Isolated power converter with adjusted Bode diagram characteristics and related regulator thereof

Abstract

The invention discloses an isolated power converter capable of adjusting Bode diagram characteristics and a related adjuster thereof. The adjustment circuit is included in a secondary side controller. The adjustment circuit includes a voltage divider, a buffer, a first variable resistor, a second variable resistor, an amplifier, and an N-type metal oxide semiconductor transistor. The buffer is coupled with the voltage divider; the first variable resistor is coupled with an external resistor arranged outside the secondary side controller; the second variable resistor is coupled with the first variable resistor and the buffer; the amplifier is coupled with the first variable resistor and the second variable resistor; the N-type metal oxide semiconductor transistor is coupled with the amplifier, the first external capacitor, the bias resistor and the optical coupler. Therefore, the characteristics of the Bode diagram of the isolated power converter can be adjusted through the first variable resistor and the second variable resistor.

Description

Technical Field

[0001] The present invention relates to an isolated power converter and its related regulator, and particularly to an isolated power converter and its related regulator that change the characteristics of the Bode plot of the isolated power converter through components within an integrated circuit. Background Art

[0002] In the prior art, the controller circuit on the secondary side of an AC / DC isolated power converter is composed of discrete components (such as resistors, capacitors, and optocouplers, etc.). Therefore, when the AC / DC isolated power converter is produced, these discrete components are already determined, that is, after the AC / DC isolated power converter is produced, the characteristics of the controller circuit are fixed. However, when the isolated power converter is designed to comply with the Universal Serial Bus Power Delivery Charging Specification Version 3.1 (USB PD 3.1) or other applications with a wide output voltage range, etc., the AC / DC isolated power converter needs to operate in a larger output voltage range.

[0003] But because the controller circuit is composed of discrete components (such as resistors, capacitors, and optocouplers, etc.) and these discrete components cannot be changed after the AC / DC isolated power converter is produced, so when the AC / DC isolated power converter needs to operate in a larger output voltage range, the controller circuit may not be easily designed to cope with the situation of a larger output voltage range, resulting in the AC / DC isolated power converter being unable to ensure good response characteristics in a wide output voltage range. Therefore, how to make the response characteristics of the AC / DC isolated power converter not easily affected by the wide output voltage range has become an important issue for the designers of the controller circuit. Summary of the Invention

[0004] An embodiment of the present invention discloses an adjustment circuit, wherein the adjustment circuit is included in a secondary side controller, and the secondary side controller is disposed on the secondary side of an isolated power converter. The adjustment circuit includes a voltage divider, a buffer, a first variable resistor, a second variable resistor, an amplifier, and an N-type metal oxide semiconductor transistor. The buffer is coupled to the voltage divider; the first variable resistor is coupled to an external resistor disposed outside the secondary side controller; the second variable resistor is coupled to the first variable resistor and the buffer; the amplifier is coupled to the first variable resistor and the second variable resistor; and the N-type metal oxide semiconductor transistor is coupled to the amplifier and a first external capacitor, a bias resistor, and an optocoupler disposed outside the secondary side controller; wherein the first variable resistor and the second variable resistor are used to adjust the characteristics of the Bode plot of the isolated power converter.

[0005] Another embodiment of the present invention discloses an adjustment circuit, wherein the adjustment circuit is included in a secondary-side controller, and the secondary-side controller is disposed on the secondary side of an isolated power converter. The adjustment circuit includes a voltage divider, a variable resistor, an amplifier, and an N-type metal oxide semiconductor transistor. The variable resistor is coupled to an external resistor disposed outside the secondary-side controller and the voltage divider; the amplifier is coupled to the variable resistor and the voltage divider; and the N-type metal oxide semiconductor transistor is coupled to the amplifier and a first external capacitor, a bias resistor, and an optocoupler disposed outside the secondary-side controller; wherein the variable resistor is used to adjust the characteristics of a Bode plot of the isolated power converter.

