Switching power supply with active dummy load and dummy load control method thereof

Abstract

The application relates to the technical field of switching power supplies, in particular to a switching power supply with an active dummy load and a dummy load control method thereof, wherein the input end of a boost module and the output end of a dimming output module are electrically connected, the output end of the boost module is electrically connected with the positive electrode of an output capacitor of a PFC module through a linear voltage stabilizing module; a controller is electrically connected with the input end of the boost module through an input detection module to obtain an input voltage; the controller is electrically connected with the output end of the boost module through an output detection module to obtain an output voltage; the boost module is provided with an active switch which is electrically connected with the controller to be controlled; the controller is preset with a consumed current, the controller calculates the on time and the off time of the active switch to form a PWM signal to control the active switch to work; the problem that a resistor type dummy load cannot constantly consume a preset current value under the condition that the output voltage changes and finally cannot realize lower dimming is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, in particular to a switching power supply with active dummy load and a dummy load control method thereof. BACKGROUND

[0002] Conventional switching power supply, generally dimming to for example 10mA cannot be adjusted down, so it is necessary to set a dummy load on the output end to consume output current, in order to achieve the purpose of lower dimming range. Conventional switching power supply usually uses resistance as a dummy load to passively consume output power, but based on the output voltage in a range, so the energy consumed by the resistance is different when the output maximum voltage Vmax and the output minimum voltage Vmin, if Vmax and Vmin difference is relatively large (i.e. in the application of wide output voltage range), the current consumed is relatively large, which cannot constant consume preset current value under the condition of output voltage change, and finally cannot realize lower dimming. SUMMARY

[0003] In view of the above defects, the purpose of the present application is to provide a switching power supply with active dummy load and a dummy load control method thereof, which solves the problem that the resistance type dummy load cannot constant consume preset current value under the condition of output voltage change, and finally cannot realize lower dimming.

[0004] To achieve this purpose, the present application adopts the following technical scheme:

[0005] A switching power supply with active dummy load, comprising a PFC module, a dimming output module and a controller; further comprising a boost module, a linear voltage stabilizing module, an input detection module and an output detection module; the input end of the boost module and the output end of the dimming output module are electrically connected, and the output end of the boost module is electrically connected with the positive electrode of the output capacitor of the PFC module through the linear voltage stabilizing module;

[0006] The controller is electrically connected with the input end of the boost module through the input detection module, and the input voltage is obtained ; the controller is electrically connected with the output end of the boost module through the output detection module, and the output voltage is obtained ;

[0007] The boost module is provided with an active switch, which is electrically connected with the controller for control; the controller is preset with a consumption current , and the controller calculates the on time and the off time of the active switch by the consumption current , the input voltage and the output voltage , and controls the active switch according to the on time and the off time. and the turn-off time The PWM signal controls the active switch to work.

[0008] Further, the boost module comprises a capacitor CE10, a diode D22, an inductor L12 and a capacitor C50; the capacitor C50 is used as an input terminal of the boost module, a cathode of the diode D22 is used as an output terminal of the boost module, and one end and the other end of the capacitor C50 are electrically connected with the positive output terminal and the negative output terminal of the dimming output module respectively;

[0009] The positive terminal of the capacitor CE10 and the cathode of the diode D22 are electrically connected, the anode of the diode D22 and one end of the inductor L12 are electrically connected, the other end of the inductor L12 and one end of the capacitor C50 are electrically connected, and the other end of the capacitor C50 and the negative terminal of the capacitor CE10 are electrically connected.

[0010] The active switch is coupled between one end of the inductor L12 and the other end of the capacitor C50.

[0011] Further, the linear voltage stabilizing module comprises a passive switch and a self-driving module; the output terminal of the boost module is electrically connected with the positive terminal of the output capacitor of the PFC module through the passive switch, and the self-driving module is coupled between the output terminal of the boost module and the passive switch.

[0012] When the active switch is turned off under the control of the controller, the boost module works to increase the voltage output to the self-driving module, and the self-driving module drives the passive switch to be turned on.

[0013] Further, the self-driving module comprises a resistor R124, a resistor R125, a resistor R126, a resistor R127, a resistor R128 and a comparator U12; one end of the resistor R124 is electrically connected with the output terminal of the boost module; the other end of the resistor R124 is connected with the GND ground terminal after the resistor R125 and the resistor R126 are connected in series in sequence; the common connection point of the resistor R125 and the resistor R126 is electrically connected with the positive input terminal of the comparator U12.

