From: "Saved by Internet Explorer 11" Subject: New Page 1 Date: Thu, 23 Jan 2014 14:27:00 -0800 MIME-Version: 1.0 Content-Type: multipart/related; type="multipart/alternative"; boundary="----=_NextPart_000_0000_01CF1847.2DB169A0" X-MimeOLE: Produced By Microsoft MimeOLE V6.1.7601.17609 This is a multi-part message in MIME format. ------=_NextPart_000_0000_01CF1847.2DB169A0 Content-Type: image/gif Content-Transfer-Encoding: base64 Content-Location: http://pagead2.googlesyndication.com/pagead/imp.gif?client=ca-lycos_tripod&channel=TRI_below_728x90&event=noscript R0lGODlhAQABAID/AP///wAAACH5BAEAAAAALAAAAAABAAEAQAICRAEAOw== ------=_NextPart_000_0000_01CF1847.2DB169A0 Content-Type: text/css; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Location: res://ieframe.dll/NewErrorPageTemplate.css body { margin: 0em; color: rgb(87, 87, 87); font-family: "Segoe UI", = "verdana", "arial"; background-repeat: repeat-x; background-color: = white; } .mainContent { width: 700px; margin-top: 80px; margin-right: 120px; margin-left: = 120px; } .title { color: rgb(39, 120, 236); font-family: "Segoe UI", "verdana"; = font-size: 38pt; font-weight: 300; margin-bottom: 20px; vertical-align: = bottom; position: relative; } .errorExplanation { color: rgb(0, 0, 0); font-family: "Segoe UI", "verdana", "arial"; = font-size: 12pt; text-decoration: none; } .taskSection { margin-top: 20px; margin-bottom: 40px; position: relative; } .tasks { color: rgb(0, 0, 0); padding-top: 5px; font-family: "Segoe UI", = "verdana"; font-size: 12pt; font-weight: 200; } li { margin-top: 8px; } .diagnoseButton { font-size: 9pt; } .launchInternetOptionsButton { font-size: 9pt; } .webpageURL { direction: ltr; } .hidden { display: none; } a { color: rgb(0, 102, 204); font-family: "Segoe UI", "verdana", "arial"; = font-size: 11pt; text-decoration: none; } a:hover { text-decoration: underline; } ------=_NextPart_000_0000_01CF1847.2DB169A0 Content-Type: application/octet-stream Content-Transfer-Encoding: quoted-printable Content-Location: res://ieframe.dll/errorPageStrings.js =EF=BB=BF//Split out for localization. var L_GOBACK_TEXT =3D "Go back to the previous page."; var L_REFRESH_TEXT =3D "Refresh the page."; var L_MOREINFO_TEXT =3D "More information"; var L_OFFLINE_USERS_TEXT =3D "For offline users"; var L_RELOAD_TEXT =3D "Retype the address."; var L_HIDE_HOTKEYS_TEXT =3D "Hide tab shortcuts"; var L_SHOW_HOTKEYS_TEXT =3D "Show more tab shortcuts"; var L_CONNECTION_OFF_TEXT =3D "You are not connected to the Internet. = Check your Internet connection."; var L_CONNECTION_ON_TEXT =3D "It appears you are connected to the = Internet, but you might want to try to reconnect to the Internet."; //used by invalidcert.js var L_CertUnknownCA_TEXT =3D "The security certificate presented by this = website was not issued by a trusted certificate authority."; var L_CertExpired_TEXT =3D "The security certificate presented by this = website has expired or is not yet valid."; var L_CertCNMismatch_TEXT =3D "The security certificate presented by = this website was issued for a different website's address."; var L_CertRevoked_TEXT =3D "This organization's certificate has been = revoked."; var L_CertSigFailed_TEXT =3D "The security certificate presented by this = website is not secure."; var L_PhishingThreat_TEXT =3D "Phishing threat: This is a phishing = website that impersonates a trusted website to trick you into revealing = personal or financial information."; var L_MalwareThreat_TEXT =3D "Malicious software threat: This site = contains links to viruses or other software programs that can reveal = personal information stored or typed on your computer to malicious = persons."; var L_TopFrameUnsafe_TEXT =3D "This website has been reported as = unsafe"; var L_ContentUnsafe_TEXT =3D "Content on this website has been reported = as unsafe"; var L_Content_TEXT =3D "Hosted by: "; var L_ACR_Title_TEXT =3D "We were unable to return you to %s."; var L_ACR_TitleFallback_TEXT =3D "We were unable to return you to the = page you were viewing."; var L_ACR_ReturnTo_TEXT =3D "Try to return to %s"; var L_ACR_ReturnToFallback_TEXT =3D "Try to return to the page you were = viewing"; var L_ACR_GoHome_TEXT =3D "Go to your home page"; //used by new dnserror.htm var L_INTERNET_NOT_CONNECTED_TEXT =3D "You\u2019re not connected to a = network"; var L_INTERNET_CONNECTED_TEXT =3D "This page can\u2019t be displayed"; var L_TLS_SSL_TEXT =3D "Make sure TLS and SSL protocols are enabled. Go = to Tools > Internet Options > Advanced > Settings > Security"; // Used by IM DNS error page var L_THIS_PAGE_CANT_BE_DISPLAYED_TEXT =3D "This page can\u2019t be = displayed"; var L_YOU_ARE_NOT_CONNECTED_TEXT =3D "You\u2019re not connected"; // Used by IExtensionValidation error page var L_ActiveXUnsafe_TEXT =3D "%s blocked this website"; var L_ActiveXUnsafe_Frame_TEXT =3D "%s blocked content on this website"; var L_ActiveXUnsafe_Explain_TEXT =3D "%s blocked this site because it = might contain threats to your PC or your privacy."; var L_ActiveXUnsafe_Hosted_TEXT =3D "Hosted by: %s"; ------=_NextPart_000_0000_01CF1847.2DB169A0 Content-Type: application/octet-stream Content-Transfer-Encoding: quoted-printable Content-Location: res://ieframe.dll/httpErrorPagesScripts.js =EF=BB=BF function isExternalUrlSafeForNavigation(urlStr) { var regEx =3D new RegExp("^(http(s?)