Low-offset and fast-response voltage-controlled current source, control method and power circuit applying voltage-controlled current source

Abstract

The invention relates to a low-offset and fast-response voltage-controlled current source. In the voltage-controlled current source which is realized by adopting an operational amplifier, an input offset voltage which is larger relative to an input reference voltage is reduced to an acceptable range through use of an automatic zeroing method, and the output error of the voltage-controlled current source is reduced. The slew rate of the operational amplifier is improved by adding a sampling hold circuit so as to realize the fast response of a circuit. The low-offset and fast-response voltage-controlled current source is especially suitable for applications, such as an LED driving circuit, requiring fast response. In addition, the input offset is reduced by adopting the automatic zeroing method, the low input offset of the voltage-controlled current source can be realized by adopting a standard CMOS (Complementary Metal Oxide Semiconducotr) process, the change of the input offset along with the changes of temperature, time, illumination and irradiation is unnecessarily considered, and the requirement on layout matching is lower, therefore the production cost and time are reduced.

Description

technical field [0001] The invention relates to a voltage-controlled current source, in particular to a voltage-controlled current source with low offset and fast response, a control method thereof, and a power supply circuit using the same. Background technique [0002] The voltage-controlled current source is widely used because of its simple design and convenient debugging. There are many ways to implement the voltage-controlled current source, among which the implementation method using the operational amplifier is used in practical applications, especially in the application of small input reference voltage, a small input offset at the input terminal of the operational amplifier may lead to a large output error, Affects the accuracy of the required current source. [0003] To solve this problem, the conventional method is to use high-power field effect transistor MOSFET or bipolar transistor BJT to form the input differential pair in the operational amplifier, and then...

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Problems solved by technology

However, this scheme does not reduce the requirements for layout matching. At the same time, the offset current at the output terminal changes with the temperature, light and radiation due to the characteristics of the field effect transistor MOSFET itself.

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