Nxp Semiconductors SSL2101 Evaluation Boards SSL2101T/DB/FBCB120V,598 SSL2101T/DB/FBCB120V,598 Scheda Tecnica

SSL2101

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As soon as the oscillator voltage is high again and the secondary stroke has ended, the 
circuit waits for a low drain voltage before starting a new primary stroke.

 shows the drain voltage together with the valley signal, the signal indicating the 

secondary stroke and the RC voltage.

The primary stroke starts some time before the actual valley at low ringing frequencies, 
and some time after the actual valley at high ringing frequencies.

 

 shows a typical curve for a reflected output voltage N at an output voltage of 

80 V. This voltage is the output voltage transferred to the primary side of the transformer 
with the factor N (determined by the turns ratio of the transformer). It shows that the 
system switches exactly at minimum drain voltage for ringing frequencies of 480 kHz, thus 
reducing the switch-on losses to a minimum. At 200 kHz, the next primary stroke is started 
at 33

 before the valley. The switch-on losses are still reduced significantly.

A: Start of new cycle with valley switching.

B: Start of new cycle in a classical PWM system.

drain

valley

secondary

ringing

secondary

stroke

primary

stroke

secondary

stroke

RC

oscillator

regulation level

A

B