CN108809098B

CN108809098B - Power converter with synchronous rectifier and voltage regulation method thereof

Info

Publication number: CN108809098B
Application number: CN201710310920.7A
Authority: CN
Inventors: 叶小培; 鍾业武
Original assignee: Sync Power Corp
Current assignee: Sync Power Corp
Priority date: 2017-05-05
Filing date: 2017-05-05
Publication date: 2020-08-04
Anticipated expiration: 2037-05-05
Also published as: CN108809098A

Abstract

The invention provides a power converter with a synchronous rectifier and a voltage regulating method thereof. The power converter includes a secondary side circuit and a primary side circuit. The secondary side circuit includes a coil and a synchronous rectifier coupled to the coil, the synchronous rectifier having a voltage thereon. The primary side circuit includes a primary side conditioning controller and an additional coil. The additional coil induces the coil in a plurality of cycles to provide a primary side regulated controller feedback voltage. The feedback voltage is related to the voltage on the synchronous rectifier, and the plurality of periods at least comprise a first period, a second period and a third period. When the primary side regulating controller detects that the feedback voltage has step change in a specific period of the second period, the primary side regulating controller regulates the feedback voltage in the second period or the third period. This can prevent the output voltage from being improperly adjusted due to the switching of the state of the synchronous rectifier.

Description

Power converter with synchronous rectifier and voltage regulation method thereof

Technical Field

The present invention relates to a power converter and a voltage regulation method thereof, and more particularly, to a power converter having a Synchronous Rectifier (SR) and a voltage regulation method thereof.

Background

Fig. 1 is a schematic diagram of a conventional power converter 100. In the power converter 100, since the output voltage Vo may be reflected to the coil 130 via the secondary side coil 122 in the transformer 120, there is no need to provide an optocoupler feedback circuit as in known secondary side regulation circuit topologies.

However, since the output voltage Vo is first passed through the diode DD (used as a rectifying device) and then appears on the secondary winding 122 of the transformer 120, the voltage seen by the secondary winding 122 will be the sum of the output voltage Vo and the voltage (about-0.7V) across the diode DD, rather than the desired output voltage Vo. For example, assuming that the output voltage Vo is 5V, the voltage seen by the secondary side coil 122 is, for example, 5.7V.

Since the Primary Side Regulation (PSR) controller 110 regulates the output voltage Vo of the power converter 100 based on the voltage reflected by the secondary side coil 122 to the coil 130, the use of the diode DD as a rectifying device will make the voltage across the secondary side coil 122 less accurate, and thus affect the regulation of the output voltage Vo.

In addition, there is a technical means of using SR instead of diode DD as a rectifying device to save power consumption in the prior art. However, in this case, since the SR is switched in two states under the control of the SR controller, the uncertainty of the voltage on the secondary side coil 122 will be increased, thereby more significantly affecting the regulation situation of the output voltage Vo.

Disclosure of Invention

Accordingly, the present invention provides a power converter having SR and PSR controllers and a voltage regulation method thereof, which can adaptively regulate and compensate a feedback voltage according to whether a step change occurs in the feedback voltage detected by a primary side circuit, thereby preventing the PSR controller from improperly regulating an output voltage.

The invention provides a power converter with a synchronous rectifier and a primary side regulation controller. The secondary side circuit comprises a coil and a synchronous rectifier coupled with the coil, and a voltage is applied to the synchronous rectifier. The primary side circuit includes a primary side conditioning controller and an additional coil. The additional coil is coupled to the coil of the secondary side circuit and induces the coil of the secondary side circuit in a plurality of cycles to provide a feedback voltage to the primary side regulator controller. The feedback voltage is related to the voltage on the synchronous rectifier, and the plurality of periods at least comprise a first period, a second period and a third period. The primary side regulator controller determines whether a step change in the feedback voltage is detected during a specific period of a second cycle. When the primary side regulating controller detects that the feedback voltage has step change in a specific period of the second period, the primary side regulating controller regulates the feedback voltage in the second period or a third period.

In an embodiment of the present invention, when the synchronous rectifier is turned on, the synchronous rectifier operates in an on state, and when the synchronous rectifier is turned off, the synchronous rectifier operates in a diode state.

In one embodiment of the present invention, the step change is in the form of a step increment, and the switching of the synchronous rectifier from the conducting state to the diode state causes the feedback voltage to undergo a step change.

In an embodiment of the invention, the step change is in the form of a step decrement, and the switching of the synchronous rectifier from the diode state to the conducting state causes the feedback voltage to have a step change.

In an embodiment of the invention, when the primary side adjustment controller detects the step change of the feedback voltage in the specific period of the second period, the primary side adjustment controller adjusts an oscillation condition of the feedback voltage in the second period according to a voltage value of the feedback voltage in the specific period of the first period or the specific period of the second period.

In an embodiment of the invention, the first period and the second period each include a first period, a second period and a third period, which are consecutive, and the second period of the first period is a specific period of the first period and the second period of the second period is a specific period of the second period. The primary side regulating controller regulates the oscillation of the feedback voltage in a third period of the second period according to the voltage value of the feedback voltage in the second period of the first period.

In an embodiment of the invention, a time length difference between the third period of the first period and the third period of the second period is smaller than a predetermined threshold.

In an embodiment of the present invention, the first period is charging, the second period is discharging, and the third period is off.

In one embodiment of the present invention, the second period is after the first period.

In an embodiment of the invention, the second period is a next period of the first period.

In an embodiment of the invention, the second period is separated from the first period by a predetermined number of periods.

In an embodiment of the present invention, the first period and the second period are respectively characterized as a (j) th period and a (j + N) th period, where j is a positive integer and N is a predetermined number. The step change is a change value between a first voltage average value and a second voltage average value, wherein the first voltage average value is an average value of the feedback voltage in the (j-N +1) th period to the (j) th period, and the second voltage average value is an average value of the feedback voltage in the (j +1) th period to the (j + N) th period.

In an embodiment of the present invention, the step change is a change value between the feedback voltage in the specific period of the second period and the feedback voltage in the specific period of the first period.

In an embodiment of the invention, the power converter further includes a step-up regulator, configured to regulate an oscillation condition of the feedback voltage in the fourth period according to a voltage value of the feedback voltage in a specific period of the fourth period when the primary-side regulator controller detects that the feedback voltage returns to the voltage value before the step-up change occurs in the specific period of the fourth period.

