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tecnologycontorol

200W Interleaved Forward Converter Design Review

جمعه 89 اردیبهشت 17 , ساعت 12:18 صبح

Application Report

SLUA312 ? May 2004

200-W Interleaved
Forward Converter Design Review

Using TI’s UCC28221
PWM Controller

Michael O’Loughlin
System Power

ABSTRACT

Interleaved buck converters are widely
used in the personal computer industry in voltage

regulation module (VRM) applications to
power central processing units, CPUs, like the

Pentium 4? and Athlon?. This topology is widely used due to the reduced input and
output

capacitor ripple current that is gained
by interleaving the converters as compared to a single

buck power stage. The reduction in
input and output capacitor RMS currents allows the

designer to reduce the input and output
capacitor banks that are required for the design. The

same benefits that are gained from
interleaving buck converters can be gained from

interleaving forward converters. In
high current applications such as telecom dc-to-dc

converters reducing the input and
output capacitor banks can reduce the size and cost of the

design. This application note reviews
the design of a telecom converter that converts a

telecom input range of 36 V to 75 V dc
down to a regulated 12-V, 200-W dc output. The design

information in this application note is
used in the design of the UCC28221 Evaluation Module

(EVM) HPA035 [5].

Table 1. Applicable
Devices

MIN TYP MAX UNITS

Input voltage (VIN) 36 75 V

Output voltage (VOUT) 11.4 12 12.6 V

Output power (POUT) 50 200 W

Switching frequency (fS) 500 kHz

Efficiency at maximum output power (ç) 85%

Maximum duty cycle (DMAX) 50%

Input voltage ripple (VIN(ripple)) 1 V

Output voltage ripple (VOUT(ripple)) 200
mV

NOTES:This design was based on typical
design values.

SLUA312 ? May 2004

2 200-W Interleaved Forward Converter
Design Review Using TI’s UCC28221 PWM Controller

1 Schematic

1 N/C

INA

3 GND

INB

5 OUTB

6 VDD

7 OUTA

8 N/C

UCC27324D

+ +

Figure 1. Typical
Application Diagram

SLUA312 ? May 2004

200-W Interleaved
Forward Converter Design Review Using TI’s UCC28221 PWM Controller 3

2 Power Stage Design

2.1 Transformer Turns Ratio (T3 and T4)

The first step is to calculate the
required transformer turns ratio required for the design. The

following equations are used to
calculate the approximate transformer turns ratio. With a

maximum duty cycle of 0.5 at minimum
input voltage (VIN(min)) the calculated turns ratio for the

design is roughly 1.4.

a _

a _ DMAX

VIN(min)_1 V

VOUT_1 V _ 1.4

2.2 Output Inductor Selection (L2 and
L3)

The output inductor was sized based on
the worst case ripple current that occurs at minimum

duty cycle, DMIN, and a maximum output
power, POUT(max), of 200 W. The output
capacitor ripple

current cancellation of interleaving
two forward converters allowed the output inductors LOUT to

be designed for a ripple current that
was roughly 60% of the maximum load current. For this

design we used 3.2-?H low profile inductors from Vishay, part number

IHLP?5050FD?RZ?3R3?M?01.

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Sziklai Output

چهارشنبه 89 فروردین 25 , ساعت 10:40 صبح

The Complementary Sziklai Output

Named after a prolific inventor by the name of George C. Sziklai, this version sports a Sziklai output section, or what is sometimes called the "Complementary Feedback Pair".

What is a Sziklai?
In essence, a high gain super transistor, somewhat similar to a Darlington. But there are major differences. Unlike Darlingtons, there is some voltage gain with Sziklais. Another unique feature is local feedback.

Why is it not as popular as EF?
Basically, more difficult to design then EF. When local feedback is nested in a global feedback, an amplifier is more prone to instability. In other words, it is easier to break out into high frequency oscillations. But a well designed Sziklai Output can often be outstanding.

