Method of power converter, converter circuit and pulse width modulation controller

Abstract

A method for a DC-DC power converter is disclosed, comprising: providing a DC-DC power converter having a switching node and an output sensing node, the switching node is configured to be coupled to a first end of an inductor element, the inductor element is externally connected to the DC-DC power converter, the output sensing node is configured to be coupled to a second end of the inductor element, an output voltage provided by the DC-DC power converter is generated at the second end of the inductor element through the inductor element; and in response to a specific event when a fluctuation range of a current flowing through the inductor element reaches or exceeds a specific range, adjusting a switching frequency adopted by the DC-DC power converter, wherein the DC-DC power converter detects the specific event through the switching node and the output sensing node. The method can resist electromagnetic coupling effect and can reduce or avoid voltage drop in an output voltage level generated from the power converter due to occurrence of unexpected electromagnetic coupling.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a mechanism of a direct current-direct current (DC / DC) power converter, in particular to a method of the DC / DC power converter, a converter circuit and a pulse width modulation controller in the converter circuit. BACKGROUND

[0002] Generally speaking, in the trend of making true wireless stereo (TWS) devices, such as earphones, earbuds or headphones, smaller and smaller, for example, in the trend of providing miniaturized TWS devices, due to the size of the miniaturized or micro-sized devices, an unexpected or unwanted electromagnetic field (or coupling) effect will frequently occur because the distance between the inductor and the magnet of a conventional power converter becomes extremely short, which inevitably leads to a large and rapid change in the inductance value of the inductor, and due to the excessively long circuit response time of the conventional power converter, the output voltage provided by the conventional power converter will also be greatly reduced, resulting in a significant reduction in the average current that the power converter can provide. SUMMARY

[0003] Therefore, one of the purposes of the present disclosure is to disclose a method of a direct current-direct current (DC / DC) power converter, a converter circuit and a pulse width modulation controller in the converter circuit to solve the above-mentioned problems.

[0004] According to an embodiment of the present disclosure, a method of a direct current-direct current (DC / DC) power converter is disclosed. The method comprises: providing the DC / DC power converter having a switching node and an output sensing node, the switching node being used to be coupled to a first end of an inductor element, the inductor element being externally connected to the DC / DC power converter, the output sensing node being used to be coupled to a second end of the inductor element, an output voltage provided by the DC / DC power converter being generated at the second end of the inductor element through the inductor element; and in response to a specific event when a fluctuation range of a current flowing through the inductor element reaches or exceeds a specific range, adjusting a switching frequency adopted by the DC / DC power converter, wherein the DC / DC power converter detects the specific event through the switching node and the output sensing node.

[0005] According to an embodiment of the present application, a converter circuit of a DC-DC power converter is disclosed. The converter circuit includes a switch node, an output sense node, and a pulse width modulation controller. The switch node is configured to be coupled to a first end of an inductor element, which is externally connected to the DC-DC power converter. The output sense node is configured to be coupled to a second end of the inductor element, wherein an output voltage provided by the DC-DC power converter is generated at the second end of the inductor element through the inductor element. The pulse width modulation controller is coupled to the switch node and the output sense node, and is configured to adjust a switching frequency adopted by the DC-DC power converter in response to a specific event when a fluctuation range of a current flowing through the inductor element reaches or exceeds a specific range, wherein the specific event is detected by the DC-DC power converter through the switch node and the output sense node.

[0006] According to an embodiment of the present application, a pulse width modulation controller in a converter circuit of a DC-DC power converter is disclosed. The converter circuit includes a switch node and an output sense node. The switch node is configured to be coupled to a first end of an inductor element, which is externally connected to the DC-DC power converter. The output sense node is configured to be coupled to a second end of the inductor element, wherein an output voltage provided by the DC-DC power converter is generated at the second end of the inductor element through the inductor element. The pulse width modulation controller is coupled to the switch node and the output sense node, and is configured to adjust a switching frequency adopted by the DC-DC power converter in response to a specific event when a fluctuation range of a current flowing through the inductor element reaches or exceeds a specific range, wherein the specific event is detected by the DC-DC power converter through the switch node and the output sense node.

