AN2063 Application note VIPower™: low consumption standby power with the VIPerx2A family Introduction The new regulation on the power supply standby consumption for the battery charger is more and more stringent. Thanks to the VIPerx2A family low power consumption, a battery charger can be built in standby mode with no-load of 100 mW. This charger solution with the VIPer12A-E is presented in Table 1. Some general features: • Ultra low standby power dissipation • Burst mode operation in standby • 72% typical efficiency • Current mode controller • Output short-circuit protection • Thermal shutdown protection Table 1. Operation conditions Parameters Limits Input voltage range 90 to 264 VAC Input frequency range 50 to 60 Hz Output voltage 5V Output current 800 mA Output power 4W Efficiency 72% typical Line regulation 0.5% Load regulation 1% Output ripple 30 mVpp Safety Short-circuit protection November 2014 DocID10955 Rev 2 1/15 www.st.com 15 Contents AN2063 Contents 1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 General circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Charger application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1 Schematic general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 Solutions for energy saving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.3 Performance results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.3.1 Input power consumption at no-load condition . . . . . . . . . . . . . . . . . . . . 7 3.3.2 Standby operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.3.3 Load, line regulation and efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3.4 Load transient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3.5 Switching waveforms of normal operation at full load . . . . . . . . . . . . . . 10 4 Transformer specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5 Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2/15 DocID10955 Rev 2 AN2063 1 Description Description The VIPer12A-E is a high voltage integrated circuit intended to be used as a primary side switch on the offline power supply, in a monolithic structure housed in DIP8 or SO8 package. It includes a PWM driver, a power MOSFET with 730 V breakdown voltage, a start-up circuit and several protection circuits. It minimizes the count of external parts , reduces the product size and power consumption. This application note describes the results obtained when the VIPer12A-E is used in mobile charger applications. Figure 1. Evaluation board bottom foil (not in scale) DocID10955 Rev 2 3/15 15 General circuit description 2 AN2063 General circuit description This board is a flyback regulator, delivering 0.8 A to 5 V. The AC input is rectified and filtered by the diodes D1, D2, D3, D4, the bulk capacitor C1, and C2 to generate the high voltage DC bus applied to the primary winding of the transformer, TR1. C1, L1, and C2 provide EMI filtering for the circuit. D9 and D10 form the snubber circuit, which reduces the leakage spike and voltage ringing on the drain pin of the VIPer12A-E. The output voltage is regulated by a TL431 (U3) via an optocoupler (U2) to the feedback pin. The output voltage ripple is controlled by the capacitor, C7, with an additional LC PI filter configuration made up of L2 and C8. The output voltages can be modified by changing the transformer turn ratio and modifying the R6 and R7 resistance values in the feedback loop. 4/15 DocID10955 Rev 2 R0 10 D3 1N4007 D1 1N4007 D4 1N4007 D2 1N4007 C1 4.7µ 400V L1 680µ C2 4.7µ 400V C5 33µ 50V C6 10µ 33V C4 47n U2 PC817 DocID10955 Rev 2 CONTROL U1 VIPer12A FB VDD Option A SOURCE DRAIN Option E D7 1N4148 D6 1N4148 D9 STTH1L06 Option C D10 P6KE180 R2 0 R1 0 Option B T1 C11 1n 1kV D8 1N5822 U3 TL431 U2 PC817 C7 470µ 16V C10 100n R4 1.5k Option E R3 220 L2 4.7µ C8 220µ 10V R6 43k R7 43k DC AN2063 General circuit description Figure 2. Application schematic 5/15 15 Charger application AN2063 3 Charger application 3.1 Schematic general description As the total input power dissipation at no-load condition of this solution is less than 0.1 W, the power losses of each component have to be saved. Below the major approaches adopted in this evaluation board. 