Switching power supply voltage compensation circuit and switching power supply

Abstract

The embodiment of the invention provides a switching power supply voltage compensation circuit and a switching power supply. An operational amplifier; the controller is used for determining the load working condition of the switching power supply; if the load working condition is a dynamic load, the reference voltage output port outputs a preset first reference voltage, the control port controls the switch to be switched on, and the second input end inputs a first sampling voltage and a second sampling voltage, so that the voltage compensation module outputs a negative compensation signal; and if the load condition is a static load, the reference voltage output port outputs a second reference voltage, the control port controls the switch to be switched off, and the second input end inputs a first sampling voltage, so that the voltage compensation module outputs a positive compensation signal. According to the switching power supply voltage compensation circuit, different voltage compensation can be carried out according to different load working conditions, line voltage drop caused by cable impedance can be compensated, and the dynamic load working condition can be optimized.

Description

Technical Field

[0001] This application relates to the field of switching power supply technology, and in particular to a switching power supply voltage compensation circuit and a switching power supply. Background Technology

[0002] Switching power supplies are typically connected to electrical appliances (i.e., loads) via cables. Due to cable impedance, the voltage at the cable terminals can be lower than the power supply's output voltage, potentially causing undervoltage at the appliance's input and preventing it from functioning properly. Therefore, power supplies usually compensate for this undervoltage by adding voltage compensation at the cable terminals.

[0003] However, adding voltage compensation at the power supply end can worsen dynamic load conditions. Summary of the Invention

[0004] This application provides a switching power supply voltage compensation circuit and a switching power supply, which can perform different voltage compensations according to different load conditions. It can compensate for line voltage drop caused by cable impedance and optimize dynamic load conditions.

[0005] This application provides a switching power supply voltage compensation circuit, including: A voltage compensation module is used to connect to the input side of the switching power supply; An operational amplifier includes a first input terminal, a second input terminal, and an output terminal. The second input terminal is connected to a first sampling circuit and to a second sampling circuit via a switch. The first sampling circuit obtains a first sampling voltage based on the output voltage of a switching power supply, and the second sampling circuit obtains a second sampling voltage based on the load current of the switching power supply. The output terminal is connected to the voltage compensation module. The controller includes a voltage sampling port, a control port, and a reference voltage output port. The voltage sampling port is connected to the second sampling circuit, the control port is connected to the switch, and the reference voltage output port is connected to the first input terminal. The controller is used for: The load condition of the switching power supply is determined based on the second sampled voltage, and the load condition includes static load and dynamic load. If the load condition is a dynamic load, the reference voltage output port outputs a preset first reference voltage, the control port controls the switch to be turned on, and the second input terminal inputs the first sampling voltage and the second sampling voltage, so that the voltage compensation module outputs a negative compensation signal; If the load condition is a static load, the reference voltage output port outputs a second reference voltage, which is obtained based on the first reference voltage and the second sampled voltage. The control port controls the switch to open, and the second input terminal inputs the first sampled voltage, so that the voltage compensation module outputs a positive compensation signal.

[0006] In some embodiments, the controller is used to: The load current of the switching power supply is obtained based on the second sampled voltage; If the change in load current within a preset time period is greater than the first current threshold, then the load condition is determined to be a dynamic load. If the change in load current within a preset time period is less than the second current threshold, then the load condition is determined to be a static load, wherein the second current threshold is less than or equal to the first current threshold.

[0007] In some embodiments, the second reference voltage is obtained according to the following formula: VREF_1 = VREF_0 + K2 × Vcs Wherein, VREF_1 is the second reference voltage, VREF_0 is the first reference voltage, Vcs is the second sampling voltage, and K2 is a preset parameter greater than 0.

[0008] In some embodiments, the first sampling circuit includes a first resistor and a second resistor. One end of the first resistor is connected to the output side of the switching power supply, the other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor is grounded, and the second input terminal is connected between the first resistor and the second resistor.

[0009] In some embodiments, the second sampling circuit includes a third resistor connected between the output side of the switching power supply and the load.

[0010] In some embodiments, the second sampling circuit further includes an analog-to-digital converter connected between the voltage sampling port and the third resistor.

