Diodes

Electronic Circuits Laboratory EE462G Lab #4 DC Power Supply Circuits Using Diodes

Instrumentation ,[object Object],[object Object],[object Object]

Power Supplies ,[object Object],[object Object],[object Object],[object Object]

Rectification ,[object Object],Time -10.000 0.0 +10.000 0.0 +20.000m +40.000m +60.000m +80.000m +100.000m V s V out

Rectification ,[object Object],[object Object],[object Object],Time -10. 0.0 +10. 0.0 +40.000m +80.000m V s V out

Smoothing ,[object Object],V s + V out _ Why doesn’t the capacitor discharge as fast as it charges up?

Smoothing ,[object Object],[object Object],[object Object],[object Object],[object Object],What scope measure functions can be used to obtain an estimate of r ? What would the average or mean of this signal be, if AC coupling was used?

Smoothing ,[object Object],V s + V out _ R L C For diode-on state assume the time constant is much smaller than period T, so capacitor fully charges on pulse peaks (small cap-resistance product) and for diode-off state assume assume time constant is larger than period (large cap-resistance product) so capacitor discharges more slowly.

Smoothing For discharge cycle (diode off), the charge removed from the capacitor is: where T is the period of wave form and I L is load current Charge is also related to the voltage change and capacitor value: From the above, the following relationships can be derived: Show for full-wave rectification: V s + V out _ R L C V m

Regulation: ,[object Object],[object Object],[object Object],[object Object],Zener diode Forward Bias Reverse Bias Ideal approximation: Short Circuit Ideal approximation: Open Circuit Knee V D I D V Z

Regulation ,[object Object],Assuming an Ideal Zener diode (zero reverse bias current, and vertical breakdown region), what is the max power delivered to a load with output voltage V z ? Show that the load resistance at this point is (VzRreg)/(Vin-Vz). What happens when load resistance is less than this value? + Vz _

Regulation ,[object Object],is the average output no-load voltage (open circuit) is the average output full-load voltage (smallest rated resistive load) Percent regulation is obtained by multiplying Regulation by 100. What scope measurement functions would be helpful in assessing the regulation of the circuit? What coupling should be used in measuring the regulators output?

Power Supply with All Stages Half-wave example: Full-wave example:

SPICE ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Matlab ,[object Object],[object Object],[object Object],[object Object]

Final Notes ,[object Object],[object Object],[object Object],[object Object]

Diodes

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