Speed-control Techniques in AC-DC Operated BLDC Applications

Application ReportSLOA203 – August 2016 Speed-Control Techniques in AC-DC Operated BLDC Applications Naveen Bevara ..................................................................................................... BLDC Motor Drivers Sanjay Dixit ABSTRACT To achieve energy efficiency, ceiling fans and ventilation fans are moving from simple alternate-current (AC) induction motors to brushless direct-current (DC) motors (BLDC). An AC-operated BLDC motor requires two sections to run the BLDC motor: the AC-DC power conversion section and the DC to 3-phase AC conversion section. The Texas Instruments reference design, TIDA-00652, helps to meet these challenges of higher efficiency and power factor in a simpler way by using a single-stage power supply to convert the AC mains input into a low-voltage DC output. This reference design also combines a fully integrated and well protected single-chip, DRV10983, sensor-less sinusoidal brushless motor controller for low-noise operation. For the DRV10983 device, the motor can be controlled directly through PWM, analog, or I2C inputs. With the physical arrangement of ceiling fans, the speed control of an AC-operated BLDC motor can be possible with an infrared (IR) remote or any high-end wireless control. The speed can also be varied with a change in the supply voltage of the DRV10983 device, but with the variation of AC over universal range, the output of AC-DC is regulated to 24 VDC. Therefore the speed of the fan is controlled by providing a fixed DC or PWM signal at the SPEED pin of the DRV10983 device. The speed of the fan can also be controlled using the I2C input of theDRV10983 device, as demonstrated in the TIDA-00652 reference design. This application report presents two different ways to control the AC-operated BLDC ceiling fan with existing infrastructure. The first solution is to vary the speed by only toggling the AC mains switch. The second solution is to vary the speed using the TRIAC component similar to an existing AC-operated ceiling fan. Contents 1 Speed Control of BLDC motor by toggling the AC mains switch ..................................................... 3 1.1 Introduction .......................................................................................................... 3 1.2 Additional Circuit Using CD74HC4017 and SN74HCT14 ..................................................... 4 2 TRIAC Control of BLDC Motor ............................................................................................. 6 2.1 Optocoupler Circuit to Detect the Firing Angle .................................................................. 6 2.2 Additions to Input Filter for TRIAC Operation ................................................................... 8 3 References ................................................................................................................... 9 List of Figures 1 BLDC Ceiling Fan Demonstrated in TIDA-00652........................................................................ 3 2 Modified Block Diagram..................................................................................................... 3 3 Proposed Solution to Control the Speed of the Fan by Toggling AC ................................................. 5 4 Probable LED Arrangement to Indicate the Speed of Fan ............................................................. 6 5 TRIAC-Based Control of AC Operated BLDC Fan ...................................................................... 7 6 PWM Signal at Emitter of Optocoupler ................................................................................... 7 7 TRIAC Current and Input Rectified Voltage Without RC-Damped Circuit ............................................ 8 8 TRIAC Current and Input Rectified Voltage With RC-Damped Circuit ............................................... 