[0014] The power supply voltage is connected with the GND ground terminal through the resistor R127 and the resistor R128; the common connection point of the resistor R127 and the resistor R128 is electrically connected with the negative input terminal of the comparator U12, and the output terminal of the comparator U12 is electrically connected with the passive switch.

[0015] Further, the passive switch comprises a resistor R120, a resistor R121, a resistor R123, a diode D23, a transistor Q18 and a transistor Q17; an anode of the diode D23 is electrically connected with an output terminal of the boost module, and a cathode of the diode D23 is electrically connected with an emitter of the transistor Q18;

[0016] a base of the transistor Q18 is electrically connected with a collector of the transistor Q17 in sequence after being connected with the resistor R120 and the resistor R121 in series, an emitter of the transistor Q17 is connected with a GND terminal, and a base of the transistor Q17 is electrically connected with the self-driving module after being connected with the resistor R123 in series;

[0017] a collector of the transistor Q18 is electrically connected with a positive terminal of an output capacitor of the PFC module.

[0018] Further, the active switch comprises a MOS transistor Q16, a resistor R129 and a resistor R130; a drain of the MOS transistor Q16 is electrically connected with one end of the inductor L12, and a source of the MOS transistor Q16 is electrically connected with the other end of the capacitor C50;

[0019] a gate of the MOS transistor Q16 is electrically connected with the controller after being connected with the resistor R129 in series, and the resistor R130 is connected in parallel between the gate and the source of the MOS transistor Q16.

[0020] Further, the input detection module and the output detection module have the same circuit structure;

[0021] the input detection module comprises a resistor R132, a resistor R133 and a resistor R134; one end of the resistor R132 is electrically connected with an input terminal of the boost module; the other end of the resistor R132 is connected with a GND terminal in sequence after being connected with the resistor R133 and the resistor R134 in series, and a common connection point of the resistor R133 and the resistor R134 is electrically connected with the controller.

[0022] A control method of an active dummy load, applied to the switching power supply with the active dummy load and loaded on the controller; comprising the following steps:

[0023] A1: calculating a preset inductance for charging the inductor L12:

[0024] ;

[0025] wherein, is a preset minimum frequency;

[0026] A2: calculating a real-time working frequency of the boost module:

[0027] ;

[0028] A3: if , then execute step A4; if , then execute step A5; otherwise, the controller controls the active switch to remain off; wherein is a preset maximum frequency;

[0029] A4: the on-time ;

[0030] the off-time ;

[0031] A5: the on-time ;

[0032] the off-time .

[0033] The technical solution provided by the application can have the following beneficial effects: a dummy load feedback path is built between the output end of a dimming output module and the positive electrode of an output capacitor of a PFC module by using a boost module and a linear voltage stabilizing module, a voltage obtained from the output end of the dimming output module is boosted to match the voltage of the PFC module, the output voltage of the PFC module is compensated (generally, there is some loss when the PFC module outputs to the dimming output module, which is just compensated), so as to consume the output current of the dimming output module and realize a lower dimming range.

[0034] On this basis, in order to adapt to the change of the output voltage of the dimming output module (such as Vmin to Vmax), an input detection module and an output detection module are arranged to detect the input voltage and the output voltage of the boost module 3, so as to know that the boost module wants to consume (for example, the output current is 10 mA when the dimming is adjusted to the minimum, and the target is to output a current of 5 mA, so the preset consumption current is 5 mA, so the boost module is actively started to feedback and compensate the PFC module to consume 5 mA), and the boost module needs to work at what PWM signal, that is, the on-time and the off-time are calculated. It should be noted that, because the input voltage and the output voltage change with the output voltage of the dimming output module, the preset consumption current can be guaranteed by detection. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1A circuit schematic diagram of a switching power supply with an active dummy load is one of the embodiments of the present application.

[0036] Figure 2 A flow chart of a control method of an active dummy load is one of the embodiments of the present application.