[0011] In some embodiments, the switching power supply voltage compensation circuit further includes a digital-to-analog converter connected between the reference voltage output port and the first input terminal.

[0012] In some embodiments, the voltage compensation module includes: An optocoupler is connected to the output terminal of the operational amplifier and the output side of the switching power supply. A pulse width modulation chip is connected to the optocoupler; The switching unit is connected to the pulse width modulation chip and the input side of the switching power supply.

[0013] This application embodiment also provides a switching power supply, including: A power supply circuit, including a mutually coupled input side and an output side; In any of the voltage compensation circuits described above, the voltage compensation module is connected to the input side, and the operational amplifier and the controller are both connected to the output side.

[0014] In some embodiments, when the voltage compensation module outputs a negative compensation signal, the output voltage on the output side is greater when the load is unloaded than when the load is fully loaded.

[0015] When the voltage compensation module outputs a positive compensation signal, the output voltage on the output side when the load is unloaded is less than the output voltage when the load is fully loaded.

[0016] In the switching power supply voltage compensation circuit of this application embodiment, the controller can perform different control processes for different load conditions. Under static load conditions, the voltage compensation module performs positive compensation, increasing the output voltage of the switching power supply and compensating for the line voltage drop caused by cable impedance. Under dynamic load conditions, the voltage compensation module performs negative compensation, suppressing the changing trend of the switching power supply output voltage and avoiding excessively high or low output voltage, thus stabilizing the output voltage within a controllable range and optimizing the dynamic load conditions of the switching power supply. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the switching power supply voltage compensation circuit according to an embodiment of this application.

[0019] Figure 2 This is a structural example diagram of a switching power supply voltage compensation circuit according to an embodiment of this application.

[0020] Figure 3 This is a schematic diagram of the switching power supply according to an embodiment of this application.

[0021] Figure 4 This is a schematic diagram of the working waveform of the switching power supply according to an embodiment of this application. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0023] This application provides a switching power supply voltage compensation circuit that can compensate the output voltage of the switching power supply, thereby compensating for the line voltage drop caused by cable impedance, and can perform different compensations according to different operating conditions of static load and dynamic load, thereby optimizing the dynamic load operating conditions.

[0024] refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a switching power supply voltage compensation circuit 100 according to an embodiment of this application. The switching power supply voltage compensation circuit 100 includes a voltage compensation module 10, an operational amplifier U2, a first sampling circuit 20, a second sampling circuit 30, and a controller 40.

[0025] The voltage compensation module 10 is used to connect to the input side of the switching power supply. As understood, the switching power supply includes an input side and an output side, which are coupled together through the primary and secondary windings of a transformer. The output side is connected to the load via a cable. Electrical energy input to the input side is coupled to the output side via the transformer, and then transmitted from the output side to the load via the cable to power the load. The voltage compensation module 10 can compensate the voltage on the input side of the switching power supply, thereby compensating for the output voltage on the output side of the switching power supply, offsetting the line voltage drop caused by cable impedance, ensuring that the voltage input to the load is within the load's operating voltage range, preventing undervoltage conditions, and enabling the load to operate normally.

[0026] Operational amplifier U2 includes a first input terminal a, a second input terminal b, and an output terminal c. In some embodiments, the first input terminal a can be a non-inverting input (+), and the second input terminal b can be an inverting input (-). The second input terminal b is connected to a first sampling circuit 20 and, via switch S, to a second sampling circuit 30. Both the first sampling circuit 20 and the second sampling circuit 30 are used to sample the voltage at the output of the switching power supply. Specifically, the first sampling circuit 20 obtains a first sampling voltage based on the output voltage of the switching power supply, and the second sampling circuit 30 obtains a second sampling voltage based on the load current of the switching power supply. The output terminal c is connected to a voltage compensation module 10. The output terminal c is used to output a signal to the voltage compensation module 10, enabling the voltage compensation module 10 to compensate the voltage at the input of the switching power supply. In practical applications, the switch S can be a switch in the form of electronic components such as a MOSFET or a transistor; for example, it can be a MOSFET.

