📋 Overview
The LM2596 CC/CV Step-Down Buck Converter Module is a compact, adjustable DC-DC power supply that provides both Constant Voltage (CV) and Constant Current (CC) output regulation. It accepts an input voltage from 7V to 35V and delivers an adjustable output from 1.25V to 30V at up to 3A. Two separate potentiometers let you independently set the maximum output voltage and the maximum output current, while a third potentiometer sets the charge-complete threshold current.
This dual-mode capability makes it far more versatile than a standard voltage-only buck converter. In CV mode, the module behaves like a traditional voltage regulator — it holds the output at a set voltage regardless of load current (up to the CC limit). In CC mode, the module limits the output current to your set value, allowing the voltage to drop as needed. The module automatically transitions between modes depending on load conditions.
Three on-board LED indicators show you which mode the module is operating in at a glance — making it especially useful for battery charging applications where you need to know when charging is complete.
⚠️ Important: This module has no input reverse polarity protection. Connecting the input backwards will permanently damage the module. Always double-check polarity before applying power. The output voltage must always be set lower than the input voltage, with a minimum difference of approximately 2V.
💡 What Is CC/CV and Why Does It Matter?
Most basic power supply modules only offer Constant Voltage (CV) — they hold the output at a fixed voltage and let the load draw whatever current it needs (up to the module's maximum). This works great for powering microcontrollers, logic circuits, and other devices that regulate their own current draw.
But some loads need Constant Current (CC) — a fixed, controlled current regardless of voltage. And some applications need both modes working together, automatically switching between them depending on conditions. That's what a CC/CV supply does.
How CC/CV Works Together
Think of it like a two-rule system:
- Rule 1 (CV): "Never exceed this voltage."
- Rule 2 (CC): "Never exceed this current."
The module enforces whichever rule is being hit first. If the load is light and the current is below your CC setting, the module operates in CV mode and holds the voltage steady. If the load increases and tries to draw more current than your CC setting, the module switches to CC mode — it holds the current steady and lets the voltage drop as needed.
When Would You Want CC/CV Control?
Here are the most common applications where CC/CV control is essential or highly beneficial:
1. LED and Laser Diode Driving
LEDs and laser diodes are current-driven devices. Their brightness is determined by the current flowing through them, not the voltage across them. If you apply a fixed voltage to an LED without current limiting, the LED will draw increasing current as it heats up (a phenomenon called thermal runaway), eventually destroying itself. A CC supply solves this by fixing the current at a safe level. The CV setting acts as a safety cap — if the LED is disconnected or the circuit opens, the voltage won't spike beyond your set maximum.
2. Battery Charging
Rechargeable batteries (lithium-ion, NiMH, NiCd, lead-acid) require a specific charging profile. Most use a CC/CV charging algorithm:
- Phase 1 (CC): The charger pushes a constant current into the battery until the battery voltage rises to the target charge voltage.
- Phase 2 (CV): The charger holds the voltage constant at the target level while the current gradually tapers off as the battery reaches full charge.
This CC/CV module handles this transition automatically. The blue CH LED illuminates when the charging current drops below the threshold you set with the third potentiometer, indicating the battery is fully charged.
3. Electroplating and Anodizing
Electroplating (depositing a thin layer of metal onto an object) and anodizing (creating a protective oxide layer on aluminum) both require a controlled, constant current through an electrolyte solution. The voltage across the solution varies depending on the chemistry, temperature, and electrode spacing, but the current must remain steady for uniform coating thickness. A CC/CV supply is ideal for small-scale hobby electroplating setups.
4. Electrolysis and Hydrogen Generation
Electrolysis (splitting water into hydrogen and oxygen, or other electrochemical processes) requires a controlled current through the electrolyte. The voltage varies with electrode condition and electrolyte concentration, but the reaction rate is proportional to current. CC mode ensures a consistent reaction rate.
5. Thermoelectric Cooler (Peltier) Modules
Peltier/TEC modules are often driven with a controlled current to manage cooling power. Running them at too high a current wastes energy and generates excess heat on the hot side. CC mode lets you dial in the optimal operating current for your cooling application.
