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