[0037] PFC module 1, dimming output module 2, boost module 3, linear voltage stabilizing module 4, input detection module 5, output detection module 6, active switch 31, capacitor CE10, diode D22, inductor L12, capacitor C50, passive switch 41, self-driving module 42, resistor R124, resistor R125, resistor R126, resistor R127, resistor R128, comparator U12, resistor R120, resistor R121, resistor R123, diode D23, triode Q18, triode Q17, MOS tube Q16, resistor R129, resistor R130, resistor R132, resistor R133, resistor R134. DETAILED DESCRIPTION

[0038] The embodiments of the present application are described in detail below with reference to the accompanying drawings. The embodiments described below are examples for explaining the present application and should not be understood as limiting the present application.

[0039] In the description of the embodiments of the present application, the terms "first", "second" are used only for the purpose of description, and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0040] In the description of the embodiments of the present application, it should be noted that, unless otherwise specifically defined and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0041] The switching power supply with an active dummy load and the dummy load control method of the embodiments of the present application are described below with reference to the accompanying drawings. Figures 1 to 2

[0042] Embodiment 1​

[0043] A switching power supply with active dummy load, comprising a PFC module 1, a dimming output module 2 and a controller; further comprising a boost module 3, a linear voltage stabilizing module 4, an input detection module 5 and an output detection module 6; the input end of the boost module 3 and the output end of the dimming output module 2 are electrically connected, and the output end of the boost module 3 is electrically connected with the positive electrode of the output capacitor of the PFC module 1 through the linear voltage stabilizing module 4;

[0044] The controller is electrically connected with the input end of the boost module 3 through the input detection module 5 to obtain the input voltage ; the controller is electrically connected with the output end of the boost module 3 through the output detection module 6 to obtain the output voltage ;

[0045] The boost module 3 is provided with an active switch 31, which is controlled by the controller; the controller is provided with a consumption current , and the controller calculates the on time and the off time of the active switch 31 through the consumption current , the input voltage and the output voltage , and the on time and the off time of the active switch 31 are combined to form a PWM signal (namely PWM_DUMMY in Figure 1 ) to control the working of the active switch 31.

[0046] The present application proposes a switching power supply with active dummy load, as shown in Figure 1 , a dummy load feedback path is constructed between the output end of the dimming output module 2 (for example, BUCK dimming) and the positive electrode of the output capacitor of the PFC module 1 by using the boost module 3 and the linear voltage stabilizing module 4, the voltage obtained from the output end of the dimming output module 2 is boosted to match the voltage of the PFC module 1, the output voltage of the PFC module 1 is compensated (generally, there is a loss when the PFC module 1 outputs to the dimming output module 2, which is just compensated), so as to consume the output current of the dimming output module 2, and a lower dimming range is realized.

[0047] On this basis, in order to adapt to the change of the output voltage of the dimming output module 2 (such as Vmin to Vmax), the input detection module 5 and the output detection module 6 are arranged to detect the input voltage and the output voltage of the boost module 3, so as to know that the boost module 3 wants to consume (for example, when the output current is 10mA at the lowest, the target is to output 5mA, and the preset consumption current 5mA, so the boost module 3 is actively turned on to feed back the PFC module 1 to consume 5mA; that is, the current to be consumed is the preset consumption current , according to the actual situation), the boost module 3 needs to work at what PWM signal, that is, the on time and the off time are calculated. It should be noted that the input voltage and the output voltage vary with the output voltage of the dimming output module 2, so the constant consumption of the preset consumption current is ensured by detection.

[0048] It should be noted that the circuit structure of the dimming output module 2 as shown in Figure 1 is only used for example and illustration, in which the HV end represents the output voltage of the PFC module 1, the FB1 represents the feedback end of the PWM2 dimming output module 2, so as to externally connect the load dimming through the LED+ and LED- ends; the PWM2 end represents the controller for preventing ghost fire.

[0049] Further, the boost module 3 includes a capacitor CE10, a diode D22, an inductor L12 and a capacitor C50; the capacitor C50 is used as the input end of the boost module 3, the cathode of the diode D22 is used as the output end of the boost module 3, one end and the other end of the capacitor C50 are respectively electrically connected with the positive output end and the negative output end of the dimming output module 2;

[0050] the positive pole of the capacitor CE10 and the cathode of the diode D22 are electrically connected, the anode of the diode D22 and one end of the inductor L12 are electrically connected, the other end of the inductor L12 and one end of the capacitor C50 are electrically connected, the other end of the capacitor C50 and the negative pole of the capacitor CE10 are electrically connected;

[0051] The active switch 31 is coupled between one end of the inductor L12 and the other end of the capacitor C50.

