CN210297567U - Switching power supply control circuit for improving dynamic performance and switching power supply system - Google Patents
Switching power supply control circuit for improving dynamic performance and switching power supply system Download PDFInfo
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- CN210297567U CN210297567U CN201921494799.9U CN201921494799U CN210297567U CN 210297567 U CN210297567 U CN 210297567U CN 201921494799 U CN201921494799 U CN 201921494799U CN 210297567 U CN210297567 U CN 210297567U
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Abstract
The utility model discloses an improve switching power supply control circuit and switching power supply system of dynamic performance, peak current that can real-time supervision switching power supply, and when detecting that the cycle number that appears first kind of peak current in succession reaches predetermined threshold number, just think that the system is in the heavy duty and switch into heavy-duty switching dynamic mode in the underload, at this moment switch first kind of peak current to second kind of peak current (be big Ipk) immediately, wherein, first kind of peak current is the peak current when switching power supply is in the underload state, first kind of peak current is less than predetermined peak threshold and appears in the form of full duty cycle; in this state, the output voltage of the switching power supply is rapidly raised only when the output voltage drops by the first-class peak current (i.e., the small Ipk) of the threshold number (e.g., 4), so that the dynamic response performance is optimized.
Description
Technical Field
The utility model relates to a switching power supply control technology field especially relates to a switching power supply control circuit and switching power supply system who improves dynamic performance.
Background
The power supply is an indispensable component of each electronic device, and the performance of the power supply is directly related to the technical index of the electronic device and whether the electronic device can safely and reliably operate, while the current mainstream application is a Switch Mode power supply (Switch Mode). A switching power supply, also called a switching converter, is a power supply that makes an output voltage or an output current constant by adjusting a conduction ratio or a frequency of a switching device using modern power electronics technology. Compared with the traditional linear power supply, the switching power supply has the characteristics of small volume, good stability and high conversion efficiency, so that the switching power supply is widely applied to occasions such as chargers, power adapters, LED driving power supplies, wireless communication equipment, liquid crystal display power supply management, electronic refrigerators, Ethernet power supplies and the like.
As the switching power supply needs to adapt to different working conditions, the requirements on the dynamic response performance of the switching power supply are higher and higher. For example, when the switching power supply is applied to a charger of an electronic device (e.g., a mobile phone), the stability of the terminal voltage of the charger (i.e., the charged terminal, e.g., the mobile phone terminal) is an important measure of the performance of the charger. Referring to fig. 1, fig. 1 is a schematic diagram of a conventional charger (i.e., a primary side controlled switching power supply). The charger comprises a bridge rectifier circuit U1, a high-voltage filter capacitor C1, a primary winding Lp of a transformer, an auxiliary winding Laux of the transformer, a secondary winding Ls of the transformer, a switching power supply control circuit IC, a power switch tube M1 and the like. The primary winding Lp of the transformer, the auxiliary winding Laux of the transformer and the secondary winding Ls of the transformer form the transformer which is mainly used for electric isolation and energy transmission of input and output. The ac power source Vac generates an input voltage Vin through a bridge rectifier circuit U1, and the input voltage Vin supplies power to the primary side of the transformer. The gate of the power switch M1 is connected to the driving terminal DRI of the switching power supply control circuit IC,the drain electrode is connected with one end of a primary winding Lp of the transformer, the source electrode is grounded through a series sampling resistor Rcs, and the source electrode of the power switch tube M1 and the common end of the sampling resistor Rcs are connected with the peak current sampling end CS end of the switch power supply control circuit IC. The other end of the primary winding Lp of the transformer is connected to the output end of the bridge rectifier circuit U1 to receive the input voltage Vin. The same-name end of the auxiliary winding Laux of the transformer is grounded by connecting two feedback resistors Rfb1 and Rfb2 which are connected in series to obtain a feedback voltage VFBFor realizing the feedback of the secondary output voltage Vout to the switching power supply control circuit IC, in particular, the feedback voltage V because the voltage of the transformer auxiliary winding Laux has a turn ratio relationship with the voltage of the transformer secondary winding LsFBThe common end of the two feedback resistors Rfb1 and Rfb2 is connected to the output voltage feedback end FB end of the switching power supply control circuit IC, reflecting the change of the secondary output voltage Vout. One end of the transformer auxiliary winding Laux is further connected with the anode of the power supply diode Daux, the cathode of the power supply diode Daux is connected with the common end of the resistor Rst and the capacitor C2, the other end of the transformer auxiliary winding Laux is grounded, the resistor Rst and the capacitor C2 form an RC starting circuit, and the common end of the resistor Rst and the capacitor C2 is connected with the power supply end VCC end of the control circuit IC to provide working voltage for the switching power supply control circuit IC. One end of the secondary winding Ls of the transformer is connected with the anode of the diode Ds, and the other end of the secondary winding Ls of the transformer is grounded. A capacitor C3, a resistor R0 and a load RL are connected between the cathode of a diode Ds and the ground in parallel, the diode Ds are used for rectifying and stabilizing voltage, and the capacitor C3 and the resistor R0 which are connected in parallel are used for forming an output filter circuit for filtering the output voltage Vout. The switching power supply control circuit IC obtains V according to the obtained VFB、VCC、VCSAnd an internally preset reference voltage VREFThe peak current Ipk of the primary winding Lp is adjusted to generate a PFM signal and output the PFM signal to the driving end DRI to control the on/off of the power switch M1, so as to realize the process of transmitting energy from the primary winding Lp of the transformer to the output end of the secondary winding Ls of the transformer, and adjust the output voltage Vout to quickly respond to the switching of the load RL state of the secondary.
