Resonant converter and operation method thereof

Abstract

A resonant converter and an operating method thereof are provided, the resonant converter converts a DC voltage into an output voltage, and the resonant converter includes a transformer, a primary side circuit, and a control module. The primary side circuit receives a DC voltage and includes a resonant circuit. The resonant circuit is coupled to the primary side winding of the transformer to form a resonant module. The control module controls the primary side circuit to convert the DC voltage so as to generate winding voltage at two ends of the resonance module. When the control module detects that the output current of the resonant converter is within the current interval between the preset current and the rated current, the control module adjusts the duty ratio of the winding voltage by a variable quantity so as to control the EMI value of the resonant converter to meet the standard value by adjusting the duty ratio.

Description

Technical Field

[0001] The present invention relates to a resonant converter and an operating method thereof, and in particular to a resonant converter with a frequency jitter function and an operating method thereof. Background Art

[0002] With the rapid development of the information industry, power supplies have played an indispensable role. The input voltage of information and household appliances is divided into AC voltage and DC voltage, and power supplies can generally be divided into two levels. Generally, the front stage is usually an AC / DC converter, a power factor corrector or a DC / DC converter, and the back stage is usually a resonant converter. Figure 1A As shown in FIG. 1 , when the power supply is applied to the AC mains voltage Vac input, the output voltage Vo of the front-stage AC / DC converter has the characteristic of twice the frequency of the mains voltage Vac. In order to adjust the output voltage, the operating frequency of the rear-stage DC / DC converter is as follows: Figure 1B As shown in the figure, the frequency range R1 of ±6kHz will change at the rated power of about 85kHz. This frequency variation of ±6kHz is similar to the characteristics of frequency gitter. Such characteristics can make the EMI energy generated by the DC / DC converter be evenly dispersed in the frequency range R1 of ±6kHz and the double frequency range of about 170kHz±12kHz. Therefore, better EMI suppression characteristics can be obtained.

[0003] However, if Figure 1C As shown, when the power supply is applied to the DC voltage Vdc input, the double frequency mains voltage will not appear in the output voltage Vo of the front stage DC / DC converter. Therefore, the operating frequency (such as Figure 1D As shown in the figure, the frequency range R2 will show a small change of ±0.2kHz. Since the operating frequency changes very little, the EMI energy generated by the DC / DC converter will be concentrated on N times the current operating frequency (N = 1, 2, 3...). Since there is no frequency jitter characteristic, the effect of suppressing EMI is extremely poor.

[0004] Therefore, the existing methods of solving the above problems in the prior art are: 1. Enhance the EMI attenuation capability, but this will make the design of the resonant converter more difficult, and it will not be possible to reduce the circuit volume and reduce the circuit cost. 2. By adjusting the operating frequency of the resonant converter, avoid the minimum safety limit specification value (150kHz). For example, if the operating frequency is designed to be 70kHz, the double frequency is 140kHz, which is still less than the specification value of 150kHz. Therefore, the design of the resonant converter will be limited. 3. Deliberately generate a frequency gitter effect. This approach is to fix the previous stage output voltage Vout, and deliberately change the operating frequency of the resonant converter by ±6kHz. However, since the operating frequency is deliberately changed, a low-frequency voltage ripple will be caused in the DC / DC output voltage Vout.

[0005] Therefore, how to design a resonant converter and its operating method so that the resonant converter has a better EMI suppression effect and the EMI value measured by the resonant converter meets the standard value is a major research topic that the inventors of this case want to conduct. Summary of the invention

[0006] In order to solve the above problems, the present disclosure provides a resonant converter to overcome the problems of the prior art. Therefore, the resonant converter of the present disclosure converts a DC voltage into an output voltage, and the resonant converter includes a transformer, a primary side circuit and a control module. The transformer includes a primary side winding, and the primary side circuit receives the DC voltage. The primary side circuit includes a resonant circuit, and the resonant circuit is coupled to the primary side winding to form a resonant module. The control module is coupled to the primary side circuit, and controls the primary side circuit to convert the DC voltage to generate a winding voltage at two ends of the resonant module. Among them, when the control module detects that the output current of the resonant converter is between a predetermined current and a rated current, the control module adjusts the duty cycle of the winding voltage by a change amount, so as to control the EMI value of the resonant converter to meet the specification value by adjusting the duty cycle.

[0007] In order to solve the above problems, the present disclosure provides an operating method of a resonant converter to overcome the problems of the prior art. Therefore, the resonant converter of the present disclosure includes a transformer and a primary side circuit, and the primary side circuit includes a resonant circuit. The resonant circuit is coupled to the primary side winding of the transformer to form a resonant module, and the operating method of the resonant converter includes the following steps: (a) Controlling the primary side circuit to convert the DC voltage to control the resonant converter to convert the DC voltage into an output voltage, and generating a winding voltage at two ends of the resonant module. (b) Detecting the output current of the resonant converter, and when it is determined that the output current is between a predetermined current and a rated current, adjusting the duty cycle of the winding voltage by a change amount. (c) Controlling the operating frequency of the resonant converter to change within a frequency range by adjusting the duty cycle, and the frequency range is positively correlated to the change amount.

