UM0277 datasheet(17/32 Pages) STMICROELECTRONICS

Part #	UM0277

Description	Getting started with the Cold Thermostat Kit based on AC switches and ST7LITE MCU

PDF	32 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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17 / 32 page

UM0277

Getting started

17/32

Figure 10.

Temperature control tab

3.5.2

Timing control

The Timing Control tab (Figure 11) controls the gate current width for the TRIACs, the delay

to switch ON the TRIACs Q1 (for compressor), the ZVS delay, the delay to activate defrost

and the defrost duration. Note that the initial parameters are given in Appendix F. These

parameters are sent and received by clicking on “Set” or “Get” buttons, respectively.

Figure 11.

Timing control tab

The ZVS delay is the delay between the AC mains zero voltage and the detection of this

zero voltage by MCU in order to synchronize the MCU orders with the AC mains voltage.

The MCU uses Zero Voltage Crossing (ZVC) events to synchronize the TRIACs' gate

current pulses. The LINE voltage is connected to the input pin through two resistors (R7 and

R8). An interruption will then occur at each ZVC event. As soon as the ZVC is detected, the

AUTO-RELOAD Timer is started and a routine is launched to define the PORT A

configuration. The required time introduces then a delay from the ZVS. The maximum delay

UM0277 Datasheet(PDF) 17 Page - STMicroelectronics