Power integrations TOP100-4, TOPSwitch series User Manual

TOP100-4

TOPSwitch

Three-terminal Off-line PWM Switch

AC

IN

DRAIN

SOURCE

CONTROL

TOPSwitch

TOPSwitch SELECTION GUIDE

OUTPUT POWER RANGE

ORDER

PART

NUMBER

N*
N*
N*
N*
N*

FLYBACK

100/110 V

VAC

48 V

DC

PFC/

BOOST

100/110

VAC

July 2009

TOP100-4

CONTROL

V

C

Z

C

SHUNT REGULATOR/

ERROR AMPLIFIER

-

+

5.7 V

5.7 V

4.7 V

SHUTDOWN/

AUTO-RESTART

+

-

POWER-UP

RESET

0

INTERNAL
SUPPLY

1

DRAIN

÷ 8

EXTERNALLY

TRIGGERED
SHUTDOWN

I

FB

OSCILLATOR

R

E

D

MAX

CLOCK

SAW

THERMAL

SHUTDOWN

COMPARATOR

Figure 2. Functional Block Diagram.

Pin Functional Description

-

+

PWM

RSQ

Q

SRQ

+

-

V

I

LIMIT

CONTROLLED

TURN-ON

GATE

DRIVER

LEADING

Q

EDGE

BLANKING

MINIMUM

ON-TIME

DELAY

SOURCE

PI-1746-011796

DRAIN Pin:

Output MOSFET drain connection. Provides internal bias
current during start-up operation via an internal switched high­voltage current source. Internal current sense point.

CONTROL Pin:

Error amplifier and feedback current input pin for duty cycle
control. Internal shunt regulator connection to provide internal
bias current during normal operation. Trigger input for latching
shutdown. It is also used as the supply bypass and auto-restart/
compensation capacitor connection point.

SOURCE Pin:

Output MOSFET source connection. Primary-side circuit
common, power return, and reference point.

F

2

7 /09

DRAIN

SOURCE (TAB)

CONTROL

TO-220/3 (YO3A)

PI-1065A-110194

Figure 3. Pin Configuration.

TOP100-4

TOPSwitch

Family Functional Description

TOPSwitch is a self biased and protected
linear control current-to-duty cycle
converter with an open drain output.
High efficiency is achieved through the
use of CMOS and integration of the
maximum number of functions possible.
CMOS significantly reduces bias
currents as compared to bipolar or
discrete solutions. Integration eliminates
external power resistors used for current
sensing and/or supplying initial start-up
bias current.

During normal operation, the internal
output MOSFET duty cycle linearly
decreases with increasing CONTROL
pin current as shown in Figure 4. To
implement all the required control, bias,
and protection functions, the DRAIN
and CONTROL pins each perform
several functions as described below.
Refer to Figure 2 for a block diagram
and Figure 6 for timing and voltage
waveforms of the TOPSwitch integrated
circuit.

Control Voltage Supply

CONTROL pin voltage VC is the supply
or bias voltage for the controller and
driver circuitry. An external bypass
capacitor closely connected between the
CONTROL and SOURCE pins is
required to supply the gate drive current.
The total amount of capacitance
connected to this pin (CT) also sets the
auto-restart timing as well as control
loop compensation. VC is regulated in
either of two modes of operation.
Hysteretic regulation is used for initial
start-up and overload operation. Shunt
regulation is used to separate the duty
cycle error signal from the control circuit
supply current. During start-up, V
current is supplied from a high-voltage
switched current source connected
internally between the DRAIN and
CONTROL pins. The current source
provides sufficient current to supply the
control circuitry as well as charge the
total external capacitance (CT).

Auto-restart

I

D

MAX

B

Duty Cycle (%)

D

MIN

I

2.5 6.5 45

CD1

Figure 4. Relationship of Duty Cycle to CONTROL Pin Current.

IC

V

DRAIN

C

5.7 V

4.7 V

V

IN

Charging C



0

0

T

Off

(a)

IC

Charging C

5.7 V



4.7 V

V

C

0

C

DRAIN

V

IN

0

T

Off

Switching Switching

(b)

CT is the total external capacitance

connected to the CONTROL pin

Slope = PWM Gain

-16%/mA

IC (mA)

Switching

I



CD1

Discharging C

95%

Off

T

8 Cycles



Discharging C

5%

PI-1691-112895

I



CD2

T

Off

PI-1124A-060694

Figure 5. Start-up Waveforms for (a) Normal Operation and (b) Auto-restart.

7/ 09

F

3

V

IN

DRAIN

V

OUT

I

OUT

TOP100-4

V

IN

0

0

0

12 12 81

8

••• •••

V

C

0

12

I

0

C

1 2

Figure 6. Typical Waveforms for (1) Normal Operation, (2) Auto-restart, (3) Latching Shutdown, and (4) Power Down Reset.

