Design Idea DI-128 PeakSwitch 35 W (75 W Peak) Variable-speed DC Motor Drive Application Device Power Output Input Voltage Output Voltage Topology DC Motor Drive PKS606Y 35 W (75 W Pk) 90-265 VAC 12 V Flyback Design Highlights • • • • • • • supplied 3.6 V to 10 VDC voltage source (connected to J4). The motor speed controls vary the output voltage of the supply. 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 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. 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 motorʼs speed is variable by two methods: 1) potentiometer R20 (connected to J3), or 2) an externally 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 C10 1 nF 250 VAC R8 68 Ω 1/2 W C11 330 pF 1 kV 9,10 D8 MBR1060 7,8 1 C4 180 µF 400 V D1-D4 1N4007 C17 4700 pF 1 kV R15 2.2 Ω 1/8 W R3 150 Ω 1/2 W 2 D6 FR106 O C7 100 nF 400 V D PE EN/UV R7 4.7 kΩ R5 2.2 MΩ JP1 R6 2.4 MΩ U2B PC817X4 BP S C2,C1 100 pF 275 VAC PeakSwitch U1 PKS606Y F1 3.15 A GND C8 220 nF 50 V R12 4.99 kΩ 1% D7 1N4148 J3-2 +12 V JP3 C12 680 µF 25 V D12 1N4148 J2-1 MOTOR J2-2 4 VR2 1N5222B 2.5 V RTN R19 2 kΩ J4-1 C19 1 nF 250 VAC R13 1 kΩ + J4-2 U2A C21 PC817X4 1.0 µF 50 V Q3 2N3904 JP2 C15 100 nF 50 V 5 C6 47 µF 35 V R1 & R2 1.3 MΩ RT1 t 10 Ω C3 680 nF 275 VAC C20 680 µF 25 V 3 D5 1N4007 L1 5.3 mH 1A H VR1 P6KE200A 200 V C5 470 pF 1 kV R20 5 kΩ J3-1 PI-4519-110606 R18 20 Ω 1/8 W 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 dBµV 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. 60 70 AV dBµV 40 QP 30 AV 20 10 0 -10 -20 0.15 80 60 40 1.0 0 1 3 5 8 10 15 20 25 30 35 Output Power (W) Figure 2. Efficiency Across Extended Motor Load Range. 40 50 100.0 TRANSFORMER PARAMETERS Core Material PC40EE25-Z Bobbin EE25 Vertical 1/2 Primary: 19T, 2 × 31 AWG Bias: 5T, 2 × 29 AWG Winding Details Secondary: 4T, 4 × 23 AWG Shield: 7T, 4 × 23 AWG 1/2 Primary: 19T, 2 × 31 AWG Winding Order (pin numbers) 20 10.0 MHz Figure 3. Conducted EMI: 230 VAC in, IOUT = 4 A (48 W). PI-4523-110606 100 Efficiency (%) QP 50 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-4524-110206 80 Key Design Points • If the motor is stopped externally for more than 30 ms, U1ʼs 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. 1/2 Primary (1-3), Bias (4-5), Secondary (7,8-9, 10), Shield (1-NC), 1/2 Primary (3-2) Inductance 145 µH Leakage Inductance 5.4 µH Primary Resonant 3.4 MHz (minimum) Frequency Table 1. Transformer Design Parameters. For the latest updates, visit www.powerint.com 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. 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 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. ©Copyright 2006, Power Integrations, Inc. For a complete listing of worldwide sales offices, please visit www.powerint.com Rev. A 11/06