CN115378246B - Switching power supply with overshoot protection - Google Patents
Switching power supply with overshoot protection Download PDFInfo
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- CN115378246B CN115378246B CN202211073907.1A CN202211073907A CN115378246B CN 115378246 B CN115378246 B CN 115378246B CN 202211073907 A CN202211073907 A CN 202211073907A CN 115378246 B CN115378246 B CN 115378246B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
- H02M3/07—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider using capacitors charged and discharged alternately by semiconductor devices with control electrode, e.g. charge pumps
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The present disclosure provides a switching power supply with overshoot protection. The switching power supply includes: a step-down circuit including a first switch and a second switch connected in series, configured to charge or discharge an inductor by alternately turning on the first switch and the second switch to step down an input voltage to an output voltage; an overshoot protection circuit configured to generate a compensation voltage based on set values of the input voltage and the output voltage; and a switch control circuit that generates a switch control signal based on the compensation voltage and the input voltage to control the first switch and the second switch to be alternately turned on.
Description
Technical Field
The present disclosure relates to the field of power supplies, and more particularly, to a switching power supply with overshoot protection.
Background
The switching power supply converts an input voltage supplied from a power supply device (such as a battery or an adapter) on an input side into an output voltage suitable for the operation of a load on an output side by controlling on and off of a switching tube, so that the load operates normally. Currently, switching power supplies have been widely used in power supply applications for various electronic devices, for example, in the field of automotive electronics. In these applications, the input voltage often varies drastically, so that the output current and output voltage also suddenly change. In particular, in the case of a rapid rise after a rapid drop in the input voltage, the output voltage and the output current may occur beyond their set values due to a follow-up delay, which is also referred to as an overshoot.
Overshoot of the output voltage and output current may damage the switching power supply and even the loaded electronic components, affecting the life of the circuit or chip.
Disclosure of Invention
In view of the above, the present disclosure provides a switching power supply with overshoot protection, which can prevent overshoot of an output voltage and an output current when an abrupt change occurs in the input voltage.
In one aspect of the disclosure, a switching power supply with overshoot protection is provided. The switching power supply includes: a step-down circuit including a first switch and a second switch connected in series, configured to charge or discharge an inductor by alternately turning on the first switch and the second switch to step down an input voltage to an output voltage; an overshoot protection circuit configured to generate a compensation voltage based on set values of the input voltage and the output voltage; and a switch control circuit that generates a switch control signal based on the compensation voltage and the input voltage to control the first switch and the second switch to be alternately turned on.
In some embodiments, the compensation voltage comprises a first compensation voltage and a second compensation voltage, and the first compensation voltage is higher than the second compensation voltage, wherein the overshoot protection circuit is configured to: generating the first compensation voltage in response to the input voltage being lower than or equal to a set value of the output voltage; and generating the second compensation voltage in response to the input voltage being higher than a set value of the output voltage.
In some embodiments, the overshoot protection circuit includes: a protection voltage generation circuit configured to generate a protection voltage based on a feedback voltage associated with the output voltage, a predetermined reference voltage, and a predetermined current source; and a compensation voltage generation circuit configured to generate the compensation voltage based on the protection voltage, the predetermined reference voltage, and the feedback voltage.
In some embodiments, the protection voltage generation circuit includes: a comparator having one input receiving a first boost value of the feedback voltage and the other input receiving the predetermined reference voltage and generating a comparison signal based on the first boost value and the predetermined reference voltage; the voltage buffer is used for boosting the feedback voltage to a second boosting value under the triggering of the comparison signal; and a third switch that is turned on under control of a third switch control signal to supply the second boost value as the protection voltage, wherein the third switch control signal is obtained by an and operation of the comparison signal and the control signal.
In some embodiments, the compensation voltage generation circuit is configured to: generating the first compensation voltage based on the protection voltage and the feedback voltage in response to the protection voltage being less than the predetermined reference voltage; and generating the second compensation voltage based on the predetermined reference voltage and the feedback voltage in response to the protection voltage being greater than or equal to the predetermined reference voltage.