8 All trademarks are the property of their respective owners. SLOA203 – August 2016 Speed-Control Techniques in AC-DC Operated BLDC Applications 1 Submit Documentation Feedback Copyright © 2016, Texas Instruments Incorporated ..... 8 2 Speed-Control Techniques in AC-DC Operated BLDC Applications SLOA203 – August 2016 Submit Documentation Feedback Copyright © 2016.............ti.......... www.. Texas Instruments Incorporated ....com 9 Input Resistor and RC-Damping Circuit Added to Input Filter ........................... the speed can be controlled by only toggling the AC mains switch. Figure 3 shows this modification of the proposed solution. In addition. Modified Block Diagram SLOA203 – August 2016 Speed-Control Techniques in AC-DC Operated BLDC Applications 3 Submit Documentation Feedback Copyright © 2016.ti. 85 VAC to High-PF AC-DC 24 V 265 VAC DC to 3-Phase Converter BLDC BLDC Motor (UCC28180) (DRV10983) SPEED IR Receiver and PWM Generator (MSP430G2231) Figure 1.com Speed Control of BLDC motor by toggling the AC mains switch 1 Speed Control of BLDC motor by toggling the AC mains switch 1. remote. and IR receiver. These devices can be replaced by a low-cost solution based on a ring counter (TI's CD74HC4017 device) and inverter (TI's SN74HCT14 device) which varies the speed by only toggling the AC mains and avoids the cost of a TRIAC component which are used in conventional ceiling fans.www. This solution can also be used along with the IR remote solution and can be used as additional control in case of the remote is lost. an arrangement of sequence LEDs can be implemented on the surface of the fan to indicate the speed of the fan. Texas Instruments Incorporated .1 Introduction Figure 1 shows a basic block diagram for an AC-operated BLDC ceiling fan demonstrated using the TIDA- 00652 reference design. BLDC Ceiling Fan Demonstrated in TIDA-00652 With the addition of a proposed circuit to the existing solution. using the proposed solution. 85 VAC to High-PF AC-DC 24 V 265 VAC DC to 3-Phase Converter BLDC BLDC Motor (UCC28180) (DRV10983) SPEED Additional Circuitry Using CD74HC4017 and SN74HCT14 Figure 2. The proposed solution can completely eliminate the option of a remote to reduce the cost of the microcontroller (MCU). 3 V in four different levels that can be fed to the SPEED pin of the DRV10983 device for different speeds of the fan. 4 Speed-Control Techniques in AC-DC Operated BLDC Applications SLOA203 – August 2016 Submit Documentation Feedback Copyright © 2016. Texas Instruments Incorporated . Q1. and Q3 turn on consecutively. A 5-V supply is then formed to CD74HC4017 and 74HCT4017 using a Zener diode of 5V1. the output of inverter is high. Q2. Therefore. the resistor divider network forms different voltages between 0 and 3.Speed Control of BLDC motor by toggling the AC mains switch www.2 Additional Circuit Using CD74HC4017 and SN74HCT14 Figure 3 shows the working of an additional circuit. And now. 24 V goes to zero making the input of Inverter to zero and. with each toggle of the AC mains Q0. If the AC is tuned off.ti. The high signal at the input of the inverter provides a high-to-low signal at the output which is fed to the clock of the counter resulting in a change of the output state. if the AC is turned on again.com 1. Whenever the AC is turned on. The number of steps of speed can be increased by increasing the use of the number of outputs and adjusting the resistor divider network accordingly. 