The article describes a simple regulated switching power supply (SMPS), which can be placed in body size of a matchbox. The device has high specific capacity, good reproducibility, and is not afraid of overcurrent.
Description miniature SMPS have been published on the Internet. As a rule, it is devices with limited power output. For example, the predecessor of the SMPS in a matchbox" was given in the load capacity up to 0,63 W, being one of the most powerful sources among those that fit in a matchbox or in the dimensions of the battery "Krona". In addition, these sources had low efficiency, typically not exceeding 35 %.
The proposed flyback SMPS can also be put into a matchbox, but its output power 15 times, and the efficiency is 2.5 times more than that of the first embodiment. To achieve such a high energy performance managed through the use of specialized chip TNY255P TinySwitch family firm Power integrations. SMPS stabilizes the output voltage has overload protection and short circuit in the load by skipping pulses, and used the chip contains nodes overheating protection.
Main technical characteristics
Supply voltage AC, .............................220±20%
Power supply voltage frequency, Hz.....................................................40...400
Power consumption with no load, W, not more 0,31 ...
Conversion frequency, kHz.................................................................115...140
Nominal output voltage, V................................................9
The maximum output power, W...............................................10
Maximum efficiency, %.............................................................................88
Specific power, W/dm3...................................................................300
Weight (without housing), g, not more...........................................................28
Fig. 1
The SMPS circuit shown in Fig. 1. Fuse FU1 protects against accidents. The thermistor RK1 limits the pulse charging current of the capacitor C2 to secure for the diode bridge values VD1, and together with the capacitor C1 forms an RC filter, used to reduce impulse noise penetrating from the SMPS to the network. VD1 diode bridge rectifies the mains voltage, the capacitor C2 - smoothing. The emission voltage of the primary winding of the transformer T1 reduces the damping circuit R1C5VD2. The capacitor C4 is a power supply filter, which is supplied with the internal elements of the circuits DA1, its nominal capacity may be in the range of 0,1...the 4.7 UF.
The output rectifier is assembled on the diode the Schottky VD3, output voltage ripple smoothing LC filter C6C7L1C8. Elements R2, R3, and VD4 U1 provide together with chip DA1 stabilization of the output voltage when the load current and line voltage. Circuit activation is performed on the HL1 led and the current limiting resistor R4.
Applied fixed resistors MLT, C2-23, P1-4, trimmer - N-1 Bourns company or domestic analogue SDR-19a, oxide capacitors - import, S1, Sz, and C5 - high voltage ceramic CD2200Z5V, DEBB33D222KA2B, C4, C7, C8 - K10-506. The series thermistor NTC (negative TCR) - SCK-103. Chip TNY255P interchangeable on TNY255G, TNY256P or TNY256G, diode HER208 - HER106, HER107, HER206, HER207, 1N4937, FR306 or BY399, diode 1N5822 - SR360, 31DQ04, 31DQ06, 90SQ045. Zener XA can be replaced by a Zener XA, XA, and the optocoupler RS - LTV817, RS, LTV816. Led - any miniature, preferably blue or green glow. Fuse FU1 - constructive, it is formed on a printed circuit Board conductor, it is possible to replace cut, copper wires, such as sew-2, with a diameter of 0.03 mm.
For the manufacture of the transformer applied magnetic armour B18 (without podstroechnik) of ferrite 2000NM. The primary winding has 182 round wire with a diameter of 0.11 mm, and the secondary consists of 20 turns of wire with a diameter of 0.6 mm Between the windings it is necessary to lay two layers of Mylar or leacockanimal tape, to impregnate them with paraffin to reduce acoustic noise. Between the cups of the magnetic circuit is necessary to make a gap of 0.16...0.23 mm, using a gasket made of PTFE, fiberglass, or, in extreme cases, cardboard. The inductor is wound on the magnetic core size CHH ferrite 2000NM and has 16 turns of wire with a diameter of 0.6 mm at an output current of up to 200...300 mA and 3...4 round wire with a diameter of 0.8 mm at a current of 1.1 A. Sharp edges of the magnetic core must be dulled with sandpaper and wrap a layer leacockanimal tape. For winding of the transformer and inductor should be applied to the wire marks sew-2, PATM, PETV-1, petv-2, PAT-200-1.
Fig. 2
Drawing of the PCB shown in Fig. 2, it is made of one-sided foil fiberglass with a thickness of 1...1.5 mm. Chip installed in the panel, cups of the magnetic core is compressed between a and fastened to the circuit Board with the two brass screws, spun from opposite sides in a brass bushing. All resistors and diodes are mounted perpendicular to the Board. Appearance fees collected are shown in Fig. 3. After checking and establishing its place in the body of insulating material.
Fig. 2
The establishment of the SMPS is reduced to accurate setting of the output voltage trimming resistor R3.
Author: E. Moscato, Taganrog, Rostov region