Linear Technology DC776 Manuel utilisateur

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

LTC3705 and LTC3706

DESCRIPTION

Demonstration circuit 776 is a 36V-72Vin, forward

converter featuring the LTC3705 and LTC3706. This

circuit was designed specifically to attain a high step-

down ratio power supply in one stage in order to ef-

ficiently power 1.5V loads from a typical telecom in-

put voltage range. Isolation voltage is 1500VDC.

This circuit features secondary-side control of the

supply without the need of an optocoupler, self-

starting architecture, input undervoltage lockout, and

output overvoltage protection.

Design files for this circuit board are available.

Call the LTC factory.

,LTC and LT are registered trademarks of Linear Technology Corporation.

Table 1.

Performance Summary (TA= 25°C)

PARAMETER CONDITION VALUE

Minimum Input Voltage 36V

Maximum Input Voltage 72V

Output Voltage V

OUT

= 36V to 72V, I

OUT

= 0A to 45A, 400LFM 1.5V ± 1%

Maximum Output Current 400LFM

200LFM

45A

40A

Typical Output Ripple V

OUT

= 48V, I

OUT

= 30A (20MHz BW) 30mV

P–P

Line ±0.01%

Output Regulation

Load ±0.18%

Dynamic Response

Peak Deviation

Load Step of 20A to 40A (1A/us min)

Settling Time (to within 15mV of set point)

65mV

50us

Nominal Switching Frequency 215kHz

Efficiency V

= 48V, I

OUT

= 45A, 400LFM 84.75% Typical

Logic Low Voltage-Off 1V MAX

On/Off Control

Logic High Voltage-On 2.5V MIN

Isolation Voltage Basic Insulation 1500VDC

OPERATING PRINCIPLES

The LTC3706 controller is used on the secondary and

the LTC3705 driver with self-starting capability is

used on the primary. When an input voltage is ap-

plied, the LTC3705 begins a controlled soft-start of

the output voltage. As this voltage begins to rise, the

LTC3706 secondary controller is quickly powered up

via T1, D3, and Q13. The LTC3706 then assumes

control of the output voltage by sending encoded

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

PWM gate pulses to the LTC3705 primary driver via

the small signal transformer, T3. The LTC3705 then

operates as a simple driver receiving both input sig-

nals and bias power through T3.

The transition from primary to secondary control oc-

curs seamlessly at a fraction of the output voltage.

From that point on, operation and design simplifies to

that of a simple buck converter. Secondary sensing

eliminates delays, tames large-signal overshoot and

reduces output capacitance. This, while utilizing off-

the-shelf magnetics and attaining high efficiency.

For large values of input inductance, a 100V, 47uF elec-

trolytic capacitor can be added across the input termi-

nals to damp the input filter and provide adequate stabil-

ity. See Linear Technology Application Note AN19 for a

discussion on input filter stability analysis. A recom-

mended part is the Sanyo 100MV39AX.

QUICK START PROCEDURE

Demonstration circuit 776 is easy to set up to evalu-

ate the performance of the LTC3705 and LTC3706.

Refer to Figure 1 for proper measurement equipment

setup and follow the procedure below:

NOTE:

When measuring the input or output voltage

ripple, care must be taken to avoid a long ground lead

on the oscilloscope probe. Measure the output (or

input) voltage ripple by touching the probe tip and

probe ground directly across the +Vout and –Vout (or

+Vin and –Vin) terminals. See Figure 2 for proper

scope probe technique.

Set an input power supply that is capable of 36V to

72V to a voltage of 36V. Then turn off the supply.

With power off, connect the supply to the input

terminals +Vin and –Vin.

Input voltages lower than 36V can keep the con-

verter from turning on due to the undervoltage

lockout feature of the LTC3705.

If efficiency measurements are desired, an am-

meter capable of measuring 3Adc can be put in

series with the input supply in order to measure

the DC776A’s input current.

A voltmeter with a capability of measuring at

least 72V can be placed across the input termi-

nals in order to get an accurate input voltage

measurement.

Turn on the power at the input.

NOTE:

Make sure that the input voltage never ex-

ceeds 72V.

Check for the proper output voltage of 1.5V ± 1%.

Turn off the power at the input.

Once the proper output voltages are established,

connect a variable load capable of sinking 50A at

1.5V to the output terminals +Vout and –Vout. Set

the current for 0A.

If efficiency measurements are desired, an am-

meter or a resistor shunt that is capable of han-

dling 50Adc can be put in series with the output

load in order to measure the DC776A’s output

current.

A voltmeter with a capability of measuring at

least 2V can be placed across the output termi-

nals in order to get an accurate output voltage

measurement.

Turn on the power at the input.

NOTE:

If there is no output, temporarily disconnect

the load to make sure that the load is not set too

high.

