Overview of DC-DC Step-down Buck Converters from Aliexpress

  • Testing Conditions and Parameters — In most cases, I tested with an input voltage of 20V and an output set to 5V. The testing was terminated when any component on the module reached a temperature of 212°F(100°C).

  • Dropout Voltage — This is the minimum possible difference between the input and output voltage. For example, if we have a 12V input and a dropout voltage of 0.7V, we cannot obtain more than 11.3V at the output. Quite often, the voltage drop is directly dependent on the current.

  • Quiescent Current - This is the amount of current consumed by the module with no load connected.

  • Switching Frequency - This is the frequency at which the power transistor controls the flow of current to the inductor. Higher frequencies result in lower output ripple, which allows for the use of more compact inductors and capacitors. However, there is a drawback: increasing the frequency increases the heat generation of the power transistors and the level of high-frequency noise.

Non-synchronous Converter

The Non-synchronous Converter features a classic and simple circuit topology. In this design, current is supplied to the inductor through an active switch or circulates through a diode from ground when the switch is off.

However, this diode is the bottleneck of this design. Due to its physical properties, a voltage drop always occurs across it, leading to inevitable power losses.

Let's consider an example: the converter outputs 5 V and 5 A, which equals 25 W of useful power. If the voltage drop across the diode is 0.5V, the losses will be: 0.5V * 5A = 2.5W. This means we are wasting 10% of the energy.

As you can imagine, these losses do not disappear without a trace; they are converted into heat, causing compact SMD diodes to overheat. For example, let's take a look at the the popular LM2596 module, which typically uses an SS34 Schottky diode:

  • At a current of 1 A, it heats up to 50°C.

  • At a current of 2.5 A, the temperature reaches 106°C, which is a critical level, close to component failure.

Although the chip itself is theoretically capable of delivering 3–5 A, the underpowered diode in cheap modules becomes the limiting factor.

MP1584

  • Dropout Voltage: from 0.1–0.15V

  • Operating Input Voltage: 4.5–28V

  • Switching Frequency: 900 kHz (up to 1.5 MHz depending on configuration)

  • Heating:

A key advantage of this module is its record-low quiescent current. This makes it an attractive choice for battery-powered portable devices where conserving power in standby mode is critical.

LM2596

  • Dropout Voltage: from 0.7V.

  • Operating Input Voltage: 4.5V – 40V.

  • Switching Frequency: 54 kHz. Such a low frequency indicates that the chip is not original or has been remarked (it contains the die of the obsolete LM2576). A genuine LM2596 operates at 150 kHz.

  • Heating: The heating pattern depends on the operating mode. If the difference between the input and output voltage is small, the "LM2596" chip itself heats up primarily. In cases where the voltage difference is significant, the diode generates most of the heat.

XL4015 CV/CC

  • Circuit Design: The main feature of this module is its true constant current (CC) mode. This logic is implemented not by the XL4015 chip itself, but by an external operational amplifier on the board. This allows the module to be used as a battery charger.

  • Protection: The chip features a Frequency Foldback function. If a short circuit is detected, the operating frequency automatically drops from 180 kHz to 48 kHz. This reduces current and heat generation, which is intended to save the chip.

  • Dropout Voltage: from 0.1v, at 2А - 0.37v

  • Operating Input Voltage: 8v - 36v

  • Switching Frequency: 180kHz


  • Heating: The thermal profile of the module changes depending on the load: up to 2A, the inductor is the hottest component; above 2A, the Schottky diode begins to heat up more.

XL6019E1 (Buck-Boost module)

  • This is a versatile Buck-Boost module — it automatically steps up or steps down the voltage to stabilize the output.

  • Dropout Voltage: None — it can operate even if the input voltage is equal to or lower than the output voltage.

  • Operating Input Voltage: 5V – 40V. Note: if you apply less than 4 volts, you may unexpectedly get a voltage spike of up to 20–30 volts at the output with no load.

  • Switching Frequency: 180 kHz.


  • Heating: Once again, in this module, the diode heated up much faster than the chip. The XL6019 chip itself only reached 67 degrees at a current of 3 A.


XL4016E1 CV/CC (Green with Heatsinks)

  • In this module, a powerful diode array is used instead of a single diode. Heatsinks are installed on both power components: the diode a rray and the XL4016 chip itself. A current limiting circuit based on an operational amplifier is also implemented.

  • As with the XL4015, the XL4016 features Frequency Foldback (frequency protection during short circuits).

  • Dropout Voltage: from 0.1V at 1А

  • Operating Input Voltage: 8V – 36V.

  • Switching Frequency: 180 kHz.


  • Heating:

Synchronous Converters

As previous tests have shown, the standard rectifier diode often becomes the circuit's "bottleneck" due to overheating. To solve this problem, engineers replaced the diode with a second MOSFET.

Why is this effective? When turned on, a MOSFET acts like a regular resistor with negligible resistance—hundredths or even thousandths of an Ohm. Consequently, energy loss and heat generation are drastically reduced.

The second transistor is controlled by an inverted signal. This means that when the high-side switch (top) is on, the low-side switch (bottom) must be off, and vice versa. Turning on both transistors simultaneously is impermissible, as it would lead to a short circuit.

Mini360 MP2307:

  • Dropout Voltage: from 0.5V

  • Operating Input Voltage: 4.75V - 23V

  • Switching Frequency: 340kHz


  • Heating:

Mini560 JW5069A

  • This module has a fixed output voltage — mine was 9.2V. It can be changed by replacing resistor R3.

  • Dropout Voltage: from 0.2V

  • Operating Input Voltage: 4V - 23V

  • Switching Frequency: 500 kHz


  • Heating:


TPS40057


The module manufacturer tried to erase the marking on the chip, but did it carelessly.



Based on the last digits “57” and the TSSOP-16 package, I found the TPS40057 datasheet and checked the pin correspondence — everything matched.

  • Operating Input Voltage: 8V - 40V

  • Dropout Voltage: - from 1.5V

  • Switching Frequency: 165 kHz (the chip itself supports up to 1 MHz, but this module is configured for 165 kHz).


  • Heating:

As we can see, the TPS40057 is one of the most powerful modules in this review. Handling 15A is virtually no problem for it; if not for the current-sensing resistor, it could deliver even more.

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