Control method, control device and switching power supply

Abstract

The invention discloses a control method, a control device and a switching power supply. The control method comprises the following steps: generating a sine full-wave rectification signal with a fixed amplitude; acquiring an input voltage sampling signal representing an input voltage peak value or an effective value of the power factor corrector; acquiring an output voltage loop feedback signal representing the magnitude of the output voltage of the power factor corrector; the sine full-wave rectification signal with the fixed amplitude serves as a first signal, or the sine full-wave rectification signal with the fixed amplitude is divided by the input voltage sampling signal to serve as the first signal; multiplying the first coefficient by the first signal, multiplying the second coefficient by the output voltage loop feedback signal, and adding the products to obtain a second signal; multiplying the third coefficient by the output voltage loop feedback signal, and dividing the obtained product by the input voltage sampling signal to obtain a third signal; a frequency conversion control signal is generated according to the second and third signals. According to the invention, frequency conversion control in a PFC CCM mode and high-efficiency operation under various working conditions can be realized.

Description

Technical Field

[0001] The invention relates to frequency conversion control, and in particular to a control method, a control device and a switching power supply. Background Art

[0002] Traditional CCM (continuous conduction mode) PFC (power factor correction) adopts a fixed frequency control strategy, and its frequency is constant throughout the entire input voltage and output power range. The PFC input current changes sinusoidally within one power frequency cycle, and the input current is large when the load is heavy and small when the load is light. This control strategy will cause two problems: one is that when the load is light, the frequency of the PFC circuit is the same as when the load is heavy, which will cause the PFC circuit to lose more when the load is light; the other is that when the input voltage is close to zero, the current is small and the input voltage is also small. If the frequency is too high, the power consumption of the PFC circuit will increase. Summary of the invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a control method, a control device and a switching power supply, which at least solve one of the technical problems existing in the prior art to a certain extent.

[0004] As a first aspect of the present invention, the technical solution of the control method provided is as follows: A control method is applied to a power factor corrector, comprising: A reference signal generating step, generating a sinusoidal full-wave rectified signal with a fixed amplitude; An input voltage detection step, obtaining an input voltage sampling signal representing a peak value or an effective value of an input voltage of the power factor corrector; An output voltage feedback step, obtaining an output voltage loop feedback signal representing the output voltage of the power factor corrector; A first signal acquisition step, taking the fixed amplitude full-wave rectified sine signal as the first signal, or dividing the fixed amplitude full-wave rectified sine signal by the input voltage sampling signal as the first signal; a second signal acquisition step, multiplying the first signal by a first coefficient, multiplying the output voltage loop feedback signal by a second coefficient, and then adding the products of the two to obtain the second signal; a third signal acquisition step, multiplying the third coefficient by the output voltage loop feedback signal, and dividing the obtained product by the input voltage sampling signal to obtain the third signal; A frequency conversion function signal generating step, generating a frequency conversion control signal according to the second signal and the third signal, and then generating a clock signal of a corresponding frequency according to the frequency conversion control signal, wherein the clock signal is used to control the operating frequency of the main power switch tube in the power factor corrector; Wherein: when the second signal>the third signal, the third signal is used as the frequency conversion control signal; when the second signal≤the third signal, the second signal is used as the frequency conversion control signal.

[0005] Furthermore, the fixed-amplitude sinusoidal full-wave rectified signal has the same frequency and phase as the input voltage sampling signal.

[0006] Furthermore, the fixed amplitude sinusoidal full-wave rectified signal is obtained by one of the following means: Obtained by dividing the full-wave rectified signal of the instantaneous input voltage of the power factor corrector by the input voltage peak sampling signal of the power factor corrector; Obtained by dividing the full-wave rectified signal of the input instantaneous voltage of the power factor corrector by the input voltage effective value sampling signal of the power factor corrector; It is generated by a fixed amplitude sinusoidal full-wave rectified signal generating circuit and then phase-locked with the full-wave rectified signal of the input instantaneous voltage of the power factor corrector to obtain it.

[0007] Furthermore, the second coefficient is set to 0.

[0008] Furthermore, the minimum frequency of the clock signal is greater than 20 KHz.