Shutdown/Auto-restart

To minimize TOPSwitch power
dissipation, the shutdown/auto-restart
circuit turns the power supply on and off
at a duty cycle of typically 5% if an out
of regulation condition persists. Loss of
regulation interrupts the external current

812 81

••• •••

removing and restoring input power, or
momentarily pulling the CONTROL pin
below the power-up reset threshold resets
the latch and allows TOPSwitch to
resume normal power supply operation.
VC is regulated in hysteretic mode when

the power supply is latched off.
into the CONTROL pin. VC regulation
changes from shunt mode to the
hysteretic auto-restart mode described
above. When the fault condition is
removed, the power supply output
becomes regulated, VC regulation returns
to shunt mode, and normal operation of
the power supply resumes.

Overtemperature Protection

Temperature protection is provided by a

precision analog circuit that turns the

output MOSFET off when the junction

temperature exceeds the thermal

shutdown temperature (typically 145°C).

Activating the power-up reset circuit by

removing and restoring input power or

Latching Shutdown

The output overvoltage protection latch
is activated by a high-current pulse into
the CONTROL pin. When set, the latch
turns off the TOPSwitch output.
Activating the power-up reset circuit by

momentarily pulling the CONTROL pin

below the power-up reset threshold resets

the latch and allows TOPSwitch to

resume normal power supply operation.

VC is regulated in hysteretic mode when

the power supply is latched off.

45 mA

High-voltage Bias Current Source

This current source biases TOPSwitch
from the DRAIN pin and charges the
CONTROL pin external capacitance
(CT) during start-up or hysteretic
operation. Hysteretic operation occurs
during auto-restart and latched
shutdown. The current source is switched
on and off with an effective duty cycle of
approximately 35%. This duty cycle is
determined by the ratio of CONTROL
pin charge (IC) and discharge currents
(I

CD1

and I

). This current source is

CD2

turned off during normal operation when
the output MOSFET is switching.

V

C(reset)

143

PI-1119-110194

7/ 09

F

5

TOP100-4

General Circuit Operation

Primary Feedback Regulation

The circuit shown in Figure 7 is a simple
5 V, 5 W bias supply using the TOP100.
This flyback power supply employs
primary-side regulation from a
transformer bias winding. This approach
is best for low-cost applications requiring
isolation and operation within a narrow
range of load variation. Line and load
regulation of ±5% or better can be
achieved from 10% to 100% of rated
load.

Voltage feedback is obtained from the
transformer (T1) bias winding, which
eliminates the need for optocoupler and
secondary-referenced error amplifier.
High-voltage DC is applied to the
primary winding of T1. The other side
of the transformer primary is driven by

the integrated high-voltage MOSFET

transistor within the TOP100 (U1). The

circuit operates at a switching frequency

of 100 kHz, set by the internal oscillator

of the TOP100. The clamp circuit

implemented by VR1 and D1 limits the

leading-edge voltage spike caused by

transformer leakage inductance to a safe

value. The 5 V power secondary winding

is rectified and filtered by D2, C2, C3,

and L1 to create the 5 V output voltage.

The output of the T1 bias winding is

rectified and filtered by D3, R1, and C5.

The voltage across C5 is regulated by

U1, and is determined by the 5.7 V

internal shunt regulator at the

CONTROL pin of U1. When the

rectified bias voltage on C5 begins to

exceed the shunt regulator voltage,

current will flow into the control pin.
Increasing control pin current decreases
the duty cycle until a stable operating
point is reached. The output voltage is
proportional to the bias voltage by the
turns ratio of the output to bias windings.
C5 is used to bypass the CONTROL pin.
C5 also provides loop compensation for
the power supply by shunting AC
currents around the CONTROL pin
dynamic impedance, and also determines
the auto-restart frequency during start­up and auto-restart conditions. See DN­8 for more information regarding bias
supplies.

D2

1N5822

VR1

P6KE91

D1

UF4004

C2

330 µF

25 V

D3

1N4148

DC

INPUT

C5

47 µF

DRAIN

SOURCE

CONTROL

U1

TOP100YAI

Figure 7. Schematic Diagram of a Minimum Parts Count 5 V, 5 W Bias Supply Utilizing the TOP100.

F

6

7 /09

T1

R1

22 Ω

L1

(Bead)

5 V

C3

150 µF

25 V

RTN

CIRCUIT PERFORMANCE:

Load Regulation - ±4%

(10% to 100%)

Line Regulation - ±1.5%

95 to 185 V DC

Ripple Voltage ±25 mV

PI-1767-020296