In an embodiment of the invention, the primary side adjustment controller includes a first input terminal, a second input terminal, a third input terminal, an output terminal, and a ground pin, and the primary side circuit further includes a power supply, a first resistor, a capacitor, a first coil, a switch, a second resistor, a diode, a third resistor, and a fourth resistor. The power supply has a first terminal and a second terminal connected to a ground terminal. A first terminal of the first resistor is coupled to the first terminal of the power supply. A first end of the capacitor is coupled to a second end of the first resistor, and a second end of the capacitor is coupled to the ground terminal. A first end of the first coil is coupled to a first end of the power supply. A first terminal of the switch is coupled to a second terminal of the first coil, and a control terminal of the switch is coupled to the output terminal of the primary-side adjustment controller. A first terminal of the second resistor is coupled to a second terminal of the switch and the second input terminal of the primary-side adjustment controller, and a second terminal of the second resistor is coupled to the ground terminal. A cathode of the diode is coupled to the first end of the capacitor and the first input end of the primary side adjustment controller, and an anode of the diode is coupled to a first end of the additional coil. A first terminal of the third resistor is coupled to the anode of the diode, and a second terminal of the third resistor is coupled to the third input terminal of the primary-side adjustment controller. A first terminal of the fourth resistor is coupled to the second terminal of the third resistor, and a second terminal of the fourth resistor is coupled to the ground terminal, a second terminal of the additional coil, and the ground pin of the primary-side adjustment controller.

In an embodiment of the invention, the coil of the secondary side circuit includes a first terminal and a second terminal, the synchronous rectifier includes a first terminal, a second terminal and a control terminal, and the secondary side circuit further includes a synchronous rectifier controller, a capacitor and a load. The synchronous rectifier controller has a first input terminal, a second input terminal, an output terminal and a ground pin. The first input end is coupled with the first end of the coil of the secondary side circuit, the second input end of the synchronous rectifier controller is coupled with the second end of the coil of the secondary side circuit and the first end of the synchronous rectifier, and the output end of the synchronous rectifier controller is coupled with the control end of the synchronous rectifier. A first terminal of the capacitor is coupled to the first terminal of the coil of the secondary side circuit, and a second terminal of the capacitor is coupled to a ground terminal, the second terminal of the synchronous rectifier and the ground pin of the synchronous rectifier controller. A first terminal of the load is coupled to the first terminal of the coil of the secondary side circuit, and a second terminal of the load is coupled to the ground terminal.

The present invention further provides a voltage regulation method suitable for a power converter including a primary side circuit and a secondary side circuit. The primary side circuit comprises a primary side regulation controller and an additional coil, the secondary side circuit comprises a coil and a synchronous rectifier, and the additional coil is coupled with the coil of the secondary side circuit. The method comprises the following steps: inducing, by the additional coil, the coil of the secondary side circuit for a first period to provide a feedback voltage to the primary side regulation controller, wherein the feedback voltage is related to a voltage on the synchronous rectifier; the primary side adjusting controller judges whether a step change of the feedback voltage is detected in a specific period of a second period; and when the primary side regulation controller detects that the feedback voltage has step change in a specific period of the second period, regulating the feedback voltage in the second period or a third period by the primary side regulation controller.

In an embodiment of the present invention, the step of adjusting the feedback voltage in the second period or the third period by the primary side adjustment controller comprises: and adjusting an oscillation condition of the feedback voltage in the second period by the primary side adjustment controller according to a voltage value of the feedback voltage in a specific period of the first period or a specific period of the second period.

In an embodiment of the invention, the first period and the second period each include a first period, a second period and a third period, which are consecutive, and the second period of the first period is a specific period of the first period and the second period of the second period is a specific period of the second period. The step of the primary side regulation controller regulating the feedback voltage in the second period or the third period comprises: the oscillation of the feedback voltage in the third period of the second period is regulated by the primary side regulation controller in dependence on the voltage value of the feedback voltage in the second period of the first period.

In an embodiment of the present invention, the method further includes: when the primary side adjusting controller detects that the feedback voltage returns to a voltage value before the step change occurs in a fourth period, the primary side adjusting controller adjusts an oscillation condition of the feedback voltage in the fourth period according to the voltage value.

Drawings

FIG. 1 is a schematic diagram of a known power converter;

FIG. 2 is a schematic diagram of a power converter with SR and PSR controllers according to an embodiment of the invention;

FIG. 3A is a waveform diagram illustrating when the SR is switched from a conduction state to a diode state according to the embodiment of the invention shown in FIG. 2;

FIG. 3B is a waveform diagram illustrating the SR switched from the diode state to the conduction state according to the embodiment of the invention in FIG. 2;

FIG. 4 is a flow chart of a voltage regulation method according to an embodiment of the invention;

FIG. 5A is a waveform diagram illustrating when the SR is switched from a conduction state to a diode state according to the embodiment shown in FIG. 3A and FIG. 4;

FIG. 5B is a waveform diagram illustrating when the SR is switched from the diode state to the conduction state according to the embodiment shown in FIG. 3B and FIG. 4;

FIG. 6A is a schematic diagram illustrating the use of adjacent detection without adjusting the feedback voltage and de-adjusting according to the embodiment of FIG. 2;

FIG. 6B is a schematic diagram of the embodiment of FIG. 6A showing the use of adjacent detection means and the regulation of the feedback voltage and the de-regulation;

FIG. 7A is a schematic diagram illustrating the embodiment of FIG. 2 using skip detection without adjusting the feedback voltage and without de-adjusting;

FIG. 7B is a schematic diagram of the embodiment of FIG. 7A using a skip detection approach and adjusting the feedback voltage and de-adjusting;

FIG. 8A is a schematic diagram illustrating the embodiment of FIG. 7A using skip average detection without adjusting the feedback voltage and without de-adjusting;

FIG. 8B is a schematic diagram illustrating the embodiment of FIG. 8A using skip-average detection and adjusting the feedback voltage and de-adjusting;

FIG. 9 is a waveform simulation of unregulated feedback voltage and unregulated output voltage and feedback voltage, according to one embodiment of the present invention;

FIG. 10 is a waveform simulation of the regulated and unregulated output and feedback voltages according to step changes according to one embodiment of the present invention;

FIG. 11 is a diagram illustrating the embodiment of FIG. 9 using the skip-average detection method.

Detailed Description

Various embodiments of the present invention will be described below with reference to the accompanying drawings. For the purpose of clarity, numerous implementation details are set forth in the following description. However, these implementation details should not be used to limit the invention. That is, in some embodiments of the invention, these implementation details are not necessary. In addition, for the sake of simplicity, some conventional structures and elements are shown in the drawings in a simple schematic manner; and repeated elements will likely be referred to using the same reference numerals.

