A high power factor single-stage switching power supply without stroboscopic effect

Abstract

The application relates to the technical field of switching power supplies, in particular to a high-power-factor single-stage switching power supply without frequency flicker; an output module is electrically connected with a control module through a dynamic voltage detection module; the control module receives a dynamic voltage signal from the output module; the control module is electrically connected with an input module through a dynamic voltage adjustment module and a primary side feedback module in sequence; the control module generates an adjustment signal according to the dynamic voltage signal, controls the opening or closing of the dynamic voltage adjustment module, feeds back to the input module through the primary side feedback module, and adjusts the dynamic voltage signal generated by the output module by the input module; the control module is electrically connected with the output module through a current chopping adjustment module; the control module generates a chopping signal according to the received dynamic voltage signal, and the chopping signal drives the current chopping adjustment module to chop the dynamic voltage signal generated by the output module; the problem that the output current ripple of the high-power-factor single-stage switching power supply is large is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, in particular to a high power factor single-stage switching power supply without frequency flicker. BACKGROUND

[0002] At present, the commonly used power supply topological architecture of switching power supply includes high power factor two-stage circuit and low power factor single-stage circuit. Among them, the first stage circuit in the high power factor two-stage circuit is used to convert alternating current into high voltage direct current (boosting), and the second stage circuit is used to convert high voltage direct current into low voltage direct current (buck), at this time, the output current ripple is small, which can meet the frequency flicker requirement; while in the low power factor single-stage circuit, a large electrolytic capacitor is connected in parallel after input rectification, which can filter the low frequency ripple to be small, and convert high voltage direct current into low voltage direct current after the electrolytic capacitor (i.e. the single-stage circuit is only used for bucking), because the input ripple of the circuit is already small, the output current ripple is also small, which also meets the frequency flicker requirement.

[0003] However, the high power factor two-stage circuit architecture is a two-stage scheme, which has high cost, and because the overall efficiency is the product of the two-stage circuit, the overall efficiency is also not high, especially for small power supply; while the low power factor single-stage circuit architecture is a single-stage scheme, but the circuit cannot meet the harmonic requirement of EMC standard (insufficient power factor) in medium and large power supply application.

[0004] Therefore, considering comprehensively, the high power factor single-stage circuit architecture is the best solution, but after improving the power factor, there is a problem of large output current ripple. SUMMARY

[0005] In view of the above defects, the purpose of the present application is to provide a high power factor single-stage switching power supply without frequency flicker, which solves the problem of large output current ripple of high power factor single-stage switching power supply.

[0006] To achieve this purpose, the present application adopts the following technical scheme:

[0007] A high power factor single-stage switching power supply without frequency flicker, comprising a transformer T1, an input module of the primary side of the transformer T1 and an output module of the secondary side of the transformer T1; further comprising a current chopping regulation module, a dynamic voltage detection module, a primary side feedback module, a dynamic voltage regulation module and a control module;

[0008] The output module is electrically connected with the control module through the dynamic voltage detection module; the control module receives a dynamic voltage signal from the output module;

[0009] The control module is electrically connected to the input module via the dynamic voltage regulation module and the primary-side feedback module in sequence; the control module generates an adjustment signal according to the dynamic voltage signal, controls the on / off of the dynamic voltage regulation module, and feeds back the adjustment signal to the input module via the primary-side feedback module, so that the input module adjusts the dynamic voltage signal generated by the output module;

[0010] The control module is electrically connected to the output module via the current chopping regulation module; the control module generates a chopping signal according to the received dynamic voltage signal, and the chopping signal drives the current chopping regulation module to chop the dynamic voltage signal generated by the output module.

[0011] Furthermore, the regulating signal is a first PWM signal;

[0012] When the control module determines that the minimum value Vo_min of the dynamic voltage signal is less than the preset minimum voltage value, the duty cycle Don of the adjustment signal is increased by one level, and the input module performs a one-level boost adjustment on the dynamic voltage signal generated by the output module;

[0013] When the control module determines that the minimum value Vo_min of the dynamic voltage signal is equal to the preset minimum voltage value, the duty cycle Don of the adjustment signal remains unchanged, and the input module does not adjust the dynamic voltage signal generated by the output module;

[0014] When the control module determines that the minimum value Vo_min of the dynamic voltage signal is greater than the preset maximum voltage value, the duty cycle Don of the regulation signal is reduced by one level, and the input module reduces the dynamic voltage signal generated by the output module by one level.

