Adjustable Frequency Square Wave Generator with Reverse Insertion Protection

Abstract

The invention discloses an adjustable frequency square wave generator with reverse insertion protection, which comprises a starting circuit connected in sequence, a bandgap reference source, a bias circuit with temperature compensation, an oscillation circuit and an output circuit, the input of the starting circuit The terminal is connected to the power supply, the starting circuit provides constant current for the bandgap reference source, the bandgap reference source provides constant voltage for the oscillation circuit, the bias circuit provides constant current for the bandgap reference source and the oscillation circuit, and the oscillation signal generated by the oscillation circuit is generated by D The flip-flop frequency division is finally output by the output port. The circuit of the whole square wave generator is simple, and a reverse insertion protection unit is added to the starting circuit connected to the power supply, which effectively solves the problem of reverse insertion damage of the power supply and improves the reliability of the circuit; the frequency can be directly connected to the bias circuit through the external resistance. Adjustment. The startup circuit and the bandgap reference source each provide a constant current source, so that the oscillation frequency does not change with the change of the power supply voltage, which greatly improves the linearity of the square wave generator.

Description

technical field [0001] The invention relates to an LDO power supply and a switching power supply, in particular to a current mode resistance control adjustable frequency square wave generating circuit with temperature compensation. Background technique [0002] As we all know, to generate a square wave circuit, it can be realized by a multivibrator, but the power consumption varies greatly with the power supply voltage, and the frequency varies greatly, and it is not easy to oscillate under low voltage; there is also a constant current source circuit To generate oscillation, usually the constant current source circuit is powered by a power supply to provide a constant charge and discharge current to the oscillation capacitor. Using voltage division sampling from the power supply, both VREFP and VREFN change with the power supply, because in practice the system power supply will fluctuate, and the PNP tube of the constant current source has Early voltage, and the result is th...

AI Technical Summary

Problems solved by technology

Using voltage division sampling from the power supply, both VREFP and VREFN change with the power supply, because in practice the system power supply will fluctuate, and the PNP tube of the constant current source has Early voltage, and the result is that the current changes with the change of the power supply, resulting in oscillation frequency Changes will affect the frequency change of the output square wave. At the same time, most existing power supplies will produce abnormalities after the power supply is reversed, which will damage the circuit and have poor reliability.

Moreover, when the power supply is reversed in the existing circuit, there is a parasitic PN junction in the PMOS transistor or NPN transistor, which is easily damaged when the power supply is reversed.

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