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| electrical_engineering_and_electronics_2:block12 [2026/06/02 03:27] – mexleadmin | electrical_engineering_and_electronics_2:block12 [2026/06/10 03:06] (current) – mexleadmin | ||
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| Line 86: | Line 86: | ||
| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| - | U_{\rm | + | U_{\rm |
| = | = | ||
| U_R+U_{\rm D}. | U_R+U_{\rm D}. | ||
| Line 106: | Line 106: | ||
| I_{\rm D} | I_{\rm D} | ||
| \approx | \approx | ||
| - | \frac{U_{\rm | + | \frac{U_{\rm |
| \end{align*} | \end{align*} | ||
| \] | \] | ||
| Line 120: | Line 120: | ||
| The required forward voltage depends on the semiconductor material and therefore on the color. | The required forward voltage depends on the semiconductor material and therefore on the color. | ||
| - | For a supply voltage \(U_{\rm | + | For a supply voltage \(U_{\rm |
| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| \boxed{ | \boxed{ | ||
| - | R_{\rm V} = \frac{U_{\rm | + | R_{\rm V} = \frac{U_{\rm |
| } | } | ||
| \end{align*} | \end{align*} | ||
| Line 139: | Line 139: | ||
| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| - | P_R = (U_{\rm | + | P_R = (U_{\rm |
| \end{align*} | \end{align*} | ||
| \] | \] | ||
| Line 240: | Line 240: | ||
| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| - | {\color{blue }{I_{\rm V}}} &= \frac{U_{\rm | + | {\color{blue }{I_{\rm V}}} &= \frac{U_{\rm |
| \\ | \\ | ||
| {\color{green}{I_{\rm L}}} &= \frac{U_{\rm Z}}{R_{\rm L}} && | {\color{green}{I_{\rm L}}} &= \frac{U_{\rm Z}}{R_{\rm L}} && | ||
| Line 539: | Line 539: | ||
| ===== Exercises ===== | ===== Exercises ===== | ||
| - | <panel type=" | + | # |
| + | # | ||
| - | The following simulation includes multiple diodes. | + | The following simulation includes multiple diodes |
| - | Which lambs will light up, when the switch is closed? | + | A lamp lights brightly |
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{\rm lamp}\geq | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | drops across it. | ||
| + | |||
| + | Close the switch in the simulation. | ||
| + | |||
| + | * Which lamps light up brightly? | ||
| + | * Which lamps remain dark? | ||
| + | * Explain the result using the idea of diode bypass paths. | ||
| {{url> | {{url> | ||
| - | </ | ||
| - | <panel type=" | + | 1. Determine which lamps light up brightly. |
| - | The following simulation includes multiple diodes. Assume a simple diode model (the forward voltage drop is $V_F=0.6~\rm V$ and constant). The source voltage shall be $U0 = 4~\rm V$. | + | <WRAP group> |
| + | <WRAP half column rightalign> | ||
| + | # | ||
| + | <WRAP leftalign> | ||
| + | Number the lamps from left to right: | ||
| - | Calculate the currents through | + | \[ |
| + | \begin{align*} | ||
| + | L_1, | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | After closing the switch, check the voltage across each lamp in the simulation. | ||
| + | |||
| + | A lamp is assumed to light brightly if | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{\rm lamp}\geq 5~{\rm V}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | The simulation shows that the outer lamps have a sufficiently large voltage across them, while the inner lamps are bypassed by conducting diodes. | ||
| + | </ | ||
| + | # | ||
| + | </ | ||
| + | |||
| + | <WRAP half column> | ||
| + | # | ||
| + | The lamps | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | L_1 | ||
| + | \quad \text{and} \quad | ||
| + | L_5 | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | light up brightly. | ||
| + | # | ||
| + | </ | ||
| + | </ | ||
| + | |||
| + | 2. Determine which lamps remain dark. | ||
| + | |||
| + | <WRAP group> | ||
| + | <WRAP half column rightalign> | ||
