Customization: software and hardware modifications

AN2446

10/13

The constant to be modified is named Dead_Time_Period, defined in the main() routine,

where the defines are declared. The value is expressed in tens of milliseconds.

A value of 10000 means 100000 milliseconds, or 100 seconds, or 1 minute and 40 seconds.

Default value: 12000 (possible range: 0 to 65535).

5.5

Gate pulse duration

The gate pulses are applied to the AC switches, which in turn drive the RUN winding and the

START winding of the compressor. The gate pulse applied to the RUN winding has the

same duration of the one applied to the START winding.

The gate pulses are applied when the mains voltage crosses the zero. Therefore, twice per

period.

The constant to be modified is named DURATION, defined in the ports() routine, where

the defines are declared. One point is equal to 400 µs.

A value of 10 means 4000 µs, or 4 ms, or an angle of 72°. Since half of a period is 10 ms

(mains frequency 50 Hz), care has to be taken while changing this constant.

Default value: 17 (possible range: 0 to 255, in any case do not exceed 25).

5.6

Disabling the stall rotor detection

Basically, the stall rotor detection reduces the power consumption when attempting to turn

on a stalled compressor, also keeping the AC switch from getting damaged.

In any case, when testing a small compressor (meaning 1 A nominal current and 5A when in

stall condition), the stall rotor detection can be disabled without damaging the AC switch.

No software modification is required. Simply unsolder the R13 temperature sensor and

replace it with a 100 K

Ω 5% ¼ W resistor.

5.7

Different START winding management

The evaluation board drives directly the START winding avoiding the use of the PTC.

If the PTC cannot be removed from the original circuitry, the AC switch will simply switch the

PTC off after the compressor is spinning.

The PTC can drive the START winding without using the AC switch too. In this case, the

evaluation board will drive the RUN winding only. No hardware or software modifications are

required.