3.2 Solutions for energy saving 1. Losses of the VIPer12A-E controller. The power losses of the VIPer12A-E control part can be calculated by below formula: Pviper = Vdd * Idd1 where: - Vdd is the supply voltage of the VIPer12A-E control part (range: 9 V-38 V) - Idd1 is the operation current of the VIPer12A-E control part (typical value: 4.5 mA) Vdd is set by considering two operative conditions; if the VIPer12A-E power has to be saved, the Vdd value has to be lowered and, at the same time the Vdd has to be higher than 10 V, which is the required normal operation value of the VIPer12A-E (with 1 V margin). Vdd value (10 V) fixes the suitable turn ratio between secondary and auxiliary winding. 2. Optimized voltage source for optocoupler. In a flyback topology, the voltage source of the optocoupler primary side is normally connected to the Vdd of the IC directly, but in this board, in order to save energy, another winding is inserted in the transformer to supply the optocoupler; the voltage supplied by this winding is lower than the Vdd value (typical value 3 V). 3. Snubber circuit configuration. An RCD clamp is a popular cheap solution, however it dissipates power even at no-load condition, in fact there is a reflected voltage across the clamp resistor all the time. The power losses on the resistor can be calculated as follows: 2 PR VR 1 2 = ------------ + --- ⋅ L LK ⋅ I lim ⋅ f sw R min 2 where VR is the reflected voltage; Rmin is the resistor value; LLK is the leakage inductance; Ilim is the peak current limitation value of the VIPer12A-E and fsw is the switching frequency. As at no-load condition, the energy ½*LLK*Ilim*fsw can be neglected, then the RCD losses could be considered as: PR=VR*VR/Rmin in this case with VR=70 V, Rmin=82 kΩ, PR is around 60 mW. 6/15 DocID10955 Rev 2 AN2063 Charger application This 60 mW power at no-load condition can be saved using the transil clamp to replace the RCD configuration in the snubber circuit. 4. Optional for the voltage reference devices (TS431 or TL431 or Zener) The TS431, the TL431 and the Zener can be used as voltage regulators. The TS431 shows the low minimum operation current with the typical value of 150 A. This feature is quite useful, because the biasing resistor can be removed without any voltage regulation performance loss. With this device, the power losses can be saved on the biasing resistor with typical value of 5-8 mW. The TL431 is a cost-effective solution for the constant voltage. The weakness of this device, in this special application, is its operation current higher than 1 mA. In order to get good voltage regulation performance at full load condition, a biasing resistor is very important, but this leads to an additional power loss. If the requirement of the output voltage performance is not so tight, a Zener can be used as voltage reference. The standby power in no-load condition is lower than 0.1 W with the 3 optional solutions of voltage reference above. The best solution depends on customers' requests. 5. The short-circuit of resistors for current limitation on the auxiliary windings. 3.3 Performance results 3.3.1 Input power consumption at no-load condition Table 2. Standby power Input power consumption VIN IIN PIN 100 Vdc 505 μA 50.5 mW 300 Vdc 252 μA 75.6 mW 380 Vdc 215 μA/203 μA 81.7 mW/77.2 mW As shown in Table 1, the standby power is measured at DC voltage input in order to have more precision in the input power data. At the high line input of 380 Vdc input, this board standby power is around 82 mW (with theTL431). DocID10955 Rev 2 7/15 15 Charger application AN2063 Figure 3. Standby consumption at 380 Vdc input 3ULPDU\P: P: 7 6HFRQGDU\P: 9LSHU P: P: &ODPSHU P: 6ZLWFKLQJORVVHV P: 5HFWLILHUGLRGH 2SWR FRXSOHU 2SWR P: %LDVLQJ5HVLVWRU P: P: 7/IRU&9 P: 7UDQVIRUPHUORVVHV P: 3.3.2 Standby operation Figure 4. Vds and Id at burst mode When no-load is applied to the secondary side, the VIPer12A-E works in burst mode by skipping some switching cycles and this behavior is shown in Figure 4. Thanks to this feature, the VIPer12A-E can save a lot of the switching losses reducing the standby power consumption. 