I endeavored to develop a simple 12V 500mA SMPS circuit. It makes use of an built-in circuit TNY267P of a sequence of circuits TinySwitch-II: TNY263, TNY264, TNY265, TNY266, TNY267 a TNY268.
This part combines together the control circuit and the switching element (MOSFET), current and thermal fuse and self-power technique.
This really is the whole thing essential to a compact flyback supply. It neglects to even require an auxiliary winding. All of this is adapted into DIP8 package (just the same as the 555)! The highest voltage is 700V, the operating frequency is 132kHz.
Referring at the schematic diagram of the simple 12V 500mA SMPS circuit it becomes clear below. On account of the minimal power, I employed halfwave rectifier. Voltage highs are controlled applying transil (zener diodes) 180V.
This can easily be replenished by the customary parallel composition of resistance and capacitor.
Feedback will be supplied with optocouplers, the minimum threshold is picked out purely via zener diode (ZD). ZD achieves the output voltage.
It happens to be approximately 1V above the formal voltage of ZD, due to the fact that the voltage decline of the LED optocoupler is occupied. For 19V output voltage ZD 18V is implemented.
As expected i better not force one to construct 19V supply – output voltage are typically fine-tuned by adjusting a couple of elements: – Secondary winding pertains to 1.4 z / V. – ZD is mostly about 1V under the needed voltage.
For low voltage (about 5V or less) try replacing fast diode on output with Schottky diode. Optimum power in this source in an covered power supply and 230V power is 13W.
Transformer is a compact ferrite EE. Middle column includes a cross-section of 4.5 x 4.5 mm, air gap 0.4 mm. Primary carries 140 turns of wire diameter 0.15 mm. Secondary incorporates (for 19V output) 27 turns of wire 0.4 mm.
On account of the small power the secondary is not separated to a pair of regions. To begin with, I wrapped the whole primary. The levels are interlaced primary.
Between primary and secondary i employed protective shielding – copper tape and hooked up it to the frigid end of primary (needless to say it simply cannot establish a shorter turn!).
After that I wrapped solid isolation – 12 sheets of duct tape. Subsequently I wrapped secondary. In the event of difficulty disturbance include a noise reductions circuit and / or work with a capacitor roughly 1n / Y1 between primary and secondary section. Specific guidelines are available in the datasheet of TNY263 – TNY268.
The greater component the number, the increased the prospective power. Be aware additionally the current compilation of TinySwitch-III: TNY274 – TNY280.
From this series one can find IC’s making it possible for substantially more electrical power. They are able to moreover accommodate with schematic listed below, but the pinout are not the same.