Rev. 1.00
100
August 29, 2018
Rev. 1.00
101
August 29, 2018
HT45F6530
AC Voltage Regulator Flash MCU
HT45F6530
AC Voltage Regulator Flash MCU
Application Description
Introduction
The main function of AVR products is to measure the input voltage, detect the AC zero-crossing
signal and then control a relay to switch the output voltage. Additional features include those for
protection against over-voltage, under-voltage and temperature. By including these functions, when
the AC input voltage is unstable, the relay will be switched to the internal multi-tap autotransformer
output voltage to continuously provide the backend loads with a stable voltage thus avoiding load
damage or shorter service life. Because there could be contact arcing during the internal relay
switching, it is necessary to control the relay timing to ensure it only switches during AC zero
crossing points to avoid relay damage. This Holtek AVR dedicated MCU provides full control
signals for all of the above functions, the details of which are described in the following sections.
Functional Description
AVR Input/Output Voltage Measurement Operating Principle
The D/A converter outputs a 2.5V bias voltage and the operational amplifier together with external
resistors form an amplifier circuit. By using these functions the AC waveform will be converted to a
sine wave with a 2.5V zero point. The peak-to-peak values can be obtained through continuous A/D
conversion during an AC cycle to convert the input/output voltage.
AVR Zero Crossing Detection Operating Principle
The AC input waveform conversion circuit is internally connected to a comparator where it is
compared with the D/A converter 2.5V output voltage. When this value is greater than 2.5V it will
output a high level. When it is lower than 2.5V a low level will be output and an interrupt generated.
AVR Relay Delay Measurement Operating Principle
The AC output waveform conversion circuit is internally connected to a comparator where it is
compared with the D/A converter output voltage. The relay will be turned on at the point where an
AC zero crossing and a rising edge both occur, therefore measure when the output voltage changes
and the time interval is the relay turn-on delay time. About 2~3ms before the AC zero crossing and
rising edge the relay is turned off, therefore measure when the output voltage changes from low to
high then low again, the time interval is the relay turn-off delay time.