Voltage negative feedback circuit with current compensation applied to precise current copying circuit

Abstract

The invention belongs to the technical field of integrated circuits, and particularly relates to a current compensation circuit. The current compensation circuit mainly comprises a replica resistor, an operational amplifier and a Miller compensation circuit. The replica resistor is used for replicating a feedback resistor in the reference voltage buffer; the inverting input end of the operational amplifier is connected to the voltage on the replica resistor, and the operational amplifier is used for controlling the voltage on the replica resistor to enable the voltage to be the same as the reference voltage of the reference voltage buffer, so that the output current is the same as the loss current flowing through the feedback resistor, and the effect of compensating the current is achieved; the Miller compensation circuit is used for ensuring the stability of a feedback loop, the capacitor enables a dominant pole and a secondary pole in the circuit to be far away, and the gate of the MOS tube is connected with a power supply to replace a resistor, so that a zero point of a right half plane introduced by the capacitor is moved to a left half plane to ensure the stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, and specifically relates to a current compensation circuit Background Art

[0002] Current compensation circuit is a technique used in reference voltage buffers or other driving circuits to improve the system's responsiveness and stability to dynamic load changes, especially when the load current demand is large and changes rapidly.

[0003] In CMOS technology, a reference voltage buffer capable of providing large current charging and discharging is usually required. Its usual structure is a current replication structure. By connecting a current source and a load in the same proportion as in the control loop in parallel at the output end, the same reference voltage as in the control loop and several times the output current can be generated. Since there is a feedback loop in the control loop, which causes a part of the current to be lost, the current replication structure will introduce some errors. Usually, the parallel output end of the current replication structure circuit cannot be connected in parallel more than 10 times, otherwise it will introduce a huge error. The advantage of a simple current replication structure circuit is that it has a simple structure and relatively lower power consumption. When there is a large demand for output current and a more stringent requirement for output voltage accuracy, additional circuits are required to ensure its performance. Summary of the invention

[0004] In view of the large error problem and output current limitation problem caused by the current replication structure circuit mentioned above, the present invention proposes a current compensation circuit, which introduces feedback to ensure that the correct current enters the control loop under specific working conditions to ensure the stability of the circuit. After the circuit starts and enters the working point, the required compensation current is basically constant, and the required power consumption is relatively low.

[0005] The current compensation circuit mainly includes a replica resistor, an operational amplifier, and a Miller compensation circuit; the replica resistor is used to replicate the feedback resistor in the reference voltage buffer; the inverting input terminal of the operational amplifier is connected to the voltage on the replica resistor, and the operational amplifier is used to control the voltage on the replica resistor to make it the same as the reference voltage of the reference voltage buffer, so that the output current is the same as the loss current flowing through the feedback resistor, thereby playing a role in compensating the current; the Miller compensation circuit is used to ensure the stability of the feedback loop, the capacitor keeps the main pole and the secondary pole in the circuit away, and the MOS tube gate is connected to the power supply instead of the resistor to move the right half plane zero introduced by the capacitor to the left half plane to ensure stability;

[0006] The replica resistor comprises a third resistor, one end of which is grounded and the other end of which is connected to the first capacitor, the drain of the third PMOS tube and the gate of the third NMOS tube;

[0007] The operational amplifier comprises a first NMOS tube, a second NMOS tube, a third NMOS tube, a fourth NMOS tube, a first PMOS tube, a second PMOS tube, a third PMOS tube, and a fourth PMOS tube, wherein the gates of the first NMOS tube and the second NMOS tube are both connected to the drain of the first NMOS tube and to a bias current source, the sources of the first NMOS tube and the second NMOS tube are both grounded, the drain of the second NMOS tube is connected to the sources of the third NMOS tube and the fourth NMOS tube; the gate of the third NMOS tube is connected to one end of the third resistor, and the drain is connected to the drain and gate of the first PMOS tube and the gate of the second PMOS tube; the gate of the fourth NMOS tube is connected to one end of the first resistor and the drain of the fourth PMOS tube, and the drain is connected to the drain of the second PMOS tube, the gate of the third PMOS tube, the gate of the fourth PMOS tube, and the drain of the fifth NMOS tube; the sources of the first PMOS tube, the second PMOS tube, the third PMOS tube, and the fourth PMOS tube are all connected to a power supply;

[0008] The Miller compensation circuit comprises a fifth NMOS tube and a first capacitor, wherein the source of the fifth NMOS tube is connected to the other end of the first capacitor, and the gate is connected to the power supply;

[0009] In the solution of the present invention, the replica resistor is used to replicate the feedback resistor in the reference voltage buffer. The resistance of the resistor is the same as the resistance of the feedback resistor. It is used to generate a replica current in the current compensation circuit to ensure that the compensation current is the same as the current loss caused by the feedback resistor.

[0010] The inverting input of the operational amplifier is connected to the voltage on the replica resistor, and the non-inverting input is connected to the output load of the main circuit. Since the feedback coefficient of this node is small, it is connected to the non-inverting input to ensure the overall negative feedback to ensure stability. The operational amplifier is used to control the voltage on the replica resistor to make it the same as the reference voltage of the reference voltage buffer, so that the output current is the same as the loss current flowing through the feedback resistor, thereby playing the role of compensation current.