[0052] In this embodiment, the boost principle of the boost module 3 is that when the active switch 31 is turned on, the output end of the dimming output module 2 charges the inductor L12 (that is, the consumption current is consumed), at this time , after the on time , the consumption current is consumed, then the active switch 31 is turned off; when the active switch 31 is turned off, the voltage of the capacitor C50 (that is, ) and the inductor L12 are connected in series to charge the capacitor CE10, then (where is the voltage of the capacitor CE10 at this time, and is the voltage of the inductor L12 at this time), thereby realizing boost.

[0053] Further, the linear voltage stabilizing module 4 comprises a passive switch 41 and a self-driving module 42; the output terminal of the voltage boosting module 3 is electrically connected with the positive terminal of the output capacitor of the PFC module 1 through the passive switch 41, and the self-driving module 42 is coupled between the output terminal of the voltage boosting module 3 and the passive switch 41.

[0054] When the active switch 31 is controlled to be turned off, the voltage boosting module 3 works to increase the voltage output to the self-driving module 42, and the self-driving module 42 drives the passive switch 41 to be turned on.

[0055] In the embodiment, the principle of the linear voltage stabilizing module 4 is mainly to use the self-driving module 42 to sense the completion of the charging of the capacitor C10 (i.e. the voltage increase), and then passively turn on the passive switch 41 to establish a compensation channel between the PFC module 1 and the dimming output module 2, so as to realize the linear voltage stabilizing compensation to the PFC module 1.

[0056] Further, the self-driving module 42 comprises a resistor R124, a resistor R125, a resistor R126, a resistor R127, a resistor R128 and a comparator U12; one end of the resistor R124 is electrically connected with the output terminal of the voltage boosting module 3; the other end of the resistor R124 is connected with the GND ground terminal after being connected with the resistor R125 and the resistor R126 in series; the common connection point of the resistor R125 and the resistor R126 is electrically connected with the positive input terminal of the comparator U12.

[0057] The power supply voltage (for example, 3.3V in the Figure 1 ) is connected with the GND ground terminal through the resistor R127 and the resistor R128; the common connection point of the resistor R127 and the resistor R128 is electrically connected with the negative input terminal of the comparator U12, and the output terminal of the comparator U12 is electrically connected with the passive switch 41.

[0058] In the embodiment, the sensing function of the self-driving module 42 is mainly realized by using the comparator U12; when the voltage of the capacitor CE10 obtained by voltage division exceeds the preset reference voltage (for example, the voltage of the Vref point in the Figure 1 ), the passive switch 41 is driven to be turned on.

[0059] Further, the passive switch 41 comprises a resistor R120, a resistor R121, a resistor R123, a diode D23, a transistor Q18 and a transistor Q17; the anode of the diode D23 is electrically connected with the output terminal of the voltage boosting module 3, and the cathode of the diode D23 is electrically connected with the emitter of the transistor Q18;

[0060] The base of the transistor Q18 is connected with the collector of the transistor Q17 after being connected with the resistor R120 and the resistor R121 in series; the emitter of the transistor Q17 is connected with the GND ground terminal; the base of the transistor Q17 is connected with the self-driving module 42 after being connected with the resistor R123 in series;

[0061] The collector of the triode Q18 and the positive pole of the output capacitor of the PFC module 1 are electrically connected.

[0062] In the embodiment, the passive switch 41 is preferably composed of a double triode, which can accelerate the on-off.

[0063] Further, the active switch 31 comprises a MOS tube Q16, a resistor R129 and a resistor R130; the drain of the MOS tube Q16 and one end of the inductor L12 are electrically connected, and the source of the MOS tube Q16 and the other end of the capacitor C50 are electrically connected.

[0064] The gate of the MOS tube Q16 is connected with the controller in series with the resistor R129; and the resistor R130 is connected in parallel between the gate and the source of the MOS tube Q16.

[0065] In the embodiment, when the active switch 31 is turned on, the inductor L12 is charged, and the active switch 31 needs to bear greater power, which is preferably composed of a MOS tube.

[0066] Further, the circuit structures of the input detection module 5 and the output detection module 6 are the same.

[0067] The input detection module 5 comprises a resistor R132, a resistor R133 and a resistor R134; one end of the resistor R132 is electrically connected with the input end of the boost module 3; the other end of the resistor R132 is connected with the GND ground end in series with the resistor R133 and the resistor R134 in turn; and the common connection point (i.e. Vin or Vout in the above formula) of the resistor R133 and the resistor R134 is electrically connected with the controller. Figure 1

[0068] In the embodiment, the input detection module 5 and the output detection module 6 are preferably adopted for voltage division detection.

