Multi-Phase Clock-less Switching Converter with EMI Noise Reduction

Transcription

1 ICTSS2018 April 18-20,2018 Kiryu, Japan Wed, April 18, :00 14:30 Room A I03-09 Multi-Phase Clock-less Switching Converter with EMI Noise Reduction Yi Xiong*, Koyo Asaishi, Natsuko Miki, Yifei Sun Nobukazu Tsukiji, Yasunori Kobori, Haruo Kobayashi Gunma University

2 Research Objective 1 Objective Development of power supply with - Fast response - Large current Approach - Constant on-time control - Multi-phase

3 Contents 2 Research background Constant on-time control Four-phase converter solution via saw-tooth wave circuit Simulation result Transfer function characteristics EMI reduction via pulse phase modulation Conclusion

4 Contents 3 Research background Constant on-time control Four-phase converter solution via saw-tooth wave circuit Simulation result Transfer function characteristics EMI reduction via pulse phase modulation Conclusion

5 What is Power Supply 4 AC-DC Converter 100~240V AC Power Supply DC-DC Converter 4.2V DC Power supply is demanded everywhere to provide appropriate voltage for electronic device

6 Classifications of DC-DC Converter 5 Load DC-DC converter Basic configuration Buck Boost Buck-Boost Vin<Vo Vin>Vo Vin Vo

7 Operation of Buck Converter 6 Q L Vin PWM D C Vo V Q ΔI L+ Q Buck Converter V EO + L - I L I L ΔI L- Vin + V C Q - Vin On State: Q on D off D V EO - L + C + - I L + Vo - + Vo - V EO Ton On State Toff Ts VLon = Vin-Vo= L ( il+/ t on ) Off State VLoff =-Vo= L ( il-/ t off ) Volt-second Balance il+ = il- Off State: Q off D on Vo = Vin

8 Demand for Power Supply of Process 7 DC input DC output Max. output current Max. output current step Max. output current slew rate 12V 1.5V 120A 100A/us 930A/us Large current Ripple control High speed response Multi-phase Four-phase Ripple Control Converter

9 Contents 8 Research background Constant on-time control Four-phase converter solution via saw-tooth wave circuit Simulation result Transfer function characteristics EMI reduction via pulse phase modulation Conclusion

10 Merit of Constant on-time control 9 Ripple Control Comp Vref Ripple +Vref Vin Hysteresis window control PWM Vout -Vref PWM V Extreme fast response Constant on-time control out f s V 1 T s in T T on s f s No phase compensation Comp Ripple Vref Ton Vin PWM Vout V out V T in on Vref PWM Ton Ton Toff Frequency swings usually Constant Toff Frequency keeps stable

11 Operation of Constant on-time control 10 Proposed COT Converter Operation waveform I o I L Cr Voltage ripple V r SW V ref V comp R T on PWM No External Clock COT Controller State t t 0 t 1 t 2 0 ~t 1 1 V r reaches to V ref, V comp comes out 2 RS flip-flop is started by V comp, 3 PWM goes to HIGH, meanwhile Ton timer is started. 4 Ton timer is over 5 RS flip-flop is reset automatically 6 PWM goes to LOW. State t 1 ~t 2 7 PWM keeps LOW until next cycle

12 Contents 11 Research background Constant on-time control Four-phase converter solution via saw-tooth wave circuit Simulation result Transfer function characteristics EMI reduction via pulse phase modulation Conclusion

13 Demerit of Single-Phase Converter 12 Single-phase Converter Cr SW V o Lo I Lo I o Io flows only through inductor Lo COT Controller Lo will be large in size PMW 100A I Lo =I o Large load on Inductor Lo V o

14 Merit of Multi-Phase Converter 13 Multi-phase Converter PMW1 PMW2 I L1 Cr V o I o Tracking PWM2 with PWM1 is demanded without clock I L2 Inductor L1 and L2 will go shares with the Io PWM1 PWM phase difference L1 and L2 will be small in size IL1 IL2 50A 50A Load of each phase s inductor halved 100A ILo=IL1+IL2 Vo Simulative frequency multiplication Low ripple by shifted two-phase peak current