[0015] Furthermore, the value of the dynamic voltage signal boosted by one level or stepped down by one level is:

[0016] △V=Vo-Vo_min or △V=Vo_max-Vo;

[0017] Wherein, Vo is the effective value of the dynamic voltage signal, Vo_min is the minimum value of the dynamic voltage signal, and Vo_max is the maximum value of the dynamic voltage signal.

[0018] Furthermore, the chopping signal is a second PWM signal, and the duty cycle of the chopping signal is:

[0019] Duty=(Vo_min-Vled) / (Vo-Vled);

[0020] Wherein, Vo_min is the minimum value of the dynamic voltage signal, Vled is the voltage of the load lamp, and Vo is the effective value of the dynamic voltage signal.

[0021] Further, the primary side feedback module includes a resistor R27, a resistor R28, a photoelectric coupler U3, a resistor R30, a resistor R31, a resistor R35, a resistor R32, a resistor R36, a resistor R37, a capacitor C9, a capacitor C10, and a controllable voltage regulator U4.

[0022] The reference end of the controllable voltage regulator U4 is electrically connected to the dynamic voltage regulation module. One end of the resistor R36, one end of the resistor R37, one end of the resistor R35, one end of the capacitor C9, and one end of the capacitor C10 are electrically connected to the reference end of the controllable voltage regulator U4. The other end of the capacitor C10 and one end of the resistor R32 are electrically connected. The other end of the resistor R32, the other end of the capacitor C9, one end of the resistor R31, and the cathode of the light-emitting source of the photoelectric coupler U3 are electrically connected to the cathode of the controllable voltage regulator U4. The anode of the controllable voltage regulator U4, the other end of the resistor R36, and the other end of the resistor R37 are electrically connected to the SGND ground end. The anode of the light-emitting source of the photoelectric coupler U3 and one end of the resistor R30 are electrically connected. The other end of the resistor R30, the other end of the resistor R31, and the other end of the resistor R35 are electrically connected to the power supply voltage.

[0023] The collector of the light receiver of the photoelectric coupler U3 is connected to the power supply voltage. The emitter of the light receiver of the photoelectric coupler U3 and one end of the resistor R28 are electrically connected to one end of the resistor R27. The other end of the resistor R28 is connected to the GND ground end. The other end of the resistor R27 and the input module are electrically connected.

[0024] Further, the dynamic voltage regulation module includes a transistor Q3, a resistor R39, a resistor R40, a transistor Q6, a resistor R42, a comparator U6A, a capacitor C13, a capacitor C15, a capacitor C18, and a resistor R46.

[0025] One end of the resistor R46 is electrically connected to the control module, one end of the resistor R46 is electrically connected to one end of the capacitor C18, the other end of the resistor R46 and one end of the capacitor C15 are electrically connected to the positive input terminal of the comparator U6A, one end of the capacitor C13, the collector of the transistor Q3, and one end of the resistor R39 are electrically connected to the negative input terminal of the comparator U6A, the other end of the capacitor C13, the other end of the capacitor C15, and the other end of the capacitor C18 are all connected to the SGND ground terminal, the output terminal of the comparator U6A is electrically connected to the base of the transistor Q6 via the resistor R42, the collector of the transistor Q6 is electrically connected to the base of the transistor Q3 via the resistor R40, the other end of the resistor R39 and the emitter of the transistor Q6 are both connected to the SGND ground terminal, and the emitter of the transistor Q3 is electrically connected to the primary feedback module.

[0026] Furthermore, the current chopping regulation module includes a MOS tube Q2, a resistor R34, a resistor R38, a resistor R41, a transistor Q4 and a transistor Q5;

[0027] One end of the resistor R41 is electrically connected to the control module, the other end of the resistor R41 and the base of the transistor Q4 are electrically connected to the base of the transistor Q5, the collector of the transistor Q5 is connected to the SGND ground terminal, the collector of the transistor Q4 is connected to the power supply voltage, the emitter of the transistor Q4 and the emitter of the transistor Q5 are electrically connected to one end of the resistor R38, the other end of the resistor R38 and one end of the resistor R34 are electrically connected to the gate of the MOS transistor Q2, the other end of the resistor R34 is electrically connected to the source of the MOS transistor Q2, and the MOS transistor Q2 is connected in series to the negative electrode of the output module through the drain and source.

