MP6005

– WIDE-INPUT, HIGH-EFFICIENCY FLYBACK AND FORWARD CONTROLLER

MP6005 Rev. 1.0

www.MonolithicPower.com

18

2/5/2021

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2021 MPS. All Rights Reserved.

If VSENSE exceeds the current-limit threshold

(typically 160mV), the MP6005 turns off the

GATE output.

Then the internal oscillator begins the next

cycle and senses the current again. The

MP6005 limits the MOSFET current cycle by

cycle.

Error Amplifier (EA)

In

PSR

mode,

the

MP6005

senses

the

feedback voltage (VFB) during the flyback period

with the feedback pulse signal. The feedback

signal is then held and fed to the error amplifier

(EA). The EA regulates VCOMP based on the

feedback

signal,

and

VCOMP

controls

the

transformer peak current to regulate VOUT.

In SSR mode, the internal EA is disabled and

the COMP pin is pulled up by an internal

resistor. The external optocoupler can be

connected to COMP for VOUT signal feedback.

Light-Load Control

Under light-load conditions in PSR mode, VCOMP

decreases to regulate the low transformer peak

current. If the peak current signal is below

36mV, the

MP6005

stops

decreasing the

transformer current, and instead decreases the

frequency. As a result, the transferred energy

decreases, and VOUT is regulated.

In light-load PSR mode, the MP6005 sets the

minimum frequency above 30kHz. This helps

the device detect the output voltage and avoid

audible noise. The minimum frequency requires

some load to maintain VOUT, so that VOUT does

not rise and trigger over-voltage protection

(OVP).

Under light-load conditions in SSR mode, the

MP6005 maintains a fixed frequency and VCOMP

continues to drop toward the PSM threshold.

Over-Voltage Protection (OVP)

The

MP6005

includes

over-voltage

protection (OVP). If VFB exceeds 125% of VREF,

the MP6005 turns off the GATE signal and

enters hiccup mode. Once the fault has been

removed, the MP6005 turns on again after a

340ms

delay,

and

then

resumes

normal

operation. Connect the FB pin to GND if the

OVP function is not used.OVP sampling has a

blanking time to avoid mistriggering due to the

oscillation of

the

leakage

inductance

and

parasitic capacitance.

Overload Protection (OLP)

The MP6005 limits the peak current cycle by

cycle

under

OCP

conditions.

If

the

load

continues to increase after triggering OCP, VOUT

decreases and the peak current triggers OCP

for each cycle.

The

MP6005

sets

overload

detection

by

monitoring VSENSE. Once the internal soft start is

complete, overload protection (OLP) turns on. If

an OCP signal longer than 4.8ms is detected,

the MP6005 turns off the gate driver. After a

340ms delay, the MP6005 turns on again with

the next cycle. During OLP, a 50µs one-shot

timer is activated after one OCP pulse. This

means if there is one OCP pulse in a 50µs

period, the MP6005 registers this event as

OCP. If the OCP condition is removed before

4.75ms,

the

MP6005

resumes

normal

operation.

Short-Circuit Protection (SCP)

When the output is shorted to GND, the

MP6005 works in OCP mode and the current is

limited cycle by cycle.

If the peak current is not limited by the 160mV

VSENSE in each cycle because of the gate

driver’s minimum on time, the current may run

out of control and the transformer may saturate.

If VSENSE reaches 300mV, the MP6005 turns off

the gate driver and enters hiccup protection

with a 340ms off time.

Once

the

short

circuit

is

removed,

VOUT

recovers after a 340ms delay and then enters

the next cycle.

Soft Start (SS)

The MP6005 employs soft start (SS) by

charging an internal capacitor from a current

source. During the soft-start period, the SS

signal ramps up slowly. In the event of a

command shutdown, thermal shutdown, or

protection condition, the soft-start capacitor is

completely discharged.

In PSR mode, the soft-start signal clamps the

feedback VREF. From 0V to 2V, the feedback

reference soft-start time is typically 4.7ms.

In SSR mode, the soft-start signal clamps VCOMP

until it reaches the switching current level. The

soft-start signal continues to ramp up at the

same rate. VCOMP’s ramp time from 1.5V to 3.5V

is typically 4.7ms.