STEVAL-IHM006V1 Datasheet, PDF (2/5 Pages) STMicroelectronics – AC/AC chopper driver

General circuit description
1 General circuit description
STEVAL-IHM006V1
Currently, the most widely used method to vary the AC mono-phase load voltage in applications
such as refrigerators, hydraulic pumps, fans and lamps consists in using the phase
partialization technique via a triac device. Although this simple and low cost solution has been
used for several years, it creates excessive harmonic distortion and has a consequent low
efficiency. Typical applications used to solve this problem are systems based on a complex
inverter drive, which are quite expensive.
The presented patented solution can solve third harmonic problems thanks to its switching
work mode. The induction motor is driven in high frequency mode by an innovative switch
topology, which delivers a silent and cost effective variable speed drive. The speed is controlled
) ^{by the motor voltage: the power switch runs in PWM mode and its duty cycle changes linearly}
t(s ^{to control the speed versus the torque.}
c The base circuit can be viewed as a double chopper that operates on a sinusoidal busdirectly
u _{from the 50-60Hz mains, without a preliminary AC-DC conversion type.}
rod ^{The double chopper is able to energize the load from any level of the sinusoidal voltagewave}
and demagnetize it via a free-wheeling current system, obtaining the voltage regulation and the
P _{current. This means that the circuit operates as an AC-AC converter or transformer and the}
te form of the current load is a perfect sinusoidal shape. The proposed circuit does not have any
le load type limitations. It works with any inductive-ohmic load with notable angles between the
o _{current and the voltage.}
bs _{The power can be controlled by varying the duty cycle of the PWM signal where the shape of}
O the current is sinusoidal due to the filtering effect of the inductive nature of the load.
- _{If the load has a reactive power, it can transit between load and line grid independently from the}
t(s) ^{power level and is not blocked or dissipated in any electronic parts of the circuit.}
c The control parameters (PWM modulation, reference signal and current sensing) are controlled
u _{through an MCU. The AC/AC chopper driver evaluation board is based on the ST7FLITE05}
d _{microcontroller (8-bit MCU with single voltage flash memory, ADC, timers, SPI, 1% internal RC}
Obsolete ^{Pro oscillator)}
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