Linear regulator 7805

Linear power supply

Linear regulator

Linear regulator 7805

Linear regulator 7805

7805 Positive regulator

Linear regulator 7905

7905 Negative regulator

Linear regulator 7805 / 7905

Linear regulator 7805

Linear regulator 7805

• SOA = Safety Operating Area• Uinmax / Uout defined • Imax defined• Pmax Umax * Imax

Linear regulator 7805

Linear regulator 7805

Linear regulator 7805

Linear regulator 7805

Linear regulator 7805

Linear regulator 7805

• Regulator measures the output voltage all the time;

• Q: Is the output voltage too small? A: Yes! => Action: Increase the output voltage/current!

• Q: Is the output voltage too small? A: No, it is too high! => Action: Decrease the output voltage/current!

• Q: Is the output voltage too small? …• =>Oscillation

Linear regulator 7805Output voltage without capacitor

Linear regulator 7805

• High frequency oscillation disturbs the operation of the equipment that regulator is used for.

• Oscillation consumes additional energy =>increased power loss => more heat

Linear regulator 7805

Input current = output current (even more)

Linear regulator 7805

Linear regulator 7805

Linear regulator 7805

Linear regulator 7805

Linear regulator 7805

Linear regulator 7805

Vin = 7,02 VVout = 5,02 VV dropout = 2,00 VRL = 1000 f = 50 Hz

Linear regulator 7805

RL = 100 f = 50 Hz

Linear regulator 7805

RL = 1000 Vin = 6,9 V Vac = 20 Vpp

f / Hz Vout / V picture50 4,99 1

100 5,02 2500 5,02 3

1000 5,02 45000 5,02 5

15000 5,02 620000 5,02 7

Linear regulator 7805

picture1 picture 2

Linear regulator 7805

picture 3 picture 4

Linear regulator 7805

picture 5 picture 6

Linear regulator 7805

picture 7

Linear regulator 7805

RL = 100Vin = 3,87 V (DMM) ? Vac = 20 Vpp

f / Hz Vout / V (Dmm) 50 2,40 ?

100 ?500 ?

1000 ?5000 ?

15000 ?20000 ?

Linear regulator 7805

f=50Hz RL =100 f=100Hz RL =100

Linear regulator 7805

f=500Hz RL =100 time scale made wider

Linear regulator 7805

f=1000Hz f= 5000HzRL = 100

Linear regulator 7805

f=15000Hz f= 20000HzRL = 100

Linear regulator 7805

max output from generator

after half-waverectification

Linear regulator 7805

Linear regulator 7805

• A current i(t) in a pure resistor R results in a power p(t) with an average value P

• This same power P could be produced by a constant (direct) current I. Then i(t) is said to have an effective value IRMS equivalent to this constant current. The same applies to voltage functions where effective value in VRMS

Linear regulator 7805

Half wave rectified voltage Root Mean Square = RMS = effective value

Vin max (from generator output) 20 Vpp

T

RMS dttVT

V0

2 )(1

Linear regulator 7805

Linear regulator 7805

xxxdx 2sin41

2sin 2

substitution:

0sin41

202sin

41

22102

2RMSV

=0 =0 = 0

52

104

1022

RMSRMS VV

Linear regulator 7805

• Generator output impedance (internal R) = 50

• Voltage drop across diode = 0,7V (not taken into account)

• Using higher frequency eliminates the need of big capacitor

• With low-ohmic loads full-wave rectifier highly recommended