6. Solenoid and Electromagnet Control
The magnetic field strength of a solenoid or electromagnet is proportional to current, not voltage. If you need a consistent magnetic force regardless of coil temperature (which changes resistance), CC mode maintains a steady current and therefore a steady magnetic field.
7. Lab and Bench Testing
When testing circuits or components on a workbench, CC mode acts as a safety net. You can set a current limit so that if something shorts or malfunctions, the module limits the current to a safe level instead of dumping maximum current into the fault. This protects both your circuit under test and the power supply.
📊 Specifications
| Module Type | DC-DC Step-Down (Buck) Converter with CC/CV |
| Regulator IC | LM2596 |
| Input Voltage | 7V – 35V DC |
| Output Voltage | 1.25V – 30V DC (adjustable via CV potentiometer) |
| Max Output Current | 3A (adjustable via CC potentiometer, 0A – 3A) |
| Output Power | 15W (natural cooling) / 25W (with heatsink) |
| Conversion Efficiency | Up to 92% (higher at higher output voltages) |
| Optimal Efficiency | Output voltage ≈ 80% of input voltage |
| Minimum Voltage Differential | ~2V (input must be at least 2V higher than output) |
| Load Regulation | ±1% |
| Voltage Regulation | ±0.5% |
| Dynamic Response | 5% / 200µs |
| No-Load Current | Typical 10mA (12V input to 4.2V output) |
| Full Load Temperature Rise | 45°C |
| Output Short Circuit Protection | Yes (limits to CC setting) |
| Input Reverse Polarity Protection | No — observe correct polarity |
| Potentiometer Direction | Clockwise = increase, Counterclockwise = decrease |
| Operating Temperature | -40°C to +85°C |
| Connection Mode | Soldered |
| Board Dimensions | Approx. 47 × 23 × 14 mm (1.85 × 0.91 × 0.55 inches) L × W × H (including potentiometers) |
📌 On-Board Controls and Indicators
Potentiometers
This module has three potentiometers (small adjustment screws on the board). Each controls a different parameter:
| Potentiometer | Label | Function |
|---|---|---|
| 1 | CV (Constant Voltage) | Sets the maximum output voltage (1.25V – 30V) |
| 2 | CC (Constant Current) | Sets the maximum output current (0A – 3A) |
| 3 | CH (Charge Complete) | Sets the current threshold at which the blue "fully charged" LED turns on. Default is 0.1× the CC setting. |
All three potentiometers follow the same convention: clockwise increases the value, counterclockwise decreases it.
LED Indicators
Three LEDs on the board tell you which mode the module is currently operating in:
| LED | Color | Label | Meaning |
|---|---|---|---|
| 1 | Red | CC/CV | Module is operating in Constant Current (CC) mode — the load is drawing the maximum set current |
| 2 | Red | OK | Module is operating in Constant Voltage (CV) mode — the output is at the set voltage and current is below the CC limit |
| 3 | Blue | CH | Fully charged — the charging current has dropped below the threshold set by the CH potentiometer |
📌 Pin / Pad Descriptions
The module has four solder pads for input and output connections:
| Pad | Label | Description |
|---|---|---|
| 1 | IN+ | Positive input — connect to the positive terminal of your DC power source (7V – 35V) |
| 2 | IN− | Negative input (ground) — connect to the negative terminal of your DC power source |
| 3 | OUT+ | Positive output — connect to the positive terminal of your load, battery, or LED |
| 4 | OUT− | Negative output (ground) — connect to the negative terminal of your load, battery, or LED |
🚀 Getting Started
Before connecting any load, you need to set both the output voltage (CV) and the output current limit (CC). This is a two-step calibration process that requires a multimeter.
What You'll Need
- A DC power source (7V – 35V) — battery, wall adapter, or bench supply
- A digital multimeter with a 10A current range
- A small screwdriver (Phillips or flathead) for the potentiometers
- Hook-up wire or jumper wires
- Soldering iron and solder (connections are soldered, not screw terminals)
Step 1: Set the Output Voltage (CV)
- Connect your DC power source to IN+ and IN−. Double-check polarity.