In FIG. 2 is shown VFBThe time profile, as can be seen from figure 2,when the charger works normally, one switching period T of the power switch tube M1 is actually divided into three phases: in the primary side conduction stage Tonp (Tonp is primary side conduction time), the secondary side conduction stage Tons (Tons is secondary side conduction time) and the primary side and secondary side both-off stage Toff (Toff is off time), referring to fig. 1, the primary side winding Lp stores energy in the primary side conduction stage Tonp, the energy stored in the primary side winding Lp is transmitted to the secondary side circuit in the secondary side conduction stage Tons, and the secondary side current gradually decreases to 0. However, in the case where the load RL state of the electronic device is suddenly switched from a light load to a heavy load (for example, from a 10% load to a 90% load), as shown in fig. 2, V is detected by the switching power supply control circuit IC at the moment of TsampleFB(V at this time)FBProportional to Vout) is lower than VREFIn the meantime, the current small Ipk is switched to the large Ipk inside the switching power supply control circuit IC, and the output voltage Vout starts to rise at this time, as shown in fig. 3, in this case, the pulses of the small Ipk are clustered to reach dozens of or even twenty pulses, and the output voltage continues to drop during this period, so that the dynamic performance is deteriorated. Therefore, how to provide a switching power supply control circuit and a switching power supply system for improving the output dynamic performance of a charger is a problem that needs to be solved by those skilled in the art at present.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide an improve switching power supply control circuit and switching power supply system of dynamic performance can make output voltage quick response switching power supply's load condition switch to the heavy condition of carrying from the light load, promotes switching power supply's dynamic response performance.
In order to achieve the above object, the present invention provides a switching power supply control circuit for improving dynamic performance, including:
the dynamic monitoring circuit is used for monitoring the number of cycles of first-class peak current continuously generated by the switching power supply and generating a peak current switching signal when the monitored number of cycles reaches a preset threshold number, wherein the first-class peak current is the peak current of the switching power supply in a light load state, and the first-class peak current is smaller than a preset peak threshold and is generated in a full duty ratio mode;
the peak current control circuit is used for generating a peak current control signal for switching the peak current of the switching power supply into a second type of peak current according to the peak current switching signal, wherein the second type of peak current is the peak current of the switching power supply in a heavy load state;
the main control circuit is connected with the dynamic monitoring circuit and the peak current control circuit and is used for controlling the work of the dynamic monitoring circuit and the peak current control circuit, adjusting the peak current of the switching power supply to be switched into a second type of peak current according to the peak current control signal and outputting a control logic signal related to the second type of peak current; and
and the driving circuit is connected with the main control circuit and used for outputting a driving signal according to the control logic signal so as to control the on-off of a power switch tube of the switching power supply and lift the output voltage of the switching power supply.
Optionally, the second type of peak current occurs in the form of a full duty cycle.
Optionally, the dynamic monitoring circuit comprises:
the enabling signal generating module is connected with the main control circuit, is used for initializing according to the initialization signal of the main control circuit and generating an enabling signal according to the corresponding control signal of the main control circuit;
the clock signal generating module is used for generating a periodic clock signal according to a primary side conduction time signal of the switching power supply and the peak current of the switching power supply;
the counting module is used for performing accumulated counting on the periodic clock signals with high level or low level under the control of the enabling signal so as to monitor the number of periods of the first type of peak current continuously appearing on the switching power supply;
and the pulse generator is used for generating a peak current switching signal when the number of the cycles counted by the counting module reaches a preset threshold number.
Optionally, the enable signal generation module includes a first nor gate, a second nor gate and a third nor gate, the clock signal generation module includes an and gate, and the counting module includes three cascaded flip-flops; wherein, an input terminal of the first nor gate receives a first signal, another input terminal of the first nor gate is connected with an output terminal of the second nor gate and an input terminal of a third nor gate, and an output terminal of the first nor gate is connected with a first input terminal of the second nor gate; the second input end of the second nor gate and the other input end of the third nor gate are both connected with an initialization signal for initializing the dynamic monitoring circuit, and the third input end of the second nor gate is connected with a second signal; the output end of the third NOR gate is connected with the asynchronous position setting ends of the three triggers, one input end of the AND gate is connected with a third signal, and the other input end of the AND gate is connected with a fourth signal; the clock end of the first stage trigger of the three triggers is connected with the output end of the AND gate, and the inverted output end of the third stage trigger is connected with the input end of the pulse generator; the first signal is a high signal in a time period from the time when the switching power supply enters the turn-off stage to the end of the turn-off stage, the third signal is a primary side on-time signal of the switching power supply, the second signal is a signal obtained by delaying the primary side on-time signal for a predetermined time, and the fourth signal is a high signal when the peak current of the switching power supply is smaller than the peak threshold.
