Positive and negative voltage generating circuit

Abstract

The invention discloses a positive and negative voltage generating circuit, which comprises a DC-DC (direct current to direct current) circuit used for performing DC-DC conversion of input voltage and then outputting direct-current voltage through a voltage output end and outputting square signals through a pulse output end; a negative voltage generating circuit connected with the pulse output end of the DC-DC circuit and used for converting the square signals output from the DC-DC circuit into negative voltage by bootstrap of a capacitor; and a positive voltage generating circuit connected with the pulse output end of the DC-DC circuit and used for performing boost conversion of the square signals output from the DC-DC circuit by the bootstrap of the capacitor. The positive and negative voltage generating circuit disclosed by the invention is applicable to supplying the positive and negative voltage to a circuit with a small demand on current and capable of reducing the product cost and reducing the interference at the same time.

Description

technical field [0001] The invention relates to a voltage conversion circuit, in particular to a positive and negative voltage generation circuit. Background technique [0002] In the process of developing electronic products, it is necessary to consider the influence of power supply on electronic products. If the design of the power supply circuit is not good, the whole system may not work properly. In existing electronic products, there is usually only one input voltage, but the voltage required by each module in the circuit is different, which leads to several voltages in the entire circuit at the same time, and sometimes a negative voltage is required. It is necessary to step up, step down, and reverse the polarity of the input voltage to make it meet the voltage required by each module of the circuit. The more common boosting method is to use a DC-DC boosting circuit. The DC-DC boosting circuit is characterized by high conversion efficiency and large output current; th...

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Problems solved by technology

[0003] The output current of the above two circuits can generally reach hundreds of milliamperes or even several amperes. When these two circuits are used to provide positive and negative bias voltage for LCD or negative voltage for 232 communication circuit, since the equipment is in standby state Only a few microamperes of current are needed, so it will cause a waste of electricity, and it is not suitable for occasions with small current requirements. In addition, DC-DC booster circuits and DC-DC reverse polarity circuits must use DC-DC Chips, inductors and large capacitors, these components will increase the cost of the product and occupy a large space, which is not conducive to the miniaturization of the product. At the same time, because these two circuits have a high switching frequency, they will generate large electromagnetic interference. In practical applications, more protection measures need to be added to prevent interference from interference sources to other circuit modules

[0004] Therefore, the existing booster circuit and negative voltage circuit are not only not suitable for occasions with small current requirements, but also have high cost and are prone to interference

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