[0008] The main purpose and effect of the present disclosure is that when the control module detects that the output current rises to a certain level, the control module adjusts the duty cycle of the winding voltage by a variation to achieve the function of frequency gitter to reduce the EMI value and make the EMI value meet the standard value.

[0009] In order to further understand the technology, means and effects adopted by the present invention to achieve the predetermined purpose, please refer to the following detailed description and drawings of the present invention. It is believed that the purpose, characteristics and features of the present invention can be understood in depth and in detail. However, the attached drawings are only provided for reference and explanation and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A A waveform diagram of an existing power supply when applied to an AC mains voltage input;

[0011] Figure 1B A frequency characteristic diagram of an existing resonant converter when applied to an AC mains voltage input;

[0012] Figure 1C A waveform diagram of a conventional power supply when applied to a DC voltage input;

[0013] Figure 1D A frequency characteristic diagram of an existing resonant converter when applied to a DC voltage input;

[0014] Figure 2A A circuit block diagram of a resonant converter with a frequency jitter function disclosed in the present invention;

[0015] Figure 2B is a current-frequency curve diagram of the first embodiment of the resonant converter disclosed in the present invention;

[0016] Figure 3A is a current-frequency curve diagram of the second embodiment of the resonant converter disclosed herein;

[0017] Figure 3B is a current-frequency curve diagram of the third embodiment of the resonant converter disclosed herein;

[0018] Figure 4A 1 is a circuit block diagram of a first embodiment of a resonant converter with a frequency jittering function disclosed in the present invention;

[0019] Figure 4B This is a signal waveform diagram of the first embodiment of the resonant converter with frequency jitter function disclosed in the present invention;

[0020] Figure 4CA circuit block diagram of a control module of a first embodiment of a resonant converter with a frequency jitter function disclosed herein;

[0021] Figure 5A is a circuit block diagram of a second embodiment of a resonant converter with a frequency jittering function disclosed in the present invention;

[0022] Figure 5B This is a signal waveform diagram of the second embodiment of the resonant converter with frequency jitter function disclosed in the present invention;

[0023] Figure 5C A circuit block diagram of a control module of a second embodiment of a resonant converter with a frequency jitter function according to the present disclosure;

[0024] Fig. 6A A method flow chart of the operating method of the first embodiment of the resonant converter with frequency jitter function disclosed in the present invention; and

[0025] Figure 6B The flowchart is a method of operating the second embodiment of the resonant converter with frequency jittering function disclosed in the present invention.

[0026]

Explanation of symbols

[0027] 100…Resonant Converter

[0028] 1… Transformer

[0029] 12…Primary winding

[0030] 122…Resonance module

[0031] a…first end

[0032] b…Second end

[0033] 14…Secondary winding

[0034] 2…Primary side circuit

[0035] 2A…Resonant circuit

[0036] 22…First bridge arm

[0037] Q1…First switch

[0038] Q2…Second switch

[0039] 24…Second bridge arm

[0040] Q3…Third switch

[0041] Q4…Fourth switch

[0042] Cr…Resonant capacitor

[0043] Lr…Resonant inductor

[0044] 3…Secondary side circuit

[0045] 4…Control module

[0046] 42…Comparator

[0047] 44…Voltage controller

[0048] 46…Pulse Width Modulator

[0049] 48…Duty cycle adjustment module

[0050] 5…Drive circuit

[0051] 200…Pre-stage circuit

[0052] 300...Load

[0053] Vac…mains voltage

[0054] Vdc…DC voltage

[0055] Vo…output voltage

[0056] Vab…winding voltage

[0057] Vref…reference voltage

[0058] Io…output current

[0059] Io_stop…predetermined current

[0060] Io_max…rated current

[0061] Ci…Current range

[0062] R1, R2, Δfsw…Frequency range

[0063] fsw…operating frequency

[0064] Sc1, Sc2, Sc3, Sc4…control signals

[0065] Sfb…Feedback signal

[0066] Ser…Error signal

[0067] D…Duty Cycle

[0068] Dp…predetermined value

[0069] Dl…critical value

[0070] Vpwm…Pulse width modulation value

[0071] Vm…Change value

[0072] M…Change

[0073] I, II, III… interval

[0074] Vs…phase shift

[0075] DT…Dead Time

[0076] Steps (S100) to (S360) DETAILED DESCRIPTION

[0077] The technical content and detailed description of the present invention are described as follows with reference to the accompanying drawings:

