The B3603 DC-DC Step-Down (Buck) Converter Module is a digitally controlled power supply module that reduces a higher DC input voltage (6V–40V) to a lower adjustable output voltage (0V–36V). It features precise constant voltage (CV) and constant current (CC) regulation, a built-in LED display for real-time monitoring of voltage, current, power, and capacity, and 10 programmable memory presets for storing frequently used settings.
This module is ideal for DIY bench power supplies, battery charging, LED driver applications, laboratory testing, and any project requiring a stable, adjustable DC output from a higher-voltage source.
📋 Specifications
| Parameter | Value |
|---|---|
| Input Voltage | 6V – 40V DC |
| Output Voltage | 0V – 36V DC (adjustable) |
| Output Current | 0A – 3A (adjustable) |
| Maximum Output Power | ~108W |
| Voltage Resolution | 0.01V (display and regulation) |
| Current Resolution | 0.001A (display and regulation) |
| Power Display Resolution | 0.001W |
| Capacity Display Resolution | 0.001Ah |
| Conversion Efficiency | Up to 92% |
| Output Ripple | ≤ 50mV |
| Switching Frequency | 150 KHz |
| Operating Temperature | -40°C to +85°C |
| Short Circuit Protection | Yes (constant current limiting) |
| Input Reverse Polarity Protection | No (add external diode if needed) |
| Connection Method | Screw terminals |
| Dimensions | 2.6 x 1.97 x 0.83 inches (66 x 50 x 21 mm) |
| Weight | 1.5 oz (43 g) |
📌 Module Layout
The B3603 module features the following physical components:
- Input Terminals (IN+ / IN−): Screw terminals for connecting the DC input power source.
- Output Terminals (OUT+ / OUT−): Screw terminals for connecting the load.
- 4-Digit LED Display: Shows voltage, current, power, and capacity values in real time.
-
Three Indicator LEDs:
- OUT – Illuminates when the output is active.
- CV – Illuminates when operating in Constant Voltage mode.
- CC – Illuminates when operating in Constant Current mode.
-
Four Push Buttons:
- SET – Switches between voltage/current settings; saves changed values.
- ▲ (Up) – Increases the displayed value. Short press for fine adjustment; long press for rapid adjustment.
- ▼ (Down) – Decreases the displayed value. Short press for fine adjustment; long press for rapid adjustment.
- OK – Enables/disables output; switches display parameters during output; accesses special functions.
🔌 Wiring and Installation
What You'll Need
- A DC power source rated between 6V and 40V (e.g., power adapter, battery, or bench supply)
- Appropriate gauge wire for your current requirements (18 AWG or heavier recommended for 3A)
- Your load (device, circuit, battery, LEDs, etc.)
- (Optional) A diode rated for your input voltage/current for reverse polarity protection
- (Optional) A heatsink or small fan for loads exceeding 2A
Step-by-Step Wiring
- Disconnect all power before making any connections.
-
Connect the input power source:
- Connect the positive (+) wire from your DC source to the IN+ screw terminal.
- Connect the negative (−) wire from your DC source to the IN− screw terminal.
-
Connect the load:
- Connect the positive (+) wire to the OUT+ screw terminal.
- Connect the negative (−) wire to the OUT− screw terminal.
- Double-check all connections for correct polarity before applying power.
⚠️ CRITICAL: This module does NOT have built-in reverse polarity protection. Reversing the input connections will permanently damage the module. If reverse connection is a risk in your application, install a series diode (e.g., 1N5822 Schottky diode) on the positive input line.
⚙️ Operating the Module
Basic Operation
Step 1: Power On and Set Voltage
- Apply power to the input terminals. The LED display will show the current voltage setting in the format 00.00 (volts).
- Use the ▲ and ▼ buttons to adjust the output voltage to your desired value.
- Short press = fine adjustment (0.01V per step)
- Long press = rapid adjustment
- Press SET to confirm. If the value was changed, the display will briefly show "✱" to confirm the voltage has been saved.
Step 2: Set Current Limit
- Press SET to switch to the current display, shown in the format 0.000 (amps).
- Use the ▲ and ▼ buttons to set your desired current limit.
- Short press = fine adjustment (0.001A per step)
- Long press = rapid adjustment
- Press SET to confirm. The display will briefly show "✱" if the value was changed and saved.
Step 3: Enable Output
- Press the OK button to turn on the output. The OUT LED will illuminate.
- The module will operate in CV mode (CV LED lit) unless the load draws more current than the set limit, at which point it will switch to CC mode (CC LED lit).
Step 4: Monitor Parameters During Output
While the output is active:
- Short press OK to cycle through display parameters: Voltage → Current → Power → Capacity
- Long press OK (3 seconds) to enable automatic cycling through all parameters
- Long press OK again to disable automatic cycling
Step 5: Adjust Output On-the-Fly
While the output is active:
- When the display shows voltage: Use ▲/▼ to adjust output voltage in real time.
- When the display shows current: Use ▲/▼ to adjust the current limit in real time.
- When the display shows power or capacity: The ▲/▼ buttons are inactive.
Step 6: Disable Output
- Press SET while the output is active to turn off the output.
📡 Understanding the Display
| Display Format | Parameter | Unit | Examples |
|---|---|---|---|
| 00.00 | Voltage | Volts (V) | 12.00 = 12.00V |
| 0.000 | Current | Amps (A) | 1.500 = 1.500A |
| P_.___ | Power | Watts (W) | P.123 = 0.123W, P1.23 = 1.23W, P12.3 = 12.3W, P102. = 102W |
| C_.___ | Capacity | Amp-hours (Ah) | C.123 = 0.123Ah, C1.23 = 1.23Ah, C12.3 = 12.3Ah, C123. = 123Ah |
Note: The decimal point position shifts automatically based on the magnitude of the power and capacity values.
