RDK-128 Power Integrations, RDK-128 Datasheet - Page 8

• Manufacturer Part Number: RDK-128
• Description: KIT REF DESIGN 36-72W MOTOR DRVR
• Manufacturer: Power Integrations

Specifications of RDK-128

• Main Purpose: Power Management, Motor Control
• Embedded: No
• Utilized Ic / Part: PKS606
• Primary Attributes: Variable Speed 12V 36W DC Motor, 90 ~ 265 VAC
• Secondary Attributes: External Potentiometer or Variable DC Voltage Speed Control
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Other names: 596-1198

RDR-128 36 W, 72 W Peak Variable Output Power Supply
If the EN/UV pin has not been pulled low for 30 ms and the input voltage is below the
under-voltage threshold, then the loss of regulation is assumed to be due to a low line
condition, and the PeakSwitch will stop switching until the under-voltage threshold is
exceeded again.
4.4 Output Rectification and Filtering
Diode D9 rectifies the output voltage while capacitors C13 and C14 provide output
filtering. The output capacitor current ripple rating is chosen to be sufficient for the
maximum rated continuous/average load. Resistor R9 and capacitor C11 form a snubber
network across diode D9, which reduces high frequency ringing that occurs during the
diode turn off event.
4.5 Output Feedback
The PeakSwitch family of devices uses a simple on/off control scheme. When a current
greater than 240 µA is drawn from the EN/UV pin of U1, the subsequent switching cycle
is disabled.
optocoupler conducts enough current through R8, thus forward biasing D8 and turning on
transistor Q1.
phototransistor’s collector connected to the bypass pin of the PeakSwitch gives a
collector to emitter voltage (V
to source current more effectively while using the high gain, small signal transistor Q1 to
draw the current from the EN/UV pin. Optocoupler U2’s high CTR (300% – 600%)
ensures a fast control loop response. Diode D8 is placed close to Q1 and thus provides
thermal compensation against Q1’s V
The output voltage is variable to allow for speed control of the DC motor. An adjustable
shunt regulator, U3, has its cathode tied to its reference, making it behave as a voltage
reference at approximately 1.24 V above the 1.1 V optocoupler’s LED (U2A) drop.
When no external control voltage is applied at terminals J3, diode D10 remains reverse
biased and potentiometer R12 controls the voltage of the divider network formed by itself,
R13 and R10. Decreasing the value of R12 programs a new voltage set-point (and also
a new speed), and the feedback loop now regulates to a lower output voltage. Setting
potentiometer R12 to its minimum value regulates the output down to 2.35 V. An 11 V
zener diode (VR2) is in place to ensure the output voltage does not regulate too far
above 12 V, as may occur due to the large tolerances of most potentiometers (which may
be as high as ±20%).
The supply’s output voltage may also be controlled by an external DC control voltage
applied at J3, with amplitude between 0 V and 10 V. Applying an external voltage above
3.5 V at J3 will forward bias diode D10 and will set the reference and cathode pin of the
shunt regulator to the external control voltage. Applying a higher external control voltage
allows more current to flow through the LED of the optocoupler and thus reduces the
supply’s output voltage. If 10 V is applied at J3, the supply shuts down completely.
Reducing the external control voltage after a shut down will start the power supply again.
Power Integrations, Inc.
Tel: [phone] Fax: [phone]
www.powerint.com
The EN/UV pin is pulled low whenever phototransistor U2B of the
Transistor Q1 then pulls current out of the EN/UV pin.
CE
) of approximately 5.8 V, which allows the phototransistor
BE
drop.
Page 8 of 32
Having the
16-Aug-07