05.01.2015

Power adaptor peru

China Good Quality Universal AC Power Adapter, Switching Power Adapters and AC DC Switching Power Supply International Trade Site.
One of the major problems that is to be solved in an electronic circuit design is the production of low voltage DC power supply from Mains to power the circuit. Selection of the dropping capacitor and the circuit design requires some technical knowledge and practical experience to get the desired voltage and current. Before selecting the dropping capacitor, it is necessary to understand the working principle and the operation of the dropping capacitor. Effective impedance (Z) of the capacitor is determined by taking the load resistance (R) as an important parameter. Therefore if a 0.22 uF capacitor rated for 230 V is used, it can deliver around 15 mA current to the circuit.
The capacitance value determines the amount of ripples that appear in the DC output when the load takes current.
The ripple that appears in the capacitor is directly proportional to the load current and is inversely proportional to the capacitance value. A Zener diode can be used to generate a fixed voltage by passing a limited current through it using the series resistor (R). Power rating of the Zener is also an important factor to be considered while selecting the Zener diode. Where R is the value of resistor in ohms, V is the supply voltage and I is the allowable current in Amps.
Caution: Construction of this form of power supply is recommended only to those persons experienced or competent in handling AC mains.
No galvanic isolation from Mains.So if the power supply section fails, it can harm the gadget.
Sir with all due respects can i have an circuit of 12 vdc to 600vac 5ma inverter circuit sir. DC at this voltage is not that difficult–can be accomplished via a fly-back or boost type converter. Dear sir i assemble the same circuit, but the bleeder resistor and neutral resistor is burned out. I get to know to avoid this should use one capacitor in parallel to motor and it will avoid this tripping. If the load will draw a higher current, say 200mA, the output voltage will drop to compromise as the circuit has been designed to supply a maximum current of 140mA only.


This circuit is very higly dangerous especially for newcommers… Here in EU are security laws who luckely dont permit this schematic.
If we use a high watt resistor in series with AC, current will be reduced but huge quantity of heat will be generated and energy will be lost due to heat. The conventional method is the use of a step-down transformer to reduce the 230 V AC to a desired level of low voltage AC.
An ordinary capacitor will not do the job since the device will be destroyed by the rushing current from the mains. The peak inverse voltage is the maximum voltage a diode can withstand when it is reverse biased. The Zener output voltage is not seriously affected by R and the output remains as a stable reference voltage.
If the supply voltage is 18V, the voltage that is to be dropped across R to get 12V output is 6volts. A significant voltage drop (about 2 volts) occurs across the LED when it passes forward current. When the current is so high that the power dissipated by the bleeder resistor is higher than 1W, the bleeder resistor will burn out as well. The function of capacitor C1 is to only provide series reactance to step down AC mains, it is nothing to do with energy storage. Capacitor power supply eliminates the chance of heat generation and it gives some isolation from mains, until the dielectric of the capacitor breaks due to short circuit or high voltage.
The most simple, space saving and low cost method is the use of a Voltage Dropping Capacitor in series with the phase line. Therefore it is recommended to use a 470 nF capacitor rated for 400 V for such circuits to give required current. The power rating and the capacitance are two important aspects to be considered while selecting the smoothing capacitor. So a high value capacitor (1000 uF or 2200 uF) rated 25 volts or more must be used to get a ripple free DC output.
If a silicon diode is reverse biased, a point reached where its reverse current suddenly increases. If the maximum Zener current allowed is 100 mA, then R will pass the maximum desired output current plus 5 mA . Resistor R2 is the bleeder resistor that remove the stored current from the capacitor when the circuit is unplugged.


Maximum output current available will be 100 mA or less.So it is not ideal to run heavy current inductive loads.
Even after switching off the circuit, avoid touching the points around the dropping capacitor to prevent electric shock. The power supply unit must be isolated from the remaining part of the circuit using insulators. The Effective Impedance (Z), Rectance (X) and the mains frequency (50 – 60 Hz) are the important parameters to be considered while selecting the capacitor. Most of the general purpose rectifier diodes in the 1N series have 1 ampere current rating. If ripple is excess it will affect the functioning of the circuit especially RF and IR circuits. So the maximum power dissipation that can be allowed in a Zener is the Zener voltage multiplied by the current flowing through it. A current limiting resistor is necessary to protect LED from excess current that is flowing through it. The circuit should be housed in metal case without touching any part of the PCB in the metal case. Zener diodes are specially made to exploit the avalanche effect for use in ‘Reference voltage ‘regulators.
For example, if a 12V Zener passes 12 V DC and 100 mA current, its power dissipation will be 1.2 Watts. The value of this series resistor should be carefully selected to prevent damage to LED and also to get sufficient brightness at 20 mA current. A full wave rectifier comprising D1 through D4 is used to rectify the low voltage AC from the capacitor C1 and C2 removes ripples from the DC.
With this design, around 24 volts at 100 mA current will be available at the output.This 24 volt DC can be regulated to required output voltage using a suitable 1 watt Zener.
It is better to add a safety fuse in the phase line and an MOV across the phase and neutral lines as safety measure if there is voltage spike or short circuit in the mains.



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