CN209913707U - Self-adaptive turn-off time timer with adjustable switching frequency - Google Patents
Self-adaptive turn-off time timer with adjustable switching frequency Download PDFInfo
- Publication number
- CN209913707U CN209913707U CN201920573023.XU CN201920573023U CN209913707U CN 209913707 U CN209913707 U CN 209913707U CN 201920573023 U CN201920573023 U CN 201920573023U CN 209913707 U CN209913707 U CN 209913707U
- Authority
- CN
- China
- Prior art keywords
- voltage
- circuit
- switching frequency
- comparator
- input
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Landscapes
- Dc-Dc Converters (AREA)
Abstract
The utility model discloses a self-adaptive turn-off time timer with adjustable switching frequency, which comprises an on-chip LDO circuit, a resistor string voltage-dividing circuit, a capacitor charging and discharging circuit, a two-stage filter circuit, a comparator circuit and an off-chip switching frequency adjusting resistor; the input voltage is respectively connected to the input ends of the LDO circuit and the resistor string voltage division circuit; the output end of the LDO circuit is connected to the positive input end of the comparator; the output end of the resistor string voltage division circuit is connected with the input of the two-stage filter, and the output of the filter is connected with the negative input end of the comparator; SW connecting piece external switch frequency adjusting resistor RfreqAnd connected to the source of the PMOS; grid voltage of switch tubeLS _ GA is connected with the gates of the NMOS and PMOS switches, and a capacitor CcThe upper plate of which is connected with the positive input end of the comparator. The utility model discloses realize that on-chip switching frequency is invariable, off-chip switching frequency is adjustable, improved electromagnetic compatibility.
Description
Technical Field
The utility model relates to a switching frequency adjustable self-adaptation turn-off time timer circuit under COT mode control to DC-DC type that steps up (boost type) converter.
Background
With the development of scientific technology, people have increasingly greater demands on electronic products and increasingly strict performance requirements on the electronic products, and the switching power converter, as the heart of the electronic product, is widely applied to the fields of industry, military, commerce and the like, and when the switching power converter supplies power to a high-performance processor, the whole system has the trends of lower and lower work, higher and higher integration level, smaller and smaller volume and more frequent transient conversion. The DC-DC converter with the self-adaptive switching frequency has extremely high theoretical and commercial value.
The switch type power converter realizes the functions of boosting, reducing or boosting and reducing voltage by utilizing the energy conversion between the magnetic energy storage element inductor and the electric energy storage element capacitor so as to achieve the function of converting power. Different topologies can be formed according to the transformation of the position of the inductor, the capacitor and the switching tube, including boost type (boost type), buck type (buck type) and boost-buck type (buck-boost type).
In the process of researching a switching power converter, the on-time of a switching tube (the off-time of a synchronous tube) is often recorded as TonThe time of the switch tube being turned off (the time of the synchronous tube being turned on) is recorded as ToffIn Continuous Conduction Mode (CCM), the switching period of the converter is equal to Ton+ToffIs marked as TswThe switching frequency of the converter being equal to 1/TswIs denoted by fsw. For a DC-DC boost converter, TonThe time switch tube is switched on (the synchronous tube is switched off), and the voltage on the inductor is equal to Vin-0, when the inductor current rises; t isoffThe time switch tube is turned off (the synchronous tube is turned on), and the voltage on the inductor is equal to Vin-VoutAt this time VoutGreater than VinThe inductor current drops, the amount by which it rises when it reaches steady state equals the amount of the drop, and the converter enters the next switching cycle.
During the operation of the converter, some conditions may cause the inductive current to drop to 0, and the converter operates in Discontinuous conduction mode (Discontinuous conductor)ionMode, DCM), when T isoffAfter the moment, in order to prevent the inductive current from flowing backwards to reduce the efficiency of the converter or damage elements, zero-crossing detection is usually introduced to turn off the synchronous tube, the switching tube and the synchronous tube are turned off simultaneously, the turn-off time is recorded as T, and as the switching tube and the synchronous tube are turned off simultaneously, the SW node can be in a high-resistance state and is very easily disturbed, so that the SW node can oscillate for a period of time under the action of the inductor until the switching period is finished.
