Constant voltage supply circuit

Abstract

The invention relates to a constant voltage circuit for switching the constant voltage circuit for heavy load to constant voltage circuit for light load without rapidly reducing output voltage and not influenced by instant change of output circuit. The said constant voltage circuit comprises: constant voltage circuit for heavy load (4), constant voltage circuit for light load (6), output control signal (ECO), a switching part (10) for operating the constant voltage circuit for heavy load (4) or constant voltage circuit for light load (6), and a current detecting circuit (2). The said current detecting circuit (2) comprises output transistor M1 and comparison circuit (12) to output the corresponding signal with the comparative result of comparison circuit (12). The switching part (10) is at state of making the constant voltage circuit for light load (6) work by control signal (ECO). The switching part makes the constant voltage circuit for light load (6) work, only when the current signal below the threshold value is inputted by said current detecting circuit.

Description

technical field [0001] The present invention relates to a constant voltage power supply circuit comprising a constant voltage circuit for light load with small power supply and a constant voltage circuit for heavy load with large power supply. Background technique [0002] In recent years, electronic devices have been required to save electric power from environmental considerations. This tendency is particularly noticeable for electronic devices driven by batteries. In order to save power, it is very important to reduce the power consumed by electronic devices, improve the power efficiency of the power supply circuit itself, and suppress useless power consumption. [0003] As one of the methods of reducing the power consumption of the electronic equipment, when the electronic equipment is not in operation, setting a standby state in which the operation of circuits in the electronic equipment is stopped to reduce power consumption can be cited. However, even if the electro...

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Problems solved by technology

[0012] The problem with the power supply circuit in (1) above is that the output voltage drops sharply when switching from the constant voltage circuit for heavy load to the constant voltage circuit for light load when the output current is greater than the maximum output current of the constant voltage circuit for light load. , resulting in malfunction

[0013] The problem with the power supply circuit of (2) above is that the output voltage tends to generate noise because the constant voltage circuit for light load and the constant voltage circuit for heavy load are switched on / off even when the output current decreases instantaneously. Generate unexpected noise, resulting in malfunction

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