PKS606P View Datasheet(PDF) - Power Integrations, Inc

Part Name

Description

MFG CO.

PKS606P

PeakSwitch Family Enhanced, Energy-Efficient, Off-Line Switcher IC With Super Peak Power Performance

Power Integrations, Inc 

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off the power supply. This protects the load and supply from

a continuous fault condition. Removing the AC input resets

this condition.

The output voltage is determined by the Zener diode VR2, the

voltage drop across R12 and the forward drop of D9 and the LED

of optocoupler U2. Resistor R13 provides bias current through

D9 and VR2, to ensure that VR2 is operating close to its knee

voltage, while R12 sets the overall gain of the feedback loop.

Capacitor C15 boosts high frequency loop gain to help distribute

the enabled switching cycles and reduce pulse grouping.

When the output voltage exceeds the feedback threshold voltage,

current will flow in the optocoupler LED, causing current flow in

the transistor of the optocoupler. When this exceeds the ENABLE

pin threshold current the next switching cycle is inhibited,

as 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.

PeakSwitch device U1 is supplied from an auxillary winding

on the transformer which is rectified and filtered by D7 and C6.

Resistor R7 provides approximately 2 mA of supply current into

the BYPASS pin capacitor C8. During startup or fault conditions

when the bias voltage is low, the BYPASS pin is supplied from

a high voltage current source within U1, eliminating the need

for separate startup components.

Components Q1-2, R9-11, R14, C13, C16, and VR3 form

an overvoltage and overcurrent protection circuit. An output

overvoltage or overcurrent condition fires SCR Q2, clamping

the output voltage and forcing PeakSwitch U1 into latching

shutdown after 30 ms. The low pass filter formed by R10 and

C13 adds a delay to the over-current sense. The shutdown

condition can be reset by briefly removing AC power for ~3

seconds (maximum). The latching function within PeakSwitch

significantly reduces the size of the SCR and output rectifier,

D8, as the short circuit current only flows for 50 ms before the

supply latches off.

This design meets EN55022 Class B conducted EMI with

>10 dB margin even with the output RTN directly connected

to earth ground.

Key Application Considerations

PeakSwitch Design Considerations

Output Power Table

The data sheet maximum output power table (Table 1) represents

PKS603-607

the maximum practical continuous output power level that can

be obtained under the following assumed conditions:

1. The minimum DC input voltage is 100 V or higher for

85 VAC input, or 220 V or higher for 230 VAC input or

single 100/115 VAC with a voltage doubler.

2. Efficiency of 70% for Y/F packaged devices, 75% for P

packaged devices at 85-265 VAC, 75% for 230 VAC input

all packages

3. Minimum datasheet value of I2f

4. Transformer primary inductance tolerance of ±10%

5. Reflected output voltage (VOR) of 135 V

6. Voltage only output of 15 V with an ultra fast PN rectifier

diode

7. Continuous conduction mode operation with transient KP*

value of 0.25

8. Sufficient heatsinking is provided, either externally (Y/F

packages) or through an area of PC board copper (P package)

to keep the SOURCE pin or tab temperature at or below

110 °C.

9. Device ambient temperature of 50 °C for open frame designs

and 40 °C for sealed adapters

*Below a value of 1, KP is the ratio of ripple to peak primary

current. To prevent reduced power capability due to premature

termination of switching cycles, a transient KP limit of ≥0.25 is

recommended. This avoids the initial current limit (IINIT) being

exceeded at MOSFET turn on.

Peak vs. Continuous Power

PeakSwitch devices have current limit values that allow the

specified peak power values in the power table. With sufficient

heatsinking, these power levels could be provided continuously,

however this may not be practical in many applications.

PeakSwitch is optimized for use in applications that have short

duration, high peak power demand, but a significantly lower

continuous or average power. Typical ratios would be PPEAK ≥

2 × PAVE. The high switching frequency of PeakSwitch allows

a small core size to be selected to deliver the peak power,

but the short duration prevents the transformer winding from

overheating. As average power increases, it may be necessary

to select a larger transformer to allow increased copper area for

the windings based on the measured transformer temperature.

The power table provides some guidance between peak

power and continuous power in sealed adapters, however

specific applications may differ. For example, if the peak

power condition is very low duty cycle, say a 2 second peak

occurring only at power up to accelerate a hard disk drive,

then the transformer’s thermal rise is only a function of the

continuous power. However, if the peak power occurs every

200 ms for 50 ms then it would need to be considered.

In all cases, the acceptable temperature rise of the PeakSwitch

and transformer should be verified under worst case ambient

and load conditions.

9

Rev. I 02/07

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