|ftp|file)://", "i"); return regEx.exec(urlStr); } function clickRefresh() { var location =3D window.location.href; var poundIndex =3D location.indexOf('#'); if (poundIndex !=3D -1 && poundIndex+1 < location.length && = isExternalUrlSafeForNavigation(location.substring(poundIndex+1))) { window.location.replace(location.substring(poundIndex+1)); } } function navCancelInit() { var location =3D window.location.href; var poundIndex =3D location.indexOf('#'); if (poundIndex !=3D -1 && poundIndex+1 < location.length && = isExternalUrlSafeForNavigation(location.substring(poundIndex+1))) { var bElement =3D document.createElement("A"); bElement.innerText =3D L_REFRESH_TEXT; bElement.href =3D 'javascript:clickRefresh()'; navCancelContainer.appendChild(bElement); } else { var textNode =3D document.createTextNode(L_RELOAD_TEXT); navCancelContainer.appendChild(textNode); } } function expandCollapse(elem, changeImage) { if (document.getElementById) { ecBlock =3D document.getElementById(elem); if (ecBlock !=3D undefined && ecBlock !=3D null) { if (changeImage) { elemImage =3D document.getElementById(elem + "Image"); } if (!changeImage || (elemImage !=3D undefined && elemImage !=3D null)) { if (ecBlock.currentStyle.display =3D=3D "none" || = ecBlock.currentStyle.display =3D=3D null || ecBlock.currentStyle.display = =3D=3D "") { ecBlock.style.display =3D "block"; if (changeImage) { elemImage.src =3D "up.png"; } } else if (ecBlock.currentStyle.display =3D=3D "block") { ecBlock.style.display =3D "none"; if (changeImage) { elemImage.src =3D "down.png"; } } else { ecBlock.style.display =3D "block"; if (changeImage) { elemImage.src =3D "up.png"; } } } } } } function initHomepage() { DocURL=3Ddocument.location.href; var poundIndex =3D DocURL.indexOf('#'); if (poundIndex !=3D -1 && poundIndex+1 < location.length && = isExternalUrlSafeForNavigation(location.substring(poundIndex+1))) { protocolIndex=3DDocURL.indexOf("://", 4); serverIndex=3DDocURL.indexOf("/", protocolIndex + 3); BeginURL=3DDocURL.indexOf("#",1) + 1; urlresult=3DDocURL.substring(BeginURL, serverIndex); if (protocolIndex - BeginURL > 7) urlresult=3D""; displayresult=3DDocURL.substring(protocolIndex + 3, serverIndex); } else { displayresult =3D ""; urlresult =3D ""; } var aElement =3D document.createElement("A"); aElement.innerText =3D displayresult; aElement.href =3D urlresult; homepageContainer.appendChild(aElement); } function initConnectionStatus() { if (navigator.onLine) { checkConnection.innerText =3D L_CONNECTION_ON_TEXT; } else { checkConnection.innerText =3D L_CONNECTION_OFF_TEXT; } } function initGoBack() { if (history.length < 1) { var textNode =3D document.createTextNode(L_GOBACK_TEXT); goBackContainer.appendChild(textNode); } else { var bElement =3D document.createElement("A"); bElement.innerText =3D L_GOBACK_TEXT ; bElement.href =3D "javascript:history.back();"; goBackContainer.appendChild(bElement); } } function initMoreInfo(infoBlockID) { var bElement =3D document.createElement("A"); bElement.innerText =3D L_MOREINFO_TEXT; bElement.href =3D "javascript:expandCollapse(\'infoBlockID\', true);"; moreInfoContainer.appendChild(bElement); } function initOfflineUser(offlineUserID) { var bElement =3D document.createElement("A"); bElement.innerText =3D L_OFFLINE_USERS_TEXT; bElement.href =3D "javascript:expandCollapse('offlineUserID', true);"; offlineUserContainer.appendChild(bElement); } function initUnframeContent() { var location =3D window.location.href; var poundIndex =3D location.indexOf('#'); if (poundIndex !=3D -1 && poundIndex+1 < location.length && = isExternalUrlSafeForNavigation(location.substring(poundIndex+1))) { document.getElementById("whatToDoIntro").style.display=3D""; document.getElementById("whatToDoBody").style.display=3D""; } } function removeNoScriptElements() { var noScriptElements =3D document.getElementsByTagName("noscript"); for (var i =3D noScriptElements.length - 1; i >=3D 0; i--) { var bElement =3D noScriptElements[i]; if (bElement !=3D=3D undefined && bElement !=3D=3D null) { bElement.removeNode(true); } } } function makeNewWindow() { var location =3D window.location.href; var poundIndex =3D location.indexOf('#'); if (poundIndex !