[0069] Embodiment 2

[0070] A control method of an active dummy load, applied to the above-mentioned switching power supply with an active dummy load, and loaded on the controller; comprising the following steps:

[0071] A1: calculating a preset inductance for charging the inductor L12:

[0072] ;

[0073] Wherein, fmin is a preset minimum frequency (i.e. in order to limit the working frequency range of the boost module 3, to exclude the continuous mode, which will be described in detail below);

[0074] A2: calculating the real-time working frequency of the boost module 3:

[0075] ;​​

[0076] A3: if , then step A4 is executed; if , then step A5 is executed; otherwise, the controller controls the active switch to remain off; wherein is a preset maximum frequency (i.e. to limit the operating frequency range of the boost module 3, to exclude continuous mode, as will be explained below);

[0077] A4: on time ;

[0078] off time ;

[0079] A5: on time ;

[0080] off time .

[0081] In the case that the boost module 3 is configured with a boost circuit composed of the capacitor CE10, the diode D22, the inductor L12 and the capacitor C50, the boost module 3 can operate in various modes, for example: when the active switch 31 is off, the current of the inductor L12 decreases linearly, and when the inductor current has not decreased to 0 mA, the active switch 31 is turned on again, which is continuous mode; when the inductor current decreases to 0 mA, the active switch 31 is turned on again immediately, which is critical mode; when the inductor current decreases to 0 mA, the active switch 31 is turned on again after a period of time, which is discontinuous mode. Since the input of the boost module 3 is a very wide range, the operating frequency range of the module according to the PWM signal is also wide, and if not limited, when the operating frequency is too low, the human ear will hear noise; when the operating frequency is too high, electromagnetic compatibility problems will occur, so a minimum frequency and a maximum frequency are preset to make the boost module 3 operate within a specific operating frequency range, to avoid noise caused by too low frequency and electromagnetic compatibility problems caused by too high frequency. In the three modes, the operating frequency of the continuous mode is always lower than the preset minimum frequency , so this mode is not selected (i.e. the active switch 31 remains off; only the active switch 31 repeatedly turns on and off can achieve feedback compensation of the PFC module 1 consumption current, otherwise neither the boost module 3 nor the linear voltage regulator module 4 works), and only the boost module 3 is set to critical mode and discontinuous mode.

[0082] Therefore, the application also proposes a preferred embodiment of a control method of an active dummy load, as shown in Figure 2 , the controller first executes step A1, and substitutes the preset consumption current , the preset minimum frequency such that continuous mode is excluded), the detected input voltage and output voltage , the inductance L12 will be calculated to charge ; thus, the step A2 is substituted, the working frequency of the boost module 3 is determined, falling into critical mode or discontinuous mode ; then, the step A4 or A5 is executed to form the PWM signal to control the on-off of the active switch 31, determining the boost consumption mode of the current consumption. It should be noted that the formula is summarized by analyzing the circuit of the boost module 3, wherein the step A4 is mainly to make the boost module 3 in the variable frequency mode, floating between the preset minimum frequency and the preset maximum frequency ; the step A5 is mainly to make the boost module 3 in the fixed frequency mode, substituting the preset maximum frequency , and being constant at the preset maximum frequency .

[0083] Other configurations and operations of the switch power supply with the active dummy load and the dummy load control method according to the embodiments of the present application are known to those skilled in the art, and thus will not be described in detail herein.

