Electronics Overview : the Property of One- way Conduction of diodes 1. forward bias （ P is positive and N is nagative ） the current flow is significant 1. forward bias （ P is positive and N is nagative ） the current flow is significant 2. reverse bias （ P is nagative and N is positive ） the current flow is very small 2. reverse bias （ P is nagative and N is positive ） the current flow is very small 3. No any one-way conduction when diodes work beyond U BK 3. No any one-way conduction when diodes work beyond U BK 4. Reverse current flow will be influnced by temperature. 5.The property of saturation of reverse current flow.

Electronics Chapter6 Sources of Stable DC Voltage(Page 167) 1. Diode Rectifiers 2. Power Supply Filtering 3. Voltage Regulator

Electronics Sources of Stable DC Voltage The small power supply u4u4 uouo u3u3 u2u2 u1u1 AC Load TransformerRectifier Filter Regulator DC

Electronics 1. Diode Rectifiers Half-Wave Rectifier Full-Wave Bridge Rectifier

Electronics Half-Wave Rectifier – + + – a Tr D uouo u b RLRL ioio 动画 u tt O uouo O ?To calculate the average value of output voltage

Electronics Full-Wave Bridge Rectifier  － tt RLRL u ioio uouo a b + – + –  － 动画 uouo u Positive half cycle,D1\D3 conduct,D2\D4 are reverse biased ?To calculate the average value of output voltage

Electronics Full-Wave Bridge Rectifier D 1 RLRL uouo D6D6 D 3 D5D5 D4D4 D2D2 ioio C b a u + + – – o Common cathode Common anode

Electronics From time t 1 ~t 2 : u o =u ab D 1 RLRL uouo D6D6 D 3 D5D5 D4D4 D2D2 ioio C b a u + + – – o Output voltage u:The transformer secondary voltage 动画 u o ubub uCuC uaua 22  uouo o t1t1 t2t2 t3t3 t4t4 t5t5 t6t6 t7t7 t8t8 t9t9

Electronics t1t1 t2t2 t3t3 t4t4 t5t5 t6t6 t7t7 t8t8 t9t9 uouo o D 1 RLRL uouo D6D6 D 3 D5D5 D4D4 D2D2 ioio c b a u + + – – o 负载电压 u o uaua ubub uCuC 22 

Electronics Homework To calculate the average value of output voltage in half and full-wave rectifier circuits. To calculate the average value of current of every diode in half and full-wave rectifier circuits To calculate the maximum reverse bias voltage that every diode endures in half and full-wave rectifier circuits

Electronics 2.Power Supply Filtering u RLRL uouo + + – – ~ + C C: Smoothing Capacitor

Electronics 2.Power Supply Filtering + C icic i – + + – a D uouo u b RLRL ioio = u C 动画 uouo u tt O tt O (T — the period of voltage)

Electronics iDiD tt uouo tt O O I peak I peak To choose diodes: I OM =2 I D I OM =2 I D R L C is larger  the peak valure of i D is larger

Electronics 3. Voltage Regulator Zener Diode Shunt Regulator Voltage Regulator

Electronics Zener Diode Shunt Regulator U I UZUZ + – UIUI RLRL + C IOIO UOUO + – + – u IRIR R DZDZ IzIz Stable voltage circuit

Electronics Zener Diode(Page 11) U Z (2CW13:5~6.5V) Voltage stable constant (Page 12) Figure U I UZUZ

Electronics Zener Diode Shunt Regulator(Page 176) U O = U Z U O +U R = U I I R = I O + I Z U I UZUZ RL(IO) IR RL(IO) IR  to assume R L is changed U O   I R (I R R)   U O (U Z )   IZ  IZ   + – UIUI RLRL + C IOIO UOUO + – + – u IRIR R DZDZ IzIz Stable voltage circuit

Electronics UiUi T R2R2 UZUZ RLRL UOUO  + – R3R3 + + – – + UBUB + – DZDZ + – UfUf + – R1R1 Zener Diode Shunt Regulator(Page 177) there are four parts. regular amplifier reference sample

Electronics output UiUi T R2R2 UZUZ RLRL UOUO  + – R3R3 + + – – + UBUB + – DZDZ + – UfUf + – R1R1

Electronics IC Voltage Regulator Three points The constant voltage output Flexible voltage output Positive output 78XX negative output 79XX （ ~ 37 V ）

Electronics Introduction of points W7800 1— input 3 — common 2 — output W — common 3— input 2 — output

Electronics (1) constant voltage output (1) constant voltage output U input - U output is more than 3V COCO W7805 CiCi UiUi +_+_ +_+_ UOUO ~1  F 1F1F To improve transiet output To imorove the wave

Electronics (2) Both positive and negative voltage output V 24V + C + C W7815 CiCi +15V 12 3 CiCi W COCO COCO – 15V 1F1F 1F1F 0.33  F 1000  F

Electronics ? What is significant as a voltage source?