=3D -1 && poundIndex+1 < location.length && = isExternalUrlSafeForNavigation(location.substring(poundIndex+1))) { window.open(location.substring(poundIndex+1)); } } function setTabInfo(tabInfoBlockID) { var bPrevElement =3D document.getElementById("tabInfoTextID"); var bPrevImage =3D document.getElementById("tabInfoBlockIDImage"); if (bPrevElement !=3D null) { tabInfoContainer.removeChild(bPrevElement); } if (bPrevImage !=3D null) { tabImageContainer.removeChild(bPrevImage); } var bElement =3D document.createElement("A"); var bImageElement =3D document.createElement("IMG"); var ecBlock =3D document.getElementById(tabInfoBlockID); if ((ecBlock !=3D undefined && ecBlock !=3D null) && (ecBlock.currentStyle.display =3D=3D "none" || = ecBlock.currentStyle.display =3D=3D null || ecBlock.currentStyle.display = =3D=3D "")) { bElement.innerText =3D L_SHOW_HOTKEYS_TEXT; bImageElement.alt =3D L_SHOW_HOTKEYS_TEXT; bImageElement.src=3D"down.png"; } else { bElement.innerText =3D L_HIDE_HOTKEYS_TEXT; bImageElement.alt =3D L_HIDE_HOTKEYS_TEXT; bImageElement.src=3D"up.png"; } bElement.id =3D "tabInfoTextID"; bElement.href =3D "javascript:expandCollapse(\'tabInfoBlockID\', false); = setTabInfo('tabInfoBlockID');"; bImageElement.id=3D"tabInfoBlockIDImage"; bImageElement.border=3D"0"; bImageElement.className=3D"actionIcon"; tabInfoContainer.appendChild(bElement); tabImageContainer.appendChild(bImageElement); } function launchInternetOptions() { window.external.msLaunchInternetOptions(); } function diagnoseConnection() { window.external.DiagnoseConnection(); } function diagnoseConnectionAndRefresh() { window.external.DiagnoseConnection(); if (navigator.onLine) { clickRefresh(); } } function getInfo() { checkConnection(); if (document.addEventListener) { addEventListener("offline", reportConnectionEvent, false); } else { attachEvent("onoffline", reportConnectionEvent); } document.body.ononline =3D reportConnectionEvent; document.body.onoffline =3D reportConnectionEvent; } function checkConnection() { var newHeading =3D document.getElementById("mainTitle"); var notConnectedTasks =3D document.getElementById("notConnectedTasks"); var cantDisplayTasks =3D document.getElementById("cantDisplayTasks"); if (navigator.onLine) { document.title =3D L_INTERNET_CONNECTED_TEXT; newHeading.textContent =3D L_INTERNET_CONNECTED_TEXT; addURL(); notConnectedTasks.style.display =3D "none"; cantDisplayTasks.style.display =3D ""; } else { document.title =3D L_INTERNET_NOT_CONNECTED_TEXT; newHeading.textContent =3D L_INTERNET_NOT_CONNECTED_TEXT; notConnectedTasks.style.display =3D ""; cantDisplayTasks.style.display =3D "none"; } } function reportConnectionEvent(e) { if (!e) e =3D window.event; if ('online' =3D=3D e.type) { setTimeout ( "clickRefresh()", 1000 ); } else if ('offline' =3D=3D e.type) { checkConnection(); } else { checkConnection(); } } function addURL() { var urlResult =3D ""; var DocURL =3D document.location.href; var urlPlaceholder =3D document.getElementById("webpage"); var beginIndex =3D DocURL.indexOf('#') + 1; if (DocURL.indexOf("file://", beginIndex) =3D=3D -1) { var protocolEndIndex =3D DocURL.indexOf("://", beginIndex); var endIndex=3DDocURL.indexOf("/", protocolEndIndex + 3); urlResult =3D DocURL.substring(beginIndex, endIndex); } urlPlaceholder.innerText =3D urlResult + " "; } function addDomainName() { var domainNamePlaceholder =3D document.getElementById("DomainName"); domainNamePlaceholder.innerText =3D findValue("DomainName=3D") + " "; } function addProxyDetail() { var proxyDetailPlaceholder =3D document.getElementById("ProxyDetail"); proxyDetailPlaceholder.innerText =3D findValue("ProxyDetail=3D"); } function findValue(key) { var value =3D ''; DocQuery =3D document.location.search; BeginString =3D DocQuery.indexOf(key); if (BeginString > 0) { BeginString +=3D key.length; EndString =3D Math.max(0, Math.min(DocQuery.indexOf("&", BeginString), = DocQuery.indexOf("#", BeginString))); if (EndString > 0) { value =3D DocQuery.substring(BeginString, EndString); } else { value =3D DocQuery.substring(BeginString); } } return value; } function isHTTPS(cantDisplayTasks) { var DocURL =3D document.location.href; var poundIndex =3D DocURL.indexOf('#'); var protocolIndex =3D DocURL.indexOf("https://", poundIndex); if (protocolIndex>poundIndex) { var bElement =3D document.createElement("li"); bElement.textContent =3D L_TLS_SSL_TEXT; cantDisplayTasks.appendChild(bElement); } } ------=_NextPart_000_0000_01CF1847.2DB169A0 Content-Type: multipart/alternative; boundary="----=_NextPart_001_0009_01CF1847.2DB169A0" ------=_NextPart_001_0009_01CF1847.2DB169A0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Content-Location: file://C:\Users\R&D 1\Documents\My Downloads\Do It Yourself Car Amplifier.htm =20 =20 =20 =20 =20 New Page 1 =20 =20

