1. APPED-101054A Confidential Application information Power Supply Unit (PSU) ©2010. Renesas Electronics Corporation, All rights reserved. Part 1…Efficiency and power factor Sep. 2011Rev.1.0 General Purpose Systems Marketing Dept. General Purpose Systems Division Marketing Unit Renesas Electronics Corporation

2. APPED-101054A Confidential Course Introduction Purpose This course is intended to expand your knowledge of power supply units to help you educate customers about Renesas products. Included in this is product information on Renesas ICs and discrete devices for power supply units. Objectives Learn about the structure of PSUs Learn about types of PFC ICs and isolated DC/DC converter ICs, their functions and line-up Learn about discrete devices used in PSUs Contents This course consists of five parts – Part 1…Efficiency and power factor – Part 2…Standards or regulations for PSUs – Part 3…PFCs (types, modes, how they work, roadmap, etc.) – Part 4…Isolated DC/DC (types, how they work, etc.) – Part 5…Discrete devices (lineup, roadmap, etc) Each part has its own introduction --- please refer to each introduction for further information 2 ©2010. Renesas Electronics Corporation, All rights reserved.

3. APPED-101054A Confidential Introduction to Part1 Purpose Part1 provides basic knowledge of power supply units Objectives Learn about efficiency and power factor Learn about the structure of the PSUs Learn about the role of each block in the PSUs Contents 38 pages Learning Time 30 minutes 3 ©2010. Renesas Electronics Corporation, All rights reserved.

4. APPED-101054A Confidential AC voltage---voltage applied to the set (i.e. voltage from a wall outlet) AC current---electrical current flow into the set AC voltage and frequency differ by country or area To simplify explanation, they are assumed to be the following in these materials unless otherwise specified. AC voltage: 100 V AC frequency: 50 Hz Definition of terms (valid in this course’s texts only) 4 ©2010. Renesas Electronics Corporation, All rights reserved.

5. APPED-101054A Efficiency 5 ©2010. Renesas Electronics Corporation, All rights reserved.

6. APPED-101054A Confidential Efficiency  Some power is lost at PSU! ---That’s bad but unavoidable Efficiency (η) = Input power Output power Input power Input power - loss at PSU η: Eta (Greek letter), used for expressing efficiency of PSU = 6 ©2010. Renesas Electronics Corporation, All rights reserved.

7. APPED-101054A Power Factor 7 ©2010. Renesas Electronics Corporation, All rights reserved.

8. APPED-101054A Confidential Remember this from your university classes? Power factor (PF) = real power / apparent power (a decimal number between 0 and 1) Generally, there is no symbol for power factor, but it is often abbreviated as “PF” in tables and figures. Real power (P): actual power consumed at load (unit: watt (W)) Electrical charge is calculated based on this value Reactive power (Q): unconsumed power coming and going between (unit: var) wall outlet and load Apparent power (S): the product of the effective values of (unit: volt-ampere (VA)) voltage and current It's all Greek to me --- William Shakespear “Julius Caesar” 8 ©2010. Renesas Electronics Corporation, All rights reserved.

9. APPED-101054A Confidential Well, let’s look at some examples Current is proportional to voltage in these devices ->Power factor = 1 AC voltage (AC 100 V) +100 V -100 V AC current (AC 0.5 A) +0.5 A -0.5 A proportional 9 ©2010. Renesas Electronics Corporation, All rights reserved.

10. APPED-101054A Confidential Dimmer for electric light bulb AC current controlled by dimmer 10 ©2010. Renesas Electronics Corporation, All rights reserved.

11. APPED-101054A Confidential For the dimmer… AC current AC voltage Power is consumed only during the period colored yellow (i.e. power is fed to bulb), because Power = Voltage × Current AC current AC voltage 11 ©2010. Renesas Electronics Corporation, All rights reserved.

12. APPED-101054A Confidential The meaning of PFC is … PF is 0.6 AC current AC voltage Power Factor (PF) is the index which shows how the waveforms of AC voltage and AC current overlap each other (refer to supplement-1 for the strict definition of PF). A dimmer changes the brightness of a light bulb by changing the PF. 12 ©2010. Renesas Electronics Corporation, All rights reserved.

13. APPED-101054A Confidential Harmonic current Harmonic current is an integer multiple of the fundamental frequency (e.g. 50 Hz in Tokyo) 100 Hz (2 nd harmonic), 150 Hz (3 rd harmonic), 200 Hz (4 th harmonic)… PF < 1= distorted wave = contains much harmonics (noisy) AC current 13 ©2010. Renesas Electronics Corporation, All rights reserved.