[0078] See also Figure 2A The circuit block diagram of the resonant converter with frequency jitter function disclosed in the present invention is as follows: Figure 2B is a current-frequency curve diagram of the first embodiment of the resonant converter disclosed in the present invention, and is also referred to in conjunction with Figure 1A to Figure 1D . The resonant converter 100 couples the front-stage circuit 200 and the load 300, and the front-stage circuit 200 can be, for example but not limited to, an AC / DC conversion circuit, a DC / DC conversion circuit, or a DC power provider such as a DC input source. The resonant converter 100 converts the DC voltage Vdc into an output voltage Vo, and provides an output current Io to the load 300 based on the power demand of the load 300. The resonant converter 100 includes a transformer 1, a primary side circuit 2, a secondary side circuit 3 and a control module 4, and the transformer 1 includes a primary side winding 12 and a secondary side winding 14. The primary side circuit 2 includes a resonant circuit 2A, the resonant circuit 2A is coupled to the primary side winding 12 to form a resonant module 122, and the secondary side circuit 3 is coupled to the secondary side winding 14. It is worth mentioning that in one embodiment, the resonant circuit 2A includes a resonant capacitor Cr and a resonant inductor Lr. Although they are shown in series in the figure, it is only a schematic example and is not limited to this. The resonant capacitor Cr and the resonant inductor Lr can also be connected in parallel.

[0079] The control module 4 is coupled to the primary side circuit 2 and the secondary side circuit 3, and the control module 4 controls the resonant converter 100 to convert the DC voltage Vdc into the output voltage Vo by controlling the primary side circuit 2 and the secondary side circuit 3. It is worth mentioning that in one embodiment, the control module 4 may include a controller (such as but not limited to a microcontroller, a central processing unit, etc.) and a detection circuit (such as but not limited to a current sensor, a voltage sensor, etc.) for detecting the voltage, current, etc. of each point (such as but not limited to an input end, an output end, etc.) of the resonant converter 100.

[0080] exist Figure 2BIn the figure, Io_min is the output current at no load, and Io_max is the output current at full load (or rated current). The lower the output current Io, the higher the operating frequency fsw of the resonant converter 100. Conversely, the higher the output current Io, the lower the operating frequency fsw of the resonant converter 100. Under this variable frequency operation (i.e., the operating frequency fsw varies with the output current Io), when a general resonant converter 100 converts the DC voltage Vdc into an output voltage Vo, a winding voltage Vab (which can be called an effective input voltage) is generated at both ends of the resonant module 122, and the duty cycle D of the winding voltage Vab is usually maintained at a predetermined value Dp (for example, but not limited to, an upper limit value of 50%, but can also be 45%, 40%, etc., which can be adjusted according to actual needs). However, if Figure 1A to Figure 1D As shown in the prior art, when the power supply is applied to the DC voltage Vdc input and the output current Io rises to a certain level, since the resonant converter 100 does not have a frequency gitter function, the resonant converter 100 has a very poor effect of suppressing EMI, which easily causes the EMI value measured by the resonant converter 100 to fail to meet the standard value (for example, but not limited to, the international standard of the International Electrotechnical Commission IEC).

[0081] Therefore, in order to make the EMI value measured by the resonant converter 100 meet the standard value, the present disclosure uses the frequency jitter function to reduce the EMI value when the output current Io rises to a certain level, so that the EMI value meets the standard value. Specifically, when the control module 4 detects that the output current Io of the resonant converter 100 is between the current interval Ci of the predetermined current Io_stop and the rated current Io_max, the control module 4 provides the frequency jitter function. That is, the control module 4 adjusts the duty cycle D of the winding voltage Vab by a change amount M so that the duty cycle D does not remain at the predetermined value Dp. When the change amount M is larger, the duty cycle D is smaller, and vice versa, the duty cycle D is larger. Among them, the change amount M varies between the predetermined value Dp and the critical value Dl according to the calculation of the control module 4, and the curve of the critical value Dl can be adaptively adjusted according to the needs of the resonant converter 100 (indicated by a dotted line). For example, but not limited to, when the change amount M is 10% and the duty cycle D is the upper limit value 50%, the duty cycle D will vary between the predetermined value Dp of 50% and the critical value Dl of 40%. Alternatively, when the change amount M is 5% and the duty cycle D is 45%, the duty cycle D will vary between the predetermined value Dp of 45% and the critical value Dl of 40%, or between the predetermined value Dp of 45% and the critical value Dl of 50%, and so on.

[0082] On the other hand, since the resonant converter 100 uses the frequency jitter function, when the output current Io is a fixed value, the operating frequency fsw of the resonant converter 100 will change accordingly with the change of the variation M. Therefore, when the output current Io is in the current interval Ci, the operating frequency fsw will change within a specific frequency range Δfsw, and the frequency range Δfsw is positively correlated with the variation M. For example, when the output current Io is fixed at 10A (10A is within the current interval Ci), and the current operating frequency fsw is 85kHz, the adjusted variation M varies between the predetermined value Dp and the critical value Dl of the variation M according to the calculation of the control module 4, and the operating frequency fsw varies between 85kHz and 75kHz or 85kHz and 95kHz according to the change of the variation M.