Once the proper output voltage is again estab-

lished, adjust the load within the operating range

and observe the output voltage regulation, ripple

voltage, efficiency and other desired parameters.

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

Figure 1.

Proper Measurement Equipment Setup

VIN

GND

Figure 2.

Measuring Input or Output Ripple

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

MEASURED DATA

Figures 3 through 13 are measured data for a typical DC776A.

5 10 15 20 25 30 35 40 45 50

Current (A)

Efficiency (%)

36VIN

48VIN

72VIN

Figure 3.

Efficiency (400LFM)

Figure 4.

Regulation (400LFM)

1.425

1.445

1.465

1.485

1.505

1.525

1.545

1.565

5 10 15 20 25 30 35 40 45 50

Current (A)

Regulation (V)

36VIN

48VIN

72VIN

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

Figure 5.

Output Voltage Ripple (72Vin and 50A)

Figure 6.

Load Transient Response (>1A/us)

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

Figure 7.

Temp Data (48Vin, 45A, 400LFM – front)

Figure 8.

Temp Data (48Vin, 45A, 400LFM – back)

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

Figure 9.

Temp Data (48Vin, 40A, 200LFM – front)

Figure 10.

Temp Data (48Vin, 40A, 200LFM – back)

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

Figure 11.

Turn-on Waveforms (72Vin and 50A)

Figure 12.

Turn-off Waveforms (72Vin and 50A)

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

Figure 13.

Control Loop Bode Plot (48Vin and 20A)

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 776

36V-72VIN, FORWARD CONVERTER

Table des matières

Autres manuels Linear Technology Carte mère

Linear Technology

Linear Technology 1635A Guide de l'administrateur

Linear Technology

Linear Technology DC861A-A Manuel utilisateur

Linear Technology

Linear Technology DC1496C Guide de configuration rapide

Linear Technology

Linear Technology LTC3880 Guide de configuration rapide

Linear Technology

Linear Technology DC1948A Guide de configuration rapide

Linear Technology

Linear Technology DC2397A Guide de configuration rapide

Linear Technology

Linear Technology DC1123 Manuel utilisateur

Linear Technology

Linear Technology DC1788B Guide de configuration rapide

Linear Technology

Linear Technology LTC5584 Manuel utilisateur

Linear Technology

Linear Technology DC1546A Guide de configuration rapide

Linear Technology

Linear Technology DC1338B Guide de configuration rapide

Linear Technology

Linear Technology DC2003A Guide de configuration rapide

Linear Technology

Linear Technology 2373A Guide de configuration rapide

Linear Technology

Linear Technology DC1216A-A Guide de configuration rapide

Linear Technology

Linear Technology Demo Circuit 1592A Manuel utilisateur

Linear Technology

Linear Technology DC1959B Guide de configuration rapide

Linear Technology

Linear Technology DC1884A Series Guide de configuration rapide

Linear Technology

Linear Technology DC1812A Guide de configuration rapide

Linear Technology

Linear Technology 1029 Manuel utilisateur

Linear Technology

Linear Technology DC2160A Guide de configuration rapide

Linear Technology

Linear Technology DC832 Manuel utilisateur

Linear Technology

Linear Technology Analog Devices DC2564A Guide de configuration rapide

Linear Technology

Linear Technology DC1636A Guide de configuration rapide

Linear Technology

Linear Technology DC1544 Manuel utilisateur

Manuels Carte mère populaires d'autres marques

DFI

DFI SD170 Manuel utilisateur

ASROCK

ASROCK ROMED8-2T Manuel utilisateur

Asus

Asus P2L97A Manuel utilisateur

Winmate

Winmate IC70 Manuel utilisateur

Asus

Asus MES-B Manuel utilisateur

Grantech

Grantech SYS8F377VGGA-3OMN Manuel utilisateur

Telit Wireless Solutions

Telit Wireless Solutions SL869-3DR Manuel utilisateur

Gigabyte

Gigabyte GA-9IVDT Manuel utilisateur

Texas Instruments

Texas Instruments ADS8372EVM Manuel utilisateur

Commell

Commell MS-C73 Manuel utilisateur

IBT Technologies

IBT Technologies MB860 Manuel utilisateur

Nvidia

Nvidia TEGRA DG-04927-001_V01 Manuel utilisateur

Biostar

Biostar M7VIT Bravo Instructions d'utilisation et d'installation

Intel

Intel D33217CK Manuel utilisateur

Asus

Asus F1A55-M LX PLUS R2.0 Manuel utilisateur

EPC

EPC EPC9147C Manuel utilisateur

Asus

Asus EX-B760M-V5 D4 Manuel utilisateur

EPOX

EPOX MU-8KHA0010 Manuel utilisateur