Modulated snubber driver for active snubber network

摘要

A switching boost type voltage regulator includes a resonant snubber network (C1, Q2, L2, CR2, CR3) connected in parallel with its FET power switch (Q1). The snubber includes a FET auxiliary switch (Q2) that is connected and turned on in order to reduce the voltage across the FET power switch (Q1) to a zero level at its turn-on transition. A driver circuit, driven by a voltage regulating pulse width modulation (PWM) pulse, initially turns on the FET auxiliary switch (Q2) to reduce a voltage across the FET power switch (Q1) and then turns on the FET power switch (Q1) when the voltage across it drops below a threshold level. The FET auxiliary switch is turned off when the FET power switch is turned on. A latch circuit (Q3, Q4) insures the complementary states of these two switches. The snubber circuit is disabled a near to zero voltage regardless of line and load levels and hence the power dissipation in the snubber is significantly reduced.