14. APPED-101054A Confidential Peak height of the AC current wave does not change in a dimmer Though the brightness is different, …. How about other equipments? 14 ©2010. Renesas Electronics Corporation, All rights reserved.

15. APPED-101054A Confidential In electronic equipment --- the peak height changes The smoothing circuit cannot take in the current continuously (refer to “Supplement 3”) This noise goes back to the AC outlet and is fed to other equipment, and may have a negative effect on that equipment. If the PF were 1, such a small current would be enough for the equipment 15 ©2010. Renesas Electronics Corporation, All rights reserved.

16. APPED-101054A Confidential If PF is low …… Electric power companies have to generate more electricity corresponding to the peak of the current. -> need more fuel …not environmentally friendly “TV doesn’t work while the microwave oven is operating. Help!” …from users “Hi-Fi set hums when the air conditioner is turned on. Uncomfortable” …from users Let’s correct the power factor -> PFC ICs are needed 16 ©2010. Renesas Electronics Corporation, All rights reserved.

17. APPED-101054A Structure of the PSUs 17 ©2010. Renesas Electronics Corporation, All rights reserved.

18. APPED-101054A Confidential The simplest: primary side of PSUs (1) Transformer changes AC voltage (eg. AC 100 V -> AC 12 V), and electrically isolates the secondary side from the primary side. Diode bridge rectifies AC voltage (eg. AC 12 V). The smoothing capacitor smoothes the output voltage from the diode bridge. 18 ©2010. Renesas Electronics Corporation, All rights reserved.

19. APPED-101054A Confidential Why are transformers needed? If any of the parts on the red path in the figure are out of order, AC 100 V may appear on the secondary side We are obligated by law to isolate all exposed conductive surfaces from the AC line to avoid the risk of electrical shock (e.g. PSE law, etc.) ->So, transformers are needed! 19 ©2010. Renesas Electronics Corporation, All rights reserved.

20. APPED-101054A Confidential The simplest primary side of PSUs (2) The disadvantage of this type of PSU is that it is HEAVY and LARGE!! Let’s apply higher frequency (>50Hz) to the transformer 20 ©2010. Renesas Electronics Corporation, All rights reserved.

21. APPED-101054A Confidential Switching mode power supply: SMPS Small and light PSUs (1) DC 100 V is converted to 100-300 kHz pulses by MOSFET and Isolated DC/DC IC, then it’s fed to a transformer This enables the use of a smaller transformer -> Small, light, GOOD!! 21 ©2010. Renesas Electronics Corporation, All rights reserved.

22. APPED-101054A Confidential The main issue for this type of SMPS is the generation of harmonic current as shown before. (refer to Supplement 3) The harmonic current goes back to the AC outlet → What should we do???!!! 22 ©2010. Renesas Electronics Corporation, All rights reserved. Switching mode power supply: SMPS Small and light PSUs (2)

23. APPED-101054A Confidential Better SMPS: --- Isolated DC/DC + PFC PFC IC filters out the harmonic and prevents the harmonic current from going back to the AC outlet → GREAT! WONDERFUL! SPLENDID! This is the solution to satisfy harmonic regulations and EnergyStar 23 ©2010. Renesas Electronics Corporation, All rights reserved.

24. APPED-101054A Confidential Summary 24 ©2010. Renesas Electronics Corporation, All rights reserved. PFC Corrects the power factor (reduces the harmonic current back to AC outlet) Isolated DC/DC drive the transformer with a few hundred kHz pulse There are COMBO ICs which have both PFC function and isolated DC/DC function on one chip Besides these, there is an auxiliary regulator on the primary side that supplies power to the PFC IC and isolated DC/DC IC Auxiliary regulator Small power regulator which supplies regulated voltage to PFC IC, isolated DC/DC IC, receiver for remote controller, etc.. Aux. regulators have their own regulator on-chip

25. APPED-101054A Confidential Various PSU structures 25 ©2010. Renesas Electronics Corporation, All rights reserved.

26. APPED-101054A Supplement 1Definition of power factor 26 ©2010. Renesas Electronics Corporation, All rights reserved.

27. APPED-101054A Confidential Definition of power factor & various powers Power factor (PF)Ratio of real power and apparent power. (no unit) A decimal number between 0 and 1 power factor = real power / apparent power Real power Actual consumed power at load. (unit: W) Power consumed at electric bulbs and heaters (Nichrome) is almost all real power. Subject of electricity charges. Apparent power The product of applied voltage (RMS) to the (unit: VA) load and current (RMS) apparent power = voltage (RMS) × current (RMS) Reactive powerPower not consumed at load, and coming (unit: var)and going between AC outlet and the equipment (see “AC current 2” on next page) Relationship between these powers RMS: Root Mean Squared – See Supplement 2 (real power) 2 + (reactive power) 2 apparent power = 27 ©2010. Renesas Electronics Corporation, All rights reserved.

28. APPED-101054A Confidential Example of real power and apparent power 28 ©2010. Renesas Electronics Corporation, All rights reserved.

29. APPED-101054A Supplement 2What is RMS? 29 ©2010. Renesas Electronics Corporation, All rights reserved.

30. APPED-101054A Confidential RMS value is calculated by taking the square of the voltage, getting its average (mean), and then its square root AC 100 V is Amplitude: 141 V (√2 times RMS) RMS ： 100 V Average ： 90 V (about 90% of RMS) [Note:] Average of AC voltage (or current) is defined as average of a half cycle Average of AC 100 V (RMS) is about 90 V 0 500 10,000 15,000 20,000 1/4 cycle1/2 cycle3/4 cycle1 cycle 141 -141 AC 100 V Square of AC 100 V RMS: Root Mean Square 30 ©2010. Renesas Electronics Corporation, All rights reserved.

31. APPED-101054A Supplement 3Noise generated from PSUs ---Harmonic current noise 31 ©2010. Renesas Electronics Corporation, All rights reserved.

32. APPED-101054A Confidential Output voltage from the diode bridge (Vd) AC voltage Current to the capacitor Voltage at thee capacitor (Vc) AC current (a)(b)(a)(b)(a)(b)(a) During period (a) in left fig., Vd < Vc, so current does not flow from the diode bridge to the capacitor During period (b), Vd ≧ Vc, so current flows from the diode bridge to the capacitor The AC current flows intermittently (1) 32 ©2010. Renesas Electronics Corporation, All rights reserved.

33. APPED-101054A Confidential Peak is high --- electrical energy for next half cycle has to be charged in a short period. Large and intermittent current generates much noise. Electric power companies have to prepare excessive facilities and to generate electricity corresponding to the peak of the current -> It is neither energy saving nor environmentally friendly During this period, although there is AC voltage, there is no current (i.e. no electrical power is taken into the PSU) Output voltage from the diode bridge (Vd) AC voltage Voltage at the capacitor (Vc) Current to the capacitor The AC current flows intermittently (2) 33 ©2010. Renesas Electronics Corporation, All rights reserved.

34. APPED-101054A Confidential This current wave is distorted by odd order (3 rd, 5 th, 7 th …) harmonic current PF is far smaller than 1 in this case AC voltage (sinusoidal) AC current 0 1 2 3 4 5 6 3 rd 5 th 7 th 9 th Order of harmonic current Harmonic current [A] Fundamental = 50 Hz (150 Hz)(250 Hz)(350 Hz)(450 Hz) Photograph of the waveform shown on previous page Waveform distorted by harmonic currents 34 ©2010. Renesas Electronics Corporation, All rights reserved.

35. APPED-101054A Supplement 4Inductors and magnetic saturation 35 ©2010. Renesas Electronics Corporation, All rights reserved.

36. APPED-101054A Confidential Inductors Current flowing in inductors generates magnetic fields When magnetic force (magnetic flux) through the inductor varies, the inductor generates voltage to prevent variation When DC voltage is applied to the inductor, current increases with time During the period when current is increasing, the electric power is used to form and to strengthen the magnetic force Photo: Wikipedia 36 ©2010. Renesas Electronics Corporation, All rights reserved.

37. APPED-101054A Confidential The state at which the core cannot have any larger magnetic force is called magnetic saturation. In this state, the magnetic field does not change correctly with input voltage. In case of a transformer, electric power applied on the primary side is not conducted to the secondary side correctly. Preventing saturation Enlarge the core or select material that is difficult to saturate for the core -> Transformer becomes large and heavy Magnetic saturation and size of trans. Drive the transformer with high frequency (see right fig.) -> Small, light and low cost transformers can be applied 37 ©2010. Renesas Electronics Corporation, All rights reserved.

38. ©2011. Renesas Electronics Corporation. All rights reserved. Renesas Electronics Corporation. Thank You Thank you