The Modulation mode of the switching power converter can be divided into a Pulse Width Modulation (PWM) mode and a Pulse Frequency Modulation (PFM) mode, wherein the PWM mode means that the switching Frequency is kept unchanged, and the control of the output voltage is realized by changing the Pulse Width of the driving signal of the switching tube; the PFM mode is a mode in which the pulse width is kept constant and the output voltage is controlled by adjusting the switching frequency, and the conventional COT mode is one of the PFM modes because only the off-time balance is kept and the whole switching period is not limited.
The control mode of the early switching power converter is divided into voltage mode control and current mode control, the voltage mode control compares the output voltage as a feedback signal with a ramp signal generated by an oscillator, and outputs a driving signal to control a switching tube of the converter, the current mode control comprises two feedback loops, the voltage feedback loop outputs the output voltage signal and a reference signal through an error amplifier, and the output error amplification signal is superposed with an inductance sampling current signal of the current feedback loop to drive the switching tube of the converter together, so as to realize the control of the output voltage. In recent years, a COT control method based on ripple control is widely used, and is very suitable for being applied to a power supply scheme of a high-speed processor due to the characteristics that an error amplifier is not needed and a loop is simple. Scholars control T in COToffAn improvement is made to obtain the ACOT control mode, i.e., adaptive constant off-time control.
In the application to the chip with the strict requirement on the transient response speed, the ACOT control mode is the first choice, but the problem of electromagnetic interference is also urgently needed to be solved.
SUMMERY OF THE UTILITY MODEL
In order to solve the problem that switching frequency is invariable, the electromagnetic interference characteristic is relatively poor under traditional COT control mode, the utility model provides a switching frequency adjustable self-adaptation turn-off time timer circuit through introducing off-chip switching frequency adjusting resistance and with output voltage and input voltage and turn-off time ToffIn connection with the constant on-chip switching frequency and the adjustable off-chip switching frequency, the electromagnetic interference characteristic of the COT mode is improved.
The utility model discloses a realize through following technical scheme:
a self-adaptive turn-off time timer circuit with adjustable switching frequency mainly comprises an on-chip LDO circuit, a resistor string voltage division circuit, a capacitor charging and discharging circuit, a two-stage filter circuit, a comparator circuit and an off-chip switching frequency adjusting resistor; the input voltage is respectively connected to the input ends of the LDO circuit and the resistor string voltage division circuit; the output end of the LDO circuit is connected to the positive input end of the comparator; the output end of the resistor string voltage division circuit is connected with the input end of the two-stage filter, and the output end of the filter is connected with the negative input end of the comparator; SW connecting piece external switch frequency adjusting resistor RfreqAnd connected to the source of the PMOS; the gate voltage LS _ GA of the switching tube is connected with the gates of the NMOS and PMOS switches, and the capacitor CcThe upper plate of which is connected with the positive input end of the comparator.
Furthermore, the LDO circuit in the chip is composed of a capacitor and a Zener diode, and the capacitor is charged through input voltage, so that the Zener diode connected with the capacitor in parallel reaches stable breakdown voltage, and the power supply voltage of the timer circuit is generated.
Further, the resistor string voltage division circuit inputs the voltage VinAnd dividing voltage according to ohm's law to obtain voltage proportional to the input voltage, and using the obtained voltage proportional to the input voltage as the input of the two-stage filtering.
Further, the two-stage filter circuit is used for filtering the voltage proportional to the input voltageFiltering twice to remove burr and noise to obtain DC voltage kV similar to that in direct proportion to input voltageinK is the voltage division coefficient of the resistor string, and the obtained kVinAs the negative input to the comparator.
Further, the capacitor charging and discharging circuit utilizes the output voltage VoutFlows through the switching frequency adjusting resistor RfreqAfter current IchgCharging is carried out, and the charging time is the turn-off time ToffAnd a charging voltage VcAs the positive input of the comparator; when the switch tube is switched on and the synchronous tube is switched off, the voltage on the capacitor is discharged through the NMOS tube and the PMOS tube which are controlled by the driving voltage of the switch tube, so that the timing of the next switching-off time is started.