Fig. 2 is a schematic diagram of a power converter 200 having an SR224 and a PSR controller 212 according to an embodiment of the invention. The power converter 200 includes a secondary side circuit 220 and a primary side circuit 210. The secondary side circuit 220 includes a coil 222 and an SR224 coupled to the coil 222, wherein the SR224 has a voltage vds. The primary side circuit 210 includes a PSR controller 212 and an additional coil 218. The additional coil 218 may induce the coil 222 over multiple cycles to provide a feedback voltage Va to the PSR controller 212. Feedback voltage Va is the voltage vds associated with SR 224.

As shown in fig. 2, the PSR controller 212 includes a first input vcc, a second input vcs, a third input vfb, an output gt, and a ground pin gnd, and the primary-side circuit 210 may further include a power source PW, a first resistor R1, a capacitor C1, a first coil 214, a switch 216, a second resistor R2, a diode D1, a third resistor Rf1, and a fourth resistor Rf 2. The power source PW has a first end and a second end connected to a ground GND. A first terminal of the first resistor R1 is coupled to the first terminal of the power PW. A first terminal of the capacitor C1 is coupled to a second terminal of the first resistor R1, and a second terminal of the capacitor C1 is coupled to the ground GND. A first terminal of the first coil 214 is coupled to the first terminal of the power PW. A voltage Vp is applied to the first coil 214 and a current Ip flows therethrough.

A first terminal of the switch 216 is coupled to a second terminal of the first coil 214, and a control terminal of the switch 216 is coupled to the output terminal gt of the PSR controller 212. A first terminal of the second resistor R2 is coupled to a second terminal of the switch 216 and the second input vcc of the PSR controller 212, and a second terminal of the second resistor R2 is coupled to the ground GND. A cathode of the diode D1 is coupled to the first terminal of the capacitor C1 and the first input vcc of the PSR controller 212, and an anode of the diode D1 is coupled to a first terminal of the additional coil 218. A first terminal of the third resistor Rf1 is coupled to the anode of the diode D1, and a second terminal of the third resistor Rf1 is coupled to the third input terminal vfb of the PSR controller 212. A first end of the fourth resistor Rf2 is coupled to the second end of the third resistor Rf1, and a second end of the fourth resistor Rf2 is coupled to the ground GND, a second end of the extra coil 218, and the ground pin GND of the PSR controller 212.

In addition, the coil 222 (across which the voltage Vs flows and the current Is) in fig. 2 includes a first terminal and a second terminal, the SR224 includes a first terminal, a second terminal and a control terminal, and the secondary side circuit 220 further includes an SR controller 226, a capacitor CO and a load R L, the SR controller 226 has a first input terminal vdd, a second input terminal sync, an output terminal gt ', and a ground pin GND', the first input terminal vdd Is coupled to the first terminal of the coil 222, the second input terminal sync of the SR controller 226 Is coupled to the second terminal of the coil 222 and the first terminal of the SR224, the output terminal gt 'of the SR controller 226 Is coupled to the control terminal of the SR224, a first terminal of the capacitor CO Is coupled to the first terminal of the coil 222, a second terminal of the capacitor CO Is coupled to the ground terminal GND, the second terminal of the SR224, and the ground pin GND' of the SR controller 226, a first terminal of the load R L Is coupled to the first terminal of the coil 222, and a second terminal of the load R L Is coupled to the ground terminal GND.

As mentioned previously, the SR224 and the SR controller 226 may be introduced into the secondary side circuit 220 to replace the diode DD in fig. 1, thereby reducing the power consumption of the power converter 200. In the present embodiment, the SR224 can be switched between two states by the SR controller 226. Specifically, when the SR224 is turned on by the SR controller 226, the SR224 can operate in a conducting state, i.e., the voltage vds is 0V. On the other hand, when the SR224 is turned off by the SR controller 226, the SR224 can operate in a diode state. That is, the SR224 may be turned off to operate as the diode 224_1 (e.g., the body diode of the SR 224), and the current voltage vds is about-0.7V.

When SR224 is switched from an on-state to a diode-state, or vice versa, the voltage Vs seen by coil 222 will change accordingly, since the voltage vds will change (e.g., from 0V to-0.7V, or from-0.7V to 0V). In this case, the voltage Vs may not accurately correspond to the output voltage Vo. Since the extra coil 218 will induce the voltage Vs to generate the feedback voltage Va for the PSR controller 212 to perform the subsequent voltage adjusting operation, if the voltage Vs does not exactly correspond to the output voltage Vo, the subsequent voltage adjusting operation performed by the PSR controller 212 will be not facilitated.

Fig. 3A is a waveform diagram illustrating when the SR224 is switched from a conducting state to a diode state according to the embodiment of the invention shown in fig. 2. In fig. 3A, the first cycle CY1 and the second cycle CY2 each include a first period Tonp, a second period Tons, and a third period Toff, which are consecutive, and respectively correspond to the charging, discharging, and turning off of the power converter 200. As shown in fig. 3A, the SR224 is turned on during the second period Tons of the first period CY1, and is turned off to be switched to the diode state during the second period Tons of the second period CY 2. Accordingly, the voltage vds is also changed from the voltage value 310 (e.g., 0V) in the second period Tons of the first period CY1 to the voltage value 320 (e.g., -0.7V) in the second period Tons of the second period CY 2. Accordingly, the feedback voltage Va at the additional coil 218 also undergoes a step change in the form of a step increment from the voltage value 330 in the second period Tons of the first period CY1 to the voltage value 340 in the second period Tons of the second period CY2, and the PSR controller 212 performs a subsequent voltage adjustment operation based on the voltage value 340 (e.g., adjusting the oscillation condition 350 of the feedback voltage Va in the third period Toff of the second period CY 2).

It is noted that the output voltage Vo does not change (e.g., 5V shown in fig. 3A) during the first period CY1 and the second period CY2, and therefore the power converter 200 does not substantially need to adjust the value of the output voltage Vo. However, since the PSR controller 212 continues to perform the subsequent voltage regulating operation based on the voltage value 340 from the second period CY2 to the period CYn, the output voltage Vo may be improperly regulated to another voltage value (e.g., 4.3V shown in fig. 3A) during the period CYn.

Referring to fig. 3B, a waveform diagram of the SR224 when being switched from the diode state to the conducting state according to the embodiment of the invention shown in fig. 2 is shown. In fig. 3B, the first cycle CY1 and the second cycle CY2 each include a first period Tonp, a second period Tons, and a third period Toff, which are consecutive, and respectively correspond to the charging, discharging, and turning off of the power converter 200. As shown in fig. 3B, the SR224 is in a diode state during the second period Tons of the first period CY1, and is turned on to be switched to a conductive state during the second period Tons of the second period CY 2. Accordingly, the voltage vds also exhibits a step change in a step decrement form from the voltage value 310 '(e.g., -0.7V) in the second period Tons of the first period CY1 to the voltage value 320' (e.g., 0V) in the second period Tons of the second period CY 2. Accordingly, the feedback voltage Va on the additional coil 218 also changes from the voltage value 330 'in the second period Tons of the first period CY1 to the voltage value 340' in the second period Tons of the second period CY2, and the PSR controller 212 will perform a subsequent voltage adjustment operation based on the voltage value 340 '(e.g., adjust the oscillation condition 350' of the feedback voltage Va in the third period Toff of the second period CY 2).