Optionally, the switching power supply control circuit further includes a load state monitoring circuit connected to the main control circuit, and configured to monitor whether a load state of the switching power supply is switched from a light load to a heavy load, and generate a count trigger signal when it is monitored that the load state is switched from the light load to the heavy load; the main control circuit is used for initializing the dynamic monitoring circuit according to the counting trigger signal so that the dynamic monitoring circuit starts to monitor the number of cycles of continuous occurrence of the first type of peak current in the switching power supply.
Optionally, the switching power supply control circuit further includes an output voltage detection circuit connected between the main control circuit and a secondary output voltage feedback end of the switching power supply, where the output voltage detection circuit is configured to feed back a change condition of an output voltage of a secondary of the switching power supply to the main control circuit.
Optionally, the switching power supply control circuit further includes a reference voltage generation circuit connected between the main control circuit and a primary side input voltage feedback end of the switching power supply, the reference voltage generation circuit is configured to generate a corresponding reference voltage according to a voltage of the primary side input voltage feedback end and output the reference voltage to the main control circuit, and the main control circuit adjusts the peak current of the switching power supply to be switched from the first type of peak current to the second type of peak current based on the reference voltage and the peak current control signal.
Based on same utility model the design, the utility model also provides a switching power supply system, including the power switch pipe and if the switching power supply control circuit of improvement dynamic behavior, the control end of power switch pipe is connected switching power supply control circuit's drive circuit.
Optionally, the switching power supply system further includes:
the input rectification filter circuit is used for converting the alternating current voltage signal into a periodic direct current pulse voltage signal;
the transformer is provided with a primary winding, a secondary winding and an auxiliary winding which are coupled with the input rectifying and filtering circuit, and a driving circuit in the switching power supply control circuit is coupled to the primary winding;
the output rectifying and filtering circuit is electrically connected with the secondary winding and is used for rectifying and filtering the output signal of the secondary winding;
and the output voltage feedback circuit is connected between the auxiliary winding and the switching power supply control circuit and is used for sampling and feeding back the output voltage of the secondary winding.
Compared with the prior art, the technical scheme of the utility model, peak current Ipk that can real-time supervision switching power supply, when detecting that the cycle number that appears first kind peak current (being little Ipk, do not have the peak current of Toff time, its pulse appears in succession with the form of full duty cycle) reaches predetermined threshold number (for example be 4, 4 periods have appeared in succession at little Ipk), just think that the system is in the light load and switches into the heavy duty and switch dynamic mode, at this moment switch first kind peak current (being little Ipk) to second kind peak current (being big Ipk, its pulse is in the form of full duty cycle), under this state, switching power supply's output voltage only drops threshold number (for example 4) the time that little Ipk will lift up rapidly to dynamic response performance has been optimized. The technical scheme of the utility model can be applied to switching power supply system separately, for example charger, power adapter, LED drive power supply, wireless communication equipment, LCD screen power management, electron refrigerator or ethernet power etc to reinforcing switching power supply system's dynamic response performance.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a system schematic diagram of a conventional charger.
FIG. 2 is a feedback value V of the output voltage of the charger system shown in FIG. 1FBTime profile.
FIG. 3 is a graph showing the output voltage Vout, the peak current Ipk and the feedback value V of the output voltage when the charger system shown in FIG. 1 is switched from a light load to a heavy loadFBTime profile.
Fig. 4 is a schematic circuit diagram of a switching power supply control circuit for improving dynamic performance according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a switching power supply system according to an embodiment of the present invention.
Fig. 6 is a schematic diagram of a dynamic monitoring circuit according to an embodiment of the present invention.
Fig. 7 is a timing diagram corresponding to the input signals and the switching power supply required by the dynamic monitoring circuit according to an embodiment of the present invention.
Fig. 8 is a timing diagram of the input signal and the output signal of the dynamic monitoring circuit and the output voltage and the feedback value of the switching power supply according to an embodiment of the present invention.
Fig. 9 is a comparison graph of the dynamic response effect between the present invention and the prior art when the light load is switched to the heavy load.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
Referring to fig. 4 and 5, an embodiment of the present invention provides a switching power supply control circuit for improving dynamic performance, including: the circuit comprises a reference voltage generating circuit 101, a load state monitoring circuit 102, an output voltage detection circuit 103, a main control circuit 104, a dynamic monitoring circuit 105, a peak current control circuit 106 and a driving circuit 107. The switching power supply control circuit is provided with a power supply end VCC, a voltage feedback end FB, a peak current sampling end CS and a driving end DRI. The utility model discloses a switching power supply control circuit can be a controller chip, can insert in the primary side control formula switching power supply system to sampling switching power supply system's former limit peak current Ipk, and drive switching power supply system's power switch pipe work, and then control switching power supply system's vice limit output voltage's size.