[0009] As a second aspect of the present invention, the technical solution of the embodiment of the control device provided is as follows: A control device, applied to a power factor corrector, comprising: A reference signal generating module, used for generating a sinusoidal full-wave rectified signal with a fixed amplitude; An input voltage detection module, used to obtain an input voltage sampling signal representing a peak value or an effective value of an input voltage of the power factor corrector; An output voltage feedback module, used to obtain an output voltage loop feedback signal representing the output voltage of the power factor corrector; A first signal acquisition module, used to take the fixed-amplitude sinusoidal full-wave rectified signal as the first signal, or to divide the fixed-amplitude sinusoidal full-wave rectified signal by the input voltage sampling signal as the first signal; a second signal acquisition module, configured to multiply the first signal by a first coefficient, multiply the output voltage loop feedback signal by a second coefficient, and then add the products of the two to obtain the second signal; A third signal acquisition module, used for multiplying the output voltage loop feedback signal by a third coefficient, and dividing the obtained product by the input voltage sampling signal to obtain the third signal; A variable frequency function signal generating module, used to generate a variable frequency control signal according to the second signal and the third signal, and then generate a clock signal of a corresponding frequency according to the variable frequency control signal, wherein the clock signal is used to control the operating frequency of the main power switch tube in the power factor corrector; Wherein: when the second signal>the third signal, the third signal is used as the frequency conversion control signal; when the second signal≤the third signal, the second signal is used as the frequency conversion control signal.

[0010] As a third aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows: A switching power supply includes a power factor corrector, wherein: it also includes the control device described in any one of the second aspects above.

[0011] The control method, device and switching power supply of the embodiment of the present invention first obtain a first signal through the input voltage of the power factor corrector, and then obtain a second signal and a third signal through the output voltage of the power factor corrector using different algorithms, and then generate a corresponding variable frequency control signal, that is, by constructing a curve that changes with the input voltage and load, the operating frequency of the PFC is controlled to achieve multi-mode operation within one power frequency cycle. The detailed working principle will be analyzed in conjunction with the specific implementation method. The beneficial effects of the present invention compared with the prior art are as follows: (1) The control method, device and switching power supply of the embodiments of the present invention can make the switching frequency of the CCM mode PFC increase with the increase of input current or load within a power frequency cycle range, and operate at a higher operating frequency when the input voltage is at a peak or overload; (2) The control method, device and switching power supply of the embodiment of the present invention operate at a lower frequency under light load and near zero input voltage, thereby improving the THD, efficiency and PF value of the PFC under light load; (3) The control method, device and switching power supply of the embodiments of the present invention can improve the efficiency of the switching power supply under all operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a control block diagram of the existing CCM PFC average current type; Figure 2 This is a schematic diagram of a preferred frequency conversion control strategy of the present invention; Figure 3a Figure 2 A waveform diagram of the first signal V1; Figure 3b for Figure 2 A waveform diagram of the first signal V1; Figure 3c for Figure 2The waveform of the second signal V2 Figure 3d for Figure 2 Medium V fb Relationship diagram with load variation; Figure 3e for Figure 2 Medium V in-sense Waveform diagram when input voltage is higher and lower; Figure 3f for Figure 2 The frequency conversion control signal waveform when K2=0; Figure 3g for Figure 2 The frequency conversion control signal waveform when K2≠0; Figure 4 This is a schematic diagram of another preferred frequency conversion control strategy of the present invention; Figure 5 shows Figure 4 The frequency conversion control signal generates a waveform diagram. DETAILED DESCRIPTION

[0013] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. In the following embodiments, many details are described to enable the present application to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, methods.

[0014] Further, it should be understood that the present disclosure can have various changes in different embodiments, all of which do not depart from the scope of the present disclosure, and the descriptions and drawings therein are essentially intended to illustrate these changes rather than to limit the present disclosure.

[0015] Furthermore, the serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0016] like Figure 1 The figure shows the CCM PFC implemented by the existing average current control, wherein 101 is the average current loop, 102 is the average current loop reference, which is obtained by multiplying the input voltage sampling and the voltage loop output 104, wherein 103 is the output voltage loop reference, and the average current of the inductor is sampled by 105, and feedback integration is performed with the average current loop reference to obtain the average current loop output, and the fixed frequency sawtooth wave is compared with the average current loop output, and connected to the R end of the RS trigger as the switch-off trigger signal of the switch tube, and 106 is a fixed frequency clock signal, which is connected to the S end of the RS trigger as the switch-on trigger signal of the switch tube to realize the control of the CCM PFC.

