DI-26参考设计 TOPSwitch-GX ® 7 W (DVB-T)电源 应用 器件 输出功率 输入电压 输出电压 拓扑结构 DVB-T TOP242PN 7W 195 – 265 VAC 2.5 V / 3.3 V / 6.2 V / 30 V 反激式 设计在更连续的状态，在不需要更大磁芯尺寸的情况下取得更好 设计特色 • 在输出地线接到大地的情况下满足CISPR22B/EN55022B传导 EMI限制 的效率和交叉调整率。 • 空载功耗<0.5 W R12、C10和L2进行传导EMI滤波；R12是防火可熔型，也做保险 • 132 kHz操作频率和可设定的电流限流点允许使用体积小、成本 丝用。如果电源不需要满足输出地线接大地的传导EMI测试， 低的EF16变压器来输出7 W功率 为了降低成本，共模电感可以一个π型滤波代替。为了空载功耗更 低，用齐纳箝位（D11和VR1）代替RCD箝位。由于3.3 V偏差要 • 元件数量少，PCB尺寸为80 × 30 × 16 mm • 集成的软启动功能减小了启动时的元件应力 求最严格（±5%），次级反馈取自3.3 V输出。2.5 V±5%的输出通 过D4接到3.3 V来实现。D1用60 V的肖特基，它的正向压降稍微 工作方式 此TOPSwitch-GX反激式电源输入电压为230 VAC±15%，输出为 高一点可以使6.2 V和30 V的输出在中心值。 4路，功率为7 W。芯片使用低成本的DIP-8封装TOP242PN，不 二次滤波（L1/C3，L2/C12和R1/C5）衰减输出噪音和纹波，使 需要外加散热片。电阻R7将TOP242PN的限流点设定为标称值的 其小于各自输出电压值的±1％。软启动电容（C7）消除了输出开 78％，刚刚超过达到低压满载时所需的值。这种特性允许变压器 机过冲。 C15 2.2 nF Y1 T1 D3 UF4002 R1 150 7 D2 SB140 L2 4.7 MH 1.8 A 30 V, 5 mA 8 1 D7-D10 1N4005 7 VR1 P6KE200 D1 SR506 D11 BYW95C C9 6.8 MF 400 V 3 TOPSwitch-GX U1 TOP242PN R12 8.2 7 Fusible 195 - 265 VAC D S D6 1N4148 C8 1 MF 50 V D4 1N5400 RTN R6 75 7 R2 15 k7 1% R5 1 k7 R7 10 k7 M CONTROL 4 U3 PC817 3.3 V, 0.5 A 2.5 V, 1 A C3 47 MF 35 V 5 L3 10 mH 0.1 A C10 47 nF X2 C1, C2 220 MF 35 V 2 6.2 V, 0.4 A C12 L1 47 MF 4.7 MH 35 V 1.8 A C4 470 MF 10 V 6 C5 10 MF 50 V C6 0.1 MF C C13 100 nF R11 6.8 7 C14 47 MF 10 V C7 10 MF 16 V R4 3.3 k7 U2 LMV431 R3 9.1 k7 1% PI-3023-101308 图1. TOPSwitch-GX 7 W DVB-T多输出电源 www.powerint.com October 2008 设计要点 变压器参数 • 为了使次级交叉调整率好，变压器设计在电流连续操作方式。 磁芯材料 EF16, gapped for 190 nH/t² • Y1安规电容C15接在初级直流高压端和次级地线，在交流输出 骨架 EF16-8 pin 绕组细节 Primary: 105T, 35 AWG Bias: 17T, 35 AWG 3.3 V Secondarty: 4T, 4 × 26 AWG T.I.W. 6.2 V Secondary: 3T, 26 AWG T.I.W. 30 V Secondary: 29T, 30 AWG T.I.W. 绕组顺序 (引脚号) Primary (1–2), tape, Bias (3–4), tape, 3.3 V (5–6), 5 V (6–7), 30 V (7–8) 电感 Primary: 2.1 mH ±10% Leakage: 50 mH (maximum) 初级谐振频率 650 kHz (minimum) 共模浪涌时噪音耦合最小。 • 遵循如下的布板经验： • C13、R11和C14靠近U1，地线回到源极脚。 • 使初级和次级环路面积最小，降低寄生漏感，改进EMI和交 叉调整率。 5 2.5 Vŋ 3.3 Vŋ 6.2 Vŋ 3.0 V Line Regulation (%) 4 3 2 PI-3021-080202 ŋ 表1. 变压器结构信息（AWG = 美国线规，T.I.W. = 三层绝缘线） 1 0 调整率(%) 负载 范围(%) -10 -7 -4 -3 -2 -1 0 1 -1 电压(V) -2 3.3 10-100 -3 5 10-100 -4 30 10-100 -5 190 2 3 4 7 100 210 230 250 270 Line Voltage (VAC) 表2. 最差情况下的输出调整率 — 所有输出从最小到最大负载 图2. 满载输入调整率 70 QP Limit Line 60 Amplitude (dBmV) PI-3022-080202 80 AV Limit Line 50 40 30 20 -10 0 -10 -20 0.15 EN_V_QPŋ EN_V_AV Quasi-Peak Scan Average Scan 1 10 30 Frequency (MHz) 图3. 传导EMI，230 V满载，输出接大地 Power Integrations 5245 Hellyer Avenue San Jose, CA 95138, USA. Main: +1 408-414-9200 Customer Service Phone: +1-408-414-9665 Fax: +1-408-414-9765 Email: [email protected] Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power Integrations does not assume any liability arising from the use of any device or circuit described herein. POWER INTEGRATIONS MAKES NO WARRANTY HEREIN AND SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS. The products and applications illustrated herein (transformer construction and circuits external to the products) may be covered by one or more U.S. and foreign patents or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A complete list of Power Integrations' patents may be found at www.powerint.com. Power Integrations grants its customers a license under certain patent rights as set forth at http://www.powerint.com/ip.htm. On the Web www.powerint.com The PI logo, TOPSwitch, TinySwitch, LinkSwitch, DPA-Switch, PeakSwitch, EcoSmart, Clampless, E-Shield, Filterfuse, StackFET, PI Expert and PI FACTS are trademarks of Power Integrations, Inc. Other trademarks are property of their respective companies. ©2002, Power Integrations, Inc. B 10/08 DI-26