CN210297524U - Active dummy load, switch power converter - Google Patents

Abstract

An active dummy load, switching power converter includes a period detection circuit and an active load. The period detection circuit receives the period information signal, outputs an active load control signal to prompt whether the working condition of the active load is met or not, receives the active load control signal, selectively accesses between the power supply voltage and the system ground when the active load control signal prompts that the working condition of the active load is met, and disconnects with the power supply voltage and the system ground when the active load control signal prompts that the working condition of the active load is not met. The active dummy load can be accurately accessed according to the requirement, and the working efficiency is improved.

Description

Active dummy load, switch power converter

Technical Field

The utility model relates to an electronic circuit, concretely relates to active dummy load circuit, switching power supply converter.

Background

Under the background that the importance of environmental protection and energy conservation is continuously promoted at present, the requirement on the power supply efficiency is higher and higher at present. The current switching power supply mainly depends on a feedback loop to control the load and the output change in the working process so as to ensure the stability of the output.

When a load of a switching power supply is in a standby state, the energy requirement for each cycle of the switching power supply is small, and in order to improve the efficiency of the switching power supply in this scenario, a frequently-used method in the prior art is to adjust the operating frequency of the switching power supply, so that the switching power supply operates in a Pulse Frequency Modulation (PFM) mode. When the load is in a standby state, the working frequency of the switching power supply is correspondingly reduced, and the working period is prolonged so as to adapt to the output requirement of the current load.

However, when the switching power supply adopting PFM mode control faces different application scenarios, it is often necessary to set a maximum switching period (i.e. minimum switching frequency) for various reasons. For example, for a high-side switching type buck converter and a primary-side control type flyback converter, a minimum switching frequency needs to be set in order to ensure the transient response capability of a feedback loop to the output end of a power supply. When the demand of the load on the energy is less than the energy output in the maximum switching period, the output voltage is gradually increased due to the fact that the energy cannot be consumed on the output end of the switching power supply, and the power supply system fails. To avoid this extreme situation, a common approach is to switch in a dummy load (dummy load) at the output. Under the condition that the load is extremely low or even zero, the switch power supply can consume redundant energy at the output end in time, and the output stability is ensured.

However, in the case of a normal load, the presence of a dummy load may additionally consume energy, so that the efficiency of the power supply system is reduced.

SUMMERY OF THE UTILITY MODEL

An active dummy load, switching power converter is presented to address one or more problems in the prior art.

One aspect of the present invention provides an active dummy load, comprising a period detection circuit and an active load, wherein the period detection circuit receives a period information signal, and outputs at least one active load control signal for controlling the active load according to a period or frequency information contained in the period information signal, wherein the active load control signal indicates whether an active load working condition is satisfied; and the active load receives the at least one active load control signal, selectively switches in between the power supply voltage and the system ground when the at least one active load control signal prompts that the active load working condition is met, and switches out from the power supply voltage and the system ground when all the active load control signals prompt that the active load working condition is not met.

In one embodiment, the cycle detection circuit includes: the timer is used for timing the length of a single period according to the period information signal and outputting a timing signal; and the first end of the comparator receives the timing signal, the second end of the comparator receives a timing reference signal, and the output end of the comparator outputs the active load control signal. In one embodiment, the cycle detection circuit may further include a trigger circuit, receiving and outputting a cycle trigger signal according to the cycle information signal, the cycle trigger signal being used to prompt the start of a cycle; the timer comprises at least one timing unit, the timing unit comprises a timing current source, a timing switch and a timing capacitor, the output end of the timing current source is coupled to the first end of the timing switch and the first end of the timing capacitor, the timing switch receives the periodic trigger signal and performs switching according to the periodic trigger signal, the second end of the timing switch is coupled with the second end of the timing capacitor and then grounded, and the first end of the timing capacitor outputs the timing signal.

In one embodiment, the cycle detection circuit has a plurality of groups of cycle detection units connected in parallel, each cycle detection unit outputs an active load control signal, wherein the active load access conditions represented by each active load control signal are different, the active load has a plurality of load units, and each load unit is correspondingly controlled by one active load control signal.

