Wednesday, September 06, 2017

Offline Isolated Flyback LED Controller - LT3799-1

This chip for LED driving has a power factor correction, the critical conduction mode keeps transformer small. A opto-coupler for feedback is avoided by an innovative primary shunt monitor.

Offline Isolated Flyback LED Controller - LT3799-1

The LT3799-1 uses a micropower hysteretic start-up to efficiently operate at offline input voltages, with a third winding to provide power to the part. An internal LDO provides a well regulated supply for the part’s internal circuitry and gate driver.

LED Controller - LT3799-1

20 Watt LED Driver using LT799-1

The FAULT pin provides notification of open and short LED conditions. The LT3799-1 offers improved line regulation over the LT3799, but is not designed for use with a TRIAC dimmer.

Features
  • Offline 4W to 100W+ LED Applications
  • High DC VIN LED Applications
  • Gate driver to drive an external high voltage MOSFET.
  • Typical power factors of 0.97.

Tuesday, September 05, 2017

LED Drive using TPS61042

This Chip from TI is simple to integrate into your designs and this solution is good for production of lighting gadgets, here a consistent quality and predictable performance is easily obtained.

TPS61042 30-V, 500-mA Switch Boost Converter  for White LED Applications
LED-driver application that drives four LEDs with 20 mA of forward current and operates from an input voltage range of 1.8 to 6.0 V.

The entire circuit consists of the control IC, two small ceramic caps, an inductor, a diode, and a current sense resistor. The primary power-supply functions and the secondary features such as load disconnect, overvoltage protection, and PWM dimming have been implemented with a control IC and five small surface-mount passive components.

LED Drive using TPS61042

LED-driver considerations - By Michael Day

Many of today’s portable electronics require backlight LED-driver solutions with the following features: direct control of current, high efficiency, PWM dimming, overvoltage protection, load disconnect, small size, and ease of use.

Monday, September 04, 2017

AD636 - True RMS to DC Converter

Working on low signals in the range of 0 mV to 200 mV rms, AD636 makes a precision AC to DC signal conditioner for Instrumentation. DMM, Data Loggers and Process Indicators can use this.

AD636 - True RMS to DC Converter

Using this chip you can make a True RMS Voltmeter for your Lab or Project.


The AD636 is easy to use. The device is factory-trimmed at the wafer level for input and output offset, positive and negative waveform symmetry (dc reversal error), and full-scale accuracy at 200 mV rms. Therefore, no external trims are required to achieve full-rated accuracy.

Some Features and Specs
  • Laser-trimmed to high accuracy
  • 0.5% maximum error (AD636K)
  • Computes rms of ac and dc signals
  • 1 MHz, −3 dB bandwidth: V rms > 100 mV
  • Signal crest factor of 6 for 0.5% error
  • Low power: 800 μA quiescent current

Friday, August 11, 2017

Zero-Crossing-Triac-Driver-Optocoupler-MOC3041

The MOC303XM and MOC304XM devices consist of a AlGaAs infrared emitting diode optically coupled to a monolithic silicon detector performing the function of a zero voltage crossing bilateral triac driver. MOC3041.

They are designed for use with a triac in the interface of logic systems to equipment powered from 115 VAC lines such as teletypewriters, CTRs, solid-state relays, industrial controls, printers, motors, solenoids and consumer appliances, etc

  • Simplifies logic control of 115 VAC power
  • Zero voltage crossing
  • dv/dt of 2000 V/µs typical, 1000 V/µs guaranteed
Motorola used to make these then it was Infineon Technologies now Isocom also makes it

MOC3041 Zero Crossing Triac Output, 6 Pin

See the original Motorola Application below.


MOC3041 Zero Crossing Triac Output, 6 Pin

These were used by me to make solid state relays. Look at the circuits here Power Electronics Circuits. The were used to control Heaters from DC control signal from a Proportional Temperature Controller. The Magnetic Contactors can be avoided for lower powers. At higher powers SCR banks become a bit expensive.