Do It Yourself Car Amplifier

This article is for = those who=20 wants to make their own car amplifier. The = basics of calculation will be discussed below. If you have understand it you will be able to make car = amplifier=20 yourself.

THE=20 DESIGN OF CAR POWER AMPLIFIER

There are many designs of good amplifier published, =20 solid state (SS) or tube designs. But few have written the design = of car=20 power amplifier

Actually the difficulty of designing the car power amplifier does not lies with = the audio power amplifier, but it is more to providing the switching power = supply.=20

As we knows, the output power of any audio power amplifier is approached = by formula :

P=20 =3D Vpp2/(8*Rl)

where Vpp=3D peak = to peak supply voltage, Rl is the speaker impedance = load. For car voltage of 12Vdc, if we connect it to 4 Ohm speakers we will only have = power of 144/32 =3D 4,5 Watt. Bridging the = amplifier will=20 double the power, but will never be more than 40 W. =

=20

If we want to make more powerful amplifier, lets say=20 170 watt at 4 ohm speaker load, we will need supply voltage of 74Vpp, or = +/- 37=20 Vdc. The way to have this voltage from car = supply of=20 12VDC is to make DC-DC = converter.

=20

In this article, I will discussed the car power amplifier in 3 steps :

=20

1.      The design of audio power amplifier =

=20

2.      The design of DC-DC converter

3.     Miscellenous  = tips for=20 making car power amplifier.

 

1. THE DESIGN OF AUDIO POWER AMPLIFIER =

In = fig1= =20 we can see that audio power amplifier can be splitted into 3 main functions, that=20 is:

-         First stage / input stage

-         Second stage / voltage amplifier = stage

-         Third stage / output stage

 

First stage is the stage that receives the input audio signal and =20 Negative Feedback  (NFB) signal from the output of the amp. = Feedback=20 is the back signal used to stabilized the = audio=20 amplifier, like the gain factor. For first stage built by discrete = transistors,=20 both signals is fed to basis of the = transistor, like=20 in fig1= .=20 Both basis of the transistors is the Non- = Inverting=20 input and Inverting Input, like those in the = op-amp.

Second stage is the stage that responsibles = for the Voltage Gain in the power amplifier.

Third=20 stage is the = Current=20 Gain.

We = can explain=20 those stages in a simple way like this : Input signal, like from car radio or CD player have low = voltage, about 1Vpp with few milliampere current. To = produce power of 170 Watt at 4 ohm speaker load, than the signal has to have maginitude=20 of 28Vpp and current of 6.5A (from the equation of P=3DI2*R = =3D=20 V2/R)

 The=20 first stage receives this signal in the non-inverting input and the = inverting=20 input receives NFB signal to make sure the voltage gain that the = amplifier=20 produces has a constant number, lets say 28 = x. The=20 output signal from the first stage has not reach 28Vpp, it tends to have the magnitude similiar to the input voltage. Second stage = amplifies the=20 voltage that the first stage generates. Second stage will amplifies the = voltage=20 to produce a signal that is enlarge 28x  for the amplifier to have = a 28Vpp=20 signal from 1Vpp signal, but this 28Vpp signal still have small current = , only a=20 few mA and cannot drive the speaker load. The third stage amplifies the = current=20 from few mA to 6.5 A.

Offcourse the explenation for three stages above is not that = simple in=20 the real amplifier. We should take the nature's law for a transistor = gain, that=20 is G=3DRC/RE. This principles must be = applied in each=20 transistor in those 3 amplifier stages.

