A periodic smooth frequency conversion control circuit, switching power supply and electronic device

Abstract

The application belongs to the technical field of power supply, and provides a period smooth frequency conversion control circuit, a switching power supply and an electronic device. The period smooth frequency conversion control circuit comprises a low-frequency voltage gradual change oscillation circuit and a voltage isolation amplification circuit. The low-frequency voltage gradual change oscillation circuit is used to generate a gradual change oscillation voltage signal according to a reference voltage signal. The voltage isolation amplification circuit is connected with the low-frequency voltage gradual change oscillation circuit. The voltage isolation amplification circuit is used to perform isolation and amplification processing on the gradual change oscillation voltage signal to generate a smooth frequency conversion control signal. The period smooth frequency conversion control circuit can change the amplitude and frequency of the output voltage waveform by adjusting the parameters of components, has design flexibility, can meet the needs of customers for different power supply technical specifications, and does not have a fatal negative voltage to an integrated circuit IC. The circuit can protect the control circuit in the rear stage, avoid dangerous out-of-control of the power supply, and avoid failure in a dangerous and dangerous safety specification or burning way.

Description

Technical Field

[0001] This application belongs to the field of power supply technology, and in particular relates to a periodic smooth frequency conversion control circuit, a switching power supply, and electronic equipment. Background Technology

[0002] Fixed-frequency pulse width modulation (PWM) control circuits are widely used in high-frequency switching power supplies, such as flyback switching power supplies, forward switching power supplies, half-bridge switching power supplies, and continuous-mode power factor correction (PFC) circuits. These switching power supply topologies are widely used in industrial, communication, security, power, military, and automation equipment fields due to their high reliability, stable operation, and strong anti-interference capabilities.

[0003] However, the electromagnetic interference (EMI) frequency band of the fixed-frequency pulse width modulation (PWM) control circuit is fixed, which makes the power supply have strong conducted and radiated interference at the operating frequency and its multiples. This means that in order to pass the conducted and radiated interference limits specified by the EMC standards of various countries, the power supply needs to increase the number and cost of filter components, resulting in high material costs and weak competitiveness of such power supplies. Summary of the Invention

[0004] To address the aforementioned technical problems, embodiments of this application provide a periodic smooth frequency conversion control circuit, a switching power supply, and an electronic device, aiming to provide a novel periodic smooth frequency conversion control circuit that solves the problems of high conducted and radiated interference intensity and low reliability in current control circuits.

[0005] A first aspect of this application provides a periodic smooth frequency conversion control circuit, the periodic smooth frequency conversion control circuit comprising:

[0006] A low-frequency voltage gradient oscillation circuit is used to receive a reference voltage signal and generate a gradient oscillation voltage signal based on the reference voltage signal.

[0007] A voltage isolation amplifier circuit is connected to the low-frequency voltage gradual oscillation circuit. It is used to receive the gradual oscillation voltage signal, isolate and amplify the gradual oscillation voltage signal, and generate a smooth frequency conversion control signal.

[0008] In one embodiment, the low-frequency voltage gradient oscillation circuit includes: a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, and a first operational amplifier;

[0009] The first end of the first resistor is connected to the reference voltage terminal. The second end of the first resistor, the first end of the second resistor, and the first end of the fourth resistor are all connected to the non-inverting input pin of the first operational amplifier. The second end of the second resistor and the ground pin of the first operational amplifier are all connected to the reference ground terminal. The output pin of the first operational amplifier, the second end of the fourth resistor, and the first end of the third resistor are all connected together. The power supply pin of the first operational amplifier is connected to the power supply terminal.

[0010] The first terminal of the first capacitor, the second terminal of the third resistor, and the inverting input pin of the first operational amplifier are all connected to the voltage isolation amplifier circuit, and the second terminal of the first capacitor is connected to the reference ground terminal.

[0011] In one embodiment, the low-frequency voltage gradient oscillation circuit further includes: a first diode; the first diode is connected in series between the output pin of the first operational amplifier and the non-inverting pin of the first operational amplifier, and the first diode is connected in series with the fourth resistor.

[0012] In one embodiment, the low-frequency voltage gradient oscillation circuit further includes: a second diode; the second diode is connected in series between the output pin of the first operational amplifier and the inverting input pin of the first operational amplifier, and the second diode is connected in series with the third resistor, and the cathode of the second diode is connected to the output pin of the first operational amplifier.

[0013] In one embodiment, the low-frequency voltage gradient oscillation circuit further includes: a third diode and a fifth resistor; the anode of the third diode is connected to the first terminal of the fifth resistor, the second terminal of the fifth resistor is connected to the output pin of the first operational amplifier, and the cathode of the third diode is connected to the inverting input pin of the first operational amplifier.

[0014] In one embodiment, the low-frequency voltage gradient oscillation circuit further includes: a second capacitor and a third capacitor; the first end and the second end of the second capacitor are respectively connected to the inverting input pin and the non-inverting input pin of the first operational amplifier, the first end of the third capacitor is connected to the non-inverting input pin of the first operational amplifier, and the second end of the third capacitor is connected to the reference ground terminal.

[0015] In one embodiment, the voltage isolation amplifier circuit includes: a second operational amplifier;

[0016] The non-inverting input pin of the second operational amplifier is connected to the low-frequency voltage gradient oscillation circuit. The inverting input pin and the output pin of the second operational amplifier are connected together as the output terminal of the periodic smooth frequency conversion control circuit. The power supply pin of the second operational amplifier is connected to the power supply terminal, and the ground pin of the second operational amplifier is connected to the reference ground terminal.

[0017] A second aspect of this application also provides a switching power supply, the switching power supply including the periodic smooth frequency conversion control circuit described in any of the above embodiments;

[0018] A high-frequency PWM control and drive circuit is provided, wherein the output terminal of the periodic smooth frequency conversion control circuit is connected to the frequency setting terminal of the high-frequency PWM control and drive circuit through an isolation resistor, and the high-frequency PWM control and drive circuit is used to generate a power conversion control signal based on the smooth frequency conversion control signal output by the periodic smooth frequency conversion control circuit.

[0019] A high-frequency power conversion circuit, connected to the high-frequency PWM control and drive circuit, is used to receive the power conversion control signal output by the high-frequency power conversion circuit, and convert the input power supply into the corresponding output power supply according to the power conversion control signal.

[0020] An output signal feedback circuit is connected to the high-frequency power conversion circuit and the high-frequency PWM control and drive circuit, and is used to sample the output current and output voltage of the high-frequency power conversion circuit to obtain a feedback signal and send it to the high-frequency PWM control and drive circuit.

[0021] The high-frequency PWM control and drive circuit is also used to adjust the power conversion control signal according to the feedback signal.

[0022] In one embodiment, the high-level transition voltage value of the low-frequency voltage gradient oscillation circuit is less than the high-level transition voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit.

[0023] The low-frequency voltage transition voltage value of the low-frequency voltage gradient oscillation circuit is greater than the low-frequency voltage transition voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit.

[0024] A third aspect of this application also provides an electronic device, including: a periodic smoothing frequency conversion control circuit as described in any of the above embodiments, or a switching power supply as described in any of the above embodiments.

