EVL150W-ADP-SR View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

EVL150W-ADP-SR

12 V - 150 W resonant converter with synchronous rectification using the L6563H, L6599A, and SRK2000

STMicroelectronics 

AN3233

Main characteristics and circuit description

Figure 2. Burst mode circuit block diagram

to power transformer

to FB optocoupler

L6599A

RFMIN

2V

RFB

Standby

-

Comp.

+

1.24V

STBY

RBM RBM

RCS

TSM1014

Rlim

TSC101

CC_OUT

-

Comp. 1.25V

+

CC-

V_REF

OUT

RH

CC+

+

VP

E/A.

-

VM

100

RL

RHts

to load

The output current is sensed by a resistor (RCS); the voltage drop across this resistor is

amplified by TSC101, a dedicated high side current sense amplifier; its output is compared

to a set reference by the TSM1014; if the output load is high, the signal fed into the CC- pin

is above the reference voltage, CC_OUT stays down and the optocoupler transistor pulls up

the L6599A’s STBY pin to the RFMIN voltage (2 V), setting continuous switching operation

(no burst mode); if load decreases, the voltage on CC- falls below the set threshold,

CC_OUT goes high opening the connection between RFMIN and STBY and so allowing

burst mode operation by the L6599A.

RCS is dimensioned considering two constraints. The first is the maximum power dissipation

allowed, based on the efficiency goal. The second limitation is imposed by the necessity to

feed a reasonable voltage signal into the TSM1014A inverting input. In fact, signals which

are too small would affect system accuracy.

On this board, the maximum acceptable power dissipation has been set to Ploss,MAX = 500

mW. RCS maximum value is calculated as follows:

RCS,MAX

= Ploss,MAX

Io2ut,MAX

= 3.2mΩ

The burst mode threshold is set at 5 W corresponding to CBM = 417 mA output current at 12

V.

Choosing VCC+,min = 50 mV as the minimum reference of TSM1014A, which allows a good

signal-to-noise ratio, the RCS minimum value is calculated as follows:

RCS,min

=

VCC+,min

100 ⋅ CBM

= 1.2mΩ

The actual value of the mounted resistor is 2 mΩ, corresponding to Ploss = 312 mW power

losses at full load. The actual resistor value at burst mode threshold current provides an

output voltage by TSC101 of 83 mV. The reference voltage of TSM1014 VCC+ must be set at

this level. The resistor divider setting the TSM1014 threshold RH and RL should be in the

range of kilo-ohms to minimize dissipation. By selecting RL = 22 kΩ, the right RH value is

obtained as follows:

Doc ID 17595 Rev 1

7/35

Share Link: