Top264,top265,top266,top267,top268,top269,top270,top271......topswitch-jx top264-top271 family ic--simplicity or complication and how to analysis in example circuit?



TOP264-271 TOPSwitch-JX Family is also Mosfet kind and TOPSwitch-JX  have multiple function to apply and use: cost effectively incorporates a 725 V power MOSFET, high-voltage switched current source, multi-mode PWM control, oscillator, thermal shutdown circuit, fault protection and other control circuitry onto a monolithic device.Additional,EcoSmart – Energy Efficient,High Design Flexibility for Low System Cost,Extensive Protection are features which make TOP264-271 become more specially and possible for many circuit.

2.Output device and Packet

TOP264-271 TOPSwitch-JX Family is used for two kind of circuit is PCB Copper Area and Metal Heat Sink and cause the difference of type packet as output voltage.TOP264-271 have two type packet is VG and KG executed in Copper Area ,by the way,EG is used in Metal Heat Sink circuit.

3.Functional Pin

TOP264-271 TOPSwitch-JX Family is diverse function and with each type of packet,it is not similar on Pin but it also has some main Pin in circuit.

DRAIN (D) Pin:(simple: receive the through voltage of current and start the Mosfet.) High-voltage power MOSFET DRAIN pin. The internal start-up bias current is drawn from this pin through a switched highvoltage current source. Internal current limit sense point for drain current.

CONTROL (C) Pin:(simple: a low impedance node that is capable of receiving a combined supply and feedback current to control oscillated cycle) 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.

EXTERNAL CURRENT LIMIT (X) Pin:(simple: used to reduce the current limit externally to a value close to the operating peak current, by connecting the pin to SOURCE through a resistor. This pin can also be used as a remote-ON/OFF input) Input pin for external current limit adjustment remote-ON/OFF and device reset. A connection to SOURCE pin disables all functions on this pin. This pin should not be left floating.

VOLTAGE MONITOR (V) Pin:(simple: usually used for line sensing by connecting a 4 MW resistor from this pin to the rectified DC high-voltage bus to implement line overvoltage (OV), undervoltage (UV) and dual-slope line feed-forward with DCMAX reduction) Input for OV, UV, line feed-forward with DCMAX reduction, output overvoltage protection (OVP), remote-ON/OFF. A connection to the SOURCE pin disables all functions on this pin. This pin should not be left floating.

FREQUENCY (F) Pin:(simple: sets the switching frequency in the full frequency PWM mode to the default value of 132 kHz when connected to SOURCE pin. A half frequency option of 66 kHz can be chosen by connecting this pin to the CONTROL pin instead. Leaving this pin open is not recommended.) Input pin for selecting switching frequency 132 kHz if connected to SOURCE pin and 66 kHz if connected to CONTROL pin. This pin should not be left floating.

SOURCE (S) Pin:(simple: connect with other Pin then receive voltage after Mosfet C Pin working and transmit thruogh the circuit)Output MOSFET source connection for high-voltage power return. Primary-side control circuit common and reference point.

NO CONNECTION (NC) Pin: Internally not connected, floating potential pin.

4.Analysis TOP264-271 TOPSwitch-JX Family in circuit?

Top264-Top271 is complex structure IC so with a examp of f High Efficiency 19 V, 65 W, Universal Input Flyback Supply with Low No-load,see that the circuit is quite difficult to see and learn.So to go deep into,we can only look at some important points to be easy to follow.

Because of having too many components,we will  divide to each part to explain for being understandable.In the input part,having inductor L3 and L4 , capacitor C1 are clamped to stable the input voltage through out rectifier and filter as well as resistor R1 and R2 is set to reduce input  with 4.2 MΩ.The rhombus diode D1 is used to convert the VAC input voltage to VDC for the current can access to circuit.

In the second part,we have resistor R3,R4,R7,R8,R9.The voltage current is increased to 10.2 MΩ and rectifier one more time to smoothy by R3 and R4.And then R7,R8,R9 is designed to control overload for the input voltage through out limit the error before going to other components.

The current go to the primary coil and drop access to Mosfet of TOP from D Pin to S Pin by the activation of pulse generator in IC.In here,if the generator is ON,the G Pin as a Gate will close and allow the current go through,By the way if the generator is OFF,the current can’t go through but the current will be stored at the primary coil and the voltage can comeback to D pin and cause the damage.So the protection combined VR2,R11,R5,R29,R28,diode D2 and capacitor C4 will prevent and remove the harm voltage.

After that,the current will be transmited to secondary coil by the Mosfet with the variable frequency.In here,the FL1 and FL2 coil will make the current gone to output after filtered by C12,C13,C14,R15,and D5.

Beside,the 4 and 5 secondary coil has a feedback mission.In here,the current also is rectified by D4 and dropped access to the LED U3.And then,the LED U3 will light when the output voltage is overload which calculated by the sum of the dropped voltage of R25 and the voltage of R16.So Transistor Q1 and VR1 added to improve the output overvoltage shutdown sensitivity after go to C Pin of Mosfet.After that,the C Pin will active if identify the problem and control the cycle of Mosfet and assurance quality output voltage.

That’s all about this IC and we also feel the headache of IC in circuit.But anyone should take a time to follow and learn about for applying in other circuit.Thanks for your attention.



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