In some embodiments, the switch control circuit includes: an oscillator for generating an operation clock signal and a slope compensation signal having the same frequency; a pulse width modulation signal generator comparing the compensation voltage with a sum of the sampling signal of the input voltage and the ramp compensation signal to generate a pulse width modulation signal; and a switch control signal generation circuit that generates the switch control signal based on the operation clock signal and the pulse width modulation signal.
In some embodiments, the switch control signal includes a first switch control signal and a second switch control signal, and the control signal generation circuit includes: the clock input end of the D trigger receives the working clock signal, the rising edge of the working clock signal triggers and outputs the first switch control signal to conduct the first switch and disconnect the second switch, the reset end of the D trigger receives the pulse width modulation signal, and the D trigger is set to output the second switch control signal to conduct the second switch and disconnect the first switch.
In some embodiments, the step-down circuit further comprises: a voltage divider circuit configured to divide the output voltage to generate a feedback voltage associated with the output voltage.
By means of the scheme, the mode of soft start voltage is adjusted by detecting the change of the output voltage, so that smooth rising of the output voltage is achieved, overshoot of the output voltage and the output current is avoided, and temperature operation of a load is further guaranteed.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
Drawings
The above and other objects, structures and features of the present disclosure will become more apparent upon reading the following detailed description with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown by way of example and not by way of limitation. For clarity, the various features of the drawings are not drawn to scale.
Fig. 1 shows a schematic diagram of a switching power supply according to the prior art.
Fig. 2 shows a waveform timing diagram of a switching power supply according to the prior art.
Fig. 3 shows a schematic block diagram of a switching power supply with overshoot protection according to an embodiment of the present disclosure.
Fig. 4 schematically illustrates a detailed circuit diagram of a switching power supply with overshoot protection according to some embodiments of the present disclosure.
Fig. 5 schematically illustrates an operational waveform timing diagram of a switching power supply with overshoot protection according to an embodiment of the disclosure.
Detailed Description
Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present disclosure have been shown in the accompanying drawings, it is to be understood that the present disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are for illustration purposes only and are not intended to limit the scope of the present disclosure. It may be evident in some or all cases that any of the embodiments described below may be practiced without resorting to the specific design details described below. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more embodiments.
In describing embodiments of the present disclosure, the expression "comprising" and the like should be understood to be an open-ended inclusion, i.e., including, but not limited to. The expression "based on" should be understood as "based at least in part on". The expression "an embodiment" or "this embodiment" should be understood as "at least one embodiment". The expressions "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions are also possible below.
Fig. 1 shows a schematic diagram of a switching power supply 10 according to the prior art. Fig. 2 shows a waveform timing diagram of a switching power supply according to the prior art.
As shown in fig. 1, the switching power supply 10 may include a voltage step-down circuit 110, and the voltage step-down circuit 110 may step down an input voltage Vin to an output voltage Vout. For example, the buck circuit 110 may alternately turn on two of the switches to charge and discharge the inductor therein to achieve buck conversion.
The switching power supply 10 may further include a switching control circuit 130, wherein the switching control circuit 130 may compare the feedback voltage Vfb associated with the output voltage Vout with a predetermined reference voltage Vref, and generate the compensation voltage Vcomp according to the comparison result. The compensation voltage Vcomp, together with the sampling voltage Vsense of the input voltage Vin, determines the on and off of the two switches in the step-down circuit 110 under the action of the clock signal CLK generated by the switch control circuit 130.
As shown in fig. 2, it is assumed that at time t1, the input voltage Vin starts to decrease rapidly. By time t2, the input voltage Vin may drop below the set value V0 of the output voltage Vout. Thereafter, the output voltage Vout may drop following the input voltage Vin, the feedback voltage Vfb may drop below the predetermined reference voltage Vref, and the compensation voltage Vcomp may rapidly rise to a maximum value.
If the input voltage Vin starts to suddenly increase again shortly after decreasing to the minimum value (time t 3) (time t 4), the feedback voltage Vfb is still smaller than the predetermined reference voltage Vref because the output voltage Vout cannot suddenly change, and the compensation voltage Vcomp continues to be kept high to continuously boost the output voltage Vout.
At time t5 when the output voltage Vout reaches its set value V0, the feedback voltage Vfb starts to be greater than the reference voltage Vref, the compensation voltage Vcomp starts to decrease, and the control loop adjusts the feedback voltage Vfb to adjust the compensation voltage Vcomp to a stable value. During this process, the output voltage Vout may overshoot (as shown by reference numeral 202 in fig. 2), and during the rising of the output voltage Vout (e.g., during the time period from t4 to t 5), the output current Iout may also overshoot (as shown by reference numeral 204 in fig. 2). Both the overshoot of the output voltage Vout and the output current Iout are undesirable and may damage the entire switching power supply and even the load.
It can be seen that the main reason for the overshoot is that the output voltage Vout cannot be suddenly changed, so that the feedback voltage Vfb that follows it also lags relatively, and thus the compensation voltage Vcomp that is determined by the feedback voltage Vfb and the predetermined reference voltage Vref also lags relatively, so that the compensation voltage Vcomp may still compensate the output voltage Vout when it has reached its set value V0, thereby generating an output voltage overshoot.
In view of the above, in the embodiments of the present disclosure, the manner in which the soft start voltage is adjusted (i.e., the manner in which the compensation voltage Vcomp is generated) by detecting the change in the output voltage Vout, thereby avoiding that the compensation voltage Vcomp is still compensating for the output voltage Vout when it has reached the set value V0.
Fig. 3 shows a schematic block diagram of a switching power supply 20 with overshoot protection according to an embodiment of the present disclosure. The switching power supply 20 may buck-convert an input voltage Vin provided by a power supply (not shown) to an output voltage Vout to power a load (not shown). The switching power supply of fig. 3 is a typical peak current and output voltage dual loop controlled buck converter.
Similar to the switching power supply 10 in fig. 1, the switching power supply 20 may also include a step-down circuit 210 and a switching control circuit 230 similar to the step-down circuit 110 and the switching control circuit 130. Unlike the switching power supply 10 in fig. 1, the switching power supply 20 further includes an overshoot protection circuit 220.
The voltage-reducing circuit 210 includes a first switch Q1 and a second switch Q2 (as shown in fig. 4) connected in series, and is configured to charge or discharge the inductor L by alternately turning on the first switch Q1 and the second switch Q2 to reduce the input voltage Vin to the output voltage Vout.
The overshoot protection circuit 220 is configured to generate the compensation voltage Vcomp based on the set value V0 of the input voltage Vin and the output voltage Vout.
Here, specifically, the compensation voltage Vcomp may include a first compensation voltage Vcomp1 and a second compensation voltage Vcomp2. The overshoot protection circuit 220 is configured to generate the first compensation voltage Vcomp1 when the input voltage Vin is lower than or equal to the set value V0 of the output voltage Vout, and to generate the second compensation voltage Vcomp2 when the input voltage Vin is higher than the set value V0 of the output voltage Vout. Here, the first compensation voltage Vcomp1 is higher than the second compensation voltage Vcomp2. In this way, the overshoot protection circuit 220 can generate a higher compensation voltage Vcomp when the input voltage Vin is lower than or equal to the set value V0 of the output voltage Vout, and the overshoot protection circuit 220 can generate a lower compensation voltage Vcomp when the input voltage Vin increases again to be higher than the set value V0 of the output voltage Vout, thereby avoiding the output voltage Vout from overshooting due to the higher compensation voltage Vcomp.
Here, the set value V0 may have different values depending on the application of the switching power supply 20, and the set value V0 of the output voltage Vout may be provided by an internal or external voltage source, which will not be described herein.
The switch control circuit 230 may generate a switch control signal to control the first switch Q1 and the second switch Q2 to be alternately turned on based on the compensation voltage Vcomp and the input voltage Vin.
Fig. 4 illustrates a detailed circuit diagram of a switching power supply 20 with overshoot protection according to some embodiments of the present disclosure.