It is noted that the output voltage Vo is also unchanged (e.g., 5V shown in fig. 3B) during the first period CY1 and the second period CY2, and therefore the power converter 200 does not substantially need to adjust the value of the output voltage Vo. However, since the PSR controller 212 continues to perform the subsequent voltage regulating operation based on the voltage value 340' from the second period CY2 to the period CYn, the output voltage Vo may be improperly regulated to another voltage value (e.g., 5.7V shown in fig. 3B) during the period CYn.

In view of the above, the present invention provides a voltage regulating method, which can prevent the output voltage Vo from being improperly regulated to another voltage value in the above situation.

Fig. 4 is a flowchart illustrating a voltage regulation method according to an embodiment of the invention. The method of the present embodiment can be implemented by the PSR controller 212 in fig. 2, but is not limited thereto. In step S410, the coil 222 may be induced by the additional coil 218 in a first cycle to provide the PSR controller 212 feedback voltage. In step S420, the PSR controller 212 determines whether a step change of the feedback voltage is detected during a specific period of the second period. In an embodiment, the second period may be after the first period (e.g., but may not be limited to, the next period of the first period). In an embodiment, the step change is, for example, a change value between the feedback voltage in the specific period of the second period and the feedback voltage in the specific period of the first period, but the invention is not limited thereto.

Next, in step S430, when the PSR controller 212 detects a step change of the feedback voltage during a specific period of the second period, the PSR controller 212 may adjust the feedback voltage during the second period or the third period.

In one embodiment, when the PSR controller 212 detects a step change in the feedback voltage during a specific period of the second period, the PSR controller 212 may adjust the oscillation of the feedback voltage during the second period according to a voltage value of the feedback voltage during the specific period of the first period or the specific period of the second period. In a further embodiment, when the PSR controller 212 detects a step change in the feedback voltage during a specific period of the second period, the PSR controller 212 may adjust the oscillation of the feedback voltage during the third period of the second period according to the voltage value of the feedback voltage during the second period of the first period.

It should be appreciated that the PSR controller 212 of the present invention can sample and temporarily store the feedback voltage Va during a specific period of each cycle as a basis for subsequent detection and adjustment operations.

Fig. 5A is a waveform diagram illustrating when the SR224 is switched from a conducting state to a diode state according to the embodiment shown in fig. 3A and fig. 4. In this embodiment, the coil 222 may be induced in the first cycle CY1 by the additional coil 218 to provide the PSR controller 212 feedback voltage Va. Next, the PSR controller 212 may determine whether a step change of the feedback voltage Va is detected during a specific period (e.g., the second period Tons) of the second period CY 2.

In fig. 5A, it is assumed that the SR224 is in an on state during the second period Tons of the first period CY1 and is turned off to be switched to a diode state during the second period Tons of the second period CY 2. Accordingly, the voltage vds is also changed from the voltage value 510 (e.g., 0V) in the second period Tons of the first period CY1 to the voltage value 520 (e.g., -0.7V) in the second period Tons of the second period CY 2. Accordingly, the feedback voltage Va on the additional coil 218 is also increased from the voltage value 530 in the second period Tons of the first period CY1 to the voltage value 540 in the second period Tons of the second period CY 2. In other words, the feedback voltage Va exhibits a step change in the form of a step increment (i.e., a change value between the feedback voltage Va in the second period Tons of the second period CY2 and the feedback voltage Va in the second period Tons of the first period CY 1).

It is noted that the output voltage Vo does not change (e.g., 5V shown in fig. 5A) during the first period CY1 and the second period CY2, and therefore the power converter 200 does not substantially need to adjust the value of the output voltage Vo.

To avoid improper adjustment of the output voltage Vo, when the PSR controller 212 detects a step change of the feedback voltage Va during the second period Tons of the second period CY2, the PSR controller 212 may adjust the oscillation condition 550 of the feedback voltage Va during the third period Toff of the second period CY2 according to the voltage value 530 of the feedback voltage Va during the second period Tons of the first period CY 1. In an embodiment, a time length difference between the third period Toff of the first period CY1 (i.e., the oscillation time duration of the oscillation situation 550) and the third period Toff of the second period CY2 may be less than a predetermined threshold (e.g., 100 μ s).

In short, rather than adjusting the oscillation condition 350 based on the voltage value 340 in FIG. 3A, the PSR controller 212 instead adjusts the oscillation condition 550 based on the voltage value 530 in FIG. 5A. As such, when the SR224 is switched to the diode state during the second period Tons of the second period CY2, which results in the step change (i.e., the change between the voltage 540 and the voltage 530), the PSR controller 212 may not adjust the output voltage Vo improperly. In this case, the output voltage Vo may still maintain the same voltage value (e.g., 5V) as the first period CY1 in the period CYn, and may not be adjusted to another voltage value (e.g., 5.7V) as in fig. 3A.

In other embodiments, since the step change occurring on the feedback voltage Va may be due to the switching of the SR224 and other concurrent phenomena, when the PSR controller 212 detects the step change of the feedback voltage Va in the form of step increment in the second period Tons of the second period CY2, the PSR controller 212 may also subtract a preset value (e.g., 0.7V) from the feedback voltage Va in the second period Tons of the second period CY2 to compensate the feedback voltage Va. The PSR controller 212 may then adjust 550 the oscillation of the feedback voltage Va during a third period Toff of the second period CY2 based on the compensated feedback voltage Va. Thus, the PSR controller 212 can still properly regulate the output voltage Vo based on the above phenomenon.

In addition, if the step change is only due to the switching of the SR224, the PSR controller 212 may subtract a preset value from the feedback voltage Va in the second period Tons of the second period CY2 to compensate the feedback voltage Va to a voltage value before the step change occurs (e.g., a value equal to the voltage value 530). The PSR controller 212 may then adjust 550 the oscillation of the feedback voltage Va during a third period Toff of the second period CY2 based on the compensated feedback voltage Va. In this way, improper regulation of the output voltage Vo can also be avoided.