- Leave the output disconnected (open circuit — nothing connected to OUT+ and OUT−).
- Power on the input supply.
- Place your multimeter probes on OUT+ (red) and OUT− (black), set to DC voltage.
- Turn the CV potentiometer until the multimeter reads your desired output voltage.
Step 2: Set the Output Current Limit (CC)
- Switch your multimeter to the 10A DC current range.
- Short-circuit the output — connect a wire (or your multimeter leads in current mode) directly between OUT+ and OUT−.
- The multimeter will now display the short-circuit current, which is the CC limit.
- Turn the CC potentiometer until the multimeter reads your desired maximum current.
- Remove the short circuit.
⚠️ Important: When measuring short-circuit current, make sure your multimeter is set to the 10A range and the leads are in the correct jacks (most multimeters have a separate 10A jack). Using the wrong range or jack can blow the multimeter's internal fuse.
Step 3: Set the Charge-Complete Threshold (Optional)
If you're using this module as a battery charger, the third potentiometer (CH) sets the current level at which the blue "fully charged" LED turns on. The default is approximately 0.1× the CC setting (e.g., if CC is set to 1A, the blue LED lights when current drops below ~100mA). Adjust this potentiometer if you need a different threshold.
Step 4: Connect Your Load
Once both CV and CC are set, connect your load (battery, LED, device, etc.) to OUT+ and OUT−. Watch the LED indicators to confirm the module is operating in the expected mode.
🔧 Application Guides
Using the Module as a Battery Charger
This module can charge lithium-ion, lithium-polymer, NiMH, NiCd, and lead-acid batteries using a CC/CV charging profile. Here's how to set it up:
- Determine your battery's charge voltage and current. Check the battery datasheet or label. For example, a single lithium-ion cell charges to 4.2V at a typical rate of 0.5C to 1C (where C is the battery capacity in Ah).
- Set the CV voltage to the battery's target charge voltage (e.g., 4.2V for a single Li-ion cell, 8.4V for a 2S pack, 12.6V for a 3S pack).
- Set the CC current to the battery's recommended charge current (e.g., 1A for a 1000mAh battery at 1C).
- Adjust the CH threshold if desired. The default (0.1× CC) works well for most lithium-ion charging — the blue LED will light when the taper current drops to about 10% of the initial charge current, indicating the battery is nearly full.
- Connect the battery to OUT+ and OUT−. The red CC/CV LED will light during the constant-current phase. As the battery voltage rises to the CV setting, the module transitions to constant-voltage mode (red OK LED). When the current tapers below the CH threshold, the blue CH LED lights up.
⚠️ Important: This module provides basic CC/CV charging. It does not include cell balancing (for multi-cell packs), temperature monitoring, or under-voltage cutoff. For lithium batteries, always monitor the charging process and do not leave unattended. For multi-cell lithium packs, use a proper balance charger or add a BMS (Battery Management System) board.
Common Battery Charge Settings
| Battery Type | CV Setting | Typical CC Setting |
|---|---|---|
| Single Li-ion / LiPo (3.7V nominal) | 4.2V | 0.5C – 1C (e.g., 1A for 1000mAh) |
| 2S Li-ion / LiPo (7.4V nominal) | 8.4V | 0.5C – 1C |
| 3S Li-ion / LiPo (11.1V nominal) | 12.6V | 0.5C – 1C |
| Single LiFePO4 (3.2V nominal) | 3.6V | 0.5C – 1C |
| 12V Lead-Acid (6-cell) | 14.4V (bulk) / 13.8V (float) | 0.1C – 0.3C |
| 6V Lead-Acid (3-cell) | 7.2V (bulk) / 6.9V (float) | 0.1C – 0.3C |
| NiMH / NiCd (per cell) | 1.4V – 1.5V per cell | 0.1C – 0.5C |
Using the Module as an LED Constant Current Driver
LEDs should be driven with a constant current for consistent brightness and long life. Here's how:
- Determine your LED's operating current and maximum forward voltage. Check the LED datasheet. For example, a typical 1W high-power LED runs at 350mA with a forward voltage of 3.0V–3.4V.