[0025] The beneficial effects of this application embodiment are as follows: It provides a periodic smooth frequency conversion control circuit, a switching power supply, and an electronic device. The periodic smooth frequency conversion control circuit includes a low-frequency voltage gradual oscillation circuit and a voltage isolation amplifier circuit. The low-frequency voltage gradual oscillation circuit is used to generate a gradual oscillation voltage signal based on a reference voltage signal. The voltage isolation amplifier circuit is connected to the low-frequency voltage gradual oscillation circuit and is used to isolate and amplify the gradual oscillation voltage signal to generate a smooth frequency conversion control signal. This periodic smooth frequency conversion control circuit has design flexibility by adjusting the component parameters. It can not only meet the customer's needs for different power supply technical specifications, but also protect the downstream control circuit, preventing the power supply from failing in a dangerous runaway manner, endangering safety standards, or burning out. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the periodic smoothing frequency conversion control circuit provided in the embodiments of this application. Figure 1 ;

[0027] Figure 2 This is a schematic diagram of the periodic smoothing frequency conversion control circuit provided in the embodiments of this application. Figure 2 ;

[0028] Figure 3 This is a schematic diagram of the periodic smoothing frequency conversion control circuit provided in the embodiments of this application. Figure 3 ;

[0029] Figure 4 This is a schematic diagram of the periodic smoothing frequency conversion control circuit provided in the embodiments of this application. Figure 4 ;

[0030] Figure 5 This is a schematic diagram of a switching power supply provided in an embodiment of this application;

[0031] Figure 6 This is a schematic diagram of the low-frequency window waveforms of voltage VP1 and current IP1 at the first node P1 of the periodic smoothing frequency conversion control circuit provided in the embodiment of this application;

[0032] Figure 7 This is a schematic diagram of the high-frequency window waveforms of IP1, VP2, and VP1 at the first node P1 of the periodic smooth frequency conversion control circuit provided in this application embodiment, near the low-level transition voltage point (approximately 1.3V).

[0033] Figure 8 This is a schematic diagram of the high-frequency window waveforms of IP1, VP2, and VP1 at the first node P1 provided in this application embodiment when the voltage VP1 is near the high-level transition voltage point (around 2.9V). Detailed Implementation

[0034] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0035] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0036] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means one or more, unless otherwise explicitly specified.

[0038] The electromagnetic interference (EMI) frequency band of the fixed-frequency pulse width modulation (PWM) control circuit is fixed, which makes the power supply have strong conducted and radiated interference at the operating frequency and its multiples. As a result, in order to pass the conducted and radiated interference limits specified by the EMC standards of various countries, the power supply needs to increase the number and cost of filter components, resulting in high material costs and weak competitiveness of such power supplies.

[0039] In existing technologies, to avoid the harmful effects of strong conducted and radiated interference at the operating frequency and its multiples of the frequency of power supplies controlled by fixed-frequency PWM, and to address the issue of increased quantity and cost of filtering components required to meet the conducted and radiated interference limits specified in various countries' electromagnetic capacitance (EMC) standards, periodic smoothing frequency conversion control technology is used. This technology injects a low-frequency (typically 200–500 Hz) additional current into a fixed-frequency high-frequency oscillator, allowing the operating frequency of the switching power supply to smoothly vary within a narrow range (e.g., ±7%) around the center frequency. Compared to fixed-frequency PWM control, periodic smoothing frequency conversion control technology effectively reduces the intensity of conducted and radiated interference at specific frequency points, thereby reducing the number and cost of filtering components.

[0040] A high negative voltage exists in the periodic smoothing frequency converter control circuit. If the resistance value of the circuit node between the periodic smoothing frequency converter control circuit and the PWM control circuit decreases abnormally after some environmental factors, the negative voltage at the output of the periodic smoothing frequency converter control circuit will enter the frequency setting pin of the PWM control circuit with a low impedance. This will cause irreversible and serious damage to the main control IC in the PWM control circuit, thereby causing the power supply to fail in a dangerous and uncontrolled manner, endangering safety standards, or even burning out.

[0041] To address the aforementioned technical problems, this application provides a periodic smoothing frequency conversion control circuit 40, which can be applied to switching power supplies. (See also...) Figure 1 As shown, in this embodiment, the periodic smoothing frequency conversion control circuit 40 is connected to the high-frequency PWM control and drive circuit 20 in the switching power supply through an isolation resistor R0. Even if the resistance value of the circuit nodes across the isolation resistor R0 abnormally decreases after exposure to environmental factors, the control chip within the high-frequency PWM control and drive circuit 20 will not suffer irreversible, severe, or permanent damage. The switching power supply will not fail in a dangerous, uncontrolled manner, endangering safety standards, or burn out. Even if the operator discovers a power supply malfunction caused by the aforementioned factors, repair operations can still be performed.

[0042] See Figure 1 As shown, the periodic smooth frequency conversion control circuit 40 includes: a low-frequency voltage gradual oscillation circuit 41 and a voltage isolation amplifier circuit 42. The low-frequency voltage gradual oscillation circuit 41 generates a gradual oscillation voltage signal based on a reference voltage signal. The voltage isolation amplifier circuit 42 is connected to the low-frequency voltage gradual oscillation circuit 41 and is used to isolate and amplify the gradual oscillation voltage signal to generate a smooth frequency conversion control signal, which is output to the high-frequency PWM control and drive circuit 20 to inject low-frequency additional current into the high-frequency PWM control and drive circuit 20. The periodic smooth frequency conversion control circuit 40 can change the amplitude and frequency of the output voltage waveform by adjusting the component parameters, providing design flexibility. It can not only meet the needs of customers for different power supply specifications, but also, since there is no fatal negative voltage in this circuit, it can protect the downstream control circuit and prevent the power supply from failing in a dangerous runaway, endangering safety standards, or burning out.

[0043] In a specific application embodiment, the output terminal of the periodic smooth frequency conversion control circuit 40 is connected to the frequency setting terminal of the high-frequency PWM control and drive circuit 20 through an isolation resistor R0. A timing capacitor is provided between the frequency setting terminal of the high-frequency PWM control and drive circuit 20 and the reference ground terminal. The smooth frequency conversion control signal output by the periodic smooth frequency conversion control circuit 40 can charge and discharge the timing capacitor. The high-frequency PWM control and drive circuit 20 is used to provide a power conversion control signal to the high-frequency power conversion circuit in the switching power supply to control the output power of the high-frequency power conversion circuit. It is also used to adjust the power conversion control signal according to the feedback signal obtained by sampling the high-frequency power conversion circuit.

[0044] In some embodiments, combined with Figure 1 As shown, when the voltage VP1 at the first node P1 is greater than the voltage VP2 at the second node P2, which is the positive terminal of the timing capacitor, the current IP1 flowing through the first node P1 is positive. At this time, the periodic smoothing frequency conversion control circuit 40 charges the timing capacitor through the isolation resistor R0.

[0045] When the voltage VP1 at the first node P1 is less than the voltage VP2 at the second node P2 at the positive terminal of the timing capacitor, the current IP1 flowing through the first node P1 is negative. At this time, the periodic smoothing frequency conversion control circuit 40 discharges the timing capacitor through the isolation resistor R0.

[0046] In this embodiment, the high-level transition voltage value of the voltage VP1 at the first node P1 of the output terminal of the low-frequency voltage gradient oscillation circuit 41 is defined as VR_P1_H, and the low-level transition voltage value is defined as VR_P1_L. The high-level transition voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit 20 is defined as VR_P2_H, and the low-level transition voltage value is defined as VR_P2_L.

[0047] When common environmental problems such as solder dross, foreign matter, stains, moisture, and dust accumulate during the use of the power supply, in order to prevent the external periodic smoothing frequency conversion control circuit 40 from dangerously or permanently damaging the control chip of the high-frequency PWM control and drive circuit 20, and to make the power supply repairable and highly reliable, the circuit parameters can generally be designed according to state 1.

[0048] By setting appropriate component parameters in the low-frequency voltage gradient oscillation circuit 41 in this embodiment, the following state 1 is achieved:

[0049] VR_P1_H<VR_P2_H,VR_P1_L> VR_P2_L1; (State 1)

[0050] In state 1, the highest voltage VR_P1_H of the waveform of the voltage VP1 at the first node P1 output by the low-frequency voltage gradient oscillation circuit 41 is less than the highest voltage VR_P2_H of the waveform of the voltage VP2 at the second node P2 in the high-frequency PWM control and drive circuit 20.

[0051] In state 1, the lowest voltage VR_P1_L of the waveform of the voltage VP1 at the first node P1 output by the low-frequency voltage gradient oscillation circuit 41 is greater than the lowest voltage VR_P2_L of the waveform of the voltage VP2 at the second node P2 in the high-frequency PWM control and drive circuit 20.

[0052] In a specific application embodiment, the high-level transition voltage value VR_P1_H of the voltage waveform at the first node P1 of the output terminal of the low-frequency voltage gradient oscillation circuit 41 is less than the high-level transition voltage value VR_P2_H of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit 20, and the low-level transition voltage value VR_P1_L of the voltage waveform at the first node P1 of the low-frequency voltage gradient oscillation circuit 41 is greater than the low-level transition voltage value VR_P2_L of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit 20. By setting the parameters of the switching power supply, the power supply can be repairable and highly reliable.

[0053] In this embodiment, the voltage VP1 at the first node P1 of the output terminal of the low-frequency voltage gradient oscillation circuit 41 is not less than the negative voltage of the reference ground terminal GND, and the voltage range of VP1 (greater than VR_P1_L, less than VR_P1_H) is always within the range of the upper and lower trigger voltage limits of the internal high-frequency oscillation circuit in the high-frequency PWM control and drive circuit 20 (greater than VR_P2_L, less than VR_P2_H).

[0054] Since the frequency range of the voltage VP2 waveform at the second node P2 is typically chosen to be from tens to hundreds of kilohertz, the waveform at the second node P2 is a high-frequency oscillating voltage waveform. Conversely, the frequency range of the voltage VP1 waveform at the first node P1 is typically chosen to be hundreds of kilohertz, and the waveform at the first node P1 is a low-frequency smooth, gradually changing oscillating voltage waveform. Therefore, within one high-frequency voltage cycle of the waveform at the second node P2, the change in the low-frequency smooth, gradually changing oscillating voltage at the first node P1 is very small, essentially a constant value.

[0055] In one specific application embodiment, the high-frequency PWM control and drive circuit 20 and the periodic smooth frequency conversion control circuit 40 have the same 0 potential reference point, which can improve the stability of the switching power supply during mode switching and avoid the problem of abnormal current direction inside the circuit caused by 0 potential error, which could damage circuit components.

[0056] In one embodiment, see Figure 2 As shown, the low-frequency voltage gradient oscillation circuit 41 includes: a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first capacitor C1, and a first operational amplifier IC41; the first end of the first resistor R1 is connected to the reference voltage terminal VREF; the second ends of the first resistor R1, the first ends of the second resistor R2, and the first ends of the fourth resistor R4 are all connected to the non-inverting input pin of the first operational amplifier IC41; the second end of the second resistor R2 and the ground pin of the first operational amplifier IC41 are all connected to the reference ground terminal GND; the output pin of the first operational amplifier IC41, the second end of the fourth resistor R4, and the first end of the third resistor R3 are all connected; the power supply pin of the first operational amplifier IC41 is connected to the power supply terminal VCC; the first end of the first capacitor C1, the second end of the third resistor R3, and the inverting input pin of the first operational amplifier IC41 are all connected to the voltage isolation amplifier circuit 42; the second end of the first capacitor C1 is connected to the reference ground terminal GND.

[0057] In this embodiment, the low-frequency voltage gradient oscillation circuit 41 consists of a first operational amplifier IC 41 and resistors, capacitors, and diodes (first resistor R1, second resistor R2, third resistor R3, fourth resistor R4, first capacitor C1, etc.) that interact with the pins of the first operational amplifier IC 41 through voltage and current. The first resistor R1 and the second resistor R2 form a voltage divider circuit, which divides the voltage at the reference voltage terminal VREF to obtain a reference voltage output to the non-inverting input pin of the first operational amplifier IC 41. The reference voltage is connected to the non-inverting input pin of the first operational amplifier IC 41 through the first resistor R1. The output pin of the first operational amplifier IC 41 is connected to the non-inverting input pin of the first operational amplifier IC 41 through the fourth resistor R4. The non-inverting input pin of the first operational amplifier IC 41 is also connected to the reference ground terminal GND through the second resistor R2.

[0058] exist Figure 2 In the calculation of the reference voltage divider value VR applied to the non-inverting input pin IC41_3 of the first operational amplifier IC41, the following formula (1) is used:

[0059] VR=[(VIC41_1*R1+VREF*R4)*R2] / (R4*R2+R1*R2+R4*R1);

[0060] R1 is the resistance value of the first resistor R1, R2 is the resistance value of the second resistor R2, R3 is the resistance value of the third resistor R3, R4 is the resistance value of the fourth resistor R4, VREF is the voltage at the reference voltage terminal VREF, and VIC41_1 is the voltage value at the output terminal of the first operational amplifier IC41.

[0061] exist Figure 2In the process, when the voltage value VIC41_1 at the output terminal of the first operational amplifier IC41 is low (approximately 0V), the reference voltage division value VR applied to the non-inverting input pin IC41_3 of the first operational amplifier IC41 is low. This voltage value is the low-level inflection point voltage value VR_L of the reference voltage of the low-frequency voltage gradient oscillation circuit 41.

[0062] Substituting VIC41_1≈0V into Formula 1, we can obtain the following formula (2) for calculating the VR_L voltage value:

[0063] VR_L=VREF*R4*R2 / (R4*R2+R1*R2+R4*R1).

[0064] exist Figure 2 In this circuit, when the voltage value VIC41_1 at the output of the general-purpose first operational amplifier IC41 is high, its typical value is approximately VCC. At this time, the reference voltage division value VR applied to the non-inverting input pin IC41_3 of the first operational amplifier IC41 is relatively high. This voltage value is the high-level inflection point voltage value VR_H of the reference voltage of the low-frequency voltage gradient oscillation circuit 41.

[0065] Substituting VIC41_1≈VCC into formula (1), where VCC is the voltage at the power supply terminal VCC, we can obtain the following formula (3) for calculating the VR_H voltage value:

[0066] VR_H=[(VCC*R1+VREF*R4)*R2] / (R4*R2+R1*R2+R4*R1).

[0067] In one embodiment, the first operational amplifier IC41 can also be replaced by a comparator.

[0068] VR_L is the low-order transition voltage value of the inverting input pin VIC41_2 that causes the voltage value of the output pin IC41_1 of the first operational amplifier IC41 or comparator to jump from 0V or close to 0V to a high voltage value.

