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Step-down DC-DC converter controlled with fixed on time

A fixed on-time, DC-DC technology, applied in the direction of output power conversion devices, control/regulation systems, instruments, etc., can solve the problems of increased output voltage ripple and difficulty in ensuring system stability, so as to avoid imbalance , easy on-chip integration, and improved stability

Active Publication Date: 2018-09-07
西安航天民芯科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This control method has the following disadvantages: 1) The output capacitor must use an output capacitor with a large equivalent series resistance, and this capacitor leads to an increase in the ripple of the output voltage
It is difficult to ensure the stability of the system by using an output capacitor with a small equivalent series resistance (such as a ceramic capacitor); 2) The valley value of the feedback voltage is adjusted to be equal to the reference voltage, so that the output voltage has a DC offset

Method used

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  • Step-down DC-DC converter controlled with fixed on time
  • Step-down DC-DC converter controlled with fixed on time
  • Step-down DC-DC converter controlled with fixed on time

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specific Embodiment

[0053] refer to Figure 4 , The valley voltage detection circuit of the present invention includes seven PMOS transistors, three NMOS transistors, one resistor, one capacitor, and one diode.

[0054] PMOS tube M 1 —M 5 , whose gates are connected to form a current mirror structure. PMOS tube M 1 The gate and drain are connected and connected to the current source I 1 connected. PMOS tube M 4 The drain of the PMOS transistor M 5 The source is connected in order to generate a small current.

[0055] The valley voltage detection circuit includes a two-stage amplifier, and the first stage amplifier includes a PMOS transistor M 2 , PMOS tube M 6 , PMOS tube M 7 , NMOS tube M 8 , NMOS tube M 9 . Among them, the PMOS transistor M 6 and PMOS tube M 7 Constitute the input differential pair structure, PMOS tube M 6 gate with V RI Connected, PMOS tube M 7 gate with V RI(VY) connected. PMOS tube M 6 The source and PMOS tube M 7 The source is connected to the PMOS tra...

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Abstract

The invention discloses a step-down DC-DC converter controlled with fixed on time, and mainly aims to solve the technical problems of poor system stability and direct-current offset of output voltageduring use of an output capacitor with low equivalent series resistance in the existing fixed-on-time control manner. According to the technical scheme, the step-down DC-DC converter comprises a powerlevel, an analog inductive current generating circuit, a valley point voltage detecting circuit, a signal superposition circuit, a PWM (Pulse-Width Modulation) comparator, a fixed on time generatingcircuit and a driving and logical control circuit, wherein the analog inductive current generating circuit is used for generating a ripple signal of inductive current, and inputting the ripple signalinto the valley point voltage detecting circuit to detect a valley point signal; and the signal superposition circuit is used for generating an inductive current ripple signal of which the ripple value is zero, and superposing with a feedback signal of the output voltage to generate a comparison signal of the PWM comparator. In the scheme, an inductive circuit ripple signal is generated by a phasesignal, so that an extra port is not added in a chip. Moreover, the step-down DC-DC converter is suitable for output capacitors of any type.

Description

technical field [0001] The invention relates to the technical field of electronic circuits, in particular to a step-down DC-DC converter controlled by a constant conduction time. Background technique [0002] In the field of power management, low-voltage high-current DC-DC converters are crucial for high-performance processors. DC-DC converters usually use a voltage-mode or current-mode feedback control method to adjust the output voltage. The power supply voltage of today's electronic devices is getting lower and lower, and the power consumption is getting higher and higher. The traditional control method is limited by the loop bandwidth, and it is difficult to meet the requirements of electronic devices for transient response speed and output voltage ripple. A new feedback control method with fixed on-time can solve these problems well. Its principle is to use the control method of comparing the output ripple voltage with the reference voltage to realize the output volta...

Claims

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Application Information

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IPC IPC(8): H02M3/158H02M1/14
CPCH02M1/14H02M3/158
Inventor 马彦昭叶峥杰樊晓桠
Owner 西安航天民芯科技有限公司