[0083] Therefore, when the change amount M calculated by the control module 4 is small, in order to keep the winding voltage Vab fixed, the amplitude of the change of the operating frequency fsw is also small. Conversely, when the change amount M calculated by the control module 4 is large, in order to keep the winding voltage Vab fixed, the amplitude of the change of the operating frequency fsw will be large. On the other hand, from the EMI characteristics of the converter (including the DC / DC converter), it can be known that the larger the output current Io, the larger the N-order harmonic energy generated by the current converter. Conversely, the smaller the output current Io, the smaller the N-order harmonic energy generated by the converter. This characteristic is limited by the EMI specification. When the output current Io is larger, the harmonic energy generated is larger, making the EMI value closer to the maximum limit value. Conversely, when the output current Io is smaller, the harmonic energy generated is smaller, making the EMI value farther from the maximum limit value. Therefore, when the output current Io is large (i.e., greater than or equal to the predetermined current Io_stop), by adjusting the duty cycle D by a change amount M, the EMI value of the resonant converter 100 can be controlled to meet the specification value.

[0084] See also Figure 3A is a current-frequency curve diagram of the second embodiment of the resonant converter disclosed in the present invention, and is also referred to in conjunction with Figure 2A to Figure 2B. The present disclosure utilizes the duty cycle D of the winding voltage Vab to change in response to the different output currents Io, and combines it with the EMI characteristics of the converter itself to operate the resonant converter 100. When the output current Io is large, the harmonic energy generated is also large. Therefore, in order to comply with regulatory restrictions, the adjustment of the variation M is large. Conversely, when the output current Io is small, the harmonic energy generated is also small, and the adjustment of the variation M is small or can remain unchanged. Therefore, when the control module 4 detects that the output current Io is less than the predetermined current Io_stop (interval I) or greater than the rated current Io_max (interval III), the control module fixes the duty cycle D to a predetermined value Dp (for example but not limited to 50%), so that the EMI value of the resonant converter 100 meets the specification value. That is, when the output current Io is not in the current interval Ci, the control module 4 controls the variation M to be zero, so that the duty cycle D is fixed at the predetermined value Dp. Therefore, in the intervals I and III, the operating frequency fsw is variable frequency, which changes according to the increase or decrease of the output current Io, and when the output current Io is a fixed value, the operating frequency fsw is substantially a constant value.

[0085] When the control module 4 detects that the output current Io is in the current interval Ci (interval II), the duty cycle D of the winding voltage Vab is the predetermined value Dp minus the variation M, and the control module 4 sets the critical value Dl of the variation M to a fixed value (i.e., the critical value Dl is a horizontal line). Similarly, the frequency range Δfsw corresponds to the critical value Dl and is in a specific range. Therefore, in interval II, the operating frequency fsw is still variable frequency, which changes according to the increase or decrease of the output current Io. In addition, in interval II, when the output current Io is a fixed value, the variation M changes between the predetermined value Dp and the critical value Dl according to the calculation of the control module 4, and the operating frequency fsw changes within a specific range accordingly with the change of the variation M. Therefore, in interval II, assuming that the predetermined value Dp of the duty cycle is an upper limit of 50%, and the variation M is 10%, the critical value Dl is 40% (i.e., 50% minus 10%). Accordingly, when the predetermined value Dp is the upper limit value of 50%, the corresponding operating frequency fsw is 85kHz, and the frequency range Δfsw corresponding to the change amount M of 10% is 10kHZ, and the operating frequency fsw varies between 85kHz and 75kHz according to the change amount M. It is worth mentioning that in one embodiment, when the predetermined value Dp of the duty cycle is other values, the above logic can be used and will not be repeated here.

[0086] See also Figure 3B is a current-frequency curve diagram of the third embodiment of the resonant converter disclosed in the present invention, and is also referred to in conjunction with Figure 2A to Figure 3A This embodiment and Figure 3AThe difference between the embodiments is that when the control module 4 detects that the output current Io is in the current interval Ci (interval II), the control module 4 sets the critical value Dl of the variation M to increase with the increase of the output current Io (i.e., the critical value Dl is a curve with a negative slope). Similarly, the frequency range Δfsw expands corresponding to the increase of the critical value Dl. Specifically, the larger the output current Io, the greater the N-order harmonic energy generated by the current converter. Therefore, the critical value Dl of the variation M increases with the increase of the output current Io, so that when the output current Io is larger, it has a better EMI suppression effect, making the EMI value less likely to approach the maximum limit value. It is worth mentioning that in one embodiment, Figure 3B Unspecified technical content, same as Figure 3A , I will not elaborate on it here.