[0069] VR_H is the high-level transition voltage value of the inverting input pin VIC41_2, which causes the voltage of the output pin IC41_1 of the first operational amplifier IC41 or comparator to jump from a high voltage value to 0V or close to 0V.

[0070] In some embodiments, VREF is the voltage value of the reference voltage source relative to the reference ground terminal GND, and VCC is the voltage value of the auxiliary power supply relative to the reference ground terminal GND.

[0071] In one embodiment, see Figure 3As shown, the low-frequency voltage gradient oscillation circuit 41 further includes: a first diode D1; the first diode D1 is connected in series between the output pin of the first operational amplifier IC41 and the non-inverting pin of the first operational amplifier IC41, and the first diode D1 is connected in series with the fourth resistor R4.

[0072] In practical applications, the first diode D1 and the fourth resistor R4 are connected in series. The first diode D1 can be connected to the fourth resistor R4 through its anode or its cathode. By changing the connection direction of its anode and cathode, the current direction between the output pin and the non-inverting pin of the first operational amplifier IC41 can be adjusted.

[0073] In one embodiment, combined Figure 3 As shown, the anode of the first diode D1 is connected to the non-inverting pin of the first operational amplifier IC41, the cathode of the first diode D1 is connected to the first terminal of the fourth resistor R4, and the second terminal of the fourth resistor R4 is connected to the output pin of the first operational amplifier IC41.

[0074] In one embodiment, see Figure 4 As shown, the cathode of the first diode D1 is connected to the non-inverting pin of the first operational amplifier IC41, the anode of the first diode D1 is connected to the first terminal of the fourth resistor R4, and the second terminal of the fourth resistor R4 is connected to the output pin of the first operational amplifier IC41.

[0075] In the reference circuit connected to the non-inverting input pin IC41_3 of the first operational amplifier IC41, with Figure 4 The direction shown is connected in series with the first diode D1. VD1 is defined as the forward conduction voltage drop of the first diode D1. This simplifies the calculation formula of VR_L to formula (4), and the calculation formula of VR_H is changed to formula (5):

[0076] VR_L = VREF * R2 / (R2 + R1); (4)

[0077] VR_H={[(VCC-VD1)*R1+VREF*R4]*R2} / (R4*R2+R1*R2+R4*R1); (5)

[0078] In the reference circuit connected to the non-inverting input pin IC41_3 of the first operational amplifier IC41, with Figure 3 Connecting the first diode D1 in series in the direction shown can change the calculation of VR_L to formula (6), and simplify the calculation of VR_H to formula (7):

[0079] VR_L=(VREF*R4+VD1*R1)*R2 / (R4*R2+R1*R2+R4*R1); (6)

[0080] VR_H = VREF * R2 / (R2 + R1); (7)

[0081] exist Figure 2 , Figure 3 , Figure 4 In this circuit, when the output pin IC41_1 of the first operational amplifier IC41 is at a high potential (approximately VCC), the first capacitor C1 connected to the inverting input pin IC41_2 of the first operational amplifier IC41 is charging. The voltage VIC41_2 at the inverting input pin IC41_2 gradually increases. When VIC41_2 reaches the high-level transition voltage VR_H of this oscillator circuit, it triggers the output of the first operational amplifier IC41 to switch from a high voltage value to 0V or close to 0V. In other words, the condition for this oscillator circuit to switch from a high voltage output state to a 0V voltage output state is VIC41_2 > VR_H.

[0082] exist Figure 2 , Figure 3 , Figure 4 In this embodiment, when the output pin IC41_1 of the first operational amplifier IC41 is in a low-potential state, with a voltage of 0V or approximately 0V (e.g., -0.1V to 0.1V), the first capacitor C1 connected to the inverting input pin IC41_2 of the first operational amplifier IC41 is in a discharging state. The voltage VIC41_2 at the inverting input pin IC41_2 gradually decreases. When the voltage VIC41_2 at the inverting input pin IC41_2 reaches the low-level transition voltage VR_L of the low-frequency voltage gradient oscillation circuit 41 in this embodiment, it triggers the output of the first operational amplifier IC41 to jump from 0V or near 0V to a high voltage value. That is, the condition for the low-frequency voltage gradient oscillation circuit 41 in this embodiment to switch from a 0V output state to a high voltage output state is:

[0083] VIC41_2 <VR_L。

[0084] In one embodiment, see Figure 3 As shown, the low-frequency voltage gradient oscillation circuit 41 further includes: a second diode D2; the second diode D2 is connected in series between the output pin of the first operational amplifier IC41 and the inverting input pin of the first operational amplifier IC41, and the second diode D2 is connected in series with the third resistor R3, and the cathode of the second diode D2 is connected to the output pin of the first operational amplifier IC41.

[0085] In some embodiments, the second diode D2 and the third resistor R3 can also be connected after their positions are interchanged without changing the direction of the loop current.

[0086] In one embodiment, see Figure 3 As shown, the low-frequency voltage gradient oscillation circuit 41 also includes: a third diode D3 and a fifth resistor R5; the anode of the third diode D3 is connected to the first end of the fifth resistor R5, the second end of the fifth resistor R5 is connected to the output pin of the first operational amplifier IC41, and the cathode of the third diode D3 is connected to the inverting input pin of the first operational amplifier IC41.

[0087] In some embodiments, the third diode D3 and the fifth resistor R5 can also be connected after their positions are interchanged without changing the direction of the loop current.

[0088] In one embodiment, see Figure 3 As shown, the low-frequency voltage gradient oscillation circuit 41 also includes: a second capacitor C2 and a third capacitor C3; the first and second ends of the second capacitor C2 are respectively connected to the inverting input pin and the non-inverting input pin of the first operational amplifier IC41, the first end of the third capacitor C3 is connected to the non-inverting input pin of the first operational amplifier IC41, and the second end of the third capacitor C3 is connected to the reference ground terminal GND.

[0089] In this embodiment, the second capacitor C2 and the third capacitor C3 serve to suppress interference, ensuring that the low-frequency voltage gradual oscillation circuit 41 can still operate normally in harsh environments such as induced lightning strikes and strong electromagnetic fields. The capacitance values ​​of these capacitors are generally chosen to be relatively small and will not significantly affect the steady-state waveform of the oscillation circuit; therefore, they are not involved in the waveform parameter calculation of the low-frequency voltage gradual oscillation circuit 41 and can be ignored. Figure 2 As shown.

[0090] In some embodiments, the capacitance values ​​of the second capacitor C2 and the third capacitor C3 can be 0uF. In this case, the capacitors are in an open-circuit state, and the capacitor symbols do not need to be drawn in the schematic diagram. Figure 2 As shown.

[0091] In one specific application embodiment, combined with Figure 2 , Figure 3 as well as Figure 4 As shown, the function of the first capacitor C1 is to convert the charging and discharging current acting on it into a gradually changing voltage waveform at the inverting input terminal of the first operational amplifier IC41, so as to realize the oscillation frequency control of the low-frequency voltage gradually changing oscillation circuit 41.

[0092] exist Figure 2 , Figure 3 , Figure 4 In the above, the charging period of the first capacitor C1 is defined as T1, and the discharging period is defined as T2.