As shown in fig. 4, the voltage step-down circuit 210 includes a first switch Q1 and a second switch Q2 connected in series to the ground, and the junction of the first switch Q1 and the second switch Q2 is connected in series with an inductor L and a capacitor Co. Under the control of the switch control signal from the switch control circuit 230, the first switch Q1 and the second switch Q2 are alternately turned on to charge and discharge the inductor L, thereby stepping down the input voltage Vin to the output voltage Vout. The first and second switches Q1 and Q2 may be implemented using field effect transistors (MOSFETs). For example, as shown in fig. 4, both the first switch Q1 and the second switch Q2 are implemented using an N-type MOSFET (NMOS transistor), wherein the gate of the first switch Q1 is connected to a switch control signal (more specifically, the first switch control signal HSD, as described below), the drain is connected to the input voltage Vin, and the source is connected to the drain of the second switch Q2. The gate of the second switch Q2 is connected to a switch control signal (more specifically, a second switch control signal LSD, as described below), the drain is connected to the source of the first switch Q1, and the source is Grounded (GND). However, it will be appreciated by those skilled in the art that the present invention is not limited thereto, and the first switch Q1 and the second switch Q2 may be implemented using various other diodes, bipolar transistors, or other electronic devices, or combinations thereof.
In addition, the step-down circuit 210 further includes a resistor Ro connected in parallel with the capacitor Co to protect charge and discharge of the capacitor Co.
When the first switch Q1 is turned on, the input voltage Vin charges the inductor L and the capacitor Co to generate an output voltage Vout to supply power to the load. During this time, the second switch Q2 is turned off, and the current flowing through the inductor L is equal to the current flowing through the first switch Q1, and gradually increases with the lapse of time. When the first switch Q1 is turned off and the second switch Q2 is turned on, the inductor L and the capacitor Co supply power to the load, and the current flowing through the inductor L gradually decreases. Thus, by alternately turning on the first switch Q1 and the second switch Q2, the voltage-reducing circuit 210 can reduce the input voltage Vin to the output voltage Vout to supply power to the load.
In some embodiments, the step-down circuit 210 may further include a voltage dividing circuit for dividing the output voltage Vout to generate the feedback voltage Vfb associated with the output voltage Vout. The voltage dividing circuit may be constituted by, for example, resistors Rf1 and Rf2 connected in series, one end of which is connected to the inductor L, receives the output voltage Vout, the other end of which is grounded, and the voltage of the connection point of the resistors Rf1 and Rf2 is input as a feedback voltage Vfb to the overshoot protection circuit 220.
The overshoot protection circuit 220 may include a protection voltage generation circuit 222, the protection voltage generation circuit 222 being configured to generate the protection voltage Vss based on the feedback voltage Vfb associated with the output voltage Vout, the predetermined reference voltage Vref, and the predetermined current source Iss. Here, the predetermined reference voltage Vref may have different values depending on the application parameters of the switching power supply 20, and may be provided by an internal or external voltage source, which will not be described herein.
The overshoot protection circuit 220 may further include a compensation voltage generation circuit 224, the compensation voltage generation circuit 224 being configured to generate the compensation voltage Vcomp based on the protection voltage Vss, the predetermined reference voltage Vref, and the feedback voltage Vfb.
In some embodiments, the protection voltage generation circuit 222 may include a comparator CMP1, a voltage buffer Buf1, and a third switch K1.
One input terminal of the comparator CMP1 receives the first boost value Va of the feedback voltage Vfb, the other input terminal receives the predetermined reference voltage Vref, and generates the comparison voltage fb_l based on the first boost value Va and the predetermined reference voltage Vref. Here, the first boost value Va of the feedback voltage Vfb may be obtained by boosting the feedback voltage Vfb by a fixed voltage source os1, for example, a weak voltage source that can supply a voltage Vos1 of several tens of mv. The first boost value Va may be expressed as va=vfb+vos1.
