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Low EMC Charge Pump for Supply System Disclosure Number: IPCOM000131955D
Original Publication Date: 2005-Dec-25
Included in the Prior Art Database: 2005-Dec-25

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The problem to be solved is to reduce EMC (Electromagnetic Compatibility) caused by charge pump versus Battery (clean supply) in a supply system. In Figure1 is shown a typical supply system. The main input is IN1 where a battery (or a shared supply) is connected. A pre-regulator block generates the IN2 supply voltage. IN2 is the supply for most of the other parts of the system (i.e. some post regulators). Inside automotive supply systems, it becomes more and more important to switch on the entire system at battery voltages, which are continuously lower. Therefore a start up booster (i.e. a charge pump) is needed (as shown in Figure 2) to start-up at low battery the pre-regulator (and when needed also the post regulators Post-reg1 … Post-regn). Charge pumps are strong EMI (Electromagnetic Interference) emitters and the battery (or a shared supply that it is named IN1) needs during normal operation to be as clean as possible because of other devices are connected to that line. It is therefore mandatory reducing or, if possible, avoiding injection of disturbances into battery. It means that since efficient boost converter (e.g. a charge pump) is necessary inside the power system, because of the switching nature of those high efficiency converters, it becomes important to avoid or to limit injection of disturbances into Battery.