In one embodiment, each of the cycle detecting units includes: the timer is used for timing the single period length represented by the period information signal and outputting a timing signal; and a comparator, wherein a first end of the comparator receives the timing signal, a second end of the comparator receives a timing reference signal, and an output end of the comparator outputs the active load control signal, wherein each timing reference signal in each period detection unit is different from each other.

In one embodiment, the active load comprises at least one controlled bleed current source coupled between the supply voltage and the system ground, the bleed current source outputting a current of zero when the active load control signal indicates that the active load operating condition is not met, and the bleed current source outputting a bleed current when the active load control signal indicates that the active load operating condition is met.

In one embodiment, the period detection circuit includes a frequency sensing circuit and a signal processing circuit, wherein the frequency sensing circuit receives the period information signal, detects the frequency information included in the period information signal, and outputs a digitized frequency value, and the signal processing circuit receives the digitized frequency value output by the frequency sensing circuit, compares the digitized frequency value with a preset value, and outputs the result as the active load control signal.

The utility model discloses another aspect provides a switching power supply system, including the switching power supply controller, output a switching power supply control signal, the switch converter, accept the control of the switching power supply control signal, convert the input voltage into output voltage; an isolation diode having an anode receiving the output voltage; the energy storage capacitor is connected between the cathode of the isolation diode and the system ground, and the voltage on the energy storage capacitor is the power supply voltage; and the active dummy load receives a periodic information signal, wherein the periodic information signal is from the switching power supply controller or the switching converter, and the active dummy load determines whether to be connected between the power supply voltage and the system ground according to the periodic information signal.

In another aspect, the present invention provides a switching power supply system, which includes a switching power supply controller outputting a switching power supply control signal; the isolated switch converter is controlled by the switch power supply control signal and converts an input voltage into an output voltage, wherein the isolated switch converter is provided with a main transformer which comprises a primary winding, a secondary winding and an auxiliary winding, the primary winding receives the input voltage, and the secondary winding provides energy for the output voltage; an isolation diode having an anode connected to one end of the auxiliary winding; the active dummy load receives a periodic information signal, wherein the periodic information signal is from the switching power supply controller or the switching converter, and the active dummy load determines whether to be connected between the power supply and the system ground according to the periodic information signal.

The beneficial effects of the utility model are that, to active dummy load, because the initiative load only when initiative load control signal instructs to satisfy initiative load operating condition, just access to between mains voltage is with system ground, and through cycle detection circuitry, can be through the opportunity to the judgement of load condition, very accurate control initiative load access circuit. Under the working condition that the active load is not required to be connected, the active load is not connected between the power supply voltage and the system ground in the whole working period, so that unnecessary energy consumed by the active load can be effectively reduced.

Drawings

Throughout the following drawings, the same reference numerals indicate the same, similar or corresponding features or functions.

Fig. 1 shows a schematic structural diagram of an active dummy load circuit 100 according to an embodiment of the present invention;

fig. 2 shows a circuit schematic of the cycle detection circuit 101 according to an embodiment of the present invention;

fig. 3 shows a schematic circuit diagram of an active load 102 in accordance with an embodiment of the present invention;

fig. 4 is a schematic circuit diagram of an active dummy load 400 according to another embodiment of the present invention;

fig. 5 is a schematic circuit diagram of an active dummy load 500 according to another embodiment of the present invention;

fig. 6 is a schematic diagram of a switching power supply system 600 using an active dummy load according to an embodiment of the present invention;

fig. 7 is a schematic diagram of a switching power supply system 700 using an active dummy load according to another embodiment of the present invention.

Detailed Description

Specific embodiments of the present invention will be described in detail below, and it should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the invention. In other instances, well-known circuits, materials, or methods have not been described in detail in order to avoid obscuring the present invention.