[0093] exist Figure 2 In the process, the charging cycle T1 of the first capacitor C1 is calculated as follows (8):

[0094] T1=R3*C1*ln[(VCC-VR_L) / (VCC-VR_H)]; (8)

[0095] exist Figure 2 In the process, the discharge period T2 of the first capacitor C1 is calculated as follows (9):

[0096] T2=R3*C1*ln(VR_H / VR_L); (9)

[0097] exist Figure 2 , Figure 3 , Figure 4 In the calculation of the oscillation frequency F1 of the voltage VIC41_1 at the output pin of the first operational amplifier IC41 or the voltage VIC41_2 at the inverting input pin, it is as follows:

[0098] F1 = 1 / (T1 + T2); (10)

[0099] exist Figure 3 , Figure 4 In this circuit, since the added second diode D2 and third diode D3 have unidirectional conductivity, the third resistor R3 is located alone in the discharge circuit of the first capacitor C1, and the fifth resistor R5 is located alone in the charging circuit of the first capacitor C1. Therefore, the charging time T1 and the discharging time T2 of the first capacitor C1 can be adjusted independently, which can further improve the oscillation waveform of the voltage VIC41_2 at the inverting input pin of the first operational amplifier IC41. The calculation formula will not be repeated here.

[0100] In one embodiment, see Figure 3 As shown, the low-frequency voltage gradient oscillation circuit 41 also includes a sixth resistor R6. The first end of the sixth resistor R6 is connected to the output pin of the first operational amplifier IC41, and the second end of the sixth resistor R6 is connected to the power supply terminal VCC.

[0101] In one embodiment, see Figure 3 As shown, the voltage isolation amplifier circuit 42 includes: a second operational amplifier IC42; the non-inverting input pin of the second operational amplifier IC42 is connected to the low-frequency voltage gradient oscillation circuit 41, the inverting input pin and the output pin of the second operational amplifier IC42 are connected together as the output terminal of the periodic smooth frequency conversion control circuit 40, the power supply pin of the second operational amplifier IC42 is connected to the power supply terminal VCC, and the ground pin of the second operational amplifier IC42 is connected to the reference ground terminal GND.

[0102] In this embodiment, the voltage VIC41_2 of the inverting input pin of the first operational amplifier IC41 in the low-frequency voltage gradient oscillation circuit 41 is output to the non-inverting input pin IC42_3 of the second operational amplifier IC42.

[0103] In one embodiment, see Figure 3 and Figure 4 As shown, the voltage isolation amplifier circuit 42 also includes a fifth capacitor C5, a sixth capacitor C6, and a fourth capacitor C4. The two ends of the fourth capacitor C4 are connected to the non-inverting input pin and the inverting input pin of the second operational amplifier IC42, respectively. The first end of the sixth capacitor C6 is connected to the inverting input pin of the second operational amplifier IC42, and the second end of the sixth capacitor C6 is connected to the reference ground terminal GND. The first end of the fifth capacitor C5 is connected to the non-inverting input pin of the second operational amplifier IC42, and the second end of the fifth capacitor C5 is connected to the reference ground terminal GND.

[0104] In this embodiment, the fifth capacitor C5, the sixth capacitor C6, and the fourth capacitor C4 are used to suppress interference. The capacitance of these capacitors is generally chosen to be relatively small, so the current flowing through the seventh resistor R7 can be ignored relative to the charging and discharging current of the first capacitor C1.

[0105] In some embodiments, the capacitance values ​​of the fifth capacitor C5, the sixth capacitor C6, and the fourth capacitor C4 can be 0uF. In this case, the capacitors are in an open-circuit state, and the capacitor symbols do not need to be drawn in the schematic diagram. Figure 2 As shown.

[0106] In one embodiment, see Figure 3 and Figure 4 As shown, the voltage isolation amplifier circuit 42 also includes an eighth resistor R8, a ninth resistor R9, and a seventh capacitor C7. The first end of the eighth resistor R8 is connected to the reference ground terminal GND. The second end of the eighth resistor R8, the first end of the ninth resistor R9, and the inverting input terminal of the second operational amplifier IC2 are connected together. The second end of the ninth resistor R9 is connected to the output pin of the second operational amplifier IC42. The first end of the seventh capacitor C7 is connected to the output pin of the second operational amplifier IC42, and the second end of the seventh capacitor C7 is grounded.

[0107] In some embodiments, the resistance values ​​of the seventh resistor R7 and the ninth resistor R9 can be 0Ω. In this case, the resistor symbols can be replaced by short-circuiting the connecting wires, and the resistor symbols do not need to be drawn in the schematic diagram. Figure 2 As shown.

[0108] In some embodiments, the capacitance value of the seventh capacitor C7 can be 0uF. In this case, the capacitor is in an open circuit state, and the capacitor symbol does not need to be drawn in the schematic diagram. Figure 2 As shown.

[0109] In some embodiments, the resistance values ​​of the sixth resistor R6 and the eighth resistor R8 can be infinite, equivalent to an open circuit, and can be omitted. The resistor symbols do not need to be drawn in the schematic diagram. Figure 2 As shown.

[0110] In one specific application embodiment, combined with Figure 3 and Figure 4 As shown, the voltage isolation amplifier circuit 42 is a non-inverting amplifier. Its function is to amplify the low-frequency smooth and gradual oscillation voltage waveform VIC41_2 of the inverting input pin IC41_2 of the first operational amplifier IC41 in the low-frequency voltage gradual oscillation circuit 41. Since the non-inverting input pin IC42_3 of the second operational amplifier IC42 has a high impedance, the current flowing through the seventh resistor R7 is very small, and its influence on the circuit oscillation frequency and waveform is negligible. Therefore, the second operational amplifier IC42 plays a role in circuit isolation.

[0111] Meanwhile, the first node P1 of the output terminal of the second operational amplifier IC42 in the voltage isolation amplifier circuit 42 injects a bias current containing a smooth and gradually changing low-frequency component into the frequency control terminal of the high-frequency PWM control and drive circuit 20 in the subsequent stage through the isolation resistor R0, so that the high-frequency PWM drive signal fluctuates smoothly at low frequency within a certain frequency range.

[0112] exist Figure 3 , Figure 4 In the calculation of the voltage VP1 at the first node P1 of the output terminal of the second operational amplifier IC42, it is as follows:

[0113] VP1=VIC41_2*(R9+R8) / R8; (11)

[0114] Where R8 is the resistance value of the eighth resistor R8, R9 is the resistance value of the ninth resistor R9, and VIC41_2 is the voltage of the inverting input pin IC41_2 of the first operational amplifier IC41.

[0115] exist Figure 2 In this circuit, since the ninth resistor R9 and the eighth resistor R8 are selected with extreme values, the second operational amplifier IC42 becomes a voltage follower with a gain of 1, which can isolate the input voltage and amplify the output current. At this time, the calculation of the voltage VP1 at the first node P1 of the output terminal of the second operational amplifier IC42 is simplified to formula (12):

[0116] VP1 = VIC41_2; (12)

[0117] In summary, the low-frequency voltage gradient oscillation circuit 41 in this embodiment can be adjusted by referring to the above formulas (1) to (7) and by selecting the resistance values ​​of the first resistor R1, the second resistor R2, and the fourth resistor R4, and the determined reference voltage VREF and auxiliary power supply voltage VCC values, thereby adjusting the high-level transition voltage value VR_H and the low-level transition voltage value VR_L of the low-frequency smooth gradient oscillation voltage waveform VIC41_2.

[0118] In some embodiments, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 can be adjustable resistors.

[0119] This application also provides a switching power supply, see [link to relevant documentation]. Figure 5 As shown, the switching power supply includes a periodic smoothing frequency conversion control circuit 40, a high-frequency PWM control and drive circuit 20, a high-frequency power conversion circuit 10, and an output signal feedback circuit 30, as described in any of the above embodiments.

[0120] In this embodiment, the output terminal of the periodic smooth frequency conversion control circuit 40 is connected to the frequency setting terminal of the high-frequency PWM control and drive circuit 20 through an isolation resistor. The high-frequency PWM control and drive circuit 20 is used to generate a power conversion control signal based on the smooth frequency conversion control signal output by the periodic smooth frequency conversion control circuit 40. The high-frequency power conversion circuit 10 is connected to the high-frequency PWM control and drive circuit 20. The high-frequency power conversion circuit 10 is used to receive the power conversion control signal output by the high-frequency PWM control and drive circuit 20 and convert the input power supply into the corresponding output power supply according to the power conversion control signal. The output signal feedback circuit 30 is connected to the high-frequency power conversion circuit 10 and the high-frequency PWM control and drive circuit 20. The output signal feedback circuit 30 is used to sample the output current and output voltage of the high-frequency power conversion circuit 10 to obtain a feedback signal and send it to the high-frequency PWM control and drive circuit 20.

[0121] In this embodiment, VI+ is the positive input terminal of the high-frequency power conversion circuit 10, VI- is the negative input terminal of the high-frequency power conversion circuit 10, VO+ is the positive output terminal of the high-frequency power conversion circuit 10, and VO- is the negative output terminal of the high-frequency power conversion circuit 10. The power supply terminal VCC can be the positive terminal of the auxiliary DC power supply, and the reference ground terminal GND can be the negative terminal of the auxiliary DC power supply, serving as a reference voltage at potential 0. The output terminal of the periodic smooth frequency conversion control circuit 40 is connected to the frequency setting terminal of the high-frequency PWM control and drive circuit 20 through an isolation resistor. A timing capacitor is provided between the frequency setting terminal of the high-frequency PWM control and drive circuit 20 and the reference ground terminal GND. The smooth frequency conversion control signal output by the periodic smooth frequency conversion control circuit 40 can charge and discharge the timing capacitor. The high-frequency PWM control and drive circuit 20 is also used to adjust the power conversion control signal according to the feedback signal to achieve power output control of the high-frequency power conversion circuit 10.

[0122] From formulas (1) to (7) in the above embodiments, it can be seen that the high-level transition voltage value VR_H and the low-level transition voltage value VR_L of the low-frequency smooth and gradual oscillation voltage waveform VIC41_2 are both greater than the voltage of the reference ground terminal GND and less than the positive voltage value of the auxiliary power supply voltage VCC.

[0123] From formulas (8) to (12) in the above embodiments, it can be seen that the voltage VP1 at the first node P1 of the low-frequency smooth and gradual oscillating voltage waveform VIC41_2 after passing through the voltage isolation amplifier circuit 42 still maintains the same waveform. All voltages in the VP1 waveform are greater than the reference ground terminal GND and less than the positive voltage value of the auxiliary power supply voltage VCC.

[0124] like Figure 5 As shown, the charging current of the given capacitor C0 in the high-frequency PWM control and drive circuit 20 can be defined as IP2, and the discharging current of the given capacitor C0 can be defined as IP3. The periodic smooth frequency conversion control circuit 40 sets the charging and discharging current of the given capacitor C0 as IP1 through the isolation resistor R0.

[0125] In this embodiment, the periodic smooth frequency conversion control circuit 40 calculates the charging and discharging current IP1 of the given capacitor C0 through the isolation resistor R0 as shown in formula (13):

[0126] IP1 = (VP1 - VP2) / R0; (13)

[0127] As can be seen from formula (13), IP1 is positive when the voltage VP1 at the first node P1 is greater than the voltage VP2 at the second node P2, which is the positive terminal of the timing capacitor C0. At this time, the periodic smoothing frequency conversion control circuit 40 charges the timing capacitor C0 through the isolation resistor R0.

[0128] When the voltage VP1 at the first node P1 is less than the voltage VP2 at the second node P2 at the positive terminal of the timing capacitor C0, IP1 is negative. At this time, the periodic smoothing frequency conversion control circuit 40 discharges the timing capacitor C0 through the isolation resistor R0.

[0129] In this embodiment, the high-level transition voltage value of the waveform of voltage VP1 at the first node P1 of the low-frequency voltage gradient oscillation circuit 41 is defined as VR_P1_H, and its low-level transition voltage value is defined as VR_P1_L. The high-level transition voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit 20 is defined as VR_P2_H, and its low-level transition voltage value is defined as VR_P2_L.

[0130] When common environmental problems such as solder dross, foreign matter, stains, moisture, and dust accumulate during the use of the power supply, in order to prevent the external periodic smoothing frequency conversion control circuit 40 from dangerously or permanently damaging the control chip of the high-frequency PWM control and drive circuit 20, and to make the power supply repairable and highly reliable, the circuit parameters can generally be designed according to state 1.

[0131] By setting appropriate component parameters in the low-frequency voltage gradient oscillation circuit 41 in this embodiment, the following state 1 is achieved:

[0132] VR_P1_H<VR_P2_H,VR_P1_L> VR_P2_L1; (State 1)

[0133] In state 1, the highest voltage VR_P1_H of the waveform of the voltage VP1 at the first node P1 output by the low-frequency voltage gradient oscillation circuit 41 is less than the highest voltage VR_P2_H of the waveform of the voltage VP2 at the second node P2 in the high-frequency PWM control and drive circuit 20.

[0134] In state 1, the lowest voltage VR_P1_L of the waveform of the voltage VP1 at the first node P1 output by the low-frequency voltage gradient oscillation circuit 41 is greater than the lowest voltage VR_P2_L of the waveform of the voltage VP2 at the second node P2 in the high-frequency PWM control and drive circuit 20.

[0135] In one embodiment, in a specific application, the high-level transition voltage value of the low-frequency voltage gradient oscillation circuit 41 can be set to be less than the high-level transition voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit 20, and the low-level transition voltage value of the low-frequency voltage gradient oscillation circuit 41 can be set to be greater than the low-level transition voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit 20. By setting the parameters of the switching power supply, the power supply can be repairable and highly reliable.

[0136] In this embodiment, the voltage VP1 at the first node P1 of the low-frequency voltage gradient oscillation circuit 41 is not less than the negative voltage of the reference ground terminal GND, and the voltage range of VP1 (greater than VR_P1_L, less than VR_P1_H) is always within the range of the upper and lower trigger voltage limits of the internal high-frequency oscillation circuit in the high-frequency PWM control and drive circuit 20 (greater than VR_P2_L, less than VR_P2_H).

[0137] Since the frequency range of the voltage VP2 waveform at the second node P2 is generally selected from tens of kilohertz to hundreds of kilohertz, and the frequency range of the voltage VP1 waveform at the first node P1 is generally selected from hundreds of kilohertz, the change of the low-frequency smooth and gradual oscillating voltage VP1 within a high-frequency voltage cycle of VP2 is very small, equivalent to a constant value.

[0138] See also Figure 6 , Figure 7 , Figure 8 The screenshots shown are of the high and low frequency windows of one design embodiment in this example.