[0028] Furthermore, the dynamic voltage detection module includes a resistor R43 and a resistor R44; the positive pole of the output module is connected in series with the resistor R43 and the resistor R44 in sequence, and then connected to the SGND ground terminal; the common point of the resistor R43 and the resistor R44 is electrically connected to the control module.

[0029] The technical solution provided by the present invention may have the following beneficial effects: To address the flicker problem of high-power-factor single-stage switching power supplies, a chopping method is used to reduce the output current ripple of the switching power supply. To this end, a dynamic voltage detection module first detects the output voltage of the output module (i.e., the dynamic voltage signal, VBUS). Then, a control module (such as an MCU module) generates different adjustment signals (REF_PWM) based on the chopping requirements of different voltage points in the dynamic voltage signal. The input module (for example, the power management chip U2 fed back to the input module) adjusts the dynamic voltage signal generated by the output module (increases, decreases, or keeps it unchanged) to ensure that the output current maintains the original output current level after subsequent chopping (equivalent to ensuring that the dimming current remains unchanged, but the fluctuation is reduced).

[0030] On this basis, the control module generates a chopping signal according to the dynamic voltage signal, and uses the chopping signal to drive the current chopping regulation module to finally chop the dynamic voltage signal generated by the output module one by one; low-frequency ripple current is obtained through high-frequency chopping. At this time, the current ripple is relatively small and can be ignored, meeting the requirements of the flicker test. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The diagram is a schematic diagram of a single-stage switching power supply with high power factor and no flicker according to one embodiment of the present invention.

[0032] Figure 2 Yes Figure 1 The output voltage and output current comparison diagram of the output module before chopping is shown.

[0033] Figure 3 Yes Figure 1 The output voltage and output current comparison diagram of the output module after chopping is shown.

[0034] Figure 4 Yes Figure 1 A comparison diagram of the dynamic voltage signal boosting stage in the output module shown.

[0035] Figure 5 Yes Figure 1 The circuit diagram of the primary side feedback module and the dynamic voltage regulation module is shown.

[0036] Figure 6 Yes Figure 1 The circuit diagram of the current chopping regulation module and the dynamic voltage detection module is shown.

[0037] Among them: transformer T1, input module 6, output module 7, current chopping regulation module 1, dynamic voltage detection module 2, primary side feedback module 3, dynamic voltage regulation module 4, control module 5, resistor R27, resistor R28, optocoupler U3, resistor R30, resistor R31, resistor R35, resistor R32, resistor R36, resistor R37, capacitor C9, capacitor C10, controllable voltage regulator U4, transistor Q3, resistor R39, resistor R40, transistor Q6, resistor R42, comparator U6A, capacitor C13, capacitor C15, capacitor C18, resistor R46, MOS tube Q2, resistor R34, resistor R38, resistor R41, transistor Q4, transistor Q5, resistor R43, resistor R44. DETAILED DESCRIPTION

[0038] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0039] In the description of the embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the described features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically specified.

[0040] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections or indirect connections through an intermediate medium; they may refer to internal communication between two components or an interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on specific circumstances.

[0041] The following combination Figures 1 to 6 , describing a flicker-free, high power factor, single-stage switching power supply according to an embodiment of the present invention.

[0042] A flicker-free, high-power-factor, single-stage switching power supply comprises a transformer T1, an input module 6 on the primary side of the transformer T1, and an output module 7 on the secondary side of the transformer T1; further comprising a current chopping regulation module 1, a dynamic voltage detection module 2, a primary-side feedback module 3, a dynamic voltage regulation module 4, and a control module 5;

[0043] The output module 7 is electrically connected to the control module 5 via the dynamic voltage detection module 2; the control module 5 receives the dynamic voltage signal from the output module 7;

[0044] The control module 5 is electrically connected to the input module 6 via the dynamic voltage regulation module 4 and the primary-side feedback module 3. The control module 5 generates an adjustment signal based on the dynamic voltage signal to control the on / off of the dynamic voltage regulation module 4. The adjustment signal is fed back to the input module 6 via the primary-side feedback module 3, and the input module 6 adjusts the dynamic voltage signal generated by the output module 7.

[0045] The control module 5 is electrically connected to the output module 7 via the current chopping regulation module 1 ; the control module 5 generates a chopping signal according to the received dynamic voltage signal, and the chopping signal drives the current chopping regulation module 1 to chop the dynamic voltage signal generated by the output module 7 .