[0017] The frequency of this control is constant within the entire input voltage and output power range, while the PFC input current changes sinusoidally within a power frequency cycle, and the input current is large when the load is heavy and small when the load is light. This control strategy will lead to two problems. One is that when the load is light, the frequency of the PFC circuit is the same as when it is heavy, which will cause the PFC circuit to lose more when the load is light. In addition, when the input voltage is close to zero, the current is small and the input voltage is also small. If the frequency is too high, the power consumption of the PFC circuit will increase.

[0018] In view of the above reasons, Figure 2 A better variable frequency control strategy is proposed, see Figure 2 , wherein: 205 is a sinusoidal full-wave rectified signal of fixed amplitude, which can be obtained by dividing the input instantaneous voltage signal of the power factor corrector by the input voltage peak sampling signal, or by dividing the input instantaneous voltage signal of the power factor corrector by the input voltage effective value sampling signal, or by being generated by a sinusoidal full-wave rectified signal generating circuit, and then being phase-locked with the full-wave rectified signal of the input instantaneous voltage of the power factor corrector, and is characterized in that it has the same frequency and phase as the full-wave rectified input voltage signal; 204 is the peak sampling signal of the input voltage or the effective value sampling signal of the input voltage V in-sense ; Divide 205 by 204 to obtain 201, i.e., the first signal V1; since 205 is a sinusoidal full-wave rectified signal with a fixed amplitude, the amplitude of V1 decreases as the input voltage increases; 207 is the output V of the PFC voltage loop fb , set coefficients K1 and K2, add the product of K1 and V1 to V fb The product of K2 is taken as the second signal V2; set coefficient K3, multiply K3 by V fb Divide by V in-sense The result is 203, which is the third signal V3. V3 is smaller at high voltage or light load, and larger at low voltage or heavy load. Finally, the second signal V2 and the third signal V3 are input into the variable frequency function signal generating module. When the second signal V2> the third signal V3, the variable frequency function signal generating module outputs the third signal V3 as the variable frequency control signal. When the second signal V2≤the third signal V3, the variable frequency function signal generating module outputs the second signal V2 as the variable frequency control signal. Then, the variable frequency clock generating module generates a clock signal of corresponding frequency according to the frequency control signal and the amplitude change of the frequency control signal.

[0019] Figure 3 Figure 2 The key waveforms in the process, such as Figure 3a As shown: 301 is a sinusoidal full-wave rectified signal with a fixed amplitude; Figure 3b It means 301 divided by the input voltage peak sampling signal or effective value signal V in-senseThe first signal V1 is obtained, Figure 3e V in-sense The voltage signal corresponding to the input voltage is higher and lower. Here you can set an input voltage, and the V corresponding to the input voltage peak sampling signal or the effective value signal in-sense Equal to 1, under this input voltage, the 303 signal is the same as the 301 signal. When the input voltage is less than the set input voltage, 302 corresponds to the first signal V1 waveform at this time. When the input voltage is greater than the set input voltage, 304 corresponds to the first signal V1 waveform at this time.

[0020] In addition, set the coefficients K1 and K2, and add the product of K1 and V1 to V fb The product of K2 is used as the second signal V2, where Figure 3d Shows V fb The relationship between load changes and V fb When the load is small, V fb Therefore, there are two situations for the second signal V2.

[0021] When K2=0, the second signal V2 differs from the first signal V1 by only one K1 coefficient, and its waveform is equivalent to Figure 3b Multiply the waveform in by K1; When K2≠0, Figure 3c As shown, the second signal V2 has an offset, which is higher at low voltage or heavy load as shown in 305, and lower at high voltage or light load as shown in 307. 306 is the second signal V2 when K2=0.

[0022] Set coefficient K3, multiply K3 by V fb Divide by V in-sense Get the third signal V3, according to V fb With V in-sense It can be inferred from the waveform that V3 is smaller at high voltage or light load, and larger at low voltage or heavy load. The second signal V2 is compared with the third signal V3, and the third signal V3 is used to limit the second signal V2. When the second signal V2> the third signal V3, the third signal V3 is used as the frequency conversion control signal. When the second signal V2≤the third signal V3, the second signal V2 is used as the frequency conversion control signal. At this time, depending on whether K2 is equal to 0, there are two situations for the frequency conversion control signal.

[0023] When K2=0, the frequency conversion control signal is as follows Figure 3f As shown, 308 is the frequency conversion control signal when the input voltage is low or the load is heavy, and 309 is the frequency conversion control signal when the input voltage is high or the load is light.

