Design Idea DI-12 ® TOPSwitch-GX 16 W, Universal ® Input, Lead Acid Battery Charger Application Device Power Output Input Voltage Output Voltage Topology Battery Charger TOP244P 16 W 85-265 VAC 13.55 V at 25 ˚C Flyback Design Highlights TOP244P requires no external heatsink, using the PC board instead. • Lowest cost and low component count solution • Universal input voltage replaces the need for multiple linear based designs • High efficiency: >75% • Integrated line undervoltage detection (UV) and overvoltage (OV) power system surge protection • Constant voltage / constant current (CV/CC) output • Temperature compensated output voltage • Monitor input to allow state of charge measurements During the first 10 ms of operation, internal soft-start is enabled, lowering stresses on the internal power MOSFET, clamp and output rectifier. Built-in switching frequency jitter reduces conducted EMI, allowing the design to meet EN55022B limits with simple input filtering. Diode D1 and Zener VR1 clamp the leading edge drain voltage spike caused by transformer leakage inductance. Operation The circuit shown in Figure 1 provides a CV/CC output for charging lead-acid batteries in applications such as fire/burglar alarms and emergency lighting. The design utilizes many of the features of the TOPSwitch-GX family. Line undervoltage and overvoltage (100 V and 450 V, respectively) are implemented using a single resistor (R13). Line undervoltage detection eliminates power-up/down output glitches, while overvoltage shutdown provides protection for short line transients and longer duration power system surges, removing the need for an input MOV. The DIP8 package of the C7 1 nF Y1 D1-D4 1N4007V 1 A, 1000 V 1 VR1 P6KE 200 Lead acid batteries for standby use are normally charged at ~2.3 V per cell and 0.1 A per Ah of capacity. Resistor R1, U2, C9, Q1, R3, R4 and R5 form the current limit circuit. Resistor R3 controls the current limit (1.2 A typical). Resistor R5 ensures sufficient voltage to drive the opto LED, even with the output shorted. Capacitor C9 and R4 provide compensation and limit Q1 base current. The output voltage is controlled using a TL431 voltage reference (U3). Resistors R7, R8, R9 and RT1 program output voltage as a function of temperature (Figure 3) to approximate that required by the lead-acid battery. During CV operation, DC gain is set by R6. Capacitor C8, C5 and R10 provide loop compensation. Bias for U3 is provided by R2. L2 3.3 µH D2 UG4D 8T 24 AWG Triple Insulated C3 220 µF 35 V C2 560 µF 35 V R2 1 kΩ 5,6 D1 UF4005 D3 BAV20 2 L1 22 mH C1 47 µF 400 V R13 2 MΩ U1 TOP244P D C6 0.1 µF 250 VAC F1 3.15 A M 8T 30 AWG 3 C4 0.1 µF 50 V t° R11 27 kΩ Q2 2N4401 U2 PC817A R8 52.7 kΩ R6 470 Ω C L RT1 4.7 kΩ R1 4.7 Ω CONTROL S R7 11.8 kΩ 4 TOPSwitch-GX 85-265 VAC MON R12 10 kΩ C8 0.1 µF R10 6.8 Ω C5 47 µF 10 V C9 0.47 µF Q1 2N4401 N R3 0.5 Ω 1W R4 470 Ω R5 0.6 Ω 1W U3 TL431 R9 12.7 kΩ RTN PI-3404-112502 Figure 1. TOPSwitch Lead Acid Battery Charger. DI-12 +13.55 V 7,8 www.powerint.com November 2002 DI-12 For battery detection and monitoring, R11, R12 and Q2 reduce the output voltage to approximately 8 V when a 5 V signal is applied to R12. This allows the battery voltage to be measured, giving the state of charge. TRANSFORMER PARAMETERS Bobbin YC 2204 (Ying Chin) Winding Details Primary: 56T, 30 AWG Bias: 8T, 2 x 30 AWG Secondary: 8T, 28 AWG T.I.W. (T.I.W. = Triple Insulated Wire) Winding Order (Pin Numbers) Primary (2-1), tape, Bias (4-3), tape, Secondary (7,8-5,6) Inductance Primary: 475 µH ±10%, Leakage: 35 µH (maximum) Primary Resonant Frequency 300 kHz (minimum) Key Design Points Table 1. Transformer Construction Information. 2.45 PI-2267-062598 • The value of R3 sets the typical output current limit threshold given by: R3 = 0.6 / ILIMIT. • Rate R3 and R5 accordingly for power dissipation (1 W). • Ensure total voltage across R3 and R5 is greater than 1.5 V at ILIMIT if control to 0 V (output shorted) is required. • Ensure voltage at cathode of D3 is >6 V at ILIMIT. Add additional bias winding turns, if necessary, to maintain output current control to 0 V (output shorted). • RT1: Philips part # 2322-640-54472. • Select tolerance of U2, R7, R8 and R9 to give the desired overall CV tolerance (R7, R8 and R9 as 0.1%; R10 as 1% and U2 as 0.5% gives overall tolerance <2%). TDK PC40 EE22/29/6-Z, 2 Gap for ALG = 145 nH/T Core Material Output Voltage (V) PI-2265-040401 Ambient Temperature = 30 °C 14 12 8 Charging Voltage (V/cell) 2.40 16 2.35 Typical Limit 2.30 2.25 2.20 4 2.15 -10.0 230 VAC 90 VAC 0.0 10.0 20.0 30.0 40.0 50.0 60.0 Temperature (°C) 0 0 0.2 0.4 0.6 0.8 1.0 1.2 Figure 3. Cell Charging Voltage vs Temperature. Output Current (A) Figure 2. Output Characteristic (VOUT vs IOUT) For the latest updates, visit our Web site: www.powerint.com 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, nor does it convey any license under its patent rights or the rights of others. The products and applications illustrated herein (including circuits external to the products and transformer construction) 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. The PI Logo, TOPSwitch, TinySwitch, LinkSwitch and EcoSmart are registered trademarks of Power Integrations, Inc. PI Expert is a trademark of Power Integrations, Inc. ©Copyright 2002, Power Integrations, Inc. WORLD HEADQUARTERS AMERICAS Power Integrations, Inc. San Jose, CA 95138 USA Customer Service: Phone: +1 408-414-9665 Fax: +1 408-414-9765 e-mail: [email protected] CHINA Power Integrations International Holdings, Inc. China Phone: +86-755-8367-5143 Fax: +86-755-8377-9610 e-mail: [email protected] A 11/02 EUROPE & AFRICA Power Integrations (Europe) Ltd. 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