[0087] See also Figure 4A The circuit block diagram of the first embodiment of the resonant converter with frequency jitter function disclosed in the present invention, Figure 4B The signal waveform diagram of the first embodiment of the resonant converter with frequency jitter function disclosed in the present invention is shown in FIG. Figure 2A to Figure 3B .exist Figure 4A In the embodiment, the resonant converter 100 is a full-bridge resonant converter, and the primary side circuit 2 further includes a first bridge arm 22 and a second bridge arm 24 connected in parallel. The first bridge arm 22 includes a first switch Q1 and a second switch Q2 connected in series, and the second bridge arm 24 includes a third switch Q3 and a fourth switch Q4 connected in series. The first end a of the resonant module 122 is coupled between the first switch Q1 and the second switch Q2, and the second end b of the resonant module 122 is coupled between the third switch Q3 and the fourth switch Q4. The control module 4 provides a first control signal Sc1 to control the first switch Q1, provides a second control signal Sc2 to control the second switch Q2, provides a third control signal Sc3 to control the third switch Q3, and provides a fourth control signal Sc4 to control the fourth switch Q4. Therefore, as Figure 4B As shown, through the control of the control module 4 , the primary side circuit 2 can convert the DC voltage Vdc and generate a winding voltage Vab between the first end a and the second end b of the resonance module 122 .

[0088] exist Figure 4B In the waveform diagram, the signal waveform on the left side corresponds to Figure 3A or Figure 3B In interval I or III, the signal waveform on the right side corresponds to Figure 3A or Figure 3Binterval II. Taking the predetermined value Dp of the duty cycle D as 50% as an example, when the control module 4 detects that the output current Io is not in the current interval Ci (i.e., in interval I or III), the control module 4 provides the first control signal Sc1 and the fourth control signal Sc4 with the same phase, and provides the second control signal Sc2 complementary to the first control signal Sc1, and provides the third control signal Sc3 complementary to the fourth control signal Sc4. Therefore, the winding voltage Vab forms a waveform of positive / negative voltage variation, and there is no dead time. However, the control signal is not limited to complete complementarity, and additional dead time may also be included between the two complementary control signals.

[0089] When the control module 4 detects that the output current Io is in the current interval Ci, the control module 4 controls the first control signal Sc1 and the fourth control signal Sc4 to have a phase shift amount Vs of phase change, so that the positive half-cycle duty cycle D of the winding voltage Vab decreases due to the sum of the first control signal Sc1 and the fourth control signal Sc4 (that is, when both are turned on at the same time, there is a current path to generate the winding voltage Vab), and then adjusts the change amount M by adjusting the phase shift amount Vs. Among them, the first control signal Sc1 and the second control signal Sc2 are corresponding opposite signals, and the fourth control signal Sc4 and the third control signal Sc3 are corresponding opposite signals, so controlling the first control signal Sc1 or the fourth control signal Sc4 can make the second control signal Sc2 or the third control signal Sc3 make corresponding adjustments.

[0090] On the other hand, when the control module 4 detects that the output current Io is in the current interval Ci, the control module 4 controls the second control signal Sc2 and the third control signal Sc3 to have a phase shift amount Vs of phase change, so that the negative half-cycle duty cycle D of the winding voltage Vab decreases due to the sum of the second control signal Sc2 and the third control signal Sc3, and then adjusts the change amount M by adjusting the phase shift amount Vs. Its operation method is roughly the same as the first control signal Sc1 and the fourth control signal Sc4, and will not be repeated here. Figure 4B Although only an illustrative example of controlling the first control signal Sc1 to lead the fourth control signal Sc4 by a phase shift amount Vs, or controlling the second control signal Sc2 to lead the third control signal Sc3 by a phase shift amount Vs is disclosed, the possibility of multiple implementations is not excluded. That is, the control can be performed by thinking in reverse and using a lagging phase. The principles are similar and will not be repeated here.

[0091] See also Figure 4C This is a circuit block diagram of a control module of the first embodiment of the resonant converter with frequency jitter function disclosed in the present invention, and is also referred to in conjunction with Figure 2A to Figure 4BThe control module 4 includes a comparator 42, a voltage controller 44, a pulse width modulator 46 and a duty cycle adjustment module 48. The comparator 42 compares the feedback signal Sfb corresponding to the output voltage Vo with the reference voltage Vref to provide an error signal Ser, and the voltage controller 44 generates a pulse width modulation value Vpwm and a change value Vm corresponding to the change amount M according to the error signal Ser. Among them, since the pulse width modulation value Vpwm is generated according to the error amount between the feedback signal Sfb and the reference voltage Vref, the output voltage Vo will change with the output current Io extracted by the load 300, so the pulse width modulation value Vpwm reflects the size of the output current Io. Therefore, the pulse width modulation value Vpwm and the change value Vm can be changed according to the size of the output current Io.