Referring to fig. 4 to fig. 7, one input terminal of the dynamic monitoring circuit 105 is connected to the peak current sampling terminal CS, the other input terminal thereof receives the control signal of the main control circuit 104, and the output terminal thereof is connected to the input terminal of the peak current control circuit 106. The dynamic monitoring circuit 105 is configured to monitor the number N of cycles of the first-class peak current Ipk1 that continuously occurs in the switching power supply, and generate a peak current switching signal when the monitored number N of cycles reaches a preset threshold number N (for example, N is 4), where the first-class peak current is a peak current of the switching power supply in a light load state, and the first-class peak current is smaller than a preset peak threshold and occurs in a full duty cycle. Referring to fig. 6, the dynamic monitoring circuit 105 includes an enable signal generating module 105a, a clock signal generating module 105b, a counting module 105c, and a pulse generator P1. The Enable signal generating module 105a is connected to the main control circuit 104, and is configured to initialize according to an initialization signal Init _ HL of the main control circuit 104, and generate an Enable signal Enable according to a corresponding control signal of the main control circuit 104. The clock signal generating module 105b is configured to generate a periodic clock signal clk according to a primary ON-time signal PD _ ON (i.e., Tonp) of the switching power supply and a peak current Ipk of the switching power supply. The counting module 105c is connected to the peak current sampling terminal CS, and configured to count the number of cycles of the first-type peak current Ipk1 continuously appearing in the switching power supply by accumulating the periodic clock signal clk at a high level or a low level under the control of the Enable signal Enable. The pulse generator is configured to generate a peak current switching signal Dynamic _ pulse according to the number of the cycles counted by the counting module 105v reaching a preset threshold number.
In this embodiment, the enable signal generating module 105a includes a first NOR gate NOR1, a second NOR gate NOR2, and a third NOR gate NOR3, the clock signal generating module 105b includes an and gate 4, and the counting module 105c includes three cascaded flip-flops TFF1 to TFF 3. Wherein an input terminal of the first NOR gate NOR1 receives a first signal Toff _2 μ sLH, another input terminal of the first NOR gate NOR1 is connected to an output terminal of the second NOR gate NOR2 and an input terminal of a third NOR gate NOR3, and an output terminal of the first NOR gate NOR1 is connected to a first input terminal of the second NOR gate NOR 2; a second input terminal of the second NOR gate NOR2 and another input terminal of the third NOR gate NOR3 are both connected to an initialization signal Init _ HL for initializing the dynamic monitoring circuit 105, and a third input terminal of the second NOR gate NOR2 is connected to a second signal PDON _ LEB; the output end of the third NOR gate NOR3 is connected with the asynchronous set end present of three flip-flops TFF 1-TFF 3, one input end of the and gate 4 is connected with a third signal PD _ ON, and the other input end of the and gate 4 is connected with a fourth signal Ipklow; the three flip-flops TFF 1-TFF 3 are connected in series (i.e. cascaded) in sequence, the clock terminal clk of the first stage flip-flop TFF1 is connected with the output terminal of the AND gate 4, the inverted output terminal Qb of the third stage flip-flop TFF3 is connected with the input terminal of the pulse generator P1, and the output terminal of the pulse generator P1 outputs a peak current switching signal Dynamic _ pulse. Referring to fig. 7 and 8, the first signal Toff _2 μ sLH is a high signal during a period from when the switching power supply enters the turn-off phase Toff to the end of the turn-off phase, the third signal PD _ ON is a primary side ON-time signal Tonp of the switching power supply, the second signal PDON _ LEB is a signal obtained by delaying the primary side ON-time signal Tonp (i.e., PD _ ON) for a predetermined time (e.g., 500ns), and the fourth signal Ipklow is a high signal when the peak current Ipk of the switching power supply is the first type peak current Ipk1 (the peak current Ipk of the switching power supply is smaller than a predetermined peak threshold). The third NOR gate NOR3 outputs an Enable signal Enable to the asynchronous reset terminals present of the three flip-flops TFF 1-TFF 3 so that the three flip-flops TFF 1-TFF 3 operate, the in-phase output terminal Q of the first stage flip-flop TFF1 outputs a signal Q1 to the clock terminal clk of the second flip-flop TFF2, the in-phase output terminal Q of the second stage flip-flop TFF2 outputs a signal Q2 to the clock terminal clk of the third stage flip-flop TFF3, and the in-phase output terminal Q of the third stage flip-flop TFF3 outputs a signal Q3 and an inverted output terminal Q3 b. Fig. 8 shows a timing chart of Vout, VFB, Ipk, Ipklow, PD _ ON, PDON _ LEB, Toff _2 μ sllh, Enable, Q1 to Q3, Q3b, and peak current switching signal Dynamic _ pulse.