[0024] When K2≠0, the frequency conversion control signal is as follows Figure 3gAs shown, 310 is the frequency conversion control signal when the input is low voltage or heavy load, and 311 is the frequency conversion control signal when the input is high voltage or light load.

[0025] Finally, the controller generates a corresponding frequency clock signal according to the variable frequency control signal. It should be noted here that the lowest operating frequency is generally set above 20KHz. Therefore, this control strategy realizes that within one power frequency cycle, the operating frequency of the CCM mode PFC circuit is high in the middle and low on both sides. At the same time, the circuit operating frequency is high when overloaded, and low when lightly loaded.

[0026] besides, Figure 4 Another better variable frequency control strategy is proposed, see Figure 4 , wherein: 401 is a sinusoidal full-wave rectified signal with a fixed amplitude, which can be obtained by dividing the input instantaneous voltage signal of the power factor corrector by the input voltage peak sampling signal, or by dividing the input instantaneous voltage signal of the power factor corrector by the input voltage effective value sampling signal, or by being generated by a sinusoidal full-wave rectified signal generating circuit, and then being phase-locked with the full-wave rectified signal of the input instantaneous voltage of the power factor corrector, and is characterized in that it has the same frequency and phase as the signal after full-wave rectification of the input voltage; 401 is directly used as the first signal V1, and 405 is the output V of the PFC voltage loop fb , set coefficients K1 and K2, add the product of K1 and V1 to V fb The product of K2 is 402, which is the second signal V2. Set the coefficient K3 and multiply K3 by V fb The result is 403, which is the third signal V3. V3 is smaller at high voltage or light load, and larger at low voltage or heavy load. Finally, the second signal V2 and the third signal V3 are input into the variable frequency function signal generating module: when the second signal V2>the third signal V3, the variable frequency function signal generating module outputs the third signal V3 as the variable frequency control signal. When the second signal V2≤the third signal V3, the variable frequency function signal generating module outputs the second signal V2 as the variable frequency control signal. Then, the variable frequency clock generating module generates a clock signal of corresponding frequency according to the amplitude change of the variable frequency control signal 404.

[0027] Figure 5 Figure 4 The key waveforms in the process, such as Figure 5a As shown, 501 is a sinusoidal full-wave rectified signal with a fixed amplitude. Here, 501 is directly used as the first signal V1. Figure 5d Shows V fb With the relationship between load, when the load is heavy, V fb When the load is small, V fb Small. Figure 5e shows the V under the same load fbWith the input voltage, when the input voltage is low, V fb When the input voltage is small, V fb Small. Also set coefficients K1 and K2, add the product of K1 and V1 to V fb The product of K2 is used as the second signal V2.

[0028] Therefore, there are two situations for the second signal V2.

[0029] When K2=0, Figure 5b As shown, the second signal V2 is different from the first signal V1 by only one K1 coefficient, and its waveform is equivalent to Figure 5a Multiply the waveform in by K1. When K1=1, it corresponds to 503; when K1>1, it corresponds to 502; when K1<1, it corresponds to 503.

[0030] When K2≠0, Figure 5c As shown, the second signal V2 has an offset, which is higher at low voltage or heavy load as shown by 505, and lower at high voltage or light load as shown by 507. 506 is the second signal V2 when K2=0.

[0031] Set coefficient K3, multiply K3 by V fb Get the third signal V3, according to V fb With V in-sense It can be inferred from the waveform that V3 is smaller at high voltage or light load, and larger at low voltage or heavy load. The second signal V2 is compared with the third signal V3, and the third signal V3 is used to limit the second signal V2. When the second signal V2> the third signal V3, the third signal V3 is used as the frequency conversion control signal. When the second signal V2≤the third signal V3, the second signal V2 is used as the frequency conversion control signal. At this time, depending on whether K2 is equal to 0, there are two situations for the frequency conversion control signal.

[0032] When K2=0, the frequency conversion control signal is as follows Figure 5f As shown, 508 is the frequency conversion control signal when the input voltage is low or heavy load, and 509 is the frequency conversion control signal when the input voltage is high or light load.

[0033] When K2≠0, the frequency conversion control signal is as follows Figure 5g As shown, 510 is the frequency conversion control signal when the input is low voltage or heavy load, and 511 is the frequency conversion control signal when the input is high voltage or light load.

