| 摘要 |
The present invention relates to a DC/DC converter configured to provide a regulated output voltage and a limited output current to a load, the converter comprising:
an inductor arranged to conduct a current to the output of the converter;
a switch responsive to a pulse width modulation signal and configured to control the current conducted to the output through the inductor as a function of the ON-time when the switch is closed during each cycle of the pulse width modulation signal;
a feedback control responsive to the inductor current and output voltage and configured to:
(a) provide the pulse width modulation signal to control the operation of the switch so that the inductor current has a peak current value for each cycle of the pulse width modulation signal at the end of each ON-time of the switch during each cycle and a ripple about an average value; and
(b) generate a compensating ramp signal for adjusting the duty cycle of the pulse width modulation signal so as to stabilize the feedback loop of the feedback control; and
wherein the feedback control includes a clamp for providing a limited voltage as a function of the desired peak current limit during current limit conditions, and a modulator for modulating the clamp voltage as a function of ripple of the inductor current for each cycle of the pulse width modulated signal so as to reduce or cancel the effect of the inductor ripple current on the average output current during current limit conditions;
a bias signal control configured to apply a variable DC bias signal to the compensation ramp signal so that the compensation ramp signal is biased to an instantaneous value of zero at the end of each ON-time for each cycle so that the peak current limit is independent of the duty cycle of the pulse width modulation signal during current limit conditions; and
a frequency foldback control for adjusting the frequency of the pulse width modulation signal during current limit conditions as a function of the input voltage and the output voltage of the converter. |