[0139] Since, according to state 1, the voltage range of VP1 (greater than VR_P1_L, less than VR_P1_H) is always within the range of the upper and lower trigger voltage limits of the internal high-frequency oscillation circuit in the high-frequency PWM control and drive circuit 20 (greater than VR_P2_L, less than VR_P2_H), therefore, within one high-frequency voltage oscillation cycle of VP2, the waveform of the current IP1 flowing through resistor R0 will change from the charging state of capacitor C0 at the given time to the discharging state of capacitor C0 at the given time at the VP1 = VP2 voltage point, see as follows. Figure 7 , Figure 8 As shown.

[0140] As in the above embodiment, within a high-frequency oscillation voltage cycle of VP2, the magnitude of the approximately constant low-frequency smooth oscillation voltage VP1 determines the ratio of the charging time period to the discharging time period of the high-frequency timing capacitor C0 through the isolation resistor R0.

[0141] As shown in formula (13), when the voltage value of VP1 is small, within one high-frequency voltage oscillation cycle of VP2, the charging time of the high-frequency timing capacitor C0 through the isolation resistor R0 is short, and the discharging time is long. At this time, the voltage rise slope of the timing capacitor C0 decreases, which lengthens the period during which the timing capacitor C0 charges from the low-level transition voltage VR_P2_L to the high-level transition voltage VR_P2_H. Therefore, the oscillation frequency of the high-frequency oscillation voltage VP1 decreases. See below. Figure 7 As shown.

[0142] As in the above embodiment, when the voltage value of VP1 is large, within one high-frequency voltage oscillation cycle of VP2, the charging time of the high-frequency timing capacitor C0 through the isolation resistor R0 is longer, and the discharging time is shorter. At this time, the voltage rise slope of the timing capacitor C0 increases, shortening the period during which the timing capacitor C0 charges from the low-level transition voltage VR_P2_L to the high-level transition voltage VR_P2_H. Therefore, the oscillation frequency of the "high-frequency oscillation voltage" VP1 increases. Figure 8 As shown.

[0143] As in the above embodiment, by selecting the value of the isolation resistor R0, the ratio of the external current IP1 for charging and discharging the given timing capacitor C0 to the charging current IP2 of the given timing capacitor C0 inside the high-frequency PWM control and drive circuit 20 can be adjusted. This allows for adjustment of the ratio between the frequency range and the center frequency of the switching power supply's cycle smoothing frequency conversion, thereby meeting the EMC requirements and specifications of the power supply in different application scenarios.

[0144] In summary, the voltage and current of the periodic smoothing frequency conversion control circuit 40 or the external control circuit of the switching power supply in this embodiment are safe and controllable at any operating time, and will not cause danger or permanent damage to the internal circuit of the original control chip. Even if the operator discovers a power-related functional abnormality, repair operations can still be performed.

[0145] Therefore, the periodic smoothing frequency conversion control circuit 40 and the switching power supply in this embodiment meet the growing socio-economic development needs of users for power safety, reliability and repairability.

[0146] In one specific embodiment, the following is adopted: Figure 2 The periodic smoothing frequency conversion control circuit 40 shown uses the following voltage setting parameters and component parameters: VREF = 5.1V, VCC = 6V, R0 = 36KΩ, R1 = 20KΩ, R2 = 12KΩ, R4 = 15KΩ, R3 = 27KΩ, C1 = 100nF. The first operational amplifier IC41 and the second operational amplifier IC42 are LM2904. The high-frequency PWM control and drive circuit 20 can be a control chip, model SG2525A. The second node P2 is the 5th pin CT (clock capacitor connection terminal) of the control chip SG2525A.

[0147] The low-frequency window waveform of the voltage VP1 at the first node P1 of the low-frequency voltage gradient oscillation circuit 41 using the above parameters, and the low-frequency window waveform of the charging and discharging current IP1 of the timing capacitor C0 of the control chip in the high-frequency PWM control and drive circuit 20 through the isolation resistor R0, are shown below. Figure 6 As shown.

[0148] like Figure 6As shown, the waveform of the charging and discharging current IP1 flowing through the isolation resistor R0 contains both high-frequency and low-frequency components. The amplitude of its high-frequency component (the width of the upper and lower boundaries of the black solid graph displayed in the low-frequency window) is relatively stable, while its low-frequency component (about 280 Hz) shows a fluctuating state.

[0149] As Figure 6 shown, the typical value of the low turning voltage VR_P2_L of the timing capacitor C0 of the control chip SG2525A in this embodiment is 0.9V. Figure 6 The low point VR_P1_L of the VP1 voltage waveform shown is about 1.3V. The typical value of VR_P2_H of the IC SG2525A is 3.3V. Figure 6 The high point VR_P1_H of the VP1 voltage waveform shown is about 2.9V.

[0150] Therefore, in this embodiment, VR_P1_L > VR_P2_L, VR_P1_H < VR_P2_H, and the VP1 voltage waveform satisfies the above state 1 and the parameter settings in the above embodiment (the high turning voltage value of the low-frequency voltage gradient oscillation circuit 41 is less than the high turning voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit 20, and the low turning voltage value of the low-frequency voltage gradient oscillation circuit 41 is greater than the low turning voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit 20).

[0151] The waveforms of IP1, VP2, and VP1 in the high-frequency window at the voltage VP1 at the first node P1 of the low-frequency voltage gradient oscillation circuit 41 adopting the parameters of the above design embodiment of the present application near the low turning voltage point (about 1.3V) are as Figure 7 shown. At this time, the frequency of VP2 is about 85 kHz.

[0152] The waveforms of IP1, VP2, and VP1 in the high-frequency window at the voltage VP1 at the first node P1 of the low-frequency voltage gradient oscillation circuit 41 adopting the parameters of the above design embodiment of the present application near the high turning voltage point (about 2.9V) are as Figure 8 shown. At this time, the frequency of VP2 is about 95 kHz.

[0153] In summary, the PWM operating frequency of the above design embodiment of the present application changes smoothly in a cycle at a low frequency (about 280 Hz) within the range of about 85 Hz to 95 Hz. It can effectively reduce the EMI electromagnetic interference of the fixed frequency band of 90 Hz. And there is no negative voltage value less than the reference ground terminal GND of the high-frequency PWM control and drive circuit 20 in the periodic smooth frequency conversion control circuit 40 of the present application, and the voltage of the reference ground terminal GND is used as the 0V reference potential.

[0154] Therefore, even if the resistance value of the circuit nodes across the isolation resistor R0 abnormally decreases after environmental factors (such as the presence of solder dross, foreign matter, stains, moisture, or dust accumulation) in the periodic smoothing frequency conversion control circuit 40 or the switching power supply in this embodiment of the application, it will not lead to some of the safety hazards existing in the prior art. For example, in the prior art, if a negative voltage is injected into the control chip under abnormal conditions, it can cause irreversible, serious, and permanent damage to the control chip, leading to power supply failure in a dangerous, uncontrolled manner, endangering safety standards, or even burning out.

[0155] The periodic smoothing frequency conversion control circuit 40 or switching power supply in the above embodiments not only effectively solves the serious safety and reliability problems of the prior art, but also has the flexibility of power supply design. Therefore, the periodic smoothing frequency conversion control circuit 40 in the above embodiments can safely and reliably meet the development trend of the continuous expansion of the application field of switching power supplies due to the rapid development of new industries and technologies in the social economy.

