Control circuit in DCDC converter

Abstract

The utility model discloses a control circuit in a DCDC converter, belongs to the technical field of electronic circuits, and solves the problem of generating a control signal to a BUCK type DC-DC voltage stabilizer. Comprising a VOUT selection circuit module, and the VOUT selection circuit module receives output voltage of the BUCK converter and outputs a reference voltage value after processing the output voltage; the charging circuit module is used for timing after receiving the charging current and the square wave signal, and outputting a charging voltage value within the timing time; and two input ends of the comparator module are respectively coupled with the VOUT selection circuit module and the charging circuit module. According to the utility model, the output voltage of the BUCK converter can be output after being processed through the VOUT selection circuit module to serve as a reference voltage value of the comparator, the charging circuit module is used for timing and enables the comparator module to generate a control signal TON, and an upper power tube is kept to be opened within the timing, so that the BUCK converter is charged. And the control signal TON is output and is connected to a post-stage logic control circuit to regulate and control the working state of the power tube.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, in particular to a control circuit in a DCDC converter. Background Art

[0002] With the development of semiconductor technology, portable electronic devices such as smart phones and watches have developed rapidly, and their popularity has continued to increase. Today, these devices have become an indispensable part of people's daily lives. For this reason, people have higher requirements for indicators such as weight, volume and battery life of electronic devices. Therefore, it is critical to improve the performance of power chips without increasing the size and weight of the equipment. This demand not only requires the power chip to have higher working efficiency, but also includes lower power consumption, lower cost, higher integration and higher stability. Therefore, the research on high-efficiency, miniaturized and high-frequency DC-DC switching power supply chips is of great value. At present, my country is also vigorously promoting the localization of DC-DC converters. Domestic DC-DC converters can not only meet the needs of the domestic market, but also greatly promote the high-quality development of the electronics industry.

[0003] In a BUCK type DC-DC regulator, in order for the output voltage to be stabilized to the original value through circuit regulation when the input voltage or load jumps, we need to introduce feedback in the entire system. According to the different feedback information, we can divide the control mode of the BUCK type DC-DC regulator into two types: the first is to sample the output voltage signal and feed it back to the control loop, which we call the voltage mode control mode. Because it only has a single voltage feedback loop, we also call it a single loop control mode; the second is to sample the inductor current on the basis of the voltage mode and feed it back to the control loop at the same time. We call it the current mode control mode. Because it has two control loops, we also call it a dual loop control mode. The control mode of the BUCK regulator has always been a hot topic in our research. After decades of development, its control mode has been greatly improved on the basis of the traditional voltage mode and current mode, and constant on-time control mode and current mode constant on-time control mode have emerged.

[0004] The voltage-mode control method responds slowly to changes in input voltage and inductor current, and the conjugate poles introduced by the LC filter at the output end complicate the compensation network. The current-mode constant on-time control regulator relies on adjusting the off-time of the switching power tube to maintain output voltage stability, and its on-time remains constant. It is a commonly used frequency conversion technology.

[0005] The dual-loop control method of the current mode can directly respond to changes in the input voltage and inductor current, which speeds up the transient response of the system to a certain extent. When performing stability analysis, the inductor can be included in the modulation module, which eliminates the conjugate pole caused by the inductor to a certain extent. In addition, the current mode control method also provides a cycle-by-cycle current limiting function.

[0006] The basic working principle of the BUCK type DC-DC regulator with valley current mode control with adaptive technology is as follows: the error amplifier detects small changes in the output voltage and amplifies it to generate a control signal, which can determine the valley current limit of the inductor. The sampling circuit samples the inductor current. When the sampled current is equal to the valley current limit, the switching power tube is turned on, and the trigger circuit starts timing to generate a fixed conduction time. When the timing ends, the switching power tube is disconnected. After the dead time, the rectifier tube is turned on, and the inductor current decreases until it reaches the valley current limit, and the next cycle starts.

[0007] A control circuit in a DCDC converter is now proposed to generate a control signal for a buck type DC-DC regulator.

[0008] Therefore, a control circuit in a DCDC converter is proposed to solve or alleviate the above problems. Utility Model Content

[0009] The utility model aims to solve the shortcomings in the prior art and proposes a control circuit in a DCDC converter.

