Other factors are trace width total printed circuit copper area copper

Other factors are trace width total printed circuit

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Other factors are trace width, total printed circuit copper area, copper thickness, single− or double−sided, multilayer board, the amount of solder on the board or even color of the traces. The size, quantity and spacing of other components on the board can also influence its effectiveness to dissipate the heat. Figure 26. Inverting Buck−Boost Develops −12 V D1 1N5822 L1 68 mH Output 2 4 Feedback 12 to 40 V Unregulated DC Input C in 100 mF 1 5 3 ON/OFF GN D +V in −12 V @ 0.7 A Regulated Output C out 2200 mF LM2576−12 ADDITIONAL APPLICATIONS Inverting Regulator An inverting buck−boost regulator using the LM2576−12 is shown in Figure 26. This circuit converts a positive input voltage to a negative output voltage with a common ground by bootstrapping the regulators ground to the negative output voltage. By grounding the feedback pin, the regulator senses the inverted output voltage and regulates it. In this example the LM2576−12 is used to generate a −12 V output. The maximum input voltage in this case cannot exceed +28 V because the maximum voltage appearing across the regulator is the absolute sum of the input and output voltages and this must be limited to a maximum of 40 V.
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LM2576 19 This circuit configuration is able to deliver approximately 0.7 A to the output when the input voltage is 12 V or higher. At lighter loads the minimum input voltage required drops to approximately 4.7 V, because the buck−boost regulator topology can produce an output voltage that, in its absolute value, is either greater or less than the input voltage. Since the switch currents in this buck−boost configuration are higher than in the standard buck converter topology, the available output current is lower. This type of buck−boost inverting regulator can also require a larger amount of startup input current, even for light loads. This may overload an input power source with a current limit less than 5.0 A. Such an amount of input startup current is needed for at least 2.0 ms or more. The actual time depends on the output voltage and size of the output capacitor. Because of the relatively high startup currents required by this inverting regulator topology, the use of a delayed startup or an undervoltage lockout circuit is recommended. Using a delayed startup arrangement, the input capacitor can charge up to a higher voltage before the switch−mode regulator begins to operate. The high input current needed for startup is now partially supplied by the input capacitor C in . It has been already mentioned above, that in some situations, the delayed startup or the undervoltage lockout features could be very useful. A delayed startup circuit applied to a buck−boost converter is shown in Figure 27, Figure 33 in the “Undervoltage Lockout” section describes an undervoltage lockout feature for the same converter topology.
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  • Spring '19
  • Margaret Earle
  • Switched-mode power supply, Vout

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