OC3041M: 6-Pin DIP 400V Zero Crossing Triac Driver Output Optocoupler

The SSR has no mechanical wear and tear but heat up at high currents. So if we overrate by 5 Times then it is an excellent solution for lower power controls upto 5 Kilo Watts. The cycle time of Contactors must be 20-60 Seconds to make it last long. In a SSR a one second cycle time is possible as 10-20mS is the switching speed due to zero crossing.

Thursday, August 10, 2017

Precision RMS Value of AC Waveform - LTC1968

"RMS to DC conversion is the truest way to measure the energy contained in an AC waveform."

Linear Technology - RMS-DC Conversion

The accurate measurement of AC for a wide variety of waveforms and noise is difficult. When we make solar systems and inverters, the AC outputs are seldom sinusoidal. The easy method is to use a Precision rectifier/filter, get the average voltage and a RMS calibration/scaling is done for sine is by tweaking a trimpot. This will not show the right values for other waveforms. The other way was, analog computing, with many opamps and a matched pair of transistors; like multipliers and log amps, very cumbersome for manufacturing and testing.

Precision RMS Value of AC Waveform - LTC1968

These single chip solutions like LTC1968 - Precision Wide Bandwidth, RMS-to-DC Converter make it easy to implement an AC Measurement in your embedded, PLC or PC based solution.

LTC1968 - Precision Wide Bandwidth, RMS-to-DC Converter

The LTC1968 is a true RMS-to-DC converter that uses an innovative delta-sigma computational technique. The benefits of the LTC1968 proprietary architecture, when compared to conventional log-antilog RMS-to-DC converters, are higher linearity and accuracy, bandwidth independent of amplitude and improved temperature behavior.

High Linearity: 0.02% Linearity Allows Simple System Calibration

Wide Input Bandwidth:
  • Bandwidth to 1% Additional Gain Error: 500kHz
  • Bandwidth to 0.1% Additional Gain Error: 150kHz
  • 3dB Bandwidth Independent of Input Voltage Amplitude

Friday, August 04, 2017

Texas Instruments - TI Semiconductors

Texas Instruments, better known in the electronics industry (and popularly) as TI, is an American company based in Dallas, Texas, USA, renowned for developing and commercializing semiconductor and computer technology.

Texas Instruments - TI Semiconductors

Chip IC Products include Solutions in Analog, DSP- Digital Signal Processing, Power Management, A/D Converter, Microcontroller based Systems, Mixed Signal Designs, Multiplexers and Thermal Management Solutions.

A Vintage Calculator from TI

Texas Instruments

Texas Instruments - wiki

TI produced the world's first commercial silicon transistor in 1950, and designed and manufactured the first transistor radio in 1954. Jack Kilby invented the integrated circuit in 1958 while working at TI's Central Research Labs.

TI also invented the hand-held calculator in 1967, and introduced the first single-chip microcontroller (MCU) in 1970, which combined all the elements of computing onto one piece of silicon.

Texas Instruments - TI Semiconductors

A Developer Evaluation Embedded System

Texas Instruments Embedded Portfolio Overview is made up of three sub-divisions: Wireless, Microcontrollers, and Processors

Embedded processors are the processing brains of electronics that gather inputs from analog chips and perform computational processing to operate a system.

Wednesday, July 05, 2017

MAX1910 White LED Charge Pumps - Maxim IC

Drives LEDs with a regulated output voltage or current (up to 120mA) from an unregulated input supply (2.7V to 5.3V). These are complete DC-DC converters requiring only four small ceramic capacitors and no inductors. 200mV Current-Sense Threshold Reduces Power Loss.

MAX1910 White LED Charge Pumps - Maxim IC

The MAX1910/MAX1912 are complete charge-pump boost converters requiring only four small ceramic capacitors. They employ a 750kHz fixed-frequency 50% duty-cycle clock.

MAX1910 White LED Charge Pumps - Maxim IC

Figure 4’s circuit improves LED current matching by raising the ballast resistance while maintaining a 200mV VSET. The increased ballast resistance tolerates wider LED mismatch, but reduces efficiency and raises the minimum input voltage required for regulation.

Yet another method of biasing LEDs is shown in Figure 5. In this case, the current through the complete parallel combination of LEDs is set by R5. R1–R4 are only used to compensate for LED variations. This method of biasing is useful for parallel LED arrays that do not allow connection to individual LEDs.