[0084] In the description of the present specification, the description referring to the terms “embodiment”, “example” and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0085] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A switching power supply with active dummy load, comprising a PFC module, a light output module and a controller; characterized in that: The voltage boosting module, the linear voltage stabilizing module, the input detecting module and the output detecting module are further included; the input end of the voltage boosting module is electrically connected with the output end of the dimming output module, and the output end of the voltage boosting module is electrically connected with the positive pole of the output capacitor of the PFC module through the linear voltage stabilizing module; The controller is electrically connected with the input end of the boosting module through the input detection module to acquire an input voltage The controller is electrically connected with the output end of the boosting module through the output detection module to acquire an output voltage ​ The boost module is equipped with an active switch, which is electrically connected to and controlled by the controller; the controller has a preset current consumption. The controller uses the current consumption The input voltage and the output voltage Calculate the conduction time of the active switch. and shutdown time The conduction time and the shutdown time The PWM signal is used to control the operation of the active switch. The voltage boosting module includes a capacitor CE10, a diode D22, an inductor L12 and a capacitor C50; the capacitor C50 is used as the input end of the voltage boosting module, the cathode of the diode D22 is used as the output end of the voltage boosting module, and one end and the other end of the capacitor C50 are electrically connected with the positive pole and the negative pole of the output end of the dimming output module, respectively; The positive pole of the capacitor CE10 is electrically connected with the cathode of the diode D22, the anode of the diode D22 is electrically connected with one end of the inductor L12, the other end of the inductor L12 is electrically connected with one end of the capacitor C50, and the other end of the capacitor C50 is electrically connected with the negative pole of the capacitor CE10; The active switch is coupled between one end of the inductor L12 and the other end of the capacitor C50.

2. The switching power supply with active dummy load according to claim 1, characterized in that The linear voltage stabilizing module includes a passive switch and a self-driving module; the output end of the voltage boosting module is electrically connected with the positive pole of the output capacitor of the PFC module through the passive switch, and the self-driving module is coupled between the output end of the voltage boosting module and the passive switch; When the active switch is controlled to be turned off by the controller, the voltage boosting module works to increase the voltage output to the self-driving module, and the self-driving module drives the passive switch to be turned on.

3. The switching power supply with active dummy load according to claim 2, characterized in that: The self-driving module includes a resistor R124, a resistor R125, a resistor R126, a resistor R127, a resistor R128 and a comparator U12; one end of the resistor R124 is electrically connected with the output end of the voltage boosting module; the other end of the resistor R124 is connected with the GND ground terminal after the resistor R125 and the resistor R126 are connected in series; the common connection point of the resistor R125 and the resistor R126 is electrically connected with the positive input end of the comparator U12; The power supply voltage is connected with the GND ground terminal after the resistor R127 and the resistor R128; the common connection point of the resistor R127 and the resistor R128 is electrically connected with the negative input end of the comparator U12, and the output end of the comparator U12 is electrically connected with the passive switch.

4. The switching power supply with active dummy load according to claim 2, characterized in that: The passive switch includes a resistor R120, a resistor R121, a resistor R123, a diode D23, a transistor Q18 and a transistor Q17; the anode of the diode D23 is electrically connected with the output end of the voltage boosting module, and the cathode of the diode D23 is electrically connected with the emitter of the transistor Q18; The base of the transistor Q18 is electrically connected with the collector of the transistor Q17 after the resistor R120 and the resistor R121 are connected in series; the emitter of the transistor Q17 is connected with the GND ground terminal; the base of the transistor Q17 is connected with the self-driving module after the resistor R123 is connected in series; The collector of the transistor Q18 is electrically connected with the positive pole of the output capacitor of the PFC module.

5. The switching power supply with active dummy load according to claim 1, characterized in that: The active switch comprises a MOS tube Q16, a resistor R129 and a resistor R130; one end of the MOS tube Q16 is electrically connected with the inductor L12, and the other end of the MOS tube Q16 is electrically connected with the capacitor C50; The gate of the MOS tube Q16 is electrically connected with the controller in series with the resistor R129; and the resistor R130 is connected in parallel between the gate and the source of the MOS tube Q16.

6. The switching power supply with active dummy load according to claim 1, characterized in that: The circuit structure of the input detection module and the output detection module is the same; The input detection module comprises a resistor R132, a resistor R133 and a resistor R134; one end of the resistor R132 is electrically connected with the input end of the boost module; the other end of the resistor R132 is connected with the ground in series with the resistor R133 and the resistor R134 in turn; and the common connection point of the resistor R133 and the resistor R134 is electrically connected with the controller.

7. A control method of an active dummy load characterized by comprising: The application is applied to a switching power supply with an active dummy load according to claim 1 or 5, and is loaded on the controller and comprises the following steps: A1: calculating a preset inductance for charging the inductor L12: ； wherein, is a preset minimum frequency; A2: calculating a real-time working frequency of the boost module: ； A3: if then step A4 is performed; if then step A5 is performed; otherwise the controller controls the active switch to remain off; wherein is a predetermined maximum frequency; A4: the on-time ; the turn-off time ; A5: the on-time ; the turn-off time .

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