The voltage buffer Buf1 boosts the feedback voltage Vfb to the second boost value Vb under the triggering of the comparison voltage fb_l (for example, when the low level is changed to the high level). Here, similarly, the second boost value Vb may also be obtained by boosting the feedback voltage Vfb by another fixed voltage source os2, which fixed voltage source os2 may for example provide a voltage Vos2 of several tens mv, which may be the same as or different from the fixed voltage source os1. The second boost value may be expressed as vb=vfb+vos2.
The third switch K1 may be turned on under the control of the third switch control signal en_k to supply the second boost value Vb as the protection voltage Vss, i.e., vss=vb=vfb+vos2. Here, the third switching control signal en_k may be obtained by performing an and operation on the comparison voltage fb_l and the control signal ldo_mode by the and gate I1, for example.
The compensation voltage generation circuit 224 is configured to compare the protection voltage Vss with a predetermined reference voltage Vref, and generate a compensation voltage Vcomp based on the comparison result.
Specifically, if the protection voltage Vss is less than the predetermined reference voltage Vref, the compensation voltage generation circuit 224 may generate the first compensation voltage Vcomp1 based on the protection voltage Vss and the feedback voltage Vfb; the compensation voltage generation circuit 224 may generate the second compensation voltage Vcomp2 based on the predetermined reference voltage Vref and the feedback voltage Vfb if the protection voltage Vss is greater than or equal to the predetermined reference voltage Vref. Here, the compensation voltage generation circuit 224 may be implemented, for example, using an Error Amplifier (EA) having two positive inputs connected to the protection voltage Vss and the predetermined reference voltage Vref, respectively, and a negative input connected to the feedback voltage Vfb, as shown in fig. 4.
In this way, it is possible to generate different protection voltages Vss as the output voltage Vout changes, and to change the manner of generating the compensation voltage Vcomp as the magnitude of the protection voltage Vss, thereby avoiding that the compensation voltage Vcomp is still compensating for the output voltage Vout when it has reached the set value V0.
In some embodiments, the switch control circuit 230 may include an oscillator 232, a pulse width modulation signal generator 234, and a switch control signal generation circuit 236.
The oscillator 232 is used to generate the operating clock signal CLK and the Ramp compensation signal Ramp. The Ramp compensation signal Ramp has the same frequency as the operating clock signal CLK, and has a different waveform, i.e., a Ramp waveform.
The pulse width modulation signal generator 234 may compare the compensation voltage Vcomp with the sum of the sampling signal Vsense of the input voltage Vin and the slope compensation signal Ramp to generate the pulse width modulation signal PWM. Here, the sampling signal Vsense of the input voltage Vin may be obtained by sampling the input voltage Vin every time the first switch Q1 is turned on. By adding the slope compensation signal Ramp to the sampling signal Vsense of the input voltage Vin and comparing the result with the compensation voltage Vcomp, subharmonic oscillation at a high duty ratio can be avoided and noise immunity can be improved.
The switch control signal generating circuit 236 may generate the switch control signal based on the operation clock signal CLK and the pulse width modulation signal PWM.
In some embodiments, the switch control signals may include a first switch control signal and a second switch control signal. The first switch control signal is used for conducting the first switch Q1 and opening the second switch Q2, and the second switch control signal is used for conducting the second switch Q2 and opening the first switch Q1.
In some embodiments, the switch control signal generation circuit 236 may include a D flip-flop DFF, as shown in fig. 4. The clock input (CLK) of the D flip-flop DFF receives the operating clock signal CLK, and is triggered by a rising edge of the operating clock signal CLK to output the first switching control signal HSD. The RESET terminal (RESET) of the D flip-flop DFF receives a pulse width modulation signal PWM that sets the D flip-flop DFF to output the second switching control signal LSD. Specifically, as shown in fig. 4, at the rising edge of the operation clock signal CLK, the output terminal Q of the D flip-flop DFF becomes high level, so that the first switch control signal HSD of high level is outputted to drive the first switch Q1 to be turned on, and at the same time, the output terminal XQ (which is the inverse of the output terminal Q) becomes low level, that is, the second switch control signal LSD is low to turn off the second switch Q2. When the pulse width modulation signal PWM becomes high level, the D flip-flop DFF is set, and the output terminal Q becomes low level, so that the first switch control signal HSD of low level is outputted to drive the first switch Q1 to be turned off, and at the same time, the output terminal XQ becomes high level, that is, the second switch control signal LSD becomes high to drive the second switch Q2 to be turned on.