[0007] The method, the converter circuit, and the pulse width modulation controller provided by the embodiments of the present application can resist electromagnetic coupling effect, and can reduce or avoid voltage drop in an output voltage level generated from a power converter due to occurrence of unpredictable electromagnetic coupling. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 FIG. 1 is a block diagram of a DC-DC power converter according to an embodiment of the present application.

[0009] Figure 2 FIG. 3 is a normal signal waveform diagram of an inductor current I L (t) through the inductor element when the power converter operates in a discontinuous conduction mode according to an embodiment of the present application.

[0010] Figure 3is the inductive current I(t) of an embodiment of the present invention when the power converter is operating in an overload condition L is a signal waveform schematic of the inductive current I(t).

[0011] Figure 4 is the inductive current I(t) of an embodiment of the present invention when the power converter is operating in an overload condition L is a signal waveform schematic of the inductive current I(t).

[0012] Figure 5 is a signal waveform schematic of the inductive current I(t) when the inductance value of the inductive element is increased due to an unexpected event of electromagnetic coupling.

[0013] Figure 6 is a signal waveform schematic of the inductive current I(t) when the inductance value of the inductive element is decreased due to an unexpected event of electromagnetic coupling.

[0014] Figure 7 is a schematic of the performance ratio of the operation of the pulse width modulation controller with the ability to mitigate the unexpected event of electromagnetic coupling and without the ability.

[0015] Figure 8 is a schematic of the performance of the pulse width modulation controller with the ability to mitigate the unexpected event of electromagnetic coupling of an embodiment of the present invention.

[0016] Wherein, the reference numerals are explained as follows:

[0017] 100 DC-DC power converter

[0018] 101 inductive component

[0019] 102 capacitive component

[0020] 103 converter circuit

[0021] 105 switching circuit

[0022] 110 pulse width modulation controller

[0023] 1101 operational amplifier

[0024] 1102 duty cycle control circuit DETAILED DESCRIPTION

[0025] The present invention aims to disclose a power recovery method / mechanism capable of resisting the effect of electromagnetic coupling, which is based on extremely short circuit response time and is capable of mitigating or avoiding a voltage drop in an output voltage level generated from a power converter due to an unexpected event of electromagnetic coupling.

[0026] Figure 1is a block diagram of a direct-current-to-direct-current (DC / DC) power converter 100 according to an embodiment of the present application. The power converter 100 is, for example, a buck converter, but is not limited thereto. The power converter 100 is coupled to a supply voltage signal VDD to step down an input voltage level, such as the supply voltage signal VDD, to an output voltage Vout as shown in Figure 1 The power converter 100 includes an inductor element 101, a capacitor element 102, and a converter circuit 103, wherein the inductor element 101, the capacitor element 102, and the converter circuit 103 can be implemented and disposed on the same printed circuit board or can be disposed on different printed circuit boards, which is not a limitation of the present application. The converter circuit 103 includes a switch node LX, an output sense node SNS, a switch circuit 105, and a pulse-width modulation (PWM) controller 110. The converter circuit 103 is externally coupled to the inductor element 101 through the switch node LX. The switch node LX is coupled to a first end of the inductor element 101. The inductor element 101 is coupled between the switch node LX and a first end of the capacitor element 102, wherein a second end of the capacitor element 102 is coupled to the ground level. The first end of the capacitor element 102 is connected to a second end of the inductor element 101 and is also connected to the output sense node SNS of the converter circuit 103 of the power converter 100, and the output sense node SNS is used to be coupled to the second end of the inductor element 101 as shown in Figure 1 The output voltage Vout provided by the DC / DC power converter 100 is generated at the first end of the capacitor element 102 (or at the second end of the inductor element 101), and the capacitor element 102 and the inductor element 101 can be regarded as a load capacitor and a load inductor, respectively.

