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1. In the 80's, 90's and even the first half of the 21st century, the low-electromagnetic interference switching power supply adapter required for color televisions was a non-flyback switching power supply.
The power supply of the TV is a very strict power supply, mainly because of the limitation of electromagnetic drying, because the circuit part of the TV with TV signal receiving is extremely sensitive to electromagnetic interference, and the switching power is a relatively strong electromagnetic dry resistance. Source, if the circuit power and control mode of the home computer power supply is transplanted into the switch power of the TV set, then the TV will generate a regular snowflake point due to the electromagnetic dry resistance generated by the power adapter switching process, without paying attention to the desired View image.
To take a step back, use a switch-like electrical control chip similar to UCs to control a flyback power adapter. Is it possible to use this flyback power adapter in a TV set? It turns out that the electromagnetic dry resistance is still very large. It does not apply to TV applications.
For the above reasons, China's color TV set used the technology of Japan's early self-excited flyback power adapter to obtain low electromagnetic interference until the mid-1990s, but the cost of this technology is lower. The loss of the machine is also very large.
2. Computer monitors generally use a reverse power adapter
In computer monitors, most of them use flyback power adapters, and basically use UOs series chips as control C, so the circuit is reliable. Because of this, the annual sales volume of UCM2 series chips is over 100 million, and the price is also greatly reduced. Even the unit price in large quantities can be no more than 1 yuan, which brings great impetus to the popularity of UC2 series chips.
3. The simplest single-chip reverse power adapter for the circuit - a TOPS series chip and a single-chip trans power adapter
UC842 series chips need external components, the area occupied on the circuit board can not be ignored, if you want to greatly reduce the size of the power adapter, there will be many difficulties, the US company has a single-chip power adapter chip a 0FSh series. The original monolithic power adapter chip requires only three pins, much like an integrated voltage regulator. The monolithic power adapter chip includes a control part of the power-on control chip, a high-voltage switch tube, a built-in start-up circuit, and the like. Therefore, only the transformer, the rush circuit, the shaft auxiliary winding and the rectification and filtering section are required on the primary side of the transformer. The secondary side of the transformer is identical to a typical flyback power adapter.
Since the switching tube and the control circuit are integrated in one package, the occupied circuit board area is greatly reduced, so that a small power supply adapter can be made.
As the requirements for various control functions continue to increase, the pins of the TOP Swih Series E continue to increase, the peripheral circuit components continue to increase, and the efficiency of the T0FShh Series L is relatively low, which makes the application of the TOSh Series C. The value is getting lower and lower, and once the power factor correction becomes a must, the TU Swtch Series E will be an undeniable necessity to exit the power adapter field. The reason will be discussed in the relevant chapters of this book.