Description
📝 Overview
The PN Labs Protect+ is a compact, high-performance DC power protection module designed to safeguard your electronics from overvoltage, undervoltage, overcurrent, reverse polarity, and reverse current faults.
It works by sitting between your power source and load, continuously monitoring voltage and current against independently adjustable thresholds and disconnecting the load the moment unsafe conditions are detected, helping prevent costly damage before it happens.
Over and undervoltage events trigger a temporary shutdown with automatic recovery once conditions normalize. Overcurrent events latch the module off until manually or electronically reset, giving you full control over when power is restored.
Built entirely in hardware with no microcontroller, the Protect+ delivers fast, reliable protection with up to 28 A of continuous current capacity across a 7–60 V operating range. Perfect for robotics, amateur radio setups, and other sensitive electronics.
✅ Key Features
- Adjustable Overvoltage & Undervoltage Protection (7–60 V): Set independent cutoff thresholds for both high and low voltage events. When input voltage exceeds or drops below the configured limits, Protect+ automatically disconnects the load and restores power once conditions normalize.
- Adjustable UVLO Hysteresis (0.9–5.2 V): Dial in the right amount of undervoltage hysteresis to account for cable voltage drop, which is especially important with long or thin wires at high currents. Prevents unwanted chatter and power blips during recovery.
- Latch-Off Overcurrent Protection: Adjustable current cutoff selectable from 2, 5, 10, 20, 30 A or No OCP with ±3% typical accuracy and a ~50 ms response time. On an overcurrent event, the module latches off and waits for a manual or electronic reset, giving you full control before power is restored.
- Reverse Polarity & Reverse Current Protection: Ideal diode functionality blocks reverse current flow with minimal voltage drop, protecting against incorrect wiring and enabling safe paralleling of power supplies, batteries, or solar panels (power ORing).
- Soft-Start Power-On: Output voltage ramps gradually at approximately 0.2 V/ms after the UVLO threshold is cleared, protecting against inrush and ensuring the protection thresholds are evaluated before full voltage is applied.
- 40 A Series Fuse: A secondary layer of hardware protection on-board, guarding against conditions that could cause the pass MOSFETs to fail.
- Power Switch Capability: Use a low-current mechanical or digital switch via the Sleep input to toggle high-power loads. No bulky high-current switches required.
- Opto-isolated Fault Output & Sleep Input: Optional isolated open-collector fault signal for system diagnostics, alerts, or automated shutdown logic. Isolated sleep input allows external control of the module’s on/off state.
- Compact & Mountable: 68 x 44 mm PCB with M2 mounting holes and XT60 connectors (with mating pair and heat shrink included) for easy installation.
⚙️ Protect+ Threshold Calculator
Enter your desired overvoltage cutoff, undervoltage cutoff, and UV hysteresis. The calculator returns the OV, UV, and HYS pad voltages to set with a multimeter, plus the full set of rising and falling thresholds derived from the Protect+ calibration equations.
Inputs
The UV cutoff has two voltages separated by the hysteresis: the trip off voltage where the module cuts power, and the recovery voltage where it restores power. Use the toggle below to choose which one you want to specify. The other is computed for you.
VInterpret the value above as:
Gap between the UV trip and recovery voltages. This prevents UVLO chatter under high currents when cable voltage drop causes the load voltage to oscillate around the trip point. Valid range is 0.45 to 5.68 V. Use around 2.5 V for typical loads, or more for long or thin wiring. Hysteresis is not adjustable on the overvoltage side.
VInput voltage at which the module trips off on a rising edge. OV hysteresis is fixed in hardware and shown in the results panel.
VResults
Pad voltages
Power the board and probe each pad against GND with a multimeter in DC volts mode. Adjust each pot until the pad reads the target.
Derived thresholds
Full set of rising and falling thresholds the module will exhibit with your settings.
UV_pad = (V_UV_recovery − 0.047) / 30.53
HYS_pad = (V_HYS + 0.058) / 29.89
V_OV_recovery = 30.23 × OV_pad − 0.69
⚡ Paralleling Protection Behavior
⚠️ Why would you need to use a Protect+ module instead of just directly connecting in Parallel?
When two unequal voltage sources are connected in parallel, the higher voltage side will attempt to charge the lower voltage side to bring them both to the same potential.
This uncontrolled flow of current can damage power supplies that are not designed to handle this, as the internal control loop will now try to compensate for what the other power supply is doing. In the case of a battery, an unregulated and potentially dangerous current spike will flow that may be higher than the maximum allowable charge current of the battery, thereby damaging it by plating lithium on the anode and contributing to early failure.
The Protect+ module has an internal comparator which senses the voltage drop across the first pass MOSFET and shuts it off within microseconds if there is any reverse current flow detected, thereby saving your power supply.
In order for the power supplies to share the load, we have found that they generally need to be within 50 mV or less between each other.
To operate the Protect+ module in Paralleling mode:
Use one Protect+ module per power source. Connect when the power is off.
Set the OVC (overvoltage cutoff) limit on each module, or disable the limit by turning the OVC reference to its maximum value.
Connect each power source to its own Protect+ module.
Join the output terminals of all Protect modules together to form the combined output.
(Optional) Add a switch to the Enable terminal on each module to individually turn power sources on or off, as described below.
- Voila! You can turn the power supplies on and you have them in parallel while being isolated from each other.
🟢Normal Operation
When operating within safe voltage limits:
The Safe (green) LED is illuminated
The FAULT signal pin is pulled high to Vcc (via an internal pull-up)
🔌 Optional: Power Switch Function
The Protect module can also act as a main power switch for your system. Simply connect a single-pole single-throw (SPST) switch to the Enable terminal block:
Open switch = Module enabled (normal operation)
Closed switch (connect points 1 and 2) = Module enters low-power mode and disables output
This allows you to toggle high-current power delivery using a compact, low-current mechanical or digital switch.
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