24 V is formed at the output of the AC-DC section which is fed to the DRV10983 device. Q4 is connected to the master reset (MR) to revert back to initial step. 24 V is formed at the AC-DC section and gives a high signal at the input of the inverter. The 24 V is divided using a resistor divider and fed to the SN74HCT14 device to form 5 V at the input. because the 5-V supply is still present because of a high capacitor value. With each signal output. Texas Instruments Incorporated .7n R7 CD74HC4017 Q3 D6 2 1 3 20k R8 U2-A U3-A 1 1 2 1 2 0. Proposed Solution to Control the Speed of the Fan by Toggling AC SLOA203 – August 2016 Speed-Control Techniques in AC-DC Operated BLDC Applications 5 Submit Documentation Feedback Copyright © 2016.7k R10 R11 R9 4.com Speed Control of BLDC motor by toggling the AC mains switch 24V 24V FROM AC-DC OUTPUT 2 2 2 2 4.7k 4.www. Texas Instruments Incorporated Figure 3.7k R27 74HCT14 11 6 2 1 9 7 R24 10k 10 7 Q2 D11 4 3 R6 Q4 9 8 GND 8 D5 2 2 1 10k 1 2 1 10k R2 C1 4.2M R25 1 5V0 D12 Copyright © 2016.ti.7k 4.7k Q5 1 Q0 D4 24V 2 1 B U1-A 16 1 100k VCC 5 R26 22k Q4 15 2 2 1 D13 MR 1 1 2 2 1 5V0 14 3 E CP 0 2 13 4 R4 *CE 2 D3 2 R23 12 5 22k TC 6 4.47u C3 2 74HCT14 74HCT14 2.7k R12 200 0 Q0 2 1 1 1 1 R16 1 1 D8 D9 D7 200 200 1 2 A A A D10 Q1 2 1 Q1 2 1 LED LED LED A Q2 LED R15 R17 2 K K K 200 200 200 2 K Q2 2 1 Q2 2 1 2 1 2 R13 C R18 C R20 C C 200 3 200 Q2 200 Q3 200 3 Q4 390 Q3 2 1 B Q3 2 1 B 2 1 B 2 1 B R3 R14 Q1 R19 R21 R22 1 E E Q3 E Q3 E 3 3 D1 5V1 D2 5V Q1 1 RESISTOR DIVIDER NETWORK 2 5V0 47uF 47uF C2 39k 47k R1 A1 2 1 C 74HCT14 CD74HC4017_N_16 0 R5 4. R5 = ((20 kΩ / 1.67 kΩ (3) When Q3 is ON. The TIDA-00652 reference design (BLDC ceiling fan TI Design) is used to implement TRIAC-based fan control. Q1. the output of Q0. R6.3 V must be generated at the output of the network. the closest available resistor values were used In addition.4 V. When Q0 is ON. A small optocoupler-based circuit is connected to the TIDA-00652 BLDC board as shown in Figure 5. and when Q1 turns on. The rectified AC is sensed using the optocoupler. R5. two LEDs turn on.3) × 5 V) – 20k = 10 kΩ (4) In the schematic. The average of PWM is fed to the SPEED pin of the DRV10983 device.5 kΩ (2) When Q2 is ON. the variation of RMS AC source does not change the output DC. As the phase angle of TRIAC is varied. These LEDs can be kept on the surface of the ceiling fan which appears as a circle and variation of speed can be indicated with variation in size of circle accordingly. If 20 kΩ is used at the output.4) × 5 V) – 20k = 21. Speed 1 Speed 2 Speed 3 Speed 4 Figure 4. R4 = ((20 kΩ / 0. Texas Instruments Incorporated .6 V.TRIAC Control of BLDC Motor www.6) × 5 V) – 20k = 42. Example of LED arrangement that can be made on the surface of a BLDC fan to indicate the speed of the fan. Probable LED Arrangement to Indicate the Speed of Fan 2 TRIAC Control of BLDC Motor 2. R6 = ((20 kΩ / 2. and 3.8) × 5 V) – 20k = 105 kΩ (1) When Q1 is ON. 1.8 V. and R7 resistors must be used at the outputs of the ring counter.ti. 6 Speed-Control Techniques in AC-DC Operated BLDC Applications SLOA203 – August 2016 Submit Documentation Feedback Copyright © 2016. 0. a PWM signal is generated accordingly. Q2 and Q3 can be used to create an LED indication as shown in Figure 4. the R4.com To achieve four different steps of speed.1 Optocoupler Circuit to Detect the Firing Angle In a BLDC motor. 2. and so on. Whenever Q0 turns on. one LED turns on. R7 = ((20 kΩ / 3. www. Texas Instruments Incorporated .2uF 1 1 Copyright © 2016. The variation in the PWM signal from 10% to 90% results in analog voltage from 0. Voltage (V) Vmax V x 2x 3x .3 V correspondingly. Time (t) Voltage (V) V Time (t) Figure 6. PWM Signal at Emitter of Optocoupler SLOA203 – August 2016 Speed-Control Techniques in AC-DC Operated BLDC Applications 7 Submit Documentation Feedback Copyright © 2016.com TRIAC Control of BLDC Motor F1 FUSE-PCB R1 1 2 1 2 24V 2 47 K R2 1k D4 2 RLT1-1099 2 1 2. Texas Instruments Incorporated Figure 5.033uF 0. TRIAC-Based Control of AC Operated BLDC Fan The AC waveform chopped with a TRIAC at a certain firing angle generates a PWM signal corresponding to the firing angle as shown in Figure 6.ti. This PWM signal is averaged using the RC low-pass filer.8 V to 3.22uF IND-UPRIGHT IND-UPRIGHT Q1 5V1 C3 2 1uF 1 2 1 2 A ??? ??? 