[0046] The present invention proposes a preferred embodiment of a single-stage switching power supply with high power factor without flicker, as shown in FIG. Figure 1 As shown in the figure, in order to solve the flicker problem of high power factor single-stage switching power supply, chopping is used to reduce the output current ripple of the switching power supply. To this end, the output voltage of the output module 7 (i.e., dynamic voltage signal, VBUS) is first detected by the dynamic voltage detection module 2, and then the control module 5 (such as MCU module) generates different adjustment signals (i.e., Figure 1 In REF_PWM), the dynamic voltage signal generated by the output module 7 is adjusted (increased, decreased or unchanged) by the input module 6 (for example, fed back to the power management chip U2 in the input module 6, such as the L6562 model chip) to ensure that the output current after subsequent chopping can maintain the original output current level (equivalent to ensuring that the dimming current remains unchanged, but the fluctuation is reduced).

[0047] On this basis, the control module 5 generates a chopping signal (ie Figure 1 In PWM), the current chopping regulation module 1 is driven by a chopping signal (such as a PWM signal with different duty cycles, different voltage values ​​and other parameters) to finally chop the dynamic voltage signal generated by the output module 7 one by one; before chopping, the corresponding relationship between the output voltage and the output current is as follows Figure 2 As shown, the output current and output voltage are in phase, and the ripple is large (i.e., the degree of fluctuation). Because the dynamic voltage signal is a periodic voltage signal (i.e., the output voltage is also a periodic voltage signal), the voltage signal at each time point needs to be chopped; after chopping, the corresponding relationship between the output voltage and output current is as follows Figure 3 As shown, the low-frequency ripple current is obtained by high-frequency chopping (meaning that Figure 3As shown, the sine wave is low frequency, generally 100-120Hz, and the frequency of the rectangular column is preferably high frequency, generally 10k-20kHz), that is, the output current, such as Figure 3 It should be noted that the output current usually mentioned is the average value, such as Figure 3 As shown in the figure, it can be seen that the duty cycle (Duty) of each chopping cycle is different. When it is at the minimum value of the sine wave waveform, its duty cycle is 100%, and when it is at the peak of the waveform, its duty cycle is the minimum; thus, the average value of the output current in the entire power frequency cycle is an output current with a very small ripple value, as shown in the figure. Figure 3 The waveform that approximates a straight line, that is, the sine wave, is multiplied by its corresponding duty cycle to obtain an output ripple current that is infinitely close to the nominal value. At this time, the current ripple is relatively small and can be ignored, meeting the requirements of the stroboscopic test.

[0048] It should be noted that there are many types of high power factor single-stage switching power supply main circuits composed of transformer T1, input module 6 and output module 7, one of which can be referred to Figure 1 , which is not limited here.

[0049] Furthermore, the regulation signal is a first PWM signal;

[0050] When the control module 5 determines that the minimum value Vo_min of the dynamic voltage signal is less than the preset minimum voltage value, the duty cycle Don of the regulation signal is increased by one level, and the input module 6 performs a voltage boost adjustment on the dynamic voltage signal generated by the output module 7;

[0051] When the control module 5 determines that the minimum value Vo_min of the dynamic voltage signal is equal to the preset minimum voltage value, the duty cycle Don of the regulation signal remains unchanged, and the input module 6 does not adjust the dynamic voltage signal generated by the output module 7;

[0052] When the control module 5 determines that the minimum value Vo_min of the dynamic voltage signal is greater than the preset maximum voltage value, the duty cycle Don of the adjustment signal is adjusted to step down by one level, and the input module 6 steps down the dynamic voltage signal generated by the output module 7 by one level.

[0053] In this embodiment, different chopping signals need to be generated according to different dynamic voltage signals for one-to-one chopping. The chopping signal preferably uses a first PWM signal. The control module 5 can obtain different PWM signals by modulating the duty cycle, which facilitates signal generation. In addition, considering that chopping usually reduces the output current level, in order to ensure that the output current can maintain the original output current level after subsequent chopping, the dynamic voltage signal should be raised as a whole (i.e., a one-stage step-up adjustment), such as Figure 4As shown, the original dynamic voltage signal is a waveform from Vo1_min to Vo1_max, and the dynamic voltage signal after raising is a waveform from Vo2_min to Vo2_max.

