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MC1466L Driven Power Supply with 30 Volts at 2 Amperes

2014-11-16 07:13  
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Figure 1 

The circuit has been designed to produce a power supply that will generate 30 volts with 2 A current by utilizing the MC1466L integrated circuit with the aid of multiple Darlington transistors.

MC1466L – an integrated circuit used as voltage and current regulator while providing a power supply performance due to its features such as adjustable internal current source, internal voltage reference, short circuit protection, good current regulation, output voltage adjustable to zero volts, good load voltage regulation, good line voltage regulation, and voltage/current regulation with automatic crossoverMPSL01 – anNPNamplifier designed for high voltage, general purpose amplifiers and gas discharge display driving, enclosed in a TO-92 package2N4923 – medium-power plasticNPNSilicon Transistor used for amplifier applications, switching, and driver circuits due to its high performance, availability of lead-free package, specific gain at 1 A, excellent safe operating area, excellent power dissipation due to thermopad construction, and low saturation voltage2N3055 – a complementary Silicon Epitaxial-Base planarNPNtransistor mounted in Jedec TO-3 metal case for use as power transistor

One of the basic prerequisite in the design of a laboratorial power supply is to provide operating voltage and current needed by standard equipments while affording good stabilization, small ripple, low noise, and low output resistance. All of these requirements are achieved by the circuit. Most of the power supplies are equipped with electronic safety protection to prevent self destruction from short circuit in their output. The large value of current output can be regulated in the circuit ranging from 0 A to 2 A, regardless of the bigger requirement by the load. While the circuit employs its auto protection, it simultaneously protects the component that it supplies especially when the component has the inclination of drawing large currents than the estimated value. The circuit can also be utilized to control the elements by recording the characteristics of voltage or current which makes it suitable as an ideal source of constant voltage and current that is capable of supplying continuously regulated 30 Vdc and 2 A without step down aid.

Two secondary coils comprise the transformer T1 with the A coil responsible for supplying high current to the output circuit through the bridge rectifier consisting of diodes D1 to D4 and capacitor C2 while the B coil supplies the IC1 after the rectification by C4 and D1, which is stabilized by C5 and D7. The current is passing throughLEDD6 which provides an indication during normal operation. The frequency in the internal circuit of IC1 is compensated by C7 while the combination of R8, D8, and D9 protects the IC1 from peak voltages of the circuit. The output voltage is being regulated by the presence of resistor R3 as required while resistor R8 acts as a current limiter in the circuit output.

The output of the power supply contains multiple Darlington transistors that are comprised by Q1 & Q2, and Q3 & Q4 that are connected in parallel. A Darlington pair is designed in such a way that the collectors of both transistors are attached together and the emitter of the first transistor is directly coupled to the base of the second or output transistor. The base current of the output transistor is equal to the emitter current of the input transistor. When several transistors are used, it can form a cascade connection and the total current amplification factor will be very high since it is a product of current amplification factor of respective transistors.

The resistors R14 and R15 maintain the similarity of currents in the collector while resistors R10 to R12 provides the stability of DC in the circuit output. This operation has basic importance in high temperature applications where the reverse currents can become significant. The frequency in the output amplifier of IC1 is compensated by the combination of C10, C11, and R9 while the protection is provided by D13. While the output current is passed through R19, the voltage is dropping gradually at a favorable percentage while being fed to pin 11 of IC1. The second input is directed to pin 10 with a constant voltage, with the value being regulated by R8 in reference to the largest value of current output. In the case when the output current exceeds this value, the voltage drops via R19 which is fed to the pin 10 which activates the differential amplifier of IC1 and prevents increasing further the output current. The capacitors C13, C14, and C15 provide the separation in the output while the protection from reverse voltage is achieved by D15.

The measurement of the output voltage and the current can be seen via the volt ammeter VA1 which depends on the position of contact made by switch S2. In the position of the switch in the figure, the current is measured by taking the voltage drop across the R19 via the R17 and R18. On the other hand, to measure the voltage, the switch is moved to the other position to take a sample of output voltage. the regulation of micrometer will originate from R21 and R22.

A small heatsink should be placed with transistor Q2 as well as with Q3 and Q4, having a thermic resistance of 2.6o C/W. The use of a digital multimeter connected to the output can provide an essential aid in regulating the power supply. Finally, the voltage and current can be regulated manually by adjusting the trimmer together with the potentiometer in the circuit.


Figure 2 

Power supplies are designed to work on equipments depending on the required voltage and current rating. Some modern power supply used in computers functions in a switched-mode where it converts 110 V to 220 V AC to DC voltages. In arc welding, power supplies are used to provide electricity to melt the surfaces of the metals in order to join them together. In Ac adapters, power supplies are used as linear or as switched-mode like a transformer in some cases.


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