FIRST=20 STAGE

First stage designs have main component, that is Constant = Current=20 Source (CCS) which can be seen in fig2=

. One of the basic of electronic law that works on every circuit is that = the voltage drop of Basis and Emitor (Vbe) equals the drop voltage of one dioda =3D = 0.67V. It=20 can be seen in  fig2= =20 that the voltage drop of 2 dioda IN4148 = =3D 2 x 0.67V=20 =3D 1,34V. We can see in RE and Q1, then V=3D0,67 is=20 substracted by  Vbe=20 of Q1 and the other 0,67V  will be the drop of RE. So we will have = a=20 Constant Current Source of 0,67/RE. In fig2= =20 the Ic is =3D = 4,4mA. CCS=20 first stage varies between 1-4mA.=20

In = fig1= =20 first stage, each component will be explained like = this:

-         R1 is the = impedance of the audio amplifier, the range is 10 Kohm=20 =96 47Kohm

-         C1 is the = highpass=20 filter from the equation : Fhp =3D 1/(2 x pi x R1 x = C1)

-         RED1 and RED2 = is=20 between 50-150 ohm

-         RM1 and RM2 = is picked=20 up so the voltage drop will be  50mV = =96=20 150mV

-         Q3 and Q4 is = the=20 Current Mirror that ensures the current in RM1 and RM2 will have the = same=20 magnitude.

-         RF and CF = will be=20 discussed later.

Before we discuss Second Stage and Third stage, first we will discuss the = amplifying effect of a transistor. In fig3= a=20 we will see a circuit of Common Emitor = Mode=20 (CEM). This circuit will amplifies the = voltage. In fig3= b we see a Common Colector Mode (CCM). This = circuit is=20 the current amplifier without voltage amplifier. So if we want to amplifies=20 voltage we use CEM circuit and to amplifies current we use CCM circuit.=20

SECOND=20 STAGE

The Second=20 stage responsibles for all voltage gain = (Maximum=20 Voltage Swing) in an audio power amplifier. This is why the Second stage = is=20 generally known as VAS or  Voltage = Amplifier=20 Stage. This stage consist of a voltage amplifier/CEM transistor(Q5 in fig1= )=20 in the bottom, Constant Current Source in the top, and a bias control = circuit in=20 the middle. Second stage CCS has current magnitude between=20 4-8mA

In = the second stage there is an important capacitor for an audio power amplifier , that is  Miller Capacitor (CC in = fig1= ).=20 CC defines the pole of the frequency response for an audio amplifier and = the=20 magnitude usually in small order (severalpF).

Bias control circuit consist of a transistor, resistor and a VR like in fig5= . This circuit uses a transistor that is placed in the heatsink, because = the transistor have good heat compensation factor (for bipolar = transistors).  For the amplifier that uses mosfet = transistor for=20 the final device, the bias circuit only needs potentio or dioda = only because=20 mosfets have different heat characteristic = than=20 bipolar transistors. The bias voltage magnitude depends on the type of = the third=20 stage used, which will be discussed later.

THIRD=20 STAGE

Third stage / Output Stage is the current amplifier. = Third stage=20 and the bias circuit will defines whether = an=20 amplifier works in class A, class AB or class B.

It = can be said that almost 90 % of car audio power amplifier works in class B. = Operation in class B does not mean that the sound produced is not good or corrupted. = With good design, we will have good audio results, both from class A or = class B. The choice of class B in car audio power amplifier is =20 conected to efficiency and the heat = generated. Heat generated is a very important factor, because if not = considered=20 carefully, it will lead to amplifier breakdown.

Many configurations of the output stage can be seen in fig4= .=20 Each configuration has different optimum bias voltage. It depends on how = many=20 Vbe's that = have to be passed.  Example : In fig4(a)&= nbsp; the signal has to pass 4 Vbe's, which is = Vbe Q1, Q3, Q4 and Q2. So the optimum bias =3D 4 = x 0.67V =3D 2.8V.

Both 3 stages=20 that we have discussed above, if we connect the together will be a = circuit that=20 can be seen in  fig5= .=20 Parts of this circuit can be explained like this:

-         The value of = Negative Feedback (NFB) resistor is determined by determining the gain factor = with the=20 equation :  Gain =3D 1+(R10/R8) =3D = 1+10k/500 =3D 21=20 x. The value of R10 =3D value of R1 to balance input. R20 and C7 are the pole and slope compensator.

-         C2 limits the = DC gain factor, value ranging from 47-220 uF, = usually using=20 a nonpolar = capacitor.

-         R21, R22 and = C11 will stabilize CCS. Here we use CCS with 2 transistor system,but the = equation used=20 still the same, that is  Ic =3D = 0,67/RE=20 .

-         The output of differential pair tapped from collector of T10 and send to VAS which is = built by T12 and T4. This configuration is called Darlington VAS and the = value of R8 is standard.

-         C3 is the = Miller capacitor with value of 100pF.