[0092] The pulse width modulator 46 modulates the first control signal Sc1, the second control signal Sc2, the third control signal Sc3 and the fourth control signal Sc4 according to the pulse width modulation value Vpwm, and the above control signals Sc1, Sc2, Sc3, Sc4 are pulse width modulation signals. The duty cycle adjustment module 48 adjusts the phase shift Vs of the control signals Sc1, Sc2, Sc3, Sc4 according to the change value Vm, so that the duty cycle D of the winding voltage Vab is adjusted by a change amount M so that the duty cycle D does not remain at the predetermined value Dp. Among them, the duty cycle adjustment module 48 can be, for example but not limited to, a phase adjustment circuit or the like for phase shifting (i.e. controlling leading / lagging) the control signals Sc1, Sc2, Sc3, Sc4, but is not limited thereto. It is worth mentioning that in one embodiment, a driving circuit 5 may be further included between the pulse width modulator 46 and the primary side circuit 2. The driving circuit 5 is a driving device that smoothly drives the high-power switch using a weak current signal. When the control signals Sc1, Sc2, Sc3, and Sc4 can smoothly drive the first bridge arm 22 and the second bridge arm 24 without the driving circuit 5, the driving circuit 5 may not be required. In addition, in one embodiment of the present invention, it is not limited that the components in the control module 4 must be implemented according to this architecture. All components, circuits, or software programs that can achieve the same function (for example, the comparison function is not limited to using only a comparator) (and the controller controls the resonant converter according to the program by writing a control software program) should be included in the scope of this embodiment.

[0093] See also Figure 5A The circuit block diagram of the second embodiment of the resonant converter with frequency jitter function disclosed in the present invention, Figure 5B This is a signal waveform diagram of the second embodiment of the resonant converter with frequency jitter function disclosed in the present invention, and is also referred to in conjunction with Figure 2A to Figure 4C .exist Figure 5AIn the embodiment, the resonant converter 100 is a half-bridge resonant converter, and the primary side circuit 2 further includes a first bridge arm 22. The first bridge arm 22 includes a first switch Q1 and a second switch Q2 connected in series, and the resonant module 122 is connected in parallel with the second switch Q2. The control module 4 provides a first control signal Sc1 to control the first switch Q1, and provides a second control signal Sc2 to control the second switch Q2. Therefore, Figure 5B As shown, through the control of the control module 4 , the primary side circuit 2 can convert the DC voltage Vdc and generate a winding voltage Vab between the first end a and the second end b of the resonance module 122 .

[0094] exist Figure 5B In the waveform diagram, the technical content of the signal waveform on the left half is similar to Figure 4B , which will not be elaborated here. In the signal waveform on the right half, since the first control signal Sc1 and the second control signal Sc2 cannot be phase-shifted, the dead time can be used to adjust the change amount M. Specifically, when the control module 4 detects that the output current Io is in the current interval Ci, the dead time DT between the first control signal Sc1 and the second control signal Sc2 is adjusted, so that the duty cycle D of the positive and negative half-cycles of the winding voltage Vab decreases due to the adjustment of the dead time DT, and then the change amount M is adjusted by adjusting the dead time DT. Among them, the first control signal Sc1 and the second control signal Sc2 are corresponding opposite signals, so controlling the first control signal Sc1 can make the second control signal Sc2 make corresponding adjustments.

[0095] See also Figure 5C This is a circuit block diagram of a control module of a second embodiment of a resonant converter with a frequency jitter function disclosed in the present invention, and is also referred to in conjunction with Figure 2A to Figure 5B . Figure 5C The control module 4 of the embodiment and Figure 4C The difference between the control module 4 and the control module 4 is that the pulse width modulator 46 modulates the first control signal Sc1 and the second control signal Sc2 according to the pulse width modulation value Vpwm, and the duty cycle adjustment module 48 adjusts the dead time DT of the control signals Sc1 and Sc2 according to the change value Vm. The duty cycle adjustment module 48 can be, for example but not limited to, a time delay circuit or other circuit for generating the dead time DT, but is not limited to this. It is worth mentioning that in one embodiment, Figure 5C Unspecified technical content, same as Figure 4C , which will not be described in detail here. On the other hand, in one embodiment, the resonant converter 100 is not Figure 4A , Figure 5A The LLC architecture is not limited to this invention, and any converter that can utilize resonance to perform DC conversion function should be included in the scope of the present disclosure.

