Minggu, 10 Juli 2011
For those of you who like to dwell with digital circuits, the power supply circuit above can be selected to meet your supply for digital circuits. Actually you could make with no power supply using zener diode as a voltage stabilizer. But by using a zener diode voltage of 5V at least the value that you get really 5 volts. Power supply circuit above only supports the load circuits which only requires a supply current is not so great. This is due to limitations of power dispasi zener diodes and transistors are used.
Zener diodes have the characteristics similar to an ordinary diode. When given a zener diode forward bias it will function as the wire as well as the ordinary diode. But if the ordinary diodes can not withstand the voltage at a particular value when given reverse bias on the zener diode so it can be done. Value that can be stabilized voltage varies according to the specifications of the zener diode itself. On this occasion I will not explain the working principle of the circuit power supply because you can read it on my other posts that explain the workings of the power supply or a rectifier circuit.
Components used in power supply circuit with zener diodes above are as follows:
Step Down Transformer
Diode Bridge (Kumprok) | can also use regular diodes 4 pieces
Capacitors 1000 UF | The greater the value the better
Resistor 4.7 Kohm
Transistors 3904 | could also suit the needs of the other transistor
5 Volt Zener Diode
If you want to get a larger supply voltage of 5 volts then you just replace the zener diode as needed and use the ac voltage transformer keluarran a little bigger. For example to use a 9-volt zener diode, you can use an ac voltage 12 volts. See also the working principle of the rectifier, a simple power supply circuit and power supply with transformer CT.
Zener Diodes can be called Breakdown Voltage Diodes or Voltage Breakdown Diodes or Avalanche Diodes. The Zener diode has been an important component in both Voltage and Current Regulators. Prior to solid state components - a gas tube was used as a voltage regulator. Examples of gas tubes are OB2 and OB3.
There are two categories of Zener Diode. These are Voltage Breakdown Diodes and Avalanche Diodes.
The difference between the two depends on the level of doping. Voltage Breakdown Diodes operate within the region of 0 - 6 VDC. Avalanche Diodes operate within the region 5 - greater than 200 VDC. See manufacturers for the largest Zener Diode that they manufacture. Note the overlap of 1 Volt for both diodes. This overlap has been noted because the difference in action between Voltage Breakdown and Avalanche is different for every manufacturer and diode built that works in this region. If a Zener Diode is between 5 and 6 VDC then if can be described as either type.
Voltage Regulation Zener diodes are constructed to be voltage regulators, which means that they will operate at an approximate but pre-determined voltage.
They operate as a voltage regulator because they maintain a pre-determined voltage despite changes in zener current. This is only true if the current remains within the specifications engineered into the Zener.
The external circuit components must be within specifications if the Zener diode is to function properly. This is usually a single resistor.
Minimum Resistance: This resistance has a minimum value, which permits a maximum zener current, thus a maximum zener voltage. If this resistance were to reduce below this value then the zener current would burn out the diode.
Maximum Resistance: This resistance also has a maximum value, however, increasing the resistance only decreases the current, and no damage will occur to the Zener. What does happen is that the Zener no longer regulates voltage but will experience large voltage changes for minimum current changes. These voltages will be less than the minimum zener voltage and normally should not damage any associated circuitry.
Regulation: A zener diode is normally connected in parallel with the load.
If the input voltage changes, and in this example, increases, then the circuit, acting as voltage divider will see an increase in voltage across the load. This increase is also in parallel with the Zener, which because of the increase in voltage will increase Zener current. This increase in current is felt through the series resistance, dropping more voltage, thus returning the load voltage to near original value.