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Design Idea DI-128
PeakSwitch
Application DC Motor Drive Device PKS606Y
35 W (75 W Peak) Variable-speed DC Motor Drive
Power Output 35 W (75 W Pk) Input Voltage 90-265 VAC Output Voltage 12 V Topology Flyback
Design Highlights
* * * * * * * Replaces a two-stage, linear power supply and chopper circuit with a simple, single-stage design Eliminates the chopper circuits normally used to achieve variable-speed control of DC motors Motor speed is controllable by a small potentiometer or a 3.6 V to 10 V variable DC voltage Low component count: only 47 parts Efficiency: 77% (at a load of 35 W) Meets EN55022 B conducted EMI limits ON/OFF control scheme is stable over the entire motor speed (output voltage) range
supplied 3.6 V to 10 VDC voltage source (connected to J4). The motor speed controls vary the output voltage of the supply. The controller in U1 receives feedback from the output and enables or disables the switching of its integrated MOSFET. Regulation is maintained by disabling or skipping MOSFET switching cycles. The output voltage is sensed across the series string of R12, Zener diode VR2 and the LED in U2 (in parallel with R13). As the output voltage rises above the VR2 conduction threshold, the current that flows through the U2 LED turns on transistor Q3. As Q3 pulls current out of the EN/UV pin of U1 switching cycles are skipped and less energy is transferred to the output. Once the output voltage falls, switching cycles are enabled again. A bias winding (T1, pins 4 and 5) on the transformer is rectified and filtered by D7 and C6, and supplies operating current to U1, through R7. A smart AC sense circuit-comprised of D5, C7, R5 and R6-enables the under-voltage lockout (UVLO) and latching shutdown functions of U1. The frequency jitter
R8 68 1/2 W 9,10 D8 MBR1060 J3-1 C15 100 nF 50 V C11 330 pF 1 kV
Operation
The flyback converter shown in Figure 1 uses a member of the PeakSwitch family (U1, a PKS606Y) to drive a 35 W motor, while delivering startup and load transition peaks of up to 75 W. The motors speed is variable by two methods: 1) potentiometer R20 (connected to J3), or 2) an externally
C10 1 nF 250 VAC
R20 5 k
1 D1-D4 1N4007 C4 180 F 400 V C17 4700 pF 1 kV R15 2.2 1/8 W C5 470 pF 1 kV R3 150 1/2 W VR1 P6KE200A 200 V
7,8
R12 4.99 k 1% JP3
D12 1N4148
J3-2
3
C20 680 F 25 V
+12 V J2-1
D6 FR106
2 5 C6 47 F 35 V
C12 680 F 25 V
MOTOR
J2-2
L1 5.3 mH 1A
D5 1N4007
4 VR2 1N5222B 2.5 V
R19 2 k
RTN
R1 & R2 1.3 M
RT1 t 10 C3 680 nF 275 VAC
O
C7 100 nF 400 V
D
PeakSwitch U1 PKS606Y
EN/UV BP
R7 4.7 k
R5 2.2 M R6 2.4 M U2B PC817X4 D7 1N4148 C19 1 nF 250 VAC R13 1 k
J4-1
+
JP1
J4-2 U2A C21 PC817X4 1.0 F 50 V
PI-4519-110606
S
GND
C2,C1 100 pF 275 VAC
F1 3.15 A
C8 220 nF 50 V
Q3 2N3904
JP2
R18 20 1/8 W
H
PE
L
CON3
Figure 1. Circuit Diagram of 35 W Continuous, 75 W Peak, Motor Drive Power Supply with Dual Speed Control Inputs.
DI-128 November 2006
DI-89 DI-128
function within U1, a shield winding in T1, and two small Y-capacitors (C10 and C19) across T1 reduce the generation of conducted EMI so that a single common mode choke (L1), a small X-capacitor (C3) and two small Y-capacitors (C1 and C2) at the input allow the supply to meet EN55022B limits with more than 12 dBV of margin. A combination RCD-Zener clamp (R3, C5, D6 and VR1) limits the peak drain-node voltage to below the 700 V rating of the integrated MOSFET. If JP3 is removed, an external variable resistor (R20) adjusts the voltage across R12 and therefore, the output voltage. The externally supplied motor speed regulating voltage (3.6 to 10 VDC) changes the voltage at the node of R12 and VR2, which effectively adjusts the output voltage. Diode D12 blocks reverse current flow through R19 if the external adjustment voltage is less than about 3.6 VDC. * If the motor is stopped externally for more than 30 ms, U1s latching shutdown function activates, and MOSFET switching latches off until AC input power is removed and reapplied. If latching shutdown is not needed, the function can be disabled and the parts count reduced by not installing D5, C7, R5 and R6.
PI-4524-110206
80 70 60 50 40
QP AV QP AV
dBV
30 20 10 0 -10 -20 0.15 1.0 10.0 100.0
Key Design Points
* The externally supplied voltage adjusts the motor speed as follows: 3.6 V sets the output voltage to about 12 V (the highest motor speed) and 7 V sets the output voltage to about 2 V (the lowest motor speed). If the resistive speed control circuit is to be used, jumper J3 must be removed from the PCB.
PI-4523-110606
*
MHz Figure 3. Conducted EMI: 230 VAC in, IOUT = 4 A (48 W).
100 80
TRANSFORMER PARAMETERS Core Material PC40EE25-Z Bobbin EE25 Vertical 1/2 Primary: 19T, 2 x 31 AWG Bias: 5T, 2 x 29 AWG Winding Details Secondary: 4T, 4 x 23 AWG Shield: 7T, 4 x 23 AWG 1/2 Primary: 19T, 2 x 31 AWG Winding Order (pin numbers) Inductance 1/2 Primary (1-3), Bias (4-5), Secondary (7,8-9, 10), Shield (1-NC), 1/2 Primary (3-2) 145 H 5.4 H
Efficiency (%)
60 40 20 0
1
3
5
8
10
15
20
25
30
35
40
50
Leakage Inductance
Output Power (W)
Figure 2. Efficiency Across Extended Motor Load Range.
For the latest updates, visit www.powerint.com
Primary Resonant 3.4 MHz (minimum) Frequency
Table 1. Transformer Design Parameters.
TIW = Triple Insulated Wire, NC = No Connect, FL = Flying Lead
Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power Integrations does not assume any liability arising from the use of any device or circuit described herein. POWER INTEGRATIONS MAKES NO WARRANTY HEREIN AND SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS. The products and applications illustrated herein (transformer construction and circuits external to the products) may be covered by one or more U.S. and foreign patents or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A complete list of Power Integrations' patents may be found at www.powerint.com. Power Integrations grants its customers a license under certain patent rights as set forth at http://www.powerint.com/ip.htm. The PI logo, TOPSwitch, TinySwitch, LinkSwitch, DPA-Switch, PeakSwitch, EcoSmart, Clampless, E-Shield, Filterfuse, StackFET, PI Expert and PI FACTS are trademarks of Power Integrations, Inc. Other trademarks are property of their respective companies. (c)Copyright 2006, Power Integrations, Inc.
Rev. A 11/06
Power Integrations 5245 Hellyer Avenue San Jose, CA 95138 Phone: 1-408-414-9200 Apps: 1-408-414-9660 Apps Fax: 1-408-414-9760 For a complete listing of worldwide sales offices, please visit www.powerint.com

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