The peak current control circuit 106 is configured to generate a peak current control signal (not shown) for switching the peak current Ipk of the switching power supply to a second type peak current Ipk2 according to the peak current switching signal Dynamic _ pulse, wherein the second type peak current Ipk2 is a peak current when the switching power supply is in a heavy load state, and the second type peak current Ipk2 is in a form of a full duty cycle and can be set to a maximum value of the peak current Ipk; the main control circuit 104 is connected to the dynamic monitoring circuit 105 and the peak current control circuit 106, and configured to control operations of the dynamic monitoring circuit 105 and the peak current control circuit 106, and adjust a peak current Ipk of the switching power supply to switch from a first type peak current Ipk1 (i.e., small Ipk) to a second type peak current Ipk2 (i.e., large Ipk) according to the peak current control signal, and output a control logic signal related to the second type peak current Ipk 2; the driving circuit 107 is connected to the main control circuit 104, and configured to output a driving signal according to the control logic signal to control on/off of a power switch of the switching power supply, so that the output voltage Vout of the switching power supply is raised.
The load state monitoring circuit 102 is connected to the main control circuit 104, and is configured to monitor whether a load state of the switching power supply is switched from a light load to a heavy load, and generate a count trigger signal when the load state is switched from the light load to the heavy load; the main control circuit 104 is configured to initialize the dynamic monitoring circuit 105 according to the count trigger signal, so that the dynamic monitoring circuit 105 starts to monitor the number of cycles in which the peak current Ipk1 of the first type continuously appears in the switching power supply.
The output voltage detection circuit 103 is connected between the main control circuit 105 and the secondary output voltage feedback terminal FB of the switching power supply, and the output voltage detection circuit 103 is configured to feed back a variation of the output voltage Vout of the secondary of the switching power supply to the main control circuit 104.
The reference voltage generating circuit 101 is connected between the main control circuit 104 and a primary side input voltage feedback terminal VCC (i.e., a control terminal of a primary side controller of the switching power supply, a power supply terminal VCC terminal), the reference voltage generating circuit 101 is configured to generate a corresponding reference voltage VREF according to a voltage VFB of the primary side input voltage feedback terminal and output the reference voltage VREF to the main control circuit 104, and the main control circuit 104 adjusts a peak current Ipk of the switching power supply to be switched from the first type peak current Ipk1 to the second type peak current Ipk2 based on the reference voltage VREF and the peak current control signal Dynamic _ pulse.
Referring to fig. 4-8, in the present embodiment, the Dynamic monitoring circuit 105 monitors the peak current Ipk of the switching power supply in real time, and when it is monitored that the pulse of the small Ipk continuously appears for 4 cycles (in other embodiments of the present invention, it may also continuously appear for 6 cycles) in the form of a full duty cycle (i.e. there is no Toff time), that is, when the number of cycles of the first kind of peak current continuously appearing on the switching power supply reaches a preset threshold number, it may be determined that the load state of the switching power supply is in a condition of switching from light load to heavy load, and at this time, the output voltage of the switching power supply drops, and further an effective peak current switching signal dynamicpulse is generated (for example, the signal is effective when the signal is high), the peak current control circuit 106 switches the peak current of the switching power supply to the second kind of peak current Ipk2 (i.e. a large peak current Ipk) according to the effective peak current switching signal dynamicpulse, and the main control circuit 104 outputs a corresponding control logic signal according to the adjusted peak current Ipk2 of the second type to control the power transistor (i.e. M1 in fig. 5) to be turned on within an allowable range, so that the transformer can provide more energy to compensate the output voltage drop, and the dynamic performance of the system is improved.
To better illustrate the effect of the switching power supply control circuit of the present embodiment on improving the dynamic response performance of the switching power supply, fig. 9 shows a timing comparison diagram of the adjustment of the output voltage when the switching power supply is switched from light load to heavy load between the conventional switching power supply control circuit shown in fig. 1 and the switching power supply control circuit of the present embodiment. Referring to fig. 9, it can be seen from fig. 9 that the conventional switching power supply control circuit outputs a voltage at the moment when Tsample is detected (V at the moment when Tsample is detected by FB voltage detection)FBVoltage proportional to the output voltage Vout) is lower than the reference voltage V preset thereinREFAt this time, the current small Ipk will be switched to large Ipk to make the output voltage Vout rise, but this process needs to go through tens or even twenty more pulses of small Ipk, i.e. from light load to heavy loadDuring the dynamic switching period (i.e. during the pulse period of tens of even more than twenty small ipks), the output voltage Vout will continue to drop, so the dynamic response performance is relatively poor; in the present embodiment, when the dynamic monitoring circuit 105 detects that the small Ipk (i.e. the first-class peak current Ipk1) continuously drops for 4 cycles, for example, it will switch to the large Ipk (i.e. the second-class peak current Ipk2), so that the output voltage Vout is quickly recovered to the normal value, i.e. during the dynamic switching from light load to heavy load, the output voltage Vout will be quickly raised only when dropping for 4 small Ipk, therefore, the switching power supply control circuit of the present embodiment improves the load dynamic response speed, and solves the problems in the prior art.
