Transcript A ) Vo = ( R1 + R2 )

Linear Power Supplies
Objectives
• Revision of linear power supply
• Introduction to linear regulator chip
• Introduction of various power supplies
Unregulated Linear Power Supply
Vmains
Regulated Linear Power Supply
Regulator
Vmains
IC Regulator
Internal
Vref
+ -
IC Regulator
Vf
Basic Elements of
Voltage Regulator
Vi
Internal
Vref
R2
Vo
+ -
IC Regulator
Vf
R1
Basic Elements of
Voltage Regulator
Vi
Internal
Vref
R2
Vo
+ -
IC Regulator
Vf = VoR1 / ( R1 + R2 )
Vf
R1
Basic Elements of
Voltage Regulator
Vi
Internal
Vref
R2
Vo
+ -
IC Regulator
Vf = VoR1 / ( R1 + R2 )
therefore
Vo = Vf ( R1 + R2 )/R1
Vf
R1
Basic Elements of
Voltage Regulator
Internal
Vref
Vi
R2
Vo
+ -
IC Regulator
Vf = VoR1 / ( R1 + R2 )
therefore
Vo = Vf ( R1 + R2 )/R1
Vf = Vref
Vf
R1
Basic Elements of
Voltage Regulator
Internal
Vref
Vi
R2
Vo
+ -
Vf
R1
IC Regulator
Vf = VoR1 / ( R1 + R2 )
therefore
therefore
Vo = Vf ( R1 + R2 )/R1
Vf = Vref
Note
Vo = Vf ( R1 + R2 )/R1
R1 and R2 are called “output
voltage programming resistors
Voltage Regulator
with Current
Limiting
Current Sense
Threshold Voltage
Rcl
Internal
Vref
Vi
R2
Vo
+ -
Vf
R1
IC Regulator
Vf = VoR1 / ( R1 + R2 )
therefore
therefore
Vo = Vf ( R1 + R2 )/R1
Vf = Vref
Note
Vo = Vf ( R1 + R2 )/R1
R1 and R2 are called “output
voltage programming resistors
Voltage Regulator
with high Current
Rating
Power
Transistor
Current Sense
Threshold Voltage
Rcl
Internal
Vref
Vi
+ -
R2
Vf
R1
Vo
IC Regulator
Vf = VoR1 / ( R1 + R2 )
therefore
therefore
Vo = Vf ( R1 + R2 )/R1
Vf = Vref
Note
Vo = Vf ( R1 + R2 )/R1
R1 and R2 are called “output
voltage programming resistors
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = >
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
B ) Rcl = VTH / RTH =
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
B ) Rcl = VTH / RTH = 0.6 / 2 = 0.3 
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
B ) Rcl = VTH / RTH = 0.6 / 2 = 0.3 
C ) Vi(min) = VT ( min)+ Vcl + Vo =
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
B ) Rcl = VTH / RTH = 0.6 / 2 = 0.3 
C ) Vi(min) = VT ( min)+ Vcl + Vo = 3.5 + 0.6 + 12 = 16.1 V
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
B ) Rcl = VTH / RTH = 0.6 / 2 = 0.3 
C ) Vi(min) = VT ( min)+ Vcl + Vo = 3.5 + 0.6 + 12 = 16.1 V
C ) Vi(max) = VT ( max)+ Vcl + Vo
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
B ) Rcl = VTH / RTH = 0.6 / 2 = 0.3 
C ) Vi(min) = VT ( min)+ Vcl + Vo = 3.5 + 0.6 + 12 = 16.1 V
C ) Vi(max) = VT ( max)+ Vcl + Vo
and VT ( max) = PT ( max) / IL ( max) = 40 / 2 = 20 V
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
B ) Rcl = VTH / RTH = 0.6 / 2 = 0.3 
C ) Vi(min) = VT ( min)+ Vcl + Vo = 3.5 + 0.6 + 12 = 16.1 V
C ) Vi(max) = VT ( max)+ Vcl + Vo
C ) Vi(max) = 20 + 0.6 + 12 = 32.6 V
and VT ( max) = PT ( max) / IL ( max) = 40 / 2 = 20 V
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
B ) Rcl = VTH / RTH = 0.6 / 2 = 0.3 
C ) Vi(min) = VT ( min)+ Vcl + Vo = 3.5 + 0.6 + 12 = 16.1 V
C ) Vi(max) = VT ( max)+ Vcl + Vo
C ) Vi(max) = 20 + 0.6 + 12 = 32.6 V
D )  = Po / Pi
and VT ( max) = PT ( max) / IL ( max) = 40 / 2 = 20 V
Example : The internal reference voltage of a linear IC regulator chip is 3 volts. The current
sense threshold voltage is 0.6 volts. It is used with an external series pass transistor to
operate up to a current limit of 2A. The minimum differential voltage needed for this transistor
is 3.5 volts. The maximum collector power dissipation permissible for the external transistor is
40 Watts. The regulator output required is 12 volts. Determine : A ) Suitable values for output
voltage programming resistors, B ) The value of current limit resistor, C ) The minimum
and maximum possible limits of the unregulated DC input, and D ) The conversion efficiency.
A ) Vo = ( R1 + R2 ) Vf / R1 = > 12 = ( R1 + R2 ) 3 / R1 => R2 = 3*R1
if R1 = 20K, then R2 =60K
B ) Rcl = VTH / RTH = 0.6 / 2 = 0.3 
C ) Vi(min) = VT ( min)+ Vcl + Vo = 3.5 + 0.6 + 12 = 16.1 V
C ) Vi(max) = VT ( max)+ Vcl + Vo
and VT ( max) = PT ( max) / IL ( max) = 40 / 2 = 20 V
C ) Vi(max) = 20 + 0.6 + 12 = 32.6 V
D )  = Po / Pi = ( 12 * 2 ) / [ 40 + ( 12 * 2 ) + ( 0.6 * 2 ) ] = 3 6.8 %