Fig. 1 - Symmetrical Adjustable Power Supply 1.25V to 47V 10 Amps with Short Circuit Protection |

**Symmetrical Adjustable Power Supply**can vary its output voltage from

**1.25V to 47V**, based on the

**LM317HV**Linear Voltage Regulator Integrated Circuit for positive voltage and the

**LM337HV**for negative voltage, which together with the NPN transistors

**TIP 35C**and the PNP transistor

**TIP36C**provide a current of

**10 amps**.

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## High Voltage Adjustable Regulator

**LM317HV**and

**LM337HV**voltage regulators are adjustable 3-terminal voltage regulators capable of delivering currents of 1.5A or more over an output voltage range of

**1.25V**to

**50V**.

**LM317HV**and

**LM337HV**offer overload protection such as current limiting, thermal overload protection, and safe-area protection, that make the device breakdown-proof. The overload protection circuit remains fully functional even if the setting terminal is disconnected.

**47V**, because the

**LM337HV**negative voltage regulator supports a maximum of

**50V**, unlike the

**LM317HV**which supports up to

**60V**.

## How the Circuit Works

**LM**s Integrated Circuit and mirror image "

*Same function, just in a negative way*".

**R1**and

**R2**are

**10 ohm**resistors that have the function of

**Load Sensor**, they receive the current flowing through the circuit, and while this current does not reach the current calculated across the resistors

**R1**and

**R2**, the circuit behaves like a normal voltage regulator, because for small "

*calculated*" currents there is no voltage drop across the

**Load Sensing resistor**, so the Boosters Transistors

**TIP36C**and

**TIP35C**are not activated.

**R1**increases, when this voltage reaches about

**0.6V**"

*transistor turn-off voltage*", the power stage is activated and current flows through it.

## The Protection Circuit

**BD140**PNP and Q2

**BD139**NPN, each for an output bias voltage.

*Calculated*", which is fixed at

**10 amps**, and work together with

**resistors**

*0.06ohm***R3**and

**R4**as a current sensing resistor, which is used to polarize transistors

**Q1**and

**Q2**, so that, depending on the determined value, they limit the output current of the entire circuit according to a simple formula from Ohms Law, which is used to set this limiting current.

## Formula 1st Ohm's Law

**First Ohm's Law**states that the potential difference between two points of a resistor is proportional to the electrical current established in it, and the ratio of electrical potential to electrical current is always constant for ohmic resistors. The formula is given by:

**V = R * I**

**V**- Voltage or Electrical Potential

**R**- Electrical Resistance

**I**- Electrical Current

**ohms law**, we can now calculate the values of the

**Load Sense resistors**, which activates the power step, and the bias resistors of the protection transistors, which is the

**Short Circuit protection circuit**.

### Load Resistor Calculation

**LM317hv**Voltage Regulator, which according to the datasheet is

**1.5 amps**.

**LM317HV & LM337HV = 1.5A**

**R1**, knowing that the same calculation is done for

**R2**. We know that

**Ohm's Law**gives us the following expression:

**V = R * I**

**V**= The cutoff voltage of transistors

**Q3, Q4**&

**Q5**, which follows the same principle for set

**Q6, Q7 & Q8**, is

**0.6V**"

*Which is the Transistor cutoff region*". Let's call

**Q3**,

**Q4**&

**Q5**as a

**Qeq**.

**I**= It is the current of the regulator

**CI1**, let's put the working current of the

**CI1**at 300mA, which is equal to 0.3A, with this current we won't need to put a heatsink on it.

**Then:**

**R1**= Vbe_Qeq / I_CI1

**R1**= 0.6V / 0.3A

**R1**=

**2 ohms**

### Protection Circuit Resistor Calculation

**10 Amps**.

**Power Supply = 10A**

**R3**, knowing that the same calculation is done for

**R4**. We know that Ohm's Law gives us the following expression:

**V = R * I**

**V**= The cutoff voltage of transistor

**Q1**, which follows the same principle as for transistor

**Q2**, is 0.6V "

*Which is the Transistor cutoff region*".

**I**= It is the total current of PS, which is

**10A**.

**Then:**

**R1**= Vbe_Q1 / I_ps

**R1**= 0.6V / 10A

**R1**=

**0.06 ohms**

### Power Transistors Current

**NOTE:**Remembering that the power of

**TIP36C**transistors is

**125W**, this means that it works with current from

**25A to 5V**, remember the formula above,

**P=V*I**;

**P = 5V * 25A = 125W**.

**For this circuit**with a maximum voltage of

**47V**, and transistors with a maximum power of

**125W**, we look like this:

**Pmax = V * I:**

**Imax**= P / V =>

**Imax**= 125W / 47V =>

**Imax**=

**2.66A**

**7.98A**

**TIP36C**transistors to achieve

**10 amps**at the output.

**we have the schematic diagram of the adjustable power supply circuit with short circuit protection, so those who accompany us already know this circuit very well, the difference is exactly the implantation of the symmetry of the circuit and the protection circuit, as we can see below.**

*Figure 2*## The Power Transformer

*3 wires*". The transformer must be able to supply at least

**10A**at the output. The primary, "input voltage", must match the voltage in your area;

**110V or 220Vac**. The secondary, "output voltage" should be

**36 - 0V - 36Vac**.

## Component List

**Semiconductors**- U1 ....................... LM317HV Voltage Regulator
- U2 ....................... LM337HV Voltage Regulator
- Q1 ....................... PNP BD140 Transistor
- Q2 ....................... NPN BD139 Transistor
- Q3, Q4, Q5 ......... PNP TIP36C Power Transistor
- Q6, Q7, Q8 ......... NPN TIP35C Power Transistor
- D1 ...................... KBPC5010 - 50A Rectifier Bridge
- D2, D3 ............... 1N4007 Diode Rectifier
**Resistors**- R1, R2 ................ 2Ω / 2W Resistor
- R3, R4 ................ 0.06Ω / 5W Resistor
- R5, R6 ................ 5KΩ / 1/8W Resistor
- R7, R8 ................ 120Ω / 1/8W Resistor
- R9, R10, R11 ...... 0.1Ω / 5W Resistor
- R12, R13, R14 .... 0.1Ω / 5W Resistor
- RV1 .................... 5KΩ Potentiometer
**Capacitors**- C1, C2 ................ 5600uF - 63V Electrolytic capacitor
- C3, C4 ................ 10uF - 63V Electrolytic capacitor
- C5, C6 ................ 1000uF - 63V Electrolytic Capacitor
**Others**- P1, P2 ................. Connector 3 screw terminal 5mm 3 Pins
- Others ................. Wires, Solders, pcb, etc.

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Parts list values of transistors and capacitor interchanged,compared with schematic diagram

ReplyDeleteThank you very much for your feedback.

DeleteWe have updated the list with the appropriate corrections.

Thank you!

Oi

ReplyDeleteHi @BINHO

DeleteWelcome!

Regards!