupling a bootstrap capacitor between a regulated voltage and a source terminal of said high side switch, said source terminal being further coupled to a drain terminal of said low side switch; charging said bootstrap capacitor through said low side switch when said low side switch is closed to provide a bootstrap voltage across said bootstrap capacitor; driving said high side switch with a gate drive signal having a voltage level corresponding to said bootstrap voltage; sensing said bootstrap voltage; and increasing the duty cycle of said low side switch in response to said bootstrap voltage being below a predetermined level and said high side switch being closed. - View Dependent Claims (13, 14)
-
Specification