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Application Note: SY5040
CCM+QR Mode SSR Flyback Controller
Preliminary Specification
General Description
SY5040 is a peak current mode SSR flyback controller that combine CCM and QR mode together to minimize transformer size and achieve high efficiency. Under low line and heavy load condition, SY5040 works under CCM, while under high line or medium load, it works under QR mode (valley switching). SY5040 adopts frequency fold back control when load decreases to achieve high average efficiency. When load decreases to very light level, SY5040 will enter burst mode and switching frequency is fixed to 25kHz to avoid audible noise. SY5040 also provides comprehensive and reliable protections including brownout protection, output OVP, external OTP, OLP, VCC OVP, internal OTP, etc.