Fig. 5 schematically illustrates a timing diagram of an operating waveform of a switching power supply 20 with overshoot protection according to an embodiment of the disclosure.
As shown in fig. 5, after the switching power supply 20 starts to start, the current source Iss charges the capacitor Css, the protection voltage Vss rises from zero, and the feedback voltage Vfb rises with the protection voltage Vss.
At time t1', the protection voltage Vss rises above the predetermined reference voltage Vref, at which time the magnitude of the feedback voltage Vfb begins to be determined by the predetermined reference voltage Vref (i.e., vfb=vref, as shown), and the protection voltage Vss may continue to rise until it approaches the voltage of the current source Iss. Meanwhile, since Vfb > Vref-Vos1, va > Vref, the comparison voltage fb_l becomes low from high.
Assume that at a time t2' after the output voltage Vout is at the set value V0, the input voltage Vin suddenly changes from high to low, decreases to a set value V0 lower than the output voltage Vout, and at this time the feedback voltage Vfb starts to be smaller than the predetermined reference voltage Vref.
When the feedback voltage Vfb decreases below the predetermined reference voltage Vref, the compensation voltage Vcomp starts to rise from a low level to a high level. When the feedback voltage Vfb continues to decrease below Vref-Vos1 (time t 3'), the comparator CMP1 starts to operate, the comparison voltage fb_l changes from low to high, and the trigger control signal ldo_mode is also high because the input voltage Vin is smaller than the set value V0 of the output voltage Vout. At this time, the voltage buffer Buf1 is enabled, outputting the voltage Vb, vb=vfb+vos2. At this time, since the input voltage Vin is lower than the set value V0 of the output voltage Vout, the first switch Q1 is turned on, and thus the final output voltage Vout is approximately equal to the input voltage Vin. At this time, the feedback voltage Vfb reaches the substantially stable voltage value Vfb0 due to the voltage division of the resistors Rf1 and Rf2, which can be expressed as:
Vfb0＝Rf2/(Rf1+Rf2)*Vout＝Rf2/(Rf1+Rf2)*Vin
at this time, the first switch Q1 is kept normally open, the control signal ldo_mode is high, the comparison signal fb_l is also high, the third switch control signal en_k is high through the and gate I1, and the third switch K1 is in an on state. Since the current capability of the current source Iss is weak, typically in the nA level, and the output driving capability of the voltage buffer Buf1 is strong, the protection voltage Vss is forcibly set to vss=vb=vfb0+vos2.
Thereafter, it is assumed that at time t4', the input voltage Vin suddenly rises to the normal voltage, at which time the first switch Q1 is turned off, and the control signal ldo_mode is changed from high to low when the input voltage Vin rises to be higher than the output voltage Vout. At this time, under the action of the and gate I1, the third switch control signal en_k becomes a low level, the third switch K1 is turned off, the protection voltage Vss starts to rise gradually from vfb0+vos2, and the feedback voltage Vfb also will rise gradually along with the voltage of the protection voltage Vss, so that the compensation voltage Vcomp will be reduced to a reasonable value during the rising process of the feedback voltage Vfb, and overshoot of the output current Iout and the output voltage Vout will not occur.
By using the embodiment of the disclosure, the mode of regulating the soft start voltage is realized by detecting the change of the output voltage, so that the smooth rising of the output voltage is realized, and the overshoot of the output voltage and the output current is avoided, so that the temperature work of the load is further ensured.
Further, the present disclosure provides various example embodiments, as described and as shown in the accompanying drawings. However, the present disclosure is not limited to the embodiments described and illustrated herein, but may be extended to other embodiments as would be known or would be apparent to one of ordinary skill in the art. Reference in the specification to "one embodiment," "the embodiment," "these embodiments," or "some embodiments" means that a particular feature, structure, or characteristic described is included in at least one embodiment, and that the appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment.