[0010] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0011] A control circuit in a DCDC converter, comprising:

[0012] A VOUT selection circuit module, wherein the VOUT selection circuit module receives the output voltage of the BUCK converter and outputs a reference voltage value after processing;

[0013] A charging circuit module, which receives the charging current and the square wave signal and then starts timing, and outputs a charging voltage value within the timing time;

[0014] A comparator module, wherein two input terminals of the comparator module are respectively coupled to the VOUT selection circuit module and the charging circuit module. The comparator module responds to the reference voltage value and the charging voltage value and outputs a control signal after comparison.

[0015] Preferably, the VOUT selection circuit module includes a source follower circuit, a dual-end input single-end output operational amplifier circuit, and a common source operational amplifier circuit.

[0016] Preferably, the source follower circuit, the dual-end input single-end output operational amplifier circuit, and the common-source operational amplifier circuit all include a plurality of MOS tubes.

[0017] Preferably, the charging circuit module includes a resistor and a plurality of MOS tubes.

[0018] Preferably, the comparator module comprises a first-stage operational amplifier circuit, a second-stage operational amplifier circuit, and a third-stage operational amplifier circuit which are connected in sequence.

[0019] Preferably, the first-stage operational amplifier circuit, the second-stage operational amplifier circuit, and the third-stage operational amplifier circuit all include a plurality of MOS tubes.

[0020] Preferably, the comparator module further includes three inverters, and the three inverters are sequentially coupled to the output end of the third-stage operational amplifier circuit.

[0021] The utility model has the following beneficial effects:

[0022] The utility model can process and output the output voltage of the BUCK converter through the VOUT selection circuit module as a reference voltage value of the comparator. The charging circuit module is used to time and make the comparator module generate a control signal TON. During this timing, the upper power tube is kept turned on. The control signal TON is output and connected to the logic control circuit of the subsequent stage to adjust the working state of the power tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural block diagram of the utility model;

[0024] Figure 2 It is the wiring diagram of the VOUT selection circuit module in the utility model;

[0025] Figure 3 It is the wiring diagram of the charging circuit module in the utility model;

[0026] Figure 4 This is the wiring diagram of the comparator module in the utility model. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0028] A control circuit in a DCDC converter, such as Figure 1 As shown, it includes a VOUT selection circuit module, a charging circuit module, and a comparator module.

[0029] The VOUT selection circuit module receives the output voltage of the BUCK converter and outputs a reference voltage value after processing. The charging circuit module receives the charging current and the square wave signal and then counts, and outputs the charging voltage value within the timing time. The two input ends of the comparator module are respectively coupled to the VOUT selection circuit module and the charging circuit module. The comparator module responds to the reference voltage value and the charging voltage value and outputs a control signal after comparison.

[0030] The VOUT selection circuit module includes a source follower circuit, a dual-end input single-end output operational amplifier circuit, and a common source operational amplifier circuit. The source follower circuit, the dual-end input single-end output operational amplifier circuit, and the common source operational amplifier circuit all include a number of MOS tubes, specifically, Figure 2 As shown, the input of the circuit is 1 / 2VOUT, which is the output voltage VOUT of the BUCK converter divided by half by resistors R1 and R2. VBG1 and VBG2 are the upper and lower reference voltages of the circuit, respectively, which are designed to be 0.3V and 2.4V.

[0031] VO is the output and serves as the input of the comparator module.

[0032] The VOUT selection circuit structure is a three-stage operational amplifier cascade structure. The first stage is a source follower circuit, consisting of M1, M2, M3 and M14, where M1, M2 and M3 are selection input terminals. The second stage is a dual-end input single-end output operational amplifier circuit, consisting of M4, M5, M6, M7 and M12, where M4 and M5 are selection input terminals. The third stage is a common source operational amplifier circuit, consisting of M8, M19 and M13.

[0033] Figure 2 Each current source provides bias current for different branches respectively, and its working process is as follows: when the input voltage of the circuit is less than VBG1, the voltage values ​​of each input voltage divider, VBG1, and VBG2 are raised by a gate-source voltage of M1, M2, and M3 through the source follower circuit. Because the input value of the circuit is low, after comparison, the op amp selects M4 as the input terminal of the second-stage op amp, and the output voltage VO of the circuit is 0.3V; when the input voltage of the circuit is greater than VBG1 and less than VBG2, the input of the circuit is between the upper and lower limit reference voltages, and the op amp selects M5 as the input terminal of the dual-end input single-end output op amp circuit. Through the joint action of the common source op amp circuit and the output feedback tube M14, the module output voltage VO changes linearly with VOUT; when the input voltage of the circuit is greater than VBG2, the op amp selects M4 as the input terminal of the dual-end input single-end output op amp circuit, but the output voltage is limited to 2.4V at this time.

