Low Power Switching Power Supply 3.3V to 9V / 0.5A

The circuit is low powered power supply with switching voltage on a dedicated chip, MS34063. In comparison with linear stabilizers have a great impulse efficiency, lower weight and dimensions, but at the same time have some disadvantages, one of the key – an increased level of output voltage ripple.

The proposed Low Power switching power supply can be used to power various appliances multifunction handsets, gaming consoles, players, residential calls, etc., where the use of switching regulator power supply unit does not only more economical, but also greatly facilitate its temperature. It provides an output voltage of 3.3 … 9 V at 0.5 A. The amplitude of the output voltage ripple is 30 mV at maximum load current. Switching voltage power supply is protected against current overload and the appearance of the output power surges. This stabilizer can be used in the construction of new power sources, and to replace the linear regulator in a previously manufactured, for example, using the popular past-110LM transformers TCE, TCE-110L2 from semiconducting tube-TV. The newly manufactured power supplies use pulse voltage step-down transformer will use a lower capacity and overall dimensions. The scheme of the power supply is shown above.

Mains voltage across the fuse FU2 and push-button switch SB1 is fed to the primary winding of step-down transformer T1. Removed from its secondary winding voltage alternating current through self-healing fuse FU1 arrives at the bridge rectifier diode VD1. Ripple capacitor smooths the rectified voltage Coll. Capacitors C1, C2, C4-C6 suppress impulse noise coming from the network, and prevents the penetration of such interference in a network of switching regulator. It is made ​​by ASIC MS34063AR, which included lowering the standard scheme of the stabilized voltage converter. This chip is operational with an input voltage to 40 V and maximum current output of the transistor up to 1.5 A. The current consumption sostavlyaet4 own … 8 mA. Chip contains an overload protection and short circuit in the load circuit. Resistor R1 serves as a current sensor for this site. Conversion frequency set capacitor C7. The output voltage depends on the ratio of resistors R4 and series-connected resistors R2, R3, and it can be changed within 3.3 … 9 variable resistor R2. Choke L1 – funded, two-tier low-frequency filter inductors L2, L3 and capacitors C8-C13 smooths the output voltage ripple. HL1 LED indicates its presence. Zener diode VD3 (voltage stabilization 11V) protects loads from damage by high voltage fault in the stabilizer. When the output voltage exceeds 11 V the current through the zener diode rises sharply and self-healing fuse FU1 abruptly into a state of high resistance and limits the current flowing.