In addition, it should be noted that the design of the dynamic monitoring circuit shown in fig. 6 is only one specific embodiment of the present invention, but the technical solution of the present invention is not limited thereto, and the circuit design that can realize the core idea (i.e. dynamic detection mechanism) of the dynamic monitoring circuit all belongs to the scope of the protection of the present invention, wherein the core idea (i.e. dynamic detection mechanism) of the dynamic monitoring circuit is: when it is detected that the pulses of the small Ipk continuously output the threshold number, for example, 4 or 6 cycles in the form of the full duty (without Toff time), the system is considered to be in a switching dynamic mode of switching from light load to heavy load, and a subsequent series of operations are performed, including switching the small Ipk to the large Ipk, and simultaneously outputting the large Ipk in the form of the full duty.
Based on same utility model, please refer to fig. 5, an embodiment of the utility model provides a switching power supply system still, include power switch pipe M1 and as the switching power supply control circuit of improvement dynamic performance, power switch pipe M1's control end is connected to switching power supply control circuit's drive circuit 107's output, and when power switch pipe M1 was the MOS transistor, power switch pipe M1's control end was the grid of MOS transistor. The switching power supply system of the present embodiment further includes: the power supply comprises an input rectifying and filtering circuit, a transformer, an output rectifying and filtering circuit, an output voltage feedback circuit, a peak current sampling circuit and a power supply voltage sampling circuit. Wherein the transformer comprises a primary winding Lp of the transformer and a transformer auxiliaryThe transformer is mainly used for electric isolation and energy transmission of input and output. The input rectifying filter circuit is configured to convert an ac voltage signal Vac into a dc voltage signal (i.e., an input voltage) Vin to supply power to a primary winding Lp of the transformer. The output rectifying and filtering circuit is electrically connected with the secondary winding Ls of the transformer and is used for rectifying and filtering an output signal Vout of the secondary winding Ls. And the output voltage feedback circuit is connected between the auxiliary winding Laux and the switching power supply control circuit and is used for sampling and feeding back the output voltage Vout of the secondary winding Ls. The peak current sampling circuit is used for sampling the peak current, transmitting the sampling result to the dynamic monitoring circuit 105RC starting circuit for sampling a direct current pulse voltage signal (namely, input voltage) Vin and providing a working voltage V for the switching power supply control circuitCC。
In this embodiment, the input rectifying and filtering circuit includes a bridge rectifying circuit U1 and an input filtering capacitor C1. The output rectifying and filtering circuit comprises an output filtering capacitor C3 and a rectifying diode Ds. The output voltage feedback circuit comprises a power supply diode Daux and two feedback resistors Rfb1 and Rfb2 which are connected in series. The peak current sampling circuit includes a peak current sampling resistor Rcs. The RC start circuit includes a sampling resistor Rst and a filter capacitor C2. The specific circuit connections in the switching power supply system of the present embodiment include:
one end of the input filter capacitor C1 is connected to the output end of the bridge rectifier circuit U1 and one end of the primary winding Lp of the transformer, the other end of the input filter capacitor C1 is grounded, the ac power source Vac is rectified by the bridge rectifier circuit U1 and filtered by the input filter capacitor C1 to generate the input voltage Vin, and the input voltage Vin supplies power to the primary side of the transformer. The grid electrode of the power switch tube M1 is connected with the drive end DRI of the switch power supply control circuit, the drain electrode is connected with one end of the primary winding Lp of the transformer, the source electrode is grounded through a series peak current sampling resistor Rcs, and the common end of the source electrode of the power switch tube M1 and the peak current sampling resistor Rcs is connected with the peak current sampling end CS end of the switch power supply control circuit. The other end of the primary winding Lp of the transformer is connected to the output end of the bridge rectifier circuit U1 to receive the input Vin. Transformer deviceOne end of the auxiliary winding Laux is grounded by connecting two feedback resistors Rfb1 and Rfb2 connected in series to obtain a feedback voltage VFBFor realizing the feedback of the secondary output voltage Vout to the switching power supply control circuit, in particular, the feedback voltage V because the voltage of the transformer auxiliary winding Laux has a turn ratio relationship with the voltage of the transformer secondary winding LsFBThe common end of the two feedback resistors Rfb1 and Rfb2 is connected with the voltage feedback end FB end of the switching power supply control circuit, which can reflect the change of the secondary output voltage Vout. One end of the auxiliary winding Laux of the transformer is also connected with the anode of the power supply diode Daux, and the cathode of the power supply diode Daux is connected with the common end of the sampling resistor Rst and the filter capacitor C2, so that the input voltage Vin is sampled to obtain the voltage V required by the switching power supply control circuitCC，VCCOn one hand, the reference voltage generating circuit can be used as the working voltage required by the working of the switching power supply control circuit, and on the other hand, the reference voltage generating circuit in the switching power supply control circuit can be enabled to generate the reference voltage according to VCCAnd generates the reference voltage VREF. The other end of the transformer auxiliary winding Laux is grounded, and the common end of the sampling resistor Rst and the filter capacitor C2 is also connected with the VCC end of the switching power supply control circuit. One end of the secondary winding Ls of the output transformer is connected with the anode of the rectifier diode Ds, and the other end of the secondary winding Ls of the transformer is grounded. The output filter capacitor C3, the filter resistor R0 and the load RL are connected in parallel between the cathode of the rectifier diode Ds and the ground, the rectifier diode Ds is used for rectification and voltage stabilization, and the filter capacitor C3 and the filter resistor R0 which are connected in parallel are used for forming a filter circuit and filtering the output voltage Vout. The control circuit of the switching power supply obtains V according to the voltage feedback endFBV obtained from the power supply terminalCCObtaining V at the peak current sampling endCSAnd an internally preset reference voltage VREFThe peak current Ipk of the primary winding Lp is adjusted to generate a corresponding PFM signal to be output to the driving end DRI to control the on and off of the power switch tube M1, so that the energy is transmitted from the primary winding Lp of the transformer to the output end of the secondary winding Ls of the transformer, and the output voltage Vout is adjusted to rapidly respond to the switching of the load RL state of the secondary.