[0011] Miller compensation circuit is used to ensure the stability of the feedback loop. The capacitor keeps the main pole and the secondary pole in the circuit away from each other. The gate of the MOS tube is connected to the power supply instead of the resistor, so that the right half plane zero introduced by the capacitor is moved to the left half plane to ensure stability. Using MOS tubes instead of resistors can save area.

[0012] The beneficial effects of the present invention are: by introducing feedback, the correct current is compensated to enter the control loop under specific working conditions to ensure the stability of the circuit. After the circuit starts and enters the working point, the required compensation current is basically constant, and the required power consumption is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of a current compensation circuit of the present invention;

[0014] Figure 2 The schematic diagram is a schematic diagram of the present invention applied to a current replication structure circuit. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings.

[0016] The current compensation circuit structure of the present invention is as follows Figure 1 As shown, the replica resistor is used to replicate the feedback resistor in the reference voltage buffer. The resistance of the resistor is the same as the resistance of the feedback resistor and is used to generate a replica current in the current compensation circuit to ensure that the compensation current is the same as the current loss caused by the feedback resistor.

[0017] The inverting input of the operational amplifier is connected to the voltage on the replica resistor, and the non-inverting input is connected to the output load of the main circuit. Since the feedback coefficient of this node is small, it is connected to the non-inverting input to ensure the overall negative feedback to ensure stability. The operational amplifier is used to control the voltage on the replica resistor to make it the same as the reference voltage of the reference voltage buffer, so that the output current is the same as the loss current flowing through the feedback resistor, thereby playing the role of compensation current.

[0018] Miller compensation circuit is used to ensure the stability of the feedback loop. The capacitor keeps the main pole and the secondary pole in the circuit away from each other. The gate of the MOS tube is connected to the power supply instead of the resistor, so that the right half plane zero introduced by the capacitor is moved to the left half plane to ensure stability. Using MOS tubes instead of resistors can save area.

[0019] Application scenarios of the present invention are as follows Figure 2 As shown, a reference voltage buffer structure that can provide large current charging and discharging is usually a current replication structure. By connecting a current source and a load in the same proportion as in the control loop in parallel at the output end, the same reference voltage and several times the output current as in the control loop can be generated. Since there is a feedback loop in the control loop, which causes a part of the current to be lost, the current replication structure will introduce some errors. Usually, the parallel output end of the current replication structure circuit cannot be connected in parallel with more than 10 times the number, otherwise it will introduce a huge error. Usually, this structure is controlled by feedback after resistor voltage division, so the final output end circuit usually only needs to connect the current MOS tube and the load in parallel, and the error current is corrected by the current compensation circuit of the present invention.

Claims

1. A voltage negative feedback circuit with current compensation used in an accurate current replication circuit, characterized in that: It includes voltage detection and current replication; the voltage detection node is connected to the non-inverting input terminal of the operational amplifier and introduced into the input of the operational amplifier as a standard voltage; the voltage generated by the current replication loop is fed back to the inverting input terminal of the operational amplifier to form a stable negative feedback, ensuring that the current can be accurately replicated and compensated back to the main circuit under different conditions; The current compensation circuit mainly includes a replica resistor, an operational amplifier, and a Miller compensation circuit. The replica resistor is used to replicate the feedback resistor in the reference voltage buffer; the inverting input terminal of the operational amplifier is connected to the voltage on the replica resistor, and the operational amplifier is used to control the voltage on the replica resistor to make it the same as the reference voltage of the reference voltage buffer, so that the output current is the same as the loss current flowing through the feedback resistor, thereby playing a role in compensating the current; the Miller compensation circuit is used to ensure the stability of the feedback loop, the capacitor keeps the main pole and the secondary pole in the circuit away, and the gate of the MOS tube is connected to the power supply instead of the resistor to move the right half plane zero introduced by the capacitor to the left half plane to ensure stability; The replica resistor comprises a third resistor, one end of which is grounded and the other end of which is connected to the first capacitor, the drain of the third PMOS tube and the gate of the third NMOS tube; The resistance of this resistor is the same as that of the feedback resistor, and is used to generate a replica current in the current compensation circuit to ensure that the compensation current is the same as the current loss caused by the feedback resistor; The operational amplifier comprises a first NMOS tube, a second NMOS tube, a third NMOS tube, a fourth NMOS tube, a first PMOS tube, a second PMOS tube, a third PMOS tube, and a fourth PMOS tube, wherein the gates of the first NMOS tube and the second NMOS tube are both connected to the drain of the first NMOS tube and to a bias current source, the sources of the first NMOS tube and the second NMOS tube are both grounded, the drain of the second NMOS tube is connected to the sources of the third NMOS tube and the fourth NMOS tube; the gate of the third NMOS tube is connected to one end of the third resistor, and the drain is connected to the drain and gate of the first PMOS tube and the gate of the second PMOS tube; the gate of the fourth NMOS tube is connected to one end of the first resistor and the drain of the fourth PMOS tube, and the drain is connected to the drain of the second PMOS tube, the gate of the third PMOS tube, the gate of the fourth PMOS tube, and the drain of the fifth NMOS tube; the sources of the first PMOS tube, the second PMOS tube, the third PMOS tube, and the fourth PMOS tube are all connected to a power supply; The Miller compensation circuit includes a fifth NMOS tube and a first capacitor, wherein the source of the fifth NMOS tube is connected to the other end of the first capacitor, and the gate is connected to a power supply.

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