Soft-start and drive circuit for 1:2 reverse charge pump and its realization method

Abstract

The invention discloses a soft-start and drive circuit for a 1: 2 reverse charge pump and an implementation method of the soft-start and drive circuit, and mainly solves the problems that an existingcharge pump driving circuit needs to be connected with a QB tube in series to realize soft start, so that the chip cost is increased, extra heat loss is generated by the QB during normal work, and thevoltage conversion efficiency is reduced. The circuit comprises a divider resistor RF1, an MOS transistor switch S and a clamping circuit A3 which are all connected with a VOUT pin of a charge pump chip; a clamping circuit A1 and a clamping circuit A2 which are connected with a BT pin of the charge pump chip; and a passive current limiting circuit which is connected with an NMOS tube Q3 and an NMOS tube Q4 on the charge pump chip. According to the invention, the product of the current limiting values of the PMOS tube Q3b and the NMOS tube Q4 and the (VIN-VOUT / 2) is used as the negative feedback quantity; and is integrated with a reference P_REF to control the current limiting values of the Q3b and the Q4, thereby ensuring that the current limiting values of the Q3b and the Q4 are the maximum values on the premise that the heat loss of the chip is less than the P_REF, i.e., the chip has the maximum loading capacity. And meanwhile, the chip cost is reduced, and the voltage conversion efficiency is improved.

Description

technical field [0001] The invention relates to an integrated circuit, in particular to a soft start and drive circuit for a 1:2 reverse charge pump and its realization method. Background technique [0002] Charge pumps are switching converters that use capacitors to store energy, where switches are used to switch the capacitors between supply and discharge states, thereby raising or lowering the supply voltage. In mobile terminals or portable electronic devices, the voltage of the power supply may be lower than the operating voltage, and the charge pump can provide the voltage of the power supply to work after the system, for example, the voltage generated by the charge pump is in the range of 3.3V to 4.0V, so as to meet Electronic equipment needs to work. [0003] Most charge pump chips are used in the 2:1 mode that reduces the input voltage to half, and few support the 1:2 mode that reverses the voltage to double the voltage. Such as figure 1 The circuit schematic diag...

AI Technical Summary

Problems solved by technology

[0010] The purpose of the present invention is to provide a soft start and drive circuit for a 1:2 reverse charge pump and its implementation method, which mainly solves the problem that the existing charge pump drive circuit needs to be connected in series with QB tubes to realize soft start, which not only increases the number of chips cost, while QB generates additional heat loss during normal operation, which reduces the problem of voltage conversion efficiency

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