When the switching power supply system of this embodiment normally operates, one switching period T of the power switch M1 is actually divided into three phases: in the primary side on stage Tonp (Toff is the primary side on time), the secondary side on stage Tons (Tons is the secondary side on time), and the primary side and secondary side both off stage Toff (Toff is the off time), referring to fig. 5, the primary side winding Lp stores energy in the primary side on stage Tonp, the energy stored in the primary side winding Lp is transmitted to the secondary side circuit in the secondary side on stage Tons, and the secondary side current gradually decreases to 0.
The switching power supply system of this embodiment has adopted from this the utility model discloses an improve switching power supply control circuit of dynamic performance, dynamic response performance is better, especially when the load state switches from light load (for example for being not higher than 10% of maximum load) to heavy load (for example for being not lower than 90% of maximum load), can promote output voltage fast. The utility model discloses a switching power supply system can be the switching power supply system of arbitrary former limit control formula, for example charger, power adapter, LED drive power supply, wireless communication equipment, LCD screen power management, electronic refrigerator or ethernet power etc..
To sum up, the utility model discloses a switching power supply control circuit and switching power supply system, peak current Ipk that can real-time supervision switching power supply when detecting first kind of peak current (be little Ipk, do not have the peak current of Toff time, its pulse appears in succession with the form of full duty cycle) has gone out predetermined threshold value number (example) in succession+If the number of the ipks is 4, namely, the small Ipk continuously appears for 4 cycles), the system is considered to be in a switching dynamic mode of switching from a light load to a heavy load, and the small Ipk is immediately switched to the peak current of the second type (namely, the large Ipk, the pulse of which is output in the form of a full duty ratio), and in this state, the output voltage of the switching power supply is rapidly raised after dropping for only a threshold number of small Ipk times (for example, 4 cycles), so that the dynamic performance is optimized.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. A switching power supply control circuit for improving dynamic performance, comprising:
the dynamic monitoring circuit is used for monitoring the number of cycles of first-class peak current continuously generated by the switching power supply and generating a peak current switching signal when the monitored number of cycles reaches a preset threshold number, wherein the first-class peak current is the peak current of the switching power supply in a light load state, and the first-class peak current is smaller than a preset peak threshold and is generated in a full duty ratio mode;
the peak current control circuit is used for generating a peak current control signal for switching the peak current of the switching power supply into a second type of peak current according to the peak current switching signal, wherein the second type of peak current is the peak current of the switching power supply in a heavy load state;
the main control circuit is connected with the dynamic monitoring circuit and the peak current control circuit and is used for controlling the work of the dynamic monitoring circuit and the peak current control circuit, adjusting the peak current of the switching power supply to be switched into a second type of peak current according to the peak current control signal and outputting a control logic signal related to the second type of peak current; and
and the driving circuit is connected with the main control circuit and used for outputting a driving signal according to the control logic signal so as to control the on-off of a power switch tube of the switching power supply and lift the output voltage of the switching power supply.
2. The switching power supply control circuit of claim 1 wherein the second type of peak current occurs at full duty cycle.
3. The switching power supply control circuit of claim 1 wherein the dynamic monitoring circuit comprises:
the enabling signal generating module is connected with the main control circuit, is used for initializing according to the initialization signal of the main control circuit and generating an enabling signal according to the corresponding control signal of the main control circuit;
the clock signal generating module is used for generating a periodic clock signal according to a primary side conduction time signal of the switching power supply and the peak current of the switching power supply;
the counting module is used for performing accumulated counting on the periodic clock signals with high level or low level under the control of the enabling signal so as to monitor the number of periods of the first type of peak current continuously appearing on the switching power supply;
and the pulse generator is used for generating a peak current switching signal when the number of the cycles counted by the counting module reaches a preset threshold number.
