Power Supply Design Guide for Wireless Modules

Wirelesscommunication has already penetrated people's lives. More and more companiesare designing wireless modules. More and more friends are engaged in RF design.The following are some of the power supply design considerations for wirelessmodules that I have summarized. Helpful. If you have different opinions orsuggestions, I hope that you can contact us in time through the officialwebsite of Chengdu Ebyte, so that we can correct and modify them in time.

The following sharing is mainly divided into two aspects: the performance ofthe power supply and the PCB layout of the power circuit.
1. Design of performance indicators of power supply

The main indicators of the power supply are load regulation, voltageregulation, ripple, etc. This paper discusses the power supply specification ofthe wireless module from two aspects of load regulation and ripple of the powersupply.
2, load adjustment rate (LOAD REGULATION)

The load regulation rate, that is, the change in the power supply load, causesa change in the power supply output, the load increases, and the outputdecreases. On the contrary, the load decreases and the output rises. Outputchanges due to good power load changes are minimized, typically 3% to 5%.

The load regulation rate is a measure of the quality of the power supply. Whenthe power supply is connected to the load, the voltage drop is small. Its loadregulation rate = (output voltage at full load - output voltage at half load) /output voltage at rated load.

This indicator is also very important in the power supply design process of thewireless module. Because the wireless module is often in the receiving,transmitting, sleeping and other modes, the load of the power supply isconstantly changing, so the power supply of the module is required to be good.Voltage regulation rate. In addition, due to the characteristics of thewireless module, it will require a large current at the beginning of the signaltransmission. The transient transmission current varies according to the moduleof different power. Therefore, the design should also take into account thatthis provides enough for the wireless module. Large transient currents ensurethe integrity and correctness of signal transmission.
3, ripple

Simply put: ripple is the alternating component of a DC voltage. The DC voltageshould have been a fixed value, but in many cases it is rectified and filteredby AC voltage. Since the filter is not clean, there will be residual ACcomponents, even if it is powered by battery, it will be affected by loadfluctuation. And ripples. In fact, even the best reference devices have rippledoutput voltages.
4, the ripple voltage hazard:

It is easy to generate undesired harmonics in the equipment, and harmonics willcause more harm, and harmonics in the communication system of the wirelessmodule will have a bad influence on the quality of communication and the like.

   Larger ripples can reduce the efficiency of the powersupply, and as a result, the overall power consumption of the wireless moduleis increased. The module receives limitations in applications such as low powerconsumption.

   Large ripples are prone to surge voltage or current,which can easily damage the MCU and RF chips.

   The large ripple is easy to interfere with the logicrelationship of the digital circuit, affecting the normal transmission of dataand the normal communication of the module.

   Larger ripples are prone to noise interference, makingthe wireless module susceptible to interference during transmission andreception, resulting in communication failure.

   The above describes the impact of the power supplyindicator on the module. The following describes the impact of the improvedperformance approach on the module.

5, the method of suppressing ripple:

   In the case of cost and volume, use full-wave orthree-phase full-wave rectifier circuits whenever possible.

   Increase the capacitance of the filter circuit, and usea better LC filter circuit when conditions permit.

   Use a good voltage regulator circuit to use an analogregulated power supply instead of a switching power supply where ripplesuppression is critical.

   Reasonable wiring.

6, PCB layout considerations

In addition to the reasonable design of the power supply performanceindicators, in the power supply design of the wireless module, we should alsopay attention to the layout and routing skills of the PCB to improve theperformance of the power supply and electromagnetic compatibility with the RFcircuit.

I will not discuss the layout and routing skills of RF circuits again. Thisarticle focuses on the detailed description of the power supply in the wirelessmodule and the specific design case.
7, PCB layout note:

In the design of the RF module, the power supply circuit should be separated fromthe RF as much as possible, because the power supply has a certain ripple thatis too close to the RF circuit to cause interference and unpredictable effects.

The power supply part wiring needs to have a power cord of sufficient thicknessand a reference ground for the fast reflow of the power supply, because themodule needs to transmit the current instantaneously and the power supplybackflow needs to be fast enough.

The filtering of the power supply should be such that the filter capacitorshould be as close as possible to the MCU, RF IC, PA, etc. that are powered, sothat the filter circuit can play a greater role.