-         C5 is called = Speed=20 Up Capacitor. Several designs do not use = this=20 capacitor

-         R18, C6,L1=20 and R19 are output power stabilisator. If = there is=20 any oscilation occur in the audio power = amplifier,=20 the first tobe effected is R18 besides the final transistors.

Car Power amplifier usually loaded by low impedance speakers, usually 4 ohms and = can reach  =BD ohm on bridge mode. Here we know the term =93High = Current Amplifier=94. The difference is the number of final transistors, or in = fig5= =20 it is the number of pairs of T7 and T8. As a rule of thumb, the number = of=20 transistor needed first has tobe = calculated by=20 equations above, and then we determine the number of final transistor = needed=20 with assumption that 1 transistor can handle 50 Watt output. A pair of = bipolar=20 transistor can handle 100 Watt. The power is raised by parrarelling several output transistors, so the = currrent flowing will be larger. For large = number of final=20 transistors, we change the predriver stage = with=20 darlington = configuration.=20

Several=20 designs uses symetrical design, like those = used=20 in  AXL and Crescendo schematic. this design is developed from the basic principal above, but the signal = handling for + and - part is handled by complementary circuits.  =

I = have an=20 example about another kind of power amplifier, = that=20 is a non-feedback amplifier. You can view the principles of the "millenium=20 power amplifier" in the http://www.lcaudio.com/ . This = amplifier has=20 a certain gain factor in first and second stage, while the third stage = is only current amplifier.

2.THE DESIGN OF DC-DC=20 CONVERTER

For building=20 car power amplifier, we need symmetrical power supply (+, 0, -) by = building  DC-DC converter. The converter system = discussed=20 below will be the SMPS(Switch Mode Power = Supply) type=20 PWM (Pulse Width Modulation). This system will deliver stable output = voltage, regardless of the input voltage (usually the car electrical system will = range=20 in 9-15Vdc).

To = explain the  SMPS type PWM, it can be analogued by the next example. Look at  fig6= . There is a voltage pulse V1 on-off with 50% wide. These pulses if = passed  through suitable  L and C filter will = be transformated into straight voltage of V2 which = is V2 =3D =BD V1. (noticed the marked area below pulsed = V1 is the same total  area of the marked straight V2 ). With the same logic, = if the pulse width of V1 is narrowed, we will have a lower V2 and if we = enlarge the width of V1 pulse, we will have higher V2. Some may ask, how can we get 30VDC from the car's 12VDC? The = answer is=20 simple. If we get the V1 voltage to 60VDC, then in the 50% duty cycle, = we will=20 get 30VDC straight. This is the part where the power switching = transformer takes=20 control, to make the 60VDC from 12VDC, and then chopped by the = PWM.  This=20 is the princip of PWM. (Like the=20 principal of class D digital power amplifier). In this design, we = use=20 regulating PWM IC's, like TL494, TL594, SG3524, SG3525. These IC's will = compare=20 the output of DC-DC converter with a reference voltage. If the output of = DC-DC=20 converter is smaller than reference voltage, then the IC will enlarge = the pulse=20 width so the voltage will raise equally to = to reach determined voltage. So as if the output = of DC-DC=20 converter is higher than the reference voltage, the IC will narrow the = pulse=20 width so the output voltage will be lowered to the determined voltage.=20

 Generally SMPS used in car = audio=20 amplifier is the push-pull system with switching frequency between 20-70Khz.=20 In push pull sytem like in fig7= ,=20 Q1 and Q2 gives alternating switched current pulses so the transformator will be objected to maximum flux = swing=20 change without saturating the core.

In = this design=20 we will use PWM IC with SG3524 from SGS Thompson. Specifications can be = seen=20 in  SGS Thompson's website. Fig8= =20 shows the configuration of 16 pins on this IC. To make is simpler, lets design a SMPS by explaining the function of each pin. =

For the stereo power amplifier in  fig5= ,=20 we will need a  SMPS 12Vdc input and summetrical output of  +/- 37Vdc with 8A=20 rating.

1.  =20 First we make the Remote Turn On circuit , = which is=20 connected from the car radio / CD player. The circuit can be seen in fig9= a. This circuit will turn on the SMPS by giving 12Vdc to pin 12, pin 13 = and pin 15.

2.     The=20 SMPS switching frequency is determined 50Khz. For=20 this, the clock inside IC SG3524 is adjusted  = 2=20 x 50 Khz =3D 100Khz. This clock is built = up by pin=20 7(Ct) and pin 6(Rt). The=20 approach can be done with  equation = Fclk=20 =3D 1 /(Rt x Ct). Here we use Ct =3D 1nF = and Rt =3D 10Kohm like = in fi= g9b

3.     Pin=20 2(Non Inv In). In pin 2 we put stable reverence output for the SMPS. = Here we use=20 reference voltage of =BD from reference pin 16.