[0027] The controller 40 includes a voltage sampling port 41, a control port 42, and a reference voltage output port 43. The voltage sampling port 41 is connected to the second sampling circuit 30 and is used to input a second sampled voltage. The control port 42 is connected to the switch S and is used to output a control signal to the switch S to control the switch S to be turned on or off. The reference voltage output port is connected to the first input terminal a of the operational amplifier U2 and is used to input a reference voltage to the first input terminal a. In some embodiments, the controller 40 can be an MCU (Micro Control Unit).

[0028] The controller 40 is used for: The load condition of the switching power supply is determined based on the second sampling voltage obtained from the second sampling circuit 30. The load condition includes static load and dynamic load. If the load condition is a dynamic load, the reference voltage output port 43 outputs the preset first reference voltage, the control port 42 controls the switch S to turn on, and the second input terminal b of the operational amplifier U2 inputs the first sampling voltage and the second sampling voltage, so that the voltage compensation module 10 outputs a negative compensation signal. If the load condition is a static load, the reference voltage output port 43 outputs a second reference voltage. The second reference voltage is obtained based on the first reference voltage and the second sampled voltage. The control port 42 controls the switch S to open, and the second input terminal b of the operational amplifier U2 inputs the first sampled voltage, so that the voltage compensation module 10 outputs a positive compensation signal.

[0029] The load conditions of a switching power supply include static load and dynamic load. Static load refers to a state where the load power remains relatively constant. In this state, the load power may fluctuate slightly, but the overall power is relatively constant. Dynamic load refers to a state where the load power changes significantly, occurring within a short period of time.

[0030] For example, taking a laptop's power adapter as an example, the load is the laptop itself. When the laptop is running applications stably, such as playing video without other applications starting or ending, the laptop's processing power and screen display remain relatively constant; this is a static load. However, when high-power applications start or end, such as suddenly launching or exiting a large game application, the laptop's processing power and screen display change drastically, resulting in a significant change in the laptop's power consumption; this is a dynamic load.

[0031] The controller 40 determines the load condition of the switching power supply based on the second sampled voltage obtained from the second sampling circuit 30, and performs different control processing for different load conditions.

[0032] In some embodiments, the controller 40 determines the load condition of the switching power supply by: obtaining the load current of the switching power supply based on the second sampling voltage; if the change value of the load current within a preset time period is greater than the first current threshold, then the load condition is determined to be a dynamic load; if the change value of the load current within a preset time period is less than the second current threshold, then the load condition is determined to be a static load, wherein the second current threshold is less than or equal to the first current threshold.

[0033] Understandably, the second sampling circuit 30 obtains the second sampling voltage based on the load current of the switching power supply. Therefore, the controller 40 can obtain the load current of the switching power supply based on the second sampling voltage, and further obtain the change value of the load current within a preset time period. The load current reflects the real-time power of the load, and the change value of the load current reflects the change in load power. The preset time period can be set empirically or according to actual needs. For example, in one example, the preset time period can be 100ms, and the sampling frequency of the second sampling circuit 30 can be 1kHz, that is, sampling is performed every 1ms.

[0034] The controller 40 compares the change in load current within a preset time period with a first current threshold and a second current threshold. The first and second current thresholds can be set empirically or based on actual needs, with the second current threshold being less than or equal to the first current threshold. For example, taking a laptop power adapter as an example, with a 300W power supply, a rated output of 20V and 15A, and a cable impedance of 40mΩ, the first current threshold can be set to 5A, and the second current threshold to 1A. If the change in load current within the preset time period is greater than the first current threshold (e.g., a change greater than 5A within 100ms), it indicates a significant power change in the load, thus classifying the load as a dynamic load. If the change in load current within the preset time period is less than the second current threshold (e.g., a change less than 1A within 100ms), it indicates a very small power change in the load, thus classifying the load as a static load. It should be noted that in practical applications, the first sampling circuit 20 and the second sampling circuit 30 continuously sample at their respective sampling frequencies, and the controller 40's judgment is also continuous.