Further, the comparator circuit compares VcAnd kVinMaking a comparison when VcGreater than kVinAnd when the DC-DC boost converter is used, the comparator outputs a set signal, and the set signal drives the switching tube and the synchronous tube through the rear-stage trigger and the logic signal to realize the function of the DC-DC boost converter.
Further, the off-chip switching frequency adjusting resistor adjusts the output voltage VoutCurrent I charging the capacitorchgTo change the charging time ToffWhen V is adaptive due to the self-adaptation of the circuitinAnd VoutWhen not changed, ToffWhen the change occurs, the switching frequency of the whole DC-DC boost converter can be changed, and the resistance value of the switch resistor can be selected according to the user requirement and the application requirement.
Compared with the prior art, the beneficial effects of the utility model are that: by introducing an off-chip switching frequency regulating resistor and combining the output voltage and the input voltage with the off-time ToffIn connection with the constant on-chip switching frequency and the adjustable off-chip switching frequency, the on-chip switching frequency is constant, and the switching frequency constancy and the electromagnetic interference characteristic under the COT control mode are improved.
Drawings
FIG. 1 is a COT architecture DC-DC boost converter topology model;
FIG. 2 is a circuit of an adaptive turn-off timer with adjustable switching frequency;
FIG. 3. output 9v time timer delay;
FIG. 4. output 12v time timer delay;
FIG. 5.ToffAnd VoutA relation curve;
FIG. 6.ToffAnd VinA relation curve;
FIG. 7.VinIs 3.5V, VoutIs 9v, RfreqA converter switching period of 250k Ω;
FIG. 8.VinIs 3.5V, VoutIs 9v, RfreqA converter switching period of 135k omega;
Detailed Description
In order to facilitate understanding of the technical solution of the present invention, the present invention will be further explained with reference to the accompanying drawings and examples.
Example 1
As shown in fig. 1, a circuit diagram of an adaptive off-time timer with adjustable switching frequency mainly comprises an on-chip LDO circuit, a resistor string voltage-dividing circuit, a capacitor charging and discharging circuit, a two-stage filter circuit, a comparator circuit, and an off-chip switching frequency adjusting resistor. The input voltage is respectively connected to the input ends of the LDO circuit and the resistor string voltage division circuit; the output end of the LDO circuit is connected to the positive input end of the comparator; the output end of the resistor string voltage division circuit is connected with the input end of the two-stage filter, and the output end of the filter is connected with the negative input end of the comparator; SW connecting piece external switch frequency adjusting resistor RfreqAnd connected to the source of the PMOS; the gate voltage LS _ GA of the switching tube is connected with the gates of the NMOS and PMOS switches, and the capacitor CcThe upper plate of which is connected with the positive input end of the comparator.
Specifically, the LDO circuit in the chip consists of an LDO circuit consisting of a capacitor and a Zener diode, and passes through VinAnd IbiasCharging a capacitor therein to stabilize breakdown voltage of a Zener diode connected in parallel with the capacitor, thereby generating a supply voltage V of the timer circuitddAnd is connected to a comparator COMP as the power supply voltage of the comparator; resistor string voltage division circuit ReqAnd RkComposition ReqFor the series equivalence of a plurality of resistors, input voltage VinDividing voltage according to ohm's law to obtain voltage proportional to input voltage, and connecting its output to R1、C1And R2、C2A two-stage filter is formed; the capacitor charging and discharging circuit utilizes the output voltage VoutFlows through the switching frequency adjusting resistor RfreqAfter current IchgCharging is carried out, and the charging time is the turn-off time ToffAnd a charging voltage VcAs the positive input of the comparator; when the switch tube is switched on and the synchronous tube is switched off, the voltage on the capacitor is discharged through the NMOS tube and the PMOS tube which are controlled by the driving voltage of the switch tube so as to start the timing of the next switching-off time; r1、C1、R2、C2The formed two-stage filter filters burrs and noise, and outputs VinDirect voltage kVin(ii) a Wherein k is the voltage division coefficient of the resistor string, and the obtained kVinAs negative phase input to comparator COMP, the result of comparator passes through VcompAn end output which is used as an input of an S end of the SR trigger; SW connecting piece external switch frequency adjusting resistor RfreqAnd connected to the source of PMOS to generate current for charging the charge-discharge capacitor, and the gate voltage LS _ GA of the switching tube is connected to the gates of NMOS and PMOS switches to determine whether the charge-discharge capacitor is in charge or discharge stage and the capacitor CcThe upper polar plate is connected with the positive input end of a comparator COMP; the off-chip switching frequency adjusting resistor adjusts the output voltage VoutCurrent I charging the capacitorchgTo change the charging time ToffWhen V is adaptive due to the self-adaptation of the circuitinAnd VoutWhen not changed, ToffWhen the change occurs, the switching frequency of the whole DC-DC boost converter can be changed, and the resistance value of the switch resistor can be selected according to the user requirement and the application requirement.
