Linear Power Supplies Objectives Revision of linear power supply Introduction to linear regulator chip Introduction of various power supplies

V mains Unregulated Linear Power Supply

V mains Regulated Linear Power Supply Regulator

+ - IC Regulator Internal Vref VfVf IC Regulator

+ - Internal Vref VfVf Basic Elements of Voltage Regulator ViR2 R1 Vo

+ - IC Regulator Internal Vref VfVf Basic Elements of Voltage Regulator ViR2 R1 Vo Vf = VoR1 / ( R1 + R2 )

+ - IC Regulator Internal Vref VfVf Basic Elements of Voltage Regulator ViR2 R1 Vo Vf = VoR1 / ( R1 + R2 ) therefore Vo = Vf ( R1 + R2 )/R1

+ - IC Regulator Internal Vref VfVf Basic Elements of Voltage Regulator ViR2 R1 Vo Vf = VoR1 / ( R1 + R2 ) therefore Vo = Vf ( R1 + R2 )/R1 Vf = Vref

+ - IC Regulator Internal Vref VfVf Basic Elements of Voltage Regulator ViR2 R1 Vo Vf = VoR1 / ( R1 + R2 ) therefore Vo = Vf ( R1 + R2 )/R1 Vf = Vref therefore Vo = Vf ( R1 + R2 )/R1 Note R1 and R2 are called “output voltage programming resistors

+ - IC Regulator Internal Vref VfVf Voltage Regulator with Current Limiting ViR2 R1 Vo Rcl Current Sense Threshold Voltage Vf = VoR1 / ( R1 + R2 ) therefore Vo = Vf ( R1 + R2 )/R1 Vf = Vref therefore Vo = Vf ( R1 + R2 )/R1 Note R1 and R2 are called “output voltage programming resistors

+ - IC Regulator Internal Vref VfVf Voltage Regulator with high Current Rating ViR2 R1Vo Rcl Current Sense Threshold Voltage Power Transistor Vf = VoR1 / ( R1 + R2 ) therefore Vo = Vf ( R1 + R2 )/R1 Vf = Vref therefore Vo = Vf ( R1 + R2 )/R1 Note 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.

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 if R1 = 20K, then R2 =60K => 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 = > B ) Rcl = V TH / R TH = 12 = ( R1 + R2 ) 3 / R1 if R1 = 20K, then R2 =60K => 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 = > B ) Rcl = V TH / R TH = 12 = ( R1 + R2 ) 3 / R1 if R1 = 20K, then R2 =60K 0.6 / 2 = 0.3  => 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 = > B ) Rcl = V TH / R TH = 12 = ( R1 + R2 ) 3 / R1 if R1 = 20K, then R2 =60K 0.6 / 2 = 0.3  C ) Vi(min) = V T ( min)+ Vcl + Vo = => 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 = > B ) Rcl = V TH / R TH = 12 = ( R1 + R2 ) 3 / R1 if R1 = 20K, then R2 =60K 0.6 / 2 = 0.3  C ) Vi(min) = V T ( min)+ Vcl + Vo = = 16.1 V => 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 = > B ) Rcl = V TH / R TH = 12 = ( R1 + R2 ) 3 / R1 if R1 = 20K, then R2 =60K 0.6 / 2 = 0.3  C ) Vi(min) = V T ( min)+ Vcl + Vo = = 16.1 V C ) Vi(max) = V T ( max)+ Vcl + Vo => 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 = > B ) Rcl = V TH / R TH = 12 = ( R1 + R2 ) 3 / R1 if R1 = 20K, then R2 =60K 0.6 / 2 = 0.3  C ) Vi(min) = V T ( min)+ Vcl + Vo = = 16.1 V C ) Vi(max) = V T ( max)+ Vcl + Vo and V T ( max) = P T ( max) / I L ( max) = 40 / 2 = 20 V => 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 = > B ) Rcl = V TH / R TH = 12 = ( R1 + R2 ) 3 / R1 if R1 = 20K, then R2 =60K 0.6 / 2 = 0.3  C ) Vi(min) = V T ( min)+ Vcl + Vo = = 16.1 V C ) Vi(max) = V T ( max)+ Vcl + Vo and V T ( max) = P T ( max) / I L ( max) = 40 / 2 = 20 V C ) Vi(max) = = 32.6 V => 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 = > B ) Rcl = V TH / R TH = 12 = ( R1 + R2 ) 3 / R1 if R1 = 20K, then R2 =60K 0.6 / 2 = 0.3  C ) Vi(min) = V T ( min)+ Vcl + Vo = = 16.1 V C ) Vi(max) = V T ( max)+ Vcl + Vo and V T ( max) = P T ( max) / I L ( max) = 40 / 2 = 20 V C ) Vi(max) = = 32.6 V D )  = Po / Pi => 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 = > B ) Rcl = V TH / R TH = 12 = ( R1 + R2 ) 3 / R1 if R1 = 20K, then R2 =60K 0.6 / 2 = 0.3  C ) Vi(min) = V T ( min)+ Vcl + Vo = = 16.1 V C ) Vi(max) = V T ( max)+ Vcl + Vo and V T ( max) = P T ( max) / I L ( max) = 40 / 2 = 20 V C ) Vi(max) = = 32.6 V D )  = Po / Pi = ( 12 * 2 ) / [ 40 + ( 12 * 2 ) + ( 0.6 * 2 ) ] = % => R2 = 3*R1