Throughout the specification, reference to "one embodiment," "an embodiment," "one example," or "an example" means: the particular features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment," "in an embodiment," "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Like reference numerals refer to like elements. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. Thus, a first element discussed below could be termed a second element without departing from the teachings of the present inventive concept. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Fig. 1 shows a schematic structural diagram of an active dummy load circuit 100 according to an embodiment of the present invention. As shown in fig. 1, the active dummy load circuit 100 includes a period detection circuit 101 and an active load 102.

The period detection circuit 101 receives the period information signal FS, and outputs an active load control signal ALC to prompt whether the working condition of the active load is satisfied or not according to the period or frequency information contained in the period information signal FS, where the active load control signal ALC is used to control the active load 102. The active load 102 receives an active load control signal ALC that is selectively coupled between the supply voltage VCC and the system ground GND when the active load control signal ALC indicates that the active load operating condition is satisfied, and decoupled from the supply voltage VCC and the system ground GND when the active load control signal ALC indicates that the active load operating condition is not satisfied.

Here and in the following, the period information signal FS is meant for any signal that contains information that embodies the operating frequency or period of the switching power supply. For example, the period information signal FS may be a switching control signal for controlling a main switching tube of the switching power supply, and in this case, the period information signal FS may be a square wave signal. The period or frequency information included in the period information signal FS is, in this document, period or frequency information that can particularly represent the size of the working load of the switching power supply corresponding to the period information signal FS. For convenience, the embodiment of the present invention will be described below by taking the switching control signal with the periodic signal FS as a square wave pattern as an example. However, it can be understood by those skilled in the art that the periodic information signal FS is not limited to the square wave type switching control signal, and in other embodiments, for example, the output voltage signal, the output current signal, the internal clock signal, etc. of the switching power supply can be used as the periodic information signal FS to achieve the purpose of the present invention.

For the active dummy load 100, since the active load 102 is only connected between the power supply voltage VCC and the system ground when the active load control signal ALC indicates that the active load operating condition is satisfied, the timing for connecting the active load 102 to the circuit can be controlled very accurately through the determination of the load condition by the period detection circuit 101. Under the working condition that the active load 102 is not required to be connected, the active load 102 is not connected between the power supply voltage VCC and the system ground GND in the whole working period, so that unnecessary energy consumption of the active load 102 can be effectively reduced.

Fig. 2 shows a circuit schematic of the cycle detection circuit 101 according to an embodiment of the present invention. As shown in fig. 2, the period detection circuit 101 may include a period trigger circuit 1011, a timer 1012, and a comparator 1013.

The period trigger circuit 1011 receives the period information signal FS and outputs a period trigger signal TS according to the period information signal FS. The period trigger signal TS is used to prompt the start of a single switching period. In one embodiment, the periodic trigger circuit 101 is a one-shot circuit formed by a differentiator. For example, when the period information signal FS is a square wave signal, it may be arranged that a rising edge or a falling edge of the period information signal FS triggers the one-shot circuit to output a single pulse signal as the period trigger signal TS. It will be appreciated by those skilled in the art that although in the illustrated embodiment the period trigger signal TS is a single pulse signal representing the start of a complete period of the period information signal FS, the form of the period trigger signal TS is not limited to a single pulse signal, and in other embodiments, other suitable circuits may be employed to generate the period trigger signal TS having a different waveform form to represent the start of a complete period of the period information signal FS.

In some embodiments, the period detecting circuit 101 may not include the period triggering circuit 1011, but directly receive the period information signal FS from the timer 1012, and determine the starting point of the single period according to the waveform characteristics, such as the rising edge or the falling edge, of the period information signal FS.

Continuing with the embodiment shown in fig. 2, in the cycle detecting circuit 101, the timer 1012 is composed of at least one timing unit, and is used for counting a single switching cycle and outputting a timing signal TC. In the illustrated embodiment, the timing unit includes a timing current source 1023, a timing switch 1024 and a timing capacitor 1025, an output terminal of the timing current source 1023 is coupled to a first terminal of the timing switch 1024 and a first terminal of the timing capacitor 1025, and the timing switch 1024 receives a periodic trigger signal TS and performs switching according to the periodic trigger signal TS. A second terminal of timing switch 1024 is coupled to a second terminal of timing capacitor 1025 and then coupled to ground. A first terminal of the comparator 1022 is coupled to the first terminal of the timing capacitor 1025 and receives the timing signal TC, a second terminal of the comparator 1022 receives the timing reference signal TREF, and an output terminal of the comparator 1022 outputs the active load control signal ALC.

