Test and Teardown of a 120W Charger Bought for 2.6 Yuan on Douyin Mall- Zeruns's Blog

This blog post is about testing and tearing down a 120W fast-charger bought for 2.6 yuan on Douyin Mall.

This charger claims to be compatible with Huawei devices and is designed to look like an official Huawei charger.

Let's take a look at the quality of such a low-cost charger.

Test and teardown video: https://www.bilibili.com/video/BV1kf42127Cu/

Unboxing and teardown review of the Yuli/Torria adjustable power supply X08P3010: https://blog.zeruns.com/archives/698.html

Simple unboxing and review of the Ruideng RD6012P programmable adjustable power supply, a 60V 12A DC power supply with buck and linear voltage reduction: https://blog.zeruns.com/archives/740.html

Purchase link for the official Huawei 100W charger: https://u.jd.com/9sxOBRm

Product Appearance

It has only one USB-A output port, with "120W Fast Charge" written below.

Information printed on the charger:

Model: 120W
Input: 180-240V ~ 1.8A 50/60Hz
Output: 5V/9V/12V/15V=3A, 20V=3.3A

Manufacturer: Shenzhen Vitamei Trading Co., Ltd.

The charger weighs 53.5 grams.

Testing

First, let's test the supported fast-charging protocols. There are quite a few, but the maximum output voltage only reaches 12V, not the claimed 20V.

In actual testing, the highest output voltage is 12V, with a maximum output power of 15.6 watts. When fully loaded, the output voltage drops from 12V to 9V, and the charger's conversion efficiency is around 80%.

When the charger outputs 12V1A, the peak-to-peak ripple is around 460mV, which is a bit high.

The ripple when the 5V output is no-load is shown in the figure below, with a peak-to-peak ripple of about one hundred millivolts.

Teardown

Removing the top cover.

Taking out the circuit board, there is a weight block on the transformer. This power supply is likely a flyback switch-mode power supply.

Removing the weight block.

The bottom side of the PCB.

On the side, the AC input side filter capacitor is 400V 6.8μF, which is a bit small. The Y capacitor is 2.2nF.

The output side filter capacitor is blocked by the USB interface, only showing a voltage rating of 16V. The capacitance value is not visible, but it was measured with a multimeter to be 644μF.

A carbon film resistor is connected in series before the rectifier bridge at the AC input end, acting as a current-limiting resistor.

The rectifier bridge model is MB10F, with performance parameters of 1000V/1A.

The power chip on the primary side of the high-frequency transformer is model FAB3B09A, and no information could be found about it.

Pin 2 of the chip is connected to the negative pole of the rectifier bridge through a 1Ω resistor, which is likely a current-sensing resistor used to detect current. Reducing the resistance value could increase the output power, but it would not be safe.