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Frequency control circuit suitable for fixed off time control mode boost converter

A fixed off-time, frequency control technology, applied in the direction of DC power input conversion to DC power output, control/regulation systems, instruments, etc., can solve the constraints of application, switching frequency is not fixed, increase the complexity of circuit design and chip area and other problems, to achieve the effect of reliable function, simple circuit structure and good application prospect

Inactive Publication Date: 2013-02-27
FUDAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Each control mode has its own advantages and disadvantages, and each has its own suitable application occasions
[0004] The fixed off-time control mode is also a kind of DC-DC converter control mode. It has the advantages of fast response speed, simple compensation network and no need for slope compensation circuit, but it has a big disadvantage - the switching frequency is not fixed , making the problem of electromagnetic interference (EMI) more serious, which greatly restricts its application
In some design examples, in order to solve this problem, phase-locked loop (PLL) technology is introduced into the control circuit, but it also increases the complexity of circuit design and chip area

Method used

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  • Frequency control circuit suitable for fixed off time control mode boost converter
  • Frequency control circuit suitable for fixed off time control mode boost converter
  • Frequency control circuit suitable for fixed off time control mode boost converter

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Embodiment Construction

[0013] The present invention will be further described below in conjunction with the accompanying drawings.

[0014] Such as figure 1 As shown, the frequency control circuit mentioned in the present invention is composed of an off-time timer and a frequency locking circuit. The off-time timer circuit is composed of amplifiers, comparators, resistors and capacitors, etc. In the inductor current continuous mode (CCM, continuous current mode),

[0015] T off = T s * V in V out ;

[0016] where T s is the switching frequency of the system, V in is the input voltage, V out is the output voltage, T off for a fixed off-time. If T off is designed to be proportional to the input voltage and inversely proportional to the output voltage, K 1 、K 2 is its proportionality coefficien...

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Abstract

The invention belongs to the technical field of integrated circuits, in particular to a switching frequency control circuit for a fixed off time control mode boost DC-DC converter. The circuit consists of an off time timer and a frequency lock circuit, solves the defect that the working frequency changes along with the working condition under the traditional fixed off time control mode, precisely fixes the working frequency on the reference frequency and reduces the electromagnetic interference (EMI). The circuit of the invention has the advantages of simple structure, reliable function and favorable application prospect, is also suitable for DC-DC converters of other types (such as buck type) and the fixed on time control mode.

Description

technical field [0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a circuit suitable for switching frequency control of a step-up DC-DC converter in a fixed off-time control mode. Background technique [0002] DC-DC Converter (DC-DC Converter) is widely used in various electronic systems, especially the inductive-based DC-DC converter, due to its advantages of high efficiency and large output current capability, it is the most widely used. According to the relationship between the input voltage and the output voltage of the converter, it can be divided into buck type (BUCK), boost type (BOOST) and buck-boost type (BUCK-BOOST). [0003] In order to obtain a higher precision output voltage, a closed-loop control of the DC-DC converter is required. The general control methods include voltage mode control, current control mode control and hysteresis control. Among them, the first two kinds of control are an approximate lin...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M3/155
Inventor 程林龙佳倪金华洪志良
Owner FUDAN UNIV