[0034] Finally, the controller generates a corresponding frequency clock signal according to the variable frequency control signal. It should be noted here that the lowest operating frequency is generally set above 20KHz. Therefore, this control strategy realizes that within one power frequency cycle, the operating frequency of the CCM mode PFC circuit is high in the middle and low on both sides. At the same time, the circuit operating frequency is high when overloaded, and low when lightly loaded.

[0035] Based on a variable frequency control method, a control device and a switching power supply provided by the present invention, it is possible to realize CCM PFC operating at different frequencies within one power frequency cycle, and to change its operating frequency accordingly according to changes in input voltage and output load, which can greatly improve the working efficiency of the circuit.

[0036] Although the present invention has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present invention can be embodied in a variety of forms without departing from the spirit or nature of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A control method, applied to a power factor corrector, characterized in that: include: A reference signal generating step, generating a sinusoidal full-wave rectified signal with a fixed amplitude; An input voltage detection step, obtaining an input voltage sampling signal representing a peak value or an effective value of an input voltage of the power factor corrector; An output voltage feedback step, obtaining an output voltage loop feedback signal representing the output voltage of the power factor corrector; A first signal acquisition step, taking the fixed amplitude full-wave rectified sine signal as the first signal, or dividing the fixed amplitude full-wave rectified sine signal by the input voltage sampling signal as the first signal; a second signal acquisition step, multiplying the first signal by a first coefficient, multiplying the output voltage loop feedback signal by a second coefficient, and then adding the products of the two to obtain the second signal; a third signal acquisition step, multiplying the third coefficient by the output voltage loop feedback signal, and dividing the obtained product by the input voltage sampling signal to obtain the third signal; A frequency conversion function signal generating step, generating a frequency conversion control signal according to the second signal and the third signal, and then generating a clock signal of a corresponding frequency according to the frequency conversion control signal, wherein the clock signal is used to control the operating frequency of the main power switch tube in the power factor corrector; Wherein: when the second signal>the third signal, the third signal is used as the frequency conversion control signal; when the second signal≤the third signal, the second signal is used as the frequency conversion control signal.

2. The control method according to claim 1, characterized in that: The fixed-amplitude sinusoidal full-wave rectified signal has the same frequency and phase as the input voltage sampling signal.

3. The control method according to claim 1, characterized in that: The fixed amplitude full-wave rectified sine signal is obtained by one of the following means: Obtained by dividing the full-wave rectified signal of the instantaneous input voltage of the power factor corrector by the input voltage peak sampling signal of the power factor corrector; Obtained by dividing the full-wave rectified signal of the input instantaneous voltage of the power factor corrector by the input voltage effective value sampling signal of the power factor corrector; It is generated by a fixed amplitude sinusoidal full-wave rectified signal generating circuit and then phase-locked with the full-wave rectified signal of the input instantaneous voltage of the power factor corrector to obtain it.

4. The control method according to claim 1, characterized in that: The second coefficient is set to zero.

5. The control method according to claim 1, characterized in that: The minimum frequency of the clock signal is greater than 20 KHz.

6. A control device, applied to a power factor corrector, characterized in that: include: A reference signal generating module, used for generating a sinusoidal full-wave rectified signal with a fixed amplitude; An input voltage detection module, used to obtain an input voltage sampling signal representing a peak value or an effective value of an input voltage of the power factor corrector; An output voltage feedback module, used to obtain an output voltage loop feedback signal representing the output voltage of the power factor corrector; A first signal acquisition module, used to take the fixed-amplitude sinusoidal full-wave rectified signal as the first signal, or to divide the fixed-amplitude sinusoidal full-wave rectified signal by the input voltage sampling signal as the first signal; a second signal acquisition module, configured to multiply the first signal by a first coefficient, multiply the output voltage loop feedback signal by a second coefficient, and then add the products of the two to obtain the second signal; A third signal acquisition module, used for multiplying the output voltage loop feedback signal by a third coefficient, and dividing the obtained product by the input voltage sampling signal to obtain the third signal; A variable frequency function signal generating module, used to generate a variable frequency control signal according to the second signal and the third signal, and then generate a clock signal of a corresponding frequency according to the variable frequency control signal, wherein the clock signal is used to control the operating frequency of the main power switch tube in the power factor corrector; Wherein: when the second signal>the third signal, the third signal is used as the frequency conversion control signal; when the second signal≤the third signal, the second signal is used as the frequency conversion control signal.

7. A switching power supply, comprising a power factor corrector, characterized in that: Also includes the control device as claimed in claim 6.

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