Referring to fig. 5B, a waveform diagram of when the SR224 is switched from the diode state to the conducting state according to the embodiment shown in fig. 3B and fig. 4 is shown. In this embodiment, the coil 222 may be induced in the first cycle CY1 by the additional coil 218 to provide the PSR controller 212 feedback voltage Va. Next, the PSR controller 212 may determine whether a step change of the feedback voltage Va is detected during a specific period (e.g., the second period Tons) of the second period CY 2.

In fig. 5B, it is assumed that the SR224 is in a diode state during the second period Tons of the first period CY1, and is turned on to be switched to a conductive state during the second period Tons of the second period CY 2. Accordingly, the voltage vds is also changed from the voltage value 510 '(e.g., -0.7V) in the second period Tons of the first period CY1 to the voltage value 520' (e.g., 0V) in the second period Tons of the second period CY 2. Accordingly, the feedback voltage Va on the additional coil 218 is also reduced from the voltage value 530 'in the second period Tons of the first period CY1 to the voltage value 540' in the second period Tons of the second period CY 2. In other words, the feedback voltage Va exhibits a step change in the form of a step decrement (i.e., a change value between the feedback voltage Va in the second period Tons of the second period CY2 and the feedback voltage Va in the second period Tons of the first period CY 1).

It is noted that the output voltage Vo does not change (e.g., 5V shown in fig. 5B) during the first period CY1 and the second period CY2, and therefore the power converter 200 does not substantially need to adjust the value of the output voltage Vo.

To avoid improper adjustment of the output voltage Vo, when the PSR controller 212 detects a step change of the feedback voltage Va during the second period Tons of the second period CY2, the PSR controller 212 may adjust an oscillation condition 550 'of the feedback voltage Va during the third period Toff of the second period CY2 according to a voltage value 530' of the feedback voltage Va during the second period Tons of the first period CY 1. In an embodiment, a time length difference between the third period Toff of the first period CY1 (i.e., the oscillation time duration of the oscillation situation 550') and the third period Toff of the second period CY2 may be less than a predetermined threshold (e.g., 100 μ s).

In short, rather than adjusting the oscillation condition 350 'based on the voltage value 340' in FIG. 3B, the PSR controller 212 instead adjusts the oscillation condition 550 'based on the voltage value 530' in FIG. 5B. As such, when the SR224 is switched to the on state during the second period Tons of the second period CY2, which results in the step change (i.e., the change value between the voltage 540 'and the voltage 530'), the PSR controller 212 may not adjust the output voltage Vo inappropriately. In this case, the output voltage Vo may still maintain the same voltage value (e.g., 5V) as the first period CY1 in the period CYn, and may not be adjusted to another voltage value (e.g., 5.7V) as in fig. 3B.

In other embodiments, since the step change occurring on the feedback voltage Va may be due to the switching of the SR224 and other concurrent phenomena, when the PSR controller 212 detects the step change of the feedback voltage Va in the form of step reduction in the second period Tons of the second period CY2, the PSR controller 212 may also superimpose the feedback voltage Va in the second period Tons of the second period CY2 with a predetermined value (e.g., 0.7V) to compensate for the feedback voltage Va. The PSR controller 212 may then adjust the oscillation condition 550' of the feedback voltage Va during the third period Toff of the second period CY2 based on the compensated feedback voltage Va. Thus, the PSR controller 212 can still properly regulate the output voltage Vo based on the above phenomenon.

In addition, if the step change is only due to the switching of the SR224, the PSR controller 212 may superimpose the feedback voltage Va in the second period Tons of the second period CY2 by a preset value to compensate the feedback voltage Va to a voltage value before the step change occurs (e.g., a value equal to the voltage value 530'). The PSR controller 212 may then adjust the oscillation condition 550' of the feedback voltage Va during the third period Toff of the second period CY2 based on the compensated feedback voltage Va. In this way, improper regulation of the output voltage Vo can also be avoided.

Although the above embodiments all take the power converter 200 operating in a pulse-frequency modulation (PFM) mode as an example (i.e., each cycle includes a first period (charging), a second period (discharging), and a third period (turning off)), in other embodiments, the method of the present invention is also applicable to the power converter 200 operating in a pulse-width modulation (PWM) mode (i.e., each cycle includes only the first period (charging) and the second period (discharging)).

When the power converter 200 is operating in the PWM mode, the additional coil 218 may induce the coil 222 during the first period to provide the PSR controller 212 feedback voltage. Then, the PSR controller 212 may determine whether a step change in the feedback voltage is detected during a specific period of the second period. Thereafter, in step S430, when the PSR controller 212 detects a step change of the feedback voltage during a specific period of the second period, the PSR controller 212 may adjust the feedback voltage during the third period. The third period is, for example, any period after the second period, and the specific period is, for example, the second period (discharge), but the present invention is not limited thereto.

In one embodiment, when the PSR controller 212 detects a step change in the second period of the second period, the PSR controller 212 may adjust the time duration of the first period of the third period according to the feedback voltage in the second period of the first period (or may be equivalently regarded as adjusting the feedback voltage in the second period of the third period). The technique of this embodiment also avoids an inappropriate adjustment of the output voltage, as compared to the prior art in which the length of time in the first period of the third period is adjusted based on the feedback voltage in the second period of the second period.

In addition, when the PSR controller 212 detects that the feedback voltage Va returns to the voltage value before the step change occurs during the specific period of the fourth period (not shown), the PSR controller 212 may adjust the oscillation condition of the feedback voltage Va during the fourth period according to the voltage value of the feedback voltage Va during the specific period of the fourth period. That is, when the PSR controller 212 detects that the SR224 has switched to the state before causing the step change, the PSR controller 212 may release the adjustment of the feedback voltage Va.

Taking fig. 5A as an example, when the PSR controller 212 detects that the feedback voltage Va returns to the voltage value before the step change (e.g., the value equal to the voltage value 530) in the fourth period after the second period CY2, the PSR controller 212 may release the adjustment of the feedback voltage Va, i.e., return to the oscillation condition of adjusting the feedback voltage Va of the third period Toff of the fourth period according to the feedback voltage Va of the second period Tons of the fourth period. In this case, the oscillation condition of the feedback voltage Va during the third period Toff of the fourth period CY will be similar to the oscillation condition of the feedback voltage Va during the third period Toff of the first period CY1 or during the third period Toff of the second period CY 2.

Referring to fig. 5B as an example, when the PSR controller 212 detects that the feedback voltage Va returns to the voltage value before the step change (e.g., the value equal to the voltage value 530') in the fourth period after the second period CY2, the PSR controller 212 may release the adjustment of the feedback voltage Va, i.e., return to the oscillation condition of adjusting the feedback voltage Va of the third period Toff of the fourth period according to the feedback voltage Va of the second period Tons of the fourth period. In this case, the oscillation condition of the feedback voltage Va during the third period Toff of the fourth period CY will be similar to the oscillation condition of the feedback voltage Va during the third period Toff of the first period CY1 or during the third period Toff of the second period CY 2.