[0027] In practice, the switching circuit 105 includes a first transistor Q1 (e.g., a P-type MOSFET) and a second transistor Q2 (e.g., an N-type MOSFET). The first transistor Q1 is coupled between the supply voltage signal VDD and the switching node LX, while the second transistor Q2 is coupled between the ground level and the switching node LX. However, it should be noted that the above circuit design of the switching circuit 105 is not a limitation of the present invention. The pulse width modulation controller 110 is coupled to the switching node LX and also to the output sensing node SNS via the switching circuit 105, and is used, for example, to control the ON / OFF state or conduction state of the transistors Q1 and Q2. For example, the pulse width modulation controller 110 includes an operational amplifier 1101 and a duty cycle control circuit 1102. The operational amplifier 1101 is used as an error amplifier to receive and compare a reference voltage level Vref with the voltage Vsns sensed at the output sensing node SNS to generate a control signal SC to the duty cycle control circuit 1102. The duty cycle control circuit 1102 is used to control and adjust the duty cycle of a pulse width modulation control signal used to control the transistors Q1 and Q2 according to a plurality of control signals SC1 and SC2; however, this is not a limitation of the present invention.

[0028] Figure 2 In one embodiment of the present invention, when the power converter 100 operates in a discontinuous conduction mode (DCM), the inductor current I through the inductor element 101 is... L A schematic diagram of the normal signal waveform of (t). The inductor current I... L The increase and decrease of (t) can be represented by the following equation:

[0029]

[0030]

[0031] like Figure 1 As shown, during the time period between time t1 and time t2, in the DCM mode of the power converter 100, the pulse width modulation controller 110, for example, turns on transistor Q1 but not transistor Q2, therefore the inductor current I... L (t) will flow from the supply voltage VDD through the inductor 101 to the first terminal of the capacitor 102. In this case, the pulse width modulation controller 110 will detect the output sense voltage Vsns to control the conduction level of the transistor Q1, so that the inductor current I LThe current I1(t) represented by (t) will be based on a first slope The current I1(t) increases over time and stops increasing only when the output sensing voltage Vsns reaches the supply voltage VDD, at which point it reaches its maximum value. Then, during the time interval between time t2 and time t3, the pulse width modulation controller 110 turns off transistor Q1 and turns on transistor Q2, thus increasing the inductor current I. L (t) flows from the first terminal of the capacitor element 102 through the inductor element 101 to the ground level. In this case, the pulse width modulation controller 110 detects the output sense voltage Vsns to control the conduction level of the transistor Q2, so that the inductor current I... L The current I2(t) represented by (t) will be based on a second slope It decreases over time and stops increasing only when the output sensing voltage Vsns reaches the ground level, at which point the current I1(t) reaches zero, i.e., it exhibits a zero-crossing phenomenon.

[0032] If the power converter 100 is under light load conditions, it can operate in DCM mode. If it is under heavy load or overload conditions, the power converter 100 will operate in continuous conduction mode (CCM). Figure 3 and Figure 4 These are embodiments of the present invention, specifically the induced current I under heavy load and overload conditions when the power converter 100 operates. L A schematic diagram of the signal waveform (t). For example... Figure 3 As shown, when the power converter 100 is under heavy load, the power converter 100 will operate in CCM mode, and the induced current I L (t) then as Figure 3 As shown, the induced current I L The minimum value of (t) will not reach zero, meaning there is no zero-point crossing. Iavg_heavy represents the induced current I when the power converter 100 is under heavy load. L The average value of (t). Furthermore, such as Figure 4 As shown, when the power converter 100 is under overload conditions, the power converter 100 will also operate in CCM mode, and the induced current I L (t) then as Figure 4 As shown, the induced current I L The minimum value of (t) will not reach zero, that is, there is no zero-point crossing phenomenon, and the induced current I LThe maximum value of (t) may reach a maximum acceptable current level specified by an overcurrent protection operation, i.e., the overcurrent protection level. Iavg_over represents the induced current I when the power converter 100 is under overload conditions. L The average value of (t).

