Switching Power Supply

Please 'Boom' Responsibly As most of you have noticed, the noise ordinances have become much tougher lately. Most of this is due to idiots, yes IDIOTS, who drive through residential areas with their windows down while their system is playing at full power. To make things worse, the music they listen to has all sorts of foul language that's not suitable for small children, (who may be playing outside). There are even a few people, who are even beyond idiot status, that play their systems at full power through residential areas after 10:00 PM (when many people go to bed). I don't believe that this type of behavior is good for the industry. If the fines get too stiff, people will stop buying large systems. If this happens, more people will get out of car audio (who wants a mediocre system). People get interested in things because they're exciting. A deck and four 6.5" speakers are not going to interest many of the younger car audio enthusiasts. If car audio enthusiasts keep annoying more and more people, the fines will keep getting tougher. All of this will only reduce interest in the equipment that fuels the industry. If you want to listen to your system at full volume, get out on the highway where there's little chance of bothering anyone. When you get to a red light, turn it down. If the only thing attractive about you is your 'system', you have some work to do. Bottom line... Think about what you're doing. Think about other people. It's not the end of the world if you have to turn the volume down for a little while.

Switching Power Supply:: As we all know, the vehicle's charging system produces less than 15 volts (generally between 13.5 and 14 volts when the engine is running). This is simply not enough for many uses. For amplifiers and high output preamplifiers, you need more voltage. To boost the voltage, we use a switching power supply. The most common type of switching power supply uses a transformer to boost voltage. A less common method uses diodes and capacitors.; A switching power supply (also known as a switch mode power supply or SMPS) pulses a DC current through the primary windings of a transformer at very high frequency (~20,000 - 50,000 pulses per second). This creates an alternating magnetic field around the primary winding and the core of the transformer. Since the secondary winding is also wrapped around the core and is in close proximity to the primary windings, a voltage is induced in the secondary windings. The secondary winding may or may not be electrically connected to any point of the source of the DC power. The output of the secondary is an AC voltage. In most power supplies, the AC output of the transformer is rectified by using diodes and therefore provides DC voltage at its outputs. This rectified output voltage is commonly reffered to as 'rail voltage' in amplifiers.; The diagram above shows a simplified version of the type of transformer that is commonly used in car audio equipment. It consists of a primary winding, a secondary winding and a toroidal core. This type of transformer is lightweight, compact and very efficient. The transformers can be much smaller than those used in home audio equipment becaust the operating frequency is much higher. Most home equipment simply has its power transformer connected to the AC mains supply. The mains in the US runs at 60hz (60 cycles per second). On the other side of the pond, the mains operate at 50 hz. At 50 or 60 hz, you need a much larger transformer. With a switching power supply, the engineer can pick any frequency he or she desires (after carefully considering all of the different variables).; The diagram above shows a simplified version of a switching power supply. In a typical design, Point "b" is connected to a source of power, such as the vehicle's battery. Points "a" and "c" will be alternately connected to ground at a high frequency (sorta like an electronic see-saw) through high speed MOSFET switching transistors. Point "x" would be the ground for the secondary of the transformer and can be completely isolated from the vehicle's ground. Point "y" would be the positive output rail voltage (referenced to the secondary ground). Point Z is the negative rail voltage. The diodes are used to rectify the AC output from the transformer. The capacitors are used to reduce the ripple on the output of the power supply.

You should remember:
1.The primary winding of the transformer is driven with pulsed D.C..
2.The pulsed D.C. creates an alternating magnetic field in the core.
3.The secondary is wound around the core which causes a voltage to be induced in its windings.
4.The output of the secondary is an A.C. voltage.
5.The A.C. is rectified into pulsed D.C. through the diodes.
6.Capacitors smooth the pulsed D.C.

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