TNY174PN 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

TNY174PN

TinySwitch-LT Family Energy Efficient, Offline Switcher with Enhanced Flexibility and Extended Power Range®

Power Integrations, Inc 

TNY174-180

D1

1N4007

F1

J1 3.15 A

85-265 RV1

VAC 275 VAC

J2

D3

1N4007

D2

1N4007

C1

6.8 μF

400 V

D4

1N4007

L1

1 mH

*R5 is optional

†C7 is configurable to adjust

U1 current limit, see circuit

description

VR1

P6KE150A

C2

22 μF

400 V

R1

1 kΩ

R2

100 Ω

C4

10 nF

1 kV

C5

2.2 nF

250 VAC

NC T1 8

D7

BYV28-200

1

6

3

R7

4 20 Ω

L2

Ferrite Bead

3.5 × 7.6 mm

+12 V, 1 A

C10

1000 μF

25 V

C11 J3

100 μF

25 V J4

RTN

D5

1N4007GP

VR2

1N5255B

28 V

D

EN

S BP/M

S

TinySwitch-LT C7 †

U1

100 nF

TNY178P

50 V

R8*

21 kΩ

1%

2

5

R3

47 Ω

1/8 W

D6

UF4003

C6

1 μF

60 V

VR3

BZX79-C11

11 V

U2

PC817A

R6

390 Ω

1/8 W

R4

2 kΩ

1/8 W

PI-4773-073107

Figure 12. TNY178P, 12 V, 1 A Universal Input Power Supply.

Applications Example

The circuit shown in Figure 12 is a low cost, high efficiency,

flyback power supply designed for 12 V, 1 A output from

universal input using the TNY178.

The supply features primary sensed output overvoltage latching

shutdown protection, high efficiency (>80%), and very low no-

load consumption (<50 mW at 265 VAC). Output regulation is

accomplished using a simple zener reference and optocoupler

feedback.

The rectified and filtered input voltage is applied to the primary

winding of T1. The other side of the transformer primary is

driven by the integrated MOSFET in U1. Diode D5, C2, R1,

R2, and VR1 comprise the clamp circuit, limiting the leakage

inductance turn-off voltage spike on the DRAIN pin to a safe

value. The use of a combination a Zener clamp and parallel

RC optimizes both EMI and energy efficiency. Resistor R2

allows the use of a slow recovery, low cost, rectifier diode by

limiting the reverse current through D5. The selection of a

slow diode also improves efficiency and conducted EMI but

should be a glass passivated type, with a specified recovery

time of ≤2 μs.

The output voltage is regulated by the Zener diode VR3. When

the output voltage exceeds the sum of the Zener and optocoupler

LED forward drop, current will flow in the optocoupler LED.

This will cause the transistor of the optocoupler to sink current.

When this current exceeds the ENABLE pin threshold current

the next switching cycle is inhibited. When the output voltage

falls below the feedback threshold, a conduction cycle is allowed

to occur and, by adjusting the number of enabled cycles, output

regulation is maintained. As the load reduces, the number of

enabled cycles decreases, lowering the effective switching

frequency and scaling switching losses with load. This provides

almost constant efficiency down to very light loads, ideal for

meeting energy efficiency requirements.

As the TinySwitch-LT devices are completely self-powered,

there is no requirement for an auxiliary or bias winding on the

transformer. However by adding a bias winding, the output

overvoltage protection feature can be configured, protecting

the load against open feedback loop faults.

When an overvoltage condition occurs, such that bias voltage

exceeds the sum of VR2 and the BYPASS/MULTIFUNCTION

(BP/M) pin voltage (28V+5.85V), current begins to flow into the

BP/M pin. When this current exceeds ISD the internal latching

shutdown circuit in TinySwitch-LT is activated. This condition

is reset when the BP/M pin voltage drops below 2.6 V after

removal of the AC input. In the example shown, on opening

the loop, the OVP trips at an output of 17 V.

A

08/07

7

Share Link: