Design Kit. NJM2377 Boost DC/DC Converter. All Rights Reserved Copyright (C) Bee Technologies Corporation

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Design Kit NJM2377 Boost DC/DC Converter All Rights

2 Contents Slide # 1. NJM2377 Boost DC/DC Converter Circuit PWM Boost DC/DC Converter Basic Operation and Design Boost DC/DC Converter V OUT Boost DC/DC Converter t ON /t OFF Boost DC/DC Converter Inductor Selection Boost DC/DC Converter Inductor Peak Current Boost DC/DC Converter C OUT Selection NJM2377 Application Circuit Configuration NJM2377 Soft Start Setting NJM2377 Oscillation Frequency Setting Error Amp Feed Back Loop Setting Performance Characteristics Output Start-Up Voltage and Current Output Ripple Voltage Efficiency Step-Load Response Voltage and Current Simulation Result Losses 6.1 Bipolar Junction Transistor Losses Schottky Barrier Diode Losses Waveforms 7.1 Start-Up Sequencing Waveforms Switching Waveform at Load 5mA Switching Waveform at Load 1mA... Simulations index... Simulations Settings All Rights Reserved Copyright (C) Bee Technologies Corporation 29 2

3 -IN REF FB CT GND CS OUT V+ 1. NJM2377 Boost DC/DC Converter Circuit 5V to 9V at 5mA Boost DC/DC Converter (f OSC =15kHz, V ripple =3mV p-p ) IN Rsf 16k CS Rsr 4.7uF 18k IC = L u R3.8 D1 HRU32A R2 15k OUT V+ 5V Cin 22uF Rt 24k Ct 47pF IC = Cout 22uF Rload 18 Rf 56k U1 NJM2377 Q1 Q2SD2623 ESR.13 R1 9.1k CLP 1pF U1: New Japan Radio NJM2377 Control IC Q1: Panasonic 2SD2623 NPN D1: Renesas HRU32A Schottky Barrier Diode All Rights Reserved Copyright (C) Bee Technologies Corporation 21 3

2. PWM Boost DC/DC Converter Basic Operation and Design V IN =5V IN 2.3), 2.

2) t ON t OFF PWM output pulse Q1 QN_SW Cout ESR R2 Rload 2.5) R1 2.

Error voltage is pulse width modulated with sawtooth waveform.

4 2. PWM Boost DC/DC Converter Basic Operation and Design V IN =5V IN 2.3), 2.4) L: I L L 1 2 D1 V OUT =9V OUT V+ PWM Control Circuit 2.2) t ON t OFF PWM output pulse Q1 QN_SW Cout ESR R2 Rload 2.5) R1 2.1) V OUT is monitored by R 1 and R 2 then compared to reference voltage V B in NJM2377. Error voltage is pulse width modulated with sawtooth waveform. PWM output pulse width is proportional to the error level. This signal will control the switch ON/OFF(t ON /t OFF ). Therefore V OUT, which is proportional to t ON /t OFF, is controlled to the desired voltage. All Rights Reserved Copyright (C) Bee Technologies Corporation 29 4

5 2.1 Boost DC/DC Converter V OUT V OUT is determined by R1 and R2, without considering I(IN-) of NJM2377 V OUT is calculated as below. V OUT R2 R1 15k 9.1k 1V REF V For V OUT =9V, R1=9.1kΩ, R2=15kΩ are selected. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 5

6 2.2 Boost DC/DC Converter t ON /t OFF If the circuit works in continuous conduction mode (CCM), output voltage (V OUT ) and ON/OFF time (t ON /t OFF ) follow the equation below. V OUT t ON t t OFF OFF V IN then t ON V V OUT OUT V f IN OSC From V IN =5V, V OUT =9V and f OSC =15kHz, these result as t ON /t OFF are t ON =2.96μs, t OFF =3.71μs, and duty=45%. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 6

7 2.3 Boost DC/DC Converter Inductor Selection L MIN value for the convertor to work in continuous conduction mode (CCM), is calculated as below. L MIN V V 2 IN 2 OUT I OUT t ON From V IN =5V, V OUT =9V, I OUT =5mA and t ON =2.96μs, these result as L MIN =82.2μH. L L 2 MIN LMIN A larger value will be used to increase the available output current, but limit it to around twice the L MIN value. L =15μH is selected. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 7

2.4 Boost DC/DC Converter Inductor Peak Current I L, PK is calculated as below. I L,PK VOUT I VIN 9.5 5 OUT VIN ton 2 L 5 2.

985m) And the current ripple - I L, PK is calculated as below ΔI L,PK VIN ton L 5 2.96μ 99mA 15μ 1mA 5mA I L, PK (86.821m,4.531m) A 86.

8 2.4 Boost DC/DC Converter Inductor Peak Current I L, PK is calculated as below. I L,PK VOUT I VIN OUT VIN ton 2 L μ 215μ 14mA PSpice is used to verify the circuit design. Add trace I(L) Zoom to check the peak value. 2mA 15mA (86.818m,14.985m) And the current ripple - I L, PK is calculated as below ΔI L,PK VIN ton L μ 99mA 15μ 1mA 5mA I L, PK (86.821m,4.531m) A 86.81ms ms ms ms I(L) I L, PK =14.985mA and I L,PK =14.985m-4.531m=1.454mA All Rights Reserved Copyright (C) Bee Technologies Corporation 21 8

9 2.5 Boost DC/DC Converter C OUT Selection C OUT is determined from the V ripple Spec (3mV p-p ). If C OUT >> I OUT ton/v ripple (5m2.96μ/3m=4.933μF), V ripple will mainly caused by ESR. Vripple ( p p) ESR IL 3m 13m 99m Select the capacitor that can handle the ripple current I rms. I rms IL m 2 3 ton t 2.96μ 6.67μ 13mArms C OUT =22μF, ESR=13m is selected. PSpice is used to verify the circuit design. I L,PK =11.168mA, ton=3μs. V ripple =14.8mV p-p I rms* =53.856mArms. 2mA 1mA A 9.9V 9.8V 9.7V I rms I(L) SEL>> 9.6V ms (87.553m,4.396m) rms(i(cout)) (87.556m,9.792) (87.553m,9.644) (87.556m, m) I L, PK V ripple Irms is larger than calculated value due to feedback loop response ripple current ms All Rights Reserved Copyright (C) Bee Technologies Corporation 21 9

10 -IN REF FB CT GND CS OUT V+ 3. NJM2377 Application Circuit Configuration 5V to 9V at 5mA Boost DC/DC Converter (f OSC =15kHz) V+ 5V IN Cin 22uF 3.1) 3.2) Rsf 16k Rt 24k Ct 47pF IC = CS Rsr 4.7uF 18k IC = L u R3.8 D1 HRU32A Cout 22uF R2 15k OUT Rload ) Rf 56k U1 NJM2377 Q1 Q2SD2623 ESR.13 R1 9.1k CLP 1pF U1: New Japan Radio NJM2377 Control IC Q1: Panasonic 2SD2623 NPN D1: Renesas HRU32A Schottky Barrier Diode All Rights Reserved Copyright (C) Bee Technologies Corporation 21 1

11 3.1 NJM2377 Soft Start Setting NJM2377 soft-start time is determined by Rsr, CS and Rsf First, caculate Rsr by Rsr>V THLA (max.)/i CHG (min.) (1.8V/1μA=18k) During steady state operation, I(CS)=I BCS =25ns. Maximum duty cycle is determined by V(CS). Set V(CS)=V THCS(max.) =.8V, Rsf is calculated by V THCS (max.) Rsr Rsr Rsf 18k.8 18k Rsf Rsf 16kΩ 1.5 V REF Soft-start time or t duty(max.) is time needed for V(CS) to reach V THCS(max.) by charging capacitor Cs. CS is charged by current Ics, calculated by: I CS then t VREF Rsr Rsf k 16k duty (max.) 4.41uA VTHCS (max.) Cs ICS ICHG.8 4.7μ 19ms 4.41μ 3μ All Rights Reserved Copyright (C) Bee Technologies Corporation 21 11

12 -IN REF FB CT GND CS OUT V+ 3.1 NJM2377 Soft Start Setting (Simulation) NJM2377 soft-start time is determined by Rsr, Rsf and CS Select Rsr, Rsf, and CS then check t duty(max.) by simulation. IN PARAMETERS: CS = 4.7u t duty(max.) =19.17ms. for CS=4.7uF 1.5V Rsf 16k CS Rsr {CS} 18k IC = V+ 5V Cin 22uF Rt 1MEG REF Ct 1nF IC = CS U1 NJM V.5V ( m,8.m) (19.17m,8.m) (76.653m,8.m) Rf 56k CLP 1pF.TRAN 5ms R1 1MEG V s 25ms 5ms V(CS) t duty(max.) =76.653ms for CS=3.3uF and t duty(max.) = ms for CS=6.8uF. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 12

-IN REF FB CT GND CS OUT V+ 3.2 NJM2377 Oscillation Frequency Setting NJM2377 oscillation frequency f OSC is determined by C T and R T IN Rsf 16k CS Rsr 4.

13 -IN REF FB CT GND CS OUT V+ 3.2 NJM2377 Oscillation Frequency Setting NJM2377 oscillation frequency f OSC is determined by C T and R T IN Rsf 16k CS Rsr 4.7uF 18k IC = f osc =15kHz V+ 5V Cin 22uF Rt 24k Ct V47pF IC = U1 NJM2377 R T =24k Rf 56k CLP 1pF R1 1MEG CT = 47pF and RT = 24kΩ to set an oscillation frequency to be 15kHz. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 13

14 3.3 Error Amp Feed Back Loop Setting Error Amp Feed Back Loop is determined by R1, R2, Rf and CLP For F.B loop gain G > 1, Rf is calculated as: Rf G R1// R2 1,k k//9.1k Rf 1k Simulation result shows V ripple of the circuit with RF=1k compare to the circuit with RF=56k. 9.12V 9.1V 9.8V RF=1k, CLP=1pF CLP is suggested to use value between 1pF~1,pF 9.6V RF=56k, CLP=1pF Inappropriate F.B loop design can cause an oscillation. PSpice is used to verify the ripple voltage vs. Rf and CLP values. 9.4V 79.ms 79.25ms 79.5ms 79.75ms 8.ms Changing RF to be 56k can reduce V ripple from 34mV p-p to less than 2mV p-p. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 14

15 -IN REF FB CT GND CS OUT V+ 4. Performance Characteristics IN Rsf 16k CS Rsr 4.7uF 18k IC = L u R3.8 D1 HRU32A R2 15k OUT V+ 5V Cin 22uF Rt 24k Ct 47pF IC = Cout 22uF Rload 18 Rf 56k U1 NJM2377 Q1 Q2SD2623 ESR.13 R1 9.1k CLP 1pF V IN =5V V OUT =9V I OUT =5mA V ripple(p-p) = less than 3mV Efficiency= 75% at I OUT =5mA U1: New Japan Radio NJM2377 Control IC Q1: Panasonic 2SD2623 NPN D1: Renesas HRU32A Schottky Barrier Diode All Rights Reserved Copyright (C) Bee Technologies Corporation 21 15

16 4.1 Output Start-Up Voltage and Current I(Rload) 5mA 4mA 3mA SEL>> 2mA 1V 9V 8V 7V I(Rload) 6V 5V 4V s 2ms 4ms 6ms 8ms 9ms Simulation result shows output start-up time of the circuit. This circuit needs 55ms to reach steady state. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 16

17 4.2 Output Ripple Voltage [ZOOM] 9.8V 9.75V 9.7V 18mV P-P 9.65V 9.6V 89.9ms 89.91ms 89.92ms 89.93ms 89.94ms 89.95ms 89.96ms 89.97ms 89.98ms 89.99ms 9.1V 9.9V 9.8V 9.7V 25mV P-P 9.6V SEL>> 9.5V 6ms 65ms 7ms 75ms 8ms 85ms 9ms Simulation result shows output ripple voltage caused by switching(18mv P-P ) and F.B loop oscillation(25mv P-P ). All Rights Reserved Copyright (C) Bee Technologies Corporation 21 17

18 4.3 Efficiency 1 Efficiency (9.m,75.5) ms 75ms 8ms 85ms 9ms 1*W(Rload)/rms(-W(V+)) Efficiency of the converter at load I OUT =5mA is 75.5%. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 18

19 4.4 Step-Load Response I(Load) 5mA 4mA 3mA 2mA SEL>> A I(I1) I(L) 2mA 1mA A 9.125V I(L) 9.1V 9.75V 9.5V 6ms 65ms 7ms 75ms 8ms 85ms 9ms Simulation result shows the transient response of the circuit, when load currents are 5mA to 1mA to 5mA steps. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 19

20 5. Voltage and Current Simulation Result I(L) peak, rms 2mA A I(L) = mA(peak), mA(rms) V(Q1:C), I(Q1:C) 1 1 V(D1:K,D1:A), IF(D1) 1 V(Cout), I(Cout) rms 2V 15V 1V 5V V 2V 1V V 1V 5V V 2 5mA 25mA >> 1 V(Q1:c) 2 I(Q1:c) 3mA 2 2mA 1mA >> 1 V(D1:2)- V(D1:1) 2 I(D1) avg(i(d1)) 1mA 2 5mA I(L) rms(i(l)) 1% of Rated Value 1% of Rated Value Q1 2SD2623: VCEO=2V, IC MAX =.5A D1 HRU32A: V RRM =2V, I O =.3A(avg), I FSM =3A I(Cout) = 5.255mA(rms) SEL>> A s 2ms 4ms 6ms 8ms 9ms 1 V(Cout:1) 2 rms(i(cout)) Simulation result shows voltage and current of the devices. Select L and Cout that can handle their I rms value. The absolute maximum value of Q1 and D1 are compared to simulation result for stress analysis. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 2

21 6.1 Bipolar Junction Transistor Losses 1 6mW 2 15mW 1% of Rated Value (P C, max. =15mW) P(Q1) peak, avg 4mW 1mW turn-on loss turn-off loss 2mW SEL>> W 2V 1 2 5mW W 3mA Conduction loss 1 V(Q1:c)*I(Q1:c) 2 avg(w(q1)) P C, avg. =17.254mW V(Q1:C), I(Q1:C) 15V 1V 5V >> V 2mA 1mA A ms ms ms 89.97ms ms ms 1 V(Q1:c) 2 I(Q1:c) Simulation result shows waveforms of I C and V CE of transistor Q1.Loss in peak and average values are also shown. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 21

W(D1) avg(w(d1)) Reverse recovery characteristic -5V -1mA -1V SEL>> -2mA 89.964ms 89.965ms 89.966ms 89.967ms 89.968ms 89.969ms 89.97ms 89.

22 6.2 Schottky Barrier Diode Losses 1mW P D, avg. =18.45mW P(D1) peak, avg 5mW W Reverse recovery loss Conduction loss -5mW Reverse leakage loss 1V 1 2 5V V(D1:A,D1:K) V, I(D1-1mW 2mA 1mA A W(D1) avg(w(d1)) Reverse recovery characteristic -5V -1mA -1V SEL>> -2mA ms ms ms ms ms ms 89.97ms ms ms ms 1 V(D1:1,D1:2) 2 I(D1) Simulation result shows waveforms of I F and V AK of diode D1.Loss in peak and average values are also shown. All Rights Reserved Copyright (C) Bee Technologies Corporation 21 22

23 7.1 Start-Up Sequencing Waveforms V(FB) 2.5V 2.V 1.5V V OSC : V(CT) V RAMP : V(CS) 1.V.5V SEL>> V V(U1:CT) V(U1:CS) V(U1:FB) 9.V 8.V 7.V 6.V 5.V s 1ms 2ms 3ms 4ms 5ms 6ms 7ms 8ms 9ms Simulation result shows start-up sequencing waveforms, including and control signal (V RAMP, V OSC, and V FB ). All Rights Reserved Copyright (C) Bee Technologies Corporation 21 23

24 7.2 Switching Waveforms at Load 5 ma (RL=18) I(L) V C (Q1) 1 I C (Q1) I(D1) 1.V 7.5V 5.V 2.5V V 2 2mA 15mA 1mA 5mA A 2mA 15mA 1mA I(L) >> A 1 V(Q1:c) 2 I(Q1:c) 15mA 1mA 5mA A -5mA I(D1) 9.1V 9.75V SEL>> 9.5V ms 89.95ms 89.96ms 89.97ms 89.98ms Simulation result shows boost converter switching waveforms at load 5mA, including I L, V C (Q1), I C (Q1), I(D1) and All Rights Reserved Copyright (C) Bee Technologies Corporation 21 24

25 7.3 Switching Waveforms at Load 1 ma (RL=9) I(L) V C (Q1) 1 I C (Q1) I(D1) 12V 8V 4V >> -4V 2 75mA 5mA 25mA A -25mA 75mA 5mA 25mA A -25mA 75mA 5mA 25mA SEL>> -25mA 9.125V 9.1V I(L) 1 V(Q1:c) 2 I(Q1:c) I(D1) 9.75V ms ms 89.96ms ms ms ms Simulation result shows boost converter switching waveforms at load 1mA, including I L, V C (Q1), I C (Q1), I(D1) and All Rights Reserved Copyright (C) Bee Technologies Corporation 21 25

26 Simulation Index Simulations Page Folder name 1. NJM2377 Soft Start Setting (Simulation) NJM2377 Oscillation Frequency Setting Error Amp Feed Back Loop (Transient) Start-Up Transient Simulation (~9ms.) Efficiency and Losses Step-Load Response Voltage and Current Simulation Switching Waveforms , 17, 23 18, 21, , 9, 24, 25 \IC-Config\SS \IC-Config\OSC \IC-Config\FB Transient Efficiency Step-load Stress Waveforms All Rights Reserved Copyright (C) Bee Technologies Corporation 29 26

27 SIMULATION SETTINGS 1 These settings are for: Start-Up Transient Simulation (~9ms.) Voltage and Current Simulation Step-Load Response.TRAN 9ms.1ms 15n.OPTIONS ABSTOL= 1.n.OPTIONS RELTOL=.1.OPTIONS VNTOL= 1.u All Rights Reserved Copyright (C) Bee Technologies Corporation 21 27

28 SIMULATION SETTINGS 2 These settings are for: Efficiency and Losses Switching Waveforms.TRAN 9ms 7ms 1n.OPTIONS ABSTOL= 1.n.OPTIONS RELTOL=.1.OPTIONS VNTOL= 1.u All Rights Reserved Copyright (C) Bee Technologies Corporation 21 28

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