4. The switching power supply control circuit according to claim 3, wherein the enable signal generation block comprises a first nor gate, a second nor gate and a third nor gate, the clock signal generation block comprises an and gate, and the counting block comprises a cascade of three flip-flops; wherein, an input terminal of the first nor gate receives a first signal, another input terminal of the first nor gate is connected with an output terminal of the second nor gate and an input terminal of a third nor gate, and an output terminal of the first nor gate is connected with a first input terminal of the second nor gate; the second input end of the second nor gate and the other input end of the third nor gate are both connected with an initialization signal for initializing the dynamic monitoring circuit, and the third input end of the second nor gate is connected with a second signal; the output end of the third NOR gate is connected with the asynchronous position setting ends of the three triggers, one input end of the AND gate is connected with a third signal, and the other input end of the AND gate is connected with a fourth signal; the clock end of the first stage trigger of the three triggers is connected with the output end of the AND gate, and the inverted output end of the third stage trigger is connected with the input end of the pulse generator; the first signal is a high signal in a time period from the time when the switching power supply enters the turn-off stage to the end of the turn-off stage, the third signal is a primary side on-time signal of the switching power supply, the second signal is a signal obtained by delaying the primary side on-time signal for a predetermined time, and the fourth signal is a high signal when the peak current of the switching power supply is smaller than the peak threshold.
5. The switching power supply control circuit according to any one of claims 1 to 4, further comprising a load status monitoring circuit connected to the main control circuit for monitoring whether the load status of the switching power supply is switched from light load to heavy load, and generating a count trigger signal when the load status is monitored to be switched from light load to heavy load; the main control circuit is used for initializing the dynamic monitoring circuit according to the counting trigger signal so that the dynamic monitoring circuit starts to monitor the number of cycles of continuous occurrence of the first type of peak current in the switching power supply.
6. The switching power supply control circuit according to any one of claims 1 to 4, further comprising an output voltage detection circuit connected between the main control circuit and a secondary side output voltage feedback terminal of the switching power supply, wherein the output voltage detection circuit is configured to feed back a variation of the output voltage of the secondary side of the switching power supply to the main control circuit.
7. The switching power supply control circuit according to any one of claims 1 to 4, further comprising a reference voltage generating circuit connected between the main control circuit and a primary side input voltage feedback terminal of the switching power supply, wherein the reference voltage generating circuit is configured to generate a corresponding reference voltage according to a voltage of the primary side input voltage feedback terminal and output the reference voltage to the main control circuit, and the main control circuit is configured to adjust the peak current of the switching power supply to switch from the first type peak current to the second type peak current based on the reference voltage and the peak current control signal.
8. A switching power supply system, characterized by comprising a power switch tube and the switching power supply control circuit for improving dynamic performance according to any one of claims 1 to 7, wherein the control end of the power switch tube is connected with the drive circuit of the switching power supply control circuit.
9. The switching power supply system according to claim 8, further comprising:
the input rectification filter circuit is used for converting the alternating voltage signal into a direct voltage signal;
the transformer is provided with a primary winding, a secondary winding and an auxiliary winding which are coupled with the input rectifying and filtering circuit, and a driving circuit in the switching power supply control circuit is coupled to the primary winding;
the output rectifying and filtering circuit is electrically connected with the secondary winding and is used for rectifying and filtering the output signal of the secondary winding;
and the output voltage feedback circuit is connected between the auxiliary winding and the switching power supply control circuit and is used for sampling and feeding back the output voltage of the secondary winding.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110445404A (en) * | 2019-09-09 | 2019-11-12 | 上海新进芯微电子有限公司 | The switching power source control circuit and method and switch power supply system of improvement dynamic property |
| CN113437870A (en) * | 2021-07-13 | 2021-09-24 | 上海艾为电子技术股份有限公司 | DC-DC converter, mode switching method and circuit thereof, and electronic device |
| TWI789265B (en) * | 2022-03-07 | 2023-01-01 | 群聯電子股份有限公司 | Over-voltage protection device, memory storage device and over-voltage protection method |
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2019
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110445404A (en) * | 2019-09-09 | 2019-11-12 | 上海新进芯微电子有限公司 | The switching power source control circuit and method and switch power supply system of improvement dynamic property |
| CN113437870A (en) * | 2021-07-13 | 2021-09-24 | 上海艾为电子技术股份有限公司 | DC-DC converter, mode switching method and circuit thereof, and electronic device |
| CN113437870B (en) * | 2021-07-13 | 2023-09-22 | 上海艾为电子技术股份有限公司 | DC-DC converter, mode switching method and circuit thereof, and electronic device |
| TWI789265B (en) * | 2022-03-07 | 2023-01-01 | 群聯電子股份有限公司 | Over-voltage protection device, memory storage device and over-voltage protection method |
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