When the period trigger signal TS indicates the beginning of a single period in the period information signal with a short pulse, the timing switch 1024 is closed to discharge the timing capacitor 1025 and is opened again, so that the timer 1012 returns to zero. Thereafter, timing current source 1023 begins to charge timing capacitor 1025. If the period corresponding to the period information signal FS is greater than a period threshold, the timing signal TC output by the corresponding timing capacitor 1025 gradually increases from small to large until it is greater than the timing reference signal TREF, and the timing switch 1024 still does not reset the voltage on the timing capacitor. At this time, the active load control signal ALC output by the output terminal of the comparator 1022 jumps, which prompts the active load 102 to meet the working condition. When the period corresponding to the period information signal FS is smaller than the period threshold, the timing signal output by the timing capacitor 1025 enters a new period before the timing signal is not larger than the timing reference signal TREF, and the timing switch 1024 resets the voltage on the timing capacitor 1025 under the action of the period trigger signal TS, so that the active load control signal ALC output by the output terminal of the comparator 1022 prompts that the active load 102 does not meet the working condition.

Those skilled in the art will appreciate that the conditions that trigger the active load control signal ALC to prompt the active load to operate in the illustrated embodiment are exemplary and not limiting, and in other embodiments, the active load control signal ALC may have different prompting conditions depending on the particular scenario. The person skilled in the art can determine the detection mode of the period detection circuit 101 to the period and the prompting condition of the corresponding active load control signal ALC according to the specific application scene requirement to the active load, which is not limited by the present invention.

The active load 102 receives the active load control signal ALC and is selectively coupled between the supply voltage VCC and the system ground GND when the active load control signal ALC indicates that the active load operating condition is satisfied, and is decoupled from the supply voltage VCC and the system ground GND when the active load control signal ALC indicates that the active load operating condition is not satisfied. Fig. 3 shows a schematic circuit diagram of the active load 102 according to an embodiment of the present invention. As shown in fig. 3, the active load 102 is a controlled bleeder (blanking) current source coupled between the supply voltage VCC and the system ground GND. The active load 102 receives the active load control signal ALC, and when the active load control signal ALC indicates that the operating condition of the active load is not satisfied, the current output by the bleeder current source is zero, which is equivalent to that the active load 102 is not connected to the circuit. When the active load control signal ALC indicates that the active load working condition is satisfied, the bleeder current source outputs a bleeder current Ib, which is equivalent to the active load 102 accessing the circuit. Typically, the value of the bleed current Ib may be 1mA-100 mA.

Those skilled in the art will appreciate that the active load 102 can be connected between the supply voltage VCC and the system ground GND by other types of suitable loads, such as resistors, through switches controlled by the active load control signal ALC, to achieve similar effects.

Those skilled in the art will appreciate that in other embodiments, the period detection circuit 101 may time a single period or a portion of a single period of the period information signal in any suitable manner to determine whether the active load access condition is met. The active load control signal ALC instructs the active load 102 to switch in the load only after the timing reaches a threshold in a specific period, further reducing unnecessary energy consumption.

Further, in one embodiment, the active load control signal ALC output by the period detection circuit 101 may be an analog signal. The value of the active load control signal ALC further prompts the size of the accessed active load. When the active load is a bleeding current source, the bleeding current source is a variable current source, and the value of the output bleeding current Ib is determined according to the value of the active load control signal ALC, so that the active load 102 can finely adjust the size of the dummy load connected to the circuit according to the specific external load actual condition and/or application environment, and the relationship between the transient response performance and the working efficiency is more accurately balanced.

