HLK-PM01 5V Backfeed

When your IoT device supplies power back to the output of the HLK-PM01 via its USB-C port, this creates an abnormal operating condition that may lead to the following issues:

The output of the HLK-PM01 is not designed to accept reverse current or reverse voltage. If a reverse voltage is sustained, it can break down internal components such as MOSFETs or capacitors, causing permanent damage.
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Risk of Short Circuit

If the HLK-PM01 is actively trying to output 5V while an external 5V source is simultaneously applied, it can cause a conflict between the two power sources. This creates a short-circuit path, leading to overcurrent or overheating.
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Activation of Protection Mechanisms (Limited Effectiveness)

Although the HLK-PM01 features output short-circuit protection (with auto-recovery), this protection is primarily designed for load-side shorts and cannot effectively prevent damage caused by a reverse voltage input. The output overcurrent protection (110%-150% of load) is also not designed to handle reverse power feeding.
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System Instability

Even if no immediate damage occurs, reverse power can cause the module to malfunction, restart, or have an unstable output.

Recommended Solutions
To prevent these issues, please take the following measures:

Solution 1: Use a Diode for Isolation (Recommended)
Connect a Schottky diode in series between the output of the HLK-PM01 and your IoT device. For example:
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Model: 1N5819 or SS14
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Reason: These have a low forward voltage drop (approx. 0.3V), making them suitable for 5V systems.
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Function: It allows the HLK-PM01 to power the device but blocks the device from feeding power back.

HLK-PM01 5V Output → [Anode of Diode] → [Cathode of Diode] → IoT Device's 5V Input
GND of HLK-PM01 → GND of IoT Device

Solution 2: Add a Reverse Voltage Protection Circuit
You can use a dedicated protection IC or design a simple reverse voltage protection circuit to ensure safety.

Solution 3: Disable USB-C Reverse Power Charging
If your IoT device supports the USB-C PD protocol, we recommend disabling its "power output" or "reverse power" function in its settings or physically cutting the path on the hardware.
Additional Notes*
From the product knowledge base:

The HLK-PM01 has a rated output current of 600mA, with a maximum of 700mA.
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The output includes short-circuit protection with auto-recovery.
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However, these built-in protections do not apply to reverse voltage input.