Before getting to 12v to 5v converter circuit using different methods lets a glance at the need of 5 volt supply.
A wide range of IC’s and automation controller devices require 5 V DC supply for their operation, in the absence of 5 volt supply we might be needed to derive it from the existing power supply then comes these linear converter for help. Here’s the list of all possible circuits but their application differs from circuit to circuit. We already discussed 9v to 5v converter circuit previously.
These circuits are basic voltage regulators, the first one is simple voltage divider using resistors.
All the circuits have different performance. The voltage divider circuit is not recommended for use in the high current application as it has a low output current and lower efficiency.
LM7805 12v to 5v converter:
A voltage regulator 12v to 5v dc can also be implemented with an LM7805 linear voltage converter. It is used for (10mA to 1 Amp ) medium current to the high current application circuits.
It has the feature of maintaining the same output current as applied at the input end.
The input capacitor and an output capacitor is to be externally connected to the IC 7805, these capacitor acts as ripple reducer if it is present in the source power supply according to the datasheet. The heat sink is a must because the voltage drop of 7 volts is converted to heat though the Heat-Sink.
If you don’t attach a heatsink it can destroy the IC while applying it in high current circuits and remain with a damaged IC. The source voltage must be >2.5V more than the required regulated output dc voltage.
One 12v battery/ 12V adopter power source, 10uF capacitor, 1uF capacitor, IC LM7805, Heat-sink, some connecting wires, and a soldering iron (for soldering).
For getting a steady and zero ripple output voltage, the linear voltage regulators IC’s are used. These are the integrated circuits that are made for linear voltage conversion and regulation are often termed as a step-down transformer ICs. Let’s discuss 12v to 5v DC converter using IC 7805.
The transformer IC 7805 is part of the LM78xx series of DC converter ICs. It is a linear step-down transformer IC. The digits ‘xx‘ represents the value of the regulated o/p in volts. The IC7805 gives 5V DC as the digit ‘xx‘ showing (05) which is 5 volts. The output will be constant at 5 Volts for all value of the input in 6.5volts to 35 volts. (refer to datasheet)
Pin number 1 is the source supply terminal. Pin number 2 is the ground terminal. Pin number 3 is the output voltage terminal.
Click here for simple5v to 3.3 v converter circuit and modules
Check this video for reference: (input capacitor is not used but it is recommended), also values of the capacitor may be different as available and depending on the area of application)
LM317 12v to 5v converter:
A 12v to 5v dc converter can also be implemented with an LM317 voltage regulator IC. It is very useful in mid to high current applications(1 Amp and more). It is also found in desktop computers as voltage surge protection circuits.
This circuit also has the capacity to give the same output current as taken from an unregulated source.
Generally, LM317 is a variable power supply IC that can provide a variable but regulated output voltage from 1.25 Volts to 37 volts depending on “Vref” (reference voltage), the voltage on pin number 1 (Adj.) which is reference voltage taken from a potentiometer. Adj. is voltage for adjustment. Below is a voltage divider circuit build using LM317 gives a fixed voltage of 5V at pin number 2.
It is suggested to connect the input capacitor ‘Cin’ to work (as well as at output ‘recommended’). A heat sink as shown in the below figure must be there to dissipate heat (kind of extra i/p potential).
The properly connected heat-ink is a must otherwise it can destroy the IC317. The input voltage must be 1.5V or more than the required output voltage.
Check here online LM317 resistor calculator tool to directly find the values of resistors.
One 12v battery/ 12V power supply, a 1.6k resistor, 4.7K resistor, 10uF capacitor, 1uF capacitor, IC LM317, a Heat-sink, some connecting wires, breadboard if doing experimentally and a soldering iron.
The LM317 is an adjustable voltage regulator IC capable of supplying more than 1.0 Ampere of current with a wide range of o/p voltage from 1.25 Volts to 37 Volts. Its regulation is a little bit better than other fixed voltage-regulator IC like LM7805, 7806, 7808, 7810 …
The formula for the output voltage of the 12v to 5v converter using LM317 is written above. It gives approximate value “Vo” when R2 and R1 are chosen to correctly to satisfy the formula. Put any standard value of either of the resistor (higher value of the resistor is recommended to reduce power loss), then substitute the value of required output voltage in the given formula to find the value of another resistor.
The below image showing Voltage regulator IC without Heat-Sink and with a heat-sink. Sometimes heat-sinks are sold separately. Please ensure to connect heat-sink properly with conducting paste applied for high current applications.
12v to 5v converter using a voltage divider:
Here is the 12v to 5v dc converter circuit for low current applications (< 70 mA), mainly for taking reference signal/ voltage and in a small current draining circuit like an LED indicator.
You can run two LEDs in series across the resistor R2 while taking input from 12V lead-acid battery or a 12v adapter as an input.
One 12v battery, 1.8k resistor, 1.3k resistor, connecting wires.
This circuit is a voltage divider schematic. You can design it for the required ‘output voltage’ by using this formula:
Here, Vout is the output voltage taken across resistor R2. Vin is the input voltage to be step down. Choose the standard resistor value (greater than 1K Ohm) of anyone resistance and solve for the other one. Then choose the standard value nearest to the obtained value of the resistor.
12v to 5v converter using zener diode:
The schematic circuit shown below is for medium current circuits, it is useful for (1-70mA) medium current draining circuit eg. light emitting diode indicators, driver circuits, low voltage transistor operations, and many more.
You can use this step-down 12v to 5v converter DC circuit in combination with another circuit across the output of zener diode (with a 12volt battery as an input). Approximately 5V is obtained across a zener diode.
A load resistor or output circuit is a must at output end while implementing or testing it in a circuit to prevent zener diode from getting burn.
One 12v battery, 100-ohm resistor (higher value is recommended), 5.1V zener diode (greater than 1W), some connecting wire, and soldering iron for permanent joints.
This is a very common circuit of zener diode as a voltage regulator circuit. You can regulate o/p voltage according to the application by changing diode and the series resistor (Rs).
Step by step Zener voltage regulator method:
Design a ‘Vout’ stabilized power supply to produce from an unregulated DC power supply source ‘Vs’. The maximum power rating PZ of the zener diode is in Watts. Using the zener diode and calculate using the following formulas:
The maximum current flowing through the zener diode.
Id = (Watts / Voltage)
The minimum value of the RS series resistor.
Rs = (Vs – Vz) / Iz
The load current IL if a load resistor of 1kΩ is connected across the zener diode.
IL = VZ / RL
The zener current IZ at full load.
Iz = Is – IL
IL = current through Load
Is = current through Rs series resistor
Iz = current though zener diode (check datasheets or assume 10- 20mA if not given)
Vo =VR =Vz = zener voltage = output voltage
RL = Load resistor
Check 3.7v to 5v boost converter circuit with various ICs
*Before final application with 12v to 5v converter circuit in your projects, verify and confirm the output volts to what you designed for. The value of current mentioned in the article is for reference only, as the value of current changes according to the impedance of the circuit at the output end.