[0096] See also Fig. 6AThis is a flowchart of the method of operating the first embodiment of the resonant converter with frequency jitter function disclosed in the present invention, and is also referred to in conjunction with Figure 2A to Figure 5C .At Fig. 6A The operation method in is mainly to cooperate with Figure 3A The control module 4 of the resonant converter 100 can pre-set parameters such as the predetermined current Io_stop, the predetermined value Dp, and the critical value Dl, and the operation method of the resonant converter 100 includes determining whether the output current is less than the predetermined current (S100). When the control module 4 determines that the output current Io is less than the predetermined current Io_stop (interval I), the control change amount is zero (S120). When the control module 4 determines that the output current Io is not less than the predetermined current Io_stop (interval I), it determines whether the output current is greater than the rated current (S200). When the control module 4 determines that the output current Io is greater than the rated current Io_max (interval III), the control change amount is zero (S220). Among them, the order of steps (S100) and (S200) can be reversed, and when the judgment results of steps (S100) and (S200) are both "no", it means that the output current Io is in the current interval Ci. Therefore, the change amount is calculated (S320). Finally, the phase shift amount of the control signal is adjusted to adjust the variation amount (S340).

[0097] Since the variation M in steps (S120) and (S220) is zero, step (S340) does not use the phase shift control signals Sc1, Sc2, Sc3, Sc4, so that the duty cycle D is fixed at the predetermined value Dp. In step (S320), since the variation M is not zero, in step (S340), the control module 4 adjusts the phase shift Vs of the control signals Sc1, Sc2, Sc3, Sc4 based on the calculated variation Vm (corresponding to the variation M), so that the duty cycle D of the winding voltage Vab varies within the range of the predetermined value Dp minus the variation M and the predetermined value Dp. In this way, the EMI values ​​of the resonant converter 100 from no load to full load can meet the specification values. It is worth mentioning that in one embodiment, the detailed operation method of the resonant converter 100 can be referred to in conjunction with Figure 2A to Figure 5C , I will not elaborate on it here.

[0098] See also Figure 6B This is a flowchart of the method of operating the second embodiment of the resonant converter with frequency jitter function disclosed in the present invention, and is also referred to in conjunction with Figure 2A to Figure 6A .At Figure 6B The operation method in is mainly to cooperate with Figure 3B The curve graph of Figure 6B How to operate and Fig. 6AThe difference in the operation method is that the dead time of the control signal is adjusted to adjust the variation (S360). In step (S320), since the variation M is not zero, in step (S360), the control module 4 adjusts the dead time DT of the control signals Sc1 and Sc2 based on the calculated variation Vm (corresponding to the variation M), so that the duty cycle D of the winding voltage Vab changes within the range of the predetermined value Dp minus the variation M and the predetermined value Dp. In this way, the EMI values ​​of the resonant converter 100 from no load to full load can meet the specification values. It is worth mentioning that in one embodiment, Figure 6B Steps not described are the same as Fig. 6A , and the detailed operation method of the resonant converter 100 can also be referred to in conjunction with Figure 2A to Figure 5C , I will not elaborate on it here.

[0099] However, the above description is only a detailed description and drawings of the preferred specific embodiments of the present invention, but the features of the present invention are not limited thereto and are not used to limit the present invention. The entire scope of the present invention shall be based on the following claims. All embodiments that conform to the spirit of the claims of the present invention and similar variations thereof shall be included in the scope of the present invention. Any changes or modifications that can be easily thought of by any person skilled in the art within the field of the present invention shall be covered by the following claims of this case.

Claims

1. A resonant converter, converting a DC voltage into an output voltage, the resonant converter comprising: A transformer, including a primary winding; A primary side circuit receives the DC voltage and comprises a resonant circuit, wherein the resonant circuit is coupled to the primary side winding to form a resonant module; and A control module coupled to the primary side circuit and controlling the primary side circuit to convert the DC voltage to generate a winding voltage at two ends of the resonance module; When the control module detects that the output current of the resonant converter is between a predetermined current and a rated current, the control module adjusts the duty cycle of the winding voltage to have a variation. 2 . The resonant converter according to claim 1 , wherein when the control module detects that the output current is less than the predetermined current or greater than the rated current, the control module fixes the duty cycle to a predetermined value.

3. The resonant converter according to claim 1 , wherein when the control module detects that the output current is in the current interval, the control module controls the operating frequency of the resonant converter to change within a frequency range, and the frequency range is positively correlated to the change amount. 4 . The resonant converter according to claim 3 , wherein the control module sets the threshold value of the variation amount as a fixed value, and the frequency range is a specific range corresponding to the threshold value. 5 . The resonant converter according to claim 3 , wherein the control module sets the threshold value of the variation amount to increase as the output current increases, and the frequency range is expanded according to the increase of the threshold value.

6. The resonant converter according to claim 1, wherein the resonant converter is a full-bridge resonant converter, and the primary side circuit further comprises: The first bridge arm comprises a first switch and a second switch connected in series, and the first end of the resonance module is coupled between the first switch and the second switch; and A second bridge arm is connected in parallel with the first bridge arm and includes a third switch and a fourth switch connected in series, and the second end of the resonance module is coupled between the third switch and the fourth switch; The control module provides a first control signal to control the first switch, provides a second control signal to control the second switch, provides a third control signal to control the third switch, and provides a fourth control signal to control the fourth switch; and When the control module detects that the output current is in the current interval, the control module controls the first control signal and the fourth control signal to have a phase shift amount of phase change to adjust the change amount; or When the control module detects that the output current is in the current interval, the control module controls the second control signal and the third control signal to have the phase shift amount of the phase change to adjust the change amount. 7 . The resonant converter according to claim 6 , wherein when the control module detects that the output current is not in the current interval, the second control signal and the first control signal are complementary signals, and the third control signal and the fourth control signal are complementary signals.

