Pulse Coding Controlled Switching Converter with Generating Automatic Frequency Tracking Notch Characteristics for Radio Receiver

Transcription

1 Apr (Wen) Pulse Coding Controlled Switching Converter with Generating Automatic Frequency Tracking Notch Characteristics for Radio Receiver Yifei Sun, Yi Xiong, Yasunori Kobori, Haruo Kobayashi Gunma University Kobayashi Laboratory

2 OUTLINE 2/37 Introduction & Objective Conventional Switching Converters Pulse Coding Method in Switching Converter Automatic PWC Control Relationship with the Clock frequency and the Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal Automatic PWPC Control Conclusion and future work

3 OUTLINE 3/37 Introduction & Objective Conventional Switching Converters Pulse Coding Method in Switching Converter Automatic PWC Control Relationship with the Clock frequency and the Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal Automatic PWPC Control Conclusion and future work

4 Research Background 4/37 Switching converters Supply many kinds of voltage by switching power Power of switching converter has become large Switching noise has strongly spread in wide frequency range Important to reduce switching noise by decreasing main spectrum level EMI EMI:Electro-Magnetic Interference

5 Research Objective 5/37 Trouble Reduce clock noise by spread spectrum with shaking clock phase Noise of clock frequency is spread CK Radio Freq. Some electronic would not like to be affected at special frequency noise Research Objective Radio receiver [1] Spread spectrum with both EMI reduction and control the diffusion of noise [1]EMI: Electro-Magnetic Interference

6 Research Summary 6/37 Proposed method Spread spectrum method using pulse coding Design modulation circuit in order to generate notch frequency automatically Achievement 1Reduction of EMI generated from clock 2Noise removal at specific frequency 3Automatic generation of notch frequency

7 OUTLINE 7/37 Introduction & Objective Conventional Switching Converters Pulse Coding Method in Switching Converter Automatic PWC Control Relationship with the Clock frequency and the Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal Automatic PWPC Control Conclusion and future work

8 Conventional Switching Converter with Spread Spectrum Spread Spectrum Continuous modulation of periodic clock Reduction of EMI concentrating on fundamental frequency 8/37 V in PWM Generator Power Stage V out PFM/PPM Error AMP [2] V out Switching Power [2] PFM: Pulse Frequency Modulation PPM: Pulse Phase Modulation

9 Spread Spectrum for EMI Reduction 9/37 Spread spectrum using pseudo analog noise Reduce EMI noise Power Stage *Clock to SAW is modulated by shaking [3] phase using analog noise & PLL PWM Switching Pulse Comp. Vo SAW Saw-tooth Generator Analog Noise + - Vref Modulated Clock Original Clock Modulated Clock SAW V Random Pattern Generator LPF PLL Clock Gen. Buck converter with modulated clock PWM Timing Chart [3] PLL: Phase Locked Loop

10 Voltage[V] Voltage[V] Spread spectrum for EMI Reduction 10/37 1 Maximum noise 3.5V 10m Frequency [MHz] Maximum noise 2.0V 1MH 1 900kHz 2.0V z 40mV Frequency [MHz] 1 2 PWM signal spectrum with EMI reduction 10m 900kHz 10mV 1 2 PWM signal spectrum without EMI reduction Simulation conditions Input :12V Output :6V Clock frequency:200khz Without EMI reduction Noise is concentrated in basic and harmonic frequencies With EMI reduction Peak level of clock frequency is reduced a lot Noise is concentrated Bottom levels are increased Not good

11 OUTLINE 11/37 Introduction & Objective Conventional Switching Converters with Spread Spectrum Pulse Coding Method in Switching Converter Automatic PWC Control Relationship with the Clock frequency and the Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal Automatic PWPC Control Conclusion and future work

12 Diffuse Noise to Specific Frequency 12/37 Problem Noise diffusing uniformly (using analog modulation) Notch Using digital modulation Noise diffuses to specific frequency Frequency band where noise does not spread Notch band created in important frequency band EMI Reduction Control of diffused noise

13 Pulse Width Modulation in Switching Converter 13/37 SEL V H SW Pulse SEL Vo SAW V L PWM signal Comparator Coding Pulse Selector MUX + - Pulse-H Pulse-L Vref PWM W L D H >D o >D L W H Input High 1SEL: High 2MUX select V H 3Generate pulse with long width in comparator W L Input Low 1SEL: Low 2MUX select V L 3Generate pulse with short width in comparator D o = V o /V in manually set WL and WH

14 Voltage[V] Simulation Result with PWC Control 14/37 Condition Buck DC-DC converter V in :10V V out :5V L:200 μ H C:470 μ F I out :0.25A f ck :500kHz W L =0.2 μ s Design clock pulse to determine the notch frequency f n N = N 0.9V 1 W H W L 0.71MHz [N = 1,2,3,, n] 1 1.6μs 0.2μs = 0.71MHz 1.4MHz W H =1.6 μ s To=2.0 μ s Pulse widths of the coding pulses Frequency(MHz) PWM signal spectrum using PWC control

