30W precision switching regulated power supply composed of TOP224Y

The following introduces an isolated +15V, 2A (30W) precision switching regulated power supply composed of TOP224Y. The circuit is as shown in the figure. Its characteristic is that TL431 is used to replace the voltage regulator tube VDz2 in the sampling circuit, that is, the high-stability bandgap reference voltage Uref is used to replace the ordinary Zener voltage to achieve the technical specifications of the precision switching power supply. The excellent characteristics of this power supply are concentrated in that when the AC input voltage u changes from 85V to 265V, Sv=±0.2%; when the load current changes from 10% (0.2A) to 100% (2A), S1 also reaches ± 0.2%, comparable to linear integrated regulated power supplies. TIA31 (IC3) and optocoupler NEC2501 (IC2) form an electrically isolated external error amplifier, which is then used in conjunction with the internal error amplifier to finely adjust the control terminal current of TOP224Y (ICl), thereby greatly improving the voltage stabilization performance. The +15V regulated output is divided by R4 and R5 to obtain the sampling voltage, which is compared with the TL431 internal 2.5V reference voltage. The LED current is controlled by changing the K terminal potential, thereby adjusting the control terminal current Ic. R1 is the current limiting resistor for the LED and sets the DC gain of the control loop. R4 and C8 also determine the frequency characteristics of the external error amplifier.