EPR-31 Datasheet, PDF (9/36 Pages) Power Integrations, Inc. – Engineering Prototype Report for EP-31 Multiple Output 180 W AC-DC Power

01-Feb-05
EPR-31 – Multi-Output, 180 W, PC Main Power Supply
The dissipation in the entire circuit (D1, C4, and D3–D5) measures only about
1.5 W at maximum load.
TOPSwitch-GX uses voltage mode control to regulate the main output voltage.
Output transient load-step waveforms show very good responsiveness (optimal
performance) and the control loop gain and phase margin plots show that the
control loop is stable with adequate margin.
This design uses a very simple remote ON/OFF circuit (see Figure 5). When the
ON line (the green wire in the output cable) is momentarily connected to the
output return (grounded), Q3 turns on, pulling current through the U3-LED, which
turns on Q7, which pulls down R12, enabling U1 to start switching. When the
output comes up into regulation before C19 discharges, Q3 is kept on through
R28, and U1 keeps switching. IC U1 stops switching if output regulation is lost.
Then the ON line must be toggled (ungrounded and then re-grounded) to restart
the supply.
When the ON line is ungrounded, it is internally pulled up (by R33) to the +5 V
standby and U1 remains disabled. The +5 V standby is always operating above
a DC rail voltage of 100 VDC. Grounding the ON line will turn the main supply
on, if the AC line voltage is above the UV threshold and there is not a fault
condition. If a fault condition exists, U1 will stay in its auto-restart mode until C19
discharges. The ON line must be toggled again to attempt another restart.
*Note 1: If the remote ON line is grounded (main power enabled) when AC is first
applied to the supply, the main converter will automatically turn on. However, if
AC is brought up too slowly (i.e. adjusting a variac), the supply will not turn on
and the ON line will have to be toggled to turn on the supply. On the output
interconnect board that is provided with the DAK Kit, the ON line is already
connected to an ON/OFF switch, enabling the supply to be turned ON and
OFF.
Page 9 of 36
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