In other embodiments, the time points at which the PSR controller 212 detects the step change, adjusts the feedback voltage, and de-adjusts may also be adaptively adjusted according to the designer's needs. For example, the PSR controller 212 may perform the method of the present invention once in each adjacent cycle to detect whether step change occurs, and accordingly determine whether to adjust the feedback voltage and to release the adjustment (hereinafter referred to as an adjacent detection means).

Fig. 6A is a schematic diagram illustrating the embodiment of fig. 2, in which the adjacent detection means is used without adjusting the feedback voltage and the cancellation. In the present embodiment, it is assumed that the SR224 is off in the period CY (a) (a is a positive integer) and is turned on to be switched to an on state in the period CY (a + 1). As mentioned above, since the PSR controller 212 employs the adjacent detection means, the feedback voltage Va is detected to have a step change (e.g. from 2.5V to 2.2V) in the period CY (a + 1). However, since the feedback voltage Va is not adjusted in response to the step change in this embodiment, the output voltage Vo is improperly adjusted to another voltage value (e.g., 5.6V) in a certain period later.

Further, it is assumed that SR224 is turned on in the cycle CY (k) (k is a positive integer) and is turned off in the cycle CY (k +1) to be switched to the diode state. Similarly, since the PSR controller 212 employs the adjacent detection means, the feedback voltage Va is detected to be stepped (e.g. from 2.2V to 2.5V) in the cycle CY (k + 1). Accordingly, the output voltage Vo will again be improperly regulated to another voltage value (e.g., 5V) in some period thereafter.

Referring to fig. 6B, a schematic diagram of adjusting the feedback voltage and releasing the adjustment by using the adjacent detection means according to the embodiment of fig. 6A is shown. In the present embodiment, it is also assumed that the SR224 is turned off in the period CY (a) and turned on in the period CY (a +1) to be switched on. As mentioned above, since the PSR controller 212 employs the adjacent detection means, the feedback voltage Va is detected to have a step change in the cycle CY (a + 1). In response to the step change, the PSR controller 212 may adjust the feedback voltage Va (not specifically shown) according to the teachings of the previous embodiments, so that the output voltage Vo may be appropriately adjusted to another voltage value (e.g., 5.2V).

Further, it is assumed that SR224 is turned on in the cycle CY (k) and turned off in the cycle CY (k +1) to switch to the diode state. Similarly, since the PSR controller 212 employs the adjacent detection means, it can detect the step change of the feedback voltage Va in the cycle CY (k + 1). In response to the step change, the PSR controller 212 may release the regulation of the feedback voltage Va (not specifically shown) according to the teaching of the previous embodiments, so that the output voltage Vo may be properly regulated to another voltage value (e.g., 5V).

In other embodiments, the PSR controller 212 may perform the method of the present invention once again every predetermined number of cycles (hereinafter, denoted by N, which is a positive integer) to detect whether the step change occurs, and accordingly determine whether to adjust the feedback voltage and release the adjustment (hereinafter, referred to as a skip detection means).

Fig. 7A is a schematic diagram illustrating the embodiment of fig. 2, in which the skip detection method is used without adjusting the feedback voltage and without adjusting the cancellation. In the present embodiment, it is assumed that SR224 is turned on and switched to the on state in a period CY (b) (b is a positive integer between j and (j + N)) between a period CY (j) (j is a positive integer) and a period CY (j + N). As mentioned above, since the PSR controller 212 employs the skip detection method, the feedback voltage Va is detected to be stepped (e.g. from 2.5V to 2.2V) in the period CY (j + N). However, since the feedback voltage Va is not adjusted according to the step change in the present embodiment, the output voltage Vo is improperly adjusted to another voltage value (e.g., 5.6V) in a period (e.g., between the period CY (j + N) and the period CY (j + 2N)) after the period.

Further, it is assumed that SR224 is turned off in a period CY (c) (c is a positive integer between (j +2N) and (j + 3N)) between the period CY (j +2N) and the period CY (j +3N) to be switched to the diode state. Similarly, since the PSR controller 212 employs the skip detection method, the feedback voltage Va is detected to be stepped (e.g., from 2.2V to 2.5V) in the period CY (j + 3N). Accordingly, the output voltage Vo is improperly adjusted to another voltage value (e.g., 5V) in a period (e.g., between the period CY (j +3N) and the period CY (j + 4N)) after the first period.

Referring to fig. 7B, a schematic diagram of adjusting the feedback voltage and releasing the adjustment by using the skip detection method according to the embodiment of fig. 7A is shown. In the present embodiment, it is also assumed that the SR224 is turned on and switched to the on state in the period CY (b) between the period CY (j) and the period CY (j + N). As mentioned above, since the PSR controller 212 employs the skip detection method, the feedback voltage Va is detected to be stepped (e.g. from 2.5V to 2.2V) in the period CY (j + N). In response to the step change, the PSR controller 212 may adjust the feedback voltage Va (not specifically shown) according to the teachings of the previous embodiments, so that the output voltage Vo may be appropriately adjusted to another voltage value (e.g., 5.2V).

Further, it is assumed that SR224 is turned off to be switched to the diode state in a period CY (c) between the period CY (j +2N) and the period CY (j + 3N). Similarly, since the PSR controller 212 employs the skip detection method, the feedback voltage Va is detected to be stepped (e.g., from 2.2V to 2.5V) in the period CY (j + 3N). In response to the step change, the PSR controller 212 may release the regulation of the feedback voltage Va (not specifically shown) according to the teaching of the previous embodiments, so that the output voltage Vo may be properly regulated to another voltage value (e.g., 5V).

In other embodiments, in the case of implementing the jump detection means, the step change of the detected feedback voltage Va can be further characterized by a change value between a first voltage average value and a second voltage average value (hereinafter, the jump average detection means), wherein the first voltage average value is an average value of the feedback voltage Va in the (j-N +1) th to (j) th periods, and the second voltage average value is an average value of the feedback voltage Va in the (j +1) th to (j + N) th periods, as described in detail below.

Fig. 8A is a schematic diagram illustrating the embodiment of fig. 7A with the skip-average detection method without adjusting the feedback voltage and without adjusting the cancellation. In the present embodiment, it is assumed that the SR224 is turned on and switched to the on state in a period CY (d) (d is a positive integer between j and (j + N)) between a period CY (j) (j is a positive integer) and a period CY (j + N). As mentioned above, the step change detected by the PSR controller 212 is slightly different from the previous embodiment because the PSR controller 212 employs the skip-average detection method. Specifically, the PSR controller 212 may first calculate an average value of the feedback voltage Va in the periods CY (j-N +1) to CY (j) as a first average value, and calculate an average value of the feedback voltage Va in the periods CY (j +1) to CY (j + N) as a second average value. Then, the PSR controller 212 may detect a step change based on a change value between the first average value and the second average value.

