A few years ago, the market began to claim ultra-thin electricity. A few years ago, the market began to claim ultra-thin power products. With the rapid development of electronic technology, people's source products, along with the rapid development of electronic technology, people daily The electronic products used in daily life are becoming more and more popular. The electronic products used in daily life are becoming more and more light and portable. The most representative ones are notebooks that are light and thin, and the most representative ones are laptops. Its performance is constantly increasing while the size is also computerized. Its performance is constantly increasing while its volume is shrinking and becoming thinner and lighter. Its supporting power supply is shrinking and becoming thinner and lighter, and its supporting power adapter is still bulky. Of course, the thin and light power adapter adapter is still cumbersome, of course, the thin and light power adapter also has, but it can be counted as a handful, why there are, but it can be counted as a handful, why?
Basic components of ultra-thin power supply
â– Slim electrolytic capacitor
â– Ultra-thin magnetic core
â– High efficiency
High efficiency general scheme
â– BUCK PFC
â– Interlaced PFC
â– LLC resonance
â– SR synchronous rectification
In fact, the biggest difficulty in realizing ultra-thin power is not in the selection of components, nor in the selection of the solution, but in the design of the process.
Why do you say that?
An ultra-thin power supply will be produced, and its manufacturing cost will account for more than 50% of the entire power supply, or even more, or even higher...
Let me share some of my insights on the design of ultra-thin power technology.
The product is a full voltage input designed several years ago, outputting a 65W notebook adapter.
The power supply has to be thin, and almost all of the plug-in components have to be installed down. To be ultra-thin, it has to be "smuggled" in size, and even some components have to be installed in a sinking process.
PCBA
side
The total PCBA height is designed to be 10.5mm, the capacitance is φ 10mm, the actual diameter is 10.2mm, and the assembly tolerance of 0.3mm is reserved.
Front view
Back view
Look at the EMC and input filtering sections first.
The EMC filtering part is on a small board, and the line is completed on the small board. Because this product is PSE certified (PSE requires circuit distance before the rectifier bridge), so use two common mode inductors with three layers of insulation. Line and Teflon casing fly lines can reduce wiring difficulty. The advantage of using small board assembly is that SMT placement and plug-in operations can be completed normally without the need for special foot forming of capacitors and inductors.
Let’s take another look at the LAYOUT of the PCB PCB.
EMC small board Toplayer layer
EMC small board Bottomlayer layer
There is a large pad on the EMC small board to provide the AC-N AC-N line circuit and fix the EMC small board at the same time. There are also two square holes for assembly with the main board, so that the EMC small board can be fixed. It can be assembled without a fixture.
Input filter capacitor plate Toplayer layer
Input filter capacitor plate Bottomlayer layer
On the input filter capacitor board, there are also four large pads for the input and output loops, and three square holes for the fixture and fixture assembly. The input filter capacitor plate also has a line connection, which also saves the action of forming the capacitor bend and simplifies the wiring.
Hide the BottomOverlay layer below, then take a look
It can be seen that the pads of the middle two capacitors are not connected in the Bottomlayer and the copper foil. The current is input from the two generous pads on the left to the first capacitor, and passes through the second capacitor and the third capacitor through the Toplayer layer, and then to the fourth capacitor. Capacitance can be effectively utilized to reduce line ripple.
In the above small board assembly design, it is necessary to consider the thickness of the PCB board and the CNC drilling and assembly tolerances. Generally, the PCB in the assembly place should not be copper and place pads or via holes to prevent the PCB from sinking or plating during the manufacturing process. The process affects the assembly tolerance of the plate thickness, and the square hole length also needs to take into account the R angle of the CNC milling edge. Generally, the assembly tolerance of 0.15~0.2mm (0.3~0.4mm total) on one side is required, otherwise assembly will be difficult.
The secondary output filter board is also installed in this way.
Planar transformer is a big tool to achieve ultra-thin, because the AW value of the planar transformer is generally small, so the traditional BOBBIN is generally not used for the winding of the skeleton, and the multilayer PCB wiring is used instead of the copper wire, but because of the safety Need, the secondary coil is still wound with three layers of insulated wire. In order to facilitate the winding, two multi-layer boards are used to wrap three layers of insulated wires in between, so that no additional winding BOBBIN is needed.
Plane transformer
This is a POT3309 planar transformer, using the original POT3311 CORE grinding to 9.3~9.5mm=, using two 4-layer FR-4 PCB layout primary copper wire and one double-sided block double-sided FR-4 PCB layout feedback coil The middle is wound with a three-layer insulated wire.
The structural order is:
Magnetic core - insulating sheet - primary PCB - insulating sheet - feedback PCB - insulating sheet - secondary three-layer insulated wire - insulating sheet - primary PCB - magnetic core.
When welding a planar transformer, it is necessary to lift a 0.6mm thick object on the transformer grounding pad to ensure that the transformer and the input filter capacitor reach the same plane. The left and right positioning of the planar transformer is completely completed by the main PCB of the power supply and the primary PCB of the transformer, and the entire welding can also be regarded as the welding of the fixture.
The rest of the action is to solder the MOS and Schottky after assembling the heat sink. In the entire power supply, in addition to Schottky. In the entire power supply manufacturing, in addition to the input connector soldering, MOS tube heat sink and Schottky heat sink and pin processing need to use the fixture, the other is no jig welding assembly, can increase the volume production, reduce the manufacturing cost.
Let's take a look at the finished PCB frame.
How does this PCB layout change? Do you want to do all the computer? How to make SMT SMT patch?
This problem can be solved by reset stamping. The principle of resetting the stamping die is to use the upper die to stamp the outer frame shape of the PCB board to make it misaligned by 2/3, and then use the lower die to reset it. The PCB board that is made looks like a whole PCB board. However, the design of the PCB frame has been "inserted" in the middle, which not only solves the typesetting problem of the shaped plate frame, but also solves the problem of SMT operation and over-peak PCB board subjected to component pressure deformation.
Let's take a look at the PCB made by the typesetting mold.
After the peak is completed, the PCBA can be removed by cutting the PCB frame, which also avoids the problem that the components of the PCB board and the weak parts of the PCB are damaged by external forces.
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