[0006] Another embodiment of the present invention discloses an isolated power converter having adjustable Bode plot characteristics. The isolated power converter includes a secondary-side controller, wherein the secondary-side controller is disposed on the secondary side of the isolated power converter to control the secondary side of the isolated power converter to receive energy from the primary side of the isolated power converter and generate an output voltage accordingly, and the secondary-side controller includes an adjustment circuit. The adjustment circuit includes a voltage divider, a buffer, a first variable resistor, a second variable resistor, an amplifier, and an N-type metal oxide semiconductor transistor. The buffer is coupled to the voltage divider; the first variable resistor is coupled to an external resistor disposed outside the secondary-side controller; the second variable resistor is coupled to the first variable resistor and the buffer; the amplifier is coupled to the first variable resistor and the second variable resistor; and the N-type metal oxide semiconductor transistor is coupled to the amplifier and a first external capacitor, a bias resistor, and an optocoupler disposed outside the secondary-side controller; wherein the first variable resistor and the second variable resistor are used to determine the characteristics of a Bode plot of the isolated power converter.

[0007] Another embodiment of the present invention discloses an isolated power converter with adjusted Bode plot characteristics. The isolated power converter includes a secondary-side controller, where the secondary-side controller is disposed on the secondary side of the isolated power converter to control the secondary side of the isolated power converter to receive energy from the primary side of the isolated power converter and generate an output voltage accordingly. The secondary-side controller includes an adjustment circuit. The adjustment circuit includes a voltage divider, a variable resistor, an amplifier, and an N-type metal oxide semiconductor transistor. The variable resistor is coupled to an external resistor disposed outside the secondary-side controller and the voltage divider; the amplifier is coupled to the variable resistor and the voltage divider; and the N-type metal oxide semiconductor transistor is coupled to the amplifier and a first external capacitor, a bias resistor, and an optocoupler disposed outside the secondary-side controller. Wherein the variable resistor is used to adjust the characteristics of the Bode plot.

[0008] The present invention discloses an adjustment circuit and an isolated power converter with adjusted Bode plot characteristics. Since the adjustment circuit and the isolated power converter can change the characteristics of the Bode plot (corresponding to the frequency response of the isolated power converter) through components within the secondary-side controller (integrated circuit), compared with the prior art, when the isolated power converter needs to operate in a large output voltage range, the isolated power converter of the present invention can adjust the characteristics of the Bode plot of the isolated power converter according to different operating conditions to ensure that the isolated power converter has certain response characteristics under wide output voltage range conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic diagram of a secondary-side adjustable characteristic controller applied to an isolated power converter disclosed in the first embodiment of the present invention.

[0010] Figure 2 is a schematic diagram showing the change of the Bode plot gain with respect to frequency and the change of phase with respect to frequency of the controller when the resistance value of the second variable resistor changes.

[0011] Figure 3 is a schematic diagram showing the change of the Bode plot gain with respect to frequency and the change of phase with respect to frequency of the controller when the resistance value of the first variable resistor changes.

[0012] Figure 4 is a schematic diagram showing the first variable resistor and the second variable resistor.

[0013] Figure 5 is a schematic diagram of a secondary-side adjustable characteristic controller applied to an isolated power converter disclosed in the second embodiment of the present invention.

[0014] Figure 6 It is a schematic diagram showing the change of the Bode plot gain of the controller with respect to frequency and the change of phase with respect to frequency when the resistance value of the first variable resistor changes.

[0015] Among them, the reference numerals are explained as follows:

[0016] 100 Isolated power converter

[0017] 102 Optocoupler

[0018] 104, RS1-RS3, RI1-RI3 Resistors

[0019] 106 First external capacitor

[0020] 108 Bias resistor

[0021] 109 External resistor

[0022] 110 Second external capacitor

[0023] 112 Parasitic capacitor

[0024] 200, 400 Secondary side controllers

[0025] 250 Primary side controller

[0026] 2502 Pull-up resistor

[0027] 300, 350 Adjustment circuits

[0028] 302 Voltage divider

[0029] 304 Buffer

[0030] 306 First variable resistor

[0031] 308 Second variable resistor

[0032] 310 Amplifier

[0033] 312 N-type metal oxide semiconductor transistor

[0034] 3022 First resistor

[0035] 3024 Second resistor

[0036] COMP, OPTO, VSEN, VCC Pins

[0037] FWC1 First control signal

[0038] FWC2 Second control signal

[0039] GND1 and GND2 levels

[0040] PRI primary side

[0041] SEC secondary side

[0042] VDD supply voltage

[0043] VBIAS bias voltage

[0044] VOUT output voltage

[0045] VREF reference voltage Detailed implementation manners

[0046] Please refer to Figure 1 , Figure 1 FIG. is a schematic diagram of a secondary side controller 200 applied to an isolated power converter 100 disclosed in the first embodiment of the present invention, wherein the secondary side adjustable characteristic controller 200 includes an adjustment circuit 300, and the secondary side controller 200 is disposed on the secondary side SEC of the isolated power converter 100. As Figure 1 shown, the adjustment circuit 300 includes a voltage divider 302, a buffer 304, a first variable resistor 306, a second variable resistor 308, an amplifier 310, and an N-type metal oxide semiconductor transistor 312. The voltage divider 302 includes a first resistor 3022 and a second resistor 3024. The coupling relationships among the voltage divider 302, the buffer 304, the first variable resistor 306, the second variable resistor 308, the amplifier 310, the N-type metal oxide semiconductor transistor 312, the first resistor 3022, and the second resistor 3024 can be referred to Figure 1 , and will not be elaborated herein. In addition, the level GND1 of the ground terminal of the primary side PRI of the isolated power converter 100 is different from the level GND2 of the ground terminal of the secondary side SEC of the isolated power converter 100. In addition, since the present invention is about the adjustment circuit 300, for simplicity Figure 1 , in Figure 1 , only the relevant components of the primary side PRI of the isolated power converter 100, the secondary side SEC of the isolated power converter 100, the secondary side controller 200, and the primary side controller 250 disposed on the primary side PRI of the isolated power converter 100 are illustrated, that is, the primary side PRI of the isolated power converter 100, the secondary side SEC of the isolated power converter 100, the secondary side controller 200, and the primary side controller 250 are not limited to only including Figure 1The components shown. Additionally, the amplifier 310 and the N-type metal oxide semiconductor transistor 312 are used to mimic the behavior of a TL431 (precision voltage reference IC), and the secondary side controller 200 and the primary side controller 250 are integrated circuits. Additionally, as Figure 1 shown, the optocoupler 102 for isolating the primary side PRI of the isolated power converter 100 and the secondary side SEC of the isolated power converter 100, a resistor 104 coupled to the optocoupler 102, a first external capacitor 106 coupled to the secondary side controller 200, a bias resistor 108 and an external resistor 109, and a second external capacitor 110 coupled to the optocoupler 102 are discrete components on a printed circuit board, where the isolated power converter 100, the secondary side controller 200, and the primary side controller 250 are disposed on the printed circuit board. Additionally, the coupling relationship between the secondary side controller 200 and the optocoupler 102, the resistor 104, the first external capacitor 106, the bias resistor 108, and the external resistor 109 outside the secondary side controller 200 can be referred to Figure 1 , which will not be elaborated here. Additionally, as Figure 1 shown, the optocoupler 102, the first external capacitor 106, and the bias resistor 108 are coupled to the secondary side controller 200 through a pin OPTO, the external resistor 109 is coupled to the secondary side controller 200 through a pin VSEN, and the secondary side controller 200 is coupled to the output terminal of the secondary side SEC of the isolated power converter 100 through a pin VCC, where the output terminal has an output voltage VOUT. Additionally, as Figure 1 shown, VDD is the supply voltage of the primary side controller 250, and the resistor 104 is coupled to a bias voltage VBIAS. Additionally, as Figure 1 shown, the amplifier 310 is further used to receive a reference voltage VREF.

[0047] To illustrate how the adjustment circuit 300 adjusts the characteristics of the Bode plot of the isolated power converter 100 through the secondary side controller 200, taking the adjustment circuit 300 as a Type 2 compensator as an example, where the Bode plot of the isolated power converter 100 (corresponding to the second type compensator) has 2 poles and 1 zero, and the transfer function G(s) of the adjustment circuit 300 can be expressed by Equation (1):

[0048]

[0049] In Equation (1):

[0050] CTR (Current Transfer Ratio) is the current transfer ratio of the optocoupler 102;

[0051] R pullup is the resistance value of the pull-up resistor 2502 for the pin COMP of the primary-side controller 250 coupled to the primary side PRI of the isolated power converter 100;

[0052] R LED is the resistance value of the resistor 104 coupled to the optocoupler 102;

[0053] R up is the resistance value of the first resistor 3022;

[0054] R dn is the resistance value of the second resistor 3024;

[0055] R S is the resistance value of the first variable resistor 306;

[0056] R i is the resistance value of the second variable resistor 308;

[0057] R2 is the resistance value of the external resistor 109;

[0058] C1 is the capacitance value of the first external capacitor 106;

[0059] C2 is the capacitance value of the second external capacitor 110; and

[0060] C opto is the capacitance value of the parasitic capacitance 112 of the optocoupler 102.

[0061] According to Equation (1), a zero-pole ω p0 , a first pole ω p1 and a zero ω z1 of the Bode plot can be represented by Equation (2), Equation (3), and Equation (4) respectively:

[0062]

[0063]

[0064]

[0065] After that, the frequencies corresponding to the zero-pole ω p0 , the first pole ω p1 and the zero ω z1 of the Bode plot can be represented by Equation (5), Equation (6), and Equation (7) respectively:

[0066]

[0067]

[0068]

[0069] Since the optocoupler 102, resistor 104, first external capacitor 106, external resistor 109, and second external capacitor 110 are discrete components on the printed circuit board, the capacitance value C of the parasitic capacitance 112 opto , the resistance value R of the resistor 104 LED , the capacitance value C1 of the first external capacitor 106, the resistance value R2 of the external resistor 109, and the capacitance value C2 of the second external capacitor 110 will not change after the system vendor sets the isolated power converter 100, secondary side controller 200, and primary side controller 250 on the printed circuit board. Therefore, from Figure 1 and Equations (2), (3), and (4), it is obvious that, compared with the prior art, the adjustment circuit 300 can determine the frequency positions of the poles and zeros in the Bode plot through the resistance value R S of the first variable resistor 306 and the resistance value R i of the second variable resistor 308. That is to say, the adjustment circuit 300 can adjust the frequency response characteristics of the isolated power converter 100 through the resistance value R S of the first variable resistor 306 and the resistance value R i of the second variable resistor 308.

[0070] Please refer to Figure 2 and Figure 3 . Figure 2 is a schematic diagram showing the gain versus frequency and phase versus frequency in the Bode plot when the resistance value R i of the second variable resistor 308 changes, and Figure 3 is a schematic diagram showing the gain versus frequency and phase versus frequency in the Bode plot when the resistance value R S of the first variable resistor 306 changes. Taking the resistance value R i as 180 kΩ, 90 kΩ, and 45 kΩ as examples, it is obvious from Equation (2) that decreases as the resistance value R i increases, and it is also obvious from Equation (5) that decreases as the resistance value R i increases. Therefore, as shown in Figure 2 , the change in the resistance value R i will change the frequency position of the zero-pole ω p0 , resulting in changes in the DC gain of the Bode plot and the phase of the Bode plot as the resistance value R ichanges, where the maximum change in DC gain, ΔDC Gain, is approximately 15 dB and the maximum change in phase, ΔMAX Phase, is approximately 5 degrees.

[0071] In addition, taking resistance values R S of 100 kΩ, 50 kΩ, and 25 kΩ as examples, it can be clearly seen from Equation (4) that as the resistance value R S increases, it decreases, and it can also be clearly seen from Equation (7) that as the resistance value R S increases, it decreases. Therefore, as shown in Figure 3 , the change in the resistance value R S will change the frequency position of the zero point ω z1 , resulting in the middle gain of the Bode plot and the phase of the Bode plot also changing with the change in the resistance value R S . Among them, the maximum change in the middle gain, ΔMiddle Gain, is approximately 10 dB and the maximum change in phase, ΔMAX Phase, is approximately 10 degrees.

[0072] Please refer to Figure 4 , Figure 4 which is a schematic diagram illustrating the first variable resistor 306 and the second variable resistor 308. The first variable resistor 306 includes resistors RS1 - RS3 and switches 3062, 3064. The second variable resistor 308 includes resistors RI1 - RI3 and switches 3082, 3084. And the adjustment circuit 300 can adjust the resistance value R S of the first variable resistor 306 through a first control signal FWC1 and adjust the resistance value R i of the second variable resistor 308 through a second control signal FWC2. Therefore, taking the first variable resistor 306 as an example, when the first control signal FWC1 is enabled and the first control signal FWC1 causes the switch 3062 to be turned on and the switch 3064 to be turned off, the resistance value R S of the first variable resistor 306 is equal to the resistance value after the parallel connection of the resistor RS1 and the resistor RS2. In addition, taking the second variable resistor 308 as an example, when the second control signal FWC2 is enabled and the second control signal FWC2 causes the switches 3082, 3084 to be turned on, the resistance value R i of the second variable resistor 308 is equal to the resistance value after the parallel connection of the resistor RI1, the resistor RI2, and the resistor RI3. In addition, the present invention is not limited to Figure 4 the configurations of the first variable resistor 306 and the second variable resistor 308 shown. That is to say, as long as the resistance value R S of the first variable resistor 306 and the resistance value R of the second variable resistor 308 are adjusted through control signalsi All fall within the scope of the present invention.

[0073] Please refer to Figure 5 , Figure 5 , which is a schematic diagram of a secondary-side controller 400 applied to an isolated power converter 100 disclosed in the second embodiment of the present invention, wherein the secondary-side controller 400 includes an adjustment circuit 350. As Figure 5 shown, the difference between the adjustment circuit 350 and the adjustment circuit 300 is that the adjustment circuit 350 includes a voltage divider 302, a first variable resistor 306, an amplifier 310, and an N-type metal oxide semiconductor transistor 312. The coupling relationship between the voltage divider 302, the first variable resistor 306, the amplifier 310, the N-type metal oxide semiconductor transistor 312, the first resistor 3022, and the second resistor 3024 can be referred to Figure 5 , and will not be elaborated here. In addition, the configuration of the first variable resistor 306 can be referred to Figure 4 , and will not be elaborated here either.

[0074] Next, the transfer function G(s) of the adjustment circuit 350 can be expressed by Equation (8):

[0075]

[0076] In Equation (8):

[0077] CTR (Current Transfer Ratio) is the current transfer ratio of the optocoupler 102;

[0078] R pullup is the resistance value of the pull-up resistor 2502;

[0079] R LED is the resistance value of the resistor 104;

[0080] R1 is the resistance value of the first resistor 3022;

[0081] R S is the resistance value of the first variable resistor 306;

[0082] R2 is the resistance value of the external resistor 109;

[0083] C1 is the capacitance value of the first external capacitor 106;

[0084] C2 is the capacitance value of the second external capacitor 110; and

[0085] C opto is the capacitance value of the parasitic capacitor 112 of the optocoupler 102.

[0086] According to Equation (8), a zero-pole ω of the Bode plot of the isolated power converter 100p0 A first pole ω p1 and a zero ω z1 can be represented by equations (9), (10), and (11) respectively:

[0087]

[0088]

[0089]

[0090] After that, corresponding to the zero-pole ω p0 the first pole ω p1 and the zero ω z1 the frequencies can be represented by equations (5), (6), and (7) respectively.

[0091] Similarly, from Figure 5 and equations (9), (10), and (11), it is obvious that assuming the resistance value R1 of the first resistor 3022 is a fixed value, then compared with the prior art, the adjustment circuit 300 can still determine the frequency position of the zero of the Bode plot through the resistance value R S of the first variable resistor 306, that is, the adjustment circuit 350 can determine the characteristics of the Bode plot through the resistance value R S of the first variable resistor 306.

[0092] Therefore, please refer to Figure 6 , Figure 6 which shows the gain of the Bode plot with respect to the operating frequency of the isolated power converter 100 and the phase of the Bode plot with respect to the operating frequency of the isolated power converter 100 when the resistance value R S of the first variable resistor 306 changes. Taking the resistance values R i as 50 kΩ, 25 kΩ, and 5 kΩ as examples, it is obvious from equation (11) that decreases as the resistance value R S increases, and it is also obvious from equation (7) that decreases as the resistance value R S increases. So as Figure 6 shows, the change in the resistance value R S will change the frequency position of the zero ω z1 , resulting in the change of the middle gain of the Bode plot and the phase of the Bode plot with the change of the resistance value R S . Among them, the maximum change amount ΔMiddle Gain of the middle gain is about 4.7 dB and the maximum change amount ΔMAXPhase of the phase is about 10 degrees.

[0093] In summary, since the adjustment circuit and the isolated power converter disclosed in the present invention can change the characteristics of the Bode plot (corresponding to the frequency response of the secondary-side controller) of the isolated power converter through the components in the secondary-side controller (integrated circuit), compared with the prior art, when the isolated power converter needs to operate in a relatively large output voltage range, the compensator of the prior art cannot achieve the same characteristic performance in each range, while the present invention can make the frequency response of the isolated power converter less affected. Therefore, when the output voltage range of the isolated power converter is relatively wide, a stable frequency response characteristic can still be maintained.

[0094] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An adjustment circuit, wherein the adjustment circuit is included in a secondary-side controller, and the secondary-side controller is disposed on the secondary side of an isolated power converter, characterized in that Comprising: A voltage divider; A buffer, coupled to the voltage divider; A first variable resistor, coupled to an external resistor disposed outside the secondary side controller; A second variable resistor, coupled to the first variable resistor and the buffer; An amplifier, coupled to the first variable resistor and the second variable resistor; And An N-type metal oxide semiconductor transistor, coupled to the amplifier and a first external capacitor, a bias resistor, and an optocoupler disposed outside the secondary side controller; Wherein the first variable resistor and the second variable resistor are used to adjust the characteristics of the Bode plot of the isolated power converter.

2. The adjustment circuit according to claim 1, wherein The voltage divider comprises: A first resistor, coupled to the output terminal of the secondary side of the isolated power converter and the buffer; A second resistor, coupled to the first resistor, the buffer, and a ground terminal.

3. The adjustment circuit according to claim 2, characterized in that The transfer function G(s) of the Bode plot is: Where: CTR (Current Transfer Ratio) is the current transfer ratio of the optocoupler; R pullup is the resistance value of the pull-up resistor for the compensation pin of the primary-side controller coupled to the primary side of the isolated power converter; R LED is the resistance value of the resistor coupled to the optical coupler; R up is the resistance value of the first resistor of the voltage divider; R dn is the resistance value of the second resistor of the voltage divider; R S is the resistance value of the first variable resistor; R i is the resistance value of the second variable resistor; R2 is the resistance value of the external resistor; C1 is the capacitance value of the first external capacitor; C2 is the capacitance value of a second external capacitor coupled to the compensation pin and the optocoupler; and C opto is the capacitance value of the parasitic capacitance of the optical coupler.

4. The adjustment circuit according to claim 3, wherein: is the zero pole of the transfer function G(s); is the first pole of the transfer function G(s); and is a zero of the transfer function G(s).

5. The adjustment circuit according to claim 1, characterized in that The secondary side controller is an integrated circuit.

6. The adjustment circuit according to claim 1, wherein The first variable resistor and the second variable resistor adjust the characteristics of the Bode plot by the positions of the poles and zeros of the Bode plot.

7. An adjustment circuit, wherein the adjustment circuit is included in a secondary-side controller, and the secondary-side controller is disposed on the secondary side of an isolated power converter, characterized in that Comprising: A voltage divider; A variable resistor, coupled to an external resistor disposed outside the secondary side controller and the voltage divider; An amplifier, coupled to the variable resistor and the voltage divider; And An N-type metal oxide semiconductor transistor, coupled to the amplifier and a first external capacitor, a bias resistor, and an optocoupler disposed outside the secondary side controller; Wherein the variable resistor is used to adjust the characteristics of a Bode plot of the isolated power converter.

8. The adjustment circuit according to claim 7, wherein The voltage divider comprises: A first resistor, coupled to the output terminal of the secondary side of the isolated power converter, the variable resistor, and the amplifier; A second resistor, coupled to the first resistor, the variable resistor, the amplifier, and a ground terminal.

9. The adjustment circuit according to claim 8, wherein The transfer function G(s) of the Bode plot is: Where: CTR is the current transfer ratio of the optocoupler; R pullup is the resistance value of the pull-up resistor for the compensation pin of the primary-side controller coupled to the primary side of the isolated power converter; R LED is the resistance value of the resistor coupled to the optical coupler; R1 is the resistance value of the first resistor of the voltage divider; R S is the resistance value of the variable resistor; R2 is the resistance value of the external resistor; C1 is the capacitance value of the first external capacitor; C2 is the capacitance value of a second external capacitor coupled to the compensation pin and the optocoupler; and C opto is the capacitance value of the parasitic capacitance of the optical coupler.

10. The adjustment circuit according to claim 9, wherein: are the zero and pole of the transfer function G(s); is the first pole of the transfer function G(s); and is a zero of the transfer function G(s).

11. The adjustment circuit according to claim 7, wherein The secondary side controller is an integrated circuit.

12. The adjustment circuit according to claim 7, wherein The variable resistor adjusts the characteristics of the Bode plot by the position of the zero of the Bode plot.

13. An isolated power converter with adjusted Bode plot characteristics, characterized in that Comprising: A secondary side controller, disposed on the secondary side of the isolated power converter, for controlling the secondary side of the isolated power converter to receive energy from the primary side of the isolated power converter and generate an output voltage accordingly, the secondary side controller comprising: An adjustment circuit, comprising: A voltage divider; A buffer, coupled to the voltage divider; A first variable resistor, coupled to an external resistor disposed outside the secondary side controller; A second variable resistor, coupled to the first variable resistor and the buffer; An amplifier, coupled to the first variable resistor and the second variable resistor; And An N-type metal oxide semiconductor transistor, coupled to the amplifier and a first external capacitor, a bias resistor, and an optocoupler disposed outside the secondary side controller; Wherein the first variable resistor and the second variable resistor are used to adjust the characteristics of the Bode plot.

14. The isolated power converter according to claim 13, wherein Further comprising: A primary side controller, disposed on the primary side of the isolated power converter, for controlling the primary side of the isolated power converter to transfer the energy of the primary side of the isolated power converter to the secondary side of the isolated power converter.

15. The isolated power converter according to claim 13, characterized in that The secondary side controller is an integrated circuit.

16. The isolated power converter according to claim 13, wherein The first variable resistor and the second variable resistor adjust the characteristics of the Bode plot by the positions of the poles and zeros of the Bode plot.

17. An isolated power converter with adjusted Bode plot characteristics, characterized in that Comprising: A secondary side controller, disposed on the secondary side of the isolated power converter, for controlling the secondary side of the isolated power converter to receive the energy from the primary side of the isolated power converter and generate an output voltage accordingly. The secondary side controller comprises: An adjustment circuit, comprising: A voltage divider; A variable resistor, coupled to an external resistor disposed outside the secondary side controller and the voltage divider; An amplifier, coupled to the variable resistor and the voltage divider; And An N-type metal oxide semiconductor transistor, coupled to the amplifier and a first external capacitor, a bias resistor, and an optocoupler disposed outside the secondary side controller; Wherein the variable resistor is used to adjust the characteristics of the Bode plot.

18. The isolated power converter according to claim 17, characterized in that Further comprising: A primary side controller, disposed on the primary side of the isolated power converter, for controlling the primary side of the isolated power converter to transfer the energy of the primary side of the isolated power converter to the secondary side of the isolated power converter.

19. The isolated power converter according to claim 17, wherein The secondary side controller is an integrated circuit.

20. The isolated power converter according to claim 17, characterized in that The variable resistor adjusts the characteristics of the Bode plot by the position of the zero of the Bode plot.

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