CS5124 データシートの表示（PDF） - Cherry semiconductor

部品番号

コンポーネント説明

メーカー

CS5124

High Performance, Integrated Current Mode PWM Controllers

Cherry semiconductor 

Application Information: continued

be used in synchronized operation, the inductor value

should be recalculated to work with the slope compensa-

tion ramp reduced to 67% of the normal value.

Powering the CS5124/6 from a Transformer Winding

There are numerous ways to power the CS5124/6 from a

transformer winding to enable the converter to be operated

at high efficiency over a wide input range. Two ways are

shown in the application circuits.

The CS5124 application circuit (main application diagram)

is a flyback converter that uses a second flyback winding

to power VCC. R4 improves VCC regulation with load

changes by snubbing the turn off spike. Once the turn off

spike has subsided the voltage of this winding is voltage

proportional to the voltage on the main flyback winding.

This voltage is regulated because the main winding is

clamped by the regulated output voltage.

In the CS5126 application circuit (below) an extra winding

is added to the forward inductor to power VCC. This wind-

ing is phased to conduct during the off time of the forward

converter and performs the same function as the flyback

winding above.

A flyback winding from a forward transformer can also be

used to power VCC. Ideally the transformer volt-second

product of a forward converter would be constant over the

range of line voltages and load currents; and the trans-

former inductance could be chosen to store the required

level of energy during each cycle to power VCC. Even

though the flyback energy is not directly regulated it

would remain constant. Unfortunately in a real converter

there are many non-ideal effects that degrade regulation.

Transformer inductance varies, converter frequency varies,

energy stored in primary leakage inductance varies with

output current, stray transformer capacitances and various

parasitics all effect the level of energy available for VCC. If

too little energy is provided to VCC, the bootstrapping cir-

cuit must provide power and efficiency will be reduced. If

too much energy is provided VCC rises and may damage

the controller. If this approach is taken the circuit must be

carefully designed and component values must be con-

trolled for good regulation.

Additional Application Diagram

36-75VIN

L1

10µH

C3

0.2µF, 100V

C2

1.5µF,

100V

C1

1.5µF,

100V

ENABLE

SYNC

48VRTN

R9

10k C4

1000pF

CTX15-14526

T1 CTX15-14527

R2

200k

R1

39k

R6

17.4k

D3

11V

C5

1µF,

25V

Q1

F2T493

D2

MMBD6100L

T2

Q2

IRF634

C6

390pF

R4

0.2Ω

1/4W

MBRB2060CT

C12

.01µF

R7

R3

2k

30.1k

R10

C11

10k 0.1µF

VCC

Gnd

UVLO GATE

SYNC

IS

SS

VFB

CS5126

C10

1000pF

U2

TPS5908

C9

.01µF

R8

10.0k

5VOUT

C7

47µF

C8

47µF

ISOLATED

RTN

48V to 5V, 5A forward converter using the CS5126

9

Share Link: