12V to 24V converter.
There are many instances where we require 24V DC from a 12V source. I also once faced a situation like this when I decided to fit a small transistorised stereo amplifier which operated from 24V DC in my car. I found this circuit to be well enough for my application. This circuit can produce a steady 24C DC output and can deliver up to 800mA of output current. The circuit is basically a dc dc converter built around LM324 IC which is configured as an oscillator to produce the switching frequency and a transistor as the semiconductor switching element.
IC1 LM324 is the heart of this circuit. LM324 is a quad opamp and out of the four operational amplifiers inside it, only two is used here. IC1a, resistors R1, R2, R3 and C1 forms a oscillator which operates at around 500Hz. Resistor R2 and capacitor C1 is used to set the oscillator frequency. IC1b is wired as a comparator which compares the output voltage with a reference and feeds back a voltage to the oscillator stage. This is done for controlling the output voltage. Potential divider using preset R5 is connected to the non inverting pin of IC1. The output voltage is connected to the inverting input pin through a 100K resistor. Output of this comparator stage is fed to the non inverting input pin of IC1a through another 100K resistor. Output of the oscillator stage is connected to the base of transistor Q1 and resistor R7 is used for limiting the base current of Q1.
When the output of the oscillator stage is high, transistor Q1 will be switched ON and the current through the inductor L1 starts to increase. When the output of oscillator goes low, transistor Q1 will be switched OFF and now the only path for the inductor current is through diode D2, capacitor C3 and the load if any. The fly back diode D2 will be forward biased and the energy stored in the inductor during the ON state will be dumped into the capacitor. Diode D1 acts as a freewheeling diode.
An inductor will always try to oppose any variation in the current passing through it and this property of the inductor is utilized here. When charged it stores energy and when discharged it behaves like an energy source. The voltage it outputs during the discharge phase is proportional to the rate of change of current through it. As the switching frequency increases the induced emf (electro motive force) from the inductor also increases.
Circuit diagram of 12V to 24V DC DC converter.
For L1, I made 60 turns of 22SWG enamelled copper wire on Type No CS166060 Sendust core. The approximate dimensions of the core are as follows. Outer diameter=0.6 inch, inner diameter= 0.3 inch and height=0.25 inch.
Load current should not exceed 800mA.
IC1 must be mounted on a holder.
The circuit can be assembled on a perf board.
Preset R5 can be used to adjust the output voltage.
C1 is a polyester capacitor while C2 is ceramic.
Electrolytic capacitor C3 must be rated at least 50V.
Preset R5 must be of linear type.
R7 must be rated 0.5 watts.
Other Related Dc to Dc Converter Circuits List; Given Below:
1. 6V to 15V DC DC Converter – This is a simple but highly efficient voltage converter circuit designed using LM2585 IC – which is a monolithic integrated converter suitable for making boost converter, forward converter or other similar applications. LM2585 is wired as a boost converter in this circuit and it can source up to maximum 3 Ampere current .
2. 12V to 120V Dc to Dc Converter – This circuit is made of two stages – first stage consists of an inverter and the second stage is a rectifier and filter. This circuit is designed using two IC’s -one is NE 555 which is wired to an astable multivibrator that operates at 100Hz frequency and the second one is CD4013 which is a CMOS dual D-Flip flop.
3. 5V Boost Converter – This is a 5Volt boost converter circuit designed using IC LTC 3440. This IC can be operated from an input voltage above,below or equal to the output voltage and it can deliver an output current of 600mA and a steady 5 Volts Dc output.
4. Step Up Voltage Converter - This circuit is actually a 3Volt to 8Volt dc dc converter designed using IC LM 2700 which is a step up switching converter.In this particular circuit LM 2700 is wired to produce 8volts from 3 volts at a switching frequency of 600 Hz.
5. 3V to 5V Converter Circuit – This voltage converter circuit is designed using two CMOS IC MAX660 and MAX 667.; where MAX 660 acts as the voltage converter and MAX 667 acts as the positive voltage regulator which keeps the output at steady 5 volts.
6. 6V to 12V Voltage Converter – This might be quiet an interesting circuit for you because this voltage converter is built around an IC TDA2003 – which is basically an audio amplifier IC. The output voltage is stabilized in this circuit using a voltage limiter and a zener diode.
7. 12V from USB – This is another circuit that may generate curiosity in you. This is 5Volt to 12Volt converter, but the source 5Volt is taken from a USB port. This circuit is designed using the constant current,constant voltage boost converter IC LT1618. This circuit is quiet interesting and has many applications in USB powered systems.
8. Positive to Negative Voltage Converter – Its actually a simple circuit that shows how to obtain a negative supply from a positive one. Circuit is designed using NE 555 IC which is wired as an astable multivibrator that operates at 1Khz frequency. A dual supply can be simulated using this same circuit by making use of both positive and negative supply.
9. 12 Volt Boost Converter – This is a simple boost converter circuit that can effectively produce 12Volt DC output. This circuit is designed using LM 2698 IC from National semiconductors, which is a general boost converter IC that has an output range of 2.2 volts to 17 volts.
I have listed almost all dc dc voltage converter circuits we have till date. But we will continue publishing more related circuits in future – which you can check out using our Tag-Voltage Converter