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CN-122001192-A - Constant on-time control circuit and power conversion circuit

CN122001192ACN 122001192 ACN122001192 ACN 122001192ACN-122001192-A

Abstract

The invention discloses a constant on-time control circuit and a power supply conversion circuit, which belong to the technical field of switching power supplies and comprise a first operational amplifier, wherein the output end of the first operational amplifier is connected with the first end of a fourth transistor, the second end of the fourth transistor is connected with the second end of the first transistor, the first end of the second transistor and the first end of a third transistor, the second end of the third resistor is connected with the first end of a third capacitor and the positive end of a first comparator, the second end of the third transistor is connected with the second end of a sixth transistor, the third end of the sixth transistor is connected with the negative end of the first comparator, the first end of the fourth capacitor and the second end of a seventh transistor, the first end of the seventh transistor is connected with the second end of a first inverter, and the output end of the first comparator is connected with the first end of a buck converter. The invention can effectively offset the influence of efficiency, duty ratio and working condition change on the switching frequency, and improves the power supply conversion efficiency and the output voltage stability.

Inventors

  • FENG LUPING
  • FAN PING
  • SONG JIAN
  • YIN LIYONG
  • LI WENGE

Assignees

  • 江苏展芯半导体技术股份有限公司

Dates

Publication Date
20260508
Application Date
20260408

Claims (10)

  1. 1. The constant on-time control circuit is applied to a power supply conversion circuit, and comprises a constant on-time control circuit and a buck converter, and is characterized in that the constant on-time control circuit comprises a second resistor, a first end of the second resistor is connected with an input voltage, a second end of the second resistor is connected with a first end of a fourth resistor and a positive end of a first operational amplifier, a second end of the fourth resistor is grounded, a negative end of the first operational amplifier is connected with a third end of the fourth transistor and a first end of a first resistor, a second end of the first resistor is grounded, an output end of the third operational amplifier is connected with a first end of a fourth transistor, a third end of the fourth transistor is connected with a second end of the first transistor, a first end of the first transistor and a first end of a third transistor, a third end of the first transistor is connected with a third end of the third transistor, a third end of the third transistor is connected with a third end of the third resistor, a third end of the third transistor is connected with a third end of the third transistor, a third end of the third transistor is connected with a third end of the third resistor, and a third end of the third transistor is connected with a third end of the third resistor is connected with a third end of the third transistor, the first end of the seventh transistor is connected with the second end of the first inverter.
  2. 2. The constant on-time control circuit of claim 1, wherein the positive terminal of the first comparator is a compensation voltage, the first comparator outputs a conduction signal with a fixed on-time, and the conduction signal with the fixed on-time is input into the buck converter to control the on-time of the buck converter switching tube.
  3. 3. The constant on-time control circuit of claim 2, wherein the compensation voltage is expressed as: , Wherein, the In order for the actual duty cycle to be the same, For the efficiency under the corresponding working conditions, In order to output the voltage, the voltage is, For the input voltage to be applied to the circuit, For the first reference current, k is a proportionality coefficient, ron is the resistance of the fifth resistor, and R1 is the resistance of the first resistor.
  4. 4. A constant on-time control circuit according to claim 3, wherein the fixed on-time is expressed as: , Wherein, the For the efficiency under the corresponding working conditions, In order to output the voltage, the voltage is, For the input voltage, ron is the resistance of the fifth resistor, and Con is the capacitance of the fourth capacitor.
  5. 5. The constant on-time control circuit according to claim 4, wherein the actual switching frequency of the buck converter is expressed as: , Wherein, the For an actual duty cycle, TON is a fixed on-time, For the efficiency under the corresponding working conditions, In order to output the voltage, the voltage is, For the input voltage, k is a scaling factor, ron is the resistance of the fifth resistor, and Con is the capacitance of the fourth capacitor.
  6. 6. The constant on-time control circuit of claim 1, wherein a first signal is input to a first terminal of the fifth transistor, the sixth transistor, and the first inverter.
  7. 7. The constant on-time control circuit according to claim 6, wherein the first signal is a switching tube pre-stage driving signal generated inside the buck converter for driving upper and lower switching tubes of the buck converter.
  8. 8. The constant on-time control circuit of claim 7, wherein the first transistor, the second transistor, and the third transistor are P-type MOS transistors, wherein first ends of the first transistor, the second transistor, and the third transistor are gates, wherein second ends of the first transistor, the second transistor, and the third transistor are drains, and wherein third ends of the first transistor, the second transistor, and the third transistor are sources.
  9. 9. The constant on-time control circuit of claim 8, wherein the fourth transistor, the fifth transistor, the sixth transistor, and the seventh transistor are N-type MOS transistors, wherein first ends of the fourth transistor, the fifth transistor, the sixth transistor, and the seventh transistor are gates, wherein second ends of the fourth transistor, the fifth transistor, the sixth transistor, and the seventh transistor are drains, and wherein third ends of the fourth transistor, the fifth transistor, the sixth transistor, and the seventh transistor are sources.
  10. 10. A power supply conversion circuit is characterized in that a buck converter finishes stable power conversion and load power supply output according to a conduction signal output by a constant conduction time control circuit, and a boost converter is also suitable for the power supply conversion circuit.