- Set the CV voltage to the LED's maximum forward voltage (or slightly above). This acts as a voltage safety cap — if the LED is disconnected, the output won't exceed this voltage.
- Set the CC current to the LED's rated operating current (e.g., 350mA for a 1W LED, 700mA for a 3W LED).
- Connect the LED to OUT+ (anode) and OUT− (cathode). The module will operate in CC mode, delivering a steady current to the LED.
💡 Tip: You can drive multiple LEDs in series as long as the total forward voltage of all LEDs combined is at least 2V less than your input voltage. For example, with a 12V input, you could drive three 3V LEDs in series (total 9V forward voltage) at a constant current. Set CV to about 10V and CC to your desired LED current.
Using the Module as a Lab/Bench Power Supply
The CC/CV capability makes this module useful as a simple adjustable bench supply with built-in current limiting:
- Set the CV voltage to your desired working voltage.
- Set the CC current to a safe maximum for your circuit under test. This acts as a safety net — if something shorts, the module limits current to your CC setting instead of dumping maximum current into the fault.
- Connect your circuit and test. The OK LED (CV mode) should be lit during normal operation. If the CC/CV LED lights up, your circuit is hitting the current limit.
🔋 Thermal Management
The LM2596 is rated for up to 3A, but heat generation depends on the voltage differential, current draw, and ambient temperature:
- Up to 15W output: The module can operate with natural air cooling (no heatsink required).
- 15W to 25W output: A heatsink is required on the LM2596 IC. Without one, the IC will overheat and may trigger thermal shutdown.
- Above 25W: Exceeds the module's rated capacity. Use a higher-rated converter.
Calculating Output Power
Output power = Output Voltage × Output Current. For example:
- 5V × 2A = 10W → No heatsink needed
- 12V × 2A = 24W → Heatsink required
- 5V × 3A = 15W → Borderline, heatsink recommended for continuous use
Tips for Managing Heat
- Add a small adhesive aluminum heatsink to the LM2596 IC (the large 5-pin chip) for any sustained load above 15W.
- Ensure adequate airflow — don't seal the module in a tight enclosure without ventilation.
- For best efficiency (and least heat), keep the output voltage at approximately 80% of the input voltage.
- If ambient temperature exceeds 40°C, derate the output power or add active cooling.
⚠️ Note: A heatsink is not included with this module. If you plan to operate above 15W or in elevated ambient temperatures, you will need to supply a heatsink separately.
🔌 Wiring Examples
Example 1: Charging a Single 18650 Li-ion Cell from a 12V Adapter
| Connection | From | To |
|---|---|---|
| Power In (+) | 12V adapter positive | Module IN+ |
| Power In (−) | 12V adapter negative | Module IN− |
| Power Out (+) | Module OUT+ | Battery positive terminal |
| Power Out (−) | Module OUT− | Battery negative terminal |
Settings: CV = 4.20V, CC = 0.5A–1A (depending on battery capacity), CH = default (0.1× CC).
Example 2: Driving a 3W High-Power LED from a 24V Supply
| Connection | From | To |
|---|---|---|
| Power In (+) | 24V supply positive | Module IN+ |
| Power In (−) | 24V supply negative | Module IN− |
| Power Out (+) | Module OUT+ | LED anode (+) |
| Power Out (−) | Module OUT− | LED cathode (−) |
Settings: CV = 3.6V (slightly above LED max forward voltage), CC = 700mA (rated LED current).
Example 3: Bench Supply with Current-Limited Output
| Connection | From | To |
|---|---|---|
| Power In (+) | 24V bench adapter positive | Module IN+ |
| Power In (−) | 24V bench adapter negative | Module IN− |
| Power Out (+) | Module OUT+ | Circuit under test (+) |
| Power Out (−) | Module OUT− | Circuit under test (−) |
Settings: CV = your desired test voltage, CC = a safe current limit for your circuit (e.g., 500mA as a safety cap).
⚠️ Important Notes & Safety
- No input reverse polarity protection. Connecting the input backwards will permanently damage the module. If you're concerned about accidental reversal, add a series diode (such as a 1N5822 Schottky diode) on the IN+ line. Note that the diode will drop approximately 0.3V–0.5V from your input voltage.