From the basic knowledge of a DC-DC boost converter, the switching frequency f of the converter can be derivedswAnd VoutAnd ToffIs inversely proportional to VinProportional, i.e., the switching frequency is not constant, to make the switching frequency constant,need to let ToffAnd VinIs in direct proportion to VoffIn inverse proportion, V is a constant on timer in the conventional buck COT converter (requiring a constant on timer)outAnd VinIs small, so that an accurate following V is requiredinThe varying current charges the capacitor to ensure VinAnd TonIn inverse proportion, a unit gain buffer is often adopted, and the method has high requirements on the precision of the switching frequency in the chip, needs a complex frequency correction circuit and improves the cost and the difficulty of chip design.
In this embodiment, the output voltage V isoutAnd an input voltage VinA large difference of (i.e. V)outAnd the voltage V after the capacitor is chargedcIs very large and therefore can be used as Vout-VcCurrent I obtained by dividing by off-chip switching frequency adjusting resistorchgIs approximately proportional to VoutBecause the switching frequency adjusting resistor is arranged outside the chip, a user can accurately determine the switching frequency by adjusting the resistance value of the switching resistor, the cost is saved, the complexity of the circuit is reduced, and the relation between the off-chip switching resistor and the switching frequency of the converter is RfreqAnd Cc、k、fswIs inversely proportional to the product of RfreqFor off-chip switching frequency regulating resistors, k is the voltage division coefficient of the resistor string, fswIs the converter switching frequency.
As shown in fig. 2, the topology model of the DC-DC boost converter with COT architecture is shown, where Off _ Timer is a turn-Off Timer module, and when the system reaches a steady state, when a switching period starts, the switching tube is turned Off, and the switching tube drives a voltage VLS_GAWhen the voltage is low, the NMOS transistor is turned off, the PMOS transistor is turned on, and V is turned off in FIG. 1swI.e. VoutAdjusting the resistance R by switching frequencyfreqGenerating a charging current IchgIs a capacitor CcCharging when voltage VCUp to kVinWhen the high-level trigger is triggered, the comparator outputs high-level pulse, the S end of the SR trigger is set, the trigger outputs high level, and the switch tube drives the voltage VLS_GAWhen the voltage is high level, the switch tube is turned on, the NMOS tube is turned on, the PMOS tube is turned off, the charges on the capacitor are discharged to the ground, the circuit and the like through the NMOS tubeWaiting for the next even cycle.
Example 2
As can be seen from fig. 3 and 4 based on embodiment 1, when the output voltage is 9V and 12V, the delay time of the comparator is 21ns and 19ns respectively, and the response speed of the comparator is good. As can be seen from FIG. 5, the turn-off time T is in the range of 4.5V to 12.5V of the output voltageoffAnd VoutIn inverse proportion, it can be seen from FIG. 6 that T is in the range of 2.5V to 12.5V of input voltageonAnd VinApproximately satisfying a direct proportional relationship. It can be seen from FIGS. 7 and 8 that V is the positioninIs 3.5V, VoutAt 9v, the resistance R is adjusted by changing the off-chip frequencyfreqCan realize the adjustment of switching frequency when R isfreqAt 250K omega, the switching period is 1.671us, namely the switching frequency is 598 KHz; rfreqFor 135K omega, the switching cycle is 1.012us, and switching frequency is 988KHz promptly, satisfies the off-chip frequency that derives in the above-mentioned relation between the switching frequency of adjusting resistance and converter, consequently, the utility model discloses can realize established function, and the functional performance is good.