[0033] Please refer to this again. Figure 1 If an unforeseen electromagnetic coupling event occurs, the inductance value of the inductor 101 will increase or decrease due to this event. Based on the above equations, an increase in the inductance value of the inductor 101 will cause... absolute value and The absolute value of I1(t) becomes smaller, which means that the induced current I1(t) will increase slowly with a gentler slope, and the induced current I2(t) will decrease slowly with another gentler slope; conversely, if the inductance value of the inductor 101 decreases, it will cause... absolute value and The absolute value of I1(t) becomes larger, indicating that the induced current I1(t) will increase rapidly with a steeper slope, while the induced current I2(t) will decrease rapidly with another steeper slope. When the inductance value increases, the duty cycle can be set after multiple cycles, and when the inductance value decreases, the overcurrent protection operation may be triggered to reduce the capacitance of capacitor element 102.

[0034] Figure 5 as well as Figure 6 These are schematic diagrams illustrating signal waveforms when the inductance value of the inductor 101 increases or decreases due to unforeseen electromagnetic coupling events. For example... Figure 5 As shown, when the inductor 101 increases due to the unforeseen electromagnetic coupling, the induced current I will increase regardless of whether the power converter 100 is operating in DCM mode or CCM mode. L The slope of the current change in (t) becomes flatter. For example, I avg This indicates the induced current I when the power converter 100 operates in the DCM mode. L (t) is an average value over a slowly changing period. avg_heavy This indicates the induced current I when the power converter 100 operates in the CCM mode. L (t) is also a slowly changing average value. Furthermore, as... Figure 6 As shown, when the inductance of the inductor 101 decreases due to unforeseen electromagnetic coupling, the induced current I... LThe slope of the current variation of (t) becomes steeper, the over-current protection operation is triggered, and the inductive current I L (t) reaches the maximum acceptable current level (i.e. an over-current protection level) of the over-current protection operation more quickly and / or the inductive current I L (t) decreases more quickly, the phenomenon of zero-crossing occurs immediately. In Figure 6 , since the inductive current I L (t) reaches the over-current protection level more quickly and then reaches zero quickly, the average value I L (t) of the inductive current I avg decreases or reduces, and in addition, the output voltage Vout can also experience a large voltage drop due to the unexpected electromagnetic coupling.

[0035] In embodiments of the present application, in order to avoid or mitigate the voltage drop due to the unexpected electromagnetic coupling and / or to maximize (or increase) the average current (which decreases due to the unexpected electromagnetic coupling), the pulse width modulation controller 110 of the power converter 100 is configured to dynamically adjust a switching frequency (i.e. clock frequency) in response to a certain event, wherein the certain event refers to a fluctuation range of the current (i.e. the inductive current I L (t)) flowing through the inductive element 101 reaching or exceeding a certain range. That is, the switching frequency (or clock frequency) is adjusted in response to the change of the inductance value of the inductive element 101 caused by the change of the external electromagnetic field. In addition, the certain event can be detected by the pulse width modulation controller 110 through the switching node LX and the output sense node SNS. For example, the pulse width modulation controller 110 can detect the fluctuation range of the inductive current I L (t) by detecting the voltage or current values on the switching node LX and the output sense node SNS to detect or determine whether the over-current protection operation is triggered (or initiated) and / or whether the phenomenon of zero-crossing occurs, so that the pulse width modulation controller 110 is able to detect or determine whether the inductance value of the inductive element 101 is changed due to the occurrence of the unexpected electromagnetic coupling.

[0036] For example, when a peak-to-peak value of the fluctuation of the inductive current I L (t) is greater than a certain threshold value, the pulse width modulation controller 110 can determine that the fluctuation range of the inductive current I L (t) reaches or exceeds the certain range. The certain range refers to a certain range of current levels, which can be represented by a first value (e.g. I high ) and a second value (e.g. Ilow ) defined specification, wherein the first value I high For example, can be determined by either a maximum acceptable current level (i.e. overcurrent protection level) of the overcurrent protection operation or a tolerable upper current limit lower than the overcurrent protection level. And the second value I low For example, can be determined by either zero or a tolerable lower current limit higher than zero. That is, even when the induced current I L (t) increases rapidly but has not yet reached the overcurrent protection level or when the induced current I L (t) decreases rapidly but has not yet reached the level of zero, the pulse width modulation controller 110 can adjust the switching frequency (i.e. clock frequency) early.