[0054] However, considering that the dynamic voltage signal is not constant, for the same power supply, the dynamic voltage signal will be different when the load size is different. Therefore, it is necessary to preset the effective value (or nominal value, such as Figure 4 Vo1 in the figure is used as the preset minimum voltage value to determine whether it needs to be raised to ensure the minimum value Vo_min of the dynamic voltage signal (such as Figure 4 Vo2_min) is always not less than the effective value of the preset dynamic voltage signal (equivalent to Figure 4 In the example, Vo2_min is always greater than or equal to Vo1; at the same time, the maximum value of the dynamic voltage signal (such as Figure 4 Vo1_max in the output voltage is used as the preset maximum voltage value to determine whether it needs to be reduced to avoid excessive deviation of the dynamic voltage signal, thereby ensuring the output current level.

[0055] Furthermore, the value of the dynamic voltage signal boosted or stepped down by one level is:

[0056] △V=Vo-Vo_min or △V=Vo_max-Vo;

[0057] Wherein, Vo is the effective value of the dynamic voltage signal, Vo_min is the minimum value of the dynamic voltage signal, and Vo_max is the maximum value of the dynamic voltage signal.

[0058] In this embodiment, the fluctuation of the dynamic voltage signal is usually constant, such as Figure 4 As shown, △V is used as the value for boosting or reducing the dynamic voltage signal by one level. Usually, only one increase or decrease is needed to meet the requirements, which is convenient for adjustment. If faced with special circumstances, further judgment and adjustment can be made.

[0059] Furthermore, the chopping signal is a second PWM signal, and the duty cycle of the chopping signal is:

[0060] Duty=(Vo_min-Vled) / (Vo-Vled);

[0061] Wherein, Vo_min is the minimum value of the dynamic voltage signal, Vled is the voltage of the load lamp, and Vo is the effective value of the dynamic voltage signal.

[0062] In this embodiment, the output current calculation formula of the switching power supply is Iled=(Vo-Vled) / R. Through this formula, we can calculate that the minimum output current after adjustment when the output voltage is Vo2_min is Iled_min=(Vo2_min-Vled) / R. In this calculation formula, Vled is the voltage of the load lamp, and R is the equivalent resistance of the load lamp, both of which are known physical quantities. Vo2_min can be detected by the dynamic voltage detection module 2. Through calculation, the current value of Iled_min can be obtained. This current value is the reference value of the output current of the circuit. Since the low-frequency ripple of the output voltage waveform is usually 100-120Hz, high-frequency chopping can be used at other points of the output voltage to obtain a low-frequency ripple current with a relatively smooth average current. The chopping frequency can be 16kHz. Therefore, the chopping duty cycle at different voltage points is calculated by the following formula: Duty=Iled-min / (Vo-Vled) R, substituting into the formula Iled_min=(Vo2_min-Vled) / R, we finally get Duty=(Vo_min-Vled) / (Vo-Vled). Therefore, the second PWM signal constructed as the chopping signal can achieve the purpose of obtaining low-frequency ripple current.

[0063] Furthermore, the primary feedback module 3 includes a resistor R27, a resistor R28, an optocoupler U3, a resistor R30, a resistor R31, a resistor R35, a resistor R32, a resistor R36, a resistor R37, a capacitor C9, a capacitor C10 and a controllable voltage regulator U4;

[0064] The reference end of the controllable voltage-stabilizing source U4 is electrically connected to the dynamic voltage regulation module 4, one end of the resistor R36, one end of the resistor R37, one end of the resistor R35, one end of the capacitor C9, and one end of the capacitor C10 are all electrically connected to the reference end of the controllable voltage-stabilizing source U4, the other end of the capacitor C10 is electrically connected to one end of the resistor R32, the other end of the resistor R32, the other end of the capacitor C9, one end of the resistor R31, and the cathode of the light source of the photoelectric coupler U3 are all electrically connected to the cathode of the controllable voltage-stabilizing source U4, the anode of the controllable voltage-stabilizing source U4, the other end of the resistor R36, and the other end of the resistor R37 are all electrically connected to the SGND ground end, the anode of the light source of the photoelectric coupler U3 is electrically connected to one end of the resistor R30, and the other end of the resistor R30, the other end of the resistor R31, and the other end of the resistor R35 are all connected to the power supply voltage;

[0065] The collector of the photoreceiver of the photocoupler U3 is connected to the power supply voltage, the emitter of the photoreceiver of the photocoupler U3 and one end of the resistor R28 are electrically connected to one end of the resistor R27, the other end of the resistor R28 is connected to the GND ground, and the other end of the resistor R27 is electrically connected to the input module 6.