4 SPEED Pin of 1 R4 2 DRV10983 2 100k 2 470k 22k R5 R6 C4 2.22uF 5 C5 L1 L2 D3 0. The DRV10983 device can be used in Analog control mode and this output analog voltage can be connected to the SPEED pin of the DRV10983 device.2k 1 A2 A1 R3 AC Input R7 L3 1 2 1 (With Triac Controlled) 1 330k C1 C2 K2 K1 4 3 0. is required to limit the inrush current. Improvement in efficiency is achieved by incorporating an active MOSFET-based bypass circuitry at the cost of additional components. A single series resistor. Therefore the transient response of the EMI filter must be controlled by incorporating suitable damping circuits. The standard method is to use RC snubber as shown in Figure 9. The TRIAC-chopped AC looks similar to the waveform shown in Figure 7.com 2. TRIAC Current and Input Rectified Voltage With Figure 7. which leads to a non-zero input current. This value can either be iteratively derived using simulation software or empirically estimated based on experimental data. shown in Figure 9. The internal RC timer initiates a new firing sequence leading to repeated firing and misfiring of the TRIAC.22uF D3 A Copyright © 2016. As a result. The resistor also damps any high frequency oscillations caused by the internal TRIAC inductance or parasitic inductance and the EMI filter capacitance. Figure 8. R1. F1 FUSE-PCB R1 1 2 1 2 2 47 K R2 1k D4 2 1 RLT1-1099 1 A2 A1 L3 AC Input (With Triac Controlled) C5 K2 K1 4 3 0. ITH. Figure 9 shows the addition of the Ri and RC snubber in the input filter section with the previously mentioned considerations.TRIAC Control of BLDC Motor www. With addition of an R and C snubber. A small value selected for R2 will cause the pole to move away from the zero while a large value for R2 will lead to insufficient damping of complex filter poles. The value of R1 is generally in the range of 10 Ω to 100 Ω and is limited by the acceptable power loss and efficiency. Each time the input current falls below the holding current. Texas Instruments Incorporated . a small optimal range of resistance between 100 Ω and 2 kΩ exists. TRIAC Current and Input Rectified Voltage RC-Damped Circuit Without RC-Damped Circuit Rapid charging of the EMI filter capacitance during the firing sequence causes a large inrush current to flow through the TRIAC.2 Additions to Input Filter for TRIAC Operation The resonance of the undamped EMI filter causes the input current. iin(t) to oscillate in response to the step change in the input voltage caused by the TRIAC firing action. false triggering is eliminated and should result in the waveform shown in Figure 8.ti. Texas Instruments Incorporated Figure 9. Input Resistor and RC-Damping Circuit Added to Input Filter 8 Speed-Control Techniques in AC-DC Operated BLDC Applications SLOA203 – August 2016 Submit Documentation Feedback Copyright © 2016. the TRIAC commutates off. ” IEEE Energy Conversion Congress and Exposition. Texas Instruments Incorporated . • Montu Doshi. pp. Inc. Texas Instruments. Colorado. “Input filter design for TRIAC dimmable LED lamps. 30-W Brushless DC Motor Drive Reference Design (TIDUAS3) • CD74HC4017 High Speed CMOS Logic Decade Counter/Divider with 10 Decoded Outputs (SCHS200) • DRV10983 12. Power Electronics.B. Lighting Power Products. Three-Phase.ti. Second Edition.. K.to 265-V AC. Khanchandani. 2007. Tata McGraw-Hill Education. James Patterson .to 24-V. >0.D.94 PF Buck-PFC Plus 24-V. Longmont. Sensorless BLDC Motor Driver (SLVSCP6) • M.com References 3 References • 90. Sept.www. • SN74HCT14 Hex schmitt-trigger inverters (SCLS225) SLOA203 – August 2016 Speed-Control Techniques in AC-DC Operated BLDC Applications 9 Submit Documentation Feedback Copyright © 2016. Singh. 4631 – 4638. 91% Efficiency. 2013. limitations.com/clocks Industrial www.com Wireless Connectivity www. in accordance with the warranty in TI’s terms and conditions of sale of semiconductor products. TI is not responsible or liable for such altered documentation.ti. latest issue.ti. notwithstanding any applications-related information or support that may be provided by TI.com/video RFID www.ti. testing of all parameters of each component is not necessarily performed. IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections. Texas Instruments Incorporated . With such components. either express or implied. improvements and other changes to its semiconductor products and services per JESD46. Dallas.com/medical Logic logic.ti.ti. or other intellectual property right relating to any combination. machine. regulatory and safety-related requirements concerning its products.ti. monitor failures and their consequences. In some cases.ti. and that Buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use.com Space. Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in military/aerospace applications or environments. Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties. and any use of TI components in its applications.ti.com OMAP Applications Processors www.com/industrial Interface interface. enhancements. No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties have executed a special agreement specifically governing such use.com Communications and Telecom www. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.com/computers DLP® Products www.com/automotive Amplifiers amplifier. Buyers are responsible for their products and applications using TI components. and notices. TI components may be promoted specifically to facilitate safety-related applications.ti. Post Office Box 655303.ti.com/wirelessconnectivity Mailing Address: Texas Instruments. such components are subject to these terms. To minimize the risks associated with Buyers’ products and applications. Texas 75265 Copyright © 2016. or a license from TI under the patents or other intellectual property of TI.ti-rfid. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. TI assumes no liability for applications assistance or the design of Buyers’ products. Buyer acknowledges and agrees that any military or aerospace use of TI components which have not been so designated is solely at the Buyer's risk. and to discontinue any product or service per JESD48.ti.com Medical www. Nonetheless. lessen the likelihood of failures that might cause harm and take appropriate remedial actions.com/audio Automotive and Transportation www. TI does not warrant or represent that any license. Except where mandated by applicable law. Buyer acknowledges and agrees that it is solely responsible for compliance with all legal. Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.ti.com/energy Clocks and Timers www. mask work right.ti.ti. Information of third parties may be subject to additional restrictions. TI has specifically designated certain components as meeting ISO/TS16949 requirements. Buyers should provide adequate design and operating safeguards.ti. Use of such information may require a license from a third party under the patents or other intellectual property of the third party.com Security www. or process in which TI components or services are used. Avionics and Defense www. TI warrants performance of its components to the specifications applicable at the time of sale.ti. conditions.com Consumer Electronics www.dlp.com Computers and Peripherals www.ti.com Video and Imaging www.com/consumer-apps DSP dsp. Information published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof.com/space-avionics-defense Microcontrollers microcontroller. TI’s goal is to help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and requirements.com/security Power Mgmt power. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.com/omap TI E2E Community e2e.ti.com Energy and Lighting www. mainly for automotive use. TI will not be responsible for any failure to meet ISO/TS16949.ti.ti. TI is not responsible or liable for any such statements. In any case of use of non-designated products. latest issue. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failures. Products Applications Audio www.com/communications Data Converters dataconverter.ti. Buyer will fully indemnify TI and its representatives against any damages arising out of the use of any TI components in safety-critical applications. is granted under any patent right. copyright.ti.