[0037] In practice, the pulse width modulation controller 110 can be used to adjust the switching frequency when both a first event and a second event occur during the same operating period of the DC-DC power converter 100 (or when they occur during different operating periods, respectively), wherein the first event refers to the induced current I L (t) reaching the first value I high , and the second event refers to the induced current I L (t) reaching the second value I low .

[0038] Figure 7 is the pulse width modulation controller 110 has the ability to mitigate the effects of the unpredictable electromagnetic coupling and the performance ratio example of the operation without the ability. For example, as shown in the left half of Figure 7 , if the pulse width modulation controller 110 does not have the effect of mitigating the unpredictable electromagnetic coupling, the current value of the induced current I L (t) will increase rapidly and reach the overcurrent protection level (i.e. maximum acceptable current level) at time t1 due to the triggering of the overcurrent protection, and then the current value of the induced current I L (t) decreases rapidly and reaches zero (i.e. zero-crossing phenomenon occurs) at time t2. Then, at the second time, similarly, the current value of the induced current I L (t) will increase rapidly and reach the overcurrent protection level (i.e. maximum acceptable current level) at time t7 due to the triggering of the overcurrent protection, and then the current value of the induced current I L (t) decreases rapidly and reaches zero (i.e. zero-crossing phenomenon occurs) at time t8. In this way, the average current value I L (t) of the induced current I avg will be greatly reduced due to the effects of unpredictable electromagnetic coupling.

[0039] Conversely, such as Figure 7 As shown in the right half, the pulse width modulation controller 110 is used to mitigate the effects of this unintended electromagnetic coupling. In this example, the first value I... high This is the overcurrent protection level, and the second value I low It is at the zero-point level, however, this is not a limitation of the invention. The pulse width modulation controller 110 can detect the occurrence of the first event (i.e., the occurrence of induced current I) by detecting that the overcurrent protection operation is triggered at time t1. L The current value of (t) increases rapidly and reaches the first value I. high (That is, the overcurrent protection level or the maximum acceptable current level), and then the occurrence of the second direct current (that is, the occurrence of induced current I) can be detected by detecting the phenomenon of zero-point crossing at time t2. L The current value of (t) decreases rapidly and reaches the second value I. low (i.e., zero point) , where time t1 and time t2 can occur within the same working cycle, that is, within the same cycle of a pulse width modulation control signal, or within different working cycles, that is, within different cycles of different pulse width modulation control signals; this is not a limitation of the present invention. In these embodiments, when the first event and the second event are detected, the pulse width modulation controller 110 immediately increases the clock frequency of the pulse width modulation control signal generated by the pulse width modulation controller 110. Therefore, by increasing the clock frequency, the induced current I can be generated more frequently. L (t). For example, during the time period from time t1 to time t7, this induced current I can be generated. L (t) twice (but not limited to), and the induced current I L The current value of (t) may reach the overcurrent protection level at times t3 and t5, and may reach zero at times t4 and t6. Therefore, the induced current I can be significantly increased, enhanced, or maximized. L The average current I of (t) avg .

[0040] Furthermore, in other embodiments, the pulse width modulation controller 110 may also determine to increase the clock frequency when at least one of the first event and the second event occurs. For example, if either the first event or the second event is detected, the pulse width modulation controller 110 may determine that the inductance value of the inductor 101 has changed due to an unexpected electromagnetic coupling event, and then decide to increase the clock frequency to mitigate the effect of the unexpected electromagnetic coupling. If neither the first event nor the second event is detected, the pulse width modulation controller 110 will maintain the clock frequency at its original value. Furthermore, when the first event and / or the second event is detected, the pulse width modulation controller 110 may gradually, continuously, or stepwise increase the clock frequency. Additionally, the pulse width modulation controller 110 may increase and maintain the clock frequency for a specific time period, and then determine whether to adjust the clock frequency again. Furthermore, the pulse width modulation controller 110 can also increase or decrease the switching frequency (i.e., the clock frequency) within a predetermined time period or within a variable time period, wherein the variable time period ends when the induced current I is detected. L When the fluctuation range of (t) becomes smaller than a specific range of the current level. In addition, the pulse width modulation controller 110 can also adjust the switching frequency from an increased frequency back to an original frequency at the end of the predetermined time period or the variable time period.