- Always set CV and CC before connecting your load. The module may power up with unknown potentiometer settings. Connecting a sensitive device or battery without verifying the output first can cause damage.
- Do not exceed 35V input. The LM2596 on this module is rated for 35V maximum input (note: this is lower than the 40V rating on the voltage-only version).
- Minimum input voltage is 7V (higher than the 4V minimum on the voltage-only version).
- Minimum voltage differential is ~2V. The input must be at least 2V higher than the desired output for proper regulation.
- Output short circuit protection is provided via CC mode. If the output is shorted, the module limits current to whatever the CC potentiometer is set to. This protects the module but means a short circuit will continuously draw current at the CC setting — it does not shut off.
- This module does not include cell balancing. When charging multi-cell lithium battery packs, always use a BMS (Battery Management System) or balance charger to prevent individual cells from overcharging.
- This module does not include a built-in voltage/current display. You must use an external multimeter to read output voltage and current.
- Heatsink not included. For output power above 15W or ambient temperatures above 40°C, add a heatsink to the LM2596 IC.
- Soldered connections only. This module does not have screw terminals — you'll need to solder your wires to the pads.
🛠️ Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| No output voltage | No input power, reversed polarity, or module damaged | Verify input voltage and polarity with a multimeter. If polarity was reversed, the module is likely damaged and must be replaced. |
| Output voltage won't reach desired level | Input voltage too low (less than output + 2V) | Increase input voltage so it is at least 2V above your desired output. |
| Output voltage drops under load | Load is drawing more current than CC setting, or module is at its power limit | Check if the CC/CV LED is lit (CC mode). Increase the CC setting if appropriate, or reduce the load. Check that output power doesn't exceed 15W (25W with heatsink). |
| CC/CV LED is always on | CC limit is set too low for the load | Increase the CC potentiometer setting, or reduce the load current. |
| Module gets very hot | High power output or large voltage differential | Add a heatsink. Reduce current draw. Ensure output power is within rated limits (15W without heatsink, 25W with heatsink). For best efficiency, keep output voltage at ~80% of input voltage. |
| Blue CH LED never turns on (battery charging) | CH threshold set too low, or battery not reaching full charge | Adjust the CH potentiometer clockwise to increase the threshold. Verify the battery is actually reaching the CV voltage. Check that the CV setting matches the battery's target charge voltage. |
| Blue CH LED turns on too early | CH threshold set too high | Turn the CH potentiometer counterclockwise to lower the threshold. |
| LED flickers or is dim | CC current set too low, or CV voltage set below LED forward voltage | Increase CC to the LED's rated current. Ensure CV is set at or slightly above the LED's maximum forward voltage. |
| Potentiometer doesn't seem to change anything | Multi-turn potentiometer needs many rotations | Keep turning — these potentiometers may require many full rotations to sweep the full range. |
📦 What's in the Box
- 1× LM2596 CC/CV DC-DC Step-Down Buck Converter Module
Heatsink, multimeter, wires, screwdriver, and power source are not included.
🏪 Where to Buy the LM2596 CC/CV Module
This module is available at Envistia Mall.
- 📦 Fast US Shipping
- 🔄 Hassle-Free Returns
- 📧 Responsive Customer Support
📚 Additional Resources
- LM2596 Module with Constant Voltage Control (no Constant Current Control): LM2596 1.25V - 35V Step Down Converter Module
- Check out our other Buck Converter Modules at Envistia Mall — Models with adjustable output voltage, higher current, and built-in digital voltmeters.
- LM2596 CC/CV Module Schematic (PDF)
- LM2596 Datasheet (Texas Instruments)
- Video: LM2596 CC/CV module tutorial on Youtube:
This guide is provided by Envistia Mall for educational and technical reference purposes. The manufacturer and Envistia LLC (dba Envistia Mall) are not responsible for any damages or losses resulting from the use of this product. Always follow proper electrical safety practices when working with electronic components. Specifications are based on manufacturer data and are subject to change without notice.