IXDN0036 datasheet(16/41 Pages) IXYS

16 / 41 page

Device Design & Application

5-16

ATAVRFBKIT / EVLD001 User Guide

7597A–AVR–02/06

FETs due to current shoot through, is prevented via the input drive signals through the

microcontroller.

Other features of the IXD611 driver include:

• Wide supply voltage operation 10-35V

• Matched propagation delay for both drivers

• Undervoltage lockout protection

• Latch up protected over entire operating range

• +/- 50V/ns dV/dt immunity

5.4

IXYS IXI859

Charge Pump

Regulator

The IXI859 charge pump regulator integrates three primary functions central to the PFC

stage of the ballast demonstrator. First it includes a linear regulated supply voltage out-

put, and in this application the linear regulator provides 3.3V to run the microcontroller.

The second function is a gate drive buffer that switches an external power MOSFET

used to boost the PFC voltage to 380V. Once the microcontroller is booted up and run-

ning, it generates the input signal to drive the PFC MOSFET through the IXI859 gate

drive buffer. Finally, the third function provides two point regulated supply voltage for

operating external devices. As a safety feature, the IXI859 includes an internal Vcc

clamp to prevent damage to itself due to over-voltage conditions.

In general applications at start-up, an R-C combination is employed at the Vcc supply

pin that ramps up a trickle voltage to the Vcc pin from a high voltage offline source. The

value of R is large to protect the internal zener diode clamp and as a result, cannot sup-

ply enough current to power the microcontroller on it’s own. C provides energy to boot

the microcontroller. At a certain voltage level during the ramp up, the Under Voltage

Lock Out point is reached and the IXI859 enables itself. The internal voltage regulator

that supplies the microcontroller is also activated during this time. However, given the

trickle charge nature of the Vcc input voltage, the microcontroller must boot itself up and

enable PFC operation to provide charge pump power to itself. This means that the R-C

combination must be sized carefully so that the voltage present at the Vcc pin does not

collapse too quickly under load and causes the UVLO circuitry to disable device opera-

tion before the microcontroller can take over the charge pump operation. Also note that

there is an internal comparator that only releases charge pump operation when the Vcc

voltage drop below 12.85V. The charge pump is released and Vcc voltage is pumped up

to 13.15V at which time the internal comparator disables the charge pump. This results

in a tightly regulated charge pump voltage.

One problem with the R-C combination described above is that when a universal range

is used at the Vcc pin, 90-265VAC, R must dissipate nine times the power, current

squared function for power in R, over a three-fold increase of voltage from 90V at the

low end to 265V on the high end. As an alternative and as used in the ballast demon-

strator, the Vcc pin is fed voltage by way of a constant current source as previously

described in section 6.2. This circuit brings several advantages over the regular R-C

usage. First we can reduce power consumed previously by R and replace it with a circuit

that can provide power at startup. It can also provide sufficient power to run the micro-

controller unlike the R-C combination. This would be an advantage in the case that a

IXDN0036 датащи(PDF) 16 Page - IXYS Corporation

IXDN0036 датащи(HTML) 16 Page - IXYS Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

датащи скачать

ссылки URL