| + | # | ||
| + | <WRAP leftalign> | ||
| + | The inner lamps are connected in parts of the circuit that are bypassed by forward-biased diodes. | ||
| + | |||
| + | A forward-biased diode has only a small voltage drop. Therefore, a lamp in parallel with such a diode path receives only a small voltage. | ||
| + | |||
| + | If | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{\rm lamp}< | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | the lamp does not light brightly. | ||
| + | </ | ||
| + | # | ||
| + | </ | ||
| + | |||
| + | <WRAP half column> | ||
| + | # | ||
| + | The lamps | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | L_2, | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | remain dark or almost dark. | ||
| + | # | ||
| + | </ | ||
| + | </ | ||
| + | |||
| + | # | ||
| + | |||
| + | |||
| + | # | ||
| + | # | ||
| + | |||
| + | The following simulation includes two diodes and two resistors. | ||
| + | |||
| + | Assume a simple constant-voltage diode model: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{\rm F}=0.6~{\rm V}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | The source voltage is | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_0=4.0~{\rm V}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | The resistors are | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | R_1=200~\Omega, | ||
| + | \qquad | ||
| + | R_2=100~\Omega. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | Calculate the currents through | ||
| + | |||
| + | * \(D_1\), | ||
| + | * \(R_1\), | ||
| + | * \(R_2\). | ||
| {{url> | {{url> | ||
| - | </ | + | 1. Calculate the current through \(R_1\). |
| + | <WRAP group> | ||
| + | <WRAP half column rightalign> | ||
| + | # | ||
| + | <WRAP leftalign> | ||
| + | The current through \(R_1\) passes through one forward-biased diode. | ||
| - | <panel type=" | + | Therefore the voltage across \(R_1\) is |
| - | The following simulation includes multiple diodes. Assume a simple diode model (the forward voltage drop is $V_{\rm F} = 0.7~\rm V$ and constant). The source voltage shall be $U0 = 5~\rm V$. | + | \[ |
| + | \begin{align*} | ||
| + | U_{R1} | ||
| + | = | ||
| + | U_0-U_{\rm F}. | ||
| + | \end{align*} | ||
| + | \] | ||
| - | Calculate the currents | + | Insert the values: |
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{R1} | ||
| + | &= | ||
| + | 4.0~{\rm V}-0.6~{\rm V} | ||
| + | \\ | ||
| + | &= | ||
| + | 3.4~{\rm V}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | Now apply Ohm's law: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{R1} | ||
| + | = | ||
| + | \frac{U_{R1}}{R_1} | ||
| + | = | ||
| + | \frac{3.4~{\rm V}}{200~\Omega} | ||
| + | = | ||
| + | 17~{\rm mA}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | </ | ||
| + | # | ||
| + | </ | ||
| + | |||
| + | <WRAP half column> | ||
| + | # | ||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{R1}=17~{\rm mA} | ||
| + | \end{align*} | ||
| + | \] | ||
| + | # | ||
| + | </ | ||
| + | </ | ||
| + | |||
| + | 2. Calculate the current | ||
| + | |||
| + | <WRAP group> | ||
| + | <WRAP half column rightalign> | ||
| + | # | ||
| + | <WRAP leftalign> | ||
| + | The current through \(R_2\) passes through two forward-biased diodes. | ||
| + | |||
| + | Therefore the voltage across \(R_2\) is | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{R2} | ||
| + | = | ||
| + | U_0-2U_{\rm F}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | Insert the values: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{R2} | ||
| + | &= | ||
| + | 4.0~{\rm V}-2\cdot 0.6~{\rm V} | ||
| + | \\ | ||
| + | &= | ||
| + | 2.8~{\rm V}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | Now apply Ohm's law: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{R2} | ||