15 Proposed Four-Phase Converter Solution 14 10kΩ 1nF Cr 1mF Main Power Stage Vo 3V 10uH 3.9kΩ 10V 200uF PWM1 SAW Generator Tracking SAW 470kΩ Sub-Converter 1 Voltage Divider & Comparator Peak Hold Sub-Converter 2 Sub-Converter 3 Tracking PWM Peak Voltage Sub Power Stages Four-phase PWM Generator

16 SAW Generator & Peak Hold Generation of Four-Phase PWM Main PWM Operation waveform [V/V] 10 VPeak-hold SAW 2 Reset Voltage Divider & Comparator V p PUL4 PWM4 V p PUL3 PWM3 V p PUL2 PWM2

17 Contents 16 Research background Constant on-time control Four-phase converter solution via saw-tooth wave circuit Simulation result Transfer function characteristics EMI reduction via pulse phase modulation Conclusion

18 Current Balance 17 Current balance offset ΔI L (ΔI L = I L I o /n ) Io = 5.06A Good current balance I L1 = I L2 = I L3 = I L4 =1.26A ΔI L1 = I L1 - I o /4 = /4 =0.005A δ = 0.005/(5.06/4) 100% [I/A] = 0.39% Io 105A Large load current achieved I L1, I L2, I L3, I L [t/ms] Good current balance during transient response

19 Comparison 18 V out : 3V Static state characteristic Vout Ripple peak to peak 57%off 2.8mV 1.2mV Ripple range under1% I load : 5A 10A 5A Transient response Peak to Peak voltage Recovery time Dynamic load regulation Undershoot 70%off 831mV 246mV 75%off 104us 30us Overshoot 59%off 699mV 289mV 80%off 123us 27us

20 Contents 19 Research background Constant on-time control Four-phase converter solution via saw-tooth wave circuit Simulation result Transfer function characteristics EMI reduction via pulse phase modulation Conclusion

21 Transfer function characteristics 20 /db Gain /deg Phase LC resonance peak frequency F 1 =3.1kHz F 2 = 5.6kHz -40dB/dec Single-phase Single-phase Four-phase -20dB/dec 20 P 1 =40 P 2 = k 2k 4k 10k 20k 40k 100k 200k [Freq/Hz] Phase margin F 2 2F 1 Four-phase Single-phase Power Stage: One LC Resonance Peak Frequency: = Four-phase Power Stage: Four (Parallel Connection) LC Resonance Peak Frequency : = = =

22 Contents 21 Research background Constant on-time control Four-phase converter solution via saw-tooth wave circuit Simulation result Transfer function characteristics EMI reduction via pulse phase modulation Conclusion

23 Pulse Phase Modulation 22 Pulse width Constant Pulse phase Change D D D D D time Phase Modulated Pulse Pulse width Constant Modulation pulse Synchronized SAW signal to V comp Comparison between SAW & Triangle wave EMI Reduction Circuit Synchronized pulse signal to PWM

24 Spectrum Diffusion Effect of PWM1 23 Before EMI Reduction 10dB 18dB 16dB After EMI Reduction [Freq/MHz] The EMI reduction circuit only used in PWM1

25 Spectrum Diffusion Effect of other PWMs 24 PWM2 PWM3 PWM4 [Freq/MHz] Other three phase PWMs has the same spectrum diffusion effect

26 Conclusion 25 Proposal of four-phase DC-DC converter with constant-on-time control Good current balance, Large load current Low output voltage ripple, Fast response Four-phase converter shew better phase margin, higher operating frequency EMI reduction is achieved by pulse phase modulation, the four-phase PWMs

27 Thank you for your attention 26

28 Q&A 27 Q:Have you considered about the efficiency? A: As for a power supply the efficiency is an important performance, but the first purpose of this research is fast response and large load current. On the basis of these achievement,i will consider about the efficiency in the next step.