Fig. 4 is a schematic circuit diagram of an active dummy load 400 according to another embodiment of the present invention. The period detection circuit 401 includes a plurality of groups of period detection units connected in parallel, each of the period detection units outputs an active load control signal ALC1, ALC2, … …, ALCn, wherein the active load access conditions represented by each of the active load control signals are different. In the illustrated embodiment, the circuit configuration of the cycle detecting unit is the same as that of the cycle detecting circuit 201 shown in fig. 2, and includes a plurality of timer units 1012 and a corresponding plurality of comparators 1022. In the illustrated embodiment, the timing reference signals TREF1, TREF2, … …, TREFn in each comparator unit 1022 are different, and the timing signals TC output by the plurality of timer units are the same, so that the active load control signals ALC1, ALC2, … …, ALCn output by each comparator have different trip conditions, i.e., the active load access conditions represented by ALC1, ALC2, … … ALCn are different. In another embodiment, the capacitance of the timing capacitor of 1022 in each timer unit or the output current of the timing current source are different, so that the timing signals TC output by the plurality of timer units are different, and the same timing reference signal TREF is uniformly used by the comparator units 1022, which also enables different active load access conditions represented by ALC1, ALC2, … … ALCn. The active load 402 comprises a plurality of controlled bleeder current sources connected in parallel, each controlled by an active load control signal ALC1, ALC2, … …, ALCn, each respectively starting to output a bleeder current Ib1, Ib2, … … Ibn when respective access conditions are met. The bleeder currents Ib1, Ib2, … … and Ibn output by each bleeder current source may be the same or different, so that the active load 402 may fine-tune the size of the dummy load of the access circuit according to the actual condition and/or application environment of the specific external load, thereby more accurately balancing the relationship between the transient response performance and the working efficiency.

Fig. 5 is a schematic circuit diagram of an active dummy load 500 according to another embodiment of the present invention. As shown in fig. 5, the active dummy load 500 includes a period detection circuit 501 having a frequency sensing circuit 5011 and a signal processing circuit 5012. The frequency sensing circuit 5011 receives the period information signal FS, detects frequency information included in the period information signal FS, and outputs a digitized frequency value DF. The frequency sensing circuit 5011 can adopt a known frequency detection circuit structure in the prior art, and can all achieve the corresponding technical purpose, which is not described herein again. The signal processing circuit 5012 may be a digital comparator, which receives the digitized frequency value DF output by the frequency sensing circuit 5011, compares the digitized frequency value DF with a preset value, and outputs the result as the active load control signal ALC. For example, when the digitized frequency value is lower than the preset value, the active load control signal ALC output by the digital comparator is at a high level, which indicates that the active load access condition is satisfied, so as to access the active load 502 between the power supply voltage VCC and the system ground GND. When the digitized frequency value is lower than the preset value, the active load control signal ALC output by the digital comparator is at a low level, which indicates that the active load access condition is not satisfied, and the active load 502 is disconnected from the power supply voltage VCC and the system ground GND.

Thus, the digitized cycle detection circuit 500 can accurately and quickly detect the current corresponding load state according to the cycle information signal FS, thereby accurately controlling the connection and disconnection of the active load 502.

Fig. 6 is a schematic diagram of a switching power supply system 600 using an active dummy load according to an embodiment of the present invention. As shown in fig. 6, the switching power supply system 600 includes a switching power supply controller 601 that outputs a switching control signal SW. The switching power supply controller 601 may adopt any switching power supply control method commonly used in the prior art, and the present invention is not limited herein. The switching converter 602 receives a switching control signal SW output from the switching power supply controller 601, and converts the input voltage VIN into an output voltage VOUT. An isolation diode 603 has an anode coupled to the output voltage VOUT and a cathode connected to an energy storage capacitor Cs. The energy storage capacitor Cs is connected between the cathode of the isolation diode 603 and the system ground GND, and the voltage across the energy storage capacitor Cs is the power supply voltage VCC. The active dummy load 604 receives the period information signal FS, and determines whether to be connected between the power source VCC and the system ground GND according to the period information signal FS.

