1. Presented by: Sanjay Pithadia SEM – Industrial Systems, Medical Sector
Designing High-Voltage, Programmable Power Supply for driving High-current Pulsed loads Part - 2
Presented by: Sanjay Pithadia
SEM – Industrial Systems, Medical Sector
Hello  everyone and Welcome to Part two of the training series on Designing High-Voltage Programmable Power Supply for driving high-current pulsed loads.

2. Challenge to Solve Floating the regulators to support high voltages
In  this video, we will go through tricks of floating the regulators to support high voltages.

3. Need of Floating Regulators
A linear regulator operates by using a voltage- controlled current source to force a fixed voltage to appear at the regulator output terminal.
The control circuitry must monitor (sense) the output voltage, and adjust the current source (as required by the load) to hold the output voltage at the desired value.
Any regulator has datasheet specifications controlled by the semiconductor process.
To operate the device safely without crossing the absolute maximum limits of the regulator, it needs some tricks to float the voltage levels.
Before  we start looking into trick for floating the regulators, let’s understand the need of floating regulators.
A  linear regulator operates by using a voltage-controlled current source to force a fixed voltage to appear at the regulator output terminal.
The  control circuitry must monitor (sense) the output voltage, and adjust the current source (as required by the load) to hold the output voltage at the desired value.
Any  regulator has datasheet specifications controlled by the semiconductor process.
To  operate the device safely without crossing the absolute maximum limits of the regulator, it needs some tricks to float the voltage levels.

4. It is NOT a new concept! Positive Floating Regulator using µA723
LDO & Op-amp have to be high-voltage
Floating  regulators is not a new concept. It has been in practice for a very long time. For  example, standard regulator 723, which is taught in high-schools and universities, 723 can be used in a floating configuration as shown here.
If  we want to use latest regulators like TPS7A47 from Texas Instruments, the ground pin needs to be floated by using some external circuits. For  example, using a high-voltage LDO and op-amp the floating circuit can be built.

5. Designing the floating regulator circuit
Ground Pin Current is provided in the datasheet of regulator.
TPS7A47
TPS7A30
In  this training we are showing a different trick which does not use high voltage op-amps and LDOs. It uses a single high-voltage bipolar junction transistor or BJT. The concept is applied to float positive as well as negative voltage regulators.
To design the floating circuit, let’s look at the regulator parameter used for the calculations. Each  regulator datasheet provides “ground pin current” value in the datasheet. It is the current which flows from ground pin of the regulator to the actual ground of the circuit. the total input current is sum of output current as well as ground pin current.
For example, looking at the datasheet of TPS7A47 , which is a 36V positive voltage regulator from Texas Instruments, the ground pin current is 6.1 milli ampere at output current of 1 ampere.
Similarly, TPS7A30  is -36V negative voltage regulator from Texas Instruments and the ground pin current is 950 micro amperes at otuptu current of 100 milli amperes.

6. DC Amplifier for Floating the Regulator
Control Voltage
(varied from 0V to 10V)
𝑉𝑖𝑟𝑡𝑢𝑎𝑙 𝐺𝑁𝐷=( 380𝑘 20𝑘 +1)× 𝑉 𝐶𝑁𝑇𝐿 =20× 𝑉 𝐶𝑁𝑇𝐿
Let’s  look at the floating positive voltage regulator circuit. To  float the ground of the regulator, a DC amplifier is created as shown in this schematic. It uses TLV171, which is a 36-V low-power rail-to-rail-output operational amplifier from Texas Instruments. It is configured as an integrator. The  22 kilo ohms resistor and 100 nano farad capacitor are the integrating components. The negative feedback for the op-amp occurs through the capacitor. The output of op-amp drives BJT.
As we have seen before, each regulator datasheet provides information about Ground Pin Current. This  current is used here to lock the output of op-amp with the gain  of 20. The ground pin current of the regulator is divided into two paths – one through the BJT and another through the gain resistors.
The  virtual ground is always 20 times the Vcontrol voltage. For example, with VCNTRL = 5V, the virtual ground is at 99.99V.
The  graphs on the right show DC transfer characteristic with respect to VCNTRL. The  control voltage is varied from 0V to 10V and Virtual GND voltage changes from 0 to 200V accordingly.

7. Negative Regulator – Virtual Ground Simulation Results
Control Voltage
(varied from 0V to 10V)
𝑉𝑜𝑢𝑡= 940𝑘 47𝑘 × 𝑉 𝐶𝑁𝑇𝐿 =20× 𝑉 𝐶𝑁𝑇𝐿
A  similar DC amplifier approach can be used for floating negative voltage regulators also. Since  the output of regulator is negative and control voltage is positive, it needs two stage implementation. The first stage is an integrator using  resistor of 90 kilo ohms and capacitor of 100 nano farads. A PNP transistor is driven by the output of integrator. The control voltage is compared with a attenuated output of the regulator by a factor of 20 . The implementation is such that the DC amplifier locks in always at a ratio of 20.
For example, with VCNTRL = 5V, the output of regulator is at V.
The  graphs on the right show DC transfer characteristic with respect to VCNTRL. The  control voltage is varied from 0V to 10V and output voltage of regulator changes from 0 to -200V accordingly.

8. TIDA-01371 is available on TI.com
Visit to find design resources (Gerbers, Schematics and more).
This  floating DC amplifiers circuits are implemented in TI Design TIDA available on TI web. For more information and reading, visit

9. TI Information – Selective Disclosure
Thank  you for watching.