8. The resonant converter according to claim 6, wherein the control module comprises: a comparator, comparing a feedback signal corresponding to the output voltage with a reference voltage to provide an error signal; A voltage controller generates a pulse width modulation value and a change value corresponding to the change amount according to the error signal; a pulse width modulator, modulating the first control signal, the second control signal, the third control signal and the fourth control signal according to the pulse width modulation value; and A duty cycle adjustment module adjusts the phase shift amount according to the change value.

9. The resonant converter according to claim 1, wherein the resonant converter is a half-bridge resonant converter, and the primary side circuit further comprises: The first bridge arm comprises a first switch and a second switch connected in series, and the resonance module is connected in parallel with the second switch; The control module provides a first control signal to control the first switch, and provides a second control signal to control the second switch; when the control module detects that the output current is in the current range, the control module adjusts the dead time between the first control signal and the second control signal to adjust the change amount. 10 . The resonant converter according to claim 9 , wherein when the control module detects that the output current is not in the current interval, the second control signal and the first control signal are complementary signals.

11. The resonant converter of claim 9, wherein the control module comprises: a comparator, comparing a feedback signal corresponding to the output voltage with a reference voltage to provide an error signal; A voltage controller generates a pulse width modulation value and a change value corresponding to the change amount according to the error signal; a pulse width modulator, modulating the first control signal and the second control signal according to the pulse width modulation value; A duty cycle adjustment module adjusts the dead time according to the change value.

12. An operating method of a resonant converter, the resonant converter comprising a transformer and a primary side circuit, wherein the primary side circuit comprises a resonant circuit, the resonant circuit is coupled to a primary side winding of the transformer to form a resonant module, and the operating method comprises the following steps: Controlling the primary side circuit to convert the DC voltage, so as to control the resonant converter to convert the DC voltage into an output voltage and generate a winding voltage at two ends of the resonant module; detecting an output current of the resonant converter, and when determining that the output current is between a predetermined current and a rated current, adjusting the duty cycle of the winding voltage to have a variation; and The operating frequency of the resonant converter is controlled to change within a frequency range by adjusting the duty cycle, and the frequency range is positively correlated to the change amount.

13. The operating method according to claim 12, further comprising the following steps: When the output current is less than the predetermined current or greater than the rated current, the duty cycle is fixed to a predetermined value.

14. The operating method according to claim 12, further comprising the following steps: The critical value of the variation is set to be a fixed value, and the frequency range is in a specific range corresponding to the critical value.

15. The operating method according to claim 12, further comprising the following steps: The critical value of the variation is set to increase with the increase of the output current, and the frequency range is expanded according to the increase of the critical value.

16. The operating method according to claim 12, wherein the primary side circuit comprises a first bridge arm and a second bridge arm connected in parallel, the first bridge arm comprises a first switch and a second switch, and the second bridge arm comprises a third switch and a fourth switch, and the operating method further comprises the following steps: providing a first control signal to control the first switch, providing a second control signal to control the second switch, providing a third control signal to control the third switch, and providing a fourth control signal to control the fourth switch; When the output current is in the current interval, controlling the first control signal and the fourth control signal to have a phase shift amount of phase change to adjust the change amount; or When the output current is in the current interval, the second control signal and the third control signal are controlled to have the phase shift amount of the phase change to adjust the change amount.

17. The operating method according to claim 16, further comprising the following steps: comparing a feedback signal corresponding to the output voltage with a reference voltage to provide an error signal; generating a pulse width modulation value and a change value corresponding to the change amount according to the error signal; modulate the first control signal, the second control signal, the third control signal and the fourth control signal according to the PWM value; and The phase shift amount is adjusted according to the change value.

18. The operating method according to claim 12, wherein the primary side circuit comprises a first bridge arm, and the first bridge arm comprises a first switch and a second switch, and the operating method further comprises the following steps: providing a first control signal to control the first switch, and providing a second control signal to control the second switch; and When the output current is in the current interval, the dead time between the first control signal and the second control signal is adjusted to adjust the variation.

19. The operating method according to claim 18, further comprising the following steps: comparing a feedback signal corresponding to the output voltage with a reference voltage to provide an error signal; generating a pulse width modulation value and a change value corresponding to the change amount according to the error signal; modulate the first control signal and the second control signal according to the PWM value; and The dead time is adjusted according to the change value.

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