[0041] Figure 8 This is a schematic diagram illustrating an example of the performance of a pulse width modulation controller 110 according to an embodiment of the present invention, which has the ability to mitigate unpredictable electromagnetic coupling effects. For example... Figure 8 As shown in the upper part, Vout1 refers to the output voltage generated by the DC-DC power converter 100 if it decides not to mitigate the unintended electromagnetic coupling effect. Before time tA, the output voltage Vout1 can be maintained at a default voltage level. At time tA, the unintended electromagnetic coupling effect occurs, resulting in a significant voltage drop across the output voltage Vout1, for example, 50 millivolts (but not limited to). If the load capacitance is, for example, equal to 10 microfarads (μF), the circuit response time of the power converter 100 will be a relatively long time period, for example, 10 microseconds (μs). However, these data are not limitations of the invention. When the DC-DC power converter 100 employs operation to mitigate the unintended electromagnetic coupling effect, such as... Figure 8As shown in the lower half of FIG. 1, Vout2 refers to the output voltage generated by the DC-DC power converter 100 with the operation to mitigate the unexpected electromagnetic coupling effect. Similarly, the output voltage Vout2 can also be maintained at the default voltage level before time tA. At time tA, when the unexpected electromagnetic coupling effect occurs, only a small voltage drop, for example, 2.5 millivolts (but not limited), occurs on the output voltage Vout2. With the load capacitance value still equal to 10 microfarad (μF), for example, the circuit response time of the power converter 100 can be significantly reduced to a short time period, for example, 0.5 microsecond, which is less than half of the period of the pulse width modulation control signal. Therefore, from Figure 8 It can be known that the pulse width modulation controller 110 with the operation and capability to mitigate the unexpected electromagnetic coupling effect can significantly reduce or decrease the circuit response time and significantly reduce or avoid a large voltage drop on the output circuit, so that sufficient power can be provided to an electronic device even when the unwanted and unexpected electromagnetic coupling effect occurs.

[0042] The preferred embodiments of the present application have been described above with the aid of drawing only for the purpose of illustration, and the present application can be modified in various ways. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall fall within the scope of the present application.

Claims

1. A method of a direct-current-direct-current power converter, characterized by, comprising: providing the dc-dc power converter with a switch node for coupling to a first end of an inductor element externally connected to the dc-dc power converter and an output sense node for coupling to a second end of the inductor element through which an output voltage provided by the dc-dc power converter is generated; and adjusting a switching frequency employed by the dc-dc power converter in response to a particular event when a fluctuation range of a current flowing through the inductor element reaches or exceeds a particular range, wherein the particular event is detected by the dc-dc power converter through the switch node and the output sense node; wherein the step of adjusting the switching frequency employed by the dc-dc power converter comprises: increasing the switching frequency during a predetermined time period or during a variable time period, wherein the variable time period ends when the fluctuation range of the current flowing through the inductor element becomes less than the particular range.

2. The method of claim 1, wherein, further comprising: determining that the fluctuation range of the current flowing through the inductor element reaches or exceeds the particular range when a peak-to-peak value of the fluctuation of the current is greater than a particular threshold.

3. The method of claim 1, wherein, the particular range is defined by a first value determined by either one of a maximum current level of an over-current protection operation and a tolerable upper current limit lower than the maximum current level and a second value determined by either one of zero and a tolerable lower current limit higher than zero.

4. The method of claim 3, wherein, adjusting the switching frequency when both a first event indicating that the current flowing through the inductor element reaches the first value and a second event indicating that the current flowing through the inductor element reaches the second value occur during a same operating cycle of the dc-dc power converter.

