A few months ago, we have several threads about class D amp construction. I am really interested about class D because of its size vs power output but sourcing of parts is a bit of a challenge so its easier to abandon the idea of building one. I then bought a lower power, class AB chip, the LM1876 (DR20W). It is during our several Q&A’s with sir Dandy that I was informed of a class D amp kit from 1Diy.
Long story short, I get my birthday present last Nov 9 , a box with two of this amp. One assembled and the other one, I choose to build my self. The amp is based off TDA8920BTH, a 2 x 100W class D chip from NXP. I havent had the chance to hear sing though because I dont have a suitable PSU yet so for the meantime, lets just look at my build pics
The SMD TDA8920BTH soldered
Caps and tall components soldered
The output inductor, lets see how it performs. I dont have any test instrument here so I can show any pretty graps showing its performance. But I will sure tell you if (1) the IC blows, (2) the speaker blows (3) it stands the test
Protection circuit is onboard so if it does what it is intended for, we can at least have a peace of mind that our speaker is safe. PSU is one problem though. I have several trafo here but none is suitable for this amp, forcing me to build a regulated PSu using LM317 and LM337 and tip2955/tip3055 pass transistors.
I welcome suggestions about the PSU, much better if someone can point me to the right direction. Thank you
Power quality problems exist everywhere. In the USA, a study (2001) found out that the cost of poor power quality was around US$ 120 Billion. A similar survey in Europe found out that the cost for EU countries was Euro$ 150 Billion. Clearly, these numbers are staggering. A similar survey is being done in Asia, the results may come out later this year.
This we know for certain, power quality problems exist. The most common power quality problems are voltage sags (where the voltage value dips to less than 90% of its nominal value) and power interruptions (where the voltage is less than 10% of its nominal value).
Knowing the problem is the first step in finding the solution. Here are some power quality problems and solutions:
1) Over voltage/ under voltage. Utilities limit the voltage supply to consumers at plus 10% to minus 10% of the nominal voltage. If your area has over/under voltage, the first step is to inform the utility and the government regulator, the ERC (Energy Regulatory Commission) whose number appears in your electric bill. While waiting for the voltage to be corrected, an AVR (auto voltage regulator) can be used for your sensitive equipment (computers, etc).
2) Voltage sags. Also called fluctuations, those times when you see your lights flicker for a moment before your computer shuts down. This temporary dip in voltage (usually lasts less than 2 seconds) can be corrected by using an uninterruptible power supply (UPS). An AVR cannot be used in this case as the voltage dip is too fast for the AVR to correct. You can avoid the problem if your equipment has a built in universal power supply. These power supplies are so called because they can operate your equipment over a wide range of voltage. A laptop’s power supply is a good example: my laptop can operate from 100V to 240V (and with the frequency between 50 Hz to 60Hz).
3) Power interruptions. A UPS would be the most common solution to this problem. To minimize costs, I would recommend that only “critical” equipment be protected by UPS. The UPS is expensive as it comes with maintenance costs (like batteries) aside from its high initial costs. Sizing is important as size will determine the amount of protection that will be provided to the equipment.
There is no “one solution fits all” in power quality, as there is no “one drug cures all” in medicine. Costs and benefits must be carefully weighed before applying solutions. Ask your equipment provider for specifics before purchasing.
The passage of the Electric Power Industry Reform Act in 2001 ushered in a new era in the power industry. The law aims to, among other things, ensure the quality of the supply of electric power. Section 43 of this law creates a Distribution Code and a Grid Code that establishes performance standards for distribution utilities. In short, the power supply for consumers will be based on the standards set by the Code and monitored by the Energy Regulatory Commission.
So, how does this concern us?
Power supply in the past was only about reliability. Its either you have power or you don’t. Today, computers and other power sensitive devices are very common in households and in industrial facilities. These electronic devices operate on precise voltages and can malfunction if its supply voltage is not within its tolerance limit.
This problem has been addressed by standards set by stakeholders in the power industry. Here, the power generators, the appliance/equipment manufacturers and consumers have agreed upon electric supply standards that the generators will supply, that the equipment manufacturers will design around, which will benefit the consumer. These standards have become accepted in many countries, including the Philippines.
So, again, how does this concern us?
The Philippines, being a signatory to these international standards, have incorporated these in the Philippine Distribution Code. Section 3 deals with power quality – the standards of voltage the power supplier will provide the customer. These standards include:
1) Voltage supply shall be within plus 10% to minus 10% from the nominal voltage.
2) Voltage frequency shall be from 59.7Hz to 60.3 Hz
3) Voltage unbalance shall not be greater than 2.5%
4) Voltage harmonics shall not be greater than 5% THD
The standards above mean that if you have a 230V supply in your home, expect the voltage to vary anywhere from 207V (minus 10%) to 253 V (plus 10%) under normal conditions. Computer manufacturers like Intel and IBM as well as NEMA (National Electrical Manufacturers Association) have accepted this standard in designing their equipment. A computer or a motor will run indefinitely as long as the voltage is not higher that 10% (or lower than 10%) of their rated voltage.
Voltage harmonics is caused by electronic power supplies. This appears as “noise” which distorts the voltage waveform. Utilities are obliged to provide less that 5% THD to their customers, as equipment manufacturers design their equipment to tolerate this amount of distortion.
With the passage of the Distribution Code, the voltage supply standard in the Philippines is up to par with countries like Japan and the USA which adhere to the same set of standards. Many will say that the cost of power here is high but at least “high” can also describe the quality of power here.