Similar to fig. 7A, the PSR controller 212 detects the step change of the feedback voltage Va in the cycle CY (j + N). However, since the feedback voltage Va is not adjusted in response to the step change in this embodiment, the output voltage Vo is improperly adjusted to another voltage value (e.g., 5.6V).

Further, it is assumed that SR224 is turned off to switch to the diode state in the period CY (j + 2N). Similarly, the PSR controller 212 may first calculate an average value of the feedback voltage Va in the periods CY (j +1) to CY (j + N) as a third average value, and calculate an average value of the feedback voltage Va in the periods CY (j + N +1) to CY (j +2N) as a fourth average value. Then, the PSR controller 212 may detect a step change based on a change value between the third average value and the fourth average value.

Since the PSR controller 212 employs the skip-average detection method, the PSR controller 212 will detect the step change of the feedback voltage Va in the cycle CY (j + 2N). Accordingly, the output voltage Vo will be improperly adjusted to another voltage value (e.g., 5V) thereafter.

Referring to fig. 8B, a schematic diagram of adjusting the feedback voltage and releasing the adjustment by using the skip-average detection method according to the embodiment of fig. 8A is shown. In the present embodiment, it is also assumed that the SR224 is turned on and switched to the on state in the period CY (d) between the period CY (j) and the period CY (j + N). As mentioned above, since the PSR controller 212 employs the skip-average detection method, the detection of the step change by the PSR controller 212 can be described with reference to fig. 8A, and will not be described herein again.

Similar to fig. 8A, the PSR controller 212 detects the feedback voltage Va as a step change during the period CY (j + N). In response to the step change, the PSR controller 212 may adjust the feedback voltage Va (not specifically shown) according to the teachings of the previous embodiments, so that the output voltage Vo may be appropriately adjusted to another voltage value (e.g., 5.2V).

Further, it is assumed that SR224 is turned off to switch to the diode state in the period CY (j + 2N). Similarly, since the PSR controller 212 employs the skip-average detection method, the PSR controller 212 may detect the step change of the feedback voltage Va only in the cycle CY (j + 3N). In response to the step change, the PSR controller 212 may release the regulation of the feedback voltage Va (not specifically shown) according to the teaching of the previous embodiments, so that the output voltage Vo may be properly regulated to another voltage value (e.g., 5V).

Fig. 9 is a waveform simulation diagram of the unregulated feedback voltage and the unregulated output voltage Vo and the unregulated feedback voltage Va according to an embodiment of the present invention. In fig. 9, the interval SR (off) and the interval SR (on) represent the intervals (which may each include several cycles) in which the SR is turned off and on, respectively. As shown in fig. 9, the feedback voltage Va will have

step changes

910, 920, 930, 940, 950 and 960 as SR is turned off and on. That is, the output voltage Vo has been improperly regulated many times, which is seen from the less smooth waveform of the output voltage Vo.

Referring to fig. 10, a waveform simulation diagram of the feedback voltage being adjusted and the output voltage Vo being released from being adjusted according to the step change and the feedback voltage Va according to an embodiment of the invention is shown. In fig. 10, the intervals SR (off) and SR (on) also represent the intervals when SR is turned off and on, respectively, the waveform 1000 is, for example, the waveform of the unregulated feedback voltage Va, and the waveform 1000' is, for example, the waveform of the regulated feedback voltage Va. As shown in fig. 10, the unregulated waveform 1000 will exhibit

step changes

1010, 1020, 1030, 1040, 1050 and 1060 as the SR is turned off and on. However, the adjusted waveform 1000' is smoother than the waveform 1000. Corresponding to the waveform 1000', the output voltage Vo also has a relatively smooth trend, which means that the output voltage Vo is not properly adjusted as shown in fig. 9.

Referring to fig. 11, a schematic diagram of the embodiment of fig. 9 showing the skip average detection method is shown. In the present embodiment, the PSR controller may calculate the average values of the feedback voltage Va in the section a1, the section a2, the section A3, the section a4, the section a5, the section A6, the section a7, the section A8, the section a9, the section a10, the section a11, and the section a12, respectively, and accordingly determine whether the step change occurs. The PSR controller may then adjust or de-adjust the feedback voltage Va based on whether the step change occurs. The details of this embodiment can refer to the related descriptions of fig. 8A and fig. 8B, and are not described herein again.

In summary, the power converter with SR and PSR controllers and the voltage regulation method thereof according to the present invention can detect whether the feedback voltage has a step change through the above-mentioned various detection means (e.g. the adjacent detection means, the jump detection means, and the jump averaging means). When the step change is detected, the PSR controller of the present invention can also adjust the feedback voltage or release the adjustment of the feedback voltage accordingly, thereby avoiding the improper adjustment of the output voltage due to the SR state switching.

Claims

1. A power converter having a synchronous rectifier and a primary-side regulation controller, comprising:

a secondary side circuit including a coil and a synchronous rectifier coupled to the coil, the synchronous rectifier having a voltage thereon;

a primary side circuit, comprising:

a primary side adjustment controller; and

an additional winding coupled to the winding of the secondary-side circuit, the winding of the secondary-side circuit being sensed in a plurality of cycles to provide a feedback voltage to the primary-side regulation controller, wherein the feedback voltage is related to the voltage on the synchronous rectifier, and the plurality of cycles comprises at least a first cycle, a second cycle, and a third cycle; and

the primary side regulation controller determines whether a step change of the feedback voltage is detected in a specific period of a second period, and regulates the feedback voltage in the second period or the third period when the primary side regulation controller detects the step change of the feedback voltage in the specific period of the second period.

2. The power converter of claim 1, wherein the synchronous rectifier operates in an on state when the synchronous rectifier is on and in a diode state when the synchronous rectifier is off.

3. The power converter of claim 2, wherein the step change is in the form of a step increment and the switching of the synchronous rectifier from the conducting state to the diode state causes the step change in the feedback voltage.

4. The power converter of claim 2, wherein the step change is in the form of a step decrement, and the switching of the synchronous rectifier from the diode state to the conducting state causes the step change in the feedback voltage.

5. The power converter of claim 1 wherein when the primary-side regulation controller detects the step change in the feedback voltage during the specific period of the second cycle, the primary-side regulation controller regulates an oscillation condition of the feedback voltage during the second cycle according to a voltage value of the feedback voltage during a specific period of the first cycle or the specific period of the second cycle.