Description

Constant on-time control circuit and power conversion circuit Technical Field The present invention relates to the field of switching power supply technologies, and in particular, to a constant on-time control circuit and a power conversion circuit. Background A constant on-time (COT) control circuit is a control circuit in which the on-time is kept constant and the off-time is dynamically adjustable in a switching power supply. Compared with the traditional constant frequency control circuit, the circuit can quickly adjust the inductance current by changing the turn-off time when the load is in transient variation, and has more excellent transient response performance, so that the circuit is widely applied to power supply systems of digital chips such as a Central Processing Unit (CPU), a Graphic Processing Unit (GPU), a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC) and the like. Although the traditional constant on-time control circuit has high response speed, the switching frequency of the circuit is greatly changed along with the load and input and output conditions, so that the difficulty of inductor type selection is increased, and the electromagnetic interference processing of the system is more complex. In order to improve the frequency fluctuation problem, the prior art often adopts an adaptive constant on-time control circuit, and realizes the relative stability of the switching frequency while retaining the rapid response characteristic. However, the existing self-adaptive constant on-time control circuit still has obvious defects that the switching frequency is easily influenced by the actual working conditions such as power supply conversion efficiency, driving conditions of a switching tube, working temperature and the like. When the load is changed slightly, the driving voltage is changed or the ambient temperature fluctuates, the conversion efficiency of the system is changed, so that the switching frequency is obviously shifted, the switching frequency is difficult to keep constant under complex working conditions, adverse effects on the aspects of inductance parameter matching, electromagnetic interference suppression and the like are still brought, and the power supply application requirements of high precision and high stability cannot be met. Disclosure of Invention The invention aims to provide a constant on-time control circuit and a power supply conversion circuit. In order to achieve the above purpose, the technical scheme of the invention is as follows: The constant on-time control circuit is applied to a power supply conversion circuit, and the power supply conversion circuit comprises a constant on-time control circuit and a buck converter; the constant on-time control circuit comprises a second resistor, wherein the first end of the second resistor is connected with an input voltage, the second end of the second resistor is connected with the first end of a fourth resistor and the positive end of a first operational amplifier, the second end of the fourth resistor is grounded, the negative end of the first operational amplifier is connected with the third end of the fourth transistor and the first end of the first resistor, the second end of the first resistor is grounded, the output end of the first operational amplifier is connected with the first end of the fourth transistor, the second end of the fourth transistor is connected with the second end of the first transistor, the first end of the second transistor and the first end of the third transistor, the third end of the first transistor is connected with the third end of the second transistor and the third end of the third transistor, the second end of the second transistor is connected with the second end of the fifth transistor, the third end of the fifth transistor is connected with the first end of the fifth resistor and the first end of the third resistor, the second end of the fifth resistor is grounded, the second end of the third resistor is connected with the first end of the third capacitor and the positive end of the first comparator, the second end of the third capacitor is grounded, the second end of the third transistor is connected with the second end of the sixth transistor, the third end of the sixth transistor is connected with the negative end of the first comparator, the first end of the fourth capacitor and the second end of the seventh transistor, the second end of the fourth capacitor is connected with the third end of the seventh transistor and the ground, the first end of the seventh transistor is connected with the second end of the first inverter. Further, the positive end of the first comparator is a compensation voltage, the first comparator outputs a conduction signal with fixed conduction time, the conduction signal with fixed conduction time is input into the buck converter, and the conduction time of the buck converter switching tube is controlled.