[0066] In this embodiment, the primary feedback module 3 is a common feedback circuit in a switching power supply for feeding back the voltage of the output module 7 to the power management chip U2 in the input module 6. The feedback principle is as follows:

[0067] like Figure 5 As shown, the voltage sampling is composed of resistors R35, R36 and R37; for example, when the positive electrode of the output module 7 is 24V, the reference voltage of the controllable voltage regulator U4 (reference end) is 2.5V.

[0068] Since the current I1=I2+I3, and the reference end of the controllable voltage regulator U4 is high impedance, that is, I2 is approximately equal to 0, I1≈I3=2.5 / (R36+R37), the voltage difference of the resistor R35 is I1 R35=2.5 R35 / (R36+R37), the output voltage effective value of output module 7 Vo1=I1 R35+2.5=2.5 R35 / (R36+R37)+2.5 (with Figure 4 As an example), the effective value of the output voltage is adjusted according to the voltage sampling of the output module 7.

[0069] Furthermore, the dynamic voltage regulation module 4 includes a transistor Q3, a resistor R39, a resistor R40, a transistor Q6, a resistor R42, a comparator U6A, a capacitor C13, a capacitor C15, a capacitor C18 and a resistor R46;

[0070] One end of the resistor R46 is electrically connected to the control module 5, one end of the resistor R46 is electrically connected to one end of the capacitor C18, the other end of the resistor R46 and one end of the capacitor C15 are electrically connected to the positive input terminal of the comparator U6A, one end of the capacitor C13, the collector of the transistor Q3, and one end of the resistor R39 are electrically connected to the negative input terminal of the comparator U6A, the other end of the capacitor C13, the other end of the capacitor C15, and the other end of the capacitor C18 are all connected to the SGND ground terminal, the output terminal of the comparator U6A is electrically connected to the base of the transistor Q6 via the resistor R42, the collector of the transistor Q6 is electrically connected to the base of the transistor Q3 via the resistor R40, the other end of the resistor R39 and the emitter of the transistor Q6 are both connected to the SGND ground terminal, and the emitter of the transistor Q3 is electrically connected to the primary feedback module 3.

[0071] In this embodiment, based on the circuit structure of the primary feedback module 3 , a dynamic voltage regulation module 4 is added to receive a regulation signal to intervene in the feedback of the primary feedback module 3 , thereby changing the dynamic voltage signal of the output module 7 .

[0072] like Figure 5As shown, the current direction of the sampling point is: I1=I2+I3+I4, wherein I2 is approximately equal to 0 and can be ignored, i.e. I1=I3+I4, I3=2.5 / (R36+R37); the current I4 is a current controlled by the REF_PWM (i.e. the adjustment signal). The working principle is as follows:

[0073] The REF_PWM is a PWM waveform with a duty ratio of Don, which is converted into a direct current voltage waveform by the CRC network and transmitted to the positive input end of the comparator U6A, and the voltage of the sampling resistor R39 at the reverse input end of the comparator U6A. When the voltage between the two ends of the resistor R39 is less than the voltage (for example, 3.3V Don) at the positive input end, the U6A outputs a high level, the transistor Q6 and the transistor Q3 are turned on, the voltage between the two ends of the resistor R39 is increased, and the current I4 is increased synchronously, until the voltage between the two ends of the resistor R39 (I4 R39) is equal to the positive input end of the comparator U6A, the comparator U6A outputs 0, and the transistors Q6 and Q3 are turned off, and the current I4 is 0. The two states are repeated, and the dynamic voltage adjustment module 4 is a negative feedback circuit, and the current I4 is maintained at a stable current, i.e. I4=3.3 Don / R39; since R39 is a known resistance value, the current I4 can be adjusted by adjusting Don; therefore, I1=I3+I4=2.5 / (R36+R37)+3.3 Don / R39; that is, after adding the dynamic voltage adjustment module 4, the effective value of the output voltage of the main circuit is (for example, with Figure 4 Vo1=I1 R35+2.5=2.5

[0074] R35 / (R36+R37)+2.5; After adding the dynamic voltage adjustment module 4, the effective value of the output voltage of the main circuit is: Vo2=I1

[0075] R35+2.5=(2.5 / (R36+R37)+3.3 Don / R39)

[0076] R35+2.5;

[0077] After adding the dynamic voltage adjustment module 4, the effective value of the output voltage of the main circuit is:

[0078] Vo2=I1 R35+2.5=(2.5 / (R36+R37)+3.3 Don / R39) R35+2.5;​

[0079] From the above formula comparison can be seen, by adjusting Don can adjust the dynamic voltage signal, dynamic voltage adjustment module 4 can be opened or closed according to the adjustment signal to drive the primary side feedback module 3 to realize the adjustment function.