[0035] After determining the load condition of the switching power supply, the controller 40 performs different control processing for different load conditions. Specifically, if the load condition is a dynamic load, the reference voltage output port 43 outputs a preset first reference voltage, and the control port 42 controls the switch S to turn on. The first reference voltage can be set according to actual needs; for example, in one example, the first reference voltage can be 2.5V. In this case, the first input terminal a of the operational amplifier U2 receives the first reference voltage, and the second input terminal b receives the first sampled voltage and the second sampled voltage; that is, the second input terminal b receives the superimposed voltage of the first and second sampled voltages. Based on the input first reference voltage and the superimposed voltage, the operational amplifier U2 outputs a drive signal to the voltage compensation module 10, causing the voltage compensation module 10 to output a negative compensation signal. The negative compensation signal can suppress the changing trend of the switching power supply output voltage, or reduce the amplitude of the switching power supply output voltage change, avoiding situations where the output voltage is too high (exceeding the upper limit voltage) or too low (below the lower limit voltage), stabilizing the output voltage within a controllable range, thereby optimizing the dynamic load condition of the switching power supply. For example, when the output voltage of the switching power supply increases, the negative compensation signal can suppress the increasing trend of the output voltage, reduce the increase in the output voltage, and prevent the output voltage from being too high (exceeding the upper limit voltage); when the output voltage of the switching power supply decreases, the negative compensation signal can suppress the decreasing trend of the output voltage, reduce the decrease in the output voltage, and prevent the output voltage from being too low (below the lower limit voltage).

[0036] If the load condition is a static load, the reference voltage output port 43 outputs a second reference voltage, and the control port 42 controls the switch S to open. The second reference voltage is obtained based on the first reference voltage and the second sampled voltage, and the second reference voltage is greater than the first reference voltage. In this case, the second reference voltage is input to the first input terminal a of operational amplifier U2, and the first sampled voltage is input to the second input terminal b. Based on the input second reference voltage and the first sampled voltage, operational amplifier U2 outputs a drive signal to the voltage compensation module 10, causing the voltage compensation module 10 to output a positive compensation signal. The positive compensation signal increases the output voltage of the switching power supply by a certain margin, thereby compensating for the line voltage drop caused by the impedance of the cable between the switching power supply and the load, ensuring that the voltage input to the load is within the load's operating voltage range, and preventing undervoltage conditions.

[0037] In some embodiments, the second reference voltage is obtained according to the following formula: VREF_1 = VREF_0 + K2 × Vcs Where VREF_1 is the second reference voltage, VREF_0 is the first reference voltage (for example, VREF_0 can be 2.5V), Vcs is the second sampling voltage, and K2 is a preset parameter greater than 0. K2 can be understood as the preset compensation ratio.

[0038] In some embodiments, reference Figure 2 , Figure 2 This is a structural example diagram of a switching power supply voltage compensation circuit 100 according to an embodiment of this application.

[0039] The controller 40 is an MCU, which includes a voltage sampling port VCS, a control port G1, and a reference voltage output port VREF. The voltage sampling port VCS is connected to the second sampling circuit 30, the control port G1 is connected to the switch S, and the reference voltage output port VREF is connected to the first input terminal a of the operational amplifier U2.

[0040] The first sampling circuit 20 includes a first resistor R1 and a second resistor R2. One end of the first resistor R1 is connected to the output side of the switching power supply, whose output voltage can be represented as V0. The output voltage V0 is input through one end of the first resistor R1. The other end of the first resistor R1 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is grounded. The second input terminal b of the operational amplifier U2 is connected between the first resistor R1 and the second resistor R2. Therefore, the first sampling circuit 20 can obtain a first sampling voltage based on the output voltage of the switching power supply. The sampling ratio of the first sampling circuit 20 can be expressed as K1 = R2 / (R1 + R2), and the first sampling voltage can be expressed as V1 = V0 × R2 / (R1 + R2), where R1 and R2 represent the resistance values ​​of the first resistor R1 and the second resistor R2, respectively.

[0041] The second sampling circuit 30 includes a third resistor Rcs. The third resistor Rcs is connected between the output side of the switching power supply and the load. Therefore, the second sampling circuit 30 can obtain a second sampling voltage based on the load current of the switching power supply. The second sampling voltage can be expressed as Vcs = Rcs × I0, where Rcs represents the resistance value of the third resistor Rcs, and I0 represents the load current on the output side of the switching power supply.

