The rectifier is good enough if its a small ripple voltage, but there are stability issues. If the voltage of electricity rise / fall, then the output voltage will also go up / down. Like the rectifier circuit above, if the current higher voltage dc discharge was also decreased. For some applications this voltage changes quite annoying, so it requires an active component that can regulate the output voltage becomes stable.
The most simple regulator circuit shown in Figure 6. In this circuit, zener works on the breakdown region, thus producing the same output voltage with a zener voltage or Fout = VZ. However, this circuit is only useful if the load current not exceeding 50mA.
picture-6 :
zener regulator
The principle of such a power supply circuit is called a shunt regulator, one of her trademark is a component of the regulator in parallel with the load. Another feature of the shunt regulator is susceptible to short-circuit. Notice when Fout connected short (short-circuit) then the current is fixed I = Vin/R1. In addition to a shunt regulator, there is also a series called by the regulator. The main principle of such series regulator circuit in Figure 7 below. In this circuit output voltage is:
Vout = VZ + VBE
VBE is the base-emitter voltage of transistor Q1 of magnitude between 0.2 – 0.7 volts depending on the type of transistor used. By ignoring the IB currents flowing in the transistor base, to determine the magnitude of resistance R2 is required is:
R2 = (Vin – Vz)/Iz
Iz is the minimum flow required by the zener diode to achieve the zener breakdown voltage. These large currents can be detected from a datasheet which amount to approximately 20 mA.
regulator zener follower
If the supply current required is greater, of course the base of IB in the current calculation circuit above can not be ignored anymore. Where such a known, large currents will be proportional to IC flows dirumskan with IB or IC = BIB. For such purpose, the transistor Q1 is used can be replaced with Darlington tansistor which typically have large b values. With a Darlington transistor, the current small base that could produce a greater flow of IC.
Techniques that better regulation is to use the Op-Amp to drive the transistor Q, as in a series of 8 images. Zener diodes are not here to give feedback directly to the transistor Q, but as a reference voltage for the op-amp IC1. Negative feedback on the op-amp pins are excerpts from the voltage regulator out, namely:
Vin(-) = (R2/(R1+R2)) Vout
If the stress out Fout ascending, then the voltage Vin (-) will also be rising until the voltage is equal to the reference voltage VZ. And vice versa if the voltage decreases Fout out, for example because of supply current to the load increases, op-amp will keep the stability of the reference point by giving the current VZ IB to the transistor Q1. So that at any time maintaining the stability of op-amp:
Vin(-) = Vz
regulator with Op-amp
For example 7805 is a voltage regulator to get a 5 volt, 12 volt voltage regulator 7812 and beyond. While such 79XX series is the 7905 and 7912 which are respectively the negative voltage regulator 5 and 12 volt.
Apart from the fixed voltage regulators have a voltage regulator IC also can be arranged. The principle is the same as OP-amp regulator packaged in a single IC for regulators such as LM317 LM337 variable positive and negative variable for the regulator. The difference between resistors R1 and R2 are outside the IC, so that the output voltage can be adjusted via external resistors.
It’s just important to know that with the IC regulator circuit can work, tengangan input must be greater than the output voltage regulatornya. Usually the difference in voltage Vin to Fout recommended in the datasheet component. Use heatshink (Aluminum cooling) is recommended if these components to be used to supply a large current. In the datasheet, these components can pass through the flow reaches a maximum of 1 A.
If the supply current required is greater, of course the base of IB in the current calculation circuit above can not be ignored anymore. Where such a known, large currents will be proportional to IC flows dirumskan with IB or IC = BIB. For such purpose, the transistor Q1 is used can be replaced with Darlington tansistor which typically have large b values. With a Darlington transistor, the current small base that could produce a greater flow of IC.
Techniques that better regulation is to use the Op-Amp to drive the transistor Q, as in a series of 8 images. Zener diodes are not here to give feedback directly to the transistor Q, but as a reference voltage for the op-amp IC1. Negative feedback on the op-amp pins are excerpts from the voltage regulator out, namely:
Vin(-) = (R2/(R1+R2)) Vout
If the stress out Fout ascending, then the voltage Vin (-) will also be rising until the voltage is equal to the reference voltage VZ. And vice versa if the voltage decreases Fout out, for example because of supply current to the load increases, op-amp will keep the stability of the reference point by giving the current VZ IB to the transistor Q1. So that at any time maintaining the stability of op-amp:
Vin(-) = Vz
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great post as usual!
thanks,.
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