Rev. H 05/22

4

MinE-CAP

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MinE-CAP Functional Description

The MinE-CAP IC comprises a digital controller and high-voltage

power switch which connected in series with a low-voltage (160 V)

bulk electrolytic capacitor in a power converter. The MinE-CAP IC

connects this low-voltage capacitor into the power supply at low input

line voltage conditions and disconnects it at high input line voltages.

A high-voltage (400 V) capacitor is connected in parallel to support

power delivery in high line conditions. The effective input capacitance

is equivalent the sum of C

LV and CHV at low input line to maintain the

same minimum DC voltage to the DC/DC converter stage. At high

input line condition the switch is disabled to ensure the voltage

across C

LV does not exceeded the rated voltage of the capacitor.

The MinE-CAP IC also includes a control signal transmitted from the

MinE-CAP LINE pin to control the start-up and fault shutdown of an

InnoSwitch IC via its V pin. Figure 4 illustrates the high level block

diagram.

Start-Up

Inrush Management

Upon application of AC input, the MinE-CAP controller is in the off-

state and the power switch is open. The C

LV is not engaged in the

circuit and only C

HV is charged by the AC input. CHV is significantly

smaller than C

LV and the inrush stress on the bridge rectifier and fuse

is therefore greatly reduced. The MinE-CAP IC then performs

controlled charging of C

LV as described in the next section. This

controlled charging of the C

LV allows MinE-CAP designs to eliminate

the inrush NTC, improving the overall system design by removing a

thermal hotspot and increases conversion efficiency.

Power-Up

The MinE-CAP Bypass is derived externally through direct connection

with the InnoSwitch BPP pin. Note that during this time, the

InnoSwitch IC is disabled from delivering power since the current

received by the InnoSwitch V pin is I

INJECT(UV) which is below brown-in

threshold of InnoSwitch (further details on V pin operation available

in InnoSwitch data sheets).

Active Charging

Once the BYPASS (BP) pin reaches regulation the MinE-CAP controller

waits for the bulk voltage to be above the MinE-CAP brown-in

threshold (I

UV+) measured on the VTOP pin. After brown-in, the

controller enters a wait state for 20 ms to ensure power supply input

voltage levels have stabilized. After that time, the MinE-CAP IC

samples the bulk DC voltage to determine which of two possible C

LV

charge up schemes to adopt as described below.

In low-line start-up conditions (V

IN < 150 VAC), the MinE-CAP IC

performs precisely controlled active charging of C

LV. At low-line

start-up condition, it is important to pre-charge C

LV to support full

power capability prior to enabling the InnoSwitch. The MinE-CAP IC

controls the internal high-voltage switch as a current source and uses

a precise constant current, pulse charging of C

LV, see Figure 6. This

algorithm allows fast charging of C

LV and ensures PSU is able to

deliver full power in less than 250 ms from initial AC line connection.

VCLV

IDS

VCLV

IDS

PI-9217-082520

Figure 6. Charging Algorithm used for Low-Line Start-Up.

In high-line start-up condition (V

IN > 150 VAC), the active charging

algorithm of C

LV described above is not employed. When selected

according to Figure 2, C

HV alone can deliver full power converter

output power at line voltages above 150 VAC. The InnoSwitch power

control IC is therefore enabled immediately using the V pin output

signal while C

LV is trickle charged at a lower rate until the steady-state

C

LV voltage is reached. The voltage across CLV is subsequently

precisely monitored and recharged as required depending on input

line conditions.

Steady-State

Power Switch Control Logic

The resistor connected to the VTOP pin is used to sense the line

voltage. During normal operation the MinE-CAP IC is fully on while

the bulk voltage remains below the user defined threshold (V

COV+).

V

COV± = ICOV± × RTOP

where

I

COV- = ICOV+ - ICOV(H)

In this condition C

LV contributes to the output power delivery. Once

the bulk voltage reaches V

COV+, the MinE-CAP IC is turned off to

maintain C

LV below its rated voltage. In this state, only CHV is

contributing to output power delivery.

The MinE-CAP IC measures the VBOT pin voltage to determine if

voltage on C

LV and CHV are equal. Once the DC bus voltage falls

below V

COV- and if the MinE-CAP IC determines CLV and CHV voltages

are equal (VBOT pin voltage close to 0 V), the MinE-CAP power

switch is turned on and C

LV is reengaged as an energy source for the

power converter.

As such, the MinE-CAP IC is designed to turn on and off, engaging

and disengaging C

LV during each AC line cycle, as may be required at

intermediate AC line voltages. Figure 7 summarizes the steady-state

control of the MinE-CAP power switch.