The above description is a specific embodiment of the present invention, and is not intended to limit the concept and scope of the present invention, and various modifications and equivalent changes made on this basis shall fall within the protection scope of the present invention.
Claims (7)
1. An adaptive turn-off time timer with adjustable switching frequency is characterized in that: the on-chip LDO circuit, the resistor string voltage division circuit, the capacitor charging and discharging circuit, the two-stage filter circuit, the comparator circuit and the off-chip switching frequency adjusting resistor are included; the input voltage is respectively connected to the input ends of the LDO circuit and the resistor string voltage division circuit; the output end of the LDO circuit is connected to the positive input end of the comparator; the output end of the resistor string voltage division circuit is connected with the input end of the two-stage filter, and the output end of the filter is connected with the negative input end of the comparator; SW connecting piece external switch frequency adjusting resistor RfreqAnd connected to the source of the PMOS; the gate voltage LS _ GA of the switching tube is connected with the gates of the NMOS and PMOS switches, and the capacitor CcThe upper plate of which is connected with the positive input end of the comparator.
2. The adaptive off-time timer with adjustable switching frequency according to claim 1, wherein: the on-chip LDO circuit comprises a capacitor and a Zener diode and provides a supply voltage V of the whole timer circuitdd。
3. The adaptive off-time timer with adjustable switching frequency according to claim 2, wherein: the resistor string voltage division circuit divides the input voltage V intoinAnd dividing voltage according to ohm's law to obtain voltage proportional to the input voltage, and using the obtained voltage proportional to the input voltage as the input of the two-stage filtering.
4. The adaptive turn-off timer with adjustable switching frequency according to claim 3, wherein: the capacitor charging and discharging circuit utilizes the output voltage VoutFlows through the switching frequency adjusting resistor RfreqAfter current IchgCharging is carried out, and the charging time is the turn-off time ToffAnd a charging voltage VcAs the positive input of the comparator; when the switch tube is switched on and the synchronous tube is switched off, the voltage on the capacitor is discharged through the NMOS tube and the PMOS tube which are controlled by the driving voltage of the switch tube, so that the timing of the next switching-off time is started.
5. The adaptive turn-off timer with adjustable switching frequency according to claim 4, wherein: the two-stage filter circuit filters the voltage proportional to the input voltage twice to filter burrs and noise to obtain a direct current voltage kV approximate to the voltage proportional to the input voltageinK is the voltage division coefficient of the resistor string, and the obtained kVinAs the negative input to the comparator.
6. The adaptive turn-off timer with adjustable switching frequency according to claim 5, wherein: the comparator circuit will VcAnd kVinMaking a comparison when VcGreater than kVinAnd when the DC-DC boost converter is used, the comparator outputs a set signal, and the set signal drives the switching tube and the synchronous tube through the rear-stage trigger and the logic signal to realize the function of the DC-DC boost converter.