5. The method of claim 3, wherein, adjusting the switching frequency when a first event indicating that the current flowing through the inductor element reaches the first value and a second event indicating that the current flowing through the inductor element reaches the second value occur during different operating cycles of the dc-dc power converter, respectively.

6. The method of claim 1, wherein, adjusting the switching frequency back to an original frequency when the predetermined time period or the variable time period ends.

7. The method of claim 1, wherein, the switching frequency is adjusted in response to a change in an inductance value of the inductor element caused by a change in an external electromagnetic field.

8. A converter circuit of a DC-DC power converter, characterized by comprising: a switch node for coupling to a first end of an inductor element externally connected to the dc-dc power converter; an output sense node for coupling to a second end of the inductor element through which an output voltage provided by the dc-dc power converter is generated; and a pulse width modulation controller coupled to the switch node and the output sense node for adjusting a switching frequency of the DC-DC power converter in response to a particular event when a fluctuation range of a current flowing through the inductive element reaches or exceeds a particular range, wherein the DC-DC power converter detects the particular event through the switch node and the output sense node; wherein the pulse width modulation controller increases the switching frequency during a predetermined time period or during a variable time period, the variable time period ending when the fluctuation range of the current flowing through the inductive element becomes less than the particular range.

9. The converter circuit of claim 8, wherein, The pulse width modulation controller determines that the fluctuation range of the current flowing through the inductive element reaches or exceeds the particular range when a peak-to-peak value of the fluctuation of the current is detected to be greater than a particular threshold.

10. The converter circuit of claim 8, wherein, The particular range is defined by a first value and a second value lower than the first value, the first value being determined by either one of a maximum current level of an over-current protection operation and a tolerable upper current limit lower than the maximum current level, and the second value being determined by either one of zero and a tolerable lower current limit higher than zero.

11. The converter circuit of claim 10, wherein, The pulse width modulation controller adjusts the switching frequency when both a first event and a second event occur during a same operating cycle of the DC-DC power converter; the first event indicating that the current flowing through the inductive element reaches the first value, and the second event indicating that the current flowing through the inductive element reaches the second value.

12. The converter circuit of claim 10, wherein, The pulse width modulation controller adjusts the switching frequency when a first event and a second event occur during different operating cycles of the DC-DC power converter; the first event indicating that the current flowing through the inductive element reaches the first value, and the second event indicating that the current flowing through the inductive element reaches the second value.

13. The converter circuit of claim 8, wherein, The pulse width modulation controller adjusts the switching frequency back to an original frequency when the predetermined time period or the variable time period ends.

14. The converter circuit of claim 8, wherein, The switching frequency is adjusted in response to a change in an inductance of the inductive element caused by a change in an external electromagnetic field.

15. A pulse width modulation controller in a converter circuit of a DC-DC power converter, characterized by The converter circuit includes a switch node for coupling to a first end of an inductor element externally connected to the DC-DC power converter and an output sense node for coupling to a second end of the inductor element through which an output voltage provided by the DC-DC power converter is generated; the pulse width modulation controller is coupled to the switch node and the output sense node and is adapted to adjust a switching frequency employed by the DC-DC power converter in response to a particular event when a fluctuation range of a current flowing through the inductor element reaches or exceeds a particular range, wherein the particular event is detected by the DC-DC power converter through the switch node and the output sense node; the pulse width modulation controller increases the switching frequency during a predetermined time period or a variable time period, which ends when the fluctuation range of the current flowing through the inductor element becomes less than the particular range.

16. The pulse width modulated controller of claim 15 wherein, The pulse width modulation controller determines that the fluctuation range of the current flowing through the inductor element reaches or exceeds the particular range when a peak-to-peak value of the fluctuation of the current is detected to be greater than a particular threshold.

17. The pulse width modulated controller of claim 15 wherein, The particular range is defined by a first value determined by either one of a maximum current level of an over-current protection operation and a tolerable upper current limit lower than the maximum current level and a second value determined by either one of zero and a tolerable lower current limit higher than zero.

18. The pulse width modulated controller of claim 15 wherein, The switching frequency is adjusted in response to a change in an inductance of the inductor element caused by a change in an external electromagnetic field.

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