Performance Factor
This is where it probably makes a real difference. With listening tests, the Sziklai Outputs are the most enjoyable of the three designs. It sounds faster and the highs are smoother. This is probably due to a wider bandwidth and faster rise time. All these are achieved without compromising bass slam and definition. Clip characteristics are similar to c200 (EF version), with no signs of distortion and instability when driving 8 and 4 ohms test loads up to rated power.

Mr George Clifford Sziklai is credited for inventing the full complementary symmetrical output that we take so much for granted today. More information on his illustrious career can be found at this Los Altos Town Crier article by writer Linda Taaffe.

THD of c200.2 complementary Sziklai output

Biasing of output transistors
All THD readings were done with outputs biased to 12mV across 0.22 ohms emitter resistor. This works out to approximately 55mA per output transistor in idling state

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Download

یکشنبه 89 فروردین 22 , ساعت 9:56 عصر

First, in order to enable the download menu commands, you must select the Block folder in the project"s station you wish to download.

There are three methods of downloading.

Partial download of selected blocks
Full download of all blocks and system data
Complete deletion of online PLC blocks and then downloading of all blocks and system data

Partial Download

Partial downloads are used in existing projects where only one or more blocks will be downloaded. To perform this type of download select the block(s) you wish to download and then select the PLC > Download menu item or the download button .

Holding down the Ctrl key or the Shift key allows more then one block to be selected at a time. Be careful though as the order of download will occur in the order that the blocks were selected. This may mean that an error will occur if a block is called before it is downloaded.

The CPU will need to be in Stop mode before downloading the System Data Block (SDB) as this is equivalent to a hardware configuration download. This is usually not necessary in a PLC that has all ready had its hardware configured. If you do download the system data, the following messages will prompt you through the transitions.

If the CPU is in Run mode then you will be prompted to Stop the CPU. The software will do the Run to Stop transition when you click OK.

After downloading the SDB you will be prompted to Run the CPU again.

Clicking Yes will automatically put the CPU back into run mode.

Full Download

To download all the blocks at once make sure you are in the Block folder and select the Edit > Select All menu item. Click on the Download icon . You will be prompted to overwrite any existing blocks and if you want to load the system data (see above).

Clearing the CPU Memory and then Downloading

The partial and full download methods above will overwrite existing blocks but will not any blocks from memory. In order to completely delete the existing program in the CPU and download a new project select the Blocks folder and then use the PLC > Download User Program to Memory Card menu item.

The following dialog box will pop up prompting you about the deletion of all the blocks and project data in the PLC. Click Yes to perform the operation.

After this, follow the normal download procedure.

‹ Connecting to the S7 PLC up Uploading ›

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plcUploading

شنبه 89 فروردین 21 , ساعت 2:10 عصر

Step 7 Connecting, Downloading and Uploading

These are general guidelines for connecting, downloading and uploading from an S7-300 or S7-400 PLC. The following procedures were created using Siemens SIMATIC STEP 7 version 5.4 software.

To start, open the SIMATIC Manager.

Now follow the links below.

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Pico Controllers I/O

جمعه 89 فروردین 20 , ساعت 2:3 عصر

<> if (eW3C==true) eClose("Programmable Automation Controllers (PAC)");
if (eW3C==true) eOpen("Programmable Logic Controllers (PLC)");
if (eW3C==true) eClose("Safety Programmable Controllers"); Pico Controllers I/O

Programmable Logic Controllers

Pico Controllers

I/O

You may have several different types of applications where the Pico controllers can be used. The Pico expansion I/O modules provide you with flexible choices that allow you to purchase the I/O count you need for a variety of applications. It is simple for you to expand the 18- and 20-point and GFX processors with any one of the Pico expansion I/O modules. Select between 2- or 6-point AC Relay outputs and the 8-point DC transistor outputs modules that you can use with AC or DC processors.

Pico GFX controllers are expandable up to 272 I/O points with the use of the current Pico expansion I/O modules and Pico-Link. Connect up to eight GFX controllers using the new GFX proprietary Pico-Link inter-connectivity network. It provides you more points of I/O and allows you to peer into the process.

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