TOP247 データシートの表示（PDF） - Power Integrations, Inc

部品番号

コンポーネント説明

メーカー

TOP247

Extended power, design elexible, integrated off-line switcher

Power Integrations, Inc 

TOP242-250

CONTROL (C) Pin Operation

The CONTROL pin is a low impedance node that is capable of

receiving a combined supply and feedback current. During

SOURCE through resistor RE as shown in Figure 2. This

current flowing through RE controls the duty cycle of the power

MOSFET to provide closed loop regulation. The shunt

normal operation, a shunt regulator is used to separate the feed-

back signal from the supply current. CONTROL pin voltage

regulator has a finite low output impedance ZC that sets the

gain of the error amplifier when used in a primary feedback

VC is the supply voltage for the control circuitry including the

MOSFET gate driver. An external bypass capacitor closely

configuration. The dynamic impedance ZC of the CONTROL

pin together with the external CONTROL pin capacitance sets

connected between the CONTROL and SOURCE pins is the dominant pole for the control loop.

required to supply the instantaneous gate drive current. The

total amount of capacitance connected to this pin also sets the When a fault condition such as an open loop or shorted output

auto-restart timing as well as control loop compensation.

prevents the flow of an external current into the CONTROL

pin, the capacitor on the CONTROL pin discharges towards

When rectified DC high voltage is applied to the DRAIN pin 4.8 V. At 4.8 V, auto-restart is activated which turns the output

during start-up, the MOSFET is initially off, and the MOSFET off and puts the control circuitry in a low current

CONTROL pin capacitor is charged through a switched high standby mode. The high-voltage current source turns on and

voltage current source connected internally between the DRAIN charges the external capacitance again. A hysteretic internal

and CONTROL pins. When the CONTROL pinGvoletagne eVCral sIunppflyourndmer-vaolttaigoe cnom&paraTtorakebeplseVCowfithiCn aownindtoewnts

reaches approximately 5.8 V, the control circuitry is activated of typically 4.8 V to 5.8 V by turning the high-voltage current

and the soft-start begins. The soft-start circuit gradually

increases the duty cycle of the MOSFET from zero to the maxi-

source on and off as shown in Figure 8. The auto-restart

circuit has Pa drivoided-buy-ecigtht Scouentleer wchitcoh prrevGentus tihde oeut- 1

mum value over approximately 10 ms. If no external feedback/ put MOSFET from turning on again until eight discharge/charge

supply current is fed into the CONTROL pin by the end of the

soft-start, the high voltage current source is turned off and the

cycles have elapsed. This is accomplished by enabling the

Data Sheets 2 output MOSFET only when the divide-by-eight counter reaches

CONTROL pin will start discharging in response to the supply full count (S7). The counter effectively limits TOPSwitch-GX

current drawn by the control circuitry. If the power supply is

designed properly, and no fault condition such as open loop or

power dissipation by reducing the auto-restart duty cycle to

typically 4%. Auto-rAestpartpmloidce acotnitoinunes Nuntoil toeutpsut 3

shorted output exists, the feedback loop will close, providing voltage regulation is again achieved through closure of the

external CONTROL pin current, before the CONTROL pin

voltage has had a chance to discharge to the lower threshold

feedback loop.

Design Ideas 4

voltage of approximately 4.8 V (internal supply under-voltage Oscillator and Switching Frequency

lockout threshold). When the externally fed current charges

the CONTROL pin to the shunt regulator voltage of 5.8 V, cur-

The internal oscillator linearly charges and discharges an

Design Tools 5 internal capacitance between two voltage levels to create a

rent in excess of the consumption of the chip is shunted to sawtooth waveform for the pulse width modulator. This

Quality and Reliability 6

VLINE

0V

VUV

VC

0V

VDRAIN

S7

S0

Package Information 7

DPA-Switch DC-DC Seminar 8 S1 S2

S6 S7 S0 S1 S2

S6 S7

S0

S1 S2

S6 S7 S7

5.8 V

4.8 V

LinkSwitch & TinySwitch-II AC-DC Seminar 9

0V

TOPSwitch-GX AC-DC Seminar 10

VOUT

0V

Sales Representatives and Distributors 11

1

2

3

2

4

Note: S0 through S7 are the output states of the auto-restart counter

Figure 8. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-restart (4) Power Down.

PI-2545-082299

6

H

9/02

Share Link: