A constant frequency switching power supply regulator with an input voltage of 165 volts DC, and a switching frequency of 20 kHz, has an "ON" time of 27 microseconds when supplying 1 ampere to its load. What is the output voltage across the load?
ā¢ Duty cycle in a constant-frequency switching regulator (relationship between ON time, period, and output voltage) ā¢ How to find the switching period from a known switching frequency (20 kHz) ā¢ The basic buck converter ratio: Vout is proportional to Vin times duty cycle (for an ideal regulator)
ā¢ First, convert 20 kHz into the switching period in microseconds. How long is one full cycle? ā¢ Given the ON time is 27 microseconds, what fraction of the total period is the switch ON (the duty cycle)? ā¢ If the input is 165 V DC and the regulator is ideal, how would you express Vout in terms of Vin and the duty cycle?
ā¢ Be sure to convert frequency to period correctly: ( T = 1/f ) and keep units consistent (seconds vs microseconds). ā¢ Check that your duty cycle is a number between 0 and 1 (or 0% to 100%). ā¢ After computing Vout, compare your numeric result carefully with the closest matching choice, watching for any rounding or placement of the decimal point.
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