ST52T301 datasheet(48/100 Pages) STMICROELECTRONICS

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10.2 BURST MODE

When REG_CONF10 (3:2) bits, MODE, are ”10”

the peripheral is programmed to work in BURST

MODE.

Notice that when you are working in Burst mode

CKSL must be set to ”1x”. (see Table 10.4)

A square wave, Tb, is generated with a duty cycle

proportional to the power the user intends to

transfer on the load. A pulse is generated for each

zero crossing of the main voltage included in the

Ton of the fixed period. Figure 10.4 shows the

typical Burst Control working mode.The period T of

the signal Tb (see Figure 10.4) is equal to 256*Tck.

The signal Tck is generatedprogrammingthe 16-bit

Prescaler, by REG_CONF8 and REG_CONF9

(see Figure 10.2). Tck is equal to the main voltage

frequency (50 or 60 Hz) divided by N+1, where N

value is from 0 to 216-1.

The value Ton is prop or tional to a value,

INIT_VALUE, that can be a fuzzy output or a value

coming from Register File, according with the

I N PS L and F Z S L c onf ig ur at ion bit s of

REG_CONF12 (see Table 10.6 and Figure 10.12).

On TRIACOUT pin is generated a sequence of

pulses, programmed, by using REG_CONF11(0)

bit, POL (see Table 10.5), in order to be positive or

negative, to drive the Triac in different quadrants.

The number of generated pulses, N_PULSES, is:

N_PULSES = 2 [(N+1)*INIT_VALUE - N]

where N is the value stored in the 16-bit pescaler.

Then Ton = (N_PULSES / 2)* TPOWER LINE

The first pulse is obtained during the first zero

crossing of the main voltage and the last one is

genera ted after INIT_VALUE*Tck clock pulses,

where Tck is the Prescaler output, generated by

using the main voltage frequencyapplied to MAIN1

and MAIN2 pins.

The peripheral can be programmed in order to work

with 50 or 60 Hz main voltage frequency, by setting

the REG_CONF10(6) bit, PSF (see Table 10.4).

Ranges of the Tb signal period depend on the

power line frequency (see Table 10.3).

In order to drive a Triac in Burst Mode it is required

to generate a sequence of pulse, that must be

centred on the zero crossing of the power line as

shown in the Figure 10.7. For this reason, the pre

zero crossing and the post zero crossing of the

power line must be detected.

To detect the zero-crossing and get also the main

voltage frequency, the user must generate MAIN1

and MAIN2 signals, by using the circuit shown in

Figure 10.6.

MAIN1 and MAIN2 signals are used in the block

called PULSE GENERATOR of the peripheral (see

Figure 10.1).

In particular the pulses are generated by using the

rise edge of the signal MAIN1 and the falling edge

of the signal MAIN2.

Figure 10.5 shows the generation of the Triac

pulses Tp .

The first firing pulse for the Triac is generated on

the zero crossing of the power line, while the next

pulses are centred on the zero crossing.

Power Line

Frequency

min

max

50 Hz

5.12 s

335544 s

60 Hz

4.26 s

279620 s

Table 10.3. TRIACOUT Signal Period

-1.5

-1

-0.5

0.5

1.5

Ton

Power

Line

TRIACOUT

T = 256 * Tck

Figure 10.4. Burst Working Mode

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ST52T301/E301

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