Constant current drive circuit and corresponding photoelectric smoke alarm circuit

Abstract

The present invention relates to a constant current drive circuit and a corresponding photoelectric smoke alarm circuit, wherein the constant current drive circuit includes a reference voltage source module, a linear voltage regulator module, a level conversion module, a current mirror module and a first NMOS tube , wherein the linear voltage regulator module can be turned on and off according to actual needs, which can effectively reduce power consumption for some periodically used equipment. The constant current drive circuit with this structure and the corresponding photoelectric smoke alarm circuit can provide a constant current source, keep the auxiliary output performance stable in the full temperature range, meet certain timing requirements, and have no standby power consumption when not working. Stable performance, low power consumption, wide range of applications.

Description

technical field [0001] The invention relates to the technical field of circuits, in particular to a drive circuit, in particular to a constant current drive circuit and a corresponding photoelectric smoke alarm circuit. Background technique [0002] In some electronic equipment, it is often necessary to ensure that when supplying power to a specific load, the current flowing through the load can be kept constant within a certain range of power supply voltage, and when supplying power to a load whose characteristics will change as the external temperature changes, It is necessary to ensure that the output characteristics of the load must remain consistent over the entire temperature range. [0003] For example, in the field of smoke alarms, there is a requirement whether to provide a constant current. Smoke alarms can be divided into ion smoke alarms and photoelectric smoke alarms. There is an optical labyrinth in the photoelectric smoke alarm, and its structure is as follow...

AI Technical Summary

Problems solved by technology

The static power consumption of the selected linear regulator needs to be very small, and the cost is relatively high;

[0014] 2. When the smoke alarm needs to detect the battery power, it is necessary to add an additional resistor string voltage divider on the positive pole of the battery to increase the static power consumption, resulting in an increase in cost

[0016] 1. The internal integrated DC-DC boost module requires a large area, and the switching frequency is high, and the EMI effect (electromagnetic interference effect) needs to be considered when laying out the PCB;

[0017] 2. The open-drain tube (that is, the NMOS tube M1 in the figure) is an intrinsic tube, and a mask plate needs to be added when using it, which increases the cost of plate making;

[0018] 3.V o1 , V o2 Related to the temperature coefficient of the reference voltage, adjusting the Trim value of the reference voltage (that is, the output value of the reference voltage source) will change the V o1 , V o2 The temperature coefficient of the final impact on the constant current characteristics

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