| + | = | ||
| + | \frac{U_{R2}}{R_2} | ||
| + | = | ||
| + | \frac{2.8~{\rm V}}{100~\Omega} | ||
| + | = | ||
| + | 28~{\rm mA}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | </ | ||
| + | # | ||
| + | </ | ||
| + | |||
| + | <WRAP half column> | ||
| + | # | ||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{R2}=28~{\rm mA} | ||
| + | \end{align*} | ||
| + | \] | ||
| + | # | ||
| + | </ | ||
| + | </ | ||
| + | |||
| + | 3. Calculate the current through \(D_1\). | ||
| + | |||
| + | <WRAP group> | ||
| + | <WRAP half column rightalign> | ||
| + | # | ||
| + | <WRAP leftalign> | ||
| + | The diode \(D_1\) supplies both current paths. | ||
| + | |||
| + | Therefore, by Kirchhoff' | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1} | ||
| + | = | ||
| + | I_{R1}+I_{R2}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | Insert the values: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1} | ||
| + | &= | ||
| + | 17~{\rm mA}+28~{\rm mA} | ||
| + | \\ | ||
| + | &= | ||
| + | 45~{\rm mA}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | </ | ||
| + | # | ||
| + | </ | ||
| + | |||
| + | <WRAP half column> | ||
| + | # | ||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1}=45~{\rm mA} | ||
| + | \end{align*} | ||
| + | \] | ||
| + | # | ||
| + | </ | ||
| + | </ | ||
| + | |||
| + | # | ||
| + | |||
| + | |||
| + | # | ||
| + | # | ||
| + | |||
| + | The following simulation includes two diodes | ||
| + | |||
| + | Assume a simple constant-voltage diode model: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{\rm F}=0.7~{\rm V}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | The source voltage is | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_0=5.0~{\rm V}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | The resistor is | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | R_1=1.0~{\rm k}\Omega. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | Calculate the currents through | ||
| + | |||
| + | * \(R_1\), | ||
| + | * \(D_1\), | ||
| + | * \(D_2\), | ||
| + | |||
| + | depending on the switch state \(S\). | ||
| {{url> | {{url> | ||
| - | </ | + | 1. Calculate the currents for open switch \(S\). |
| + | |||
| + | <WRAP group> | ||
| + | <WRAP half column rightalign> | ||
| + | # | ||
| + | <WRAP leftalign> | ||
| + | With the switch open, only \(D_1\) is connected to the resistor path. | ||
| + | |||
| + | The conducting diode clamps the node voltage to approximately | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{\rm node}\approx U_{\rm F}=0.7~{\rm V}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | The resistor current is therefore | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{R1} | ||
| + | &= | ||
| + | \frac{U_0-U_{\rm F}}{R_1} | ||
| + | \\ | ||
| + | &= | ||
| + | \frac{5.0~{\rm V}-0.7~{\rm V}}{1.0~{\rm k}\Omega} | ||
| + | \\ | ||
| + | &= | ||
| + | 4.3~{\rm mA}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | Since only \(D_1\) conducts, | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1}=I_{R1}, | ||
| + | \qquad | ||
| + | I_{D2}=0. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | </ | ||
| + | # | ||
| + | </ | ||
| + | |||
| + | <WRAP half column> | ||
| + | # | ||
| + | For open switch: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{R1}& | ||
| + | \\ | ||
| + | I_{D1}& | ||
| + | \\ | ||
| + | I_{D2}& | ||
| + | \end{align*} | ||
| + | \] | ||
| + | # | ||
| + | </WRAP> | ||
| + | </ | ||
| + | |||
| + | 2. Calculate the currents for closed switch \(S\). | ||
| + | |||
| + | <WRAP group> | ||
| + | <WRAP half column rightalign> | ||
| + | # | ||
| + | <WRAP leftalign> | ||
| + | With the switch closed, \(D_1\) and \(D_2\) are connected in parallel. | ||
| + | |||
