Offline UPS - low frequency transformer
Offline (standby) UPS is mainly used for Small Office and Home Office, also called SOHO. Offline UPS is usually between 0 and 10 kVA. Mainly covered with discrete power semiconductor solutions, it is usually divided into low frequency and high-frequency transformer-based systems. It is used when AC line voltage is present a relay bypasses the inverter, which remains off. The battery charger operates to maintain full charge. If the AC power fails the relay switches, the UPS output over to the inverter, which starts up after a short interruption of 10-20 ms to supply backup power.
- 50/60 Hz iron core transformers which are large and heavy
- Sine or square wave output voltage
- Full-bridge or push-pull inverter/charger while full-bridge topology is mainly used
- Robust against AC line surges
UPSs for use in Small Office or Home Office (SOHO) environments typically include MOSFET-based inverters that operate from 12 V or 24 V lead-acid batteries (24 V systems are comprised of two series-connected 12 V batteries). Higher battery voltages are required to limit operating currents in higher power-rated systems. 42 V and 72 V systems also exist for the same reason; these are somewhat less common. Batteries may be external or internal to the UPS; car batteries are used externally and sealed lead-acid batteries internally.
The XMC™ microcontroller family based on ARM® Cortex®-M cores, is suitable for real-time critical applications where an industry-standard core is needed. It is dedicated to applications in the segments of power conversion, factory and building automation, and transportation, as well as home appliances. The XMC1000 series brings together the ARM® Cortex®-M0 core and market-proven and differentiating peripherals in a leading-edge 65 nm manufacturing process.
XMC13x option offers the functionality of the CCU8 timer/PWM module. It is necessary to provide the required gate drive signals. A clock speed of 32 MHz provides sufficient granularity of adjustment for the PWM outputs switching at 20 kHz. Since the MATH co-processor and BCCU LED lighting engine is not required for example in an offline UPS application, the XMC1301 is sufficient. For example, the 16-pin PG-TSSOP-16-8 packaged XMC1301-T016F0032 variant has 32 kB of Flash memory and 16 KB of SRAM and enough I/O pins to support the required offline UPS functions.
The firmware can be developed using the DAVETM IDE, which can be downloaded free of charge. Programming and debugging is carried out via the XMCTM Link isolated debug probe. Create your project within DAVETM IDE containing the device definition, settings and source files required to compile and build the executable code, which can be downloaded into the Flash program memory of the XMCTM controller. There are several programming/debugging protocols available.