The period information signal FS is derived from the switching power supply controller 601 or the switching converter 602, and contains the duty cycle or frequency information of the switching power supply system 600. The active dummy load 604 may have the circuit structure of any of the embodiments of the active dummy load described above. In the illustrated embodiment, the period information signal FS is the switch control signal SW.

Specifically, in the embodiment shown in fig. 6, the switching converter 602 is a non-isolated Buck (Buck) converter, and the switching power supply controller 601 is a non-isolated Buck converter. Having a main switch tube 6021 that receives a switch control signal SW, a freewheeling diode 6022, an output inductor 6023, and an output capacitor 6024. In other embodiments, the switching converter 602 may be of any suitable isolated or non-isolated switching power supply topology, including but not limited to a boost (boost) converter, buck-boost (buck-boost) converter, flyback (fly-back) converter, forward (forward) converter, half-bridge (half-bridge) converter, full-bridge (full-bridge) converter or other resonant/quasi-resonant converter topologies, such as phase-shifted full-bridge, resonant half-bridge LLC, active clamping forward/flyback, and so on.

Fig. 7 is a schematic diagram of a switching power supply system 700 using an active dummy load according to another embodiment of the present invention. As shown in fig. 7, the switching power supply system 700 includes a switching power supply controller 701 outputting a switching control signal SW, and an isolated switching converter 702 receiving the control of the switching control signal SW output by the switching power supply controller 701 to convert an input voltage VIN into an output voltage VOUT. The isolated switching converter 702 has a main transformer 703 including a primary winding 7031, a secondary winding 7032, and an auxiliary winding 7033. The primary winding 7031 receives an input voltage VIN, the secondary winding 7032 supplies an output voltage VOUT, the auxiliary winding 7033 is connected to an anode of an isolation diode 704, and a cathode of the isolation diode is connected to an energy storage capacitor Cs. The voltage across the storage capacitor Cs is the supply voltage VCC. The active dummy load 705 receives the period information signal FS, and determines whether to be connected between the power source VCC and the system ground GND according to the period information signal FS.

Similarly, the period information signal FS is derived from the switching power supply controller 701 or the switching converter 702 and contains the duty period or frequency information of the switching power supply system 700. The active dummy load 705 may have the circuit structure of any of the embodiments of the active dummy load described above. In the illustrated embodiment, the period information signal FS is the switch control signal SW.

In one embodiment, the isolated switching converter 702 is a primary control type isolated flyback converter, and the switching power supply controller 701 is a primary control type flyback controller. For example, in the illustrated embodiment, a first terminal of the primary winding 7031 receives the input voltage VIN, a second terminal of the primary winding is coupled to a first terminal of the main switch 7021, a control terminal of the main switch 7021 receives the switch control signal SW, and is controlled to be turned on and off by the switch control signal SW, and a second terminal of the main switch 7021 is coupled to the primary ground PGND. The secondary winding 7032 has a first terminal coupled to the anode of the freewheeling diode 7022, a second terminal connected to the secondary ground SGND, and an output capacitor 7023 coupled between the cathode of the freewheeling diode 7022 and the secondary ground SGND to provide the output voltage VOUT.

Those skilled in the art will appreciate that isolated switching converter 702 is not limited to the primary side controlled flyback converter in the illustrated embodiment, and any isolated switching converter topology commonly found in the art may be used, such as a half-bridge converter, a forward converter, an isolated buck converter, an isolated boost converter, etc., without limitation.

While the present invention has been described with reference to several exemplary embodiments, it is understood that the terminology used is intended to be in the nature of words of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

Claims (11)

1. An active dummy load comprising a cycle detection circuit and an active load, wherein:

the period detection circuit receives a period information signal, and outputs at least one active load control signal for controlling an active load according to period or frequency information contained in the period information signal, wherein the active load control signal prompts whether the working condition of the active load is met;

and the active load receives the at least one active load control signal, selectively switches in between the power supply voltage and the system ground when the at least one active load control signal prompts that the active load working condition is met, and switches out from the power supply voltage and the system ground when all the active load control signals prompt that the active load working condition is not met.

