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Power to the People - Switched-Mode Power Supply (SMPS) <140036-I>

Status: Finished
April 24, 2014

Submitted by: Reiner Müller

6 Watts wide range switching power supply with "Green-Mode Controller" TNY274P


- Worldwide application possible

- Open frame for installation in their own devices

- Low heat generation due to high efficiency

- Silent, no hum present

- Short-circuit proof output

- Low-cost, few components

- Conversion to 12 V output is also possible



- Power supply voltage: UAC = 85-265 V

- Frequency: fmains = 47 - 63 Hz

- DC voltage: UDC = 120-350 V

- Efficiency: teta = 80 % @ UAC = 230 V, Pout = 6 W

- Stand-by consumption: PStandby < 50 mW @ UAC = 265 V

- Output Voltage: Vout = Adjustable 5 V/3 V switchable

- Output current: Iout_max = 1.2 A @ Vout = 3 V/5 V

- Output power: Pout_max = 6 W

- Output Ripple: Uout_Ripple = 25 mV (ss) @ Iout = 1 A

- Ambient temperature: T = -10 ... +50 ° C

- Connection: Screw

- Module Size: 94 x 50.8 x 26 mm (L x W x H), with no spacers


General Linear power supplies are straightforward and therefore hardly need development effort. A linear power supply with 50 Hz transformer requires only a few standard components. It is relatively cheap to produce, sturdy, but at the same bulky, heavy and consumes a lot of energy. In order, for example, to achieve the above output power of 6 W, the transformer would have a calculated nominal power of 16 VA (PCB mount transformer with secondary 6 VAC/2666 mA) possess. In addition, would be a low-dropout voltage regulator with heat sink and a smoothing electrolytic capacitor of min. 2200 µF required. The selected transformer alone would have a size of 57 x 48 x 39 mm (L x W x H), and the efficiency of the entire circuit would be modest at ~ 38 %. Switching Power Supplies (flyback power supplies) in turn have specific advantages and disadvantages compared to conventional transformers. Switching power supplies are usually expensive in circuit design and require special components that are difficult to obtain. Higher complexity of the circuit means more components and therefore statistically higher probability of default. In addition, switching power supplies are the high frequencies of the flyback converter often sources of electromagnetic interference (EMC problem). This filters are necessary to bring the spurious emissions below the legal limit. At too low output load switching power supplies often tend to oscillate. Nevertheless outweigh the benefits, because primary switch mode power supplies are superior to the transformer power supplies technically far. On the one hand, the high efficiency is to be called up more than 80 % compared to the transformer. This hardly or only produces a low heat generated by the device, and therefore can be dispensed with a heatsink. On the other hand, switching power supplies a lower weight or volume for smaller transformers and smaller secondary-side filter capacitors, due to the high operating frequency of the flyback converter. Due to the reduced copper consumption of the transformer the price drops compared to a conventional regulated power supply. The biggest advantage, however, probably in large tolerance range of the input voltage and the variation/stability of the mains frequency. SMPS can for use with very different supply voltages (UAC = 85-265 V, f = 47 - 63 Hz) are designed without much additional effort. In addition, the operation with a correspondingly high d.c. voltage (U_DC = 120-350 V) is also possible. And finally carried out the direct conversion of the input voltage of, for example 265 VAC at an output voltage of 3.3 VDC. By using a modern, highly integrated 8-pin ICs, namely the TNY274P from the TinySwitch-III family of POWER INTEGRATION, it is possible to circumvent the above named circuitry disadvantages elegant. In combination with the transducer type 74001 with EE16 core of MYRRA and a few readily available standard components, it is possible to build a cheap and yet powerful switching power supply itself. Due to the ever increasing cost of electricity is the replacement of transformers with series regulator (heat sink) with smaller rated output through a switching power supply meaningful and economically, especially in permanent standby mode (P <50 mW @ 265 VAC).


Update 2014-04-28

Added new schematic and PCB

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