8/15 DocID10955 Rev 2 AN2063 3.3.3 Charger application Load, line regulation and efficiency Figure 5. Load regulation The output load changes from 0 A to full load 0.8 A while the line input voltage is set as 100 Vdc, 300 Vdc, 380 Vdc. The board has a load, line regulation lower than 1%. Figure 6. System efficiency The measurements are based on input voltage of 100 Vdc,300 Vdc, 380 Vdc. The typical efficiency measured is about 73%. Figure 6 shows the efficiency measured when IOUT is set at different values from 200 mA to maximum value of 800 mA. DocID10955 Rev 2 9/15 15 Charger application 3.3.4 AN2063 Load transient Figure 7. Vds and Id at VIN=100 Vdc, POUT=4 W - Figure 8. Vds and Id at VIN=380 Vdc, POUT=4 W 50 mV/division 50 mV/division As shown in Figure 7 and Figure 8 the maximum overshoot and undershoot value of the output voltage is less than 150 mV at transient tests. 3.3.5 Switching waveforms of normal operation at full load Figure 9. Vds and Id at VIN=100 Vdc, POUT=4 W Figure 10. Vds and Id at VIN=380 Vdc, POUT=4 W Figure 8 and Figure 9 show the drain voltage and drain current during normal operation at full load. The power supply operates in the continuous current mode at low line and in discontinue current mode at high line input as seen from the waveforms. 10/15 DocID10955 Rev 2 AN2063 4 Transformer specification Transformer specification Table 3. Transformer characteristics Winding description Symbol Number turns Primary P1 145 0.19 mm 2 1 EE-16; Lp = 2.5 mH at 1 V, 1 kHz Secondary S1 11 0.50 mm 9 7 Tipple isolated wire Auxiliary1 A1 16 0.10 mm 4 5 Auxiliary2 A2 15 0.10 mm 5 3 Wire size Start pin End pin Remarks Figure 11. Transformer structure 3ULPDU\ 3ULPDU\ 6HFRQGDU\ 6HFRQGDU\ DocID10955 Rev 2 11/15 15 Bill of material 5 AN2063 Bill of material Table 4. Bill of material 12/15 Symbol Part list description C1,C2 Elect Cap 4.7 µF/400 V C4 47 nF/25 V C5 Elect cap 33 µF/25 V C6 Elect cap 10 µF/6.3 V C7 Elect cap 470 µF/16 V C8 Elect cap 220 µF/10 V C10 Film 100 nF/50 V C11 Y cap 1 nF/1 KV R0 10 Ω R1,R2 0Ω R3 220 Ω R4 1.5 KΩ R6 43 KΩ R7 43 KΩ/130 KΩ D1,D2,D3,D4 1N4007 D6,D7 1N4148 D8 1N5822 D9 STTH1L06 D10 P6KE180 L1 680 µH L2 4.7 µH T1 2.7 mH EE-16 vertical U1 VIPer12A-E U2 PC817 U3 TL431/TS431 DocID10955 Rev 2 Note Fuse TL431:1.5 K/TS431: remove TL431:43 K/TS431: 130 K AN2063 6 Conclusions Conclusions When the board works in standby, it consumes less than 0.1 W meeting the “Blue Angel” norm. The total power consumption measured at 100 Vdc input with zero load on output is approximately 50 mW, while at 380 Vdc input this value is about 80 mW. This unit operates in burst mode when the output load is reduced to zero and normal operation is resumed automatically when the power gets back to a level higher than the standby power. The output voltage remains regulated even when the board works in burst mode. DocID10955 Rev 2 13/15 15 Revision history 7 AN2063 Revision history Table 5. Document revision history 14/15 Date Revision 10-Nov-2014 2 Changes Content reworked to improve readability, no technical changes. DocID10955 Rev 2 AN2063 IMPORTANT NOTICE – PLEASE READ CAREFULLY STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, enhancements, modifications, and improvements to ST products and/or to this document at any time without notice. Purchasers should obtain the latest relevant information on ST products before placing orders. ST products are sold pursuant to ST’s terms and conditions of sale in place at the time of order acknowledgement. Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or the design of Purchasers’ products. No license, express or implied, to any intellectual property right is granted by ST herein. Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such product. ST and the ST logo are trademarks of ST. All other product or service names are the property of their respective owners. Information in this document supersedes and replaces information previously supplied in any prior versions of this document. © 2014 STMicroelectronics – All rights reserved DocID10955 Rev 2 15/15 15