Patent ID: 7420355
Filing Date: 2008-09-02
Classification: H02M

Abstract:
1. A DC-DC converter for powering a load connectable to an output node of the DC-DC converter with power supplied at a voltage supply node of the DC-DC converter, the DC-DC converter comprising: a control circuit for generating a pulse width modulated signal based on a voltage at said output node and for generating an over-voltage fault signal when said voltage at said output node exceeds a limit; a first switch connected to conduct during pulses of said pulse width modulated signal; a second switch connected to conduct during time intervals between pulses of said pulse width modulated signal, wherein said first switch is connected to an internal power node, wherein said internal power node is connectable to said voltage supply node, wherein said second switch is connected to a current return node, and wherein there is a common node between said first switch and said second switch; an output filter circuit connected to said common node and to said output node, wherein said control circuit is responsive to a feedback signal from said output node to control a width of said pulses of said pulse width modulated signal, whereby a voltage of said output node can be controlled; an input power switch connecting said internal power node to said voltage supply node; a charging circuit connecting said pulse width modulated signal to a conduction control terminal of said input power switch, said charging circuit comprising a resistor and a diode in series whereby said input power switch is caused to conduct when said pulse width modulated signal is turned on; and an over-voltage protection circuit connected to receive said over-voltage fault signal from said control circuit, said over-voltage protection circuit connected to said conduction control terminal of said input power switch to cause said input power switch not to conduct during an event causing an over-voltage fault signal.