[0042] In some embodiments, the second sampling circuit 30 further includes an analog-to-digital converter (ADC) connected between the voltage sampling port VCS of the MCU and the third resistor Rcs. It is understood that the MCU input is a digital signal, while the signal sampled through the third resistor Rcs is an analog signal. Therefore, the analog signal sampled through the third resistor Rcs can be converted into a digital signal by the ADC and input to the voltage sampling port VCS of the MCU.

[0043] In some embodiments, the voltage compensation circuit 100 further includes a digital-to-analog converter (DAC) connected between the reference voltage output port VREF of the MCU and the first input terminal a of the operational amplifier U2. It is understood that the MCU outputs a digital signal, while the operational amplifier U2 inputs an analog signal. Therefore, the digital signal output from the reference voltage output port VREF of the MCU can be converted into an analog signal by the DAC and input to the first input terminal a of the operational amplifier U2.

[0044] In some embodiments, the switching power supply voltage compensation circuit 100 further includes a compensation network 50, which is connected between the second input terminal b of the operational amplifier U2 and the voltage compensation module 10. The compensation network 50 can compensate for zeros and poles, achieving zero static error. In some embodiments, the compensation network 50 includes a resistor R3, a capacitor C4, and a capacitor C5. One end of the resistor R3 is connected to the second input terminal b of the operational amplifier U2, and the other end of the resistor R3 is connected to one end of the capacitor C5, which in turn is connected to the voltage compensation module 10. One end of the capacitor C4 is connected to the second input terminal b of the operational amplifier U2, and the other end is connected to the voltage compensation module 10.

[0045] In some embodiments, the voltage compensation module 10 includes an optocoupler U3, a pulse width modulation chip (PWM IC) U1, and a switching unit Q1. The optocoupler U3 is connected to the output terminal c of the operational amplifier U2 and the output side of the switching power supply. Furthermore, the optocoupler U3 is also connected to the compensation network 50. The pulse width modulation chip U1 is connected to the optocoupler. The switching unit Q1 is connected to the pulse width modulation chip U1 and the input side of the switching power supply.

[0046] Specifically, optocoupler U3 includes a light-emitting diode (LED) and a phototransistor, which are coupled to the LED via optical signals. The positive terminal of the LED is connected to the output side of the switching power supply for input voltage V0, for example, through resistor R4. The negative terminal of the LED is connected to the output terminal c of operational amplifier U2 and to compensation network 50. The collector of the phototransistor is connected to pulse width modulation chip U1, and the emitter of the phototransistor is grounded. Understandably, different output voltages at the output terminal c of operational amplifier U2 can change the voltage of the LED, thereby changing the LED current and further affecting the phototransistor current.

[0047] The pulse width modulation chip U1 includes a feedback port FB, a drive port Vg, a voltage port Vcc, and a ground port GND. The feedback port FB is connected to the collector of a phototransistor to obtain its voltage. The drive port Vg is connected to a switching unit Q1 to output a pulse signal, thereby turning the switching unit Q1 on or off. The ground port GND is grounded, and a capacitor C3 is connected between the voltage port Vcc and the ground port GND. The pulse width modulation chip U1 can adjust the duty cycle of the pulse signal output from the drive port Vg based on the voltage signal from the feedback port FB.

[0048] Switching unit Q1 is the main switching transistor of the switching power supply. The control terminal of switching unit Q1 is connected to the drive port Vg of pulse width modulation chip U1. Pulse width modulation chip U1 controls the energy input to the input side of the switching power supply by controlling the duty cycle of the pulse signal output to switching unit Q1, thereby controlling the output voltage on the output side. In some embodiments, switching unit Q1 is a MOSFET. The gate of the MOSFET is connected to the drive port Vg of pulse width modulation chip U1, the source of the MOSFET is grounded, and the drain of the MOSFET is connected to the input side of the switching power supply.

