Different Between High Quality And Low Quality

Well, first of all begin our LED driver articles.

Simple Google look, common LED driver there are three, one is the formula RC Buck, this is common in 3-5W spotlights inside the jar, there are many pictures. This application because of its limitations as well as our red sixth principle, the basic is not considered;

The second non-isolated, such as cheap, so in a suite which is basically a standard treasure. After a few cents put a white plastic shell probably cost can be controlled to between one dollar to five dollars. I do not consider this. Since the output terminal is directly interlinked and FireWire. And we use the existing lamp housing reconstruction, after a long time, a great chance of leakage is difficult to avoid the line of fire will be set up to short-circuit the lamp housing. Inside the home, this can be fatal.

The third is isolated, it is below the point.

The figure below three power belong to isolated power from a merchant Taobao, cost about 2-3 yuan, the output current is 300mA or so, left to right are 7W, 12W, and 5W. The figure can be seen clearly mains area and low output region has a wide distance, and even PCB slotted approach to enhance the isolation.

It is clear you can see the figure, the low pressure area and the electricity output region on the PCB layout significantly safe distance as the buffer zone. And PCB slotted to enhance the effect. Mains voltage area up to 400V can be achieved in some switching power supply board, and may even be twice to three times the voltage doubler circuit, or even without a voltage doubler circuit, also because of fluctuations in the secondary side of the transformer and reflected to the primary side on the primary side of the element forming a voltage higher than 800V. The output of the low voltage, normally does not exceed 80V, most of the time will work in a relatively safe area 48V DC or less, which is the reason I chose to isolate the power supply. Even if there is a difference in the dollar to a few dollars on the cost.


First look at this board 7W

 The basic circuit is as follows

After the line of fire of a string of small resistance, measured 0.5 Europe into four similar 1N4007 diode rectifier bridge to do, and then into a small inductor, two voltage 400V, 6.8uF4.7uF 102CBB there is a capacitor composed of "faction type "filter circuit.

After one of the mains voltage rectifier filter out probably in 230VX1.414 = 320V, it will actually fluctuate between 320-380V.

Then separated using resistance all the way down a 5K + 2.4 Europe after the chip to 1 foot to provide the chip's operating voltage VDD.

The primary side of the transformer, also known as primary or the primary, has two windings. Bulk provides a winding circuit primary side inductance inductance into the drain through the primary control chip, a current flows from the source electrode of the chip into the primary side of the high pressure form the primary loop.

Primary feedback winding induced voltage generated after two resistor divider network, enter INV end.

Resistance CS and CS terminal end, which is the figure that gray tetracycline, can control the entire output of the output current and power.

Look at the secondary side, a simple fast diode turn off the main power supply is provided by a 100uF50V withstand voltage electrolytic capacitors.


In accordance with the chip operation manual provided by the manufacturer, the drive power is working in discontinuous flyback current state of constant work, this is what does that mean? Power chip will be around 60K frequency control chip built-in switch. When the primary-side switch turns on when the current in the primary coil will rise, thereby forming a magnetic flux in the transformer circle. But because the secondary winding and the primary winding is reversed (flyback power supply is one such name), this time, the secondary side of the fast diode is off. No secondary side output voltage and current. On the primary side switch conduction period, the primary task is to magnetic circuit inside the transformer flux pumped energy storage. As if to pump inside a vat of water.

When the primary-side switch is closed, as of the primary-side current, fast switching diode is turned on, the water inside the vat when the secondary side flows to the output capacitor and liabilities of the secondary side. . . . After the water inside the vat light, thanks to the secondary side of the output capacitor to the load pour until the output capacitor until the streamer also inside the water, this time, there is a short time, they will not have any primary secondary current. That is the current state of intermittent work.

From the brief description above operating conditions inside, we can see enough to ensure that current and power output capacitors and fast diodes on the secondary side is very important, so that after a power failure will know how to deal with

The figure is the time I collected five in four of the drive power, there are two sub-aluminum, 10W and 30W, constant current 900mA, mainly want to play high-wattage lamp beads. Three kinds of bare board is 300mA current, the most expensive six basic cost, the cheapest one 8, and what work is still very satisfactory.

The basic circuit topology, are using bulk buck, flyback constant current mode, Baidu, there are many scholarly articles provide feedback ah, ah power what the formula. Internal use chip main change is in the feedback section. Need some used optocoupler output from the secondary circuit with the resistance of the sample, and then proceeds to the primary side of the chip feedback pin. Figure left and third from right across the optocoupler has a small slot on the PCB. Very intuitive.

The aluminum Son is wholly filled epoxy sealed, a large hammer to drop out, I refuse this old, in his state of health is still good, they may not be willing to serve the torture.

Well, the simple consolidation will come to an end. Warmly welcome all enthusiasts to explore together.