LNK227 is not non-common IC Chip in electronic technology.So,TOP221,TOP222,TOP223,TOP224,TOP225,TOP226,TOP227is the family-Three-terminal off-line PWM switch and it has same function as feature in application.This family has two generation but TOP221-TOP227 is the developed second generation of TOPSwitch IC.And then with the enhancement,TOP221-TOP227 has severals affect:extends the power range,reduce the sensitivity to board layout and line transients through out make the design even easier,reduces cost in lower power, and high efficiency applications.Moreover,this brings TOPSwitch technology advantages to many new applications, i.e. TV, Monitor, Audio amplifiers, etc.
2.Input voltage and type packet
This part of TOP is so quite difficult to get to any technician.By the complexition,this TOP is usually divided to each packet to determine the input voltage of each parts.Normally,TOP221-TOP227 have 3 typical type is G packet,D packet and Y packet (TO-220/3).And the input will be showed in the table here.
Depend on type packet,Pin of this TOP is have quite difference to each part and make the change to each circuit application.
DRAIN Pin: Output MOSFET drain connection. Provides internal bias current during start-up operation via an internal switched high-voltage current source. Internal current sense point.
CONTROL Pin: Error amplifier and feedback current input pin for duty cycle control. Internal shunt regulator connection to provide internal bias current during normal operation. It is also used as the connection point for the supply bypass and auto-restart/ compensation capacitor.
SOURCE Pin: YN package – Output MOSFET source connection for high voltage power return. Primary side circuit common and reference point. PN and GN package – Primary-side control circuit common and reference point.
SOURCE (HV RTN) Pin: (P and G package only) Output MOSFET source connection for high voltage power return.
4.How LNK221-LNK227 do in circuit?
Because of the complication,TOP227 is quite difficult to explain simply in circuit.But if we take care of each point,we can realize easily and get knowledge from there.So,one example of 20 W Universal Supply using 8 Lead PDIP will show to study.As you know that the current in input is always alternative so before going to circuit,the current have been converted to DC.This process may be cut because It don’t really need to show.
In 4 W TOPSwitch-II Standby Power Supply using an 8 lead PDIP example,firstly,the converted direct current go through to primary coil and continuously go to the TOP227 from D pin to S pin.In the TOP227 IC which link to circuit,the Mosfet is stored and have a G pin like a gate to open and close and the pulse generator which create oscillation to control the G pin.If the generator run to make oscillation to G pin,the G pin will close and the current can go across.If the generator is OFF,the current can’t go through and the current will go back to the primary coil and stored at there.
This trouble cause the leaking voltage which can drop and make harm affect to D pin.To prevent this problem,resistor R3,capacitor C1 and diode D1 is clamped to rectifier and filter the voltage.
With the variable voltage,the current will transmit to two secondary coil(output device and feedback circuit) by the pulse transformer.In the output circuit of secondary coil, the current is continuously rectifiered by diode D2 and filtered by capacitor C2 C3,inductor L1 before going to output.
By the way,in the feedback circuit of secondary coil,the current ,after being rectified by D3 and filter by C4 and C5,drop across to the LED U2.At the process,if the ouput voltage (which is determined by the sum of VR1 and the voltage drop) increase exceedly the suitable output voltage,the LED will light by the voltage determined of R1 and R2 and the U2(as a lock) will locked and the C Pin will identify the problem and adjust the voltage in the output device.
In conclusion,TOP221-TOP227 family bring new information and create diversity in elctronic technology so in example,it prove that TOP227 is not too hard to understand.Hope people can get more knowledge in this blog.Thanks for your attention.