15 OUTLINE 15/37 Introduction & Objective Conventional Switching Converters with Spread Spectrum Pulse Coding Method in Switching Converter Automatic PWC Control Relationship with the Clock frequency and the Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal Automatic PWPC Control Conclusion and future work

16 Automatic PWC Control 16/37 Set frequency of radio reception Auto corresponding to Fin change is necessary SW Pulse SEL Vo + - Vref Notch frequency Automatic generate Pulse-H and Pulse-L Selector Pulse-H Pulse-L Control of diffused noise VH Radio receiver Fin Automatic PWC Controller SAW Generator VL SAW Generator Comp Comp

17 OUTLINE 17/37 Introduction & Objective Conventional Switching Converters with Spread Spectrum Pulse Coding Method in Switching Converter Automatic PWC Control Relationship between Clock frequency and Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal Automatic PWPC Control Conclusion and future work

18 Voltage[V] Relationship with Clock and Notch 18/37 F ck :500kHz 0.9V 0.71MHz 1.4MHz NF ck < F n < N + 1 F ck Optimal F n = (N + 0.5)F ck When N=1 Optimal Frequency(MHz) PWM signal spectrum using PWC control Better to generate Fn at middle of Fck F ck < F n < 2F ck F n = 1.5F ck F n 3 = F ck 2

19 Relationship between Pulse-H and Pusle-L 19/37 T ck V in Vo Original Clock Pulse L T o T p W L SW Pulse SEL Vo + - Vref Pulse H W H T p Fin Selector Automatic PWC Controller Pulse-H Pulse-L VH SAW Generator VL SAW Generator Comp Comp Timing Chart T o = D o T ck = V o V in T ck W L = T o T p W H = T o + T p T n = W H W L = 2 T p

20 OUTLINE 20/37 Introduction & Objective Conventional Switching Converters with Spread Spectrum Pulse Coding Method in Switching Converter Automatic PWC Control Relationship with the Clock frequency and the Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal Automatic PWPC Control Conclusion and future work

21 Generating Tck using Direct Calculation Generate Tck from Tin using: F in =(N+0.5) F ck 21/37 T ck =(N+0.5) T in N=1 D o =0.5 W L = T o T p =D o T ck T in SW Pulse SEL Vo + - Vref W H = T o + T p =D o T ck T in T n = 2 T p Selector Pulse-H Pulse-L Fin Counter T in Right shift 1bit ADD T in 2 T ck Right shift 1bit T ck 2 ADD SUB VH SAW Generator VL SAW Generator Comp Comp

22 V 22/37 Simulation Waveforms of W H, W L Generation We set F in = 750kHz Automatic generated F ck = 500kHz Tck=1.99μs Tin=1.33μs Tck compare with VL or VH Time/mSec1.01 s Simulation waveform of Tck and Tin Pulse-L 0.35μs w L T ck =(N + 0.5)T in = 1.5T in Theoretical formula W H = 1.66μs W L = 0.37μs Simulation result W H = 1.67μs W L = 0.35μs Well matched Pulse-H 1.67μs w H Time/mSecs Simulation waveform of W H and W L

23 OUTLINE 23/37 Introduction & Objective Conventional Switching Converters with Spread Spectrum Pulse Coding Method in Switching Converter Automatic PWC Control Relationship with the Clock frequency and the Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal Automatic PWPC Control Conclusion and future work

24 Voltage[V] 24/37 Simulated Noise Spectrum of PWM Signal Case 1 According to Case 1 : Fin=750kHz, N=1 Fck=500kHz, WH=1.66μs, WL=0.37μs Result:Fn=750 khz, Fck=500 khz, Fck < Fn < 2Fck Condition Buck DC-DC converter V in :10V V out :5V L:200 μ H C:470 μ F I out :0.25A F in = (N + 0.5)F ck 1m 1 100m Fn= 750kHz 4Fn= 3MHz Result Fn=750kHz 4 Fn=3.0MHz Frequency(MHz) Simulated spectrum with EMI reduction Assume to suppress influence on AM radio in 750kHz A notch was generated around 750kHz

25 Voltage[V] Simulated Noise Spectrum of PWM Signal Case 2 25/37 Case 2:Fin=1.25MHz,N=2 Fck=500kHz,WH=1.40μs,WL=0.60 μs Result:Fn=1.27 MHz, Fck=500 khz, 2Fck < Fn < 3Fck Simulation Result Fn=1.27 MHz 4Fn=5.05 MHz 1 100m Fn= 4Fn= *Compare bottom levels 4Fn is deeper than Fn 1m Condition:same Frequency(MHz) Simulated spectrum with EMI reduction