[0080] Further, the current chopping adjustment module 1 comprises MOS tube Q2, resistor R34, resistor R38, resistor R41, triode Q4 and triode Q5;

[0081] One end of the resistor R41 is electrically connected with the control module 5, the other end of the resistor R41 and the base of the triode Q4 are electrically connected with the base of the triode Q5, the collector of the triode Q5 is connected with the SGND ground end, the collector of the triode Q4 is connected with the power supply voltage, the emitter of the triode Q4 and the emitter of the triode Q5 are electrically connected with one end of the resistor R38, the other end of the resistor R38 and one end of the resistor R34 are electrically connected with the gate of the MOS tube Q2, the other end of the resistor R34 is electrically connected with the source of the MOS tube Q2, and the MOS tube Q2 is connected in series with the negative electrode of the output module 7 through the drain and the source.

[0082] In the embodiment, as shown in the figure, Figure 6 The current chopping adjustment module 1 comprises a push-pull circuit composed of the triode Q4 and the triode Q5 to drive the MOS tube Q2 to be turned on or turned off, thereby realizing the chopping of the output module 7.

[0083] Further, the dynamic voltage detection module 2 comprises resistor R43 and resistor R44; the positive electrode of the output module 7 is connected with the SGND ground end in sequence after being connected with the resistor R43 and the resistor R44; and the common connection point of the resistor R43 and the resistor R44 is electrically connected with the control module 5.

[0084] In the embodiment, the dynamic voltage detection module 2 comprises a voltage detection circuit composed of the resistor R43 and the resistor R44.

[0085] Other configurations and operations of the high power factor single-stage switching power supply without stroboscopic effect according to the embodiment of the application are known to those skilled in the art, and thus will not be described in detail herein.

[0086] In the description of the 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 contained in at least one embodiment or example of the application. In the specification, the illustrative description of the above terms does 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.

[0087] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A flicker-free, high power factor, single-stage switching power supply comprising a transformer T1, an input module on the primary side of the transformer T1, and an output module on the secondary side of the transformer T1; characterized in that: It also includes a current chopping regulation module, a dynamic voltage detection module, a primary side feedback module, a dynamic voltage regulation module and a control module; The output module is electrically connected to the control module via the dynamic voltage detection module; the control module receives a dynamic voltage signal from the output module; The control module is electrically connected to the input module via the dynamic voltage regulation module and the primary-side feedback module in sequence; the control module generates an adjustment signal according to the dynamic voltage signal, controls the on / off of the dynamic voltage regulation module, and feeds back the adjustment signal to the input module via the primary-side feedback module, so that the input module adjusts the dynamic voltage signal generated by the output module; The control module is electrically connected to the output module via the current chopping regulation module; The control module generates a chopping signal according to the received dynamic voltage signal, and the chopping signal drives the current chopping regulation module to chop the dynamic voltage signal generated by the output module; The dynamic voltage regulation module includes a transistor Q3, a resistor R39, a resistor R40, a transistor Q6, a resistor R42, a comparator U6A, a capacitor C13, a capacitor C15, a capacitor C18 and a resistor R46; One end of the resistor R46 is electrically connected to the control module, one end of the resistor R46 is electrically connected to one end of the capacitor C18, the other end of the resistor R46 and one end of the capacitor C15 are electrically connected to the positive input terminal of the comparator U6A, one end of the capacitor C13, the collector of the transistor Q3, and one end of the resistor R39 are electrically connected to the negative input terminal of the comparator U6A, the other end of the capacitor C13, the other end of the capacitor C15, and the other end of the capacitor C18 are all connected to the SGND ground terminal, the output terminal of the comparator U6A is electrically connected to the base of the transistor Q6 via the resistor R42, the collector of the transistor Q6 is electrically connected to the base of the transistor Q3 via the resistor R40, the other end of the resistor R39 and the emitter of the transistor Q6 are both connected to the SGND ground terminal, and the emitter of the transistor Q3 is electrically connected to the primary feedback module.