Finally, although the various embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended representations is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as example forms of implementing the claimed subject matter.
Claims (7)
1. A switching power supply with overshoot protection, comprising:
a step-down circuit including a first switch and a second switch connected in series, configured to charge or discharge an inductor by alternately turning on the first switch and the second switch to step down an input voltage to an output voltage;
an overshoot protection circuit configured to generate a compensation voltage based on set values of the input voltage and the output voltage; and
a switch control circuit for generating a switch control signal based on the compensation voltage and the input voltage to control the first switch and the second switch to be alternately turned on,
wherein the compensation voltage comprises a first compensation voltage and a second compensation voltage, and the first compensation voltage is higher than the second compensation voltage, wherein the overshoot protection circuit is configured to:
generating the first compensation voltage in response to the input voltage being lower than or equal to a set value of the output voltage; and
the second compensation voltage is generated in response to the input voltage being higher than a set point of the output voltage.
2. The switching power supply of claim 1 wherein the overshoot protection circuit comprises:
a protection voltage generation circuit configured to generate a protection voltage based on a feedback voltage associated with the output voltage, a predetermined reference voltage, and a predetermined current source; and
and a compensation voltage generation circuit configured to generate the compensation voltage based on the protection voltage, the predetermined reference voltage, and the feedback voltage.
3. The switching power supply of claim 2 wherein the protection voltage generation circuit comprises:
a comparator having one input receiving a first boost value of the feedback voltage and the other input receiving the predetermined reference voltage and generating a comparison signal based on the first boost value and the predetermined reference voltage;
the voltage buffer is used for boosting the feedback voltage to a second boosting value under the triggering of the comparison signal; and
and a third switch that is turned on under control of a third switch control signal to supply the second boost value as the protection voltage, wherein the third switch control signal is obtained by an and operation of the comparison signal and a control signal that is triggered to be high level when the input voltage is smaller than a set value of the output voltage.
4. The switching power supply of claim 2 wherein the compensation voltage generation circuit is configured to:
generating the first compensation voltage based on the protection voltage and the feedback voltage in response to the protection voltage being less than the predetermined reference voltage; and
the second compensation voltage is generated based on the predetermined reference voltage and the feedback voltage in response to the protection voltage being greater than or equal to the predetermined reference voltage.
5. The switching power supply of claim 1 wherein the switch control circuit comprises:
an oscillator for generating an operation clock signal and a slope compensation signal having the same frequency;
a pulse width modulation signal generator comparing a sum of the sampling signal of the input voltage and the slope compensation signal with the compensation voltage to generate a pulse width modulation signal; and
and a switch control signal generating circuit that generates the switch control signal based on the operation clock signal and the pulse width modulation signal.
6. The switching power supply of claim 5 wherein the switch control signal comprises a first switch control signal and a second switch control signal, and the switch control signal generation circuit comprises:
the clock input end of the D trigger receives the working clock signal, the rising edge of the working clock signal triggers and outputs the first switch control signal to conduct the first switch and disconnect the second switch, the reset end of the D trigger receives the pulse width modulation signal, and the D trigger is set to output the second switch control signal to conduct the second switch and disconnect the first switch.
7. The switching power supply of claim 2 wherein the step-down circuit further comprises:
a voltage divider circuit configured to divide the output voltage to generate the feedback voltage associated with the output voltage.
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| CN104821718B (en) * | 2015-05-05 | 2018-08-28 | 南京矽力杰半导体技术有限公司 | Boost booster types circuit and its control method based on input voltage feed forward control |
| CN106300944B (en) * | 2016-08-06 | 2018-12-14 | 杰华特微电子（张家港）有限公司 | Over-current control circuit crosses method of flow control and the power-supply system using it |
| US11362579B2 (en) * | 2019-09-27 | 2022-06-14 | Apple Inc. | Peak voltage overshoot control for switch mode power converters |
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