[0049] The working principle of the switching power supply voltage compensation circuit 100 in this embodiment is as follows: The MCU determines the load condition based on the load current at the output side of the switching power supply and performs different control processing for different load conditions to change the output voltage of operational amplifier U2. Specifically, under dynamic load conditions, the MCU outputs a first reference voltage and controls switch S to be turned on; under static load conditions, the MCU outputs a second reference voltage higher than the first reference voltage and controls switch S to be turned off. When the output voltage of operational amplifier U2 changes, the voltage and current of the LED in optocoupler U3 also change, further changing the current of the phototransistor, thus changing the voltage at the feedback port FB of pulse width modulation chip U1. Based on the different voltage signals at the feedback port FB, pulse width modulation chip U1 adjusts the duty cycle of the pulse signal output from the drive port Vg, thereby controlling the energy input to the switching power supply input side to control the output voltage of the switching power supply output side. Therefore, under both dynamic and static load conditions, pulse width modulation chip U1 can output pulse signals with different duty cycles.

[0050] In practical applications, under dynamic load conditions, the output voltage of a switching power supply exhibits both undershoot and overshoot. For example, when the load switches from full load to no load, the output voltage overshoots, resulting in an excessively high output voltage; conversely, when the load switches from no load to full load, the output voltage undershoots, resulting in an excessively low output voltage. Under dynamic load conditions, the voltage compensation module 10 needs to output a negative compensation signal. When the output voltage overshoots, the pulse width modulation chip U1 can reduce the duty cycle of the pulse signal (in this case, the pulse signal with a reduced duty cycle can be understood as the aforementioned negative compensation signal), reducing the on-time of the MOSFET Q1, thereby reducing the overshoot amplitude of the output voltage and achieving negative compensation. When the output voltage undershoots, the pulse width modulation chip U1 can increase the duty cycle of the pulse signal (in this case, the pulse signal with an increased duty cycle can be understood as the aforementioned negative compensation signal), increasing the on-time of the MOSFET Q1 and achieving negative compensation. Under static conditions, the voltage compensation module 10 needs to output a positive compensation signal. In this case, the pulse width modulation chip U1 can increase the duty cycle of the pulse signal (in this case, the pulse signal with increased duty cycle can be understood as the positive compensation signal mentioned above), increase the turn-on time of the MOSFET Q1, and achieve positive compensation for the output voltage of the switching power supply.

[0051] Under dynamic load conditions, the first input terminal a of operational amplifier U2 receives the first reference voltage VREF_0, and the second input terminal b receives the superposition voltage of the first sampling voltage V1 and the second sampling voltage Vcs: V1 + Vcs = V0 × R2 / (R1 + R2) + Rcs × I0. Based on the fact that the signals at the non-inverting and inverting inputs of operational amplifier U2 are equal, we can obtain Equation 1. From Equation 1, we can derive Equation 2: Formula 1: VREF_0=V0×R2 / (R1+R2)+Rcs×I0 Formula 2: V0=(R1+R2) / R2×(VREF_0- Rcs×I0) As can be seen from Formula 2, the larger the load current I0 on the output side of the switching power supply, the lower the output voltage V0, thus achieving a negative compensation effect.

[0052] Under static load conditions, the first input terminal a of operational amplifier U2 receives the second reference voltage VREF_1, where VREF_1 = VREF_0 + K2 × Vcs, and the second input terminal b receives the first sampling voltage V1, where V1 = V0 × R2 / (R1 + R2). Based on the fact that the signals at the non-inverting and inverting inputs of operational amplifier U2 are equal, we can obtain Equation 3. From Equation 3, we can derive Equation 4: Formula 3: VREF_0+K2×Vcs= V0×R2 / (R1+R2) Formula 4: V0=(R1+R2) / R2×(VREF_0+K2×Vcs) As can be seen from Formula 4, the larger the load current I0 on the output side of the switching power supply, the larger the second sampling voltage Vcs, and the higher the output voltage V0, thus achieving a positive compensation effect.

[0053] This application also provides a switching power supply. (See reference...) Figure 3 , Figure 3 This is a schematic diagram of the structure of a switching power supply according to an embodiment of this application. The switching power supply includes the voltage compensation circuit 100 and the power supply circuit 200 described above. The power supply circuit 200 is connected to the voltage compensation circuit 100 and is connected to the load 300 via a cable.

[0054] The power supply circuit 200 includes an input side and an output side that are coupled together. The input side includes an AC power supply (AC), a rectifier bridge, a capacitor C1, and the primary winding of a transformer T, connected in sequence. The output side includes the secondary winding of the transformer T, a capacitor C2, and an interface, connected in sequence. Capacitor C2 is connected in parallel with the secondary winding; therefore, the voltage across capacitor C2 is the output voltage of the transformer T, which is also the output voltage V0 of the power supply circuit 200. The interface on the output side is connected to the load 300 via a cable.

[0055] The voltage compensation module 10 of the voltage compensation circuit 100 is connected to the input side of the power supply circuit 200, and the operational amplifier U2 and the controller 40 are both connected to the output side of the power supply circuit 200. Specifically, the switching unit Q1 of the voltage compensation module 10 is connected to the primary winding of the transformer T, the operational amplifier U2 is connected to the secondary winding of the transformer T through the first sampling circuit 20, and the controller 40 (MCU) is connected to the secondary winding of the transformer T through the second sampling circuit 30. It can be understood that the third resistor Rcs of the second sampling circuit 30 can be connected between the secondary winding of the transformer T and the interface.

[0056] Under dynamic load conditions, when the voltage compensation module 10 outputs a negative compensation signal, the load current I0 on the output side of the power supply circuit 200 when the load is unloaded is less than the load current I0 when the load is fully loaded. According to formula 2 in the above embodiment, the output voltage V0 on the output side when the load is unloaded is greater than the output voltage V0 when the load is fully loaded, thus achieving a negative compensation effect. Under static load conditions, when the voltage compensation module 10 outputs a positive compensation signal, the load current I0 on the output side of the power supply circuit 200 when the load is unloaded is less than the load current I0 when the load is fully loaded. According to formula 4 in the above embodiment, the output voltage V0 on the output side when the load is unloaded is less than the output voltage V0 when the load is fully loaded, thus achieving a positive compensation effect.

[0057] refer to Figure 4 , Figure 4This is a schematic diagram of the working waveform of the switching power supply according to an embodiment of this application. Figure 4 In this context, I0 represents the load current, V0 represents the output voltage, and VREF represents the reference voltage input to the first input terminal a of operational amplifier U2. Figure 4 Taking the 300W power adapter of the aforementioned laptop as an example, the full load current of the power adapter is 15A.

[0058] Where t0 is the initial time, the initial time is the dynamic load condition, and the voltage compensation module 10 performs negative compensation. The period between t0 and t1 lasts for 50ms, the load is unloaded and the load current is 0A. At time t1, the load suddenly changes, and the output voltage V0 becomes unbalanced. Due to the negative compensation, the V0 imbalance is suppressed, so that the minimum voltage of V0 is higher and the input voltage (line terminal voltage) of the appliance meets the voltage range requirements.

[0059] The load is fully loaded for 50ms between t1 and t2. The load current is, for example, 15A. At time t1, a change in current is detected. The load is in dynamic condition. The reference voltage VREF is lower than the no-load condition. At time t2, the load changes abruptly, and the output voltage V0 overshoots. Due to the presence of negative compensation, the overshoot of V0 is suppressed, resulting in a lower maximum voltage of V0. The input voltage (line terminal voltage) of the appliance meets the voltage range requirements.

[0060] The time interval between t2 and t3 is 50ms. At time t2, the load returns to no load, and the load current suddenly drops to 0A, which meets the dynamic load condition, so negative compensation continues. At time t3, the load suddenly changes, and the load current suddenly drops to 15A, which also meets the dynamic load condition, so negative compensation continues.

[0061] For 100ms between t3 and t4, the load current remains at 15A, and no change in load current exceeding 1A (second current threshold) is detected, which meets the static load condition. At t4, the system switches to positive compensation mode to perform positive compensation on the output voltage V0, thereby increasing the output voltage V0.

[0062] Depend on Figure 4 As can be seen, the switching power supply of this application embodiment can effectively suppress output voltage offset and overshoot under dynamic load conditions, thus optimizing the dynamic load conditions of the switching power supply.

[0063] In the description of this application, it should be understood that terms such as “first” and “second” are used only to distinguish similar objects and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0064] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0065] The voltage compensation circuit and switching power supply provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A voltage compensation circuit for a switching power supply, characterized in that, include: A voltage compensation module is used to connect to the input side of the switching power supply; An operational amplifier includes a first input terminal, a second input terminal, and an output terminal. The second input terminal is connected to a first sampling circuit and to a second sampling circuit via a switch. The first sampling circuit obtains a first sampling voltage based on the output voltage of a switching power supply, and the second sampling circuit obtains a second sampling voltage based on the load current of the switching power supply. The output terminal is connected to the voltage compensation module. The controller includes a voltage sampling port, a control port, and a reference voltage output port. The voltage sampling port is connected to the second sampling circuit, the control port is connected to the switch, and the reference voltage output port is connected to the first input terminal. The controller is used for: The load condition of the switching power supply is determined based on the second sampled voltage, and the load condition includes static load and dynamic load. If the load condition is a dynamic load, the reference voltage output port outputs a preset first reference voltage, the control port controls the switch to be turned on, and the second input terminal inputs the first sampling voltage and the second sampling voltage, so that the voltage compensation module outputs a negative compensation signal; If the load condition is a static load, the reference voltage output port outputs a second reference voltage, which is obtained based on the first reference voltage and the second sampled voltage. The control port controls the switch to open, and the second input terminal inputs the first sampled voltage, so that the voltage compensation module outputs a positive compensation signal.

2. The switching power supply voltage compensation circuit according to claim 1, characterized in that, The controller is used for: The load current of the switching power supply is obtained based on the second sampled voltage; If the change in load current within a preset time period is greater than the first current threshold, then the load condition is determined to be a dynamic load. If the change in load current within a preset time period is less than the second current threshold, then the load condition is determined to be a static load, wherein the second current threshold is less than or equal to the first current threshold.

3. The switching power supply voltage compensation circuit according to claim 1, characterized in that, The second reference voltage is obtained according to the following formula: VREF_1 = VREF_0 + K2 × Vcs Wherein, VREF_1 is the second reference voltage, VREF_0 is the first reference voltage, Vcs is the second sampling voltage, and K2 is a preset parameter greater than 0.

4. The switching power supply voltage compensation circuit according to any one of claims 1 to 3, characterized in that, The first sampling circuit includes a first resistor and a second resistor. One end of the first resistor is connected to the output side of the switching power supply, the other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor is grounded, and the second input terminal is connected between the first resistor and the second resistor.

5. The switching power supply voltage compensation circuit according to any one of claims 1 to 3, characterized in that, The second sampling circuit includes a third resistor connected between the output side of the switching power supply and the load.

6. The switching power supply voltage compensation circuit according to claim 5, characterized in that, The second sampling circuit also includes an analog-to-digital converter connected between the voltage sampling port and the third resistor.

7. The switching power supply voltage compensation circuit according to any one of claims 1 to 3, characterized in that, It also includes a digital-to-analog converter connected between the reference voltage output port and the first input terminal.

8. The switching power supply voltage compensation circuit according to any one of claims 1 to 3, characterized in that, The voltage compensation module includes: An optocoupler is connected to the output terminal of the operational amplifier and the output side of the switching power supply. A pulse width modulation chip is connected to the optocoupler; The switching unit is connected to the pulse width modulation chip and the input side of the switching power supply.

9. A switching power supply, characterized in that, include: A power supply circuit, including a mutually coupled input side and an output side; In the voltage compensation circuit according to any one of claims 1 to 8, the voltage compensation module is connected to the input side, and the operational amplifier and the controller are both connected to the output side.

10. The switching power supply according to claim 9, characterized in that: When the voltage compensation module outputs a negative compensation signal, the output voltage on the output side when the load is unloaded is greater than the output voltage when the load is fully loaded. When the voltage compensation module outputs a positive compensation signal, the output voltage on the output side when the load is unloaded is less than the output voltage when the load is fully loaded.

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