2. The active dummy load of claim 1, wherein the cycle detection circuit comprises:

the timer is used for timing the length of a single period according to the period information signal and outputting a timing signal;

and the first end of the comparator receives the timing signal, the second end of the comparator receives a timing reference signal, and the output end of the comparator outputs the active load control signal.

3. An active dummy load according to claim 2, wherein:

the cycle detection circuit also comprises a trigger circuit which receives and outputs a cycle trigger signal according to the cycle information signal, wherein the cycle trigger signal is used for prompting the start of a cycle;

the timer comprises at least one timing unit, the timing unit comprises a timing current source, a timing switch and a timing capacitor, the output end of the timing current source is coupled to the first end of the timing switch and the first end of the timing capacitor, the timing switch receives the periodic trigger signal and performs switching according to the periodic trigger signal, the second end of the timing switch is coupled with the second end of the timing capacitor and then grounded, and the first end of the timing capacitor outputs the timing signal.

4. The active dummy load according to claim 1, wherein the period detection circuit has a plurality of sets of period detection units connected in parallel, each period detection unit outputting an active load control signal, wherein each active load control signal represents different active load access conditions, the active load has a plurality of load units, and each load unit is controlled by one active load control signal.

5. The active dummy load of claim 4, wherein each of the cycle detection units comprises:

the timer is used for timing the single period length represented by the period information signal and outputting a timing signal;

a comparator, a first end of the comparator receives the timing signal, a second end of the comparator receives a timing reference signal, and an output end of the comparator outputs the active load control signal

Wherein each timing reference signal in each of the cycle detecting units is different.

6. The active dummy load of claim 1, wherein the active load comprises at least one controlled bleed current source coupled between the power supply voltage and the system ground, the bleed current source outputting a current of zero when the active load control signal indicates that an active load operating condition is not met, and the bleed current source outputting a bleed current when the active load control signal indicates that an active load operating condition is met.

7. The active dummy load according to claim 1, wherein the period detection circuit comprises a frequency sensing circuit and a signal processing circuit, wherein the frequency sensing circuit receives the period information signal, detects the frequency information contained in the period information signal, and outputs a digitized frequency value, and the signal processing circuit receives the digitized frequency value output by the frequency sensing circuit, compares the digitized frequency value with a predetermined value, and outputs the result as the active load control signal.

8. A switching power converter comprising:

the switching power supply controller outputs a switching power supply control signal;

the switching converter is controlled by the switching power supply control signal and converts input voltage into output voltage;

an isolation diode having an anode receiving the output voltage;

the energy storage capacitor is connected between the cathode of the isolation diode and the system ground, and the voltage on the energy storage capacitor is the power supply voltage;

an active dummy load according to any of claims 1-7 receiving a periodic information signal from said switching power supply controller or said switching converter, said active dummy load determining whether to switch between said supply voltage and said system ground based on said periodic information signal.

9. The switching power converter of claim 8, wherein the switching converter is a non-isolated buck converter and the switching power controller is a non-isolated buck converter controller.

10. A switching power converter comprising:

the switching power supply controller outputs a switching power supply control signal;

the isolated switch converter is controlled by the switch power supply control signal and converts an input voltage into an output voltage, wherein the isolated switch converter is provided with a main transformer which comprises a primary winding, a secondary winding and an auxiliary winding, the primary winding receives the input voltage, and the secondary winding provides energy for the output voltage;

an isolation diode having an anode connected to one end of the auxiliary winding;

the energy storage capacitor is connected between the cathode of the isolation diode and the system ground, and the voltage on the energy storage capacitor is the power supply voltage; and

an active dummy load according to any of claims 1-7 receiving a periodic information signal from said switching power supply controller or said switching converter, said active dummy load determining whether to switch between said supply voltage and said system ground based on said periodic information signal.

11. The switching power converter as claimed in claim 10, wherein the isolated switching converter is a primary-side controlled flyback switching converter and the switching power controller is a primary-side controlled flyback switching power controller.

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