QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-D
ACTIVE RESET ISOLATED 18-72V INPUT TO 24V @5A DC/DC POWER CONVERTER
3
Figure 1. Proper Measurement Equipment Setup
Figure 2. Scope Probe Placement for Measuring Input or Output Ripple
ACTIVE RESET CIRCUIT
The Active Reset circuit on DC1317A-D demo board
consists of a small P-Channel MOSFET Q13 and
reset capacitor C25. The MOSFET Q13 is used to
connect the reset capacitor across the transformer
T1 primary winding during the reset period when
Q1 MOSFET is off. The voltage across capacitor
C25 automatically adjusts with the duty cycle to
provide complete transformer reset under all oper-
ating conditions.
Also the active reset circuit shapes the reset voltage
into a square waveform that results in lower drain
voltages for Q1 and Q2 MOSFETs. The lower
MOSFET drain voltages allow lower voltage and
lower Rdson MOSFETs to be used. The MOSFETs
must be avalanche rated for the peak reset voltage.
If non-avalanche rated MOSFETs are used a proper
drain voltage derating should be used.
The main benefit of active reset circuit in the case of
DC1317A-D demo board is high efficiency (shown
in Figure 3), wide input range, high power density