26 Voltage[V] Transient Response with F in Change in Case 2 26/37 Condition (N=2) F in = 1.25MHz F in = 1MHz F in =1.25MHz Settling Time 0μs F in = 750kHz Output stability Ripple: 2.37mV pp at F in = 1.25MHz 2.77mV pp at F in = 1MHz 5mV pp at F in = 750kHz Static ripple is about 0.1% of the output voltage V o stable Tin Vo 2.37mV 2.77mV 5mV Time/mSec s Transient response with Fin change Response speed is important when tuning or switching communication channels

27 Voltage[V] Simulated Noise Spectrum of PWM Signal Case 3 27/37 Case3 : Fin=1.75MHz, N=3 Fck=500kHz, WH=1.29μs,WL=0.72μs Result:Fn=1.8 MHz, Fck=500 khz, 3Fck < Fn < 4Fck Simulation Result 1 100m Fn=1.8MHz 4Fn=7.2MHz Fn=1.8 MHz 4Fn=7.2 MHz *Compare bottom levels Almost equal 1m Condition:same Frequency(MHz) Simulated spectrum with EMI reduction

28 Voltage[V] Voltage[V] Simulated Noise Spectrum of PWM Signal Case 3 28/37 *High frequency harmonics is not clear! *But it is good for AM radio receiver.(< 2MHz) It needs to generate Notch at higher than 80MHz (FM) 45Fn=78.75MHz 44Fn=77MHz 46Fn=80.5MHz 47Fn=82.25MHz 48Fn=84MHz Frequency(MHz) Frequency(MHz)

29 OUTLINE 29/37 Introduction & Objective Conventional Switching Converters with Spread Spectrum Pulse Coding Method in Switching Converter Automatic PWC Control Relationship with the Clock frequency and the Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal in the higher frequency range Automatic PWPC Control Conclusion and future work

30 PWPC Method 30/37 Complex coding method PWPC (Pulse width coding + Pulse phase coding) method PWC + PPC W L τ W H Theoretical formula f notch1 = f notch2 = n W H W L n 2 τ H τ L Expect T Condition: W H = 7μs W L = 3μs : PWC : PWPC Set f notch1 = f notch2 Big Notch

31 31/37 Automatic Generation of Notch Frequency with PWPC Control Automatic pulse generation Tck V L Pulse-L V L τ Pulse-LD τ Design timing in PWPC method W H = To + Tp = Do Tck + 0.5Tin W L = To Tp = Do Tck 0.5Tin τ = W H -W L /2 = 0.5 Tin Pulse coding of PWPC method

32 V 32/37 Simulation Waveforms of W H, W L Generation V We set F in = 750kHz Automatic generated F ck = 500kHz f notch1 = f notch2 n n = W H W L 2 τ H τ L τ H τ L = τ = W H W L 2 = T in 2 Tck=2μs Pulse-H WH 1.65μs τ = 0.7μs Pulse-L WL 0.35μs Time/mSecs Simulation waveform of Tck and delay Tck Theoretical formula result W H = 1.67μs W L = 0.33μs τ = 0.67μs Well matched Pulse-LD τ WL 0.35μs Time/mSecs Simulation waveform of Pulse-H, Pusle-L and delay Pulse-L Simulation result W H = 1.66μs W L = 0.37μs τ = 0.70μs

33 Simulated Noise Spectrum of PWPC Control Voltage[V] 33/37 According to Fin=750kHz, N=1 Fck=500kHz,WH=1.67μs,WL=0.33 μs Fn=750 khz, Fck=500 khz, Fck < Fn < 2Fck Condition Buck DC-DC converter V in :10V V out :5V L:200 μ H C:470 μ F I out :0.25A F in :750kHz F in = (N + 0.5)F ck 1 100m 1m 750kHz 4Fn=3.0MHz 8Fn=6.0MHz 12Fn=9.0MHz Frequency(MHz) Simulated spectrum with EMI reduction PWPC characteristic: There are many harmonics of 4NFn (N =1,2,3 )

34 OUTLINE 34/37 Introduction & Objective Conventional Switching Converters with Spread Spectrum Pulse Coding Method in Switching Converter Automatic PWC Control Relationship with the Clock frequency and the Notch frequency Direct generation of clock pulse from input frequency Simulated Noise Spectrum of PWM Signal in the higher frequency range Automatic PWPC Control Conclusion and future work

35 Conclusion 35/37 Developed pulse coding control in order to generate notch characteristics at desired frequency Analyze spread spectrum with notch characteristics Automatic generate the notch frequency from Fin Using F in = (N + 0.5)F ck, discussion on direct generation of notch in N=1,2,3 situation using PWC control Automatic generating of notch frequency with PWPC control

36 Future Work 36/37 Notch generation using PCC(Pulse Cycle Coding) method W W T L T H Extend 4Fn in order to high frequency notch generation using PWPC method

37 Thank you for Listening 37/37