[0034] The charging circuit module includes a resistor and several MOS tubes, specifically, Figure 3As shown, ION is the charging current, VCLK is a square wave signal with a certain frequency, and the resistor R is a resistor with a limited current function. When VCLK is at a low level, MOS tubes M1 and 2 are turned on, and the capacitor discharges through M1 and M2. The voltage on capacitor C is zero. At this time, the upper power tube of the BUCK converter is turned off and the lower power tube is turned on. When the lower power tube is turned off, VCLK becomes a high level, MOS tubes M1 and 2 are turned off, and the current ION starts to charge capacitor C. The VC voltage gradually rises. When the voltage on capacitor C reaches VO, the comparator flips, and the TON control signal outputs a low level, which controls the upper power tube to turn off. At the same time, VCLK becomes a low level again, and the circuit repeats the above process continuously.

[0035] The comparator module includes a first-stage operational amplifier circuit, a second-stage operational amplifier circuit, a third-stage operational amplifier circuit, and three inverters connected in sequence. The first-stage operational amplifier circuit, the second-stage operational amplifier circuit, and the third-stage operational amplifier circuit all include a plurality of MOS tubes. The three inverters are sequentially coupled to the output end of the third-stage operational amplifier circuit. More specifically, the comparator module is as follows Figure 4 As shown in the figure, this module is a comparator composed of three-stage operational amplifiers. I BIAS is the bias of the entire circuit, VC and VO are the output values ​​of the VOUT selection circuit module and the charging circuit module respectively. The comparator compares the VC and VO voltages to obtain the core control signal TON. The first-stage operational amplifier circuit is composed of M1, M2, R1, R2 and M12, wherein M1 and M2 are the first-stage input terminals, R1 and R2 are the loads of the operational amplifier, and M12 provides bias; the second-stage operational amplifier circuit is composed of M5, M6, M7, M8 and M11, wherein the input of the second-stage operational amplifier is the output value of the first-stage operational amplifier, M5 and M6 are the second-stage input terminals, M7 and M8 are the loads of the operational amplifier, and M11 provides bias for the second-stage operational amplifier; the third-stage operational amplifier circuit is composed of M9 and M10, forming a common-source amplifier, the input of the third-stage operational amplifier circuit is the output of the second-stage operational amplifier circuit, M9 is the amplifier tube, and M10 is used as a load; finally, the output of the three-stage operational amplifier is shaped by three inverters to obtain the control signal TON.

[0036] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes within the technical scope disclosed by the present invention according to the technical scheme and the utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A control circuit in a DCDC converter, characterized in that: include: A VOUT selection circuit module, wherein the VOUT selection circuit module receives the output voltage of the BUCK converter and outputs a reference voltage value after processing; A charging circuit module, which receives the charging current and the square wave signal and then starts timing, and outputs a charging voltage value within the timing time; A comparator module, wherein two input terminals of the comparator module are respectively coupled to the VOUT selection circuit module and the charging circuit module. The comparator module responds to the reference voltage value and the charging voltage value and outputs a control signal after comparison.

2. The control circuit in a DCDC converter according to claim 1, characterized in that: The VOUT selection circuit module includes a source follower circuit, a dual-end input single-end output operational amplifier circuit, and a common source operational amplifier circuit.

3. The control circuit in a DCDC converter according to claim 2, characterized in that: The source follower circuit, the dual-end input single-end output operational amplifier circuit, and the common-source operational amplifier circuit all include a plurality of MOS tubes.

4. The control circuit in a DCDC converter according to claim 1, characterized in that: The charging circuit module includes a resistor and a plurality of MOS tubes.

5. The control circuit in a DCDC converter according to claim 1, characterized in that: The comparator module includes a first-stage operational amplifier circuit, a second-stage operational amplifier circuit, and a third-stage operational amplifier circuit which are connected in sequence.

6. The control circuit in a DCDC converter according to claim 5, characterized in that: The first-stage operational amplifier circuit, the second-stage operational amplifier circuit, and the third-stage operational amplifier circuit all include a plurality of MOS tubes.

7. The control circuit in a DCDC converter according to claim 5, characterized in that: The comparator module further includes three inverters, and the three inverters are sequentially coupled to the output end of the third-stage operational amplifier circuit.

Images