Diode Characteristics Univerity of Massachusetts Dartmouth二极管的特性麻州大学达特茅斯.pptVIP

PN-Junction Diode Characteristics Graphical PN-Junction Diode V-I Characteristic Mathematical Approximation Ideal PN Junction Diode V-I Characteristic Diode Reverse Recovery Time Reverse Recovery CharacteristicsSoft Recovery Reverse Recovery CharacteristicsAbrupt Recovery Series-Connected Diodes Use 2 diodes in series to withstand higher reverse breakdown voltage. Both diodes conduct the same reverse saturation current, Is. Diode Characteristics Due to differences between devices, each diode has a different voltage across it. Would like to “Equalize” the voltages. Series-Connected Diodes with Voltage Sharing Resistors Series-Connected Diodes with Voltage Sharing Resistors Series-Connected Diodes with Voltage Sharing Resistors Is = Is1+IR1 = Is2+IR2 IR1 = VD1/R1 IR2 = VD2/R2 = VD1/R2 Is1+VD1/R1 = IS2+VD1/R2 Let R = R1 = R2 Is1 + VD1/R = Is2 +VD2/R VD1 + VD2 = Vs Example 2.3 Is1 = 30mA, Is2 = 35mA VD = 5kV (a) – R1=R2=R=100k?, find VD1 and VD2 (b) – Find R1 and R2 for VD1=VD2=VD/2 Example 2.3 (a) Example 2.3 (a) simulation Example 2.3 (b) Example 2.3 (b) simulation *ECE 442 Power Electronics Forward Bias --- External battery makes the Anode more positive than the Cathode --- Current flows in the direction of the arrow in the symbol. Reverse Bias --- External battery makes the Cathode more positive than the Anode --- A tiny current flows opposite to the arrow in the symbol. Reverse breakdown Forward Bias Region Reverse Bias Region Forward Bias – Short Circuit Reverse Bias – Open Circuit ta is the time to remove the charge stored in the depletion region of the junction tb is the time to remove the charge stored in the bulk semiconductor material Reverse recovery time = trr = ta+tb Peak Reverse Current = IRR = ta(di/dt) Reverse recovery time = trr = ta+tb Peak Reverse Current = IRR = ta(di/dt) *ECE 442 Power Electronics