Design of nickel-metal hydride battery charger circuit PCB

- Sep 15, 2018-

1. Introduction to Protel software

With the rapid development of electronic information technology, PCB(printed circuit board) designed by hand cannot meet the needs of the development of electronic technology.We must use computer to complete the design of PCB, which is not only fast, accurate, and can greatly reduce the labor intensity of engineers and technicians.There are many kinds of software involved, and Protel is one of them. 

Protel is the circuit aided design system launched by Altium. It is the first board card-level design system integrating all design tools, including schematic design, PCB design, circuit simulation, PLD design and so on.Its earliest version was TANGO software package, which later developed into Protel for DOS, Protel for Windows, Protel 98, Protel 99 SE, Protel DXP and Protel 2004.As the version continues to evolve, it becomes more powerful. 

Compared with other versions, many new functions of Protel 2004 make the operation easier and more automatic, making it easy for us to carry out various complicated circuit board design. 

2. PCB design

PCB is the abbreviation of Printed Circuit Board.Printed circuit board is made into conductive circuit and component package by printed method. Its main function is to realize fixed installation of electronic components and electrical connection between pins, so as to realize various specific functions of electrical appliances.Making correct, reliable and beautiful printed circuit board is the ultimate goal of circuit board design. 

The general process of PCB design includes: making preliminary preparation, making PCB component pin package, building new PCB files, planning circuit board, loading component pin package and network, layout, wiring, DRC design rules inspection, etc. 

3. Design of ni-mh battery charger PCB

Ni-mh battery charger is a common electronic product in our life.The basic steps of PCB design with Protel 2004 are as follows. 

3.1 create the project file

To facilitate the management of design documents and their seamless connection and synchronization design.In Protel 2004, project files are used for management. First, a project file is created, and then each design file is created or added under the project file. 

3.2 create schematic file and complete schematic design of battery charger circuit

The circuit principle of ni-mh battery charger is shown in figure 1 below. 

Figure 1 schematic diagram of battery charger

Figure 1 schematic diagram of battery charger

3.3 create PCB files and plan

There are two ways to create a PCB file in Protel 2004: create with the file menu and create with the wizard. It should be noted that the PCB file created with the wizard is not in the project file, and must be put into the project file after the creation, otherwise the following steps cannot be done.According to the composition of the charger circuit, the first step is to plan the shape of the board as a rectangle, and the size of the board is determined as 2400mil x 1300mil according to the number of components. The single layer wiring is designed as a single panel. 

3.4 load component pin package and network and conduct component layout

All components in this circuit adopt the form of jack package.In addition to the battery pack is polarity of encapsulation, other components all use Protel 2004 components in the library standard packaging, we need according to the actual circuit for the battery pack is polar end set out the packaging, the first to create their own device packaging library, in the garage to create as shown in figure 2 BT1 - BT4 encapsulation, and then set the encapsulation to battery encapsulation. 

Component layouts can be arranged automatically and then manually.Note that the transformer is not placed on this board.Attention should be paid to the arrangement and distribution of components and components in a reasonable and uniform layout. 

FIG. 2 battery charger PCB

FIG. 2 battery charger PCB

3.5 set wiring rules and conduct wiring

The so-called "wiring" is to use printed wires to complete the wiring relationships of various components in the schematic diagram.After completing the component layout of any circuit board, the next thing to do is to connect the components with wires to make them have electrical characteristics, thus forming a complete circuit board. 

In Protel 2004, the wiring rules should be set first to meet the electrical requirements such as safety principles.According to the actual requirements of the charger circuit, safety spacing here is set as 10mil, top level wiring, normal wire width is 10mil, power line is 20mil, ground wire is 30mil. The wiring adopts automatic wiring, and it can be modified manually at last if it does not meet the requirements.When wiring, under the premise of meeting the electrical requirements such as safety principle, the conductor should be concise, as short as possible, and as few turns as possible, so as to make the conductor simple and clear. 

In addition, the routing design should consider whether the assembly is convenient.Finally, the board is required to be beautiful and economical, good PCB board wiring is beautiful, and the work is fine, and it looks like a work of art. 

3.6 inspection and error exclusion of DRC design rules. 

After the circuit board design is completed, in order to ensure that the design work performed meets the requirements, the inspection work can be done automatically by the computer, that is, the inspection of DRC design rules.Upon completion of the check, the system will pop up the Messages message box and modify the design according to the message prompt until there are no errors.The PCB design of the circuit is completed here. The PCB file of the designed charger is shown in figure 2.Finally, we can print and output the drawings and reports, and carry out corresponding follow-up work such as actual plate making. 


4, summarize


Protel 2004 software is used for PCB design, simple operation and high degree of automation.The design of ni-mh battery charger PCB has the common characteristics of PCB design, and also has certain characteristics.It takes a lot of experience to design a perfect charger PCB.With the development of electronic technology, electronic circuit is more and more complex, which requires designers to constantly improve the design level and design more high-quality PCB products.