Linear constant-current circuit

Abstract

The invention discloses a linear constant-current circuit. The linear constant-current circuit comprises a first power switch, a second power switch, an output capacitor, a current sampling resistor,an operational amplifier and a control circuit of the second power switch, wherein a positive end of the output capacitor is connected with a positive voltage end of a circuit load, a drain of the first power switch is connected with a negative voltage end of the circuit load, a source of the first power switch is connected to system ground by the current sampling resistor, a gate of the first power switch is connected with an output end of the operational amplifier, a drain of the second power switch is connected with a drain of the first power switch, a source of the second power switch is connected with a negative end of the output capacitor and is used as reference ground of the control circuit, a gate of the second power switch is connected with an output end of the control circuit, and the control circuit is used for generating a second switch control signal for switching on and off the second power switch according to an output representation voltage, a second reference voltageand a third reference voltage which represent the circuit load or output voltages of two ends of the output capacitor.

Description

technical field [0001] The invention relates to the field of circuits, in particular to a linear constant current circuit. Background technique [0002] figure 1 The working principle diagram of the traditional linear constant current circuit is shown. exist figure 1 In the linear constant current circuit shown, the positive terminal and negative terminal of the output capacitor Co are respectively connected to both ends of the load; the drain of the power switch S1 is connected to the negative terminal of the output capacitor Co; the source of the power switch S1 is sampled through the current The resistor Rcs is connected to the system ground; the gate of the power switch S1 is connected to the output terminal of the operational amplifier (EA), wherein: the current sampling resistor Rcs samples the output current Io flowing through the load to generate a current sampling voltage Vcs; the operational amplifier (EA) ) Based on the current sampling voltage Vcs and the refe...

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Problems solved by technology

[0006] In some application scenarios, the low-frequency ripple of the output current Io is required to be as small as possible, which requires a larger capacity of the output capacitor Co, but the output capacitor Co is generally an electrolytic capacitor, and the larger the capacity, the larger the volume. This prevents miniaturization of the power supply volume

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