🚀 Advanced Features (Special Functions)
The B3603 includes three special functions that are disabled by default. You can enable or disable them individually.
Accessing Special Functions
- Disconnect power from the module.
- Press and hold the OK button, then reconnect power while continuing to hold OK.
- The display will cycle through "--0-", "--1-", and "--2-".
-
Release OK when the desired function number is displayed:
- Release on "--0-" → toggles Function 0
- Release on "--1-" → toggles Function 1
- Release on "--2-" → toggles Function 2
- The display will show:
- "--y-" = Function is now enabled
- "--n-" = Function is now disabled
Function 0: Auto-Output on Power-Up
When enabled, the module will automatically enable the output when power is applied, using the last saved voltage and current settings. This is useful for unattended or embedded applications where the module should begin operating immediately.
Function 1: Memory Presets and Power/Capacity Display
When enabled, this unlocks:
- 10 memory preset slots (0–9) for storing and recalling voltage/current combinations
- Power and capacity display in the parameter cycle
Saving a Preset
- With output off, press SET to navigate to the voltage setting. Set your desired voltage and press SET to save.
- Press SET to navigate to the current setting. Set your desired current and press SET to save.
- Press SET until the display shows "SA.-0" (Save to slot 0).
- Use ▲/▼ to select the desired slot number (0–9), e.g., "SA.-1".
- Press OK to save the current voltage and current values to that slot.
Recalling a Preset
- With output off, press SET until the display shows "Lo.-0" (Load from slot 0).
- Use ▲/▼ to select the desired slot number (0–9), e.g., "Lo.-1".
- Press OK to load the stored voltage and current values from that slot.
Example: To store 10V / 1.5A in slot 1: Set voltage to 10.00V → SET → Set current to 1.500A → SET → Navigate to SA.-1 → OK. To recall: Navigate to Lo.-1 → OK.
Function 2: Auto-Cycle Display During Output
When enabled, the display will automatically cycle through voltage, current, power, and capacity readings while the output is active. This provides hands-free monitoring without needing to press OK to switch parameters.
🔋 Thermal Management
| Output Current | Cooling Required |
|---|---|
| 0A – 2A | Natural convection (no additional cooling needed) |
| 2A – 3A | Active cooling recommended (heatsink and/or fan) |
Tip: For sustained operation at or near 3A, mount the module to an aluminum heatsink or direct a small 5V fan across the board. Overheating can cause reduced efficiency, thermal shutdown, or component damage.
⚠️ Safety Warnings and Important Notes
- No Reverse Polarity Protection: Reversing the input polarity will destroy the module. Always verify polarity before applying power. Consider adding an external Schottky diode for protection.
- Step-Down Only: The input voltage must be at least 1.5V higher than the desired output voltage. The module cannot boost voltage — it can only step down.
- Do Not Exceed Ratings: Do not exceed 40V input or 3A output. Operating beyond rated specifications may cause permanent damage.
- Secure Connections: Ensure all screw terminal connections are tight. Loose connections can cause arcing, heat buildup, and intermittent operation.
- Adequate Ventilation: When operating above 2A, ensure adequate airflow around the module.
- Isolated Output: The input and output share a common ground. If your application requires galvanic isolation, use an isolated DC-DC converter instead.
🎯 Common Applications
- DIY Bench Power Supply: Pair with a laptop adapter (19V–24V) for an adjustable lab supply with digital readout.
- Battery Charging: Use CC/CV mode to charge lithium-ion, lead-acid, or NiMH batteries with precise voltage and current control.
- LED Driver: Set the exact forward voltage and current limit for driving high-power LEDs safely.
- Embedded Systems Power: Provide regulated voltage rails for microcontrollers, sensors, and IoT devices from a higher-voltage bus.
- Solar Panel Regulation: Step down variable solar panel output to a stable voltage for charging or powering devices.
- Automotive Projects: Convert 12V/24V vehicle power to lower voltages for accessories and electronics.
🛠️ Troubleshooting
| Symptom | Possible Cause | Solution |
|---|---|---|
| Module does not power on | Input voltage below 6V or reversed polarity | Verify input is 6V–40V with correct polarity |
| Output voltage lower than set value | Input voltage too close to output voltage | Ensure input is at least 1.5V above desired output |
| Module overheats at high current | Insufficient cooling | Add heatsink and/or fan for loads above 2A |
| CC LED lights unexpectedly | Load is drawing more current than the set limit | Increase the current limit or reduce the load |
| Display shows erratic readings | Loose terminal connections or noisy input | Tighten all connections; add input capacitor if needed |
| Output does not turn on after power-up | Auto-output (Function 0) is disabled | Press OK to manually enable output, or enable Function 0 |
| Cannot access Save/Load presets | Function 1 is disabled | Enable Function 1 via the special function menu |
🛒 Where to Buy the B3603
You can purchase the B3603 Step-Down CC/CV Buck Converter Module directly from Envistia Mall:
B3603 3A 6-40V DC-DC Digital Control CV/CC Step-Down Converter →
📚 Resources & Downloads
Review: 3A 40V Digital Buck DC/DC Converter - It's more like a Bench PSU! by Julian Ilett 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.