Simple High Current Voltage Regulator Circuit using LM317 and LM195

A simple circuit made for controlling high current voltage helps to provide a steady voltage while handling big current needs.

In this post the LM317 voltage regulator works together with the LM195 power transistor to create a steady output that can give more current than the LM317 can do by itself.

The LM195 is a special power transistor that has built-in safety features to protect against overloads.

The High Current Voltage Regulator Circuit using LM317 and LM195 can handle an output current of up to 600mA.

This kind of circuit is really useful when you need a low dropout and high current voltage regulation solution.

Circuit Working:

Parts List:

In this article the circuit has two main parts:

The first part is the LM317 IC1, which is a special piece that helps control the output voltage.

The second part is the LM195 Q1 a power transistor that helps the circuit manage more current.

The input voltage Vs can change from 10V to 40V giving power to the whole circuit.

The LM317 keeps the voltage steady by changing its output through the adjust pin which is pin 1.

At the same time the LM195 acts like a current booster.

The LM195 gets its signal from the LM317 and then it sends out the final regulated voltage.

To keep the current steady resistor R1 is used to stabilize the current regulation.

Resistor R2 controls the amount of current that goes into the base of the power transistor LM195 making sure it works safely.

Capacitor C1 helps to clean up any noise in the power supply.

This circuit is made to provide an output current of up to 600mA.

Formulas with Calculations:

Below are the formulas with calculations for Simple High Current Voltage Regulator Circuit using LM317 and LM195:

Output Voltage Formula:

Since the LM195 transistor is in an emitter follower configuration, the output voltage is approximately:

Vout​ = VLM317 output​− VBE​

• VLM317 output​ is the output voltage of the LM317.
• VBE is the base emitter voltage drop of the LM195 which is around 0.7V to 1V depending on load current

So, if the LM317 is set to 5V then:

Vout = 5V − 0.7V = 4.3V

For higher output voltages set LM317 to output (Vout + 0.7V)

Output Current Formula:

The maximum current delivered by this circuit depends on the LM317s current and the gain of LM195.

The current through R1 plays a role in stabilizing this.

The current gain of LM195 is high, so the output current is approximately:

Iout​ = 1.25V​ / R1

Since R1= 2.4Ω we get:

Iout​ = 1.25V / 2.4Ω​ = 0.52A (520mA)

This means the circuit can provide around 520mA of output current.

If you need more current reducing R1 will increase it.

Power Dissipation Formula:

Power dissipation is important especially for LM195, which must handle the excess power as heat.

The power dissipated by LM195 is:

PLM195 = (Vin−Vout) × Iout

For example, if Vin = 12V and Vout = 5V, with Iout = 0.52A, then:

PLM195 = (12V−5V) × 0.52A = 3.64W

This means LM195 needs proper heat sinking to avoid overheating.

How to Build:

To build a Simple High Current Voltage Regulator Circuit using LM317 and LM195 follow the below mentioned steps for connections:

• Assemble all the components as mentioned in the above circuit diagram:
• Connect ADJUST pin 1 of IC1 to GND
• Connect OUTPUT pin 2 of IC1 to one terminal of resistor R1 and other terminal of R1 connect to GND
• Connect INPUT pin 3 of IC1 to the junction of emitter of power transistor Q1 and output supply of 600mA
• Connect the base pin of power transistor Q1 to input supply through resistor R2
• Connect the collector of Q1 transistor to Vs power supply of 10V to 40V
• Connect capacitor C1 positive to Vs power supply of 10V to 40V and negative of capacitor C1 to GND.

Conclusion:

Simple High Current Voltage Regulator Circuit using LM317 is an easy method to increase current capacity while keeping the voltage steady.

It is perfect for situations where you need a reliable and strong power supply.

To make sure it works well, it is important to manage heat dissipation properly.

References:

High current voltage regulator

LM195/LM395 Ultra Reliable Power Transistors