Description of parameter adjustment method of constant current and constant voltage power supply module

Click image to buy

foreword

At present, the common descriptions about power modules on the market are mostly found in constant voltage power supplies. In most cases, the parameter detection and adjustment of the module without special instructions are for constant voltage power supplies (there are also some special cases where the power supply only has a constant current function. It will not necessarily be explained below), then about the role of the two functions of constant voltage and constant current of the power module, and how to adjust them. This article will explain my personal understanding of these two aspects. I hope Can be helpful to everyone.

power module

Here we divide the common power modules into two categories, one is the 恒压电源module, the other is the 恒流电源module. Below we will give a brief introduction to the two categories of power modules.

constant pressure

A simple understanding of the power supply module that can adjust an input stable or unstable voltage is 稳定电压输出called a regulated power supply module (personal summary). This type of module can output a stable or specified voltage (provided that the input is within the specified range)

They have a maximum output current parameter. It should be noted that the output current will automatically adjust with the connected load but will not exceed the maximum current output capability. Many friends have misunderstood this aspect.

When the output current exceeds or reaches the limit value, it will cause damage to the module or enter the constant current mode, and some will enter the constant current mode, depending on the module, so when the voltage drops, the module is often reached here. The limit value of this situation, or the parameters required by the load are too large

constant current

It can be understood from the literal meaning that constant current refers to 恒定电流输出a power supply module that can adjust the stable or unstable voltage of an input. We call it a constant current power supply module (personal summary). However, there are relatively few pure constant current output modules on the market. , it is common to have on the LED controller, and more often have two functions of constant current and constant voltage to adjust

Parameter adjustment

There are many friends who have big doubts about the adjustment of the constant current situation, so here we are more related to the adjustment of the constant current value, and the parameter adjustment is more dependent on the Ohm's law learned in junior high school. : U=IRto perform parameter calculation, so the related calculation of adjustment parameters will not be too complicated

It is worth noting that the module with constant voltage and constant current functions 恒压与恒流is only possible 二选一, and it is impossible to adjust the constant voltage to the ideal value and the constant current to the ideal value.

According to Ohm's law, U=IRit can be seen that when the constant current Iis constant, the voltage Uis completely determined by Rthe size of the load. Therefore, when the load Rchanges during measurement, the voltage across the load will also change accordingly.

In the same way, according to Ohm's law, U=IRwhen the constant voltage Uremains unchanged, Ithe Rchanges with the size of the load, and the current passing through the measured load will also change accordingly when the load Rchanges

Then the actual adjustment method will also be adjusted according to the above theory.

Constant voltage regulation

The constant voltage regulator here is a module that has both constant current and constant voltage functions. Generally, there is a potentiometer on the module that only adjusts the voltage, and it can be adjusted by screwing directly.

Take the following constant current and constant voltage buck-boost module as an example

When we need to output a stable voltage, 空载直接拧CV电位器the voltage will change when the potentiometer adjusts the voltage. At this time, we can directly screw it to the position we need. Another situation is that the voltage will not change after screwing. This time is generally 电位器不在电压调节范围内caused by Yes, there is no problem in adjusting directly to the direction of the maximum output value until the voltage changes.

After we adjust the no-load to the specified parameters, the load situation may not be ideal (the voltage may be pulled down, etc.), and there is an abnormal situation after the load is generally 负载超出了模块输出电流的最大值, or the constant current potentiometer is set. Yes, but at 恒流值过小this time we cannot see the constant current value, because the voltage has been set, the adjustment of the constant current potentiometer is relatively simple, and the constant current potentiometer can be adjusted directly in the direction of increasing the constant current value, until the voltage value returns to normal

Constant current regulation

The voltage output by the module can be seen very intuitively by measuring the output terminal of a multimeter, but the constant current value cannot be directly observed. The constant current value adjustment is divided into the following three steps. Here, the parameters we need to adjust are 1Aconstant current value as an example, a linear load needs to be prepared, I use an electronic load here to adjust the resistance to10Ω

1. It U=IRcan be known from , that the current needs to be set to 1Aconstant current, the linear resistance is 10Ω, the set constant voltage value must be greater than 10V, otherwise the size of the current will be limited by the voltage, then we output the terminal under no-load condition Connect a multimeter and adjust the voltage to 20V

2. Connect a high-power linear load to the load end (there is a current output indicating that there is a certain power output), the linear load is convenient for us to calculate, I adjust it to 10Ω resistance here, and connect a multimeter in series with the current gear to observe the current (electronic load). You can directly observe the current), at this time the current will be equal to 1A or less than 1A

In two cases, if it is less than 1A, directly screw the constant current potentiometer to increase the current to about 1A.

Then obviously the constant current value of my module below is greater than 1A at this time

3. If it is greater than 1A, reduce the current potentiometer. It is worth noting that when the current is about 2A, the current of the constant current potentiometer may not change (my current situation is the case), because the current module is in constant In current mode, you need to further reduce the constant current value until there is a change and then adjust to 1A current

4. According to the above adjustment, the constant current value is 1A, then we replace the load with a 15Ω resistor to observe whether the current is still 1A. According to U=IR, we can know that the voltage value output by the module should be about 15V at this time. According to the above Verify, the following picture is the verification result of this adjustment

Summarize

Personally conclude that the adjustment of constant current and constant voltage of this type of module is more about the use of Ohm’s law. The parameter setting of constant current and constant voltage can be understood as setting the upper limit of the voltage and current output by the module. There are many problems. It is the first time to write this kind of article. Welcome to correct me!