MP6005

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

MP6005 Rev. 1.0

www.MonolithicPower.com

17

2/5/2021

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COMP pin, and controls the transformer peak

current to match the regulated output voltage.

Secondary-Side Regulation (SSR) Mode

The MP6005 can work in secondary-side

regulation (SSR) mode. In SSR mode, the VOUT

signal is fed back to the COMP pin through one

optocoupler, and the PSR feedback voltage

detection is disabled. The FB pin should be

connected to GND.

The MP6005 has a fixed frequency while in

SSR mode under light-load conditions. The

peak current continues to drop towards VCOMP

until the PSM threshold is triggered. The 36mV

minimum current limit does not work in SSR

mode.

In SSR mode, the MP6005 supports both

flyback and forward topology. In PSR mode, the

MP6005 only supports flyback topology.

Output Voltage Compensation

In PSR mode, the auxiliary winding waveform

reflects the secondary-side winding voltage, but

the output voltage differs from the winding

output voltage due to the output diode voltage

drop and the power winding resistance (see

Figure 4). The dropout voltage varies as the

conduction current changes. As the current

varies, the resistance from the SENSE pin to

GND sets the compensation gain of the dropout

voltage. The current-sense (CS) signal is

filtered internally, and controls the current

sinking from the FB pin based on the average

voltage from the SENSE pin. There are three

types of current gain from the average VSENSE to

the FB sinking current (see Table 2 for SENSE

programming options). The FB sinking current

creates a voltage drop on the FB

pin’s high-side

(HS) feedback resistor to compensate for VOUT.

GATE

RSENSE

VIN

+

-

From Auxilary

Winding

RREG

R1

R2

Current

Mirror

IREG is set by VSENSE and

RREG + RSENSE

EA

VREF

COMP

Figure 4: Output Voltage Compensation

The voltage compensation function is disabled

in SSR mode.

Frequency Dithering

The MP6005 has a frequency dithering circuit

that

minimizes

electromagnetic

interference

(EMI). During steady state, the frequency is

fixed internally, but the frequency dithering

circuit is added to the configured frequency with

a 1.5kHz modulation. In PSR mode, frequency

dithering is fixed at ±6% of the switching

frequency. In SSR mode, frequency dithering

can be set at ±3%, ±6%, or ±9%, depending on

the resistor connected from the SENSE pin to

GND.

Table

2

shows

dithering

and

VOUT

compensation programming options.

Table 2: SENSE Program Options

SENSE to GND

Resistance (k

Ω) (13)

PSR Mode

SSR

Mode

Min

Typ

(1%)

Max

Dither

Range

(kHz)

IFB / VSENSE

Ratio

(µA/mV)

Dither

Range

(kHz)

0

0

1.3

0

0

0

3

3.3

3.6

±15

0.05

±7.5

6.2

6.8

7.5

±15

0.1

±15

12.7

12.7

13

±15

0.2

±22.5

24.9

25.5

28

±15

0

±22.5

After start-up, the SENSE detection current

continues for about 200µs. Typically, a resistor

from the SENSE pin to GND is sufficient. An

additional capacitor from SENSE to GND may

be required for filtering in a noise environment.

Notes:

13) RSENSE-GND is the resistance from the SENSE pin to GND,

which includes the CS resistor from the MOSFET source to

GND and the resistor from the MOSFET source to the

SENSE pin.

Current

Sense

(CS)

and

Over-Current

Protection (OCP)

The MP6005’s external MOSFET current is

sensed by the SENSE pin, which amplifies

VSENSE

to

feed

the

high-speed

current

comparator for current control mode. The

current comparator uses VSENSE and the slope

compensation

as

one

of

its

inputs,

and

compares that value to VCOMP. If the amplified

current exceeds VCOMP, then the comparator

output decreases and turns off the power

MOSFET.