Powerful Voltage and Current adjustable Power Supply Circuit
Build a powerful voltage and current adjustable power supply circuit. Step-by-step guide with components, working principle, schematic, and construction tips.
What Is a Voltage and Current Adjustable Power Supply Circuit?
An Adjustable power supply circuit is an electronic component that enables users to regulate the output voltage and current depending on their requirements. It is frequently applied to power microcontrollers, LEDs, motors, and other electronics in a safe way in laboratories, electronics workshops, and also in hobbyist projects.
charger with voltage cutoff 12v
A 12V auto cut-off battery charger is a charging circuit that provides a current flow to a 12V lead-acid or SLA battery and switches and cuts off to float mode when the battery reaches the predetermined full-charge voltage (usually 13.6–14.4V depending on the battery type). This is normally built with a voltage-sensing comparator (LM324/LM358), an adjustable reference (zener or precision reference), a switching element (MOSFET or relay) to prevent charging, an indicator, and a current-limiting resistor or constant-current stage. Newer models introduce temperature compensation and soft start to increase the life of the battery. This charger can avoid excessive charge, gassing, and minimize maintenance- it can be used with car batteries, solar battery banks, UPS, and small off-grid systems. The ability to select a proper transformer/adapter, heat dissipation, and protection with fusing is the warranty for safe and reliable functioning.
Work / Installation (Inputs → Outputs)
Input: AC mains → transformer/SMPS → rectifier & filter → current limit stage → comparator control → switching device → battery.
- AC mains (or DC adapter) is stepped to ~15–18V AC (or supplied by suitable SMPS).
- Rectify (bridge) and filter to obtain DC (~18–20V unloaded).
- A current-limiter (resistor, or better: constant current regulator / CC stage) controls charge current (e.g., 0.1C–0.3C).
- A voltage-sensing comparator monitors battery voltage; reference set to cutoff (e.g., 14.4V for lead-acid).
- When measured voltage ≥ cutoff, comparator drives MOSFET/relay to disconnect charge or switch to float-mode regulator (~13.6V).
- Indicators (LEDs) show CHARGING / FULL; optional reverse polarity protection and fuse on input.
Output: Battery receives safe, limited-current charge and is automatically disconnected or held at float voltage when full.
Testing & Final Adjustments
Check no-load voltages. Before connecting a battery, check rectified DC no-load output voltages: measure rectified DC, and make the comparator reference adjustable. Install the fit input fuse and utilize a bench power supply/current-limited source during initial tests. Connect a discharged battery and measure the current of charge: This must be within the specifications (e.g.,1 3 A at charger rating). Watch the increasing voltage of the battery. When it goes to the cutoff setpoint (adjustable pot), be sure that the MOSFET/relay closes and the charging current is reduced to almost zero or floats. Characteristics of thermal behavior of MOSFET/heatsink with prolonged charging. Test reverse polarity and short-circuit. To be reliable in the long term, test at varying temperatures (or add a temp sensor) and vary the cutoff of battery chemistry: bulk charge =~14.4V, float = 13.6 -13.8V. And lastly, check LED indicators and safety cutouts (fuse, thermal limits). Label the charger and settings of the document.
Frequently Asked Questions - Powerful Voltage and Current adjustable Power Supply Circuit:
What is an adjustable power supply circuit?
A circuit that allows users to set output voltage and current for electronic loads.
Which IC is used for voltage regulation?
LM317 adjustable voltage regulator IC is commonly used.
How to limit output current?
Using a sense resistor and transistor to reduce current when exceeding the set limit.
Can it supply high current?
Yes, with a power transistor like TIP3055 or equivalent for high current output.
What voltage range is adjustable?
Typically from 1.25V to the maximum of the supply transformer minus regulator drop.
Can it be used for battery charging?
Yes, adjustable current and voltage make it ideal for charging batteries safely.
Do I need a heatsink?
Yes, LM317 and power transistor dissipate heat when supplying high current.
What input power is required?
AC mains via a step-down transformer to provide suitable DC after rectification.
Can I add an LED indicator?
Yes, for power ON indication.
Is it suitable for beginners?
Yes, basic knowledge of voltage regulators, transistors, and wiring is enough.