| + | The resistor current is still determined by the source voltage, the forward diode voltage, and \(R_1\): | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{R1} | ||
| + | &= | ||
| + | \frac{U_0-U_{\rm F}}{R_1} | ||
| + | \\ | ||
| + | &= | ||
| + | \frac{5.0~{\rm V}-0.7~{\rm V}}{1.0~{\rm k}\Omega} | ||
| + | \\ | ||
| + | &= | ||
| + | 4.3~{\rm mA}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | Kirchhoff' | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1}+I_{D2}=I_{R1}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | With the ideal constant-voltage diode model, the individual currents through two parallel diodes are not uniquely determined. | ||
| + | |||
| + | If both real diodes are approximately identical, the current splits approximately equally: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1} | ||
| + | \approx | ||
| + | I_{D2} | ||
| + | \approx | ||
| + | \frac{4.3~{\rm mA}}{2} | ||
| + | = | ||
| + | 2.15~{\rm mA}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | </ | ||
| + | # | ||
| + | </ | ||
| + | |||
| + | <WRAP half column> | ||
| + | # | ||
| + | For closed switch: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{R1}=4.3~{\rm mA} | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | and | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1}+I_{D2}=4.3~{\rm mA}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | For approximately identical real diodes: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1} | ||
| + | \approx | ||
| + | I_{D2} | ||
| + | \approx | ||
| + | 2.15~{\rm mA}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | # | ||
| + | </ | ||
| + | </ | ||
| + | |||
| + | 3. Explain why the current sharing is not unique in the simple model. | ||
| + | |||
| + | <WRAP group> | ||
| + | <WRAP half column rightalign> | ||
| + | # | ||
| + | <WRAP leftalign> | ||
| + | The constant-voltage diode model assumes that each conducting diode has exactly the same voltage drop: | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | U_{\rm D}=U_{\rm F}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | For two parallel diodes, this condition is true for many possible current distributions. | ||
| + | |||
| + | Therefore, the model only determines the sum | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1}+I_{D2}, | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | not the individual diode currents. | ||
| + | </ | ||
| + | # | ||
| + | </ | ||
| + | |||
| + | <WRAP half column> | ||
| + | # | ||
| + | The constant-voltage diode model determines only | ||
| + | |||
| + | \[ | ||
| + | \begin{align*} | ||
| + | I_{D1}+I_{D2}=4.3~{\rm mA}. | ||
| + | \end{align*} | ||
| + | \] | ||
| + | |||
| + | It does not uniquely determine \(I_{D1}\) and \(I_{D2}\) separately. | ||
| + | |||
| + | <callout type=" | ||
| + | Parallel diodes are sensitive to small differences in real diode characteristics. | ||
| + | Current sharing should not be assumed to be perfect without checking the design. | ||
| + | </ | ||
| + | # | ||
| + | </ | ||
| + | </WRAP> | ||
| + | |||
| + | # | ||
| Line 578: | Line 1100: | ||
| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| - | U_{\rm | + | U_{\rm |
| \end{align*} | \end{align*} | ||
| \] | \] | ||
| Line 604: | Line 1126: | ||
| R_{\rm V} | R_{\rm V} | ||
| &= | &= | ||
| - | \frac{U_{\rm | + | \frac{U_{\rm |
| \\ | \\ | ||
| &= | &= | ||
| Line 628: | Line 1150: | ||
| P_R | P_R | ||
| &= | &= | ||
| - | (U_{\rm | + | (U_{\rm |
| \\ | \\ | ||
| &= | &= | ||
| Line 659: | Line 1181: | ||
| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| - | U_{\rm | + | U_{\rm |
| \end{align*} | \end{align*} | ||
| \] | \] | ||
| Line 692: | Line 1214: | ||
| I_{\rm V} | I_{\rm V} | ||
| &= | &= | ||
| - | \frac{U_{\rm | + | \frac{U_{\rm |
| \\ | \\ | ||
| &= | &= | ||