2. The flicker-free, high power factor, single-stage switching power supply according to claim 1, characterized in that: The regulating signal is a first PWM signal; When the control module determines that the minimum value Vo_min of the dynamic voltage signal is less than the preset minimum voltage value, the duty cycle Don of the adjustment signal is increased by one level, and the input module performs a one-level boost adjustment on the dynamic voltage signal generated by the output module; When the control module determines that the minimum value Vo_min of the dynamic voltage signal is equal to the preset minimum voltage value, the duty cycle Don of the adjustment signal remains unchanged, and the input module does not adjust the dynamic voltage signal generated by the output module; When the control module determines that the minimum value Vo_min of the dynamic voltage signal is greater than the preset maximum voltage value, the duty cycle Don of the regulation signal is reduced by one level, and the input module reduces the dynamic voltage signal generated by the output module by one level.

3. The flicker-free, high power factor, single-stage switching power supply according to claim 2, characterized in that: The value of the dynamic voltage signal boosting or reducing by one level is: △V=Vo-Vo_min or △V=Vo_max-Vo; Wherein, Vo is the effective value of the dynamic voltage signal, Vo_min is the minimum value of the dynamic voltage signal, and Vo_max is the maximum value of the dynamic voltage signal.

4. The flicker-free, high power factor, single-stage switching power supply according to claim 2, characterized in that: The chopping signal is a second PWM signal, and the duty cycle of the chopping signal is: Duty=(Vo_min-Vled) / (Vo-Vled); Wherein, Vo_min is the minimum value of the dynamic voltage signal, Vled is the voltage of the load lamp, and Vo is the effective value of the dynamic voltage signal.

5. The flicker-free, high power factor, single-stage switching power supply according to claim 1, characterized in that: The primary feedback module includes a resistor R27, a resistor R28, an optocoupler U3, a resistor R30, a resistor R31, a resistor R35, a resistor R32, a resistor R36, a resistor R37, a capacitor C9, a capacitor C10 and a controllable voltage regulator U4; The reference end of the controllable voltage-stabilizing source U4 is electrically connected to the dynamic voltage regulation module, one end of the resistor R36, one end of the resistor R37, one end of the resistor R35, one end of the capacitor C9, and one end of the capacitor C10 are all electrically connected to the reference end of the controllable voltage-stabilizing source U4, the other end of the capacitor C10 is electrically connected to one end of the resistor R32, the other end of the resistor R32, the other end of the capacitor C9, one end of the resistor R31, and the cathode of the light source of the photoelectric coupler U3 are all electrically connected to the cathode of the controllable voltage-stabilizing source U4, the anode of the controllable voltage-stabilizing source U4, the other end of the resistor R36, and the other end of the resistor R37 are all connected to the SGND ground terminal, the anode of the light source of the photoelectric coupler U3 is electrically connected to one end of the resistor R30, and the other end of the resistor R30, the other end of the resistor R31, and the other end of the resistor R35 are all connected to the power supply voltage; The collector of the light receiver of the photocoupler U3 is connected to the power supply voltage, the emitter of the light receiver of the photocoupler U3 and one end of the resistor R28 are electrically connected to one end of the resistor R27, the other end of the resistor R28 is connected to the GND ground terminal, and the other end of the resistor R27 is electrically connected to the input module.

6. The flicker-free, high power factor, single-stage switching power supply according to claim 1, characterized in that: The current chopping regulation module includes a MOS tube Q2, a resistor R34, a resistor R38, a resistor R41, a transistor Q4 and a transistor Q5; One end of the resistor R41 is electrically connected to the control module, the other end of the resistor R41 and the base of the transistor Q4 are electrically connected to the base of the transistor Q5, the collector of the transistor Q5 is connected to the SGND ground terminal, the collector of the transistor Q4 is connected to the power supply voltage, the emitter of the transistor Q4 and the emitter of the transistor Q5 are electrically connected to one end of the resistor R38, the other end of the resistor R38 and one end of the resistor R34 are electrically connected to the gate of the MOS transistor Q2, the other end of the resistor R34 is electrically connected to the source of the MOS transistor Q2, and the MOS transistor Q2 is connected in series to the negative electrode of the output module through the drain and source.

7. The flicker-free, high power factor, single-stage switching power supply according to claim 1, characterized in that: The dynamic voltage detection module includes a resistor R43 and a resistor R44; the positive electrode of the output module is connected in series with the resistor R43 and the resistor R44 in sequence, and then connected to the SGND ground terminal; the common point of the resistor R43 and the resistor R44 is electrically connected to the control module.

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