[0156] This application also provides an electronic device, including: a periodic smoothing frequency conversion control circuit 40 as described in any of the above embodiments.

[0157] This application also provides an electronic device, which includes a switching power supply as described in any of the above embodiments.

[0158] The periodic smoothing frequency conversion control circuit 40 in the above embodiments can be applied to power supplies in the fields of server power supplies, communication power supplies, security power supplies, power supplies, military power supplies, automated equipment power supplies, industrial power supplies, LED lighting power supplies, desktop and all-in-one computer power supplies, adapters, chargers, medical power supplies, and precision instruments.

[0159] The periodic smoothing frequency conversion control circuit 40 in the above embodiments can be widely used in a large number of switching power supplies in industries such as industrial, DIN rail, LED lighting, consumer electronics, PC, communications, and servers. Therefore, the periodic smoothing frequency conversion control circuit 40 in the above embodiments can generate significant economic and social benefits and has the prospect of large-scale application.

[0160] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0161] Furthermore, the specific names of each functional unit and module are merely for ease of differentiation and are not intended to limit the scope of protection of this application. The specific working processes of the units and modules in the above system can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0162] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0163] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0164] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A periodic smooth frequency conversion control circuit, characterized in that, Applied to switching power supplies, the periodic smoothing frequency conversion control circuit generates a low-frequency modulation signal with a frequency range of 200~500Hz to fine-tune the operating frequency of the high-frequency PWM control and drive circuit in the switching power supply. The periodic smoothing frequency conversion control circuit is connected to the high-frequency PWM control and drive circuit in the switching power supply via an isolation resistor. The periodic smoothing frequency conversion control circuit includes: A low-frequency voltage gradient oscillation circuit is used to receive a reference voltage signal and generate a gradient oscillation voltage signal based on the reference voltage signal. A voltage isolation amplifier circuit, connected to the low-frequency voltage gradual oscillation circuit, is used to receive the gradual oscillation voltage signal, isolate and amplify the gradual oscillation voltage signal, generate a smooth frequency conversion control signal and output it to the high-frequency PWM control and drive circuit, so as to inject low-frequency additional current into the high-frequency PWM control and drive circuit. The output terminal of the low-frequency voltage gradual oscillation circuit is the first node (P1), and the high-frequency PWM control and drive circuit includes a high-frequency voltage oscillation circuit, the input terminal of which is the second node (P2). The parameter settings of the periodic smooth frequency conversion control circuit satisfy state 1: The voltage high-level transition value VR_P1_H of the first node (P1) is less than the voltage high-level transition value VR_P2_H of the second node (P2), and the voltage low-level transition value VR_P1_L of the first node (P1) is greater than the voltage low-level transition value VR_P2_L of the second node (P2).

2. The periodic smooth frequency conversion control circuit as described in claim 1, characterized in that, The low-frequency voltage gradient oscillation circuit includes: a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, and a first operational amplifier; The first end of the first resistor is connected to the reference voltage terminal. The second end of the first resistor, the first end of the second resistor, and the first end of the fourth resistor are all connected to the non-inverting input pin of the first operational amplifier. The second end of the second resistor and the ground pin of the first operational amplifier are all connected to the reference ground terminal. The output pin of the first operational amplifier, the second end of the fourth resistor, and the first end of the third resistor are all connected together. The power supply pin of the first operational amplifier is connected to the power supply terminal. The first terminal of the first capacitor, the second terminal of the third resistor, and the inverting input pin of the first operational amplifier are all connected to the voltage isolation amplifier circuit, and the second terminal of the first capacitor is connected to the reference ground terminal.

3. The periodic smooth frequency conversion control circuit as described in claim 2, characterized in that, The low-frequency voltage gradient oscillation circuit further includes: a first diode; the first diode is connected in series between the output pin of the first operational amplifier and the non-inverting pin of the first operational amplifier, and the first diode is connected in series with the fourth resistor.

4. The periodic smooth frequency conversion control circuit as described in claim 2, characterized in that, The low-frequency voltage gradient oscillation circuit further includes: a second diode; the second diode is connected in series between the output pin of the first operational amplifier and the inverting input pin of the first operational amplifier, and the second diode is connected in series with the third resistor, and the cathode of the second diode is connected to the output pin of the first operational amplifier.

5. The periodic smooth frequency conversion control circuit as described in claim 2, characterized in that, The low-frequency voltage gradient oscillation circuit further includes: a third diode and a fifth resistor; the anode of the third diode is connected to the first terminal of the fifth resistor, the second terminal of the fifth resistor is connected to the output pin of the first operational amplifier, and the cathode of the third diode is connected to the inverting input pin of the first operational amplifier.

6. The periodic smooth frequency conversion control circuit as described in claim 2, characterized in that, The low-frequency voltage gradient oscillation circuit further includes: a second capacitor and a third capacitor; the first end and the second end of the second capacitor are respectively connected to the inverting input pin and the non-inverting input pin of the first operational amplifier, the first end of the third capacitor is connected to the non-inverting input pin of the first operational amplifier, and the second end of the third capacitor is connected to the reference ground terminal.

7. The periodic smooth frequency conversion control circuit as described in claim 1, characterized in that, The voltage isolation amplifier circuit includes: a second operational amplifier; The non-inverting input pin of the second operational amplifier is connected to the low-frequency voltage gradient oscillation circuit. The inverting input pin and the output pin of the second operational amplifier are connected together as the output terminal of the periodic smooth frequency conversion control circuit. The power supply pin of the second operational amplifier is connected to the power supply terminal, and the ground pin of the second operational amplifier is connected to the reference ground terminal.

8. A switching power supply, characterized in that, The switching power supply includes the periodic smooth frequency conversion control circuit according to any one of claims 1-7; the periodic smooth frequency conversion control circuit is used to generate a low-frequency modulation signal with a frequency range of 200~500Hz to fine-tune the operating frequency of the high-frequency PWM control and drive circuit in the switching power supply. A high-frequency PWM control and drive circuit is provided, wherein the output terminal of the periodic smooth frequency conversion control circuit is connected to the frequency setting terminal of the high-frequency PWM control and drive circuit through an isolation resistor, and the high-frequency PWM control and drive circuit is used to generate a power conversion control signal based on the smooth frequency conversion control signal output by the periodic smooth frequency conversion control circuit. A high-frequency power conversion circuit, connected to the high-frequency PWM control and drive circuit, is used to receive the power conversion control signal output by the high-frequency power conversion circuit, and convert the input power supply into the corresponding output power supply according to the power conversion control signal. An output signal feedback circuit is connected to the high-frequency power conversion circuit and the high-frequency PWM control and drive circuit, and is used to sample the output current and output voltage of the high-frequency power conversion circuit to obtain a feedback signal and send it to the high-frequency PWM control and drive circuit. The high-frequency PWM control and drive circuit is also used to adjust the power conversion control signal according to the feedback signal; The high-level transition voltage value of the low-frequency voltage gradient oscillation circuit is less than the high-level transition voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit. The low-frequency voltage transition voltage value of the low-frequency voltage gradient oscillation circuit is greater than the low-frequency voltage transition voltage value of the high-frequency voltage oscillation circuit in the high-frequency PWM control and drive circuit.

9. An electronic device, characterized in that, include: The periodic smoothing frequency conversion control circuit as described in any one of claims 1-7, or the switching power supply as described in claim 8.

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