4.     Pin=20 1(Inv In) is the output voltage detector . = Pin 1 is=20 connected to the optoisolator type 4N35 = like in  fi= g9b.=20 Optoisolator is an important component in = making=20 this SMPS so we can have  Floating = Secondary=20 Ground which will prevent noises (especially whine/storing) if the power = amplifier is placed in car. The value of  = zener=20 diode is 2 x 37V =3D 74V. If it is difficult to have zener voltage of 74 = V, then=20 we can series several zener values until we have total of 74=20 V.

5.     Pin (4) and  pin(5) are not used and = connected to=20 ground, pin(8) and pin(10) connected directly with = ground.

6.      Pin=20 no 9(Comp) determines slope and pole of feedback from the whole SMPS = system. In=20 this design we use only 1 capacitor of 100nF.

7.     Pin=20 no 16(Vref) gives reverence voltage of = 5,1=20 Vdc . This pin is placed with 10nF as a = voltage=20 stabilisator.

8.     The=20 output ripple (Vr) of the SMPS is = determined by=20 equation :

      Vr =3D 8 x 10-6 x I / Co. With I =3D 8A and Vr =3D=20 0,029V we will have Co of 2.200uF    in +37Vdc = ->-37Vdc=20 rail or 4400uF each in +37Vdc_0  = and=20 4.400uF in 0_-37Vdc.

9.     For=20 output filter capacitor of 2.200uF, we will need approximately =20 4x 2.200uF or 8.800uF in the SMPS's = input=20 12Vdc . The larger the value of this capacitor, more energy stored for = the=20 SMPS.

10. Output=20 filter inductor Lo is determine by : Lo =3D = 0,5 x Vout/ (I x F). With Vout =3D 2 x=20 37V =3D 74V, I =3D 8A dan F =3D 50Khz, we will have Lo =3D 0,092mH or Lo =3D = 0,046mH on each=20 supply rail + and =96 37Vdc.

11. Pin=20 11 and pin 14 are output pins that will drive the primary winding = switching=20 mosfets. Inside IC SG3524 both pins have = already=20 opereated in mode push-pull. The circuit = for driving=20 power mosfets can be seen in  fi= g9b. The number of power mosfet used is 3 in = each transformator primary. So total there is 6 power = mosfets type BUZ11.

12. Transformator(trafo)=20 for SMPS is selfwould from ferrite toroidal=20 core (like donuts) like in fi= g10. It is very important that for SMPS frequency above 20Khz, we cannot use iron core transformator like we use in homes. The ferite=20 core transformator will have black color = like in the=20 speaker magnets, but do not have magnetizing force. The basic of = equation for=20 switching power supply with 12Vdc = input=20 is:

  (1)  Np =3D 1,37 x 105 / (F x Ae), where Np=3D primary=20 number of turns, F =3D  switching frequency, Ae =3D=20 X x Y =3D window area of ferrite in = cm2.=20 Look at fi= g10. To make it easy to wound the transformator, we will have to choose the toroid core with minimal diameter of 2,5 cm and window area minimal of = 0.75cm2.This is=20 necessary for the easyness of self handwound. Remember that in push-pull system there is 2 primary=20 windings.

(2) Ns/Np =3D Vo/8,8,=20 where Ns =3D secondary number of turns, Vo =3D secondary output=20 voltage

(3)=20 Ap =3D 0,004 x Vo x Io, where=20 Ap =3D window area of primary wire in =20 mm2, Vo =3D output voltage, Io =3D output=20 current.

(4) As =3D 0,13 x Io, where=20 As =3D window area of secondary wire in = mm2.

Example : =20 If we use toroidal ferrite core with = window area=20 of  Ae =3D 1 cm2. then from equation no. 1 we will have number of = primary=20 turn Np =3D 1,37 x 105 / (50Khz = x 1 cm2) =3D 2,74 turns. In practice, number of minimal primary = turns is 4 so the primary will cover the whole toroidal core.=20 So we use 4 turns for Q1 and 4 turns for Q2.

From equation (2) we have that Ns/Np =3D = 37/8.8 =3D 4,2. From here we can calculate that the number of = secondary windings is =3D Np x Np/Ns =3D 4 x 4,2 = =3D 16,8 or 17=20 windings. Like the primary, in secondary we use 2 x 17 turns, that is 17 = turns=20 for  +37V =96> 0 and 17 turns for 0-> = -37V

Equation (3) is used tp determine the number of = primary winding wires. We have  Ap =3D 0,004 x 74 x 8 =3D = 2,36mm2. If we use=20 a 1mm diameter magnet wire, we will have window area of = 0,785mm2 so=20 we will need 3 wire magnets for each = primary=20 windings

Equation (4) is used to determine the number of wire needed for secondary = windings. We have As =3D 0,13 x 8 =3D 1mm2 = So if we use=20 wire magnet with diameter of 0,8mm(window area =3D 0, 5mm2), = then we=20 will need 2 wires with diameter 0,8mm for each secondary=20 windings. 