7. The adaptive turn-off timer with adjustable switching frequency according to claim 6, wherein: the off-chip switching frequency adjusting resistor adjusts the output voltage VoutCurrent I charging the capacitorchgTo change the charging time ToffWhen V is adaptive due to the self-adaptation of the circuitinAnd VoutWhen not changed, ToffThe switching frequency of the whole DC-DC boost converter is changed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201920573023.XU CN209913707U (en) | 2019-04-25 | 2019-04-25 | Self-adaptive turn-off time timer with adjustable switching frequency |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201920573023.XU CN209913707U (en) | 2019-04-25 | 2019-04-25 | Self-adaptive turn-off time timer with adjustable switching frequency |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN209913707U true CN209913707U (en) | 2020-01-07 |
Family
ID=69045467
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201920573023.XU Active CN209913707U (en) | 2019-04-25 | 2019-04-25 | Self-adaptive turn-off time timer with adjustable switching frequency |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN209913707U (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109980935A (en) * | 2019-04-25 | 2019-07-05 | 西安电子科技大学 | Self-adaptive turn-off time timer with adjustable switching frequency |
| CN113098272A (en) * | 2021-04-23 | 2021-07-09 | 陕西亚成微电子股份有限公司 | Control method and circuit of switching power supply |
| JP6993038B1 (en) | 2020-12-29 | 2022-01-13 | ▲広▼州大学 | Zero cross detector for boost converter circuit |
-
2019
- 2019-04-25 CN CN201920573023.XU patent/CN209913707U/en active Active
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109980935A (en) * | 2019-04-25 | 2019-07-05 | 西安电子科技大学 | Self-adaptive turn-off time timer with adjustable switching frequency |
| JP6993038B1 (en) | 2020-12-29 | 2022-01-13 | ▲広▼州大学 | Zero cross detector for boost converter circuit |
| JP2022104784A (en) * | 2020-12-29 | 2022-07-11 | ▲広▼州大学 | Zero-cross detection device of step-up converter circuit |
| CN113098272A (en) * | 2021-04-23 | 2021-07-09 | 陕西亚成微电子股份有限公司 | Control method and circuit of switching power supply |
| CN113098272B (en) * | 2021-04-23 | 2022-01-25 | 陕西亚成微电子股份有限公司 | Control method and circuit of switching power supply |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US10892686B2 (en) | Hysteretic control for transformer based power converters | |
| US10992231B1 (en) | Buck-boost converter and control method | |
| US8593125B1 (en) | Buck DC-DC converter with dual feedback control | |
| CN202889198U (en) | Switch type power supply and slope compensation signal generating circuit thereof | |
| US10778231B2 (en) | Clock dividing frequency circuit, control circuit and power management integrated circuit | |
| US9614437B2 (en) | Switching regulator and control circuit and control method therefor | |
| US8710816B2 (en) | Buck converter having reduced ripple under a light load | |
| CN209913707U (en) | Self-adaptive turn-off time timer with adjustable switching frequency | |
| KR20090063129A (en) | Constant on-time regulator with internal ripple generation and improved output voltage accuracy | |
| KR20090063135A (en) | Constant on-time regulator with increased maximum duty cycle | |
| CN104617771A (en) | Switching power converter system and control method thereof | |
| CN108390562A (en) | A kind of switching frequency correcting circuit for DC/DC | |
| US11705811B2 (en) | Buck-boost converter and hybrid control method | |
| Tattiwong et al. | Analysis design and experimental verification of a quadratic boost converter | |
| Gong et al. | An 80% peak efficiency, 0.84 mW sleep power consumption, fully-integrated DC-DC converter with buck/LDO mode control | |
| CN109617413B (en) | Boost chip and mode switching circuit thereof | |
| Yang et al. | Nonlinear variable frequency control of high power switched-capacitor converter | |
| CN114944748B (en) | Constant frequency control circuit and method for constant on-time control mode converter | |
| CN109980935A (en) | Self-adaptive turn-off time timer with adjustable switching frequency | |
| Ye et al. | PWM/PSM dual-mode controller for high efficiency DC-DC buck converter | |
| Tseng et al. | Fast transient voltage-mode buck regulator applying ramp signal with a variable DC-offset scheme | |
| CN112994467A (en) | Mixed modulation control method and circuit applied to primary side feedback flyback converter | |
| Jiang et al. | An IAOT controlled current-mode buck converter with RC-based inductor current sensor | |
| CN218648730U (en) | Switching frequency control circuit | |
| CN113422513B (en) | Control method of BUCK-BOOST converter |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| TR01 | Transfer of patent right |
Effective date of registration: 20220622 Address after: B201, zero one square, Xi'an Software Park, 72 Keji 2nd Road, high tech Zone, Xi'an City, Shaanxi Province, 710000 Patentee after: Tuoer Microelectronics Co.,Ltd. Address before: No.2, Taibai South Road, Yanta District, Xi'an City, Shaanxi Province Patentee before: XIDIAN University |
|
| TR01 | Transfer of patent right |