6. The power converter of claim 5 wherein the first period and the second period each comprise a first period, a second period and a third period in succession, the second period of the first period being the specific period of the first period, the second period of the second period being the specific period of the second period,

the primary side regulation controller regulates the oscillation condition of the feedback voltage in the third period of the second period according to the voltage value of the feedback voltage in the second period of the first period.

7. The power converter of claim 6, wherein a time length difference between the third period of the first cycle and the third period of the second cycle is less than a predetermined threshold.

8. The power converter of claim 6, wherein the first period is charging, the second period is discharging, and the third period is off.

9. The power converter of claim 1 wherein the second period is subsequent to the first period.

10. The power converter of claim 9, wherein the second period is a next period of the first period.

11. The power converter of claim 9, wherein the second period is a predetermined number of periods away from the first period.

12. The power converter of claim 11 wherein the first period and the second period are respectively characterized as (j) th period and (j + N) th period, wherein j is a positive integer and N is the predetermined number,

the step change is a change value between a first voltage average value and a second voltage average value, wherein the first voltage average value is an average value of the feedback voltage in the (j-N +1) th to (j) th periods, and the second voltage average value is an average value of the feedback voltage in the (j +1) th to (j + N) th periods.

13. The power converter of claim 1, wherein the step change is a change between the feedback voltage in the specific period of the second cycle and the feedback voltage in the specific period of the first cycle.

14. The power converter of claim 1, further comprising: when the primary side adjusting controller detects that the feedback voltage returns to the voltage value before the step change occurs in a specific period of a fourth period, the primary side adjusting controller adjusts an oscillation condition of the feedback voltage in the fourth period according to the voltage value of the feedback voltage in the specific period of the fourth period.

15. The power converter of claim 1, wherein the primary-side regulation controller comprises a first input terminal, a second input terminal, a third input terminal, an output terminal, and a ground pin, and the primary-side circuit further comprises:

a power supply having a first end and a second end connected to a ground end;

a first resistor having a first end coupled to the first end of the power supply;

a capacitor, a first end of which is coupled to a second end of the first resistor, and a second end of which is coupled to the ground terminal;

a first coil having a first end coupled to the first end of the power supply;

a switch, a first end of which is coupled to a second end of the first coil, and a control end of which is coupled to the output end of the primary side adjusting controller;

a second resistor, a first end of which is coupled to a second end of the switch and the second input end of the primary side regulation controller, and a second end of which is coupled to the ground terminal;

a diode having a cathode coupled to the first end of the capacitor and the first input end of the primary side regulator controller, and an anode coupled to a first end of the extra coil;

a third resistor, a first end of which is coupled to the anode of the diode, and a second end of which is coupled to the third input end of the primary side regulation controller; and

a first end of the fourth resistor is coupled to the second end of the third resistor, and a second end of the fourth resistor is coupled to the ground terminal, a second end of the additional coil, and the ground pin of the primary-side adjustment controller.

16. The power converter of claim 1, wherein the winding of the secondary-side circuit includes a first terminal and a second terminal, the synchronous rectifier includes a first terminal, a second terminal and a control terminal, and the secondary-side circuit further includes:

a synchronous rectifier controller having a first input terminal coupled to the first end of the coil of the secondary side circuit, a second input terminal coupled to the second end of the coil of the secondary side circuit and the first end of the synchronous rectifier, an output terminal coupled to the control terminal of the synchronous rectifier, and a ground pin;

a capacitor, a first end of which is coupled to the first end of the coil of the secondary side circuit, and a second end of which is coupled to a ground terminal, the second end of the synchronous rectifier and the ground pin of the synchronous rectifier controller; and

a load, a first end of which is coupled to the first end of the coil of the secondary side circuit, and a second end of which is coupled to the ground terminal.

17. A method of voltage regulation for a power converter including a primary side circuit and a secondary side circuit, the primary side circuit including a primary side regulation controller and an additional winding, the secondary side circuit including a winding and a synchronous rectifier, the additional winding coupled to the winding of the secondary side circuit, the method comprising:

sensing the coil of the secondary side circuit by the additional coil in a first cycle to provide a feedback voltage to the primary side regulation controller, wherein the feedback voltage is associated with a voltage on the synchronous rectifier;

the primary side regulating controller judges whether a step change of the feedback voltage is detected in a specific period of a second period; and

when the primary side regulation controller detects the step change of the feedback voltage in the specific period of the second period, the primary side regulation controller regulates the feedback voltage in the second period or a third period.

18. The method of claim 17, wherein the synchronous rectifier operates in an on state when the synchronous rectifier is on and in a diode state when the synchronous rectifier is off.

19. The method of claim 18, wherein the step change is in the form of a step increment and the switching of the synchronous rectifier from the conducting state to the diode state causes the step change in the feedback voltage.

20. The method of claim 18, wherein the step change is in the form of a step decrement, and the switching of the synchronous rectifier from the diode state to the conducting state causes the step change in the feedback voltage.

21. The method of claim 17, wherein the step of adjusting the feedback voltage in the second period or the third period by the primary-side adjustment controller comprises: and adjusting an oscillation condition of the feedback voltage in the second period by the primary side adjustment controller according to a voltage value of the feedback voltage in a specific period of the first period or the specific period of the second period.

22. The method of claim 21, wherein the first period and the second period each include a first period, a second period and a third period in succession, the second period of the first period being the specific period of the first period, the second period of the second period being the specific period of the second period,

wherein the step of the primary side regulation controller regulating the feedback voltage in the second period or the third period comprises: adjusting, by the primary-side adjustment controller, the oscillation condition of the feedback voltage in the third period of the second period according to the voltage value of the feedback voltage in the second period of the first period.

23. The method of claim 22, wherein a time length difference between the third period of the first cycle and the third period of the second cycle is less than a predetermined threshold.

24. The method of claim 22, wherein the first period is charging, the second period is discharging, and the third period is off.

25. The method of claim 17, wherein the second period is subsequent to the first period.

26. The method of claim 25, wherein the second period is a next period of the first period.

27. The method of claim 25, wherein the second period is a predetermined number of periods apart from the first period.

28. The method of claim 27, wherein the first period and the second period are respectively characterized as a (j) th period and a (j + N) th period, wherein j is a positive integer and N is the predetermined number,

29. The voltage regulation method of claim 17, further comprising: when the primary side regulation controller detects that the feedback voltage returns to a voltage value before the step change occurs in a fourth period, the primary side regulation controller regulates an oscillation condition of the feedback voltage in the fourth period according to the voltage value.