13. The=20 secondary output voltage is rectified by full bridge configuration like = in fi= g11. Bridging diode must be the type of fast rectifier, usually looks like transistor TO220 with plate heatsink. For SMPS we cannot use ordinary = 50/60Hz rectifier diode. For this design we use diode type  BYW29-150, which have rating  of 8A, 150V. We can also use = other diodes like with prefixes FE=85,MUR..., as long as it is a fast rectifier diode = with=20 minimal specification like above.

3. MISCELLENEUS TIPS FOR MAKING CAR POWER AMPLIFIER=20  

Car power amplifier has specific accesories like = preamp gain circuit, an inverting channel so that the power is bridgeable. These=20 functions usually done with opamps. The circuit can be seen in fig12a= and the supply circuit can be seen in fi= g12b. The circuit is placed before the audio amplifier circuit.=20

The transformator is handwound on=20 toroidal ferrite core. The output filter = inductor=20 can be made with ferrite core material or MPP core material. It can be = made with=20 1.2mm wire magnet, handwound and measured = until we=20 have 0,046mH

Handwound the transformator core can be done as follow (fi= g13b):

-         First we = wound the secondary winding of 4 wires of 0.8mm magnet wires at once with 17 = numbers of=20 turn. The turn can be made in any direction as long as we consistent = with the direction of the wound. If we have finished wounding it, the toroidal=20 core will look like fi= g13a. We named the wires with wireA,B,C, and D.  If we start the wound = on top of=20 the core, the end will be at the bottom of the core. Make sure each wire = edges=20 with AVOmeter. Connect start edge of wire = A and B to=20 point S1 and the end edge of wire A and B to point G.  The start = edge of=20 wire C and D is connected to point G and the end edge of wire C and D is = connected to point S2.  Point G will be the secondary ground of the = power=20 amplifier and point S1 and S2 will be connected to bridging diode = of =20 BYW29.

-         After we = finished with secondary winding, we start to wound primary winding. Edges of primary wires is placed diagonally to the edges of the = secondary wires like in fi= g13c. Like winding the secondary wires, we wound 6 wires of 1mm diameter at = once. Name them wire A,B,C,D,E,and F.  Connect the start = edge of wire=20 A,B,C to point P1 and the end edge of wire = A,B,C to=20 point P+. Connect the start point of wire D,E,F to point P+ and the end = edge of=20 wire D,E,F to point P2 (fi= g13d) 

       If you have finished winding the = primary=20 and the secondary, the whole transformator = will have=20 the same wire directions like in fig12e= . Connect point P+ to the +12VDC of the car battery, point P1 to the = drain of power mosfets Q1 and point P2 to the = drain of the power mosfets Q2.

It = is=20 important to remember that all tracks in PCB layer that is connected to = the=20 power transformer has to have sufficient width due to large current will = be=20 involved. Also it is better if we soldered those tracks to have more = current=20 transfer.

After=20 finishing winding the transformator, place = all the=20 rest of the component and finish assembly of the SMPS. You can test it = by=20 connect it with 12VDC input from the battery. Don't forget to connect = the remote=20 turn on with 12VDC. There should be output voltage of =20 +37V, 0 and =9637V without any large current draw in the 12VDC = line. Check=20 for any mistakes, if the output voltage do = not=20 present or if the SMPS draws large current from 12VDC input.=20

In = the=20 assembly process of car audio power amplifier, we have to pay attention = in=20 mounting all transistors to the heatsink. We must use sufficient = heatsink=20 surface so the heat won't damage the amplifier. Use mica isolator and = white=20 silicon pasta to make sure the heat transfer. Firmly tighten all the = bolts to=20 press all the transistors. Car amplifier works in vigorous environment = like in=20 the trunk of a car. Placing an extra fan always a = good idea=20 in making car power amplifier.

After we=20 connect the SMPS to the audio amplifier, we are ready to test the car = power=20 amplifier. First trim the bias potentiometer fully left side to have = minimum=20 bias. Turn on the SMPS and look for the current draw in 12VDC line with = ampmeter. The ampmeter=20 indicator will raise for a moment to fill = all the=20 capacitors. After a few moment, the ampmeter=20 indicator must turn back to minimum indication of ampere. If not, there = is some=20 problem. Then we trim the bias to optimal point. Usually for car stereo = power=20 amplifier total quiscent ampere will not = exceed 2A=20 of 12VDC line. 

=20 =20 =

=20

------=_NextPart_001_0009_01CF1847.2DB169A0 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Location: res://ieframe.dll/dnserrordiagoff.htm =EF=BB=BF =20 =20 This page can=E2=80=99t be displayed =20 =20 =20 =
This page can=E2=80=99t be = displayed
  • Make sure the web address is=20 correct.
  • Look for the page with your search engine.
  • Refresh the page in a few minutes.
  • Check that all network cables are plugged in.
  • Verify that airplane mode is turned off.
  • Make sure your wireless switch is turned on.
  • See if you can connect to mobile broadband.
  • Restart your = router.
------=_NextPart_001_0009_01CF1847.2DB169A0-- ------=_NextPart_000_0000_01CF1847.2DB169A0--